loader: remove devdesc comments and assertions

[unleashed.git] / kernel / os / sunmdi.c

/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */
/*
 * Copyright (c) 2000, 2010, Oracle and/or its affiliates. All rights reserved.
 * Copyright (c) 2014 Nexenta Systems Inc. All rights reserved.
 */

/*
 * Multipath driver interface (MDI) implementation; see mdi_impldefs.h for a
 * more detailed discussion of the overall mpxio architecture.
 *
 * Default locking order:
 *
 * _NOTE(LOCK_ORDER(mdi_mutex, mdi_vhci:vh_phci_mutex);
 * _NOTE(LOCK_ORDER(mdi_mutex, mdi_vhci:vh_client_mutex);
 * _NOTE(LOCK_ORDER(mdi_vhci:vh_phci_mutex, mdi_phci::ph_mutex);
 * _NOTE(LOCK_ORDER(mdi_vhci:vh_client_mutex, mdi_client::ct_mutex);
 * _NOTE(LOCK_ORDER(mdi_phci::ph_mutex mdi_pathinfo::pi_mutex))
 * _NOTE(LOCK_ORDER(mdi_phci::ph_mutex mdi_client::ct_mutex))
 * _NOTE(LOCK_ORDER(mdi_client::ct_mutex mdi_pathinfo::pi_mutex))
 */

#include <sys/note.h>
#include <sys/types.h>
#include <sys/varargs.h>
#include <sys/param.h>
#include <sys/errno.h>
#include <sys/uio.h>
#include <sys/buf.h>
#include <sys/modctl.h>
#include <sys/open.h>
#include <sys/kmem.h>
#include <sys/poll.h>
#include <sys/conf.h>
#include <sys/bootconf.h>
#include <sys/cmn_err.h>
#include <sys/stat.h>
#include <sys/ddi.h>
#include <sys/sunddi.h>
#include <sys/ddipropdefs.h>
#include <sys/sunndi.h>
#include <sys/ndi_impldefs.h>
#include <sys/promif.h>
#include <sys/sunmdi.h>
#include <sys/mdi_impldefs.h>
#include <sys/taskq.h>
#include <sys/epm.h>
#include <sys/sunpm.h>
#include <sys/modhash.h>
#include <sys/disp.h>
#include <sys/autoconf.h>
#include <sys/sysmacros.h>

#ifdef  DEBUG
#include <sys/debug.h>
int     mdi_debug = 1;
int     mdi_debug_logonly = 0;
#define MDI_DEBUG(dbglevel, pargs) if (mdi_debug >= (dbglevel)) i_mdi_log pargs
#define MDI_WARN        CE_WARN, __func__
#define MDI_NOTE        CE_NOTE, __func__
#define MDI_CONT        CE_CONT, __func__
static void i_mdi_log(int, const char *, dev_info_t *, const char *, ...);
#else   /* !DEBUG */
#define MDI_DEBUG(dbglevel, pargs)
#endif  /* DEBUG */
int     mdi_debug_consoleonly = 0;
int     mdi_delay = 3;

extern pri_t    minclsyspri;
extern int      modrootloaded;

/*
 * Global mutex:
 * Protects vHCI list and structure members.
 */
kmutex_t        mdi_mutex;

/*
 * Registered vHCI class driver lists
 */
int             mdi_vhci_count;
mdi_vhci_t      *mdi_vhci_head;
mdi_vhci_t      *mdi_vhci_tail;

/*
 * Client Hash Table size
 */
static int      mdi_client_table_size = CLIENT_HASH_TABLE_SIZE;

/*
 * taskq interface definitions
 */
#define MDI_TASKQ_N_THREADS     8
#define MDI_TASKQ_PRI           minclsyspri
#define MDI_TASKQ_MINALLOC      (4*mdi_taskq_n_threads)
#define MDI_TASKQ_MAXALLOC      (500*mdi_taskq_n_threads)

taskq_t                         *mdi_taskq;
static uint_t                   mdi_taskq_n_threads = MDI_TASKQ_N_THREADS;

#define TICKS_PER_SECOND        (drv_usectohz(1000000))

/*
 * The data should be "quiet" for this interval (in seconds) before the
 * vhci cached data is flushed to the disk.
 */
static int mdi_vhcache_flush_delay = 10;

/* number of seconds the vhcache flush daemon will sleep idle before exiting */
static int mdi_vhcache_flush_daemon_idle_time = 60;

/*
 * MDI falls back to discovery of all paths when a bus_config_one fails.
 * The following parameters can be used to tune this operation.
 *
 * mdi_path_discovery_boot
 *      Number of times path discovery will be attempted during early boot.
 *      Probably there is no reason to ever set this value to greater than one.
 *
 * mdi_path_discovery_postboot
 *      Number of times path discovery will be attempted after early boot.
 *      Set it to a minimum of two to allow for discovery of iscsi paths which
 *      may happen very late during booting.
 *
 * mdi_path_discovery_interval
 *      Minimum number of seconds MDI will wait between successive discovery
 *      of all paths. Set it to -1 to disable discovery of all paths.
 */
static int mdi_path_discovery_boot = 1;
static int mdi_path_discovery_postboot = 2;
static int mdi_path_discovery_interval = 10;

/*
 * number of seconds the asynchronous configuration thread will sleep idle
 * before exiting.
 */
static int mdi_async_config_idle_time = 600;

static int mdi_bus_config_cache_hash_size = 256;

/* turns off multithreaded configuration for certain operations */
static int mdi_mtc_off = 0;

/*
 * The "path" to a pathinfo node is identical to the /devices path to a
 * devinfo node had the device been enumerated under a pHCI instead of
 * a vHCI.  This pathinfo "path" is associated with a 'path_instance'.
 * This association persists across create/delete of the pathinfo nodes,
 * but not across reboot.
 */
static uint_t           mdi_pathmap_instance = 1;       /* 0 -> any path */
static int              mdi_pathmap_hash_size = 256;
static kmutex_t         mdi_pathmap_mutex;
static mod_hash_t       *mdi_pathmap_bypath;            /* "path"->instance */
static mod_hash_t       *mdi_pathmap_byinstance;        /* instance->"path" */
static mod_hash_t       *mdi_pathmap_sbyinstance;       /* inst->shortpath */

/*
 * MDI component property name/value string definitions
 */
const char              *mdi_component_prop = "mpxio-component";
const char              *mdi_component_prop_vhci = "vhci";
const char              *mdi_component_prop_phci = "phci";
const char              *mdi_component_prop_client = "client";

/*
 * MDI client global unique identifier property name
 */
const char              *mdi_client_guid_prop = "client-guid";

/*
 * MDI client load balancing property name/value string definitions
 */
const char              *mdi_load_balance = "load-balance";
const char              *mdi_load_balance_none = "none";
const char              *mdi_load_balance_rr = "round-robin";
const char              *mdi_load_balance_lba = "logical-block";

/*
 * Obsolete vHCI class definition; to be removed after Leadville update
 */
const char *mdi_vhci_class_scsi = MDI_HCI_CLASS_SCSI;

static char vhci_greeting[] =
        "\tThere already exists one vHCI driver for class %s\n"
        "\tOnly one vHCI driver for each class is allowed\n";

/*
 * Static function prototypes
 */
static int              i_mdi_phci_offline(dev_info_t *, uint_t);
static int              i_mdi_client_offline(dev_info_t *, uint_t);
static int              i_mdi_phci_pre_detach(dev_info_t *, ddi_detach_cmd_t);
static void             i_mdi_phci_post_detach(dev_info_t *,
                            ddi_detach_cmd_t, int);
static int              i_mdi_client_pre_detach(dev_info_t *,
                            ddi_detach_cmd_t);
static void             i_mdi_client_post_detach(dev_info_t *,
                            ddi_detach_cmd_t, int);
static void             i_mdi_pm_hold_pip(mdi_pathinfo_t *);
static void             i_mdi_pm_rele_pip(mdi_pathinfo_t *);
static int              i_mdi_lba_lb(mdi_client_t *ct,
                            mdi_pathinfo_t **ret_pip, struct buf *buf);
static void             i_mdi_pm_hold_client(mdi_client_t *, int);
static void             i_mdi_pm_rele_client(mdi_client_t *, int);
static void             i_mdi_pm_reset_client(mdi_client_t *);
static int              i_mdi_power_all_phci(mdi_client_t *);
static void             i_mdi_log_sysevent(dev_info_t *, char *, char *);


/*
 * Internal mdi_pathinfo node functions
 */
static void             i_mdi_pi_kstat_destroy(mdi_pathinfo_t *);

static mdi_vhci_t       *i_mdi_vhci_class2vhci(char *);
static mdi_vhci_t       *i_devi_get_vhci(dev_info_t *);
static mdi_phci_t       *i_devi_get_phci(dev_info_t *);
static void             i_mdi_phci_lock(mdi_phci_t *, mdi_pathinfo_t *);
static void             i_mdi_phci_unlock(mdi_phci_t *);
static mdi_pathinfo_t   *i_mdi_pi_alloc(mdi_phci_t *, char *, mdi_client_t *);
static void             i_mdi_phci_add_path(mdi_phci_t *, mdi_pathinfo_t *);
static void             i_mdi_client_add_path(mdi_client_t *, mdi_pathinfo_t *);
static void             i_mdi_pi_free(mdi_phci_t *ph, mdi_pathinfo_t *,
                            mdi_client_t *);
static void             i_mdi_phci_remove_path(mdi_phci_t *, mdi_pathinfo_t *);
static void             i_mdi_client_remove_path(mdi_client_t *,
                            mdi_pathinfo_t *);

static int              i_mdi_pi_state_change(mdi_pathinfo_t *,
                            mdi_pathinfo_state_t, int);
static int              i_mdi_pi_offline(mdi_pathinfo_t *, int);
static dev_info_t       *i_mdi_devinfo_create(mdi_vhci_t *, char *, char *,
                            char **, int);
static dev_info_t       *i_mdi_devinfo_find(mdi_vhci_t *, char *, char *);
static int              i_mdi_devinfo_remove(dev_info_t *, dev_info_t *, int);
static int              i_mdi_is_child_present(dev_info_t *, dev_info_t *);
static mdi_client_t     *i_mdi_client_alloc(mdi_vhci_t *, char *, char *);
static void             i_mdi_client_enlist_table(mdi_vhci_t *, mdi_client_t *);
static void             i_mdi_client_delist_table(mdi_vhci_t *, mdi_client_t *);
static mdi_client_t     *i_mdi_client_find(mdi_vhci_t *, char *, char *);
static void             i_mdi_client_update_state(mdi_client_t *);
static int              i_mdi_client_compute_state(mdi_client_t *,
                            mdi_phci_t *);
static void             i_mdi_client_lock(mdi_client_t *, mdi_pathinfo_t *);
static void             i_mdi_client_unlock(mdi_client_t *);
static int              i_mdi_client_free(mdi_vhci_t *, mdi_client_t *);
static mdi_client_t     *i_devi_get_client(dev_info_t *);
/*
 * NOTE: this will be removed once the NWS files are changed to use the new
 * mdi_{enable,disable}_path interfaces
 */
static int              i_mdi_pi_enable_disable(dev_info_t *, dev_info_t *,
                                int, int);
static mdi_pathinfo_t   *i_mdi_enable_disable_path(mdi_pathinfo_t *pip,
                                mdi_vhci_t *vh, int flags, int op);
/*
 * Failover related function prototypes
 */
static int              i_mdi_failover(void *);

/*
 * misc internal functions
 */
static int              i_mdi_get_hash_key(char *);
static int              i_map_nvlist_error_to_mdi(int);
static void             i_mdi_report_path_state(mdi_client_t *,
                            mdi_pathinfo_t *);

static void             setup_vhci_cache(mdi_vhci_t *);
static int              destroy_vhci_cache(mdi_vhci_t *);
static int              stop_vhcache_async_threads(mdi_vhci_config_t *);
static boolean_t        stop_vhcache_flush_thread(void *, int);
static void             free_string_array(char **, int);
static void             free_vhcache_phci(mdi_vhcache_phci_t *);
static void             free_vhcache_pathinfo(mdi_vhcache_pathinfo_t *);
static void             free_vhcache_client(mdi_vhcache_client_t *);
static int              mainnvl_to_vhcache(mdi_vhci_cache_t *, nvlist_t *);
static nvlist_t         *vhcache_to_mainnvl(mdi_vhci_cache_t *);
static void             vhcache_phci_add(mdi_vhci_config_t *, mdi_phci_t *);
static void             vhcache_phci_remove(mdi_vhci_config_t *, mdi_phci_t *);
static void             vhcache_pi_add(mdi_vhci_config_t *,
                            struct mdi_pathinfo *);
static void             vhcache_pi_remove(mdi_vhci_config_t *,
                            struct mdi_pathinfo *);
static void             free_phclient_path_list(mdi_phys_path_t *);
static void             sort_vhcache_paths(mdi_vhcache_client_t *);
static int              flush_vhcache(mdi_vhci_config_t *, int);
static void             vhcache_dirty(mdi_vhci_config_t *);
static void             free_async_client_config(mdi_async_client_config_t *);
static void             single_threaded_vhconfig_enter(mdi_vhci_config_t *);
static void             single_threaded_vhconfig_exit(mdi_vhci_config_t *);
static nvlist_t         *read_on_disk_vhci_cache(char *);
extern int              fread_nvlist(char *, nvlist_t **);
extern int              fwrite_nvlist(char *, nvlist_t *);

/* called once when first vhci registers with mdi */
static void
i_mdi_init()
{
        static int initialized = 0;

        if (initialized)
                return;
        initialized = 1;

        mutex_init(&mdi_mutex, NULL, MUTEX_DEFAULT, NULL);

        /* Create our taskq resources */
        mdi_taskq = taskq_create("mdi_taskq", mdi_taskq_n_threads,
            MDI_TASKQ_PRI, MDI_TASKQ_MINALLOC, MDI_TASKQ_MAXALLOC,
            TASKQ_PREPOPULATE | TASKQ_CPR_SAFE);
        ASSERT(mdi_taskq != NULL);      /* taskq_create never fails */

        /* Allocate ['path_instance' <-> "path"] maps */
        mutex_init(&mdi_pathmap_mutex, NULL, MUTEX_DRIVER, NULL);
        mdi_pathmap_bypath = mod_hash_create_strhash(
            "mdi_pathmap_bypath", mdi_pathmap_hash_size,
            mod_hash_null_valdtor);
        mdi_pathmap_byinstance = mod_hash_create_idhash(
            "mdi_pathmap_byinstance", mdi_pathmap_hash_size,
            mod_hash_null_valdtor);
        mdi_pathmap_sbyinstance = mod_hash_create_idhash(
            "mdi_pathmap_sbyinstance", mdi_pathmap_hash_size,
            mod_hash_null_valdtor);
}

/*
 * mdi_get_component_type():
 *              Return mpxio component type
 * Return Values:
 *              MDI_COMPONENT_NONE
 *              MDI_COMPONENT_VHCI
 *              MDI_COMPONENT_PHCI
 *              MDI_COMPONENT_CLIENT
 * XXX This doesn't work under multi-level MPxIO and should be
 *      removed when clients migrate mdi_component_is_*() interfaces.
 */
int
mdi_get_component_type(dev_info_t *dip)
{
        return (DEVI(dip)->devi_mdi_component);
}

/*
 * mdi_vhci_register():
 *              Register a vHCI module with the mpxio framework
 *              mdi_vhci_register() is called by vHCI drivers to register the
 *              'class_driver' vHCI driver and its MDI entrypoints with the
 *              mpxio framework.  The vHCI driver must call this interface as
 *              part of its attach(9e) handler.
 *              Competing threads may try to attach mdi_vhci_register() as
 *              the vHCI drivers are loaded and attached as a result of pHCI
 *              driver instance registration (mdi_phci_register()) with the
 *              framework.
 * Return Values:
 *              MDI_SUCCESS
 *              MDI_FAILURE
 */
/*ARGSUSED*/
int
mdi_vhci_register(char *class, dev_info_t *vdip, mdi_vhci_ops_t *vops,
    int flags)
{
        mdi_vhci_t              *vh = NULL;

        /* Registrant can't be older */
        ASSERT(vops->vo_revision <= MDI_VHCI_OPS_REV);

#ifdef DEBUG
        /*
         * IB nexus driver is loaded only when IB hardware is present.
         * In order to be able to do this there is a need to drive the loading
         * and attaching of the IB nexus driver (especially when an IB hardware
         * is dynamically plugged in) when an IB HCA driver (PHCI)
         * is being attached. Unfortunately this gets into the limitations
         * of devfs as there seems to be no clean way to drive configuration
         * of a subtree from another subtree of a devfs. Hence, do not ASSERT
         * for IB.
         */
        if (strcmp(class, MDI_HCI_CLASS_IB) != 0)
                ASSERT(DEVI_BUSY_OWNED(ddi_get_parent(vdip)));
#endif

        i_mdi_init();

        mutex_enter(&mdi_mutex);
        /*
         * Scan for already registered vhci
         */
        for (vh = mdi_vhci_head; vh != NULL; vh = vh->vh_next) {
                if (strcmp(vh->vh_class, class) == 0) {
                        /*
                         * vHCI has already been created.  Check for valid
                         * vHCI ops registration.  We only support one vHCI
                         * module per class
                         */
                        if (vh->vh_ops != NULL) {
                                mutex_exit(&mdi_mutex);
                                cmn_err(CE_NOTE, vhci_greeting, class);
                                return (MDI_FAILURE);
                        }
                        break;
                }
        }

        /*
         * if not yet created, create the vHCI component
         */
        if (vh == NULL) {
                struct client_hash      *hash = NULL;
                char                    *load_balance;

                /*
                 * Allocate and initialize the mdi extensions
                 */
                vh = kmem_zalloc(sizeof (mdi_vhci_t), KM_SLEEP);
                hash = kmem_zalloc(mdi_client_table_size * sizeof (*hash),
                    KM_SLEEP);
                vh->vh_client_table = hash;
                vh->vh_class = kmem_zalloc(strlen(class) + 1, KM_SLEEP);
                (void) strcpy(vh->vh_class, class);
                vh->vh_lb = LOAD_BALANCE_RR;
                if (ddi_prop_lookup_string(DDI_DEV_T_ANY, vdip,
                    0, LOAD_BALANCE_PROP, &load_balance) == DDI_SUCCESS) {
                        if (strcmp(load_balance, LOAD_BALANCE_PROP_NONE) == 0) {
                                vh->vh_lb = LOAD_BALANCE_NONE;
                        } else if (strcmp(load_balance, LOAD_BALANCE_PROP_LBA)
                                    == 0) {
                                vh->vh_lb = LOAD_BALANCE_LBA;
                        }
                        ddi_prop_free(load_balance);
                }

                mutex_init(&vh->vh_phci_mutex, NULL, MUTEX_DEFAULT, NULL);
                mutex_init(&vh->vh_client_mutex, NULL, MUTEX_DEFAULT, NULL);

                /*
                 * Store the vHCI ops vectors
                 */
                vh->vh_dip = vdip;
                vh->vh_ops = vops;

                setup_vhci_cache(vh);

                if (mdi_vhci_head == NULL) {
                        mdi_vhci_head = vh;
                }
                if (mdi_vhci_tail) {
                        mdi_vhci_tail->vh_next = vh;
                }
                mdi_vhci_tail = vh;
                mdi_vhci_count++;
        }

        /*
         * Claim the devfs node as a vhci component
         */
        DEVI(vdip)->devi_mdi_component |= MDI_COMPONENT_VHCI;

        /*
         * Initialize our back reference from dev_info node
         */
        DEVI(vdip)->devi_mdi_xhci = (caddr_t)vh;
        mutex_exit(&mdi_mutex);
        return (MDI_SUCCESS);
}

/*
 * mdi_vhci_unregister():
 *              Unregister a vHCI module from mpxio framework
 *              mdi_vhci_unregister() is called from the detach(9E) entrypoint
 *              of a vhci to unregister it from the framework.
 * Return Values:
 *              MDI_SUCCESS
 *              MDI_FAILURE
 */
/*ARGSUSED*/
int
mdi_vhci_unregister(dev_info_t *vdip, int flags)
{
        mdi_vhci_t      *found, *vh, *prev = NULL;

        ASSERT(DEVI_BUSY_OWNED(ddi_get_parent(vdip)));

        /*
         * Check for invalid VHCI
         */
        if ((vh = i_devi_get_vhci(vdip)) == NULL)
                return (MDI_FAILURE);

        /*
         * Scan the list of registered vHCIs for a match
         */
        mutex_enter(&mdi_mutex);
        for (found = mdi_vhci_head; found != NULL; found = found->vh_next) {
                if (found == vh)
                        break;
                prev = found;
        }

        if (found == NULL) {
                mutex_exit(&mdi_mutex);
                return (MDI_FAILURE);
        }

        /*
         * Check the vHCI, pHCI and client count. All the pHCIs and clients
         * should have been unregistered, before a vHCI can be
         * unregistered.
         */
        MDI_VHCI_PHCI_LOCK(vh);
        if (vh->vh_refcnt || vh->vh_phci_count || vh->vh_client_count) {
                MDI_VHCI_PHCI_UNLOCK(vh);
                mutex_exit(&mdi_mutex);
                return (MDI_FAILURE);
        }
        MDI_VHCI_PHCI_UNLOCK(vh);

        if (destroy_vhci_cache(vh) != MDI_SUCCESS) {
                mutex_exit(&mdi_mutex);
                return (MDI_FAILURE);
        }

        /*
         * Remove the vHCI from the global list
         */
        if (vh == mdi_vhci_head) {
                mdi_vhci_head = vh->vh_next;
        } else {
                prev->vh_next = vh->vh_next;
        }
        if (vh == mdi_vhci_tail) {
                mdi_vhci_tail = prev;
        }
        mdi_vhci_count--;
        mutex_exit(&mdi_mutex);

        vh->vh_ops = NULL;
        DEVI(vdip)->devi_mdi_component &= ~MDI_COMPONENT_VHCI;
        DEVI(vdip)->devi_mdi_xhci = NULL;
        kmem_free(vh->vh_class, strlen(vh->vh_class)+1);
        kmem_free(vh->vh_client_table,
            mdi_client_table_size * sizeof (struct client_hash));
        mutex_destroy(&vh->vh_phci_mutex);
        mutex_destroy(&vh->vh_client_mutex);

        kmem_free(vh, sizeof (mdi_vhci_t));
        return (MDI_SUCCESS);
}

/*
 * i_mdi_vhci_class2vhci():
 *              Look for a matching vHCI module given a vHCI class name
 * Return Values:
 *              Handle to a vHCI component
 *              NULL
 */
static mdi_vhci_t *
i_mdi_vhci_class2vhci(char *class)
{
        mdi_vhci_t      *vh = NULL;

        ASSERT(!MUTEX_HELD(&mdi_mutex));

        mutex_enter(&mdi_mutex);
        for (vh = mdi_vhci_head; vh != NULL; vh = vh->vh_next) {
                if (strcmp(vh->vh_class, class) == 0) {
                        break;
                }
        }
        mutex_exit(&mdi_mutex);
        return (vh);
}

/*
 * i_devi_get_vhci():
 *              Utility function to get the handle to a vHCI component
 * Return Values:
 *              Handle to a vHCI component
 *              NULL
 */
mdi_vhci_t *
i_devi_get_vhci(dev_info_t *vdip)
{
        mdi_vhci_t      *vh = NULL;
        if (MDI_VHCI(vdip)) {
                vh = (mdi_vhci_t *)DEVI(vdip)->devi_mdi_xhci;
        }
        return (vh);
}

/*
 * mdi_phci_register():
 *              Register a pHCI module with mpxio framework
 *              mdi_phci_register() is called by pHCI drivers to register with
 *              the mpxio framework and a specific 'class_driver' vHCI.  The
 *              pHCI driver must call this interface as part of its attach(9e)
 *              handler.
 * Return Values:
 *              MDI_SUCCESS
 *              MDI_FAILURE
 */
/*ARGSUSED*/
int
mdi_phci_register(char *class, dev_info_t *pdip, int flags)
{
        mdi_phci_t              *ph;
        mdi_vhci_t              *vh;
        char                    *data;

        /*
         * Some subsystems, like fcp, perform pHCI registration from a
         * different thread than the one doing the pHCI attach(9E) - the
         * driver attach code is waiting for this other thread to complete.
         * This means we can only ASSERT DEVI_BUSY_CHANGING of parent
         * (indicating that some thread has done an ndi_devi_enter of parent)
         * not DEVI_BUSY_OWNED (which would indicate that we did the enter).
         */
        ASSERT(DEVI_BUSY_CHANGING(ddi_get_parent(pdip)));

        /*
         * Check for mpxio-disable property. Enable mpxio if the property is
         * missing or not set to "yes".
         * If the property is set to "yes" then emit a brief message.
         */
        if ((ddi_prop_lookup_string(DDI_DEV_T_ANY, pdip, 0, "mpxio-disable",
            &data) == DDI_SUCCESS)) {
                if (strcmp(data, "yes") == 0) {
                        MDI_DEBUG(1, (MDI_CONT, pdip,
                            "?multipath capabilities disabled via %s.conf.",
                            ddi_driver_name(pdip)));
                        ddi_prop_free(data);
                        return (MDI_FAILURE);
                }
                ddi_prop_free(data);
        }

        /*
         * Search for a matching vHCI
         */
        vh = (mdi_vhci_t *)i_mdi_vhci_class2vhci(class);
        if (vh == NULL) {
                return (MDI_FAILURE);
        }

        ph = kmem_zalloc(sizeof (mdi_phci_t), KM_SLEEP);
        mutex_init(&ph->ph_mutex, NULL, MUTEX_DEFAULT, NULL);
        ph->ph_dip = pdip;
        ph->ph_vhci = vh;
        ph->ph_next = NULL;
        ph->ph_unstable = 0;
        ph->ph_vprivate = 0;
        cv_init(&ph->ph_unstable_cv, NULL, CV_DRIVER, NULL);

        MDI_PHCI_LOCK(ph);
        MDI_PHCI_SET_POWER_UP(ph);
        MDI_PHCI_UNLOCK(ph);
        DEVI(pdip)->devi_mdi_component |= MDI_COMPONENT_PHCI;
        DEVI(pdip)->devi_mdi_xhci = (caddr_t)ph;

        vhcache_phci_add(vh->vh_config, ph);

        MDI_VHCI_PHCI_LOCK(vh);
        if (vh->vh_phci_head == NULL) {
                vh->vh_phci_head = ph;
        }
        if (vh->vh_phci_tail) {
                vh->vh_phci_tail->ph_next = ph;
        }
        vh->vh_phci_tail = ph;
        vh->vh_phci_count++;
        MDI_VHCI_PHCI_UNLOCK(vh);

        i_mdi_log_sysevent(pdip, class, ESC_DDI_INITIATOR_REGISTER);
        return (MDI_SUCCESS);
}

/*
 * mdi_phci_unregister():
 *              Unregister a pHCI module from mpxio framework
 *              mdi_phci_unregister() is called by the pHCI drivers from their
 *              detach(9E) handler to unregister their instances from the
 *              framework.
 * Return Values:
 *              MDI_SUCCESS
 *              MDI_FAILURE
 */
/*ARGSUSED*/
int
mdi_phci_unregister(dev_info_t *pdip, int flags)
{
        mdi_vhci_t              *vh;
        mdi_phci_t              *ph;
        mdi_phci_t              *tmp;
        mdi_phci_t              *prev = NULL;
        mdi_pathinfo_t          *pip;

        ASSERT(DEVI_BUSY_CHANGING(ddi_get_parent(pdip)));

        ph = i_devi_get_phci(pdip);
        if (ph == NULL) {
                MDI_DEBUG(1, (MDI_WARN, pdip, "!not a valid pHCI"));
                return (MDI_FAILURE);
        }

        vh = ph->ph_vhci;
        ASSERT(vh != NULL);
        if (vh == NULL) {
                MDI_DEBUG(1, (MDI_WARN, pdip, "!not a valid vHCI"));
                return (MDI_FAILURE);
        }

        MDI_VHCI_PHCI_LOCK(vh);
        tmp = vh->vh_phci_head;
        while (tmp) {
                if (tmp == ph) {
                        break;
                }
                prev = tmp;
                tmp = tmp->ph_next;
        }

        if (ph == vh->vh_phci_head) {
                vh->vh_phci_head = ph->ph_next;
        } else {
                prev->ph_next = ph->ph_next;
        }

        if (ph == vh->vh_phci_tail) {
                vh->vh_phci_tail = prev;
        }

        vh->vh_phci_count--;
        MDI_VHCI_PHCI_UNLOCK(vh);

        /* Walk remaining pathinfo nodes and disassociate them from pHCI */
        MDI_PHCI_LOCK(ph);
        for (pip = (mdi_pathinfo_t *)ph->ph_path_head; pip;
            pip = (mdi_pathinfo_t *)MDI_PI(pip)->pi_phci_link)
                MDI_PI(pip)->pi_phci = NULL;
        MDI_PHCI_UNLOCK(ph);

        i_mdi_log_sysevent(pdip, ph->ph_vhci->vh_class,
            ESC_DDI_INITIATOR_UNREGISTER);
        vhcache_phci_remove(vh->vh_config, ph);
        cv_destroy(&ph->ph_unstable_cv);
        mutex_destroy(&ph->ph_mutex);
        kmem_free(ph, sizeof (mdi_phci_t));
        DEVI(pdip)->devi_mdi_component &= ~MDI_COMPONENT_PHCI;
        DEVI(pdip)->devi_mdi_xhci = NULL;
        return (MDI_SUCCESS);
}

/*
 * i_devi_get_phci():
 *              Utility function to return the phci extensions.
 */
static mdi_phci_t *
i_devi_get_phci(dev_info_t *pdip)
{
        mdi_phci_t      *ph = NULL;

        if (MDI_PHCI(pdip)) {
                ph = (mdi_phci_t *)DEVI(pdip)->devi_mdi_xhci;
        }
        return (ph);
}

/*
 * Single thread mdi entry into devinfo node for modifying its children.
 * If necessary we perform an ndi_devi_enter of the vHCI before doing
 * an ndi_devi_enter of 'dip'.  We maintain circular in two parts: one
 * for the vHCI and one for the pHCI.
 */
void
mdi_devi_enter(dev_info_t *phci_dip, int *circular)
{
        dev_info_t      *vdip;
        int             vcircular, pcircular;

        /* Verify calling context */
        ASSERT(MDI_PHCI(phci_dip));
        vdip = mdi_devi_get_vdip(phci_dip);
        ASSERT(vdip);                   /* A pHCI always has a vHCI */

        /*
         * If pHCI is detaching then the framework has already entered the
         * vHCI on a threads that went down the code path leading to
         * detach_node().  This framework enter of the vHCI during pHCI
         * detach is done to avoid deadlock with vHCI power management
         * operations which enter the vHCI and the enter down the path
         * to the pHCI. If pHCI is detaching then we piggyback this calls
         * enter of the vHCI on frameworks vHCI enter that has already
         * occurred - this is OK because we know that the framework thread
         * doing detach is waiting for our completion.
         *
         * We should DEVI_IS_DETACHING under an enter of the parent to avoid
         * race with detach - but we can't do that because the framework has
         * already entered the parent, so we have some complexity instead.
         */
        for (;;) {
                if (ndi_devi_tryenter(vdip, &vcircular)) {
                        ASSERT(vcircular != -1);
                        if (DEVI_IS_DETACHING(phci_dip)) {
                                ndi_devi_exit(vdip, vcircular);
                                vcircular = -1;
                        }
                        break;
                } else if (DEVI_IS_DETACHING(phci_dip)) {
                        vcircular = -1;
                        break;
                } else if (servicing_interrupt()) {
                        /*
                         * Don't delay an interrupt (and ensure adaptive
                         * mutex inversion support).
                         */
                        ndi_devi_enter(vdip, &vcircular);
                        break;
                } else {
                        delay_random(mdi_delay);
                }
        }

        ndi_devi_enter(phci_dip, &pcircular);
        *circular = (vcircular << 16) | (pcircular & 0xFFFF);
}

/*
 * Attempt to mdi_devi_enter.
 */
int
mdi_devi_tryenter(dev_info_t *phci_dip, int *circular)
{
        dev_info_t      *vdip;
        int             vcircular, pcircular;

        /* Verify calling context */
        ASSERT(MDI_PHCI(phci_dip));
        vdip = mdi_devi_get_vdip(phci_dip);
        ASSERT(vdip);                   /* A pHCI always has a vHCI */

        if (ndi_devi_tryenter(vdip, &vcircular)) {
                if (ndi_devi_tryenter(phci_dip, &pcircular)) {
                        *circular = (vcircular << 16) | (pcircular & 0xFFFF);
                        return (1);     /* locked */
                }
                ndi_devi_exit(vdip, vcircular);
        }
        return (0);                     /* busy */
}

/*
 * Release mdi_devi_enter or successful mdi_devi_tryenter.
 */
void
mdi_devi_exit(dev_info_t *phci_dip, int circular)
{
        dev_info_t      *vdip;
        int             vcircular, pcircular;

        /* Verify calling context */
        ASSERT(MDI_PHCI(phci_dip));
        vdip = mdi_devi_get_vdip(phci_dip);
        ASSERT(vdip);                   /* A pHCI always has a vHCI */

        /* extract two circular recursion values from single int */
        pcircular = (short)(circular & 0xFFFF);
        vcircular = (short)((circular >> 16) & 0xFFFF);

        ndi_devi_exit(phci_dip, pcircular);
        if (vcircular != -1)
                ndi_devi_exit(vdip, vcircular);
}

/*
 * The functions mdi_devi_exit_phci() and mdi_devi_enter_phci() are used
 * around a pHCI drivers calls to mdi_pi_online/offline, after holding
 * the pathinfo node via mdi_hold_path/mdi_rele_path, to avoid deadlock
 * with vHCI power management code during path online/offline.  Each
 * mdi_devi_exit_phci must have a matching mdi_devi_enter_phci, and both must
 * occur within the scope of an active mdi_devi_enter that establishes the
 * circular value.
 */
void
mdi_devi_exit_phci(dev_info_t *phci_dip, int circular)
{
        int             pcircular;

        /* Verify calling context */
        ASSERT(MDI_PHCI(phci_dip));

        /* Keep hold on pHCI until we reenter in mdi_devi_enter_phci */
        ndi_hold_devi(phci_dip);

        pcircular = (short)(circular & 0xFFFF);
        ndi_devi_exit(phci_dip, pcircular);
}

void
mdi_devi_enter_phci(dev_info_t *phci_dip, int *circular)
{
        int             pcircular;

        /* Verify calling context */
        ASSERT(MDI_PHCI(phci_dip));

        ndi_devi_enter(phci_dip, &pcircular);

        /* Drop hold from mdi_devi_exit_phci. */
        ndi_rele_devi(phci_dip);

        /* verify matching mdi_devi_exit_phci/mdi_devi_enter_phci use */
        ASSERT(pcircular == ((short)(*circular & 0xFFFF)));
}

/*
 * mdi_devi_get_vdip():
 *              given a pHCI dip return vHCI dip
 */
dev_info_t *
mdi_devi_get_vdip(dev_info_t *pdip)
{
        mdi_phci_t      *ph;

        ph = i_devi_get_phci(pdip);
        if (ph && ph->ph_vhci)
                return (ph->ph_vhci->vh_dip);
        return (NULL);
}

/*
 * mdi_devi_pdip_entered():
 *              Return 1 if we are vHCI and have done an ndi_devi_enter
 *              of a pHCI
 */
int
mdi_devi_pdip_entered(dev_info_t *vdip)
{
        mdi_vhci_t      *vh;
        mdi_phci_t      *ph;

        vh = i_devi_get_vhci(vdip);
        if (vh == NULL)
                return (0);

        MDI_VHCI_PHCI_LOCK(vh);
        ph = vh->vh_phci_head;
        while (ph) {
                if (ph->ph_dip && DEVI_BUSY_OWNED(ph->ph_dip)) {
                        MDI_VHCI_PHCI_UNLOCK(vh);
                        return (1);
                }
                ph = ph->ph_next;
        }
        MDI_VHCI_PHCI_UNLOCK(vh);
        return (0);
}

/*
 * mdi_phci_path2devinfo():
 *              Utility function to search for a valid phci device given
 *              the devfs pathname.
 */
dev_info_t *
mdi_phci_path2devinfo(dev_info_t *vdip, caddr_t pathname)
{
        char            *temp_pathname;
        mdi_vhci_t      *vh;
        mdi_phci_t      *ph;
        dev_info_t      *pdip = NULL;

        vh = i_devi_get_vhci(vdip);
        ASSERT(vh != NULL);

        if (vh == NULL) {
                /*
                 * Invalid vHCI component, return failure
                 */
                return (NULL);
        }

        temp_pathname = kmem_zalloc(MAXPATHLEN, KM_SLEEP);
        MDI_VHCI_PHCI_LOCK(vh);
        ph = vh->vh_phci_head;
        while (ph != NULL) {
                pdip = ph->ph_dip;
                ASSERT(pdip != NULL);
                *temp_pathname = '\0';
                (void) ddi_pathname(pdip, temp_pathname);
                if (strcmp(temp_pathname, pathname) == 0) {
                        break;
                }
                ph = ph->ph_next;
        }
        if (ph == NULL) {
                pdip = NULL;
        }
        MDI_VHCI_PHCI_UNLOCK(vh);
        kmem_free(temp_pathname, MAXPATHLEN);
        return (pdip);
}

/*
 * mdi_phci_get_path_count():
 *              get number of path information nodes associated with a given
 *              pHCI device.
 */
int
mdi_phci_get_path_count(dev_info_t *pdip)
{
        mdi_phci_t      *ph;
        int             count = 0;

        ph = i_devi_get_phci(pdip);
        if (ph != NULL) {
                count = ph->ph_path_count;
        }
        return (count);
}

/*
 * i_mdi_phci_lock():
 *              Lock a pHCI device
 * Return Values:
 *              None
 * Note:
 *              The default locking order is:
 *              _NOTE(LOCK_ORDER(mdi_phci::ph_mutex mdi_pathinfo::pi_mutex))
 *              But there are number of situations where locks need to be
 *              grabbed in reverse order.  This routine implements try and lock
 *              mechanism depending on the requested parameter option.
 */
static void
i_mdi_phci_lock(mdi_phci_t *ph, mdi_pathinfo_t *pip)
{
        if (pip) {
                /* Reverse locking is requested. */
                while (MDI_PHCI_TRYLOCK(ph) == 0) {
                        if (servicing_interrupt()) {
                                MDI_PI_HOLD(pip);
                                MDI_PI_UNLOCK(pip);
                                MDI_PHCI_LOCK(ph);
                                MDI_PI_LOCK(pip);
                                MDI_PI_RELE(pip);
                                break;
                        } else {
                                /*
                                 * tryenter failed. Try to grab again
                                 * after a small delay
                                 */
                                MDI_PI_HOLD(pip);
                                MDI_PI_UNLOCK(pip);
                                delay_random(mdi_delay);
                                MDI_PI_LOCK(pip);
                                MDI_PI_RELE(pip);
                        }
                }
        } else {
                MDI_PHCI_LOCK(ph);
        }
}

/*
 * i_mdi_phci_unlock():
 *              Unlock the pHCI component
 */
static void
i_mdi_phci_unlock(mdi_phci_t *ph)
{
        MDI_PHCI_UNLOCK(ph);
}

/*
 * i_mdi_devinfo_create():
 *              create client device's devinfo node
 * Return Values:
 *              dev_info
 *              NULL
 * Notes:
 */
static dev_info_t *
i_mdi_devinfo_create(mdi_vhci_t *vh, char *name, char *guid,
        char **compatible, int ncompatible)
{
        dev_info_t *cdip = NULL;

        ASSERT(MDI_VHCI_CLIENT_LOCKED(vh));

        /* Verify for duplicate entry */
        cdip = i_mdi_devinfo_find(vh, name, guid);
        ASSERT(cdip == NULL);
        if (cdip) {
                cmn_err(CE_WARN,
                    "i_mdi_devinfo_create: client %s@%s already exists",
                        name ? name : "", guid ? guid : "");
        }

        ndi_devi_alloc_sleep(vh->vh_dip, name, DEVI_SID_NODEID, &cdip);
        if (cdip == NULL)
                goto fail;

        /*
         * Create component type and Global unique identifier
         * properties
         */
        if (ndi_prop_update_string(DDI_DEV_T_NONE, cdip,
            MDI_CLIENT_GUID_PROP, guid) != DDI_PROP_SUCCESS) {
                goto fail;
        }

        /* Decorate the node with compatible property */
        if (compatible &&
            (ndi_prop_update_string_array(DDI_DEV_T_NONE, cdip,
            "compatible", compatible, ncompatible) != DDI_PROP_SUCCESS)) {
                goto fail;
        }

        return (cdip);

fail:
        if (cdip) {
                (void) ndi_prop_remove_all(cdip);
                (void) ndi_devi_free(cdip);
        }
        return (NULL);
}

/*
 * i_mdi_devinfo_find():
 *              Find a matching devinfo node for given client node name
 *              and its guid.
 * Return Values:
 *              Handle to a dev_info node or NULL
 */
static dev_info_t *
i_mdi_devinfo_find(mdi_vhci_t *vh, caddr_t name, char *guid)
{
        char                    *data;
        dev_info_t              *cdip = NULL;
        dev_info_t              *ndip = NULL;
        int                     circular;

        ndi_devi_enter(vh->vh_dip, &circular);
        ndip = (dev_info_t *)DEVI(vh->vh_dip)->devi_child;
        while ((cdip = ndip) != NULL) {
                ndip = (dev_info_t *)DEVI(cdip)->devi_sibling;

                if (strcmp(DEVI(cdip)->devi_node_name, name)) {
                        continue;
                }

                if (ddi_prop_lookup_string(DDI_DEV_T_ANY, cdip,
                    DDI_PROP_DONTPASS, MDI_CLIENT_GUID_PROP,
                    &data) != DDI_PROP_SUCCESS) {
                        continue;
                }

                if (strcmp(data, guid) != 0) {
                        ddi_prop_free(data);
                        continue;
                }
                ddi_prop_free(data);
                break;
        }
        ndi_devi_exit(vh->vh_dip, circular);
        return (cdip);
}

/*
 * i_mdi_devinfo_remove():
 *              Remove a client device node
 */
static int
i_mdi_devinfo_remove(dev_info_t *vdip, dev_info_t *cdip, int flags)
{
        int     rv = MDI_SUCCESS;

        if (i_mdi_is_child_present(vdip, cdip) == MDI_SUCCESS ||
            (flags & MDI_CLIENT_FLAGS_DEV_NOT_SUPPORTED)) {
                rv = ndi_devi_offline(cdip, NDI_DEVFS_CLEAN | NDI_DEVI_REMOVE);
                if (rv != NDI_SUCCESS) {
                        MDI_DEBUG(1, (MDI_NOTE, cdip,
                            "!failed: cdip %p", (void *)cdip));
                }
                /*
                 * Convert to MDI error code
                 */
                switch (rv) {
                case NDI_SUCCESS:
                        rv = MDI_SUCCESS;
                        break;
                case NDI_BUSY:
                        rv = MDI_BUSY;
                        break;
                default:
                        rv = MDI_FAILURE;
                        break;
                }
        }
        return (rv);
}

/*
 * i_devi_get_client()
 *              Utility function to get mpxio component extensions
 */
static mdi_client_t *
i_devi_get_client(dev_info_t *cdip)
{
        mdi_client_t    *ct = NULL;

        if (MDI_CLIENT(cdip)) {
                ct = (mdi_client_t *)DEVI(cdip)->devi_mdi_client;
        }
        return (ct);
}

/*
 * i_mdi_is_child_present():
 *              Search for the presence of client device dev_info node
 */
static int
i_mdi_is_child_present(dev_info_t *vdip, dev_info_t *cdip)
{
        int             rv = MDI_FAILURE;
        struct dev_info *dip;
        int             circular;

        ndi_devi_enter(vdip, &circular);
        dip = DEVI(vdip)->devi_child;
        while (dip) {
                if (dip == DEVI(cdip)) {
                        rv = MDI_SUCCESS;
                        break;
                }
                dip = dip->devi_sibling;
        }
        ndi_devi_exit(vdip, circular);
        return (rv);
}


/*
 * i_mdi_client_lock():
 *              Grab client component lock
 * Return Values:
 *              None
 * Note:
 *              The default locking order is:
 *              _NOTE(LOCK_ORDER(mdi_client::ct_mutex mdi_pathinfo::pi_mutex))
 *              But there are number of situations where locks need to be
 *              grabbed in reverse order.  This routine implements try and lock
 *              mechanism depending on the requested parameter option.
 */
static void
i_mdi_client_lock(mdi_client_t *ct, mdi_pathinfo_t *pip)
{
        if (pip) {
                /*
                 * Reverse locking is requested.
                 */
                while (MDI_CLIENT_TRYLOCK(ct) == 0) {
                        if (servicing_interrupt()) {
                                MDI_PI_HOLD(pip);
                                MDI_PI_UNLOCK(pip);
                                MDI_CLIENT_LOCK(ct);
                                MDI_PI_LOCK(pip);
                                MDI_PI_RELE(pip);
                                break;
                        } else {
                                /*
                                 * tryenter failed. Try to grab again
                                 * after a small delay
                                 */
                                MDI_PI_HOLD(pip);
                                MDI_PI_UNLOCK(pip);
                                delay_random(mdi_delay);
                                MDI_PI_LOCK(pip);
                                MDI_PI_RELE(pip);
                        }
                }
        } else {
                MDI_CLIENT_LOCK(ct);
        }
}

/*
 * i_mdi_client_unlock():
 *              Unlock a client component
 */
static void
i_mdi_client_unlock(mdi_client_t *ct)
{
        MDI_CLIENT_UNLOCK(ct);
}

/*
 * i_mdi_client_alloc():
 *              Allocate and initialize a client structure.  Caller should
 *              hold the vhci client lock.
 * Return Values:
 *              Handle to a client component
 */
/*ARGSUSED*/
static mdi_client_t *
i_mdi_client_alloc(mdi_vhci_t *vh, char *name, char *lguid)
{
        mdi_client_t    *ct;

        ASSERT(MDI_VHCI_CLIENT_LOCKED(vh));

        /*
         * Allocate and initialize a component structure.
         */
        ct = kmem_zalloc(sizeof (*ct), KM_SLEEP);
        mutex_init(&ct->ct_mutex, NULL, MUTEX_DEFAULT, NULL);
        ct->ct_hnext = NULL;
        ct->ct_hprev = NULL;
        ct->ct_dip = NULL;
        ct->ct_vhci = vh;
        ct->ct_drvname = kmem_alloc(strlen(name) + 1, KM_SLEEP);
        (void) strcpy(ct->ct_drvname, name);
        ct->ct_guid = kmem_alloc(strlen(lguid) + 1, KM_SLEEP);
        (void) strcpy(ct->ct_guid, lguid);
        ct->ct_cprivate = NULL;
        ct->ct_vprivate = NULL;
        ct->ct_flags = 0;
        ct->ct_state = MDI_CLIENT_STATE_FAILED;
        MDI_CLIENT_LOCK(ct);
        MDI_CLIENT_SET_OFFLINE(ct);
        MDI_CLIENT_SET_DETACH(ct);
        MDI_CLIENT_SET_POWER_UP(ct);
        MDI_CLIENT_UNLOCK(ct);
        ct->ct_failover_flags = 0;
        ct->ct_failover_status = 0;
        cv_init(&ct->ct_failover_cv, NULL, CV_DRIVER, NULL);
        ct->ct_unstable = 0;
        cv_init(&ct->ct_unstable_cv, NULL, CV_DRIVER, NULL);
        cv_init(&ct->ct_powerchange_cv, NULL, CV_DRIVER, NULL);
        ct->ct_lb = vh->vh_lb;
        ct->ct_lb_args =  kmem_zalloc(sizeof (client_lb_args_t), KM_SLEEP);
        ct->ct_lb_args->region_size = LOAD_BALANCE_DEFAULT_REGION_SIZE;
        ct->ct_path_count = 0;
        ct->ct_path_head = NULL;
        ct->ct_path_tail = NULL;
        ct->ct_path_last = NULL;

        /*
         * Add this client component to our client hash queue
         */
        i_mdi_client_enlist_table(vh, ct);
        return (ct);
}

/*
 * i_mdi_client_enlist_table():
 *              Attach the client device to the client hash table. Caller
 *              should hold the vhci client lock.
 */
static void
i_mdi_client_enlist_table(mdi_vhci_t *vh, mdi_client_t *ct)
{
        int                     index;
        struct client_hash      *head;

        ASSERT(MDI_VHCI_CLIENT_LOCKED(vh));

        index = i_mdi_get_hash_key(ct->ct_guid);
        head = &vh->vh_client_table[index];
        ct->ct_hnext = (mdi_client_t *)head->ct_hash_head;
        head->ct_hash_head = ct;
        head->ct_hash_count++;
        vh->vh_client_count++;
}

/*
 * i_mdi_client_delist_table():
 *              Attach the client device to the client hash table.
 *              Caller should hold the vhci client lock.
 */
static void
i_mdi_client_delist_table(mdi_vhci_t *vh, mdi_client_t *ct)
{
        int                     index;
        char                    *guid;
        struct client_hash      *head;
        mdi_client_t            *next;
        mdi_client_t            *last;

        ASSERT(MDI_VHCI_CLIENT_LOCKED(vh));

        guid = ct->ct_guid;
        index = i_mdi_get_hash_key(guid);
        head = &vh->vh_client_table[index];

        last = NULL;
        next = (mdi_client_t *)head->ct_hash_head;
        while (next != NULL) {
                if (next == ct) {
                        break;
                }
                last = next;
                next = next->ct_hnext;
        }

        if (next) {
                head->ct_hash_count--;
                if (last == NULL) {
                        head->ct_hash_head = ct->ct_hnext;
                } else {
                        last->ct_hnext = ct->ct_hnext;
                }
                ct->ct_hnext = NULL;
                vh->vh_client_count--;
        }
}


/*
 * i_mdi_client_free():
 *              Free a client component
 */
static int
i_mdi_client_free(mdi_vhci_t *vh, mdi_client_t *ct)
{
        int             rv = MDI_SUCCESS;
        int             flags = ct->ct_flags;
        dev_info_t      *cdip;
        dev_info_t      *vdip;

        ASSERT(MDI_VHCI_CLIENT_LOCKED(vh));

        vdip = vh->vh_dip;
        cdip = ct->ct_dip;

        (void) ndi_prop_remove(DDI_DEV_T_NONE, cdip, MDI_CLIENT_GUID_PROP);
        DEVI(cdip)->devi_mdi_component &= ~MDI_COMPONENT_CLIENT;
        DEVI(cdip)->devi_mdi_client = NULL;

        /*
         * Clear out back ref. to dev_info_t node
         */
        ct->ct_dip = NULL;

        /*
         * Remove this client from our hash queue
         */
        i_mdi_client_delist_table(vh, ct);

        /*
         * Uninitialize and free the component
         */
        kmem_free(ct->ct_drvname, strlen(ct->ct_drvname) + 1);
        kmem_free(ct->ct_guid, strlen(ct->ct_guid) + 1);
        kmem_free(ct->ct_lb_args, sizeof (client_lb_args_t));
        cv_destroy(&ct->ct_failover_cv);
        cv_destroy(&ct->ct_unstable_cv);
        cv_destroy(&ct->ct_powerchange_cv);
        mutex_destroy(&ct->ct_mutex);
        kmem_free(ct, sizeof (*ct));

        if (cdip != NULL) {
                MDI_VHCI_CLIENT_UNLOCK(vh);
                (void) i_mdi_devinfo_remove(vdip, cdip, flags);
                MDI_VHCI_CLIENT_LOCK(vh);
        }
        return (rv);
}

/*
 * i_mdi_client_find():
 *              Find the client structure corresponding to a given guid
 *              Caller should hold the vhci client lock.
 */
static mdi_client_t *
i_mdi_client_find(mdi_vhci_t *vh, char *cname, char *guid)
{
        int                     index;
        struct client_hash      *head;
        mdi_client_t            *ct;

        ASSERT(MDI_VHCI_CLIENT_LOCKED(vh));

        index = i_mdi_get_hash_key(guid);
        head = &vh->vh_client_table[index];

        ct = head->ct_hash_head;
        while (ct != NULL) {
                if (strcmp(ct->ct_guid, guid) == 0 &&
                    (cname == NULL || strcmp(ct->ct_drvname, cname) == 0)) {
                        break;
                }
                ct = ct->ct_hnext;
        }
        return (ct);
}

/*
 * i_mdi_client_update_state():
 *              Compute and update client device state
 * Notes:
 *              A client device can be in any of three possible states:
 *
 *              MDI_CLIENT_STATE_OPTIMAL - Client in optimal state with more
 *              one online/standby paths. Can tolerate failures.
 *              MDI_CLIENT_STATE_DEGRADED - Client device in degraded state with
 *              no alternate paths available as standby. A failure on the online
 *              would result in loss of access to device data.
 *              MDI_CLIENT_STATE_FAILED - Client device in failed state with
 *              no paths available to access the device.
 */
static void
i_mdi_client_update_state(mdi_client_t *ct)
{
        int state;

        ASSERT(MDI_CLIENT_LOCKED(ct));
        state = i_mdi_client_compute_state(ct, NULL);
        MDI_CLIENT_SET_STATE(ct, state);
}

/*
 * i_mdi_client_compute_state():
 *              Compute client device state
 *
 *              mdi_phci_t *    Pointer to pHCI structure which should
 *                              while computing the new value.  Used by
 *                              i_mdi_phci_offline() to find the new
 *                              client state after DR of a pHCI.
 */
static int
i_mdi_client_compute_state(mdi_client_t *ct, mdi_phci_t *ph)
{
        int             state;
        int             online_count = 0;
        int             standby_count = 0;
        mdi_pathinfo_t  *pip, *next;

        ASSERT(MDI_CLIENT_LOCKED(ct));
        pip = ct->ct_path_head;
        while (pip != NULL) {
                MDI_PI_LOCK(pip);
                next = (mdi_pathinfo_t *)MDI_PI(pip)->pi_client_link;
                if (MDI_PI(pip)->pi_phci == ph) {
                        MDI_PI_UNLOCK(pip);
                        pip = next;
                        continue;
                }

                if ((MDI_PI(pip)->pi_state & MDI_PATHINFO_STATE_MASK)
                                == MDI_PATHINFO_STATE_ONLINE)
                        online_count++;
                else if ((MDI_PI(pip)->pi_state & MDI_PATHINFO_STATE_MASK)
                                == MDI_PATHINFO_STATE_STANDBY)
                        standby_count++;
                MDI_PI_UNLOCK(pip);
                pip = next;
        }

        if (online_count == 0) {
                if (standby_count == 0) {
                        state = MDI_CLIENT_STATE_FAILED;
                        MDI_DEBUG(2, (MDI_NOTE, ct->ct_dip,
                            "client state failed: ct = %p", (void *)ct));
                } else if (standby_count == 1) {
                        state = MDI_CLIENT_STATE_DEGRADED;
                } else {
                        state = MDI_CLIENT_STATE_OPTIMAL;
                }
        } else if (online_count == 1) {
                if (standby_count == 0) {
                        state = MDI_CLIENT_STATE_DEGRADED;
                } else {
                        state = MDI_CLIENT_STATE_OPTIMAL;
                }
        } else {
                state = MDI_CLIENT_STATE_OPTIMAL;
        }
        return (state);
}

/*
 * i_mdi_client2devinfo():
 *              Utility function
 */
dev_info_t *
i_mdi_client2devinfo(mdi_client_t *ct)
{
        return (ct->ct_dip);
}

/*
 * mdi_client_path2_devinfo():
 *              Given the parent devinfo and child devfs pathname, search for
 *              a valid devfs node handle.
 */
dev_info_t *
mdi_client_path2devinfo(dev_info_t *vdip, char *pathname)
{
        dev_info_t      *cdip = NULL;
        dev_info_t      *ndip = NULL;
        char            *temp_pathname;
        int             circular;

        /*
         * Allocate temp buffer
         */
        temp_pathname = kmem_zalloc(MAXPATHLEN, KM_SLEEP);

        /*
         * Lock parent against changes
         */
        ndi_devi_enter(vdip, &circular);
        ndip = (dev_info_t *)DEVI(vdip)->devi_child;
        while ((cdip = ndip) != NULL) {
                ndip = (dev_info_t *)DEVI(cdip)->devi_sibling;

                *temp_pathname = '\0';
                (void) ddi_pathname(cdip, temp_pathname);
                if (strcmp(temp_pathname, pathname) == 0) {
                        break;
                }
        }
        /*
         * Release devinfo lock
         */
        ndi_devi_exit(vdip, circular);

        /*
         * Free the temp buffer
         */
        kmem_free(temp_pathname, MAXPATHLEN);
        return (cdip);
}

/*
 * mdi_client_get_path_count():
 *              Utility function to get number of path information nodes
 *              associated with a given client device.
 */
int
mdi_client_get_path_count(dev_info_t *cdip)
{
        mdi_client_t    *ct;
        int             count = 0;

        ct = i_devi_get_client(cdip);
        if (ct != NULL) {
                count = ct->ct_path_count;
        }
        return (count);
}


/*
 * i_mdi_get_hash_key():
 *              Create a hash using strings as keys
 *
 */
static int
i_mdi_get_hash_key(char *str)
{
        uint32_t        g, hash = 0;
        char            *p;

        for (p = str; *p != '\0'; p++) {
                g = *p;
                hash += g;
        }
        return (hash % (CLIENT_HASH_TABLE_SIZE - 1));
}

/*
 * mdi_get_lb_policy():
 *              Get current load balancing policy for a given client device
 */
client_lb_t
mdi_get_lb_policy(dev_info_t *cdip)
{
        client_lb_t     lb = LOAD_BALANCE_NONE;
        mdi_client_t    *ct;

        ct = i_devi_get_client(cdip);
        if (ct != NULL) {
                lb = ct->ct_lb;
        }
        return (lb);
}

/*
 * mdi_set_lb_region_size():
 *              Set current region size for the load-balance
 */
int
mdi_set_lb_region_size(dev_info_t *cdip, int region_size)
{
        mdi_client_t    *ct;
        int             rv = MDI_FAILURE;

        ct = i_devi_get_client(cdip);
        if (ct != NULL && ct->ct_lb_args != NULL) {
                ct->ct_lb_args->region_size = region_size;
                rv = MDI_SUCCESS;
        }
        return (rv);
}

/*
 * mdi_Set_lb_policy():
 *              Set current load balancing policy for a given client device
 */
int
mdi_set_lb_policy(dev_info_t *cdip, client_lb_t lb)
{
        mdi_client_t    *ct;
        int             rv = MDI_FAILURE;

        ct = i_devi_get_client(cdip);
        if (ct != NULL) {
                ct->ct_lb = lb;
                rv = MDI_SUCCESS;
        }
        return (rv);
}

/*
 * mdi_failover():
 *              failover function called by the vHCI drivers to initiate
 *              a failover operation.  This is typically due to non-availability
 *              of online paths to route I/O requests.  Failover can be
 *              triggered through user application also.
 *
 *              The vHCI driver calls mdi_failover() to initiate a failover
 *              operation. mdi_failover() calls back into the vHCI driver's
 *              vo_failover() entry point to perform the actual failover
 *              operation.  The reason for requiring the vHCI driver to
 *              initiate failover by calling mdi_failover(), instead of directly
 *              executing vo_failover() itself, is to ensure that the mdi
 *              framework can keep track of the client state properly.
 *              Additionally, mdi_failover() provides as a convenience the
 *              option of performing the failover operation synchronously or
 *              asynchronously
 *
 *              Upon successful completion of the failover operation, the
 *              paths that were previously ONLINE will be in the STANDBY state,
 *              and the newly activated paths will be in the ONLINE state.
 *
 *              The flags modifier determines whether the activation is done
 *              synchronously: MDI_FAILOVER_SYNC
 * Return Values:
 *              MDI_SUCCESS
 *              MDI_FAILURE
 *              MDI_BUSY
 */
/*ARGSUSED*/
int
mdi_failover(dev_info_t *vdip, dev_info_t *cdip, int flags)
{
        int                     rv;
        mdi_client_t            *ct;

        ct = i_devi_get_client(cdip);
        ASSERT(ct != NULL);
        if (ct == NULL) {
                /* cdip is not a valid client device. Nothing more to do. */
                return (MDI_FAILURE);
        }

        MDI_CLIENT_LOCK(ct);

        if (MDI_CLIENT_IS_PATH_FREE_IN_PROGRESS(ct)) {
                /* A path to the client is being freed */
                MDI_CLIENT_UNLOCK(ct);
                return (MDI_BUSY);
        }


        if (MDI_CLIENT_IS_FAILED(ct)) {
                /*
                 * Client is in failed state. Nothing more to do.
                 */
                MDI_CLIENT_UNLOCK(ct);
                return (MDI_FAILURE);
        }

        if (MDI_CLIENT_IS_FAILOVER_IN_PROGRESS(ct)) {
                /*
                 * Failover is already in progress; return BUSY
                 */
                MDI_CLIENT_UNLOCK(ct);
                return (MDI_BUSY);
        }
        /*
         * Make sure that mdi_pathinfo node state changes are processed.
         * We do not allow failovers to progress while client path state
         * changes are in progress
         */
        if (ct->ct_unstable) {
                if (flags == MDI_FAILOVER_ASYNC) {
                        MDI_CLIENT_UNLOCK(ct);
                        return (MDI_BUSY);
                } else {
                        while (ct->ct_unstable)
                                cv_wait(&ct->ct_unstable_cv, &ct->ct_mutex);
                }
        }

        /*
         * Client device is in stable state. Before proceeding, perform sanity
         * checks again.
         */
        if ((MDI_CLIENT_IS_DETACHED(ct)) || (MDI_CLIENT_IS_FAILED(ct)) ||
            (!i_ddi_devi_attached(cdip))) {
                /*
                 * Client is in failed state. Nothing more to do.
                 */
                MDI_CLIENT_UNLOCK(ct);
                return (MDI_FAILURE);
        }

        /*
         * Set the client state as failover in progress.
         */
        MDI_CLIENT_SET_FAILOVER_IN_PROGRESS(ct);
        ct->ct_failover_flags = flags;
        MDI_CLIENT_UNLOCK(ct);

        if (flags == MDI_FAILOVER_ASYNC) {
                /*
                 * Submit the initiate failover request via CPR safe
                 * taskq threads.
                 */
                (void) taskq_dispatch(mdi_taskq, (task_func_t *)i_mdi_failover,
                    ct, KM_SLEEP);
                return (MDI_ACCEPT);
        } else {
                /*
                 * Synchronous failover mode.  Typically invoked from the user
                 * land.
                 */
                rv = i_mdi_failover(ct);
        }
        return (rv);
}

/*
 * i_mdi_failover():
 *              internal failover function. Invokes vHCI drivers failover
 *              callback function and process the failover status
 * Return Values:
 *              None
 *
 * Note: A client device in failover state can not be detached or freed.
 */
static int
i_mdi_failover(void *arg)
{
        int             rv = MDI_SUCCESS;
        mdi_client_t    *ct = (mdi_client_t *)arg;
        mdi_vhci_t      *vh = ct->ct_vhci;

        ASSERT(!MDI_CLIENT_LOCKED(ct));

        if (vh->vh_ops->vo_failover != NULL) {
                /*
                 * Call vHCI drivers callback routine
                 */
                rv = (*vh->vh_ops->vo_failover)(vh->vh_dip, ct->ct_dip,
                    ct->ct_failover_flags);
        }

        MDI_CLIENT_LOCK(ct);
        MDI_CLIENT_CLEAR_FAILOVER_IN_PROGRESS(ct);

        /*
         * Save the failover return status
         */
        ct->ct_failover_status = rv;

        /*
         * As a result of failover, client status would have been changed.
         * Update the client state and wake up anyone waiting on this client
         * device.
         */
        i_mdi_client_update_state(ct);

        cv_broadcast(&ct->ct_failover_cv);
        MDI_CLIENT_UNLOCK(ct);
        return (rv);
}

/*
 * Load balancing is logical block.
 * IOs within the range described by region_size
 * would go on the same path. This would improve the
 * performance by cache-hit on some of the RAID devices.
 * Search only for online paths(At some point we
 * may want to balance across target ports).
 * If no paths are found then default to round-robin.
 */
static int
i_mdi_lba_lb(mdi_client_t *ct, mdi_pathinfo_t **ret_pip, struct buf *bp)
{
        int             path_index = -1;
        int             online_path_count = 0;
        int             online_nonpref_path_count = 0;
        int             region_size = ct->ct_lb_args->region_size;
        mdi_pathinfo_t  *pip;
        mdi_pathinfo_t  *next;
        int             preferred, path_cnt;

        pip = ct->ct_path_head;
        while (pip) {
                MDI_PI_LOCK(pip);
                if (MDI_PI(pip)->pi_state ==
                    MDI_PATHINFO_STATE_ONLINE && MDI_PI(pip)->pi_preferred) {
                        online_path_count++;
                } else if (MDI_PI(pip)->pi_state ==
                    MDI_PATHINFO_STATE_ONLINE && !MDI_PI(pip)->pi_preferred) {
                        online_nonpref_path_count++;
                }
                next = (mdi_pathinfo_t *)
                    MDI_PI(pip)->pi_client_link;
                MDI_PI_UNLOCK(pip);
                pip = next;
        }
        /* if found any online/preferred then use this type */
        if (online_path_count > 0) {
                path_cnt = online_path_count;
                preferred = 1;
        } else if (online_nonpref_path_count > 0) {
                path_cnt = online_nonpref_path_count;
                preferred = 0;
        } else {
                path_cnt = 0;
        }
        if (path_cnt) {
                path_index = (bp->b_blkno >> region_size) % path_cnt;
                pip = ct->ct_path_head;
                while (pip && path_index != -1) {
                        MDI_PI_LOCK(pip);
                        if (path_index == 0 &&
                            (MDI_PI(pip)->pi_state ==
                            MDI_PATHINFO_STATE_ONLINE) &&
                                MDI_PI(pip)->pi_preferred == preferred) {
                                MDI_PI_HOLD(pip);
                                MDI_PI_UNLOCK(pip);
                                *ret_pip = pip;
                                return (MDI_SUCCESS);
                        }
                        path_index --;
                        next = (mdi_pathinfo_t *)
                            MDI_PI(pip)->pi_client_link;
                        MDI_PI_UNLOCK(pip);
                        pip = next;
                }
                MDI_DEBUG(4, (MDI_NOTE, ct->ct_dip,
                    "lba %llx: path %s %p",
                    bp->b_lblkno, mdi_pi_spathname(pip), (void *)pip));
        }
        return (MDI_FAILURE);
}

/*
 * mdi_select_path():
 *              select a path to access a client device.
 *
 *              mdi_select_path() function is called by the vHCI drivers to
 *              select a path to route the I/O request to.  The caller passes
 *              the block I/O data transfer structure ("buf") as one of the
 *              parameters.  The mpxio framework uses the buf structure
 *              contents to maintain per path statistics (total I/O size /
 *              count pending).  If more than one online paths are available to
 *              select, the framework automatically selects a suitable path
 *              for routing I/O request. If a failover operation is active for
 *              this client device the call shall be failed with MDI_BUSY error
 *              code.
 *
 *              By default this function returns a suitable path in online
 *              state based on the current load balancing policy.  Currently
 *              we support LOAD_BALANCE_NONE (Previously selected online path
 *              will continue to be used till the path is usable) and
 *              LOAD_BALANCE_RR (Online paths will be selected in a round
 *              robin fashion), LOAD_BALANCE_LB(Online paths will be selected
 *              based on the logical block).  The load balancing
 *              through vHCI drivers configuration file (driver.conf).
 *
 *              vHCI drivers may override this default behavior by specifying
 *              appropriate flags.  The meaning of the thrid argument depends
 *              on the flags specified. If MDI_SELECT_PATH_INSTANCE is set
 *              then the argument is the "path instance" of the path to select.
 *              If MDI_SELECT_PATH_INSTANCE is not set then the argument is
 *              "start_pip". A non NULL "start_pip" is the starting point to
 *              walk and find the next appropriate path.  The following values
 *              are currently defined: MDI_SELECT_ONLINE_PATH (to select an
 *              ONLINE path) and/or MDI_SELECT_STANDBY_PATH (to select an
 *              STANDBY path).
 *
 *              The non-standard behavior is used by the scsi_vhci driver,
 *              whenever it has to use a STANDBY/FAULTED path.  Eg. during
 *              attach of client devices (to avoid an unnecessary failover
 *              when the STANDBY path comes up first), during failover
 *              (to activate a STANDBY path as ONLINE).
 *
 *              The selected path is returned in a a mdi_hold_path() state
 *              (pi_ref_cnt). Caller should release the hold by calling
 *              mdi_rele_path().
 *
 * Return Values:
 *              MDI_SUCCESS     - Completed successfully
 *              MDI_BUSY        - Client device is busy failing over
 *              MDI_NOPATH      - Client device is online, but no valid path are
 *                                available to access this client device
 *              MDI_FAILURE     - Invalid client device or state
 *              MDI_DEVI_ONLINING
 *                              - Client device (struct dev_info state) is in
 *                                onlining state.
 */

/*ARGSUSED*/
int
mdi_select_path(dev_info_t *cdip, struct buf *bp, int flags,
    void *arg, mdi_pathinfo_t **ret_pip)
{
        mdi_client_t    *ct;
        mdi_pathinfo_t  *pip;
        mdi_pathinfo_t  *next;
        mdi_pathinfo_t  *head;
        mdi_pathinfo_t  *start;
        client_lb_t     lbp;    /* load balancing policy */
        int             sb = 1; /* standard behavior */
        int             preferred = 1;  /* preferred path */
        int             cond, cont = 1;
        int             retry = 0;
        mdi_pathinfo_t  *start_pip;     /* request starting pathinfo */
        int             path_instance;  /* request specific path instance */

        /* determine type of arg based on flags */
        if (flags & MDI_SELECT_PATH_INSTANCE) {
                path_instance = (int)(intptr_t)arg;
                start_pip = NULL;
        } else {
                path_instance = 0;
                start_pip = (mdi_pathinfo_t *)arg;
        }

        if (flags != 0) {
                /*
                 * disable default behavior
                 */
                sb = 0;
        }

        *ret_pip = NULL;
        ct = i_devi_get_client(cdip);
        if (ct == NULL) {
                /* mdi extensions are NULL, Nothing more to do */
                return (MDI_FAILURE);
        }

        MDI_CLIENT_LOCK(ct);

        if (sb) {
                if (MDI_CLIENT_IS_FAILED(ct)) {
                        /*
                         * Client is not ready to accept any I/O requests.
                         * Fail this request.
                         */
                        MDI_DEBUG(2, (MDI_NOTE, cdip,
                            "client state offline ct = %p", (void *)ct));
                        MDI_CLIENT_UNLOCK(ct);
                        return (MDI_FAILURE);
                }

                if (MDI_CLIENT_IS_FAILOVER_IN_PROGRESS(ct)) {
                        /*
                         * Check for Failover is in progress. If so tell the
                         * caller that this device is busy.
                         */
                        MDI_DEBUG(2, (MDI_NOTE, cdip,
                            "client failover in progress ct = %p",
                            (void *)ct));
                        MDI_CLIENT_UNLOCK(ct);
                        return (MDI_BUSY);
                }

                /*
                 * Check to see whether the client device is attached.
                 * If not so, let the vHCI driver manually select a path
                 * (standby) and let the probe/attach process to continue.
                 */
                if (MDI_CLIENT_IS_DETACHED(ct) || !i_ddi_devi_attached(cdip)) {
                        MDI_DEBUG(4, (MDI_NOTE, cdip,
                            "devi is onlining ct = %p", (void *)ct));
                        MDI_CLIENT_UNLOCK(ct);
                        return (MDI_DEVI_ONLINING);
                }
        }

        /*
         * Cache in the client list head.  If head of the list is NULL
         * return MDI_NOPATH
         */
        head = ct->ct_path_head;
        if (head == NULL) {
                MDI_CLIENT_UNLOCK(ct);
                return (MDI_NOPATH);
        }

        /* Caller is specifying a specific pathinfo path by path_instance */
        if (path_instance) {
                /* search for pathinfo with correct path_instance */
                for (pip = head;
                    pip && (mdi_pi_get_path_instance(pip) != path_instance);
                    pip = (mdi_pathinfo_t *)MDI_PI(pip)->pi_client_link)
                        ;

                /* If path can't be selected then MDI_NOPATH is returned. */
                if (pip == NULL) {
                        MDI_CLIENT_UNLOCK(ct);
                        return (MDI_NOPATH);
                }

                /*
                 * Verify state of path. When asked to select a specific
                 * path_instance, we select the requested path in any
                 * state (ONLINE, OFFLINE, STANDBY, FAULT) other than INIT.
                 * We don't however select paths where the pHCI has detached.
                 * NOTE: last pathinfo node of an opened client device may
                 * exist in an OFFLINE state after the pHCI associated with
                 * that path has detached (but pi_phci will be NULL if that
                 * has occurred).
                 */
                MDI_PI_LOCK(pip);
                if ((MDI_PI(pip)->pi_state == MDI_PATHINFO_STATE_INIT) ||
                    (MDI_PI(pip)->pi_phci == NULL)) {
                        MDI_PI_UNLOCK(pip);
                        MDI_CLIENT_UNLOCK(ct);
                        return (MDI_FAILURE);
                }

                /* Return MDI_BUSY if we have a transient condition */
                if (MDI_PI_IS_TRANSIENT(pip)) {
                        MDI_PI_UNLOCK(pip);
                        MDI_CLIENT_UNLOCK(ct);
                        return (MDI_BUSY);
                }

                /*
                 * Return the path in hold state. Caller should release the
                 * lock by calling mdi_rele_path()
                 */
                MDI_PI_HOLD(pip);
                MDI_PI_UNLOCK(pip);
                *ret_pip = pip;
                MDI_CLIENT_UNLOCK(ct);
                return (MDI_SUCCESS);
        }

        /*
         * for non default behavior, bypass current
         * load balancing policy and always use LOAD_BALANCE_RR
         * except that the start point will be adjusted based
         * on the provided start_pip
         */
        lbp = sb ? ct->ct_lb : LOAD_BALANCE_RR;

        switch (lbp) {
        case LOAD_BALANCE_NONE:
                /*
                 * Load balancing is None  or Alternate path mode
                 * Start looking for a online mdi_pathinfo node starting from
                 * last known selected path
                 */
                preferred = 1;
                pip = (mdi_pathinfo_t *)ct->ct_path_last;
                if (pip == NULL) {
                        pip = head;
                }
                start = pip;
                do {
                        MDI_PI_LOCK(pip);
                        /*
                         * No need to explicitly check if the path is disabled.
                         * Since we are checking for state == ONLINE and the
                         * same variable is used for DISABLE/ENABLE information.
                         */
                        if ((MDI_PI(pip)->pi_state  ==
                                MDI_PATHINFO_STATE_ONLINE) &&
                                preferred == MDI_PI(pip)->pi_preferred) {
                                /*
                                 * Return the path in hold state. Caller should
                                 * release the lock by calling mdi_rele_path()
                                 */
                                MDI_PI_HOLD(pip);
                                MDI_PI_UNLOCK(pip);
                                ct->ct_path_last = pip;
                                *ret_pip = pip;
                                MDI_CLIENT_UNLOCK(ct);
                                return (MDI_SUCCESS);
                        }

                        /*
                         * Path is busy.
                         */
                        if (MDI_PI_IS_DRV_DISABLE_TRANSIENT(pip) ||
                            MDI_PI_IS_TRANSIENT(pip))
                                retry = 1;
                        /*
                         * Keep looking for a next available online path
                         */
                        next = (mdi_pathinfo_t *)MDI_PI(pip)->pi_client_link;
                        if (next == NULL) {
                                next = head;
                        }
                        MDI_PI_UNLOCK(pip);
                        pip = next;
                        if (start == pip && preferred) {
                                preferred = 0;
                        } else if (start == pip && !preferred) {
                                cont = 0;
                        }
                } while (cont);
                break;

        case LOAD_BALANCE_LBA:
                /*
                 * Make sure we are looking
                 * for an online path. Otherwise, if it is for a STANDBY
                 * path request, it will go through and fetch an ONLINE
                 * path which is not desirable.
                 */
                if ((ct->ct_lb_args != NULL) &&
                            (ct->ct_lb_args->region_size) && bp &&
                                (sb || (flags == MDI_SELECT_ONLINE_PATH))) {
                        if (i_mdi_lba_lb(ct, ret_pip, bp)
                                    == MDI_SUCCESS) {
                                MDI_CLIENT_UNLOCK(ct);
                                return (MDI_SUCCESS);
                        }
                }
                /* FALLTHROUGH */
        case LOAD_BALANCE_RR:
                /*
                 * Load balancing is Round Robin. Start looking for a online
                 * mdi_pathinfo node starting from last known selected path
                 * as the start point.  If override flags are specified,
                 * process accordingly.
                 * If the search is already in effect(start_pip not null),
                 * then lets just use the same path preference to continue the
                 * traversal.
                 */

                if (start_pip != NULL) {
                        preferred = MDI_PI(start_pip)->pi_preferred;
                } else {
                        preferred = 1;
                }

                start = sb ? (mdi_pathinfo_t *)ct->ct_path_last : start_pip;
                if (start == NULL) {
                        pip = head;
                } else {
                        pip = (mdi_pathinfo_t *)MDI_PI(start)->pi_client_link;
                        if (pip == NULL) {
                                if ( flags & MDI_SELECT_NO_PREFERRED) {
                                        /*
                                         * Return since we hit the end of list
                                         */
                                        MDI_CLIENT_UNLOCK(ct);
                                        return (MDI_NOPATH);
                                }

                                if (!sb) {
                                        if (preferred == 0) {
                                                /*
                                                 * Looks like we have completed
                                                 * the traversal as preferred
                                                 * value is 0. Time to bail out.
                                                 */
                                                *ret_pip = NULL;
                                                MDI_CLIENT_UNLOCK(ct);
                                                return (MDI_NOPATH);
                                        } else {
                                                /*
                                                 * Looks like we reached the
                                                 * end of the list. Lets enable
                                                 * traversal of non preferred
                                                 * paths.
                                                 */
                                                preferred = 0;
                                        }
                                }
                                pip = head;
                        }
                }
                start = pip;
                do {
                        MDI_PI_LOCK(pip);
                        if (sb) {
                                cond = ((MDI_PI(pip)->pi_state ==
                                    MDI_PATHINFO_STATE_ONLINE &&
                                        MDI_PI(pip)->pi_preferred ==
                                                preferred) ? 1 : 0);
                        } else {
                                if (flags == MDI_SELECT_ONLINE_PATH) {
                                        cond = ((MDI_PI(pip)->pi_state ==
                                            MDI_PATHINFO_STATE_ONLINE &&
                                                MDI_PI(pip)->pi_preferred ==
                                                preferred) ? 1 : 0);
                                } else if (flags == MDI_SELECT_STANDBY_PATH) {
                                        cond = ((MDI_PI(pip)->pi_state ==
                                            MDI_PATHINFO_STATE_STANDBY &&
                                                MDI_PI(pip)->pi_preferred ==
                                                preferred) ? 1 : 0);
                                } else if (flags == (MDI_SELECT_ONLINE_PATH |
                                    MDI_SELECT_STANDBY_PATH)) {
                                        cond = (((MDI_PI(pip)->pi_state ==
                                            MDI_PATHINFO_STATE_ONLINE ||
                                            (MDI_PI(pip)->pi_state ==
                                            MDI_PATHINFO_STATE_STANDBY)) &&
                                                MDI_PI(pip)->pi_preferred ==
                                                preferred) ? 1 : 0);
                                } else if (flags ==
                                        (MDI_SELECT_STANDBY_PATH |
                                        MDI_SELECT_ONLINE_PATH |
                                        MDI_SELECT_USER_DISABLE_PATH)) {
                                        cond = (((MDI_PI(pip)->pi_state ==
                                            MDI_PATHINFO_STATE_ONLINE ||
                                            (MDI_PI(pip)->pi_state ==
                                            MDI_PATHINFO_STATE_STANDBY) ||
                                                (MDI_PI(pip)->pi_state ==
                                            (MDI_PATHINFO_STATE_ONLINE|
                                            MDI_PATHINFO_STATE_USER_DISABLE)) ||
                                                (MDI_PI(pip)->pi_state ==
                                            (MDI_PATHINFO_STATE_STANDBY |
                                            MDI_PATHINFO_STATE_USER_DISABLE)))&&
                                                MDI_PI(pip)->pi_preferred ==
                                                preferred) ? 1 : 0);
                                } else if (flags ==
                                    (MDI_SELECT_STANDBY_PATH |
                                    MDI_SELECT_ONLINE_PATH |
                                    MDI_SELECT_NO_PREFERRED)) {
                                        cond = (((MDI_PI(pip)->pi_state ==
                                            MDI_PATHINFO_STATE_ONLINE) ||
                                            (MDI_PI(pip)->pi_state ==
                                            MDI_PATHINFO_STATE_STANDBY))
                                            ? 1 : 0);
                                } else {
                                        cond = 0;
                                }
                        }
                        /*
                         * No need to explicitly check if the path is disabled.
                         * Since we are checking for state == ONLINE and the
                         * same variable is used for DISABLE/ENABLE information.
                         */
                        if (cond) {
                                /*
                                 * Return the path in hold state. Caller should
                                 * release the lock by calling mdi_rele_path()
                                 */
                                MDI_PI_HOLD(pip);
                                MDI_PI_UNLOCK(pip);
                                if (sb)
                                        ct->ct_path_last = pip;
                                *ret_pip = pip;
                                MDI_CLIENT_UNLOCK(ct);
                                return (MDI_SUCCESS);
                        }
                        /*
                         * Path is busy.
                         */
                        if (MDI_PI_IS_DRV_DISABLE_TRANSIENT(pip) ||
                            MDI_PI_IS_TRANSIENT(pip))
                                retry = 1;

                        /*
                         * Keep looking for a next available online path
                         */
do_again:
                        next = (mdi_pathinfo_t *)MDI_PI(pip)->pi_client_link;
                        if (next == NULL) {
                                if ( flags & MDI_SELECT_NO_PREFERRED) {
                                        /*
                                         * Bail out since we hit the end of list
                                         */
                                        MDI_PI_UNLOCK(pip);
                                        break;
                                }

                                if (!sb) {
                                        if (preferred == 1) {
                                                /*
                                                 * Looks like we reached the
                                                 * end of the list. Lets enable
                                                 * traversal of non preferred
                                                 * paths.
                                                 */
                                                preferred = 0;
                                                next = head;
                                        } else {
                                                /*
                                                 * We have done both the passes
                                                 * Preferred as well as for
                                                 * Non-preferred. Bail out now.
                                                 */
                                                cont = 0;
                                        }
                                } else {
                                        /*
                                         * Standard behavior case.
                                         */
                                        next = head;
                                }
                        }
                        MDI_PI_UNLOCK(pip);
                        if (cont == 0) {
                                break;
                        }
                        pip = next;

                        if (!sb) {
                                /*
                                 * We need to handle the selection of
                                 * non-preferred path in the following
                                 * case:
                                 *
                                 * +------+   +------+   +------+   +-----+
                                 * | A : 1| - | B : 1| - | C : 0| - |NULL |
                                 * +------+   +------+   +------+   +-----+
                                 *
                                 * If we start the search with B, we need to
                                 * skip beyond B to pick C which is non -
                                 * preferred in the second pass. The following
                                 * test, if true, will allow us to skip over
                                 * the 'start'(B in the example) to select
                                 * other non preferred elements.
                                 */
                                if ((start_pip != NULL) && (start_pip == pip) &&
                                    (MDI_PI(start_pip)->pi_preferred
                                    != preferred)) {
                                        /*
                                         * try again after going past the start
                                         * pip
                                         */
                                        MDI_PI_LOCK(pip);
                                        goto do_again;
                                }
                        } else {
                                /*
                                 * Standard behavior case
                                 */
                                if (start == pip && preferred) {
                                        /* look for nonpreferred paths */
                                        preferred = 0;
                                } else if (start == pip && !preferred) {
                                        /*
                                         * Exit condition
                                         */
                                        cont = 0;
                                }
                        }
                } while (cont);
                break;
        }

        MDI_CLIENT_UNLOCK(ct);
        if (retry == 1) {
                return (MDI_BUSY);
        } else {
                return (MDI_NOPATH);
        }
}

/*
 * For a client, return the next available path to any phci
 *
 * Note:
 *              Caller should hold the branch's devinfo node to get a consistent
 *              snap shot of the mdi_pathinfo nodes.
 *
 *              Please note that even the list is stable the mdi_pathinfo
 *              node state and properties are volatile.  The caller should lock
 *              and unlock the nodes by calling mdi_pi_lock() and
 *              mdi_pi_unlock() functions to get a stable properties.
 *
 *              If there is a need to use the nodes beyond the hold of the
 *              devinfo node period (For ex. I/O), then mdi_pathinfo node
 *              need to be held against unexpected removal by calling
 *              mdi_hold_path() and should be released by calling
 *              mdi_rele_path() on completion.
 */
mdi_pathinfo_t *
mdi_get_next_phci_path(dev_info_t *ct_dip, mdi_pathinfo_t *pip)
{
        mdi_client_t *ct;

        if (!MDI_CLIENT(ct_dip))
                return (NULL);

        /*
         * Walk through client link
         */
        ct = (mdi_client_t *)DEVI(ct_dip)->devi_mdi_client;
        ASSERT(ct != NULL);

        if (pip == NULL)
                return ((mdi_pathinfo_t *)ct->ct_path_head);

        return ((mdi_pathinfo_t *)MDI_PI(pip)->pi_client_link);
}

/*
 * For a phci, return the next available path to any client
 * Note: ditto mdi_get_next_phci_path()
 */
mdi_pathinfo_t *
mdi_get_next_client_path(dev_info_t *ph_dip, mdi_pathinfo_t *pip)
{
        mdi_phci_t *ph;

        if (!MDI_PHCI(ph_dip))
                return (NULL);

        /*
         * Walk through pHCI link
         */
        ph = (mdi_phci_t *)DEVI(ph_dip)->devi_mdi_xhci;
        ASSERT(ph != NULL);

        if (pip == NULL)
                return ((mdi_pathinfo_t *)ph->ph_path_head);

        return ((mdi_pathinfo_t *)MDI_PI(pip)->pi_phci_link);
}

/*
 * mdi_hold_path():
 *              Hold the mdi_pathinfo node against unwanted unexpected free.
 * Return Values:
 *              None
 */
void
mdi_hold_path(mdi_pathinfo_t *pip)
{
        if (pip) {
                MDI_PI_LOCK(pip);
                MDI_PI_HOLD(pip);
                MDI_PI_UNLOCK(pip);
        }
}


/*
 * mdi_rele_path():
 *              Release the mdi_pathinfo node which was selected
 *              through mdi_select_path() mechanism or manually held by
 *              calling mdi_hold_path().
 * Return Values:
 *              None
 */
void
mdi_rele_path(mdi_pathinfo_t *pip)
{
        if (pip) {
                MDI_PI_LOCK(pip);
                MDI_PI_RELE(pip);
                if (MDI_PI(pip)->pi_ref_cnt == 0) {
                        cv_broadcast(&MDI_PI(pip)->pi_ref_cv);
                }
                MDI_PI_UNLOCK(pip);
        }
}

/*
 * mdi_pi_lock():
 *              Lock the mdi_pathinfo node.
 * Note:
 *              The caller should release the lock by calling mdi_pi_unlock()
 */
void
mdi_pi_lock(mdi_pathinfo_t *pip)
{
        ASSERT(pip != NULL);
        if (pip) {
                MDI_PI_LOCK(pip);
        }
}


/*
 * mdi_pi_unlock():
 *              Unlock the mdi_pathinfo node.
 * Note:
 *              The mdi_pathinfo node should have been locked with mdi_pi_lock()
 */
void
mdi_pi_unlock(mdi_pathinfo_t *pip)
{
        ASSERT(pip != NULL);
        if (pip) {
                MDI_PI_UNLOCK(pip);
        }
}

/*
 * mdi_pi_find():
 *              Search the list of mdi_pathinfo nodes attached to the
 *              pHCI/Client device node whose path address matches "paddr".
 *              Returns a pointer to the mdi_pathinfo node if a matching node is
 *              found.
 * Return Values:
 *              mdi_pathinfo node handle
 *              NULL
 * Notes:
 *              Caller need not hold any locks to call this function.
 */
mdi_pathinfo_t *
mdi_pi_find(dev_info_t *pdip, char *caddr, char *paddr)
{
        mdi_phci_t              *ph;
        mdi_vhci_t              *vh;
        mdi_client_t            *ct;
        mdi_pathinfo_t          *pip = NULL;

        MDI_DEBUG(2, (MDI_NOTE, pdip,
            "caddr@%s paddr@%s", caddr ? caddr : "", paddr ? paddr : ""));
        if ((pdip == NULL) || (paddr == NULL)) {
                return (NULL);
        }
        ph = i_devi_get_phci(pdip);
        if (ph == NULL) {
                /*
                 * Invalid pHCI device, Nothing more to do.
                 */
                MDI_DEBUG(2, (MDI_WARN, pdip, "invalid phci"));
                return (NULL);
        }

        vh = ph->ph_vhci;
        if (vh == NULL) {
                /*
                 * Invalid vHCI device, Nothing more to do.
                 */
                MDI_DEBUG(2, (MDI_WARN, pdip, "invalid vhci"));
                return (NULL);
        }

        /*
         * Look for pathinfo node identified by paddr.
         */
        if (caddr == NULL) {
                /*
                 * Find a mdi_pathinfo node under pHCI list for a matching
                 * unit address.
                 */
                MDI_PHCI_LOCK(ph);
                if (MDI_PHCI_IS_OFFLINE(ph)) {
                        MDI_DEBUG(2, (MDI_WARN, pdip,
                            "offline phci %p", (void *)ph));
                        MDI_PHCI_UNLOCK(ph);
                        return (NULL);
                }
                pip = (mdi_pathinfo_t *)ph->ph_path_head;

                while (pip != NULL) {
                        if (strcmp(MDI_PI(pip)->pi_addr, paddr) == 0) {
                                break;
                        }
                        pip = (mdi_pathinfo_t *)MDI_PI(pip)->pi_phci_link;
                }
                MDI_PHCI_UNLOCK(ph);
                MDI_DEBUG(2, (MDI_NOTE, pdip,
                    "found %s %p", mdi_pi_spathname(pip), (void *)pip));
                return (pip);
        }

        /*
         * XXX - Is the rest of the code in this function really necessary?
         * The consumers of mdi_pi_find() can search for the desired pathinfo
         * node by calling mdi_pi_find(pdip, NULL, paddr). Irrespective of
         * whether the search is based on the pathinfo nodes attached to
         * the pHCI or the client node, the result will be the same.
         */

        /*
         * Find the client device corresponding to 'caddr'
         */
        MDI_VHCI_CLIENT_LOCK(vh);

        /*
         * XXX - Passing NULL to the following function works as long as the
         * the client addresses (caddr) are unique per vhci basis.
         */
        ct = i_mdi_client_find(vh, NULL, caddr);
        if (ct == NULL) {
                /*
                 * Client not found, Obviously mdi_pathinfo node has not been
                 * created yet.
                 */
                MDI_VHCI_CLIENT_UNLOCK(vh);
                MDI_DEBUG(2, (MDI_NOTE, pdip,
                    "client not found for caddr @%s", caddr ? caddr : ""));
                return (NULL);
        }

        /*
         * Hold the client lock and look for a mdi_pathinfo node with matching
         * pHCI and paddr
         */
        MDI_CLIENT_LOCK(ct);

        /*
         * Release the global mutex as it is no more needed. Note: We always
         * respect the locking order while acquiring.
         */
        MDI_VHCI_CLIENT_UNLOCK(vh);

        pip = (mdi_pathinfo_t *)ct->ct_path_head;
        while (pip != NULL) {
                /*
                 * Compare the unit address
                 */
                if ((MDI_PI(pip)->pi_phci == ph) &&
                    strcmp(MDI_PI(pip)->pi_addr, paddr) == 0) {
                        break;
                }
                pip = (mdi_pathinfo_t *)MDI_PI(pip)->pi_client_link;
        }
        MDI_CLIENT_UNLOCK(ct);
        MDI_DEBUG(2, (MDI_NOTE, pdip,
            "found: %s %p", mdi_pi_spathname(pip), (void *)pip));
        return (pip);
}

/*
 * mdi_pi_alloc():
 *              Allocate and initialize a new instance of a mdi_pathinfo node.
 *              The mdi_pathinfo node returned by this function identifies a
 *              unique device path is capable of having properties attached
 *              and passed to mdi_pi_online() to fully attach and online the
 *              path and client device node.
 *              The mdi_pathinfo node returned by this function must be
 *              destroyed using mdi_pi_free() if the path is no longer
 *              operational or if the caller fails to attach a client device
 *              node when calling mdi_pi_online(). The framework will not free
 *              the resources allocated.
 *              This function can be called from both interrupt and kernel
 *              contexts.  DDI_NOSLEEP flag should be used while calling
 *              from interrupt contexts.
 * Return Values:
 *              MDI_SUCCESS
 *              MDI_FAILURE
 *              MDI_NOMEM
 */
/*ARGSUSED*/
int
mdi_pi_alloc_compatible(dev_info_t *pdip, char *cname, char *caddr, char *paddr,
    char **compatible, int ncompatible, int flags, mdi_pathinfo_t **ret_pip)
{
        mdi_vhci_t      *vh;
        mdi_phci_t      *ph;
        mdi_client_t    *ct;
        mdi_pathinfo_t  *pip = NULL;
        dev_info_t      *cdip;
        int             rv = MDI_NOMEM;
        int             path_allocated = 0;

        MDI_DEBUG(2, (MDI_NOTE, pdip,
            "cname %s: caddr@%s paddr@%s",
            cname ? cname : "", caddr ? caddr : "", paddr ? paddr : ""));

        if (pdip == NULL || cname == NULL || caddr == NULL || paddr == NULL ||
            ret_pip == NULL) {
                /* Nothing more to do */
                return (MDI_FAILURE);
        }

        *ret_pip = NULL;

        /* No allocations on detaching pHCI */
        if (DEVI_IS_DETACHING(pdip)) {
                /* Invalid pHCI device, return failure */
                MDI_DEBUG(1, (MDI_WARN, pdip,
                    "!detaching pHCI=%p", (void *)pdip));
                return (MDI_FAILURE);
        }

        ph = i_devi_get_phci(pdip);
        ASSERT(ph != NULL);
        if (ph == NULL) {
                /* Invalid pHCI device, return failure */
                MDI_DEBUG(1, (MDI_WARN, pdip,
                    "!invalid pHCI=%p", (void *)pdip));
                return (MDI_FAILURE);
        }

        MDI_PHCI_LOCK(ph);
        vh = ph->ph_vhci;
        if (vh == NULL) {
                /* Invalid vHCI device, return failure */
                MDI_DEBUG(1, (MDI_WARN, pdip,
                    "!invalid vHCI=%p", (void *)pdip));
                MDI_PHCI_UNLOCK(ph);
                return (MDI_FAILURE);
        }

        if (MDI_PHCI_IS_READY(ph) == 0) {
                /*
                 * Do not allow new node creation when pHCI is in
                 * offline/suspended states
                 */
                MDI_DEBUG(1, (MDI_WARN, pdip,
                    "pHCI=%p is not ready", (void *)ph));
                MDI_PHCI_UNLOCK(ph);
                return (MDI_BUSY);
        }
        MDI_PHCI_UNSTABLE(ph);
        MDI_PHCI_UNLOCK(ph);

        /* look for a matching client, create one if not found */
        MDI_VHCI_CLIENT_LOCK(vh);
        ct = i_mdi_client_find(vh, cname, caddr);
        if (ct == NULL) {
                ct = i_mdi_client_alloc(vh, cname, caddr);
                ASSERT(ct != NULL);
        }

        if (ct->ct_dip == NULL) {
                /*
                 * Allocate a devinfo node
                 */
                ct->ct_dip = i_mdi_devinfo_create(vh, cname, caddr,
                    compatible, ncompatible);
                if (ct->ct_dip == NULL) {
                        (void) i_mdi_client_free(vh, ct);
                        goto fail;
                }
        }
        cdip = ct->ct_dip;

        DEVI(cdip)->devi_mdi_component |= MDI_COMPONENT_CLIENT;
        DEVI(cdip)->devi_mdi_client = (caddr_t)ct;

        MDI_CLIENT_LOCK(ct);
        pip = (mdi_pathinfo_t *)ct->ct_path_head;
        while (pip != NULL) {
                /*
                 * Compare the unit address
                 */
                if ((MDI_PI(pip)->pi_phci == ph) &&
                    strcmp(MDI_PI(pip)->pi_addr, paddr) == 0) {
                        break;
                }
                pip = (mdi_pathinfo_t *)MDI_PI(pip)->pi_client_link;
        }
        MDI_CLIENT_UNLOCK(ct);

        if (pip == NULL) {
                /*
                 * This is a new path for this client device.  Allocate and
                 * initialize a new pathinfo node
                 */
                pip = i_mdi_pi_alloc(ph, paddr, ct);
                ASSERT(pip != NULL);
                path_allocated = 1;
        }
        rv = MDI_SUCCESS;

fail:
        /*
         * Release the global mutex.
         */
        MDI_VHCI_CLIENT_UNLOCK(vh);

        /*
         * Mark the pHCI as stable
         */
        MDI_PHCI_LOCK(ph);
        MDI_PHCI_STABLE(ph);
        MDI_PHCI_UNLOCK(ph);
        *ret_pip = pip;

        MDI_DEBUG(2, (MDI_NOTE, pdip,
            "alloc %s %p", mdi_pi_spathname(pip), (void *)pip));

        if (path_allocated)
                vhcache_pi_add(vh->vh_config, MDI_PI(pip));

        return (rv);
}

/*ARGSUSED*/
int
mdi_pi_alloc(dev_info_t *pdip, char *cname, char *caddr, char *paddr,
    int flags, mdi_pathinfo_t **ret_pip)
{
        return (mdi_pi_alloc_compatible(pdip, cname, caddr, paddr, NULL, 0,
            flags, ret_pip));
}

/*
 * i_mdi_pi_alloc():
 *              Allocate a mdi_pathinfo node and add to the pHCI path list
 * Return Values:
 *              mdi_pathinfo
 */
/*ARGSUSED*/
static mdi_pathinfo_t *
i_mdi_pi_alloc(mdi_phci_t *ph, char *paddr, mdi_client_t *ct)
{
        mdi_pathinfo_t  *pip;
        int             ct_circular;
        int             ph_circular;
        static char     path[MAXPATHLEN];       /* mdi_pathmap_mutex protects */
        char            *path_persistent;
        int             path_instance;
        mod_hash_val_t  hv;

        ASSERT(MDI_VHCI_CLIENT_LOCKED(ph->ph_vhci));

        pip = kmem_zalloc(sizeof (struct mdi_pathinfo), KM_SLEEP);
        mutex_init(&MDI_PI(pip)->pi_mutex, NULL, MUTEX_DEFAULT, NULL);
        MDI_PI(pip)->pi_state = MDI_PATHINFO_STATE_INIT |
            MDI_PATHINFO_STATE_TRANSIENT;

        if (MDI_PHCI_IS_USER_DISABLED(ph))
                MDI_PI_SET_USER_DISABLE(pip);

        if (MDI_PHCI_IS_DRV_DISABLED_TRANSIENT(ph))
                MDI_PI_SET_DRV_DISABLE_TRANS(pip);

        if (MDI_PHCI_IS_DRV_DISABLED(ph))
                MDI_PI_SET_DRV_DISABLE(pip);

        MDI_PI(pip)->pi_old_state = MDI_PATHINFO_STATE_INIT;
        cv_init(&MDI_PI(pip)->pi_state_cv, NULL, CV_DEFAULT, NULL);
        MDI_PI(pip)->pi_client = ct;
        MDI_PI(pip)->pi_phci = ph;
        MDI_PI(pip)->pi_addr = kmem_alloc(strlen(paddr) + 1, KM_SLEEP);
        (void) strcpy(MDI_PI(pip)->pi_addr, paddr);

        /*
         * We form the "path" to the pathinfo node, and see if we have
         * already allocated a 'path_instance' for that "path".  If so,
         * we use the already allocated 'path_instance'.  If not, we
         * allocate a new 'path_instance' and associate it with a copy of
         * the "path" string (which is never freed). The association
         * between a 'path_instance' this "path" string persists until
         * reboot.
         */
        mutex_enter(&mdi_pathmap_mutex);
        (void) ddi_pathname(ph->ph_dip, path);
        (void) sprintf(path + strlen(path), "/%s@%s",
            mdi_pi_get_node_name(pip), mdi_pi_get_addr(pip));
        if (mod_hash_find(mdi_pathmap_bypath, (mod_hash_key_t)path, &hv) == 0) {
                path_instance = (uint_t)(intptr_t)hv;
        } else {
                /* allocate a new 'path_instance' and persistent "path" */
                path_instance = mdi_pathmap_instance++;
                path_persistent = i_ddi_strdup(path, KM_SLEEP);
                (void) mod_hash_insert(mdi_pathmap_bypath,
                    (mod_hash_key_t)path_persistent,
                    (mod_hash_val_t)(intptr_t)path_instance);
                (void) mod_hash_insert(mdi_pathmap_byinstance,
                    (mod_hash_key_t)(intptr_t)path_instance,
                    (mod_hash_val_t)path_persistent);

                /* create shortpath name */
                (void) snprintf(path, sizeof(path), "%s%d/%s@%s",
                    ddi_driver_name(ph->ph_dip), ddi_get_instance(ph->ph_dip),
                    mdi_pi_get_node_name(pip), mdi_pi_get_addr(pip));
                path_persistent = i_ddi_strdup(path, KM_SLEEP);
                (void) mod_hash_insert(mdi_pathmap_sbyinstance,
                    (mod_hash_key_t)(intptr_t)path_instance,
                    (mod_hash_val_t)path_persistent);
        }
        mutex_exit(&mdi_pathmap_mutex);
        MDI_PI(pip)->pi_path_instance = path_instance;

        (void) nvlist_alloc(&MDI_PI(pip)->pi_prop, NV_UNIQUE_NAME, KM_SLEEP);
        ASSERT(MDI_PI(pip)->pi_prop != NULL);
        MDI_PI(pip)->pi_pprivate = NULL;
        MDI_PI(pip)->pi_cprivate = NULL;
        MDI_PI(pip)->pi_vprivate = NULL;
        MDI_PI(pip)->pi_client_link = NULL;
        MDI_PI(pip)->pi_phci_link = NULL;
        MDI_PI(pip)->pi_ref_cnt = 0;
        MDI_PI(pip)->pi_kstats = NULL;
        MDI_PI(pip)->pi_preferred = 1;
        cv_init(&MDI_PI(pip)->pi_ref_cv, NULL, CV_DEFAULT, NULL);

        /*
         * Lock both dev_info nodes against changes in parallel.
         *
         * The ndi_devi_enter(Client), is atypical since the client is a leaf.
         * This atypical operation is done to synchronize pathinfo nodes
         * during devinfo snapshot (see di_register_pip) by 'pretending' that
         * the pathinfo nodes are children of the Client.
         */
        ndi_devi_enter(ct->ct_dip, &ct_circular);
        ndi_devi_enter(ph->ph_dip, &ph_circular);

        i_mdi_phci_add_path(ph, pip);
        i_mdi_client_add_path(ct, pip);

        ndi_devi_exit(ph->ph_dip, ph_circular);
        ndi_devi_exit(ct->ct_dip, ct_circular);

        return (pip);
}

/*
 * mdi_pi_pathname_by_instance():
 *      Lookup of "path" by 'path_instance'. Return "path".
 *      NOTE: returned "path" remains valid forever (until reboot).
 */
char *
mdi_pi_pathname_by_instance(int path_instance)
{
        char            *path;
        mod_hash_val_t  hv;

        /* mdi_pathmap lookup of "path" by 'path_instance' */
        mutex_enter(&mdi_pathmap_mutex);
        if (mod_hash_find(mdi_pathmap_byinstance,
            (mod_hash_key_t)(intptr_t)path_instance, &hv) == 0)
                path = (char *)hv;
        else
                path = NULL;
        mutex_exit(&mdi_pathmap_mutex);
        return (path);
}

/*
 * mdi_pi_spathname_by_instance():
 *      Lookup of "shortpath" by 'path_instance'. Return "shortpath".
 *      NOTE: returned "shortpath" remains valid forever (until reboot).
 */
char *
mdi_pi_spathname_by_instance(int path_instance)
{
        char            *path;
        mod_hash_val_t  hv;

        /* mdi_pathmap lookup of "path" by 'path_instance' */
        mutex_enter(&mdi_pathmap_mutex);
        if (mod_hash_find(mdi_pathmap_sbyinstance,
            (mod_hash_key_t)(intptr_t)path_instance, &hv) == 0)
                path = (char *)hv;
        else
                path = NULL;
        mutex_exit(&mdi_pathmap_mutex);
        return (path);
}


/*
 * i_mdi_phci_add_path():
 *              Add a mdi_pathinfo node to pHCI list.
 * Notes:
 *              Caller should per-pHCI mutex
 */
static void
i_mdi_phci_add_path(mdi_phci_t *ph, mdi_pathinfo_t *pip)
{
        ASSERT(DEVI_BUSY_OWNED(ph->ph_dip));

        MDI_PHCI_LOCK(ph);
        if (ph->ph_path_head == NULL) {
                ph->ph_path_head = pip;
        } else {
                MDI_PI(ph->ph_path_tail)->pi_phci_link = MDI_PI(pip);
        }
        ph->ph_path_tail = pip;
        ph->ph_path_count++;
        MDI_PHCI_UNLOCK(ph);
}

/*
 * i_mdi_client_add_path():
 *              Add mdi_pathinfo node to client list
 */
static void
i_mdi_client_add_path(mdi_client_t *ct, mdi_pathinfo_t *pip)
{
        ASSERT(DEVI_BUSY_OWNED(ct->ct_dip));

        MDI_CLIENT_LOCK(ct);
        if (ct->ct_path_head == NULL) {
                ct->ct_path_head = pip;
        } else {
                MDI_PI(ct->ct_path_tail)->pi_client_link = MDI_PI(pip);
        }
        ct->ct_path_tail = pip;
        ct->ct_path_count++;
        MDI_CLIENT_UNLOCK(ct);
}

/*
 * mdi_pi_free():
 *              Free the mdi_pathinfo node and also client device node if this
 *              is the last path to the device
 * Return Values:
 *              MDI_SUCCESS
 *              MDI_FAILURE
 *              MDI_BUSY
 */
/*ARGSUSED*/
int
mdi_pi_free(mdi_pathinfo_t *pip, int flags)
{
        int             rv;
        mdi_vhci_t      *vh;
        mdi_phci_t      *ph;
        mdi_client_t    *ct;
        int             (*f)();
        int             client_held = 0;

        MDI_PI_LOCK(pip);
        ph = MDI_PI(pip)->pi_phci;
        ASSERT(ph != NULL);
        if (ph == NULL) {
                /*
                 * Invalid pHCI device, return failure
                 */
                MDI_DEBUG(1, (MDI_WARN, NULL,
                    "!invalid pHCI: pip %s %p",
                    mdi_pi_spathname(pip), (void *)pip));
                MDI_PI_UNLOCK(pip);
                return (MDI_FAILURE);
        }

        vh = ph->ph_vhci;
        ASSERT(vh != NULL);
        if (vh == NULL) {
                /* Invalid pHCI device, return failure */
                MDI_DEBUG(1, (MDI_WARN, ph->ph_dip,
                    "!invalid vHCI: pip %s %p",
                    mdi_pi_spathname(pip), (void *)pip));
                MDI_PI_UNLOCK(pip);
                return (MDI_FAILURE);
        }

        ct = MDI_PI(pip)->pi_client;
        ASSERT(ct != NULL);
        if (ct == NULL) {
                /*
                 * Invalid Client device, return failure
                 */
                MDI_DEBUG(1, (MDI_WARN, ph->ph_dip,
                    "!invalid client: pip %s %p",
                    mdi_pi_spathname(pip), (void *)pip));
                MDI_PI_UNLOCK(pip);
                return (MDI_FAILURE);
        }

        /*
         * Check to see for busy condition.  A mdi_pathinfo can only be freed
         * if the node state is either offline or init and the reference count
         * is zero.
         */
        if (!(MDI_PI_IS_OFFLINE(pip) || MDI_PI_IS_INIT(pip) ||
            MDI_PI_IS_INITING(pip))) {
                /*
                 * Node is busy
                 */
                MDI_DEBUG(1, (MDI_WARN, ct->ct_dip,
                    "!busy: pip %s %p", mdi_pi_spathname(pip), (void *)pip));
                MDI_PI_UNLOCK(pip);
                return (MDI_BUSY);
        }

        while (MDI_PI(pip)->pi_ref_cnt != 0) {
                /*
                 * Give a chance for pending I/Os to complete.
                 */
                MDI_DEBUG(1, (MDI_NOTE, ct->ct_dip,
                    "!%d cmds still pending on path: %s %p",
                    MDI_PI(pip)->pi_ref_cnt,
                    mdi_pi_spathname(pip), (void *)pip));
                if (cv_reltimedwait(&MDI_PI(pip)->pi_ref_cv,
                    &MDI_PI(pip)->pi_mutex, drv_usectohz(60 * 1000000),
                    TR_CLOCK_TICK) == -1) {
                        /*
                         * The timeout time reached without ref_cnt being zero
                         * being signaled.
                         */
                        MDI_DEBUG(1, (MDI_NOTE, ct->ct_dip,
                            "!Timeout reached on path %s %p without the cond",
                            mdi_pi_spathname(pip), (void *)pip));
                        MDI_DEBUG(1, (MDI_NOTE, ct->ct_dip,
                            "!%d cmds still pending on path %s %p",
                            MDI_PI(pip)->pi_ref_cnt,
                            mdi_pi_spathname(pip), (void *)pip));
                        MDI_PI_UNLOCK(pip);
                        return (MDI_BUSY);
                }
        }
        if (MDI_PI(pip)->pi_pm_held) {
                client_held = 1;
        }
        MDI_PI_UNLOCK(pip);

        vhcache_pi_remove(vh->vh_config, MDI_PI(pip));

        MDI_CLIENT_LOCK(ct);

        /* Prevent further failovers till MDI_VHCI_CLIENT_LOCK is held */
        MDI_CLIENT_SET_PATH_FREE_IN_PROGRESS(ct);

        /*
         * Wait till failover is complete before removing this node.
         */
        while (MDI_CLIENT_IS_FAILOVER_IN_PROGRESS(ct))
                cv_wait(&ct->ct_failover_cv, &ct->ct_mutex);

        MDI_CLIENT_UNLOCK(ct);
        MDI_VHCI_CLIENT_LOCK(vh);
        MDI_CLIENT_LOCK(ct);
        MDI_CLIENT_CLEAR_PATH_FREE_IN_PROGRESS(ct);

        if (!MDI_PI_IS_INITING(pip)) {
                f = vh->vh_ops->vo_pi_uninit;
                if (f != NULL) {
                        rv = (*f)(vh->vh_dip, pip, 0);
                }
        } else
                rv = MDI_SUCCESS;

        /*
         * If vo_pi_uninit() completed successfully.
         */
        if (rv == MDI_SUCCESS) {
                if (client_held) {
                        MDI_DEBUG(4, (MDI_NOTE, ct->ct_dip,
                            "i_mdi_pm_rele_client\n"));
                        i_mdi_pm_rele_client(ct, 1);
                }
                i_mdi_pi_free(ph, pip, ct);
                if (ct->ct_path_count == 0) {
                        /*
                         * Client lost its last path.
                         * Clean up the client device
                         */
                        MDI_CLIENT_UNLOCK(ct);
                        (void) i_mdi_client_free(ct->ct_vhci, ct);
                        MDI_VHCI_CLIENT_UNLOCK(vh);
                        return (rv);
                }
        }
        MDI_CLIENT_UNLOCK(ct);
        MDI_VHCI_CLIENT_UNLOCK(vh);

        if (rv == MDI_FAILURE)
                vhcache_pi_add(vh->vh_config, MDI_PI(pip));

        return (rv);
}

/*
 * i_mdi_pi_free():
 *              Free the mdi_pathinfo node
 */
static void
i_mdi_pi_free(mdi_phci_t *ph, mdi_pathinfo_t *pip, mdi_client_t *ct)
{
        int     ct_circular;
        int     ph_circular;

        ASSERT(MDI_CLIENT_LOCKED(ct));

        /*
         * remove any per-path kstats
         */
        i_mdi_pi_kstat_destroy(pip);

        /* See comments in i_mdi_pi_alloc() */
        ndi_devi_enter(ct->ct_dip, &ct_circular);
        ndi_devi_enter(ph->ph_dip, &ph_circular);

        i_mdi_client_remove_path(ct, pip);
        i_mdi_phci_remove_path(ph, pip);

        ndi_devi_exit(ph->ph_dip, ph_circular);
        ndi_devi_exit(ct->ct_dip, ct_circular);

        mutex_destroy(&MDI_PI(pip)->pi_mutex);
        cv_destroy(&MDI_PI(pip)->pi_state_cv);
        cv_destroy(&MDI_PI(pip)->pi_ref_cv);
        if (MDI_PI(pip)->pi_addr) {
                kmem_free(MDI_PI(pip)->pi_addr,
                    strlen(MDI_PI(pip)->pi_addr) + 1);
                MDI_PI(pip)->pi_addr = NULL;
        }

        if (MDI_PI(pip)->pi_prop) {
                (void) nvlist_free(MDI_PI(pip)->pi_prop);
                MDI_PI(pip)->pi_prop = NULL;
        }
        kmem_free(pip, sizeof (struct mdi_pathinfo));
}


/*
 * i_mdi_phci_remove_path():
 *              Remove a mdi_pathinfo node from pHCI list.
 * Notes:
 *              Caller should hold per-pHCI mutex
 */
static void
i_mdi_phci_remove_path(mdi_phci_t *ph, mdi_pathinfo_t *pip)
{
        mdi_pathinfo_t  *prev = NULL;
        mdi_pathinfo_t  *path = NULL;

        ASSERT(DEVI_BUSY_OWNED(ph->ph_dip));

        MDI_PHCI_LOCK(ph);
        path = ph->ph_path_head;
        while (path != NULL) {
                if (path == pip) {
                        break;
                }
                prev = path;
                path = (mdi_pathinfo_t *)MDI_PI(path)->pi_phci_link;
        }

        if (path) {
                ph->ph_path_count--;
                if (prev) {
                        MDI_PI(prev)->pi_phci_link = MDI_PI(path)->pi_phci_link;
                } else {
                        ph->ph_path_head =
                            (mdi_pathinfo_t *)MDI_PI(path)->pi_phci_link;
                }
                if (ph->ph_path_tail == path) {
                        ph->ph_path_tail = prev;
                }
        }

        /*
         * Clear the pHCI link
         */
        MDI_PI(pip)->pi_phci_link = NULL;
        MDI_PI(pip)->pi_phci = NULL;
        MDI_PHCI_UNLOCK(ph);
}

/*
 * i_mdi_client_remove_path():
 *              Remove a mdi_pathinfo node from client path list.
 */
static void
i_mdi_client_remove_path(mdi_client_t *ct, mdi_pathinfo_t *pip)
{
        mdi_pathinfo_t  *prev = NULL;
        mdi_pathinfo_t  *path;

        ASSERT(DEVI_BUSY_OWNED(ct->ct_dip));

        ASSERT(MDI_CLIENT_LOCKED(ct));
        path = ct->ct_path_head;
        while (path != NULL) {
                if (path == pip) {
                        break;
                }
                prev = path;
                path = (mdi_pathinfo_t *)MDI_PI(path)->pi_client_link;
        }

        if (path) {
                ct->ct_path_count--;
                if (prev) {
                        MDI_PI(prev)->pi_client_link =
                            MDI_PI(path)->pi_client_link;
                } else {
                        ct->ct_path_head =
                            (mdi_pathinfo_t *)MDI_PI(path)->pi_client_link;
                }
                if (ct->ct_path_tail == path) {
                        ct->ct_path_tail = prev;
                }
                if (ct->ct_path_last == path) {
                        ct->ct_path_last = ct->ct_path_head;
                }
        }
        MDI_PI(pip)->pi_client_link = NULL;
        MDI_PI(pip)->pi_client = NULL;
}

/*
 * i_mdi_pi_state_change():
 *              online a mdi_pathinfo node
 *
 * Return Values:
 *              MDI_SUCCESS
 *              MDI_FAILURE
 */
/*ARGSUSED*/
static int
i_mdi_pi_state_change(mdi_pathinfo_t *pip, mdi_pathinfo_state_t state, int flag)
{
        int             rv = MDI_SUCCESS;
        mdi_vhci_t      *vh;
        mdi_phci_t      *ph;
        mdi_client_t    *ct;
        int             (*f)();
        dev_info_t      *cdip;

        MDI_PI_LOCK(pip);

        ph = MDI_PI(pip)->pi_phci;
        ASSERT(ph);
        if (ph == NULL) {
                /*
                 * Invalid pHCI device, fail the request
                 */
                MDI_PI_UNLOCK(pip);
                MDI_DEBUG(1, (MDI_WARN, NULL,
                    "!invalid phci: pip %s %p",
                    mdi_pi_spathname(pip), (void *)pip));
                return (MDI_FAILURE);
        }

        vh = ph->ph_vhci;
        ASSERT(vh);
        if (vh == NULL) {
                /*
                 * Invalid vHCI device, fail the request
                 */
                MDI_PI_UNLOCK(pip);
                MDI_DEBUG(1, (MDI_WARN, ph->ph_dip,
                    "!invalid vhci: pip %s %p",
                    mdi_pi_spathname(pip), (void *)pip));
                return (MDI_FAILURE);
        }

        ct = MDI_PI(pip)->pi_client;
        ASSERT(ct != NULL);
        if (ct == NULL) {
                /*
                 * Invalid client device, fail the request
                 */
                MDI_PI_UNLOCK(pip);
                MDI_DEBUG(1, (MDI_WARN, ph->ph_dip,
                    "!invalid client: pip %s %p",
                    mdi_pi_spathname(pip), (void *)pip));
                return (MDI_FAILURE);
        }

        /*
         * If this path has not been initialized yet, Callback vHCI driver's
         * pathinfo node initialize entry point
         */

        if (MDI_PI_IS_INITING(pip)) {
                MDI_PI_UNLOCK(pip);
                f = vh->vh_ops->vo_pi_init;
                if (f != NULL) {
                        rv = (*f)(vh->vh_dip, pip, 0);
                        if (rv != MDI_SUCCESS) {
                                MDI_DEBUG(1, (MDI_WARN, ct->ct_dip,
                                    "!vo_pi_init failed: vHCI %p, pip %s %p",
                                    (void *)vh, mdi_pi_spathname(pip),
                                    (void *)pip));
                                return (MDI_FAILURE);
                        }
                }
                MDI_PI_LOCK(pip);
                MDI_PI_CLEAR_TRANSIENT(pip);
        }

        /*
         * Do not allow state transition when pHCI is in offline/suspended
         * states
         */
        i_mdi_phci_lock(ph, pip);
        if (MDI_PHCI_IS_READY(ph) == 0) {
                MDI_DEBUG(1, (MDI_WARN, ct->ct_dip,
                    "!pHCI not ready, pHCI=%p", (void *)ph));
                MDI_PI_UNLOCK(pip);
                i_mdi_phci_unlock(ph);
                return (MDI_BUSY);
        }
        MDI_PHCI_UNSTABLE(ph);
        i_mdi_phci_unlock(ph);

        /*
         * Check if mdi_pathinfo state is in transient state.
         * If yes, offlining is in progress and wait till transient state is
         * cleared.
         */
        if (MDI_PI_IS_TRANSIENT(pip)) {
                while (MDI_PI_IS_TRANSIENT(pip)) {
                        cv_wait(&MDI_PI(pip)->pi_state_cv,
                            &MDI_PI(pip)->pi_mutex);
                }
        }

        /*
         * Grab the client lock in reverse order sequence and release the
         * mdi_pathinfo mutex.
         */
        i_mdi_client_lock(ct, pip);
        MDI_PI_UNLOCK(pip);

        /*
         * Wait till failover state is cleared
         */
        while (MDI_CLIENT_IS_FAILOVER_IN_PROGRESS(ct))
                cv_wait(&ct->ct_failover_cv, &ct->ct_mutex);

        /*
         * Mark the mdi_pathinfo node state as transient
         */
        MDI_PI_LOCK(pip);
        switch (state) {
        case MDI_PATHINFO_STATE_ONLINE:
                MDI_PI_SET_ONLINING(pip);
                break;

        case MDI_PATHINFO_STATE_STANDBY:
                MDI_PI_SET_STANDBYING(pip);
                break;

        case MDI_PATHINFO_STATE_FAULT:
                /*
                 * Mark the pathinfo state as FAULTED
                 */
                MDI_PI_SET_FAULTING(pip);
                MDI_PI_ERRSTAT(pip, MDI_PI_HARDERR);
                break;

        case MDI_PATHINFO_STATE_OFFLINE:
                /*
                 * ndi_devi_offline() cannot hold pip or ct locks.
                 */
                MDI_PI_UNLOCK(pip);

                /*
                 * If this is a user initiated path online->offline operation
                 * who's success would transition a client from DEGRADED to
                 * FAILED then only proceed if we can offline the client first.
                 */
                cdip = ct->ct_dip;
                if ((flag & NDI_USER_REQ) &&
                    MDI_PI_IS_ONLINE(pip) &&
                    (MDI_CLIENT_STATE(ct) == MDI_CLIENT_STATE_DEGRADED)) {
                        i_mdi_client_unlock(ct);
                        rv = ndi_devi_offline(cdip, NDI_DEVFS_CLEAN);
                        if (rv != NDI_SUCCESS) {
                                /*
                                 * Convert to MDI error code
                                 */
                                switch (rv) {
                                case NDI_BUSY:
                                        rv = MDI_BUSY;
                                        break;
                                default:
                                        rv = MDI_FAILURE;
                                        break;
                                }
                                goto state_change_exit;
                        } else {
                                i_mdi_client_lock(ct, NULL);
                        }
                }
                /*
                 * Mark the mdi_pathinfo node state as transient
                 */
                MDI_PI_LOCK(pip);
                MDI_PI_SET_OFFLINING(pip);
                break;
        }
        MDI_PI_UNLOCK(pip);
        MDI_CLIENT_UNSTABLE(ct);
        i_mdi_client_unlock(ct);

        f = vh->vh_ops->vo_pi_state_change;
        if (f != NULL)
                rv = (*f)(vh->vh_dip, pip, state, 0, flag);

        MDI_CLIENT_LOCK(ct);
        MDI_PI_LOCK(pip);
        if (rv == MDI_NOT_SUPPORTED) {
                MDI_CLIENT_SET_DEV_NOT_SUPPORTED(ct);
        }
        if (rv != MDI_SUCCESS) {
                MDI_DEBUG(2, (MDI_WARN, ct->ct_dip,
                    "vo_pi_state_change failed: rv %x", rv));
        }
        if (MDI_PI_IS_TRANSIENT(pip)) {
                if (rv == MDI_SUCCESS) {
                        MDI_PI_CLEAR_TRANSIENT(pip);
                } else {
                        MDI_PI(pip)->pi_state = MDI_PI_OLD_STATE(pip);
                }
        }

        /*
         * Wake anyone waiting for this mdi_pathinfo node
         */
        cv_broadcast(&MDI_PI(pip)->pi_state_cv);
        MDI_PI_UNLOCK(pip);

        /*
         * Mark the client device as stable
         */
        MDI_CLIENT_STABLE(ct);
        if (rv == MDI_SUCCESS) {
                if (ct->ct_unstable == 0) {
                        cdip = ct->ct_dip;

                        /*
                         * Onlining the mdi_pathinfo node will impact the
                         * client state Update the client and dev_info node
                         * state accordingly
                         */
                        rv = NDI_SUCCESS;
                        i_mdi_client_update_state(ct);
                        switch (MDI_CLIENT_STATE(ct)) {
                        case MDI_CLIENT_STATE_OPTIMAL:
                        case MDI_CLIENT_STATE_DEGRADED:
                                if (cdip && !i_ddi_devi_attached(cdip) &&
                                    ((state == MDI_PATHINFO_STATE_ONLINE) ||
                                    (state == MDI_PATHINFO_STATE_STANDBY))) {

                                        /*
                                         * Must do ndi_devi_online() through
                                         * hotplug thread for deferred
                                         * attach mechanism to work
                                         */
                                        MDI_CLIENT_UNLOCK(ct);
                                        rv = ndi_devi_online(cdip, 0);
                                        MDI_CLIENT_LOCK(ct);
                                        if ((rv != NDI_SUCCESS) &&
                                            (MDI_CLIENT_STATE(ct) ==
                                            MDI_CLIENT_STATE_DEGRADED)) {
                                                MDI_DEBUG(1, (MDI_WARN, cdip,
                                                    "!ndi_devi_online failed "
                                                    "error %x", rv));
                                        }
                                        rv = NDI_SUCCESS;
                                }
                                break;

                        case MDI_CLIENT_STATE_FAILED:
                                /*
                                 * This is the last path case for
                                 * non-user initiated events.
                                 */
                                if (((flag & NDI_USER_REQ) == 0) &&
                                    cdip && (i_ddi_node_state(cdip) >=
                                    DS_INITIALIZED)) {
                                        MDI_CLIENT_UNLOCK(ct);
                                        rv = ndi_devi_offline(cdip,
                                            NDI_DEVFS_CLEAN);
                                        MDI_CLIENT_LOCK(ct);

                                        if (rv != NDI_SUCCESS) {
                                                /*
                                                 * ndi_devi_offline failed.
                                                 * Reset client flags to
                                                 * online as the path could not
                                                 * be offlined.
                                                 */
                                                MDI_DEBUG(1, (MDI_WARN, cdip,
                                                    "!ndi_devi_offline failed: "
                                                    "error %x", rv));
                                                MDI_CLIENT_SET_ONLINE(ct);
                                        }
                                }
                                break;
                        }
                        /*
                         * Convert to MDI error code
                         */
                        switch (rv) {
                        case NDI_SUCCESS:
                                MDI_CLIENT_SET_REPORT_DEV_NEEDED(ct);
                                i_mdi_report_path_state(ct, pip);
                                rv = MDI_SUCCESS;
                                break;
                        case NDI_BUSY:
                                rv = MDI_BUSY;
                                break;
                        default:
                                rv = MDI_FAILURE;
                                break;
                        }
                }
        }
        MDI_CLIENT_UNLOCK(ct);

state_change_exit:
        /*
         * Mark the pHCI as stable again.
         */
        MDI_PHCI_LOCK(ph);
        MDI_PHCI_STABLE(ph);
        MDI_PHCI_UNLOCK(ph);
        return (rv);
}

/*
 * mdi_pi_online():
 *              Place the path_info node in the online state.  The path is
 *              now available to be selected by mdi_select_path() for
 *              transporting I/O requests to client devices.
 * Return Values:
 *              MDI_SUCCESS
 *              MDI_FAILURE
 */
int
mdi_pi_online(mdi_pathinfo_t *pip, int flags)
{
        mdi_client_t    *ct = MDI_PI(pip)->pi_client;
        int             client_held = 0;
        int             rv;

        ASSERT(ct != NULL);
        rv = i_mdi_pi_state_change(pip, MDI_PATHINFO_STATE_ONLINE, flags);
        if (rv != MDI_SUCCESS)
                return (rv);

        MDI_PI_LOCK(pip);
        if (MDI_PI(pip)->pi_pm_held == 0) {
                MDI_DEBUG(4, (MDI_NOTE, ct->ct_dip,
                    "i_mdi_pm_hold_pip %p", (void *)pip));
                i_mdi_pm_hold_pip(pip);
                client_held = 1;
        }
        MDI_PI_UNLOCK(pip);

        if (client_held) {
                MDI_CLIENT_LOCK(ct);
                if (ct->ct_power_cnt == 0) {
                        rv = i_mdi_power_all_phci(ct);
                }

                MDI_DEBUG(4, (MDI_NOTE, ct->ct_dip,
                    "i_mdi_pm_hold_client %p", (void *)ct));
                i_mdi_pm_hold_client(ct, 1);
                MDI_CLIENT_UNLOCK(ct);
        }

        return (rv);
}

/*
 * mdi_pi_standby():
 *              Place the mdi_pathinfo node in standby state
 *
 * Return Values:
 *              MDI_SUCCESS
 *              MDI_FAILURE
 */
int
mdi_pi_standby(mdi_pathinfo_t *pip, int flags)
{
        return (i_mdi_pi_state_change(pip, MDI_PATHINFO_STATE_STANDBY, flags));
}

/*
 * mdi_pi_fault():
 *              Place the mdi_pathinfo node in fault'ed state
 * Return Values:
 *              MDI_SUCCESS
 *              MDI_FAILURE
 */
int
mdi_pi_fault(mdi_pathinfo_t *pip, int flags)
{
        return (i_mdi_pi_state_change(pip, MDI_PATHINFO_STATE_FAULT, flags));
}

/*
 * mdi_pi_offline():
 *              Offline a mdi_pathinfo node.
 * Return Values:
 *              MDI_SUCCESS
 *              MDI_FAILURE
 */
int
mdi_pi_offline(mdi_pathinfo_t *pip, int flags)
{
        int     ret, client_held = 0;
        mdi_client_t    *ct;

        /*
         * Original code overloaded NDI_DEVI_REMOVE to this interface, and
         * used it to mean "user initiated operation" (i.e. devctl). Callers
         * should now just use NDI_USER_REQ.
         */
        if (flags & NDI_DEVI_REMOVE) {
                flags &= ~NDI_DEVI_REMOVE;
                flags |= NDI_USER_REQ;
        }

        ret = i_mdi_pi_state_change(pip, MDI_PATHINFO_STATE_OFFLINE, flags);

        if (ret == MDI_SUCCESS) {
                MDI_PI_LOCK(pip);
                if (MDI_PI(pip)->pi_pm_held) {
                        client_held = 1;
                }
                MDI_PI_UNLOCK(pip);

                if (client_held) {
                        ct = MDI_PI(pip)->pi_client;
                        MDI_CLIENT_LOCK(ct);
                        MDI_DEBUG(4, (MDI_NOTE, ct->ct_dip,
                            "i_mdi_pm_rele_client\n"));
                        i_mdi_pm_rele_client(ct, 1);
                        MDI_CLIENT_UNLOCK(ct);
                }
        }

        return (ret);
}

/*
 * i_mdi_pi_offline():
 *              Offline a mdi_pathinfo node and call the vHCI driver's callback
 */
static int
i_mdi_pi_offline(mdi_pathinfo_t *pip, int flags)
{
        dev_info_t      *vdip = NULL;
        mdi_vhci_t      *vh = NULL;
        mdi_client_t    *ct = NULL;
        int             (*f)();
        int             rv;

        MDI_PI_LOCK(pip);
        ct = MDI_PI(pip)->pi_client;
        ASSERT(ct != NULL);

        while (MDI_PI(pip)->pi_ref_cnt != 0) {
                /*
                 * Give a chance for pending I/Os to complete.
                 */
                MDI_DEBUG(1, (MDI_NOTE, ct->ct_dip,
                    "!%d cmds still pending on path %s %p",
                    MDI_PI(pip)->pi_ref_cnt, mdi_pi_spathname(pip),
                    (void *)pip));
                if (cv_reltimedwait(&MDI_PI(pip)->pi_ref_cv,
                    &MDI_PI(pip)->pi_mutex, drv_usectohz(60 * 1000000),
                    TR_CLOCK_TICK) == -1) {
                        /*
                         * The timeout time reached without ref_cnt being zero
                         * being signaled.
                         */
                        MDI_DEBUG(1, (MDI_NOTE, ct->ct_dip,
                            "!Timeout reached on path %s %p without the cond",
                            mdi_pi_spathname(pip), (void *)pip));
                        MDI_DEBUG(1, (MDI_NOTE, ct->ct_dip,
                            "!%d cmds still pending on path %s %p",
                            MDI_PI(pip)->pi_ref_cnt,
                            mdi_pi_spathname(pip), (void *)pip));
                }
        }
        vh = ct->ct_vhci;
        vdip = vh->vh_dip;

        /*
         * Notify vHCI that has registered this event
         */
        ASSERT(vh->vh_ops);
        f = vh->vh_ops->vo_pi_state_change;

        if (f != NULL) {
                MDI_PI_UNLOCK(pip);
                if ((rv = (*f)(vdip, pip, MDI_PATHINFO_STATE_OFFLINE, 0,
                    flags)) != MDI_SUCCESS) {
                        MDI_DEBUG(1, (MDI_WARN, ct->ct_dip,
                            "!vo_path_offline failed: vdip %s%d %p: path %s %p",
                            ddi_driver_name(vdip), ddi_get_instance(vdip),
                            (void *)vdip, mdi_pi_spathname(pip), (void *)pip));
                }
                MDI_PI_LOCK(pip);
        }

        /*
         * Set the mdi_pathinfo node state and clear the transient condition
         */
        MDI_PI_SET_OFFLINE(pip);
        cv_broadcast(&MDI_PI(pip)->pi_state_cv);
        MDI_PI_UNLOCK(pip);

        MDI_CLIENT_LOCK(ct);
        if (rv == MDI_SUCCESS) {
                if (ct->ct_unstable == 0) {
                        dev_info_t      *cdip = ct->ct_dip;

                        /*
                         * Onlining the mdi_pathinfo node will impact the
                         * client state Update the client and dev_info node
                         * state accordingly
                         */
                        i_mdi_client_update_state(ct);
                        rv = NDI_SUCCESS;
                        if (MDI_CLIENT_STATE(ct) == MDI_CLIENT_STATE_FAILED) {
                                if (cdip &&
                                    (i_ddi_node_state(cdip) >=
                                    DS_INITIALIZED)) {
                                        MDI_CLIENT_UNLOCK(ct);
                                        rv = ndi_devi_offline(cdip,
                                            NDI_DEVFS_CLEAN);
                                        MDI_CLIENT_LOCK(ct);
                                        if (rv != NDI_SUCCESS) {
                                                /*
                                                 * ndi_devi_offline failed.
                                                 * Reset client flags to
                                                 * online.
                                                 */
                                                MDI_DEBUG(4, (MDI_WARN, cdip,
                                                    "ndi_devi_offline failed: "
                                                    "error %x", rv));
                                                MDI_CLIENT_SET_ONLINE(ct);
                                        }
                                }
                        }
                        /*
                         * Convert to MDI error code
                         */
                        switch (rv) {
                        case NDI_SUCCESS:
                                rv = MDI_SUCCESS;
                                break;
                        case NDI_BUSY:
                                rv = MDI_BUSY;
                                break;
                        default:
                                rv = MDI_FAILURE;
                                break;
                        }
                }
                MDI_CLIENT_SET_REPORT_DEV_NEEDED(ct);
                i_mdi_report_path_state(ct, pip);
        }

        MDI_CLIENT_UNLOCK(ct);

        /*
         * Change in the mdi_pathinfo node state will impact the client state
         */
        MDI_DEBUG(2, (MDI_NOTE, ct->ct_dip,
            "ct = %p pip = %p", (void *)ct, (void *)pip));
        return (rv);
}

/*
 * i_mdi_pi_online():
 *              Online a mdi_pathinfo node and call the vHCI driver's callback
 */
static int
i_mdi_pi_online(mdi_pathinfo_t *pip, int flags)
{
        mdi_vhci_t      *vh = NULL;
        mdi_client_t    *ct = NULL;
        mdi_phci_t      *ph;
        int             (*f)();
        int             rv;

        MDI_PI_LOCK(pip);
        ph = MDI_PI(pip)->pi_phci;
        vh = ph->ph_vhci;
        ct = MDI_PI(pip)->pi_client;
        MDI_PI_SET_ONLINING(pip)
        MDI_PI_UNLOCK(pip);
        f = vh->vh_ops->vo_pi_state_change;
        if (f != NULL)
                rv = (*f)(vh->vh_dip, pip, MDI_PATHINFO_STATE_ONLINE, 0,
                    flags);
        MDI_CLIENT_LOCK(ct);
        MDI_PI_LOCK(pip);
        cv_broadcast(&MDI_PI(pip)->pi_state_cv);
        MDI_PI_UNLOCK(pip);
        if (rv == MDI_SUCCESS) {
                dev_info_t      *cdip = ct->ct_dip;

                rv = MDI_SUCCESS;
                i_mdi_client_update_state(ct);
                if (MDI_CLIENT_STATE(ct) == MDI_CLIENT_STATE_OPTIMAL ||
                    MDI_CLIENT_STATE(ct) == MDI_CLIENT_STATE_DEGRADED) {
                        if (cdip && !i_ddi_devi_attached(cdip)) {
                                MDI_CLIENT_UNLOCK(ct);
                                rv = ndi_devi_online(cdip, 0);
                                MDI_CLIENT_LOCK(ct);
                                if ((rv != NDI_SUCCESS) &&
                                    (MDI_CLIENT_STATE(ct) ==
                                    MDI_CLIENT_STATE_DEGRADED)) {
                                        MDI_CLIENT_SET_OFFLINE(ct);
                                }
                                if (rv != NDI_SUCCESS) {
                                        /* Reset the path state */
                                        MDI_PI_LOCK(pip);
                                        MDI_PI(pip)->pi_state =
                                            MDI_PI_OLD_STATE(pip);
                                        MDI_PI_UNLOCK(pip);
                                }
                        }
                }
                switch (rv) {
                case NDI_SUCCESS:
                        MDI_CLIENT_SET_REPORT_DEV_NEEDED(ct);
                        i_mdi_report_path_state(ct, pip);
                        rv = MDI_SUCCESS;
                        break;
                case NDI_BUSY:
                        rv = MDI_BUSY;
                        break;
                default:
                        rv = MDI_FAILURE;
                        break;
                }
        } else {
                /* Reset the path state */
                MDI_PI_LOCK(pip);
                MDI_PI(pip)->pi_state = MDI_PI_OLD_STATE(pip);
                MDI_PI_UNLOCK(pip);
        }
        MDI_CLIENT_UNLOCK(ct);
        return (rv);
}

/*
 * mdi_pi_get_node_name():
 *              Get the name associated with a mdi_pathinfo node.
 *              Since pathinfo nodes are not directly named, we
 *              return the node_name of the client.
 *
 * Return Values:
 *              char *
 */
char *
mdi_pi_get_node_name(mdi_pathinfo_t *pip)
{
        mdi_client_t    *ct;

        if (pip == NULL)
                return (NULL);
        ct = MDI_PI(pip)->pi_client;
        if ((ct == NULL) || (ct->ct_dip == NULL))
                return (NULL);
        return (ddi_node_name(ct->ct_dip));
}

/*
 * mdi_pi_get_addr():
 *              Get the unit address associated with a mdi_pathinfo node
 *
 * Return Values:
 *              char *
 */
char *
mdi_pi_get_addr(mdi_pathinfo_t *pip)
{
        if (pip == NULL)
                return (NULL);

        return (MDI_PI(pip)->pi_addr);
}

/*
 * mdi_pi_get_path_instance():
 *              Get the 'path_instance' of a mdi_pathinfo node
 *
 * Return Values:
 *              path_instance
 */
int
mdi_pi_get_path_instance(mdi_pathinfo_t *pip)
{
        if (pip == NULL)
                return (0);

        return (MDI_PI(pip)->pi_path_instance);
}

/*
 * mdi_pi_pathname():
 *              Return pointer to path to pathinfo node.
 */
char *
mdi_pi_pathname(mdi_pathinfo_t *pip)
{
        if (pip == NULL)
                return (NULL);
        return (mdi_pi_pathname_by_instance(mdi_pi_get_path_instance(pip)));
}

/*
 * mdi_pi_spathname():
 *              Return pointer to shortpath to pathinfo node. Used for debug
 *              messages, so return "" instead of NULL when unknown.
 */
char *
mdi_pi_spathname(mdi_pathinfo_t *pip)
{
        char    *spath = "";

        if (pip) {
                spath = mdi_pi_spathname_by_instance(
                    mdi_pi_get_path_instance(pip));
                if (spath == NULL)
                        spath = "";
        }
        return (spath);
}

char *
mdi_pi_pathname_obp(mdi_pathinfo_t *pip, char *path)
{
        char *obp_path = NULL;
        if ((pip == NULL) || (path == NULL))
                return (NULL);

        if (mdi_prop_lookup_string(pip, "obp-path", &obp_path) == MDI_SUCCESS) {
                (void) strcpy(path, obp_path);
                (void) mdi_prop_free(obp_path);
        } else {
                path = NULL;
        }
        return (path);
}

int
mdi_pi_pathname_obp_set(mdi_pathinfo_t *pip, char *component)
{
        dev_info_t *pdip;
        char *obp_path = NULL;
        int rc = MDI_FAILURE;

        if (pip == NULL)
                return (MDI_FAILURE);

        pdip = mdi_pi_get_phci(pip);
        if (pdip == NULL)
                return (MDI_FAILURE);

        obp_path = kmem_zalloc(MAXPATHLEN, KM_SLEEP);

        if (ddi_pathname_obp(pdip, obp_path) == NULL) {
                (void) ddi_pathname(pdip, obp_path);
        }

        if (component) {
                (void) strncat(obp_path, "/", MAXPATHLEN);
                (void) strncat(obp_path, component, MAXPATHLEN);
        }
        rc = mdi_prop_update_string(pip, "obp-path", obp_path);

        if (obp_path)
                kmem_free(obp_path, MAXPATHLEN);
        return (rc);
}

/*
 * mdi_pi_get_client():
 *              Get the client devinfo associated with a mdi_pathinfo node
 *
 * Return Values:
 *              Handle to client device dev_info node
 */
dev_info_t *
mdi_pi_get_client(mdi_pathinfo_t *pip)
{
        dev_info_t      *dip = NULL;
        if (pip) {
                dip = MDI_PI(pip)->pi_client->ct_dip;
        }
        return (dip);
}

/*
 * mdi_pi_get_phci():
 *              Get the pHCI devinfo associated with the mdi_pathinfo node
 * Return Values:
 *              Handle to dev_info node
 */
dev_info_t *
mdi_pi_get_phci(mdi_pathinfo_t *pip)
{
        dev_info_t      *dip = NULL;
        mdi_phci_t      *ph;

        if (pip) {
                ph = MDI_PI(pip)->pi_phci;
                if (ph)
                        dip = ph->ph_dip;
        }
        return (dip);
}

/*
 * mdi_pi_get_client_private():
 *              Get the client private information associated with the
 *              mdi_pathinfo node
 */
void *
mdi_pi_get_client_private(mdi_pathinfo_t *pip)
{
        void *cprivate = NULL;
        if (pip) {
                cprivate = MDI_PI(pip)->pi_cprivate;
        }
        return (cprivate);
}

/*
 * mdi_pi_set_client_private():
 *              Set the client private information in the mdi_pathinfo node
 */
void
mdi_pi_set_client_private(mdi_pathinfo_t *pip, void *priv)
{
        if (pip) {
                MDI_PI(pip)->pi_cprivate = priv;
        }
}

/*
 * mdi_pi_get_phci_private():
 *              Get the pHCI private information associated with the
 *              mdi_pathinfo node
 */
caddr_t
mdi_pi_get_phci_private(mdi_pathinfo_t *pip)
{
        caddr_t pprivate = NULL;

        if (pip) {
                pprivate = MDI_PI(pip)->pi_pprivate;
        }
        return (pprivate);
}

/*
 * mdi_pi_set_phci_private():
 *              Set the pHCI private information in the mdi_pathinfo node
 */
void
mdi_pi_set_phci_private(mdi_pathinfo_t *pip, caddr_t priv)
{
        if (pip) {
                MDI_PI(pip)->pi_pprivate = priv;
        }
}

/*
 * mdi_pi_get_state():
 *              Get the mdi_pathinfo node state. Transient states are internal
 *              and not provided to the users
 */
mdi_pathinfo_state_t
mdi_pi_get_state(mdi_pathinfo_t *pip)
{
        mdi_pathinfo_state_t    state = MDI_PATHINFO_STATE_INIT;

        if (pip) {
                if (MDI_PI_IS_TRANSIENT(pip)) {
                        /*
                         * mdi_pathinfo is in state transition.  Return the
                         * last good state.
                         */
                        state = MDI_PI_OLD_STATE(pip);
                } else {
                        state = MDI_PI_STATE(pip);
                }
        }
        return (state);
}

/*
 * mdi_pi_get_flags():
 *              Get the mdi_pathinfo node flags.
 */
uint_t
mdi_pi_get_flags(mdi_pathinfo_t *pip)
{
        return (pip ? MDI_PI(pip)->pi_flags : 0);
}

/*
 * Note that the following function needs to be the new interface for
 * mdi_pi_get_state when mpxio gets integrated to ON.
 */
int
mdi_pi_get_state2(mdi_pathinfo_t *pip, mdi_pathinfo_state_t *state,
                uint32_t *ext_state)
{
        *state = MDI_PATHINFO_STATE_INIT;

        if (pip) {
                if (MDI_PI_IS_TRANSIENT(pip)) {
                        /*
                         * mdi_pathinfo is in state transition.  Return the
                         * last good state.
                         */
                        *state = MDI_PI_OLD_STATE(pip);
                        *ext_state = MDI_PI_OLD_EXT_STATE(pip);
                } else {
                        *state = MDI_PI_STATE(pip);
                        *ext_state = MDI_PI_EXT_STATE(pip);
                }
        }
        return (MDI_SUCCESS);
}

/*
 * mdi_pi_get_preferred:
 *      Get the preferred path flag
 */
int
mdi_pi_get_preferred(mdi_pathinfo_t *pip)
{
        if (pip) {
                return (MDI_PI(pip)->pi_preferred);
        }
        return (0);
}

/*
 * mdi_pi_set_preferred:
 *      Set the preferred path flag
 */
void
mdi_pi_set_preferred(mdi_pathinfo_t *pip, int preferred)
{
        if (pip) {
                MDI_PI(pip)->pi_preferred = preferred;
        }
}

/*
 * mdi_pi_set_state():
 *              Set the mdi_pathinfo node state
 */
void
mdi_pi_set_state(mdi_pathinfo_t *pip, mdi_pathinfo_state_t state)
{
        uint32_t        ext_state;

        if (pip) {
                ext_state = MDI_PI(pip)->pi_state & MDI_PATHINFO_EXT_STATE_MASK;
                MDI_PI(pip)->pi_state = state;
                MDI_PI(pip)->pi_state |= ext_state;

                /* Path has changed state, invalidate DINFOCACHE snap shot. */
                i_ddi_di_cache_invalidate();
        }
}

/*
 * Property functions:
 */
int
i_map_nvlist_error_to_mdi(int val)
{
        int rv;

        switch (val) {
        case 0:
                rv = DDI_PROP_SUCCESS;
                break;
        case EINVAL:
        case ENOTSUP:
                rv = DDI_PROP_INVAL_ARG;
                break;
        case ENOMEM:
                rv = DDI_PROP_NO_MEMORY;
                break;
        default:
                rv = DDI_PROP_NOT_FOUND;
                break;
        }
        return (rv);
}

/*
 * mdi_pi_get_next_prop():
 *              Property walk function.  The caller should hold mdi_pi_lock()
 *              and release by calling mdi_pi_unlock() at the end of walk to
 *              get a consistent value.
 */
nvpair_t *
mdi_pi_get_next_prop(mdi_pathinfo_t *pip, nvpair_t *prev)
{
        if ((pip == NULL) || (MDI_PI(pip)->pi_prop == NULL)) {
                return (NULL);
        }
        ASSERT(MDI_PI_LOCKED(pip));
        return (nvlist_next_nvpair(MDI_PI(pip)->pi_prop, prev));
}

/*
 * mdi_prop_remove():
 *              Remove the named property from the named list.
 */
int
mdi_prop_remove(mdi_pathinfo_t *pip, char *name)
{
        if (pip == NULL) {
                return (DDI_PROP_NOT_FOUND);
        }
        ASSERT(!MDI_PI_LOCKED(pip));
        MDI_PI_LOCK(pip);
        if (MDI_PI(pip)->pi_prop == NULL) {
                MDI_PI_UNLOCK(pip);
                return (DDI_PROP_NOT_FOUND);
        }
        if (name) {
                (void) nvlist_remove_all(MDI_PI(pip)->pi_prop, name);
        } else {
                char            nvp_name[MAXNAMELEN];
                nvpair_t        *nvp;
                nvp = nvlist_next_nvpair(MDI_PI(pip)->pi_prop, NULL);
                while (nvp) {
                        nvpair_t        *next;
                        next = nvlist_next_nvpair(MDI_PI(pip)->pi_prop, nvp);
                        (void) snprintf(nvp_name, sizeof(nvp_name), "%s",
                            nvpair_name(nvp));
                        (void) nvlist_remove_all(MDI_PI(pip)->pi_prop,
                            nvp_name);
                        nvp = next;
                }
        }
        MDI_PI_UNLOCK(pip);
        return (DDI_PROP_SUCCESS);
}

/*
 * mdi_prop_size():
 *              Get buffer size needed to pack the property data.
 *              Caller should hold the mdi_pathinfo_t lock to get a consistent
 *              buffer size.
 */
int
mdi_prop_size(mdi_pathinfo_t *pip, size_t *buflenp)
{
        int     rv;
        size_t  bufsize;

        *buflenp = 0;
        if ((pip == NULL) || (MDI_PI(pip)->pi_prop == NULL)) {
                return (DDI_PROP_NOT_FOUND);
        }
        ASSERT(MDI_PI_LOCKED(pip));
        rv = nvlist_size(MDI_PI(pip)->pi_prop,
            &bufsize, NV_ENCODE_NATIVE);
        *buflenp = bufsize;
        return (i_map_nvlist_error_to_mdi(rv));
}

/*
 * mdi_prop_pack():
 *              pack the property list.  The caller should hold the
 *              mdi_pathinfo_t node to get a consistent data
 */
int
mdi_prop_pack(mdi_pathinfo_t *pip, char **bufp, uint_t buflen)
{
        int     rv;
        size_t  bufsize;

        if ((pip == NULL) || MDI_PI(pip)->pi_prop == NULL) {
                return (DDI_PROP_NOT_FOUND);
        }

        ASSERT(MDI_PI_LOCKED(pip));

        bufsize = buflen;
        rv = nvlist_pack(MDI_PI(pip)->pi_prop, bufp, (size_t *)&bufsize,
            NV_ENCODE_NATIVE, KM_SLEEP);

        return (i_map_nvlist_error_to_mdi(rv));
}

/*
 * mdi_prop_update_byte():
 *              Create/Update a byte property
 */
int
mdi_prop_update_byte(mdi_pathinfo_t *pip, char *name, uchar_t data)
{
        int rv;

        if (pip == NULL) {
                return (DDI_PROP_INVAL_ARG);
        }
        ASSERT(!MDI_PI_LOCKED(pip));
        MDI_PI_LOCK(pip);
        if (MDI_PI(pip)->pi_prop == NULL) {
                MDI_PI_UNLOCK(pip);
                return (DDI_PROP_NOT_FOUND);
        }
        rv = nvlist_add_byte(MDI_PI(pip)->pi_prop, name, data);
        MDI_PI_UNLOCK(pip);
        return (i_map_nvlist_error_to_mdi(rv));
}

/*
 * mdi_prop_update_byte_array():
 *              Create/Update a byte array property
 */
int
mdi_prop_update_byte_array(mdi_pathinfo_t *pip, char *name, uchar_t *data,
    uint_t nelements)
{
        int rv;

        if (pip == NULL) {
                return (DDI_PROP_INVAL_ARG);
        }
        ASSERT(!MDI_PI_LOCKED(pip));
        MDI_PI_LOCK(pip);
        if (MDI_PI(pip)->pi_prop == NULL) {
                MDI_PI_UNLOCK(pip);
                return (DDI_PROP_NOT_FOUND);
        }
        rv = nvlist_add_byte_array(MDI_PI(pip)->pi_prop, name, data, nelements);
        MDI_PI_UNLOCK(pip);
        return (i_map_nvlist_error_to_mdi(rv));
}

/*
 * mdi_prop_update_int():
 *              Create/Update a 32 bit integer property
 */
int
mdi_prop_update_int(mdi_pathinfo_t *pip, char *name, int data)
{
        int rv;

        if (pip == NULL) {
                return (DDI_PROP_INVAL_ARG);
        }
        ASSERT(!MDI_PI_LOCKED(pip));
        MDI_PI_LOCK(pip);
        if (MDI_PI(pip)->pi_prop == NULL) {
                MDI_PI_UNLOCK(pip);
                return (DDI_PROP_NOT_FOUND);
        }
        rv = nvlist_add_int32(MDI_PI(pip)->pi_prop, name, (int32_t)data);
        MDI_PI_UNLOCK(pip);
        return (i_map_nvlist_error_to_mdi(rv));
}

/*
 * mdi_prop_update_int64():
 *              Create/Update a 64 bit integer property
 */
int
mdi_prop_update_int64(mdi_pathinfo_t *pip, char *name, int64_t data)
{
        int rv;

        if (pip == NULL) {
                return (DDI_PROP_INVAL_ARG);
        }
        ASSERT(!MDI_PI_LOCKED(pip));
        MDI_PI_LOCK(pip);
        if (MDI_PI(pip)->pi_prop == NULL) {
                MDI_PI_UNLOCK(pip);
                return (DDI_PROP_NOT_FOUND);
        }
        rv = nvlist_add_int64(MDI_PI(pip)->pi_prop, name, data);
        MDI_PI_UNLOCK(pip);
        return (i_map_nvlist_error_to_mdi(rv));
}

/*
 * mdi_prop_update_int_array():
 *              Create/Update a int array property
 */
int
mdi_prop_update_int_array(mdi_pathinfo_t *pip, char *name, int *data,
            uint_t nelements)
{
        int rv;

        if (pip == NULL) {
                return (DDI_PROP_INVAL_ARG);
        }
        ASSERT(!MDI_PI_LOCKED(pip));
        MDI_PI_LOCK(pip);
        if (MDI_PI(pip)->pi_prop == NULL) {
                MDI_PI_UNLOCK(pip);
                return (DDI_PROP_NOT_FOUND);
        }
        rv = nvlist_add_int32_array(MDI_PI(pip)->pi_prop, name, (int32_t *)data,
            nelements);
        MDI_PI_UNLOCK(pip);
        return (i_map_nvlist_error_to_mdi(rv));
}

/*
 * mdi_prop_update_string():
 *              Create/Update a string property
 */
int
mdi_prop_update_string(mdi_pathinfo_t *pip, char *name, char *data)
{
        int rv;

        if (pip == NULL) {
                return (DDI_PROP_INVAL_ARG);
        }
        ASSERT(!MDI_PI_LOCKED(pip));
        MDI_PI_LOCK(pip);
        if (MDI_PI(pip)->pi_prop == NULL) {
                MDI_PI_UNLOCK(pip);
                return (DDI_PROP_NOT_FOUND);
        }
        rv = nvlist_add_string(MDI_PI(pip)->pi_prop, name, data);
        MDI_PI_UNLOCK(pip);
        return (i_map_nvlist_error_to_mdi(rv));
}

/*
 * mdi_prop_update_string_array():
 *              Create/Update a string array property
 */
int
mdi_prop_update_string_array(mdi_pathinfo_t *pip, char *name, char **data,
    uint_t nelements)
{
        int rv;

        if (pip == NULL) {
                return (DDI_PROP_INVAL_ARG);
        }
        ASSERT(!MDI_PI_LOCKED(pip));
        MDI_PI_LOCK(pip);
        if (MDI_PI(pip)->pi_prop == NULL) {
                MDI_PI_UNLOCK(pip);
                return (DDI_PROP_NOT_FOUND);
        }
        rv = nvlist_add_string_array(MDI_PI(pip)->pi_prop, name, data,
            nelements);
        MDI_PI_UNLOCK(pip);
        return (i_map_nvlist_error_to_mdi(rv));
}

/*
 * mdi_prop_lookup_byte():
 *              Look for byte property identified by name.  The data returned
 *              is the actual property and valid as long as mdi_pathinfo_t node
 *              is alive.
 */
int
mdi_prop_lookup_byte(mdi_pathinfo_t *pip, char *name, uchar_t *data)
{
        int rv;

        if ((pip == NULL) || (MDI_PI(pip)->pi_prop == NULL)) {
                return (DDI_PROP_NOT_FOUND);
        }
        rv = nvlist_lookup_byte(MDI_PI(pip)->pi_prop, name, data);
        return (i_map_nvlist_error_to_mdi(rv));
}


/*
 * mdi_prop_lookup_byte_array():
 *              Look for byte array property identified by name.  The data
 *              returned is the actual property and valid as long as
 *              mdi_pathinfo_t node is alive.
 */
int
mdi_prop_lookup_byte_array(mdi_pathinfo_t *pip, char *name, uchar_t **data,
    uint_t *nelements)
{
        int rv;

        if ((pip == NULL) || (MDI_PI(pip)->pi_prop == NULL)) {
                return (DDI_PROP_NOT_FOUND);
        }
        rv = nvlist_lookup_byte_array(MDI_PI(pip)->pi_prop, name, data,
            nelements);
        return (i_map_nvlist_error_to_mdi(rv));
}

/*
 * mdi_prop_lookup_int():
 *              Look for int property identified by name.  The data returned
 *              is the actual property and valid as long as mdi_pathinfo_t
 *              node is alive.
 */
int
mdi_prop_lookup_int(mdi_pathinfo_t *pip, char *name, int *data)
{
        int rv;

        if ((pip == NULL) || (MDI_PI(pip)->pi_prop == NULL)) {
                return (DDI_PROP_NOT_FOUND);
        }
        rv = nvlist_lookup_int32(MDI_PI(pip)->pi_prop, name, (int32_t *)data);
        return (i_map_nvlist_error_to_mdi(rv));
}

/*
 * mdi_prop_lookup_int64():
 *              Look for int64 property identified by name.  The data returned
 *              is the actual property and valid as long as mdi_pathinfo_t node
 *              is alive.
 */
int
mdi_prop_lookup_int64(mdi_pathinfo_t *pip, char *name, int64_t *data)
{
        int rv;
        if ((pip == NULL) || (MDI_PI(pip)->pi_prop == NULL)) {
                return (DDI_PROP_NOT_FOUND);
        }
        rv = nvlist_lookup_int64(MDI_PI(pip)->pi_prop, name, data);
        return (i_map_nvlist_error_to_mdi(rv));
}

/*
 * mdi_prop_lookup_int_array():
 *              Look for int array property identified by name.  The data
 *              returned is the actual property and valid as long as
 *              mdi_pathinfo_t node is alive.
 */
int
mdi_prop_lookup_int_array(mdi_pathinfo_t *pip, char *name, int **data,
    uint_t *nelements)
{
        int rv;

        if ((pip == NULL) || (MDI_PI(pip)->pi_prop == NULL)) {
                return (DDI_PROP_NOT_FOUND);
        }
        rv = nvlist_lookup_int32_array(MDI_PI(pip)->pi_prop, name,
            (int32_t **)data, nelements);
        return (i_map_nvlist_error_to_mdi(rv));
}

/*
 * mdi_prop_lookup_string():
 *              Look for string property identified by name.  The data
 *              returned is the actual property and valid as long as
 *              mdi_pathinfo_t node is alive.
 */
int
mdi_prop_lookup_string(mdi_pathinfo_t *pip, char *name, char **data)
{
        int rv;

        if ((pip == NULL) || (MDI_PI(pip)->pi_prop == NULL)) {
                return (DDI_PROP_NOT_FOUND);
        }
        rv = nvlist_lookup_string(MDI_PI(pip)->pi_prop, name, data);
        return (i_map_nvlist_error_to_mdi(rv));
}

/*
 * mdi_prop_lookup_string_array():
 *              Look for string array property identified by name.  The data
 *              returned is the actual property and valid as long as
 *              mdi_pathinfo_t node is alive.
 */
int
mdi_prop_lookup_string_array(mdi_pathinfo_t *pip, char *name, char ***data,
    uint_t *nelements)
{
        int rv;

        if ((pip == NULL) || (MDI_PI(pip)->pi_prop == NULL)) {
                return (DDI_PROP_NOT_FOUND);
        }
        rv = nvlist_lookup_string_array(MDI_PI(pip)->pi_prop, name, data,
            nelements);
        return (i_map_nvlist_error_to_mdi(rv));
}

/*
 * mdi_prop_free():
 *              Symmetrical function to ddi_prop_free(). nvlist_lookup_xx()
 *              functions return the pointer to actual property data and not a
 *              copy of it.  So the data returned is valid as long as
 *              mdi_pathinfo_t node is valid.
 */
/*ARGSUSED*/
int
mdi_prop_free(void *data)
{
        return (DDI_PROP_SUCCESS);
}

/*ARGSUSED*/
static void
i_mdi_report_path_state(mdi_client_t *ct, mdi_pathinfo_t *pip)
{
        char            *ct_path;
        char            *ct_status;
        char            *status;
        dev_info_t      *cdip = ct->ct_dip;
        char            lb_buf[64];
        int             report_lb_c = 0, report_lb_p = 0;

        ASSERT(MDI_CLIENT_LOCKED(ct));
        if ((cdip == NULL) || (ddi_get_instance(cdip) == -1) ||
            (MDI_CLIENT_IS_REPORT_DEV_NEEDED(ct) == 0)) {
                return;
        }
        if (MDI_CLIENT_STATE(ct) == MDI_CLIENT_STATE_OPTIMAL) {
                ct_status = "optimal";
                report_lb_c = 1;
        } else if (MDI_CLIENT_STATE(ct) == MDI_CLIENT_STATE_DEGRADED) {
                ct_status = "degraded";
        } else if (MDI_CLIENT_STATE(ct) == MDI_CLIENT_STATE_FAILED) {
                ct_status = "failed";
        } else {
                ct_status = "unknown";
        }

        lb_buf[0] = 0;          /* not interested in load balancing config */

        if (MDI_PI_FLAGS_IS_DEVICE_REMOVED(pip)) {
                status = "removed";
        } else if (MDI_PI_IS_OFFLINE(pip)) {
                status = "offline";
        } else if (MDI_PI_IS_ONLINE(pip)) {
                status = "online";
                report_lb_p = 1;
        } else if (MDI_PI_IS_STANDBY(pip)) {
                status = "standby";
        } else if (MDI_PI_IS_FAULT(pip)) {
                status = "faulted";
        } else {
                status = "unknown";
        }

        if (cdip) {
                ct_path = kmem_alloc(MAXPATHLEN, KM_SLEEP);

                /*
                 * NOTE: Keeping "multipath status: %s" and
                 * "Load balancing: %s" format unchanged in case someone
                 * scrubs /var/adm/messages looking for these messages.
                 */
                if (report_lb_c && report_lb_p) {
                        if (ct->ct_lb == LOAD_BALANCE_LBA) {
                                (void) snprintf(lb_buf, sizeof (lb_buf),
                                    "%s, region-size: %d", mdi_load_balance_lba,
                                    ct->ct_lb_args->region_size);
                        } else if (ct->ct_lb == LOAD_BALANCE_NONE) {
                                (void) snprintf(lb_buf, sizeof (lb_buf),
                                    "%s", mdi_load_balance_none);
                        } else {
                                (void) snprintf(lb_buf, sizeof (lb_buf), "%s",
                                    mdi_load_balance_rr);
                        }

                        cmn_err(mdi_debug_consoleonly ? CE_NOTE : CE_CONT,
                            "?%s (%s%d) multipath status: %s: "
                            "path %d %s is %s: Load balancing: %s\n",
                            ddi_pathname(cdip, ct_path), ddi_driver_name(cdip),
                            ddi_get_instance(cdip), ct_status,
                            mdi_pi_get_path_instance(pip),
                            mdi_pi_spathname(pip), status, lb_buf);
                } else {
                        cmn_err(mdi_debug_consoleonly ? CE_NOTE : CE_CONT,
                            "?%s (%s%d) multipath status: %s: "
                            "path %d %s is %s\n",
                            ddi_pathname(cdip, ct_path), ddi_driver_name(cdip),
                            ddi_get_instance(cdip), ct_status,
                            mdi_pi_get_path_instance(pip),
                            mdi_pi_spathname(pip), status);
                }

                kmem_free(ct_path, MAXPATHLEN);
                MDI_CLIENT_CLEAR_REPORT_DEV_NEEDED(ct);
        }
}

#ifdef  DEBUG
/*
 * i_mdi_log():
 *              Utility function for error message management
 *
 *              NOTE: Implementation takes care of trailing \n for cmn_err,
 *              MDI_DEBUG should not terminate fmt strings with \n.
 *
 *              NOTE: If the level is >= 2, and there is no leading !?^
 *              then a leading ! is implied (but can be overriden via
 *              mdi_debug_consoleonly). If you are using kmdb on the console,
 *              consider setting mdi_debug_consoleonly to 1 as an aid.
 */
/*PRINTFLIKE4*/
static void
i_mdi_log(int level, const char *func, dev_info_t *dip, const char *fmt, ...)
{
        char            name[MAXNAMELEN];
        char            buf[512];
        char            *bp;
        va_list         ap;
        int             log_only = 0;
        int             boot_only = 0;
        int             console_only = 0;

        if (dip) {
                (void) snprintf(name, sizeof(name), "%s%d: ",
                    ddi_driver_name(dip), ddi_get_instance(dip));
        } else {
                name[0] = 0;
        }

        va_start(ap, fmt);
        (void) vsnprintf(buf, sizeof(buf), fmt, ap);
        va_end(ap);

        switch (buf[0]) {
        case '!':
                bp = &buf[1];
                log_only = 1;
                break;
        case '?':
                bp = &buf[1];
                boot_only = 1;
                break;
        case '^':
                bp = &buf[1];
                console_only = 1;
                break;
        default:
                if (level >= 2)
                        log_only = 1;           /* ! implied */
                bp = buf;
                break;
        }
        if (mdi_debug_logonly) {
                log_only = 1;
                boot_only = 0;
                console_only = 0;
        }
        if (mdi_debug_consoleonly) {
                log_only = 0;
                boot_only = 0;
                console_only = 1;
                level = CE_NOTE;
                goto console;
        }

        switch (level) {
        case CE_NOTE:
                level = CE_CONT;
                /* FALLTHROUGH */
        case CE_CONT:
                if (boot_only) {
                        cmn_err(level, "?mdi: %s%s: %s\n", name, func, bp);
                } else if (console_only) {
                        cmn_err(level, "^mdi: %s%s: %s\n", name, func, bp);
                } else if (log_only) {
                        cmn_err(level, "!mdi: %s%s: %s\n", name, func, bp);
                } else {
                        cmn_err(level, "mdi: %s%s: %s\n", name, func, bp);
                }
                break;

        case CE_WARN:
        case CE_PANIC:
        console:
                if (boot_only) {
                        cmn_err(level, "?mdi: %s%s: %s", name, func, bp);
                } else if (console_only) {
                        cmn_err(level, "^mdi: %s%s: %s", name, func, bp);
                } else if (log_only) {
                        cmn_err(level, "!mdi: %s%s: %s", name, func, bp);
                } else {
                        cmn_err(level, "mdi: %s%s: %s", name, func, bp);
                }
                break;
        default:
                cmn_err(level, "mdi: %s%s", name, bp);
                break;
        }
}
#endif  /* DEBUG */

void
i_mdi_client_online(dev_info_t *ct_dip)
{
        mdi_client_t    *ct;

        /*
         * Client online notification. Mark client state as online
         * restore our binding with dev_info node
         */
        ct = i_devi_get_client(ct_dip);
        ASSERT(ct != NULL);
        MDI_CLIENT_LOCK(ct);
        MDI_CLIENT_SET_ONLINE(ct);
        /* catch for any memory leaks */
        ASSERT((ct->ct_dip == NULL) || (ct->ct_dip == ct_dip));
        ct->ct_dip = ct_dip;

        if (ct->ct_power_cnt == 0)
                (void) i_mdi_power_all_phci(ct);

        MDI_DEBUG(4, (MDI_NOTE, ct_dip,
            "i_mdi_pm_hold_client %p", (void *)ct));
        i_mdi_pm_hold_client(ct, 1);

        MDI_CLIENT_UNLOCK(ct);
}

void
i_mdi_phci_online(dev_info_t *ph_dip)
{
        mdi_phci_t      *ph;

        /* pHCI online notification. Mark state accordingly */
        ph = i_devi_get_phci(ph_dip);
        ASSERT(ph != NULL);
        MDI_PHCI_LOCK(ph);
        MDI_PHCI_SET_ONLINE(ph);
        MDI_PHCI_UNLOCK(ph);
}

/*
 * mdi_devi_online():
 *              Online notification from NDI framework on pHCI/client
 *              device online.
 * Return Values:
 *              NDI_SUCCESS
 *              MDI_FAILURE
 */
/*ARGSUSED*/
int
mdi_devi_online(dev_info_t *dip, uint_t flags)
{
        if (MDI_PHCI(dip)) {
                i_mdi_phci_online(dip);
        }

        if (MDI_CLIENT(dip)) {
                i_mdi_client_online(dip);
        }
        return (NDI_SUCCESS);
}

/*
 * mdi_devi_offline():
 *              Offline notification from NDI framework on pHCI/Client device
 *              offline.
 *
 * Return Values:
 *              NDI_SUCCESS
 *              NDI_FAILURE
 */
/*ARGSUSED*/
int
mdi_devi_offline(dev_info_t *dip, uint_t flags)
{
        int             rv = NDI_SUCCESS;

        if (MDI_CLIENT(dip)) {
                rv = i_mdi_client_offline(dip, flags);
                if (rv != NDI_SUCCESS)
                        return (rv);
        }

        if (MDI_PHCI(dip)) {
                rv = i_mdi_phci_offline(dip, flags);

                if ((rv != NDI_SUCCESS) && MDI_CLIENT(dip)) {
                        /* set client back online */
                        i_mdi_client_online(dip);
                }
        }

        return (rv);
}

/*ARGSUSED*/
static int
i_mdi_phci_offline(dev_info_t *dip, uint_t flags)
{
        int             rv = NDI_SUCCESS;
        mdi_phci_t      *ph;
        mdi_client_t    *ct;
        mdi_pathinfo_t  *pip;
        mdi_pathinfo_t  *next;
        mdi_pathinfo_t  *failed_pip = NULL;
        dev_info_t      *cdip;

        /*
         * pHCI component offline notification
         * Make sure that this pHCI instance is free to be offlined.
         * If it is OK to proceed, Offline and remove all the child
         * mdi_pathinfo nodes.  This process automatically offlines
         * corresponding client devices, for which this pHCI provides
         * critical services.
         */
        ph = i_devi_get_phci(dip);
        MDI_DEBUG(2, (MDI_NOTE, dip,
            "called %p %p", (void *)dip, (void *)ph));
        if (ph == NULL) {
                return (rv);
        }

        MDI_PHCI_LOCK(ph);

        if (MDI_PHCI_IS_OFFLINE(ph)) {
                MDI_DEBUG(1, (MDI_WARN, dip,
                    "!pHCI already offlined: %p", (void *)dip));
                MDI_PHCI_UNLOCK(ph);
                return (NDI_SUCCESS);
        }

        /*
         * Check to see if the pHCI can be offlined
         */
        if (ph->ph_unstable) {
                MDI_DEBUG(1, (MDI_WARN, dip,
                    "!One or more target devices are in transient state. "
                    "This device can not be removed at this moment. "
                    "Please try again later."));
                MDI_PHCI_UNLOCK(ph);
                return (NDI_BUSY);
        }

        pip = ph->ph_path_head;
        while (pip != NULL) {
                MDI_PI_LOCK(pip);
                next = (mdi_pathinfo_t *)MDI_PI(pip)->pi_phci_link;

                /*
                 * The mdi_pathinfo state is OK. Check the client state.
                 * If failover in progress fail the pHCI from offlining
                 */
                ct = MDI_PI(pip)->pi_client;
                i_mdi_client_lock(ct, pip);
                if ((MDI_CLIENT_IS_FAILOVER_IN_PROGRESS(ct)) ||
                    (ct->ct_unstable)) {
                        /*
                         * Failover is in progress, Fail the DR
                         */
                        MDI_DEBUG(1, (MDI_WARN, dip,
                            "!pHCI device is busy. "
                            "This device can not be removed at this moment. "
                            "Please try again later."));
                        MDI_PI_UNLOCK(pip);
                        i_mdi_client_unlock(ct);
                        MDI_PHCI_UNLOCK(ph);
                        return (NDI_BUSY);
                }
                MDI_PI_UNLOCK(pip);

                /*
                 * Check to see of we are removing the last path of this
                 * client device...
                 */
                cdip = ct->ct_dip;
                if (cdip && (i_ddi_node_state(cdip) >= DS_INITIALIZED) &&
                    (i_mdi_client_compute_state(ct, ph) ==
                    MDI_CLIENT_STATE_FAILED)) {
                        i_mdi_client_unlock(ct);
                        MDI_PHCI_UNLOCK(ph);
                        if (ndi_devi_offline(cdip,
                            NDI_DEVFS_CLEAN) != NDI_SUCCESS) {
                                /*
                                 * ndi_devi_offline() failed.
                                 * This pHCI provides the critical path
                                 * to one or more client devices.
                                 * Return busy.
                                 */
                                MDI_PHCI_LOCK(ph);
                                MDI_DEBUG(1, (MDI_WARN, dip,
                                    "!pHCI device is busy. "
                                    "This device can not be removed at this "
                                    "moment. Please try again later."));
                                failed_pip = pip;
                                break;
                        } else {
                                MDI_PHCI_LOCK(ph);
                                pip = next;
                        }
                } else {
                        i_mdi_client_unlock(ct);
                        pip = next;
                }
        }

        if (failed_pip) {
                pip = ph->ph_path_head;
                while (pip != failed_pip) {
                        MDI_PI_LOCK(pip);
                        next = (mdi_pathinfo_t *)MDI_PI(pip)->pi_phci_link;
                        ct = MDI_PI(pip)->pi_client;
                        i_mdi_client_lock(ct, pip);
                        cdip = ct->ct_dip;
                        switch (MDI_CLIENT_STATE(ct)) {
                        case MDI_CLIENT_STATE_OPTIMAL:
                        case MDI_CLIENT_STATE_DEGRADED:
                                if (cdip) {
                                        MDI_PI_UNLOCK(pip);
                                        i_mdi_client_unlock(ct);
                                        MDI_PHCI_UNLOCK(ph);
                                        (void) ndi_devi_online(cdip, 0);
                                        MDI_PHCI_LOCK(ph);
                                        pip = next;
                                        continue;
                                }
                                break;

                        case MDI_CLIENT_STATE_FAILED:
                                if (cdip) {
                                        MDI_PI_UNLOCK(pip);
                                        i_mdi_client_unlock(ct);
                                        MDI_PHCI_UNLOCK(ph);
                                        (void) ndi_devi_offline(cdip,
                                                NDI_DEVFS_CLEAN);
                                        MDI_PHCI_LOCK(ph);
                                        pip = next;
                                        continue;
                                }
                                break;
                        }
                        MDI_PI_UNLOCK(pip);
                        i_mdi_client_unlock(ct);
                        pip = next;
                }
                MDI_PHCI_UNLOCK(ph);
                return (NDI_BUSY);
        }

        /*
         * Mark the pHCI as offline
         */
        MDI_PHCI_SET_OFFLINE(ph);

        /*
         * Mark the child mdi_pathinfo nodes as transient
         */
        pip = ph->ph_path_head;
        while (pip != NULL) {
                MDI_PI_LOCK(pip);
                next = (mdi_pathinfo_t *)MDI_PI(pip)->pi_phci_link;
                MDI_PI_SET_OFFLINING(pip);
                MDI_PI_UNLOCK(pip);
                pip = next;
        }
        MDI_PHCI_UNLOCK(ph);
        /*
         * Give a chance for any pending commands to execute
         */
        delay_random(mdi_delay);
        MDI_PHCI_LOCK(ph);
        pip = ph->ph_path_head;
        while (pip != NULL) {
                next = (mdi_pathinfo_t *)MDI_PI(pip)->pi_phci_link;
                (void) i_mdi_pi_offline(pip, flags);
                MDI_PI_LOCK(pip);
                ct = MDI_PI(pip)->pi_client;
                if (!MDI_PI_IS_OFFLINE(pip)) {
                        MDI_DEBUG(1, (MDI_WARN, dip,
                            "!pHCI device is busy. "
                            "This device can not be removed at this moment. "
                            "Please try again later."));
                        MDI_PI_UNLOCK(pip);
                        MDI_PHCI_SET_ONLINE(ph);
                        MDI_PHCI_UNLOCK(ph);
                        return (NDI_BUSY);
                }
                MDI_PI_UNLOCK(pip);
                pip = next;
        }
        MDI_PHCI_UNLOCK(ph);

        return (rv);
}

void
mdi_phci_mark_retiring(dev_info_t *dip, char **cons_array)
{
        mdi_phci_t      *ph;
        mdi_client_t    *ct;
        mdi_pathinfo_t  *pip;
        mdi_pathinfo_t  *next;
        dev_info_t      *cdip;

        if (!MDI_PHCI(dip))
                return;

        ph = i_devi_get_phci(dip);
        if (ph == NULL) {
                return;
        }

        MDI_PHCI_LOCK(ph);

        if (MDI_PHCI_IS_OFFLINE(ph)) {
                /* has no last path */
                MDI_PHCI_UNLOCK(ph);
                return;
        }

        pip = ph->ph_path_head;
        while (pip != NULL) {
                MDI_PI_LOCK(pip);
                next = (mdi_pathinfo_t *)MDI_PI(pip)->pi_phci_link;

                ct = MDI_PI(pip)->pi_client;
                i_mdi_client_lock(ct, pip);
                MDI_PI_UNLOCK(pip);

                cdip = ct->ct_dip;
                if (cdip && (i_ddi_node_state(cdip) >= DS_INITIALIZED) &&
                    (i_mdi_client_compute_state(ct, ph) ==
                    MDI_CLIENT_STATE_FAILED)) {
                        /* Last path. Mark client dip as retiring */
                        i_mdi_client_unlock(ct);
                        MDI_PHCI_UNLOCK(ph);
                        (void) e_ddi_mark_retiring(cdip, cons_array);
                        MDI_PHCI_LOCK(ph);
                        pip = next;
                } else {
                        i_mdi_client_unlock(ct);
                        pip = next;
                }
        }

        MDI_PHCI_UNLOCK(ph);

        return;
}

void
mdi_phci_retire_notify(dev_info_t *dip, int *constraint)
{
        mdi_phci_t      *ph;
        mdi_client_t    *ct;
        mdi_pathinfo_t  *pip;
        mdi_pathinfo_t  *next;
        dev_info_t      *cdip;

        if (!MDI_PHCI(dip))
                return;

        ph = i_devi_get_phci(dip);
        if (ph == NULL)
                return;

        MDI_PHCI_LOCK(ph);

        if (MDI_PHCI_IS_OFFLINE(ph)) {
                MDI_PHCI_UNLOCK(ph);
                /* not last path */
                return;
        }

        if (ph->ph_unstable) {
                MDI_PHCI_UNLOCK(ph);
                /* can't check for constraints */
                *constraint = 0;
                return;
        }

        pip = ph->ph_path_head;
        while (pip != NULL) {
                MDI_PI_LOCK(pip);
                next = (mdi_pathinfo_t *)MDI_PI(pip)->pi_phci_link;

                /*
                 * The mdi_pathinfo state is OK. Check the client state.
                 * If failover in progress fail the pHCI from offlining
                 */
                ct = MDI_PI(pip)->pi_client;
                i_mdi_client_lock(ct, pip);
                if ((MDI_CLIENT_IS_FAILOVER_IN_PROGRESS(ct)) ||
                    (ct->ct_unstable)) {
                        /*
                         * Failover is in progress, can't check for constraints
                         */
                        MDI_PI_UNLOCK(pip);
                        i_mdi_client_unlock(ct);
                        MDI_PHCI_UNLOCK(ph);
                        *constraint = 0;
                        return;
                }
                MDI_PI_UNLOCK(pip);

                /*
                 * Check to see of we are retiring the last path of this
                 * client device...
                 */
                cdip = ct->ct_dip;
                if (cdip && (i_ddi_node_state(cdip) >= DS_INITIALIZED) &&
                    (i_mdi_client_compute_state(ct, ph) ==
                    MDI_CLIENT_STATE_FAILED)) {
                        i_mdi_client_unlock(ct);
                        MDI_PHCI_UNLOCK(ph);
                        (void) e_ddi_retire_notify(cdip, constraint);
                        MDI_PHCI_LOCK(ph);
                        pip = next;
                } else {
                        i_mdi_client_unlock(ct);
                        pip = next;
                }
        }

        MDI_PHCI_UNLOCK(ph);

        return;
}

/*
 * offline the path(s) hanging off the pHCI. If the
 * last path to any client, check that constraints
 * have been applied.
 *
 * If constraint is 0, we aren't going to retire the
 * pHCI. However we still need to go through the paths
 * calling e_ddi_retire_finalize() to clear their
 * contract barriers.
 */
void
mdi_phci_retire_finalize(dev_info_t *dip, int phci_only, void *constraint)
{
        mdi_phci_t      *ph;
        mdi_client_t    *ct;
        mdi_pathinfo_t  *pip;
        mdi_pathinfo_t  *next;
        dev_info_t      *cdip;
        int             unstable = 0;
        int             tmp_constraint;

        if (!MDI_PHCI(dip))
                return;

        ph = i_devi_get_phci(dip);
        if (ph == NULL) {
                /* no last path and no pips */
                return;
        }

        MDI_PHCI_LOCK(ph);

        if (MDI_PHCI_IS_OFFLINE(ph)) {
                MDI_PHCI_UNLOCK(ph);
                /* no last path and no pips */
                return;
        }

        /*
         * Check to see if the pHCI can be offlined
         */
        if (ph->ph_unstable) {
                unstable = 1;
        }

        pip = ph->ph_path_head;
        while (pip != NULL) {
                MDI_PI_LOCK(pip);
                next = (mdi_pathinfo_t *)MDI_PI(pip)->pi_phci_link;

                /*
                 * if failover in progress fail the pHCI from offlining
                 */
                ct = MDI_PI(pip)->pi_client;
                i_mdi_client_lock(ct, pip);
                if ((MDI_CLIENT_IS_FAILOVER_IN_PROGRESS(ct)) ||
                    (ct->ct_unstable)) {
                        unstable = 1;
                }
                MDI_PI_UNLOCK(pip);

                /*
                 * Check to see of we are removing the last path of this
                 * client device...
                 */
                cdip = ct->ct_dip;
                if (!phci_only && cdip &&
                    (i_ddi_node_state(cdip) >= DS_INITIALIZED) &&
                    (i_mdi_client_compute_state(ct, ph) ==
                    MDI_CLIENT_STATE_FAILED)) {
                        i_mdi_client_unlock(ct);
                        MDI_PHCI_UNLOCK(ph);
                        /*
                         * This is the last path to this client.
                         *
                         * Constraint will only be set to 1 if this client can
                         * be retired (as already determined by
                         * mdi_phci_retire_notify). However we don't actually
                         * need to retire the client (we just retire the last
                         * path - MPXIO will then fail all I/Os to the client).
                         * But we still need to call e_ddi_retire_finalize so
                         * the contract barriers can be cleared. Therefore we
                         * temporarily set constraint = 0 so that the client
                         * dip is not retired.
                         */
                        tmp_constraint = 0;
                        (void) e_ddi_retire_finalize(cdip, &tmp_constraint);
                        MDI_PHCI_LOCK(ph);
                        pip = next;
                } else {
                        i_mdi_client_unlock(ct);
                        pip = next;
                }
        }

        if (!phci_only && *((int *)constraint) == 0) {
                MDI_PHCI_UNLOCK(ph);
                return;
        }

        /*
         * Cannot offline pip(s)
         */
        if (unstable) {
                cmn_err(CE_WARN, "%s%d: mdi_phci_retire_finalize: "
                    "pHCI in transient state, cannot retire",
                    ddi_driver_name(dip), ddi_get_instance(dip));
                MDI_PHCI_UNLOCK(ph);
                return;
        }

        /*
         * Mark the pHCI as offline
         */
        MDI_PHCI_SET_OFFLINE(ph);

        /*
         * Mark the child mdi_pathinfo nodes as transient
         */
        pip = ph->ph_path_head;
        while (pip != NULL) {
                MDI_PI_LOCK(pip);
                next = (mdi_pathinfo_t *)MDI_PI(pip)->pi_phci_link;
                MDI_PI_SET_OFFLINING(pip);
                MDI_PI_UNLOCK(pip);
                pip = next;
        }
        MDI_PHCI_UNLOCK(ph);
        /*
         * Give a chance for any pending commands to execute
         */
        delay_random(mdi_delay);
        MDI_PHCI_LOCK(ph);
        pip = ph->ph_path_head;
        while (pip != NULL) {
                next = (mdi_pathinfo_t *)MDI_PI(pip)->pi_phci_link;
                (void) i_mdi_pi_offline(pip, 0);
                MDI_PI_LOCK(pip);
                ct = MDI_PI(pip)->pi_client;
                if (!MDI_PI_IS_OFFLINE(pip)) {
                        cmn_err(CE_WARN, "mdi_phci_retire_finalize: "
                            "path %d %s busy, cannot offline",
                            mdi_pi_get_path_instance(pip),
                            mdi_pi_spathname(pip));
                        MDI_PI_UNLOCK(pip);
                        MDI_PHCI_SET_ONLINE(ph);
                        MDI_PHCI_UNLOCK(ph);
                        return;
                }
                MDI_PI_UNLOCK(pip);
                pip = next;
        }
        MDI_PHCI_UNLOCK(ph);

        return;
}

void
mdi_phci_unretire(dev_info_t *dip)
{
        mdi_phci_t      *ph;
        mdi_pathinfo_t  *pip;
        mdi_pathinfo_t  *next;

        ASSERT(MDI_PHCI(dip));

        /*
         * Online the phci
         */
        i_mdi_phci_online(dip);

        ph = i_devi_get_phci(dip);
        MDI_PHCI_LOCK(ph);
        pip = ph->ph_path_head;
        while (pip != NULL) {
                MDI_PI_LOCK(pip);
                next = (mdi_pathinfo_t *)MDI_PI(pip)->pi_phci_link;
                MDI_PI_UNLOCK(pip);
                (void) i_mdi_pi_online(pip, 0);
                pip = next;
        }
        MDI_PHCI_UNLOCK(ph);
}

/*ARGSUSED*/
static int
i_mdi_client_offline(dev_info_t *dip, uint_t flags)
{
        int             rv = NDI_SUCCESS;
        mdi_client_t    *ct;

        /*
         * Client component to go offline.  Make sure that we are
         * not in failing over state and update client state
         * accordingly
         */
        ct = i_devi_get_client(dip);
        MDI_DEBUG(2, (MDI_NOTE, dip,
            "called %p %p", (void *)dip, (void *)ct));
        if (ct != NULL) {
                MDI_CLIENT_LOCK(ct);
                if (ct->ct_unstable) {
                        /*
                         * One or more paths are in transient state,
                         * Dont allow offline of a client device
                         */
                        MDI_DEBUG(1, (MDI_WARN, dip,
                            "!One or more paths to "
                            "this device are in transient state. "
                            "This device can not be removed at this moment. "
                            "Please try again later."));
                        MDI_CLIENT_UNLOCK(ct);
                        return (NDI_BUSY);
                }
                if (MDI_CLIENT_IS_FAILOVER_IN_PROGRESS(ct)) {
                        /*
                         * Failover is in progress, Dont allow DR of
                         * a client device
                         */
                        MDI_DEBUG(1, (MDI_WARN, dip,
                            "!Client device is Busy. "
                            "This device can not be removed at this moment. "
                            "Please try again later."));
                        MDI_CLIENT_UNLOCK(ct);
                        return (NDI_BUSY);
                }
                MDI_CLIENT_SET_OFFLINE(ct);

                /*
                 * Unbind our relationship with the dev_info node
                 */
                if (flags & NDI_DEVI_REMOVE) {
                        ct->ct_dip = NULL;
                }
                MDI_CLIENT_UNLOCK(ct);
        }
        return (rv);
}

/*
 * mdi_pre_attach():
 *              Pre attach() notification handler
 */
/*ARGSUSED*/
int
mdi_pre_attach(dev_info_t *dip, ddi_attach_cmd_t cmd)
{
        /* don't support old DDI_PM_RESUME */
        if ((DEVI(dip)->devi_mdi_component != MDI_COMPONENT_NONE) &&
            (cmd == DDI_PM_RESUME))
                return (DDI_FAILURE);

        return (DDI_SUCCESS);
}

/*
 * mdi_post_attach():
 *              Post attach() notification handler
 */
/*ARGSUSED*/
void
mdi_post_attach(dev_info_t *dip, ddi_attach_cmd_t cmd, int error)
{
        mdi_phci_t      *ph;
        mdi_client_t    *ct;
        mdi_vhci_t      *vh;

        if (MDI_PHCI(dip)) {
                ph = i_devi_get_phci(dip);
                ASSERT(ph != NULL);

                MDI_PHCI_LOCK(ph);
                switch (cmd) {
                case DDI_ATTACH:
                        MDI_DEBUG(2, (MDI_NOTE, dip,
                            "phci post_attach called %p", (void *)ph));
                        if (error == DDI_SUCCESS) {
                                MDI_PHCI_SET_ATTACH(ph);
                        } else {
                                MDI_DEBUG(1, (MDI_NOTE, dip,
                                    "!pHCI post_attach failed: error %d",
                                    error));
                                MDI_PHCI_SET_DETACH(ph);
                        }
                        break;

                case DDI_RESUME:
                        MDI_DEBUG(2, (MDI_NOTE, dip,
                            "pHCI post_resume: called %p", (void *)ph));
                        if (error == DDI_SUCCESS) {
                                MDI_PHCI_SET_RESUME(ph);
                        } else {
                                MDI_DEBUG(1, (MDI_NOTE, dip,
                                    "!pHCI post_resume failed: error %d",
                                    error));
                                MDI_PHCI_SET_SUSPEND(ph);
                        }
                        break;
                }
                MDI_PHCI_UNLOCK(ph);
        }

        if (MDI_CLIENT(dip)) {
                ct = i_devi_get_client(dip);
                ASSERT(ct != NULL);

                MDI_CLIENT_LOCK(ct);
                switch (cmd) {
                case DDI_ATTACH:
                        MDI_DEBUG(2, (MDI_NOTE, dip,
                            "client post_attach called %p", (void *)ct));
                        if (error != DDI_SUCCESS) {
                                MDI_DEBUG(1, (MDI_NOTE, dip,
                                    "!client post_attach failed: error %d",
                                    error));
                                MDI_CLIENT_SET_DETACH(ct);
                                MDI_DEBUG(4, (MDI_WARN, dip,
                                    "i_mdi_pm_reset_client"));
                                i_mdi_pm_reset_client(ct);
                                break;
                        }

                        /*
                         * Client device has successfully attached, inform
                         * the vhci.
                         */
                        vh = ct->ct_vhci;
                        if (vh->vh_ops->vo_client_attached)
                                (*vh->vh_ops->vo_client_attached)(dip);

                        MDI_CLIENT_SET_ATTACH(ct);
                        break;

                case DDI_RESUME:
                        MDI_DEBUG(2, (MDI_NOTE, dip,
                            "client post_attach: called %p", (void *)ct));
                        if (error == DDI_SUCCESS) {
                                MDI_CLIENT_SET_RESUME(ct);
                        } else {
                                MDI_DEBUG(1, (MDI_NOTE, dip,
                                    "!client post_resume failed: error %d",
                                    error));
                                MDI_CLIENT_SET_SUSPEND(ct);
                        }
                        break;
                }
                MDI_CLIENT_UNLOCK(ct);
        }
}

/*
 * mdi_pre_detach():
 *              Pre detach notification handler
 */
/*ARGSUSED*/
int
mdi_pre_detach(dev_info_t *dip, ddi_detach_cmd_t cmd)
{
        int rv = DDI_SUCCESS;

        if (MDI_CLIENT(dip)) {
                (void) i_mdi_client_pre_detach(dip, cmd);
        }

        if (MDI_PHCI(dip)) {
                rv = i_mdi_phci_pre_detach(dip, cmd);
        }

        return (rv);
}

/*ARGSUSED*/
static int
i_mdi_phci_pre_detach(dev_info_t *dip, ddi_detach_cmd_t cmd)
{
        int             rv = DDI_SUCCESS;
        mdi_phci_t      *ph;
        mdi_client_t    *ct;
        mdi_pathinfo_t  *pip;
        mdi_pathinfo_t  *failed_pip = NULL;
        mdi_pathinfo_t  *next;

        ph = i_devi_get_phci(dip);
        if (ph == NULL) {
                return (rv);
        }

        MDI_PHCI_LOCK(ph);
        switch (cmd) {
        case DDI_DETACH:
                MDI_DEBUG(2, (MDI_NOTE, dip,
                    "pHCI pre_detach: called %p", (void *)ph));
                if (!MDI_PHCI_IS_OFFLINE(ph)) {
                        /*
                         * mdi_pathinfo nodes are still attached to
                         * this pHCI. Fail the detach for this pHCI.
                         */
                        MDI_DEBUG(2, (MDI_WARN, dip,
                            "pHCI pre_detach: paths are still attached %p",
                            (void *)ph));
                        rv = DDI_FAILURE;
                        break;
                }
                MDI_PHCI_SET_DETACH(ph);
                break;

        case DDI_SUSPEND:
                /*
                 * pHCI is getting suspended.  Since mpxio client
                 * devices may not be suspended at this point, to avoid
                 * a potential stack overflow, it is important to suspend
                 * client devices before pHCI can be suspended.
                 */

                MDI_DEBUG(2, (MDI_NOTE, dip,
                    "pHCI pre_suspend: called %p", (void *)ph));
                /*
                 * Suspend all the client devices accessible through this pHCI
                 */
                pip = ph->ph_path_head;
                while (pip != NULL && rv == DDI_SUCCESS) {
                        dev_info_t *cdip;
                        MDI_PI_LOCK(pip);
                        next =
                            (mdi_pathinfo_t *)MDI_PI(pip)->pi_phci_link;
                        ct = MDI_PI(pip)->pi_client;
                        i_mdi_client_lock(ct, pip);
                        cdip = ct->ct_dip;
                        MDI_PI_UNLOCK(pip);
                        if ((MDI_CLIENT_IS_DETACHED(ct) == 0) &&
                            MDI_CLIENT_IS_SUSPENDED(ct) == 0) {
                                i_mdi_client_unlock(ct);
                                if ((rv = devi_detach(cdip, DDI_SUSPEND)) !=
                                    DDI_SUCCESS) {
                                        /*
                                         * Suspend of one of the client
                                         * device has failed.
                                         */
                                        MDI_DEBUG(1, (MDI_WARN, dip,
                                            "!suspend of device (%s%d) failed.",
                                            ddi_driver_name(cdip),
                                            ddi_get_instance(cdip)));
                                        failed_pip = pip;
                                        break;
                                }
                        } else {
                                i_mdi_client_unlock(ct);
                        }
                        pip = next;
                }

                if (rv == DDI_SUCCESS) {
                        /*
                         * Suspend of client devices is complete. Proceed
                         * with pHCI suspend.
                         */
                        MDI_PHCI_SET_SUSPEND(ph);
                } else {
                        /*
                         * Revert back all the suspended client device states
                         * to converse.
                         */
                        pip = ph->ph_path_head;
                        while (pip != failed_pip) {
                                dev_info_t *cdip;
                                MDI_PI_LOCK(pip);
                                next =
                                    (mdi_pathinfo_t *)MDI_PI(pip)->pi_phci_link;
                                ct = MDI_PI(pip)->pi_client;
                                i_mdi_client_lock(ct, pip);
                                cdip = ct->ct_dip;
                                MDI_PI_UNLOCK(pip);
                                if (MDI_CLIENT_IS_SUSPENDED(ct)) {
                                        i_mdi_client_unlock(ct);
                                        (void) devi_attach(cdip, DDI_RESUME);
                                } else {
                                        i_mdi_client_unlock(ct);
                                }
                                pip = next;
                        }
                }
                break;

        default:
                rv = DDI_FAILURE;
                break;
        }
        MDI_PHCI_UNLOCK(ph);
        return (rv);
}

/*ARGSUSED*/
static int
i_mdi_client_pre_detach(dev_info_t *dip, ddi_detach_cmd_t cmd)
{
        int             rv = DDI_SUCCESS;
        mdi_client_t    *ct;

        ct = i_devi_get_client(dip);
        if (ct == NULL) {
                return (rv);
        }

        MDI_CLIENT_LOCK(ct);
        switch (cmd) {
        case DDI_DETACH:
                MDI_DEBUG(2, (MDI_NOTE, dip,
                    "client pre_detach: called %p",
                     (void *)ct));
                MDI_CLIENT_SET_DETACH(ct);
                break;

        case DDI_SUSPEND:
                MDI_DEBUG(2, (MDI_NOTE, dip,
                    "client pre_suspend: called %p",
                    (void *)ct));
                MDI_CLIENT_SET_SUSPEND(ct);
                break;

        default:
                rv = DDI_FAILURE;
                break;
        }
        MDI_CLIENT_UNLOCK(ct);
        return (rv);
}

/*
 * mdi_post_detach():
 *              Post detach notification handler
 */
/*ARGSUSED*/
void
mdi_post_detach(dev_info_t *dip, ddi_detach_cmd_t cmd, int error)
{
        /*
         * Detach/Suspend of mpxio component failed. Update our state
         * too
         */
        if (MDI_PHCI(dip))
                i_mdi_phci_post_detach(dip, cmd, error);

        if (MDI_CLIENT(dip))
                i_mdi_client_post_detach(dip, cmd, error);
}

/*ARGSUSED*/
static void
i_mdi_phci_post_detach(dev_info_t *dip, ddi_detach_cmd_t cmd, int error)
{
        mdi_phci_t      *ph;

        /*
         * Detach/Suspend of phci component failed. Update our state
         * too
         */
        ph = i_devi_get_phci(dip);
        if (ph == NULL) {
                return;
        }

        MDI_PHCI_LOCK(ph);
        /*
         * Detach of pHCI failed. Restore back converse
         * state
         */
        switch (cmd) {
        case DDI_DETACH:
                MDI_DEBUG(2, (MDI_NOTE, dip,
                    "pHCI post_detach: called %p",
                    (void *)ph));
                if (error != DDI_SUCCESS)
                        MDI_PHCI_SET_ATTACH(ph);
                break;

        case DDI_SUSPEND:
                MDI_DEBUG(2, (MDI_NOTE, dip,
                    "pHCI post_suspend: called %p",
                    (void *)ph));
                if (error != DDI_SUCCESS)
                        MDI_PHCI_SET_RESUME(ph);
                break;
        }
        MDI_PHCI_UNLOCK(ph);
}

/*ARGSUSED*/
static void
i_mdi_client_post_detach(dev_info_t *dip, ddi_detach_cmd_t cmd, int error)
{
        mdi_client_t    *ct;

        ct = i_devi_get_client(dip);
        if (ct == NULL) {
                return;
        }
        MDI_CLIENT_LOCK(ct);
        /*
         * Detach of Client failed. Restore back converse
         * state
         */
        switch (cmd) {
        case DDI_DETACH:
                MDI_DEBUG(2, (MDI_NOTE, dip,
                    "client post_detach: called %p", (void *)ct));
                if (DEVI_IS_ATTACHING(dip)) {
                        MDI_DEBUG(4, (MDI_NOTE, dip,
                            "i_mdi_pm_rele_client\n"));
                        i_mdi_pm_rele_client(ct, ct->ct_path_count);
                } else {
                        MDI_DEBUG(4, (MDI_NOTE, dip,
                            "i_mdi_pm_reset_client\n"));
                        i_mdi_pm_reset_client(ct);
                }
                if (error != DDI_SUCCESS)
                        MDI_CLIENT_SET_ATTACH(ct);
                break;

        case DDI_SUSPEND:
                MDI_DEBUG(2, (MDI_NOTE, dip,
                    "called %p", (void *)ct));
                if (error != DDI_SUCCESS)
                        MDI_CLIENT_SET_RESUME(ct);
                break;
        }
        MDI_CLIENT_UNLOCK(ct);
}

int
mdi_pi_kstat_exists(mdi_pathinfo_t *pip)
{
        return (MDI_PI(pip)->pi_kstats ? 1 : 0);
}

/*
 * create and install per-path (client - pHCI) statistics
 * I/O stats supported: nread, nwritten, reads, and writes
 * Error stats - hard errors, soft errors, & transport errors
 */
int
mdi_pi_kstat_create(mdi_pathinfo_t *pip, char *ksname)
{
        kstat_t                 *kiosp, *kerrsp;
        struct pi_errs          *nsp;
        struct mdi_pi_kstats    *mdi_statp;

        if (MDI_PI(pip)->pi_kstats != NULL)
                return (MDI_SUCCESS);

        if ((kiosp = kstat_create("mdi", 0, ksname, "iopath",
            KSTAT_TYPE_IO, 1, KSTAT_FLAG_PERSISTENT)) == NULL) {
                return (MDI_FAILURE);
        }

        (void) strcat(ksname, ",err");
        kerrsp = kstat_create("mdi", 0, ksname, "iopath_errors",
            KSTAT_TYPE_NAMED,
            sizeof (struct pi_errs) / sizeof (kstat_named_t), 0);
        if (kerrsp == NULL) {
                kstat_delete(kiosp);
                return (MDI_FAILURE);
        }

        nsp = (struct pi_errs *)kerrsp->ks_data;
        kstat_named_init(&nsp->pi_softerrs, "Soft Errors", KSTAT_DATA_UINT32);
        kstat_named_init(&nsp->pi_harderrs, "Hard Errors", KSTAT_DATA_UINT32);
        kstat_named_init(&nsp->pi_transerrs, "Transport Errors",
            KSTAT_DATA_UINT32);
        kstat_named_init(&nsp->pi_icnt_busy, "Interconnect Busy",
            KSTAT_DATA_UINT32);
        kstat_named_init(&nsp->pi_icnt_errors, "Interconnect Errors",
            KSTAT_DATA_UINT32);
        kstat_named_init(&nsp->pi_phci_rsrc, "pHCI No Resources",
            KSTAT_DATA_UINT32);
        kstat_named_init(&nsp->pi_phci_localerr, "pHCI Local Errors",
            KSTAT_DATA_UINT32);
        kstat_named_init(&nsp->pi_phci_invstate, "pHCI Invalid State",
            KSTAT_DATA_UINT32);
        kstat_named_init(&nsp->pi_failedfrom, "Failed From",
            KSTAT_DATA_UINT32);
        kstat_named_init(&nsp->pi_failedto, "Failed To", KSTAT_DATA_UINT32);

        mdi_statp = kmem_alloc(sizeof (*mdi_statp), KM_SLEEP);
        mdi_statp->pi_kstat_ref = 1;
        mdi_statp->pi_kstat_iostats = kiosp;
        mdi_statp->pi_kstat_errstats = kerrsp;
        kstat_install(kiosp);
        kstat_install(kerrsp);
        MDI_PI(pip)->pi_kstats = mdi_statp;
        return (MDI_SUCCESS);
}

/*
 * destroy per-path properties
 */
static void
i_mdi_pi_kstat_destroy(mdi_pathinfo_t *pip)
{

        struct mdi_pi_kstats *mdi_statp;

        if (MDI_PI(pip)->pi_kstats == NULL)
                return;
        if ((mdi_statp = MDI_PI(pip)->pi_kstats) == NULL)
                return;

        MDI_PI(pip)->pi_kstats = NULL;

        /*
         * the kstat may be shared between multiple pathinfo nodes
         * decrement this pathinfo's usage, removing the kstats
         * themselves when the last pathinfo reference is removed.
         */
        ASSERT(mdi_statp->pi_kstat_ref > 0);
        if (--mdi_statp->pi_kstat_ref != 0)
                return;

        kstat_delete(mdi_statp->pi_kstat_iostats);
        kstat_delete(mdi_statp->pi_kstat_errstats);
        kmem_free(mdi_statp, sizeof (*mdi_statp));
}

/*
 * update I/O paths KSTATS
 */
void
mdi_pi_kstat_iosupdate(mdi_pathinfo_t *pip, struct buf *bp)
{
        kstat_t *iostatp;
        size_t xfer_cnt;

        ASSERT(pip != NULL);

        /*
         * I/O can be driven across a path prior to having path
         * statistics available, i.e. probe(9e).
         */
        if (bp != NULL && MDI_PI(pip)->pi_kstats != NULL) {
                iostatp = MDI_PI(pip)->pi_kstats->pi_kstat_iostats;
                xfer_cnt = bp->b_bcount - bp->b_resid;
                if (bp->b_flags & B_READ) {
                        KSTAT_IO_PTR(iostatp)->reads++;
                        KSTAT_IO_PTR(iostatp)->nread += xfer_cnt;
                } else {
                        KSTAT_IO_PTR(iostatp)->writes++;
                        KSTAT_IO_PTR(iostatp)->nwritten += xfer_cnt;
                }
        }
}

/*
 * Enable the path(specific client/target/initiator)
 * Enabling a path means that MPxIO may select the enabled path for routing
 * future I/O requests, subject to other path state constraints.
 */
int
mdi_pi_enable_path(mdi_pathinfo_t *pip, int flags)
{
        mdi_phci_t      *ph;

        ph = MDI_PI(pip)->pi_phci;
        if (ph == NULL) {
                MDI_DEBUG(1, (MDI_NOTE, mdi_pi_get_phci(pip),
                    "!failed: path %s %p: NULL ph",
                    mdi_pi_spathname(pip), (void *)pip));
                return (MDI_FAILURE);
        }

        (void) i_mdi_enable_disable_path(pip, ph->ph_vhci, flags,
                MDI_ENABLE_OP);
        MDI_DEBUG(5, (MDI_NOTE, ph->ph_dip,
            "!returning success pip = %p. ph = %p",
            (void *)pip, (void *)ph));
        return (MDI_SUCCESS);

}

/*
 * Disable the path (specific client/target/initiator)
 * Disabling a path means that MPxIO will not select the disabled path for
 * routing any new I/O requests.
 */
int
mdi_pi_disable_path(mdi_pathinfo_t *pip, int flags)
{
        mdi_phci_t      *ph;

        ph = MDI_PI(pip)->pi_phci;
        if (ph == NULL) {
                MDI_DEBUG(1, (MDI_NOTE, mdi_pi_get_phci(pip),
                    "!failed: path %s %p: NULL ph",
                    mdi_pi_spathname(pip), (void *)pip));
                return (MDI_FAILURE);
        }

        (void) i_mdi_enable_disable_path(pip,
            ph->ph_vhci, flags, MDI_DISABLE_OP);
        MDI_DEBUG(5, (MDI_NOTE, ph->ph_dip,
            "!returning success pip = %p. ph = %p",
            (void *)pip, (void *)ph));
        return (MDI_SUCCESS);
}

/*
 * disable the path to a particular pHCI (pHCI specified in the phci_path
 * argument) for a particular client (specified in the client_path argument).
 * Disabling a path means that MPxIO will not select the disabled path for
 * routing any new I/O requests.
 * NOTE: this will be removed once the NWS files are changed to use the new
 * mdi_{enable,disable}_path interfaces
 */
int
mdi_pi_disable(dev_info_t *cdip, dev_info_t *pdip, int flags)
{
        return (i_mdi_pi_enable_disable(cdip, pdip, flags, MDI_DISABLE_OP));
}

/*
 * Enable the path to a particular pHCI (pHCI specified in the phci_path
 * argument) for a particular client (specified in the client_path argument).
 * Enabling a path means that MPxIO may select the enabled path for routing
 * future I/O requests, subject to other path state constraints.
 * NOTE: this will be removed once the NWS files are changed to use the new
 * mdi_{enable,disable}_path interfaces
 */

int
mdi_pi_enable(dev_info_t *cdip, dev_info_t *pdip, int flags)
{
        return (i_mdi_pi_enable_disable(cdip, pdip, flags, MDI_ENABLE_OP));
}

/*
 * Common routine for doing enable/disable.
 */
static mdi_pathinfo_t *
i_mdi_enable_disable_path(mdi_pathinfo_t *pip, mdi_vhci_t *vh, int flags,
                int op)
{
        int             sync_flag = 0;
        int             rv;
        mdi_pathinfo_t  *next;
        int             (*f)() = NULL;

        /*
         * Check to make sure the path is not already in the
         * requested state. If it is just return the next path
         * as we have nothing to do here.
         */
        if ((MDI_PI_IS_DISABLE(pip) && op == MDI_DISABLE_OP) ||
            (!MDI_PI_IS_DISABLE(pip) && op == MDI_ENABLE_OP)) {
                MDI_PI_LOCK(pip);
                next = (mdi_pathinfo_t *)MDI_PI(pip)->pi_phci_link;
                MDI_PI_UNLOCK(pip);
                return (next);
        }

        f = vh->vh_ops->vo_pi_state_change;

        sync_flag = (flags << 8) & 0xf00;

        /*
         * Do a callback into the mdi consumer to let it
         * know that path is about to get enabled/disabled.
         */
        if (f != NULL) {
                rv = (*f)(vh->vh_dip, pip, 0,
                        MDI_PI_EXT_STATE(pip),
                        MDI_EXT_STATE_CHANGE | sync_flag |
                        op | MDI_BEFORE_STATE_CHANGE);
                if (rv != MDI_SUCCESS) {
                        MDI_DEBUG(2, (MDI_WARN, vh->vh_dip,
                            "vo_pi_state_change: failed rv = %x", rv));
                }
        }
        MDI_PI_LOCK(pip);
        next = (mdi_pathinfo_t *)MDI_PI(pip)->pi_phci_link;

        switch (flags) {
                case USER_DISABLE:
                        if (op == MDI_DISABLE_OP) {
                                MDI_PI_SET_USER_DISABLE(pip);
                        } else {
                                MDI_PI_SET_USER_ENABLE(pip);
                        }
                        break;
                case DRIVER_DISABLE:
                        if (op == MDI_DISABLE_OP) {
                                MDI_PI_SET_DRV_DISABLE(pip);
                        } else {
                                MDI_PI_SET_DRV_ENABLE(pip);
                        }
                        break;
                case DRIVER_DISABLE_TRANSIENT:
                        if (op == MDI_DISABLE_OP && rv == MDI_SUCCESS) {
                                MDI_PI_SET_DRV_DISABLE_TRANS(pip);
                        } else {
                                MDI_PI_SET_DRV_ENABLE_TRANS(pip);
                        }
                        break;
        }
        MDI_PI_UNLOCK(pip);
        /*
         * Do a callback into the mdi consumer to let it
         * know that path is now enabled/disabled.
         */
        if (f != NULL) {
                rv = (*f)(vh->vh_dip, pip, 0,
                        MDI_PI_EXT_STATE(pip),
                        MDI_EXT_STATE_CHANGE | sync_flag |
                        op | MDI_AFTER_STATE_CHANGE);
                if (rv != MDI_SUCCESS) {
                        MDI_DEBUG(2, (MDI_WARN, vh->vh_dip,
                            "vo_pi_state_change failed: rv = %x", rv));
                }
        }
        return (next);
}

/*
 * Common routine for doing enable/disable.
 * NOTE: this will be removed once the NWS files are changed to use the new
 * mdi_{enable,disable}_path has been putback
 */
int
i_mdi_pi_enable_disable(dev_info_t *cdip, dev_info_t *pdip, int flags, int op)
{

        mdi_phci_t      *ph;
        mdi_vhci_t      *vh = NULL;
        mdi_client_t    *ct;
        mdi_pathinfo_t  *next, *pip;
        int             found_it;

        ph = i_devi_get_phci(pdip);
        MDI_DEBUG(5, (MDI_NOTE, cdip ? cdip : pdip,
            "!op = %d pdip = %p cdip = %p", op, (void *)pdip,
            (void *)cdip));
        if (ph == NULL) {
                MDI_DEBUG(1, (MDI_NOTE, cdip ? cdip : pdip,
                    "!failed: operation %d: NULL ph", op));
                return (MDI_FAILURE);
        }

        if ((op != MDI_ENABLE_OP) && (op != MDI_DISABLE_OP)) {
                MDI_DEBUG(1, (MDI_NOTE, cdip ? cdip : pdip,
                    "!failed: invalid operation %d", op));
                return (MDI_FAILURE);
        }

        vh = ph->ph_vhci;

        if (cdip == NULL) {
                /*
                 * Need to mark the Phci as enabled/disabled.
                 */
                MDI_DEBUG(4, (MDI_NOTE, cdip ? cdip : pdip,
                    "op %d for the phci", op));
                MDI_PHCI_LOCK(ph);
                switch (flags) {
                        case USER_DISABLE:
                                if (op == MDI_DISABLE_OP) {
                                        MDI_PHCI_SET_USER_DISABLE(ph);
                                } else {
                                        MDI_PHCI_SET_USER_ENABLE(ph);
                                }
                                break;
                        case DRIVER_DISABLE:
                                if (op == MDI_DISABLE_OP) {
                                        MDI_PHCI_SET_DRV_DISABLE(ph);
                                } else {
                                        MDI_PHCI_SET_DRV_ENABLE(ph);
                                }
                                break;
                        case DRIVER_DISABLE_TRANSIENT:
                                if (op == MDI_DISABLE_OP) {
                                        MDI_PHCI_SET_DRV_DISABLE_TRANSIENT(ph);
                                } else {
                                        MDI_PHCI_SET_DRV_ENABLE_TRANSIENT(ph);
                                }
                                break;
                        default:
                                MDI_PHCI_UNLOCK(ph);
                                MDI_DEBUG(1, (MDI_NOTE, cdip ? cdip : pdip,
                                    "!invalid flag argument= %d", flags));
                }

                /*
                 * Phci has been disabled. Now try to enable/disable
                 * path info's to each client.
                 */
                pip = ph->ph_path_head;
                while (pip != NULL) {
                        pip = i_mdi_enable_disable_path(pip, vh, flags, op);
                }
                MDI_PHCI_UNLOCK(ph);
        } else {

                /*
                 * Disable a specific client.
                 */
                ct = i_devi_get_client(cdip);
                if (ct == NULL) {
                        MDI_DEBUG(1, (MDI_NOTE, cdip ? cdip : pdip,
                            "!failed: operation = %d: NULL ct", op));
                        return (MDI_FAILURE);
                }

                MDI_CLIENT_LOCK(ct);
                pip = ct->ct_path_head;
                found_it = 0;
                while (pip != NULL) {
                        MDI_PI_LOCK(pip);
                        next = (mdi_pathinfo_t *)MDI_PI(pip)->pi_client_link;
                        if (MDI_PI(pip)->pi_phci == ph) {
                                MDI_PI_UNLOCK(pip);
                                found_it = 1;
                                break;
                        }
                        MDI_PI_UNLOCK(pip);
                        pip = next;
                }


                MDI_CLIENT_UNLOCK(ct);
                if (found_it == 0) {
                        MDI_DEBUG(1, (MDI_NOTE, cdip ? cdip : pdip,
                            "!failed. Could not find corresponding pip\n"));
                        return (MDI_FAILURE);
                }

                (void) i_mdi_enable_disable_path(pip, vh, flags, op);
        }

        MDI_DEBUG(5, (MDI_NOTE, cdip ? cdip : pdip,
            "!op %d returning success pdip = %p cdip = %p",
            op, (void *)pdip, (void *)cdip));
        return (MDI_SUCCESS);
}

/*
 * Ensure phci powered up
 */
static void
i_mdi_pm_hold_pip(mdi_pathinfo_t *pip)
{
        dev_info_t      *ph_dip;

        ASSERT(pip != NULL);
        ASSERT(MDI_PI_LOCKED(pip));

        if (MDI_PI(pip)->pi_pm_held) {
                return;
        }

        ph_dip = mdi_pi_get_phci(pip);
        MDI_DEBUG(4, (MDI_NOTE, ph_dip,
            "%s %p", mdi_pi_spathname(pip), (void *)pip));
        if (ph_dip == NULL) {
                return;
        }

        MDI_PI_UNLOCK(pip);
        MDI_DEBUG(4, (MDI_NOTE, ph_dip, "kidsupcnt was %d",
            DEVI(ph_dip)->devi_pm_kidsupcnt));
        pm_hold_power(ph_dip);
        MDI_DEBUG(4, (MDI_NOTE, ph_dip, "kidsupcnt is %d",
            DEVI(ph_dip)->devi_pm_kidsupcnt));
        MDI_PI_LOCK(pip);

        /* If PM_GET_PM_INFO is NULL the pm_hold_power above was a noop */
        if (DEVI(ph_dip)->devi_pm_info)
                MDI_PI(pip)->pi_pm_held = 1;
}

/*
 * Allow phci powered down
 */
static void
i_mdi_pm_rele_pip(mdi_pathinfo_t *pip)
{
        dev_info_t      *ph_dip = NULL;

        ASSERT(pip != NULL);
        ASSERT(MDI_PI_LOCKED(pip));

        if (MDI_PI(pip)->pi_pm_held == 0) {
                return;
        }

        ph_dip = mdi_pi_get_phci(pip);
        ASSERT(ph_dip != NULL);

        MDI_DEBUG(4, (MDI_NOTE, ph_dip,
            "%s %p", mdi_pi_spathname(pip), (void *)pip));

        MDI_PI_UNLOCK(pip);
        MDI_DEBUG(4, (MDI_NOTE, ph_dip,
            "kidsupcnt was %d", DEVI(ph_dip)->devi_pm_kidsupcnt));
        pm_rele_power(ph_dip);
        MDI_DEBUG(4, (MDI_NOTE, ph_dip,
            "kidsupcnt is %d", DEVI(ph_dip)->devi_pm_kidsupcnt));
        MDI_PI_LOCK(pip);

        MDI_PI(pip)->pi_pm_held = 0;
}

static void
i_mdi_pm_hold_client(mdi_client_t *ct, int incr)
{
        ASSERT(MDI_CLIENT_LOCKED(ct));

        ct->ct_power_cnt += incr;
        MDI_DEBUG(4, (MDI_NOTE, ct->ct_dip,
            "%p ct_power_cnt = %d incr = %d",
            (void *)ct, ct->ct_power_cnt, incr));
        ASSERT(ct->ct_power_cnt >= 0);
}

static void
i_mdi_rele_all_phci(mdi_client_t *ct)
{
        mdi_pathinfo_t  *pip;

        ASSERT(MDI_CLIENT_LOCKED(ct));
        pip = (mdi_pathinfo_t *)ct->ct_path_head;
        while (pip != NULL) {
                mdi_hold_path(pip);
                MDI_PI_LOCK(pip);
                i_mdi_pm_rele_pip(pip);
                MDI_PI_UNLOCK(pip);
                mdi_rele_path(pip);
                pip = (mdi_pathinfo_t *)MDI_PI(pip)->pi_client_link;
        }
}

static void
i_mdi_pm_rele_client(mdi_client_t *ct, int decr)
{
        ASSERT(MDI_CLIENT_LOCKED(ct));

        if (i_ddi_devi_attached(ct->ct_dip)) {
                ct->ct_power_cnt -= decr;
                MDI_DEBUG(4, (MDI_NOTE, ct->ct_dip,
                    "%p ct_power_cnt = %d decr = %d",
                    (void *)ct, ct->ct_power_cnt, decr));
        }

        ASSERT(ct->ct_power_cnt >= 0);
        if (ct->ct_power_cnt == 0) {
                i_mdi_rele_all_phci(ct);
                return;
        }
}

static void
i_mdi_pm_reset_client(mdi_client_t *ct)
{
        MDI_DEBUG(4, (MDI_NOTE, ct->ct_dip,
            "%p ct_power_cnt = %d", (void *)ct, ct->ct_power_cnt));
        ASSERT(MDI_CLIENT_LOCKED(ct));
        ct->ct_power_cnt = 0;
        i_mdi_rele_all_phci(ct);
        ct->ct_powercnt_config = 0;
        ct->ct_powercnt_unconfig = 0;
        ct->ct_powercnt_reset = 1;
}

static int
i_mdi_power_one_phci(mdi_pathinfo_t *pip)
{
        int             ret;
        dev_info_t      *ph_dip;

        MDI_PI_LOCK(pip);
        i_mdi_pm_hold_pip(pip);

        ph_dip = mdi_pi_get_phci(pip);
        MDI_PI_UNLOCK(pip);

        /* bring all components of phci to full power */
        MDI_DEBUG(4, (MDI_NOTE, ph_dip,
            "pm_powerup for %s%d %p", ddi_driver_name(ph_dip),
            ddi_get_instance(ph_dip), (void *)pip));

        ret = pm_powerup(ph_dip);

        if (ret == DDI_FAILURE) {
                MDI_DEBUG(4, (MDI_NOTE, ph_dip,
                    "pm_powerup FAILED for %s%d %p",
                    ddi_driver_name(ph_dip), ddi_get_instance(ph_dip),
                    (void *)pip));

                MDI_PI_LOCK(pip);
                i_mdi_pm_rele_pip(pip);
                MDI_PI_UNLOCK(pip);
                return (MDI_FAILURE);
        }

        return (MDI_SUCCESS);
}

static int
i_mdi_power_all_phci(mdi_client_t *ct)
{
        mdi_pathinfo_t  *pip;
        int             succeeded = 0;

        ASSERT(MDI_CLIENT_LOCKED(ct));
        pip = (mdi_pathinfo_t *)ct->ct_path_head;
        while (pip != NULL) {
                /*
                 * Don't power if MDI_PATHINFO_STATE_FAULT
                 * or MDI_PATHINFO_STATE_OFFLINE.
                 */
                if (MDI_PI_IS_INIT(pip) ||
                    MDI_PI_IS_ONLINE(pip) || MDI_PI_IS_STANDBY(pip)) {
                        mdi_hold_path(pip);
                        MDI_CLIENT_UNLOCK(ct);
                        if (i_mdi_power_one_phci(pip) == MDI_SUCCESS)
                                succeeded = 1;

                        ASSERT(ct == MDI_PI(pip)->pi_client);
                        MDI_CLIENT_LOCK(ct);
                        mdi_rele_path(pip);
                }
                pip = (mdi_pathinfo_t *)MDI_PI(pip)->pi_client_link;
        }

        return (succeeded ? MDI_SUCCESS : MDI_FAILURE);
}

/*
 * mdi_bus_power():
 *              1. Place the phci(s) into powered up state so that
 *                 client can do power management
 *              2. Ensure phci powered up as client power managing
 * Return Values:
 *              MDI_SUCCESS
 *              MDI_FAILURE
 */
int
mdi_bus_power(dev_info_t *parent, void *impl_arg, pm_bus_power_op_t op,
    void *arg, void *result)
{
        int                     ret = MDI_SUCCESS;
        pm_bp_child_pwrchg_t    *bpc;
        mdi_client_t            *ct;
        dev_info_t              *cdip;
        pm_bp_has_changed_t     *bphc;

        /*
         * BUS_POWER_NOINVOL not supported
         */
        if (op == BUS_POWER_NOINVOL)
                return (MDI_FAILURE);

        /*
         * ignore other OPs.
         * return quickly to save cou cycles on the ct processing
         */
        switch (op) {
        case BUS_POWER_PRE_NOTIFICATION:
        case BUS_POWER_POST_NOTIFICATION:
                bpc = (pm_bp_child_pwrchg_t *)arg;
                cdip = bpc->bpc_dip;
                break;
        case BUS_POWER_HAS_CHANGED:
                bphc = (pm_bp_has_changed_t *)arg;
                cdip = bphc->bphc_dip;
                break;
        default:
                return (pm_busop_bus_power(parent, impl_arg, op, arg, result));
        }

        ASSERT(MDI_CLIENT(cdip));

        ct = i_devi_get_client(cdip);
        if (ct == NULL)
                return (MDI_FAILURE);

        /*
         * wait till the mdi_pathinfo node state change are processed
         */
        MDI_CLIENT_LOCK(ct);
        switch (op) {
        case BUS_POWER_PRE_NOTIFICATION:
                MDI_DEBUG(4, (MDI_NOTE, bpc->bpc_dip,
                    "BUS_POWER_PRE_NOTIFICATION:"
                    "%s@%s, olevel=%d, nlevel=%d, comp=%d",
                    ddi_node_name(bpc->bpc_dip), PM_ADDR(bpc->bpc_dip),
                    bpc->bpc_olevel, bpc->bpc_nlevel, bpc->bpc_comp));

                /* serialize power level change per client */
                while (MDI_CLIENT_IS_POWER_TRANSITION(ct))
                        cv_wait(&ct->ct_powerchange_cv, &ct->ct_mutex);

                MDI_CLIENT_SET_POWER_TRANSITION(ct);

                if (ct->ct_power_cnt == 0) {
                        ret = i_mdi_power_all_phci(ct);
                }

                /*
                 * if new_level > 0:
                 *      - hold phci(s)
                 *      - power up phci(s) if not already
                 * ignore power down
                 */
                if (bpc->bpc_nlevel > 0) {
                        if (!DEVI_IS_ATTACHING(ct->ct_dip)) {
                                MDI_DEBUG(4, (MDI_NOTE, bpc->bpc_dip,
                                    "i_mdi_pm_hold_client\n"));
                                i_mdi_pm_hold_client(ct, ct->ct_path_count);
                        }
                }
                break;
        case BUS_POWER_POST_NOTIFICATION:
                MDI_DEBUG(4, (MDI_NOTE, bpc->bpc_dip,
                    "BUS_POWER_POST_NOTIFICATION:"
                    "%s@%s, olevel=%d, nlevel=%d, comp=%d result=%d",
                    ddi_node_name(bpc->bpc_dip), PM_ADDR(bpc->bpc_dip),
                    bpc->bpc_olevel, bpc->bpc_nlevel, bpc->bpc_comp,
                    *(int *)result));

                if (*(int *)result == DDI_SUCCESS) {
                        if (bpc->bpc_nlevel > 0) {
                                MDI_CLIENT_SET_POWER_UP(ct);
                        } else {
                                MDI_CLIENT_SET_POWER_DOWN(ct);
                        }
                }

                /* release the hold we did in pre-notification */
                if (bpc->bpc_nlevel > 0 && (*(int *)result != DDI_SUCCESS) &&
                    !DEVI_IS_ATTACHING(ct->ct_dip)) {
                        MDI_DEBUG(4, (MDI_NOTE, bpc->bpc_dip,
                            "i_mdi_pm_rele_client\n"));
                        i_mdi_pm_rele_client(ct, ct->ct_path_count);
                }

                if (bpc->bpc_nlevel == 0 && (*(int *)result == DDI_SUCCESS)) {
                        /* another thread might started attaching */
                        if (DEVI_IS_ATTACHING(ct->ct_dip)) {
                                MDI_DEBUG(4, (MDI_NOTE, bpc->bpc_dip,
                                    "i_mdi_pm_rele_client\n"));
                                i_mdi_pm_rele_client(ct, ct->ct_path_count);
                        /* detaching has been taken care in pm_post_unconfig */
                        } else if (!DEVI_IS_DETACHING(ct->ct_dip)) {
                                MDI_DEBUG(4, (MDI_NOTE, bpc->bpc_dip,
                                    "i_mdi_pm_reset_client\n"));
                                i_mdi_pm_reset_client(ct);
                        }
                }

                MDI_CLIENT_CLEAR_POWER_TRANSITION(ct);
                cv_broadcast(&ct->ct_powerchange_cv);

                break;

        /* need to do more */
        case BUS_POWER_HAS_CHANGED:
                MDI_DEBUG(4, (MDI_NOTE, bphc->bphc_dip,
                    "BUS_POWER_HAS_CHANGED:"
                    "%s@%s, olevel=%d, nlevel=%d, comp=%d",
                    ddi_node_name(bphc->bphc_dip), PM_ADDR(bphc->bphc_dip),
                    bphc->bphc_olevel, bphc->bphc_nlevel, bphc->bphc_comp));

                if (bphc->bphc_nlevel > 0 &&
                    bphc->bphc_nlevel > bphc->bphc_olevel) {
                        if (ct->ct_power_cnt == 0) {
                                ret = i_mdi_power_all_phci(ct);
                        }
                        MDI_DEBUG(4, (MDI_NOTE, bphc->bphc_dip,
                            "i_mdi_pm_hold_client\n"));
                        i_mdi_pm_hold_client(ct, ct->ct_path_count);
                }

                if (bphc->bphc_nlevel == 0 && bphc->bphc_olevel != -1) {
                        MDI_DEBUG(4, (MDI_NOTE, bphc->bphc_dip,
                            "i_mdi_pm_rele_client\n"));
                        i_mdi_pm_rele_client(ct, ct->ct_path_count);
                }
                break;
        }

        MDI_CLIENT_UNLOCK(ct);
        return (ret);
}

static int
i_mdi_pm_pre_config_one(dev_info_t *child)
{
        int             ret = MDI_SUCCESS;
        mdi_client_t    *ct;

        ct = i_devi_get_client(child);
        if (ct == NULL)
                return (MDI_FAILURE);

        MDI_CLIENT_LOCK(ct);
        while (MDI_CLIENT_IS_POWER_TRANSITION(ct))
                cv_wait(&ct->ct_powerchange_cv, &ct->ct_mutex);

        if (!MDI_CLIENT_IS_FAILED(ct)) {
                MDI_CLIENT_UNLOCK(ct);
                MDI_DEBUG(4, (MDI_NOTE, child, "already configured\n"));
                return (MDI_SUCCESS);
        }

        if (ct->ct_powercnt_config) {
                MDI_CLIENT_UNLOCK(ct);
                MDI_DEBUG(4, (MDI_NOTE, child, "already held\n"));
                return (MDI_SUCCESS);
        }

        if (ct->ct_power_cnt == 0) {
                ret = i_mdi_power_all_phci(ct);
        }
        MDI_DEBUG(4, (MDI_NOTE, child, "i_mdi_pm_hold_client\n"));
        i_mdi_pm_hold_client(ct, ct->ct_path_count);
        ct->ct_powercnt_config = 1;
        ct->ct_powercnt_reset = 0;
        MDI_CLIENT_UNLOCK(ct);
        return (ret);
}

static int
i_mdi_pm_pre_config(dev_info_t *vdip, dev_info_t *child)
{
        int                     ret = MDI_SUCCESS;
        dev_info_t              *cdip;
        int                     circ;

        ASSERT(MDI_VHCI(vdip));

        /* ndi_devi_config_one */
        if (child) {
                ASSERT(DEVI_BUSY_OWNED(vdip));
                return (i_mdi_pm_pre_config_one(child));
        }

        /* devi_config_common */
        ndi_devi_enter(vdip, &circ);
        cdip = ddi_get_child(vdip);
        while (cdip) {
                dev_info_t *next = ddi_get_next_sibling(cdip);

                ret = i_mdi_pm_pre_config_one(cdip);
                if (ret != MDI_SUCCESS)
                        break;
                cdip = next;
        }
        ndi_devi_exit(vdip, circ);
        return (ret);
}

static int
i_mdi_pm_pre_unconfig_one(dev_info_t *child, int *held, int flags)
{
        int             ret = MDI_SUCCESS;
        mdi_client_t    *ct;

        ct = i_devi_get_client(child);
        if (ct == NULL)
                return (MDI_FAILURE);

        MDI_CLIENT_LOCK(ct);
        while (MDI_CLIENT_IS_POWER_TRANSITION(ct))
                cv_wait(&ct->ct_powerchange_cv, &ct->ct_mutex);

        if (!i_ddi_devi_attached(child)) {
                MDI_DEBUG(4, (MDI_NOTE, child, "node detached already\n"));
                MDI_CLIENT_UNLOCK(ct);
                return (MDI_SUCCESS);
        }

        if (MDI_CLIENT_IS_POWERED_DOWN(ct) &&
            (flags & NDI_AUTODETACH)) {
                MDI_DEBUG(4, (MDI_NOTE, child, "auto-modunload\n"));
                MDI_CLIENT_UNLOCK(ct);
                return (MDI_FAILURE);
        }

        if (ct->ct_powercnt_unconfig) {
                MDI_DEBUG(4, (MDI_NOTE, child, "ct_powercnt_held\n"));
                MDI_CLIENT_UNLOCK(ct);
                *held = 1;
                return (MDI_SUCCESS);
        }

        if (ct->ct_power_cnt == 0) {
                ret = i_mdi_power_all_phci(ct);
        }
        MDI_DEBUG(4, (MDI_NOTE, child, "i_mdi_pm_hold_client\n"));
        i_mdi_pm_hold_client(ct, ct->ct_path_count);
        ct->ct_powercnt_unconfig = 1;
        ct->ct_powercnt_reset = 0;
        MDI_CLIENT_UNLOCK(ct);
        if (ret == MDI_SUCCESS)
                *held = 1;
        return (ret);
}

static int
i_mdi_pm_pre_unconfig(dev_info_t *vdip, dev_info_t *child, int *held,
    int flags)
{
        int                     ret = MDI_SUCCESS;
        dev_info_t              *cdip;
        int                     circ;

        ASSERT(MDI_VHCI(vdip));
        *held = 0;

        /* ndi_devi_unconfig_one */
        if (child) {
                ASSERT(DEVI_BUSY_OWNED(vdip));
                return (i_mdi_pm_pre_unconfig_one(child, held, flags));
        }

        /* devi_unconfig_common */
        ndi_devi_enter(vdip, &circ);
        cdip = ddi_get_child(vdip);
        while (cdip) {
                dev_info_t *next = ddi_get_next_sibling(cdip);

                ret = i_mdi_pm_pre_unconfig_one(cdip, held, flags);
                cdip = next;
        }
        ndi_devi_exit(vdip, circ);

        if (*held)
                ret = MDI_SUCCESS;

        return (ret);
}

static void
i_mdi_pm_post_config_one(dev_info_t *child)
{
        mdi_client_t    *ct;

        ct = i_devi_get_client(child);
        if (ct == NULL)
                return;

        MDI_CLIENT_LOCK(ct);
        while (MDI_CLIENT_IS_POWER_TRANSITION(ct))
                cv_wait(&ct->ct_powerchange_cv, &ct->ct_mutex);

        if (ct->ct_powercnt_reset || !ct->ct_powercnt_config) {
                MDI_DEBUG(4, (MDI_NOTE, child, "not configured\n"));
                MDI_CLIENT_UNLOCK(ct);
                return;
        }

        /* client has not been updated */
        if (MDI_CLIENT_IS_FAILED(ct)) {
                MDI_DEBUG(4, (MDI_NOTE, child, "client failed\n"));
                MDI_CLIENT_UNLOCK(ct);
                return;
        }

        /* another thread might have powered it down or detached it */
        if ((MDI_CLIENT_IS_POWERED_DOWN(ct) &&
            !DEVI_IS_ATTACHING(child)) ||
            (!i_ddi_devi_attached(child) &&
            !DEVI_IS_ATTACHING(child))) {
                MDI_DEBUG(4, (MDI_NOTE, child, "i_mdi_pm_reset_client\n"));
                i_mdi_pm_reset_client(ct);
        } else {
                mdi_pathinfo_t  *pip, *next;
                int     valid_path_count = 0;

                MDI_DEBUG(4, (MDI_NOTE, child, "i_mdi_pm_rele_client\n"));
                pip = ct->ct_path_head;
                while (pip != NULL) {
                        MDI_PI_LOCK(pip);
                        next = (mdi_pathinfo_t *)MDI_PI(pip)->pi_client_link;
                        if (MDI_PI_IS_ONLINE(pip) || MDI_PI_IS_STANDBY(pip))
                                valid_path_count ++;
                        MDI_PI_UNLOCK(pip);
                        pip = next;
                }
                i_mdi_pm_rele_client(ct, valid_path_count);
        }
        ct->ct_powercnt_config = 0;
        MDI_CLIENT_UNLOCK(ct);
}

static void
i_mdi_pm_post_config(dev_info_t *vdip, dev_info_t *child)
{
        int             circ;
        dev_info_t      *cdip;

        ASSERT(MDI_VHCI(vdip));

        /* ndi_devi_config_one */
        if (child) {
                ASSERT(DEVI_BUSY_OWNED(vdip));
                i_mdi_pm_post_config_one(child);
                return;
        }

        /* devi_config_common */
        ndi_devi_enter(vdip, &circ);
        cdip = ddi_get_child(vdip);
        while (cdip) {
                dev_info_t *next = ddi_get_next_sibling(cdip);

                i_mdi_pm_post_config_one(cdip);
                cdip = next;
        }
        ndi_devi_exit(vdip, circ);
}

static void
i_mdi_pm_post_unconfig_one(dev_info_t *child)
{
        mdi_client_t    *ct;

        ct = i_devi_get_client(child);
        if (ct == NULL)
                return;

        MDI_CLIENT_LOCK(ct);
        while (MDI_CLIENT_IS_POWER_TRANSITION(ct))
                cv_wait(&ct->ct_powerchange_cv, &ct->ct_mutex);

        if (!ct->ct_powercnt_unconfig || ct->ct_powercnt_reset) {
                MDI_DEBUG(4, (MDI_NOTE, child, "not held\n"));
                MDI_CLIENT_UNLOCK(ct);
                return;
        }

        /* failure detaching or another thread just attached it */
        if ((MDI_CLIENT_IS_POWERED_DOWN(ct) &&
            i_ddi_devi_attached(child)) ||
            (!i_ddi_devi_attached(child) &&
            !DEVI_IS_ATTACHING(child))) {
                MDI_DEBUG(4, (MDI_NOTE, child, "i_mdi_pm_reset_client\n"));
                i_mdi_pm_reset_client(ct);
        } else {
                mdi_pathinfo_t  *pip, *next;
                int     valid_path_count = 0;

                MDI_DEBUG(4, (MDI_NOTE, child, "i_mdi_pm_rele_client\n"));
                pip = ct->ct_path_head;
                while (pip != NULL) {
                        MDI_PI_LOCK(pip);
                        next = (mdi_pathinfo_t *)MDI_PI(pip)->pi_client_link;
                        if (MDI_PI_IS_ONLINE(pip) || MDI_PI_IS_STANDBY(pip))
                                valid_path_count ++;
                        MDI_PI_UNLOCK(pip);
                        pip = next;
                }
                i_mdi_pm_rele_client(ct, valid_path_count);
                ct->ct_powercnt_unconfig = 0;
        }

        MDI_CLIENT_UNLOCK(ct);
}

static void
i_mdi_pm_post_unconfig(dev_info_t *vdip, dev_info_t *child, int held)
{
        int                     circ;
        dev_info_t              *cdip;

        ASSERT(MDI_VHCI(vdip));

        if (!held) {
                MDI_DEBUG(4, (MDI_NOTE, vdip, "held = %d", held));
                return;
        }

        if (child) {
                ASSERT(DEVI_BUSY_OWNED(vdip));
                i_mdi_pm_post_unconfig_one(child);
                return;
        }

        ndi_devi_enter(vdip, &circ);
        cdip = ddi_get_child(vdip);
        while (cdip) {
                dev_info_t *next = ddi_get_next_sibling(cdip);

                i_mdi_pm_post_unconfig_one(cdip);
                cdip = next;
        }
        ndi_devi_exit(vdip, circ);
}

int
mdi_power(dev_info_t *vdip, mdi_pm_op_t op, void *args, char *devnm, int flags)
{
        int                     circ, ret = MDI_SUCCESS;
        dev_info_t              *client_dip = NULL;
        mdi_client_t            *ct;

        /*
         * Handling ndi_devi_config_one and ndi_devi_unconfig_one.
         * Power up pHCI for the named client device.
         * Note: Before the client is enumerated under vhci by phci,
         * client_dip can be NULL. Then proceed to power up all the
         * pHCIs.
         */
        if (devnm != NULL) {
                ndi_devi_enter(vdip, &circ);
                client_dip = ndi_devi_findchild(vdip, devnm);
        }

        MDI_DEBUG(4, (MDI_NOTE, vdip,
            "op = %d %s %p", op, devnm ? devnm : "", (void *)client_dip));

        switch (op) {
        case MDI_PM_PRE_CONFIG:
                ret = i_mdi_pm_pre_config(vdip, client_dip);
                break;

        case MDI_PM_PRE_UNCONFIG:
                ret = i_mdi_pm_pre_unconfig(vdip, client_dip, (int *)args,
                    flags);
                break;

        case MDI_PM_POST_CONFIG:
                i_mdi_pm_post_config(vdip, client_dip);
                break;

        case MDI_PM_POST_UNCONFIG:
                i_mdi_pm_post_unconfig(vdip, client_dip, *(int *)args);
                break;

        case MDI_PM_HOLD_POWER:
        case MDI_PM_RELE_POWER:
                ASSERT(args);

                client_dip = (dev_info_t *)args;
                ASSERT(MDI_CLIENT(client_dip));

                ct = i_devi_get_client(client_dip);
                MDI_CLIENT_LOCK(ct);

                if (op == MDI_PM_HOLD_POWER) {
                        if (ct->ct_power_cnt == 0) {
                                (void) i_mdi_power_all_phci(ct);
                                MDI_DEBUG(4, (MDI_NOTE, client_dip,
                                    "i_mdi_pm_hold_client\n"));
                                i_mdi_pm_hold_client(ct, ct->ct_path_count);
                        }
                } else {
                        if (DEVI_IS_ATTACHING(client_dip)) {
                                MDI_DEBUG(4, (MDI_NOTE, client_dip,
                                    "i_mdi_pm_rele_client\n"));
                                i_mdi_pm_rele_client(ct, ct->ct_path_count);
                        } else {
                                MDI_DEBUG(4, (MDI_NOTE, client_dip,
                                    "i_mdi_pm_reset_client\n"));
                                i_mdi_pm_reset_client(ct);
                        }
                }

                MDI_CLIENT_UNLOCK(ct);
                break;

        default:
                break;
        }

        if (devnm)
                ndi_devi_exit(vdip, circ);

        return (ret);
}

int
mdi_component_is_vhci(dev_info_t *dip, const char **mdi_class)
{
        mdi_vhci_t *vhci;

        if (!MDI_VHCI(dip))
                return (MDI_FAILURE);

        if (mdi_class) {
                vhci = DEVI(dip)->devi_mdi_xhci;
                ASSERT(vhci);
                *mdi_class = vhci->vh_class;
        }

        return (MDI_SUCCESS);
}

int
mdi_component_is_phci(dev_info_t *dip, const char **mdi_class)
{
        mdi_phci_t *phci;

        if (!MDI_PHCI(dip))
                return (MDI_FAILURE);

        if (mdi_class) {
                phci = DEVI(dip)->devi_mdi_xhci;
                ASSERT(phci);
                *mdi_class = phci->ph_vhci->vh_class;
        }

        return (MDI_SUCCESS);
}

int
mdi_component_is_client(dev_info_t *dip, const char **mdi_class)
{
        mdi_client_t *client;

        if (!MDI_CLIENT(dip))
                return (MDI_FAILURE);

        if (mdi_class) {
                client = DEVI(dip)->devi_mdi_client;
                ASSERT(client);
                *mdi_class = client->ct_vhci->vh_class;
        }

        return (MDI_SUCCESS);
}

void *
mdi_client_get_vhci_private(dev_info_t *dip)
{
        ASSERT(mdi_component_is_client(dip, NULL) == MDI_SUCCESS);
        if (mdi_component_is_client(dip, NULL) == MDI_SUCCESS) {
                mdi_client_t    *ct;
                ct = i_devi_get_client(dip);
                return (ct->ct_vprivate);
        }
        return (NULL);
}

void
mdi_client_set_vhci_private(dev_info_t *dip, void *data)
{
        ASSERT(mdi_component_is_client(dip, NULL) == MDI_SUCCESS);
        if (mdi_component_is_client(dip, NULL) == MDI_SUCCESS) {
                mdi_client_t    *ct;
                ct = i_devi_get_client(dip);
                ct->ct_vprivate = data;
        }
}
/*
 * mdi_pi_get_vhci_private():
 *              Get the vhci private information associated with the
 *              mdi_pathinfo node
 */
void *
mdi_pi_get_vhci_private(mdi_pathinfo_t *pip)
{
        caddr_t vprivate = NULL;
        if (pip) {
                vprivate = MDI_PI(pip)->pi_vprivate;
        }
        return (vprivate);
}

/*
 * mdi_pi_set_vhci_private():
 *              Set the vhci private information in the mdi_pathinfo node
 */
void
mdi_pi_set_vhci_private(mdi_pathinfo_t *pip, void *priv)
{
        if (pip) {
                MDI_PI(pip)->pi_vprivate = priv;
        }
}

/*
 * mdi_phci_get_vhci_private():
 *              Get the vhci private information associated with the
 *              mdi_phci node
 */
void *
mdi_phci_get_vhci_private(dev_info_t *dip)
{
        ASSERT(mdi_component_is_phci(dip, NULL) == MDI_SUCCESS);
        if (mdi_component_is_phci(dip, NULL) == MDI_SUCCESS) {
                mdi_phci_t      *ph;
                ph = i_devi_get_phci(dip);
                return (ph->ph_vprivate);
        }
        return (NULL);
}

/*
 * mdi_phci_set_vhci_private():
 *              Set the vhci private information in the mdi_phci node
 */
void
mdi_phci_set_vhci_private(dev_info_t *dip, void *priv)
{
        ASSERT(mdi_component_is_phci(dip, NULL) == MDI_SUCCESS);
        if (mdi_component_is_phci(dip, NULL) == MDI_SUCCESS) {
                mdi_phci_t      *ph;
                ph = i_devi_get_phci(dip);
                ph->ph_vprivate = priv;
        }
}

int
mdi_pi_ishidden(mdi_pathinfo_t *pip)
{
        return (MDI_PI_FLAGS_IS_HIDDEN(pip));
}

int
mdi_pi_device_isremoved(mdi_pathinfo_t *pip)
{
        return (MDI_PI_FLAGS_IS_DEVICE_REMOVED(pip));
}

/* Return 1 if all client paths are device_removed */
static int
i_mdi_client_all_devices_removed(mdi_client_t *ct)
{
        mdi_pathinfo_t  *pip;
        int             all_devices_removed = 1;

        MDI_CLIENT_LOCK(ct);
        for (pip = ct->ct_path_head; pip;
            pip = (mdi_pathinfo_t *)MDI_PI(pip)->pi_client_link) {
                if (!mdi_pi_device_isremoved(pip)) {
                        all_devices_removed = 0;
                        break;
                }
        }
        MDI_CLIENT_UNLOCK(ct);
        return (all_devices_removed);
}

/*
 * When processing path hotunplug, represent device removal.
 */
int
mdi_pi_device_remove(mdi_pathinfo_t *pip)
{
        mdi_client_t    *ct;

        MDI_PI_LOCK(pip);
        if (mdi_pi_device_isremoved(pip)) {
                MDI_PI_UNLOCK(pip);
                return (0);
        }
        MDI_PI_FLAGS_SET_DEVICE_REMOVED(pip);
        MDI_PI_FLAGS_SET_HIDDEN(pip);
        MDI_PI_UNLOCK(pip);

        /*
         * If all paths associated with the client are now DEVICE_REMOVED,
         * reflect DEVICE_REMOVED in the client.
         */
        ct = MDI_PI(pip)->pi_client;
        if (ct && ct->ct_dip && i_mdi_client_all_devices_removed(ct))
                (void) ndi_devi_device_remove(ct->ct_dip);
        else
                i_ddi_di_cache_invalidate();

        return (1);
}

/*
 * When processing hotplug, if a path marked mdi_pi_device_isremoved()
 * is now accessible then this interfaces is used to represent device insertion.
 */
int
mdi_pi_device_insert(mdi_pathinfo_t *pip)
{
        MDI_PI_LOCK(pip);
        if (!mdi_pi_device_isremoved(pip)) {
                MDI_PI_UNLOCK(pip);
                return (0);
        }
        MDI_PI_FLAGS_CLR_DEVICE_REMOVED(pip);
        MDI_PI_FLAGS_CLR_HIDDEN(pip);
        MDI_PI_UNLOCK(pip);

        i_ddi_di_cache_invalidate();

        return (1);
}

/*
 * List of vhci class names:
 * A vhci class name must be in this list only if the corresponding vhci
 * driver intends to use the mdi provided bus config implementation
 * (i.e., mdi_vhci_bus_config()).
 */
static char *vhci_class_list[] = { MDI_HCI_CLASS_SCSI, MDI_HCI_CLASS_IB };
#define N_VHCI_CLASSES  (sizeof (vhci_class_list) / sizeof (char *))

/*
 * During boot time, the on-disk vhci cache for every vhci class is read
 * in the form of an nvlist and stored here.
 */
static nvlist_t *vhcache_nvl[N_VHCI_CLASSES];

/* nvpair names in vhci cache nvlist */
#define MDI_VHCI_CACHE_VERSION  1
#define MDI_NVPNAME_VERSION     "version"
#define MDI_NVPNAME_PHCIS       "phcis"
#define MDI_NVPNAME_CTADDRMAP   "clientaddrmap"

/*
 * Given vhci class name, return its on-disk vhci cache filename.
 * Memory for the returned filename which includes the full path is allocated
 * by this function.
 */
static char *
vhclass2vhcache_filename(char *vhclass)
{
        char *filename;
        int len;
        static char *fmt = "/etc/devices/mdi_%s_cache";

        /*
         * fmt contains the on-disk vhci cache file name format;
         * for scsi_vhci the filename is "/etc/devices/mdi_scsi_vhci_cache".
         */

        /* the -1 below is to account for "%s" in the format string */
        len = strlen(fmt) + strlen(vhclass) - 1;
        filename = kmem_alloc(len, KM_SLEEP);
        (void) snprintf(filename, len, fmt, vhclass);
        ASSERT(len == (strlen(filename) + 1));
        return (filename);
}

/*
 * initialize the vhci cache related data structures and read the on-disk
 * vhci cached data into memory.
 */
static void
setup_vhci_cache(mdi_vhci_t *vh)
{
        mdi_vhci_config_t *vhc;
        mdi_vhci_cache_t *vhcache;
        int i;
        nvlist_t *nvl = NULL;

        vhc = kmem_zalloc(sizeof (mdi_vhci_config_t), KM_SLEEP);
        vh->vh_config = vhc;
        vhcache = &vhc->vhc_vhcache;

        vhc->vhc_vhcache_filename = vhclass2vhcache_filename(vh->vh_class);

        mutex_init(&vhc->vhc_lock, NULL, MUTEX_DEFAULT, NULL);
        cv_init(&vhc->vhc_cv, NULL, CV_DRIVER, NULL);

        rw_init(&vhcache->vhcache_lock, NULL, RW_DRIVER, NULL);

        /*
         * Create string hash; same as mod_hash_create_strhash() except that
         * we use NULL key destructor.
         */
        vhcache->vhcache_client_hash = mod_hash_create_extended(vh->vh_class,
            mdi_bus_config_cache_hash_size,
            mod_hash_null_keydtor, mod_hash_null_valdtor,
            mod_hash_bystr, NULL, mod_hash_strkey_cmp, KM_SLEEP);

        /*
         * The on-disk vhci cache is read during booting prior to the
         * lights-out period by mdi_read_devices_files().
         */
        for (i = 0; i < N_VHCI_CLASSES; i++) {
                if (strcmp(vhci_class_list[i], vh->vh_class) == 0) {
                        nvl = vhcache_nvl[i];
                        vhcache_nvl[i] = NULL;
                        break;
                }
        }

        /*
         * this is to cover the case of some one manually causing unloading
         * (or detaching) and reloading (or attaching) of a vhci driver.
         */
        if (nvl == NULL && modrootloaded)
                nvl = read_on_disk_vhci_cache(vh->vh_class);

        if (nvl != NULL) {
                rw_enter(&vhcache->vhcache_lock, RW_WRITER);
                if (mainnvl_to_vhcache(vhcache, nvl) == MDI_SUCCESS)
                        vhcache->vhcache_flags |= MDI_VHCI_CACHE_SETUP_DONE;
                else  {
                        cmn_err(CE_WARN,
                            "%s: data file corrupted, will recreate",
                            vhc->vhc_vhcache_filename);
                }
                rw_exit(&vhcache->vhcache_lock);
                nvlist_free(nvl);
        }

        vhc->vhc_cbid = callb_add(stop_vhcache_flush_thread, vhc,
            CB_CL_UADMIN_PRE_VFS, "mdi_vhcache_flush");

        vhc->vhc_path_discovery_boot = mdi_path_discovery_boot;
        vhc->vhc_path_discovery_postboot = mdi_path_discovery_postboot;
}

/*
 * free all vhci cache related resources
 */
static int
destroy_vhci_cache(mdi_vhci_t *vh)
{
        mdi_vhci_config_t *vhc = vh->vh_config;
        mdi_vhci_cache_t *vhcache = &vhc->vhc_vhcache;
        mdi_vhcache_phci_t *cphci, *cphci_next;
        mdi_vhcache_client_t *cct, *cct_next;
        mdi_vhcache_pathinfo_t *cpi, *cpi_next;

        if (stop_vhcache_async_threads(vhc) != MDI_SUCCESS)
                return (MDI_FAILURE);

        kmem_free(vhc->vhc_vhcache_filename,
            strlen(vhc->vhc_vhcache_filename) + 1);

        mod_hash_destroy_strhash(vhcache->vhcache_client_hash);

        for (cphci = vhcache->vhcache_phci_head; cphci != NULL;
            cphci = cphci_next) {
                cphci_next = cphci->cphci_next;
                free_vhcache_phci(cphci);
        }

        for (cct = vhcache->vhcache_client_head; cct != NULL; cct = cct_next) {
                cct_next = cct->cct_next;
                for (cpi = cct->cct_cpi_head; cpi != NULL; cpi = cpi_next) {
                        cpi_next = cpi->cpi_next;
                        free_vhcache_pathinfo(cpi);
                }
                free_vhcache_client(cct);
        }

        rw_destroy(&vhcache->vhcache_lock);

        mutex_destroy(&vhc->vhc_lock);
        cv_destroy(&vhc->vhc_cv);
        kmem_free(vhc, sizeof (mdi_vhci_config_t));
        return (MDI_SUCCESS);
}

/*
 * Stop all vhci cache related async threads and free their resources.
 */
static int
stop_vhcache_async_threads(mdi_vhci_config_t *vhc)
{
        mdi_async_client_config_t *acc, *acc_next;

        mutex_enter(&vhc->vhc_lock);
        vhc->vhc_flags |= MDI_VHC_EXIT;
        ASSERT(vhc->vhc_acc_thrcount >= 0);
        cv_broadcast(&vhc->vhc_cv);

        while ((vhc->vhc_flags & MDI_VHC_VHCACHE_FLUSH_THREAD) ||
            vhc->vhc_acc_thrcount != 0) {
                mutex_exit(&vhc->vhc_lock);
                delay_random(mdi_delay);
                mutex_enter(&vhc->vhc_lock);
        }

        vhc->vhc_flags &= ~MDI_VHC_EXIT;

        for (acc = vhc->vhc_acc_list_head; acc != NULL; acc = acc_next) {
                acc_next = acc->acc_next;
                free_async_client_config(acc);
        }
        vhc->vhc_acc_list_head = NULL;
        vhc->vhc_acc_list_tail = NULL;
        vhc->vhc_acc_count = 0;

        if (vhc->vhc_flags & MDI_VHC_VHCACHE_DIRTY) {
                vhc->vhc_flags &= ~MDI_VHC_VHCACHE_DIRTY;
                mutex_exit(&vhc->vhc_lock);
                if (flush_vhcache(vhc, 0) != MDI_SUCCESS) {
                        vhcache_dirty(vhc);
                        return (MDI_FAILURE);
                }
        } else
                mutex_exit(&vhc->vhc_lock);

        if (callb_delete(vhc->vhc_cbid) != 0)
                return (MDI_FAILURE);

        return (MDI_SUCCESS);
}

/*
 * Stop vhci cache flush thread
 */
/* ARGSUSED */
static boolean_t
stop_vhcache_flush_thread(void *arg, int code)
{
        mdi_vhci_config_t *vhc = (mdi_vhci_config_t *)arg;

        mutex_enter(&vhc->vhc_lock);
        vhc->vhc_flags |= MDI_VHC_EXIT;
        cv_broadcast(&vhc->vhc_cv);

        while (vhc->vhc_flags & MDI_VHC_VHCACHE_FLUSH_THREAD) {
                mutex_exit(&vhc->vhc_lock);
                delay_random(mdi_delay);
                mutex_enter(&vhc->vhc_lock);
        }

        if (vhc->vhc_flags & MDI_VHC_VHCACHE_DIRTY) {
                vhc->vhc_flags &= ~MDI_VHC_VHCACHE_DIRTY;
                mutex_exit(&vhc->vhc_lock);
                (void) flush_vhcache(vhc, 1);
        } else
                mutex_exit(&vhc->vhc_lock);

        return (B_TRUE);
}

/*
 * Enqueue the vhcache phci (cphci) at the tail of the list
 */
static void
enqueue_vhcache_phci(mdi_vhci_cache_t *vhcache, mdi_vhcache_phci_t *cphci)
{
        cphci->cphci_next = NULL;
        if (vhcache->vhcache_phci_head == NULL)
                vhcache->vhcache_phci_head = cphci;
        else
                vhcache->vhcache_phci_tail->cphci_next = cphci;
        vhcache->vhcache_phci_tail = cphci;
}

/*
 * Enqueue the vhcache pathinfo (cpi) at the tail of the list
 */
static void
enqueue_tail_vhcache_pathinfo(mdi_vhcache_client_t *cct,
    mdi_vhcache_pathinfo_t *cpi)
{
        cpi->cpi_next = NULL;
        if (cct->cct_cpi_head == NULL)
                cct->cct_cpi_head = cpi;
        else
                cct->cct_cpi_tail->cpi_next = cpi;
        cct->cct_cpi_tail = cpi;
}

/*
 * Enqueue the vhcache pathinfo (cpi) at the correct location in the
 * ordered list. All cpis which do not have MDI_CPI_HINT_PATH_DOES_NOT_EXIST
 * flag set come at the beginning of the list. All cpis which have this
 * flag set come at the end of the list.
 */
static void
enqueue_vhcache_pathinfo(mdi_vhcache_client_t *cct,
    mdi_vhcache_pathinfo_t *newcpi)
{
        mdi_vhcache_pathinfo_t *cpi, *prev_cpi;

        if (cct->cct_cpi_head == NULL ||
            (newcpi->cpi_flags & MDI_CPI_HINT_PATH_DOES_NOT_EXIST))
                enqueue_tail_vhcache_pathinfo(cct, newcpi);
        else {
                for (cpi = cct->cct_cpi_head, prev_cpi = NULL; cpi != NULL &&
                    !(cpi->cpi_flags & MDI_CPI_HINT_PATH_DOES_NOT_EXIST);
                    prev_cpi = cpi, cpi = cpi->cpi_next)
                        ;

                if (prev_cpi == NULL)
                        cct->cct_cpi_head = newcpi;
                else
                        prev_cpi->cpi_next = newcpi;

                newcpi->cpi_next = cpi;

                if (cpi == NULL)
                        cct->cct_cpi_tail = newcpi;
        }
}

/*
 * Enqueue the vhcache client (cct) at the tail of the list
 */
static void
enqueue_vhcache_client(mdi_vhci_cache_t *vhcache,
    mdi_vhcache_client_t *cct)
{
        cct->cct_next = NULL;
        if (vhcache->vhcache_client_head == NULL)
                vhcache->vhcache_client_head = cct;
        else
                vhcache->vhcache_client_tail->cct_next = cct;
        vhcache->vhcache_client_tail = cct;
}

static void
free_string_array(char **str, int nelem)
{
        int i;

        if (str) {
                for (i = 0; i < nelem; i++) {
                        if (str[i])
                                kmem_free(str[i], strlen(str[i]) + 1);
                }
                kmem_free(str, sizeof (char *) * nelem);
        }
}

static void
free_vhcache_phci(mdi_vhcache_phci_t *cphci)
{
        kmem_free(cphci->cphci_path, strlen(cphci->cphci_path) + 1);
        kmem_free(cphci, sizeof (*cphci));
}

static void
free_vhcache_pathinfo(mdi_vhcache_pathinfo_t *cpi)
{
        kmem_free(cpi->cpi_addr, strlen(cpi->cpi_addr) + 1);
        kmem_free(cpi, sizeof (*cpi));
}

static void
free_vhcache_client(mdi_vhcache_client_t *cct)
{
        kmem_free(cct->cct_name_addr, strlen(cct->cct_name_addr) + 1);
        kmem_free(cct, sizeof (*cct));
}

static char *
vhcache_mknameaddr(char *ct_name, char *ct_addr, int *ret_len)
{
        char *name_addr;
        int len;

        len = strlen(ct_name) + strlen(ct_addr) + 2;
        name_addr = kmem_alloc(len, KM_SLEEP);
        (void) snprintf(name_addr, len, "%s@%s", ct_name, ct_addr);

        if (ret_len)
                *ret_len = len;
        return (name_addr);
}

/*
 * Copy the contents of paddrnvl to vhci cache.
 * paddrnvl nvlist contains path information for a vhci client.
 * See the comment in mainnvl_to_vhcache() for the format of this nvlist.
 */
static void
paddrnvl_to_vhcache(nvlist_t *nvl, mdi_vhcache_phci_t *cphci_list[],
    mdi_vhcache_client_t *cct)
{
        nvpair_t *nvp = NULL;
        mdi_vhcache_pathinfo_t *cpi;
        uint_t nelem;
        uint32_t *val;

        while ((nvp = nvlist_next_nvpair(nvl, nvp)) != NULL) {
                ASSERT(nvpair_type(nvp) == DATA_TYPE_UINT32_ARRAY);
                cpi = kmem_zalloc(sizeof (*cpi), KM_SLEEP);
                cpi->cpi_addr = i_ddi_strdup(nvpair_name(nvp), KM_SLEEP);
                (void) nvpair_value_uint32_array(nvp, &val, &nelem);
                ASSERT(nelem == 2);
                cpi->cpi_cphci = cphci_list[val[0]];
                cpi->cpi_flags = val[1];
                enqueue_tail_vhcache_pathinfo(cct, cpi);
        }
}

/*
 * Copy the contents of caddrmapnvl to vhci cache.
 * caddrmapnvl nvlist contains vhci client address to phci client address
 * mappings. See the comment in mainnvl_to_vhcache() for the format of
 * this nvlist.
 */
static void
caddrmapnvl_to_vhcache(mdi_vhci_cache_t *vhcache, nvlist_t *nvl,
    mdi_vhcache_phci_t *cphci_list[])
{
        nvpair_t *nvp = NULL;
        nvlist_t *paddrnvl;
        mdi_vhcache_client_t *cct;

        while ((nvp = nvlist_next_nvpair(nvl, nvp)) != NULL) {
                ASSERT(nvpair_type(nvp) == DATA_TYPE_NVLIST);
                cct = kmem_zalloc(sizeof (*cct), KM_SLEEP);
                cct->cct_name_addr = i_ddi_strdup(nvpair_name(nvp), KM_SLEEP);
                (void) nvpair_value_nvlist(nvp, &paddrnvl);
                paddrnvl_to_vhcache(paddrnvl, cphci_list, cct);
                /* the client must contain at least one path */
                ASSERT(cct->cct_cpi_head != NULL);

                enqueue_vhcache_client(vhcache, cct);
                (void) mod_hash_insert(vhcache->vhcache_client_hash,
                    (mod_hash_key_t)cct->cct_name_addr, (mod_hash_val_t)cct);
        }
}

/*
 * Copy the contents of the main nvlist to vhci cache.
 *
 * VHCI busconfig cached data is stored in the form of a nvlist on the disk.
 * The nvlist contains the mappings between the vhci client addresses and
 * their corresponding phci client addresses.
 *
 * The structure of the nvlist is as follows:
 *
 * Main nvlist:
 *      NAME            TYPE            DATA
 *      version         int32           version number
 *      phcis           string array    array of phci paths
 *      clientaddrmap   nvlist_t        c2paddrs_nvl (see below)
 *
 * structure of c2paddrs_nvl:
 *      NAME            TYPE            DATA
 *      caddr1          nvlist_t        paddrs_nvl1
 *      caddr2          nvlist_t        paddrs_nvl2
 *      ...
 * where caddr1, caddr2, ... are vhci client name and addresses in the
 * form of "<clientname>@<clientaddress>".
 * (for example: "ssd@2000002037cd9f72");
 * paddrs_nvl1, paddrs_nvl2, .. are nvlists that contain path information.
 *
 * structure of paddrs_nvl:
 *      NAME            TYPE            DATA
 *      pi_addr1        uint32_array    (phci-id, cpi_flags)
 *      pi_addr2        uint32_array    (phci-id, cpi_flags)
 *      ...
 * where pi_addr1, pi_addr2, ... are bus specific addresses of pathinfo nodes
 * (so called pi_addrs, for example: "w2100002037cd9f72,0");
 * phci-ids are integers that identify pHCIs to which the
 * the bus specific address belongs to. These integers are used as an index
 * into to the phcis string array in the main nvlist to get the pHCI path.
 */
static int
mainnvl_to_vhcache(mdi_vhci_cache_t *vhcache, nvlist_t *nvl)
{
        char **phcis, **phci_namep;
        uint_t nphcis;
        mdi_vhcache_phci_t *cphci, **cphci_list;
        nvlist_t *caddrmapnvl;
        int32_t ver;
        int i;
        size_t cphci_list_size;

        ASSERT(RW_WRITE_HELD(&vhcache->vhcache_lock));

        if (nvlist_lookup_int32(nvl, MDI_NVPNAME_VERSION, &ver) != 0 ||
            ver != MDI_VHCI_CACHE_VERSION)
                return (MDI_FAILURE);

        if (nvlist_lookup_string_array(nvl, MDI_NVPNAME_PHCIS, &phcis,
            &nphcis) != 0)
                return (MDI_SUCCESS);

        ASSERT(nphcis > 0);

        cphci_list_size = sizeof (mdi_vhcache_phci_t *) * nphcis;
        cphci_list = kmem_alloc(cphci_list_size, KM_SLEEP);
        for (i = 0, phci_namep = phcis; i < nphcis; i++, phci_namep++) {
                cphci = kmem_zalloc(sizeof (mdi_vhcache_phci_t), KM_SLEEP);
                cphci->cphci_path = i_ddi_strdup(*phci_namep, KM_SLEEP);
                enqueue_vhcache_phci(vhcache, cphci);
                cphci_list[i] = cphci;
        }

        ASSERT(vhcache->vhcache_phci_head != NULL);

        if (nvlist_lookup_nvlist(nvl, MDI_NVPNAME_CTADDRMAP, &caddrmapnvl) == 0)
                caddrmapnvl_to_vhcache(vhcache, caddrmapnvl, cphci_list);

        kmem_free(cphci_list, cphci_list_size);
        return (MDI_SUCCESS);
}

/*
 * Build paddrnvl for the specified client using the information in the
 * vhci cache and add it to the caddrmapnnvl.
 * Returns 0 on success, errno on failure.
 */
static int
vhcache_to_paddrnvl(mdi_vhci_cache_t *vhcache, mdi_vhcache_client_t *cct,
    nvlist_t *caddrmapnvl)
{
        mdi_vhcache_pathinfo_t *cpi;
        nvlist_t *nvl;
        int err;
        uint32_t val[2];

        ASSERT(RW_LOCK_HELD(&vhcache->vhcache_lock));

        if ((err = nvlist_alloc(&nvl, 0, KM_SLEEP)) != 0)
                return (err);

        for (cpi = cct->cct_cpi_head; cpi != NULL; cpi = cpi->cpi_next) {
                val[0] = cpi->cpi_cphci->cphci_id;
                val[1] = cpi->cpi_flags;
                if ((err = nvlist_add_uint32_array(nvl, cpi->cpi_addr, val, 2))
                    != 0)
                        goto out;
        }

        err = nvlist_add_nvlist(caddrmapnvl, cct->cct_name_addr, nvl);
out:
        nvlist_free(nvl);
        return (err);
}

/*
 * Build caddrmapnvl using the information in the vhci cache
 * and add it to the mainnvl.
 * Returns 0 on success, errno on failure.
 */
static int
vhcache_to_caddrmapnvl(mdi_vhci_cache_t *vhcache, nvlist_t *mainnvl)
{
        mdi_vhcache_client_t *cct;
        nvlist_t *nvl;
        int err;

        ASSERT(RW_LOCK_HELD(&vhcache->vhcache_lock));

        if ((err = nvlist_alloc(&nvl, NV_UNIQUE_NAME, KM_SLEEP)) != 0)
                return (err);

        for (cct = vhcache->vhcache_client_head; cct != NULL;
            cct = cct->cct_next) {
                if ((err = vhcache_to_paddrnvl(vhcache, cct, nvl)) != 0)
                        goto out;
        }

        err = nvlist_add_nvlist(mainnvl, MDI_NVPNAME_CTADDRMAP, nvl);
out:
        nvlist_free(nvl);
        return (err);
}

/*
 * Build nvlist using the information in the vhci cache.
 * See the comment in mainnvl_to_vhcache() for the format of the nvlist.
 * Returns nvl on success, NULL on failure.
 */
static nvlist_t *
vhcache_to_mainnvl(mdi_vhci_cache_t *vhcache)
{
        mdi_vhcache_phci_t *cphci;
        uint_t phci_count;
        char **phcis;
        nvlist_t *nvl;
        int err, i;

        if ((err = nvlist_alloc(&nvl, NV_UNIQUE_NAME, KM_SLEEP)) != 0) {
                nvl = NULL;
                goto out;
        }

        if ((err = nvlist_add_int32(nvl, MDI_NVPNAME_VERSION,
            MDI_VHCI_CACHE_VERSION)) != 0)
                goto out;

        rw_enter(&vhcache->vhcache_lock, RW_READER);
        if (vhcache->vhcache_phci_head == NULL) {
                rw_exit(&vhcache->vhcache_lock);
                return (nvl);
        }

        phci_count = 0;
        for (cphci = vhcache->vhcache_phci_head; cphci != NULL;
            cphci = cphci->cphci_next)
                cphci->cphci_id = phci_count++;

        /* build phci pathname list */
        phcis = kmem_alloc(sizeof (char *) * phci_count, KM_SLEEP);
        for (cphci = vhcache->vhcache_phci_head, i = 0; cphci != NULL;
            cphci = cphci->cphci_next, i++)
                phcis[i] = i_ddi_strdup(cphci->cphci_path, KM_SLEEP);

        err = nvlist_add_string_array(nvl, MDI_NVPNAME_PHCIS, phcis,
            phci_count);
        free_string_array(phcis, phci_count);

        if (err == 0 &&
            (err = vhcache_to_caddrmapnvl(vhcache, nvl)) == 0) {
                rw_exit(&vhcache->vhcache_lock);
                return (nvl);
        }

        rw_exit(&vhcache->vhcache_lock);
out:
        nvlist_free(nvl);
        return (NULL);
}

/*
 * Lookup vhcache phci structure for the specified phci path.
 */
static mdi_vhcache_phci_t *
lookup_vhcache_phci_by_name(mdi_vhci_cache_t *vhcache, char *phci_path)
{
        mdi_vhcache_phci_t *cphci;

        ASSERT(RW_LOCK_HELD(&vhcache->vhcache_lock));

        for (cphci = vhcache->vhcache_phci_head; cphci != NULL;
            cphci = cphci->cphci_next) {
                if (strcmp(cphci->cphci_path, phci_path) == 0)
                        return (cphci);
        }

        return (NULL);
}

/*
 * Lookup vhcache phci structure for the specified phci.
 */
static mdi_vhcache_phci_t *
lookup_vhcache_phci_by_addr(mdi_vhci_cache_t *vhcache, mdi_phci_t *ph)
{
        mdi_vhcache_phci_t *cphci;

        ASSERT(RW_LOCK_HELD(&vhcache->vhcache_lock));

        for (cphci = vhcache->vhcache_phci_head; cphci != NULL;
            cphci = cphci->cphci_next) {
                if (cphci->cphci_phci == ph)
                        return (cphci);
        }

        return (NULL);
}

/*
 * Add the specified phci to the vhci cache if not already present.
 */
static void
vhcache_phci_add(mdi_vhci_config_t *vhc, mdi_phci_t *ph)
{
        mdi_vhci_cache_t *vhcache = &vhc->vhc_vhcache;
        mdi_vhcache_phci_t *cphci;
        char *pathname;
        int cache_updated;

        rw_enter(&vhcache->vhcache_lock, RW_WRITER);

        pathname = kmem_alloc(MAXPATHLEN, KM_SLEEP);
        (void) ddi_pathname(ph->ph_dip, pathname);
        if ((cphci = lookup_vhcache_phci_by_name(vhcache, pathname))
            != NULL) {
                cphci->cphci_phci = ph;
                cache_updated = 0;
        } else {
                cphci = kmem_zalloc(sizeof (*cphci), KM_SLEEP);
                cphci->cphci_path = i_ddi_strdup(pathname, KM_SLEEP);
                cphci->cphci_phci = ph;
                enqueue_vhcache_phci(vhcache, cphci);
                cache_updated = 1;
        }

        rw_exit(&vhcache->vhcache_lock);

        /*
         * Since a new phci has been added, reset
         * vhc_path_discovery_cutoff_time to allow for discovery of paths
         * during next vhcache_discover_paths().
         */
        mutex_enter(&vhc->vhc_lock);
        vhc->vhc_path_discovery_cutoff_time = 0;
        mutex_exit(&vhc->vhc_lock);

        kmem_free(pathname, MAXPATHLEN);
        if (cache_updated)
                vhcache_dirty(vhc);
}

/*
 * Remove the reference to the specified phci from the vhci cache.
 */
static void
vhcache_phci_remove(mdi_vhci_config_t *vhc, mdi_phci_t *ph)
{
        mdi_vhci_cache_t *vhcache = &vhc->vhc_vhcache;
        mdi_vhcache_phci_t *cphci;

        rw_enter(&vhcache->vhcache_lock, RW_WRITER);
        if ((cphci = lookup_vhcache_phci_by_addr(vhcache, ph)) != NULL) {
                /* do not remove the actual mdi_vhcache_phci structure */
                cphci->cphci_phci = NULL;
        }
        rw_exit(&vhcache->vhcache_lock);
}

static void
init_vhcache_lookup_token(mdi_vhcache_lookup_token_t *dst,
    mdi_vhcache_lookup_token_t *src)
{
        if (src == NULL) {
                dst->lt_cct = NULL;
                dst->lt_cct_lookup_time = 0;
        } else {
                dst->lt_cct = src->lt_cct;
                dst->lt_cct_lookup_time = src->lt_cct_lookup_time;
        }
}

/*
 * Look up vhcache client for the specified client.
 */
static mdi_vhcache_client_t *
lookup_vhcache_client(mdi_vhci_cache_t *vhcache, char *ct_name, char *ct_addr,
    mdi_vhcache_lookup_token_t *token)
{
        mod_hash_val_t hv;
        char *name_addr;
        int len;

        ASSERT(RW_LOCK_HELD(&vhcache->vhcache_lock));

        /*
         * If no vhcache clean occurred since the last lookup, we can
         * simply return the cct from the last lookup operation.
         * It works because ccts are never freed except during the vhcache
         * cleanup operation.
         */
        if (token != NULL &&
            vhcache->vhcache_clean_time < token->lt_cct_lookup_time)
                return (token->lt_cct);

        name_addr = vhcache_mknameaddr(ct_name, ct_addr, &len);
        if (mod_hash_find(vhcache->vhcache_client_hash,
            (mod_hash_key_t)name_addr, &hv) == 0) {
                if (token) {
                        token->lt_cct = (mdi_vhcache_client_t *)hv;
                        token->lt_cct_lookup_time = ddi_get_lbolt64();
                }
        } else {
                if (token) {
                        token->lt_cct = NULL;
                        token->lt_cct_lookup_time = 0;
                }
                hv = NULL;
        }
        kmem_free(name_addr, len);
        return ((mdi_vhcache_client_t *)hv);
}

/*
 * Add the specified path to the vhci cache if not already present.
 * Also add the vhcache client for the client corresponding to this path
 * if it doesn't already exist.
 */
static void
vhcache_pi_add(mdi_vhci_config_t *vhc, struct mdi_pathinfo *pip)
{
        mdi_vhci_cache_t *vhcache = &vhc->vhc_vhcache;
        mdi_vhcache_client_t *cct;
        mdi_vhcache_pathinfo_t *cpi;
        mdi_phci_t *ph = pip->pi_phci;
        mdi_client_t *ct = pip->pi_client;
        int cache_updated = 0;

        rw_enter(&vhcache->vhcache_lock, RW_WRITER);

        /* if vhcache client for this pip doesn't already exist, add it */
        if ((cct = lookup_vhcache_client(vhcache, ct->ct_drvname, ct->ct_guid,
            NULL)) == NULL) {
                cct = kmem_zalloc(sizeof (*cct), KM_SLEEP);
                cct->cct_name_addr = vhcache_mknameaddr(ct->ct_drvname,
                    ct->ct_guid, NULL);
                enqueue_vhcache_client(vhcache, cct);
                (void) mod_hash_insert(vhcache->vhcache_client_hash,
                    (mod_hash_key_t)cct->cct_name_addr, (mod_hash_val_t)cct);
                cache_updated = 1;
        }

        for (cpi = cct->cct_cpi_head; cpi != NULL; cpi = cpi->cpi_next) {
                if (cpi->cpi_cphci->cphci_phci == ph &&
                    strcmp(cpi->cpi_addr, pip->pi_addr) == 0) {
                        cpi->cpi_pip = pip;
                        if (cpi->cpi_flags & MDI_CPI_HINT_PATH_DOES_NOT_EXIST) {
                                cpi->cpi_flags &=
                                    ~MDI_CPI_HINT_PATH_DOES_NOT_EXIST;
                                sort_vhcache_paths(cct);
                                cache_updated = 1;
                        }
                        break;
                }
        }

        if (cpi == NULL) {
                cpi = kmem_zalloc(sizeof (*cpi), KM_SLEEP);
                cpi->cpi_addr = i_ddi_strdup(pip->pi_addr, KM_SLEEP);
                cpi->cpi_cphci = lookup_vhcache_phci_by_addr(vhcache, ph);
                ASSERT(cpi->cpi_cphci != NULL);
                cpi->cpi_pip = pip;
                enqueue_vhcache_pathinfo(cct, cpi);
                cache_updated = 1;
        }

        rw_exit(&vhcache->vhcache_lock);

        if (cache_updated)
                vhcache_dirty(vhc);
}

/*
 * Remove the reference to the specified path from the vhci cache.
 */
static void
vhcache_pi_remove(mdi_vhci_config_t *vhc, struct mdi_pathinfo *pip)
{
        mdi_vhci_cache_t *vhcache = &vhc->vhc_vhcache;
        mdi_client_t *ct = pip->pi_client;
        mdi_vhcache_client_t *cct;
        mdi_vhcache_pathinfo_t *cpi;

        rw_enter(&vhcache->vhcache_lock, RW_WRITER);
        if ((cct = lookup_vhcache_client(vhcache, ct->ct_drvname, ct->ct_guid,
            NULL)) != NULL) {
                for (cpi = cct->cct_cpi_head; cpi != NULL;
                    cpi = cpi->cpi_next) {
                        if (cpi->cpi_pip == pip) {
                                cpi->cpi_pip = NULL;
                                break;
                        }
                }
        }
        rw_exit(&vhcache->vhcache_lock);
}

/*
 * Flush the vhci cache to disk.
 * Returns MDI_SUCCESS on success, MDI_FAILURE on failure.
 */
static int
flush_vhcache(mdi_vhci_config_t *vhc, int force_flag)
{
        nvlist_t *nvl;
        int err;
        int rv;

        /*
         * It is possible that the system may shutdown before
         * i_ddi_io_initialized (during stmsboot for example). To allow for
         * flushing the cache in this case do not check for
         * i_ddi_io_initialized when force flag is set.
         */
        if (force_flag == 0 && !i_ddi_io_initialized())
                return (MDI_FAILURE);

        if ((nvl = vhcache_to_mainnvl(&vhc->vhc_vhcache)) != NULL) {
                err = fwrite_nvlist(vhc->vhc_vhcache_filename, nvl);
                nvlist_free(nvl);
        } else
                err = EFAULT;

        rv = MDI_SUCCESS;
        mutex_enter(&vhc->vhc_lock);
        if (err != 0) {
                if (err == EROFS) {
                        vhc->vhc_flags |= MDI_VHC_READONLY_FS;
                        vhc->vhc_flags &= ~(MDI_VHC_VHCACHE_FLUSH_ERROR |
                            MDI_VHC_VHCACHE_DIRTY);
                } else {
                        if (!(vhc->vhc_flags & MDI_VHC_VHCACHE_FLUSH_ERROR)) {
                                cmn_err(CE_CONT, "%s: update failed\n",
                                    vhc->vhc_vhcache_filename);
                                vhc->vhc_flags |= MDI_VHC_VHCACHE_FLUSH_ERROR;
                        }
                        rv = MDI_FAILURE;
                }
        } else if (vhc->vhc_flags & MDI_VHC_VHCACHE_FLUSH_ERROR) {
                cmn_err(CE_CONT,
                    "%s: update now ok\n", vhc->vhc_vhcache_filename);
                vhc->vhc_flags &= ~MDI_VHC_VHCACHE_FLUSH_ERROR;
        }
        mutex_exit(&vhc->vhc_lock);

        return (rv);
}

/*
 * Call flush_vhcache() to flush the vhci cache at the scheduled time.
 * Exits itself if left idle for the idle timeout period.
 */
static void
vhcache_flush_thread(void *arg)
{
        mdi_vhci_config_t *vhc = (mdi_vhci_config_t *)arg;
        clock_t idle_time, quit_at_ticks;
        callb_cpr_t cprinfo;

        /* number of seconds to sleep idle before exiting */
        idle_time = mdi_vhcache_flush_daemon_idle_time * TICKS_PER_SECOND;

        CALLB_CPR_INIT(&cprinfo, &vhc->vhc_lock, callb_generic_cpr,
            "mdi_vhcache_flush");
        mutex_enter(&vhc->vhc_lock);
        for (; ; ) {
                while (!(vhc->vhc_flags & MDI_VHC_EXIT) &&
                    (vhc->vhc_flags & MDI_VHC_VHCACHE_DIRTY)) {
                        if (ddi_get_lbolt() < vhc->vhc_flush_at_ticks) {
                                CALLB_CPR_SAFE_BEGIN(&cprinfo);
                                (void) cv_timedwait(&vhc->vhc_cv,
                                    &vhc->vhc_lock, vhc->vhc_flush_at_ticks);
                                CALLB_CPR_SAFE_END(&cprinfo, &vhc->vhc_lock);
                        } else {
                                vhc->vhc_flags &= ~MDI_VHC_VHCACHE_DIRTY;
                                mutex_exit(&vhc->vhc_lock);

                                if (flush_vhcache(vhc, 0) != MDI_SUCCESS)
                                        vhcache_dirty(vhc);

                                mutex_enter(&vhc->vhc_lock);
                        }
                }

                quit_at_ticks = ddi_get_lbolt() + idle_time;

                while (!(vhc->vhc_flags & MDI_VHC_EXIT) &&
                    !(vhc->vhc_flags & MDI_VHC_VHCACHE_DIRTY) &&
                    ddi_get_lbolt() < quit_at_ticks) {
                        CALLB_CPR_SAFE_BEGIN(&cprinfo);
                        (void) cv_timedwait(&vhc->vhc_cv, &vhc->vhc_lock,
                            quit_at_ticks);
                        CALLB_CPR_SAFE_END(&cprinfo, &vhc->vhc_lock);
                }

                if ((vhc->vhc_flags & MDI_VHC_EXIT) ||
                    !(vhc->vhc_flags & MDI_VHC_VHCACHE_DIRTY))
                        goto out;
        }

out:
        vhc->vhc_flags &= ~MDI_VHC_VHCACHE_FLUSH_THREAD;
        /* CALLB_CPR_EXIT releases the vhc->vhc_lock */
        CALLB_CPR_EXIT(&cprinfo);
}

/*
 * Make vhci cache dirty and schedule flushing by vhcache flush thread.
 */
static void
vhcache_dirty(mdi_vhci_config_t *vhc)
{
        mdi_vhci_cache_t *vhcache = &vhc->vhc_vhcache;
        int create_thread;

        rw_enter(&vhcache->vhcache_lock, RW_READER);
        /* do not flush cache until the cache is fully built */
        if (!(vhcache->vhcache_flags & MDI_VHCI_CACHE_SETUP_DONE)) {
                rw_exit(&vhcache->vhcache_lock);
                return;
        }
        rw_exit(&vhcache->vhcache_lock);

        mutex_enter(&vhc->vhc_lock);
        if (vhc->vhc_flags & MDI_VHC_READONLY_FS) {
                mutex_exit(&vhc->vhc_lock);
                return;
        }

        vhc->vhc_flags |= MDI_VHC_VHCACHE_DIRTY;
        vhc->vhc_flush_at_ticks = ddi_get_lbolt() +
            mdi_vhcache_flush_delay * TICKS_PER_SECOND;
        if (vhc->vhc_flags & MDI_VHC_VHCACHE_FLUSH_THREAD) {
                cv_broadcast(&vhc->vhc_cv);
                create_thread = 0;
        } else {
                vhc->vhc_flags |= MDI_VHC_VHCACHE_FLUSH_THREAD;
                create_thread = 1;
        }
        mutex_exit(&vhc->vhc_lock);

        if (create_thread)
                (void) thread_create(NULL, 0, vhcache_flush_thread, vhc,
                    0, &p0, TS_RUN, minclsyspri);
}

/*
 * phci bus config structure - one for for each phci bus config operation that
 * we initiate on behalf of a vhci.
 */
typedef struct mdi_phci_bus_config_s {
        char *phbc_phci_path;
        struct mdi_vhci_bus_config_s *phbc_vhbusconfig; /* vhci bus config */
        struct mdi_phci_bus_config_s *phbc_next;
} mdi_phci_bus_config_t;

/* vhci bus config structure - one for each vhci bus config operation */
typedef struct mdi_vhci_bus_config_s {
        ddi_bus_config_op_t vhbc_op;    /* bus config op */
        major_t vhbc_op_major;          /* bus config op major */
        uint_t vhbc_op_flags;           /* bus config op flags */
        kmutex_t vhbc_lock;
        kcondvar_t vhbc_cv;
        int vhbc_thr_count;
} mdi_vhci_bus_config_t;

/*
 * bus config the specified phci
 */
static void
bus_config_phci(void *arg)
{
        mdi_phci_bus_config_t *phbc = (mdi_phci_bus_config_t *)arg;
        mdi_vhci_bus_config_t *vhbc = phbc->phbc_vhbusconfig;
        dev_info_t *ph_dip;

        /*
         * first configure all path components upto phci and then configure
         * the phci children.
         */
        if ((ph_dip = e_ddi_hold_devi_by_path(phbc->phbc_phci_path, 0))
            != NULL) {
                if (vhbc->vhbc_op == BUS_CONFIG_DRIVER ||
                    vhbc->vhbc_op == BUS_UNCONFIG_DRIVER) {
                        (void) ndi_devi_config_driver(ph_dip,
                            vhbc->vhbc_op_flags,
                            vhbc->vhbc_op_major);
                } else
                        (void) ndi_devi_config(ph_dip,
                            vhbc->vhbc_op_flags);

                /* release the hold that e_ddi_hold_devi_by_path() placed */
                ndi_rele_devi(ph_dip);
        }

        kmem_free(phbc->phbc_phci_path, strlen(phbc->phbc_phci_path) + 1);
        kmem_free(phbc, sizeof (*phbc));

        mutex_enter(&vhbc->vhbc_lock);
        vhbc->vhbc_thr_count--;
        if (vhbc->vhbc_thr_count == 0)
                cv_broadcast(&vhbc->vhbc_cv);
        mutex_exit(&vhbc->vhbc_lock);
}

/*
 * Bus config all phcis associated with the vhci in parallel.
 * op must be BUS_CONFIG_DRIVER or BUS_CONFIG_ALL.
 */
static void
bus_config_all_phcis(mdi_vhci_cache_t *vhcache, uint_t flags,
    ddi_bus_config_op_t op, major_t maj)
{
        mdi_phci_bus_config_t *phbc_head = NULL, *phbc, *phbc_next;
        mdi_vhci_bus_config_t *vhbc;
        mdi_vhcache_phci_t *cphci;

        rw_enter(&vhcache->vhcache_lock, RW_READER);
        if (vhcache->vhcache_phci_head == NULL) {
                rw_exit(&vhcache->vhcache_lock);
                return;
        }

        vhbc = kmem_zalloc(sizeof (*vhbc), KM_SLEEP);

        for (cphci = vhcache->vhcache_phci_head; cphci != NULL;
            cphci = cphci->cphci_next) {
                /* skip phcis that haven't attached before root is available */
                if (!modrootloaded && (cphci->cphci_phci == NULL))
                        continue;
                phbc = kmem_zalloc(sizeof (*phbc), KM_SLEEP);
                phbc->phbc_phci_path = i_ddi_strdup(cphci->cphci_path,
                    KM_SLEEP);
                phbc->phbc_vhbusconfig = vhbc;
                phbc->phbc_next = phbc_head;
                phbc_head = phbc;
                vhbc->vhbc_thr_count++;
        }
        rw_exit(&vhcache->vhcache_lock);

        vhbc->vhbc_op = op;
        vhbc->vhbc_op_major = maj;
        vhbc->vhbc_op_flags = NDI_NO_EVENT |
            (flags & (NDI_CONFIG_REPROBE | NDI_DRV_CONF_REPROBE));
        mutex_init(&vhbc->vhbc_lock, NULL, MUTEX_DEFAULT, NULL);
        cv_init(&vhbc->vhbc_cv, NULL, CV_DRIVER, NULL);

        /* now create threads to initiate bus config on all phcis in parallel */
        for (phbc = phbc_head; phbc != NULL; phbc = phbc_next) {
                phbc_next = phbc->phbc_next;
                if (mdi_mtc_off)
                        bus_config_phci((void *)phbc);
                else
                        (void) thread_create(NULL, 0, bus_config_phci, phbc,
                            0, &p0, TS_RUN, minclsyspri);
        }

        mutex_enter(&vhbc->vhbc_lock);
        /* wait until all threads exit */
        while (vhbc->vhbc_thr_count > 0)
                cv_wait(&vhbc->vhbc_cv, &vhbc->vhbc_lock);
        mutex_exit(&vhbc->vhbc_lock);

        mutex_destroy(&vhbc->vhbc_lock);
        cv_destroy(&vhbc->vhbc_cv);
        kmem_free(vhbc, sizeof (*vhbc));
}

/*
 * Single threaded version of bus_config_all_phcis()
 */
static void
st_bus_config_all_phcis(mdi_vhci_config_t *vhc, uint_t flags,
    ddi_bus_config_op_t op, major_t maj)
{
        mdi_vhci_cache_t *vhcache = &vhc->vhc_vhcache;

        single_threaded_vhconfig_enter(vhc);
        bus_config_all_phcis(vhcache, flags, op, maj);
        single_threaded_vhconfig_exit(vhc);
}

/*
 * Perform BUS_CONFIG_ONE on the specified child of the phci.
 * The path includes the child component in addition to the phci path.
 */
static int
bus_config_one_phci_child(char *path)
{
        dev_info_t *ph_dip, *child;
        char *devnm;
        int rv = MDI_FAILURE;

        /* extract the child component of the phci */
        devnm = strrchr(path, '/');
        *devnm++ = '\0';

        /*
         * first configure all path components upto phci and then
         * configure the phci child.
         */
        if ((ph_dip = e_ddi_hold_devi_by_path(path, 0)) != NULL) {
                if (ndi_devi_config_one(ph_dip, devnm, &child, NDI_NO_EVENT) ==
                    NDI_SUCCESS) {
                        /*
                         * release the hold that ndi_devi_config_one() placed
                         */
                        ndi_rele_devi(child);
                        rv = MDI_SUCCESS;
                }

                /* release the hold that e_ddi_hold_devi_by_path() placed */
                ndi_rele_devi(ph_dip);
        }

        devnm--;
        *devnm = '/';
        return (rv);
}

/*
 * Build a list of phci client paths for the specified vhci client.
 * The list includes only those phci client paths which aren't configured yet.
 */
static mdi_phys_path_t *
build_phclient_path_list(mdi_vhcache_client_t *cct, char *ct_name)
{
        mdi_vhcache_pathinfo_t *cpi;
        mdi_phys_path_t *pp_head = NULL, *pp_tail = NULL, *pp;
        int config_path, len;

        for (cpi = cct->cct_cpi_head; cpi != NULL; cpi = cpi->cpi_next) {
                /*
                 * include only those paths that aren't configured.
                 */
                config_path = 0;
                if (cpi->cpi_pip == NULL)
                        config_path = 1;
                else {
                        MDI_PI_LOCK(cpi->cpi_pip);
                        if (MDI_PI_IS_INIT(cpi->cpi_pip))
                                config_path = 1;
                        MDI_PI_UNLOCK(cpi->cpi_pip);
                }

                if (config_path) {
                        pp = kmem_alloc(sizeof (*pp), KM_SLEEP);
                        len = strlen(cpi->cpi_cphci->cphci_path) +
                            strlen(ct_name) + strlen(cpi->cpi_addr) + 3;
                        pp->phys_path = kmem_alloc(len, KM_SLEEP);
                        (void) snprintf(pp->phys_path, len, "%s/%s@%s",
                            cpi->cpi_cphci->cphci_path, ct_name,
                            cpi->cpi_addr);
                        pp->phys_path_next = NULL;

                        if (pp_head == NULL)
                                pp_head = pp;
                        else
                                pp_tail->phys_path_next = pp;
                        pp_tail = pp;
                }
        }

        return (pp_head);
}

/*
 * Free the memory allocated for phci client path list.
 */
static void
free_phclient_path_list(mdi_phys_path_t *pp_head)
{
        mdi_phys_path_t *pp, *pp_next;

        for (pp = pp_head; pp != NULL; pp = pp_next) {
                pp_next = pp->phys_path_next;
                kmem_free(pp->phys_path, strlen(pp->phys_path) + 1);
                kmem_free(pp, sizeof (*pp));
        }
}

/*
 * Allocated async client structure and initialize with the specified values.
 */
static mdi_async_client_config_t *
alloc_async_client_config(char *ct_name, char *ct_addr,
    mdi_phys_path_t *pp_head, mdi_vhcache_lookup_token_t *tok)
{
        mdi_async_client_config_t *acc;

        acc = kmem_alloc(sizeof (*acc), KM_SLEEP);
        acc->acc_ct_name = i_ddi_strdup(ct_name, KM_SLEEP);
        acc->acc_ct_addr = i_ddi_strdup(ct_addr, KM_SLEEP);
        acc->acc_phclient_path_list_head = pp_head;
        init_vhcache_lookup_token(&acc->acc_token, tok);
        acc->acc_next = NULL;
        return (acc);
}

/*
 * Free the memory allocated for the async client structure and their members.
 */
static void
free_async_client_config(mdi_async_client_config_t *acc)
{
        if (acc->acc_phclient_path_list_head)
                free_phclient_path_list(acc->acc_phclient_path_list_head);
        kmem_free(acc->acc_ct_name, strlen(acc->acc_ct_name) + 1);
        kmem_free(acc->acc_ct_addr, strlen(acc->acc_ct_addr) + 1);
        kmem_free(acc, sizeof (*acc));
}

/*
 * Sort vhcache pathinfos (cpis) of the specified client.
 * All cpis which do not have MDI_CPI_HINT_PATH_DOES_NOT_EXIST
 * flag set come at the beginning of the list. All cpis which have this
 * flag set come at the end of the list.
 */
static void
sort_vhcache_paths(mdi_vhcache_client_t *cct)
{
        mdi_vhcache_pathinfo_t *cpi, *cpi_next, *cpi_head;

        cpi_head = cct->cct_cpi_head;
        cct->cct_cpi_head = cct->cct_cpi_tail = NULL;
        for (cpi = cpi_head; cpi != NULL; cpi = cpi_next) {
                cpi_next = cpi->cpi_next;
                enqueue_vhcache_pathinfo(cct, cpi);
        }
}

/*
 * Verify whether MDI_CPI_HINT_PATH_DOES_NOT_EXIST flag setting is correct for
 * every vhcache pathinfo of the specified client. If not adjust the flag
 * setting appropriately.
 *
 * Note that MDI_CPI_HINT_PATH_DOES_NOT_EXIST flag is persisted in the
 * on-disk vhci cache. So every time this flag is updated the cache must be
 * flushed.
 */
static void
adjust_sort_vhcache_paths(mdi_vhci_config_t *vhc, char *ct_name, char *ct_addr,
    mdi_vhcache_lookup_token_t *tok)
{
        mdi_vhci_cache_t *vhcache = &vhc->vhc_vhcache;
        mdi_vhcache_client_t *cct;
        mdi_vhcache_pathinfo_t *cpi;

        rw_enter(&vhcache->vhcache_lock, RW_READER);
        if ((cct = lookup_vhcache_client(vhcache, ct_name, ct_addr, tok))
            == NULL) {
                rw_exit(&vhcache->vhcache_lock);
                return;
        }

        /*
         * to avoid unnecessary on-disk cache updates, first check if an
         * update is really needed. If no update is needed simply return.
         */
        for (cpi = cct->cct_cpi_head; cpi != NULL; cpi = cpi->cpi_next) {
                if ((cpi->cpi_pip != NULL &&
                    (cpi->cpi_flags & MDI_CPI_HINT_PATH_DOES_NOT_EXIST)) ||
                    (cpi->cpi_pip == NULL &&
                    !(cpi->cpi_flags & MDI_CPI_HINT_PATH_DOES_NOT_EXIST))) {
                        break;
                }
        }
        if (cpi == NULL) {
                rw_exit(&vhcache->vhcache_lock);
                return;
        }

        if (rw_tryupgrade(&vhcache->vhcache_lock) == 0) {
                rw_exit(&vhcache->vhcache_lock);
                rw_enter(&vhcache->vhcache_lock, RW_WRITER);
                if ((cct = lookup_vhcache_client(vhcache, ct_name, ct_addr,
                    tok)) == NULL) {
                        rw_exit(&vhcache->vhcache_lock);
                        return;
                }
        }

        for (cpi = cct->cct_cpi_head; cpi != NULL; cpi = cpi->cpi_next) {
                if (cpi->cpi_pip != NULL)
                        cpi->cpi_flags &= ~MDI_CPI_HINT_PATH_DOES_NOT_EXIST;
                else
                        cpi->cpi_flags |= MDI_CPI_HINT_PATH_DOES_NOT_EXIST;
        }
        sort_vhcache_paths(cct);

        rw_exit(&vhcache->vhcache_lock);
        vhcache_dirty(vhc);
}

/*
 * Configure all specified paths of the client.
 */
static void
config_client_paths_sync(mdi_vhci_config_t *vhc, char *ct_name, char *ct_addr,
    mdi_phys_path_t *pp_head, mdi_vhcache_lookup_token_t *tok)
{
        mdi_phys_path_t *pp;

        for (pp = pp_head; pp != NULL; pp = pp->phys_path_next)
                (void) bus_config_one_phci_child(pp->phys_path);
        adjust_sort_vhcache_paths(vhc, ct_name, ct_addr, tok);
}

/*
 * Dequeue elements from vhci async client config list and bus configure
 * their corresponding phci clients.
 */
static void
config_client_paths_thread(void *arg)
{
        mdi_vhci_config_t *vhc = (mdi_vhci_config_t *)arg;
        mdi_async_client_config_t *acc;
        clock_t quit_at_ticks;
        clock_t idle_time = mdi_async_config_idle_time * TICKS_PER_SECOND;
        callb_cpr_t cprinfo;

        CALLB_CPR_INIT(&cprinfo, &vhc->vhc_lock, callb_generic_cpr,
            "mdi_config_client_paths");

        for (; ; ) {
                quit_at_ticks = ddi_get_lbolt() + idle_time;

                mutex_enter(&vhc->vhc_lock);
                while (!(vhc->vhc_flags & MDI_VHC_EXIT) &&
                    vhc->vhc_acc_list_head == NULL &&
                    ddi_get_lbolt() < quit_at_ticks) {
                        CALLB_CPR_SAFE_BEGIN(&cprinfo);
                        (void) cv_timedwait(&vhc->vhc_cv, &vhc->vhc_lock,
                            quit_at_ticks);
                        CALLB_CPR_SAFE_END(&cprinfo, &vhc->vhc_lock);
                }

                if ((vhc->vhc_flags & MDI_VHC_EXIT) ||
                    vhc->vhc_acc_list_head == NULL)
                        goto out;

                acc = vhc->vhc_acc_list_head;
                vhc->vhc_acc_list_head = acc->acc_next;
                if (vhc->vhc_acc_list_head == NULL)
                        vhc->vhc_acc_list_tail = NULL;
                vhc->vhc_acc_count--;
                mutex_exit(&vhc->vhc_lock);

                config_client_paths_sync(vhc, acc->acc_ct_name,
                    acc->acc_ct_addr, acc->acc_phclient_path_list_head,
                    &acc->acc_token);

                free_async_client_config(acc);
        }

out:
        vhc->vhc_acc_thrcount--;
        /* CALLB_CPR_EXIT releases the vhc->vhc_lock */
        CALLB_CPR_EXIT(&cprinfo);
}

/*
 * Arrange for all the phci client paths (pp_head) for the specified client
 * to be bus configured asynchronously by a thread.
 */
static void
config_client_paths_async(mdi_vhci_config_t *vhc, char *ct_name, char *ct_addr,
    mdi_phys_path_t *pp_head, mdi_vhcache_lookup_token_t *tok)
{
        mdi_async_client_config_t *acc, *newacc;
        int create_thread;

        if (pp_head == NULL)
                return;

        if (mdi_mtc_off) {
                config_client_paths_sync(vhc, ct_name, ct_addr, pp_head, tok);
                free_phclient_path_list(pp_head);
                return;
        }

        newacc = alloc_async_client_config(ct_name, ct_addr, pp_head, tok);
        ASSERT(newacc);

        mutex_enter(&vhc->vhc_lock);
        for (acc = vhc->vhc_acc_list_head; acc != NULL; acc = acc->acc_next) {
                if (strcmp(ct_name, acc->acc_ct_name) == 0 &&
                    strcmp(ct_addr, acc->acc_ct_addr) == 0) {
                        free_async_client_config(newacc);
                        mutex_exit(&vhc->vhc_lock);
                        return;
                }
        }

        if (vhc->vhc_acc_list_head == NULL)
                vhc->vhc_acc_list_head = newacc;
        else
                vhc->vhc_acc_list_tail->acc_next = newacc;
        vhc->vhc_acc_list_tail = newacc;
        vhc->vhc_acc_count++;
        if (vhc->vhc_acc_count <= vhc->vhc_acc_thrcount) {
                cv_broadcast(&vhc->vhc_cv);
                create_thread = 0;
        } else {
                vhc->vhc_acc_thrcount++;
                create_thread = 1;
        }
        mutex_exit(&vhc->vhc_lock);

        if (create_thread)
                (void) thread_create(NULL, 0, config_client_paths_thread, vhc,
                    0, &p0, TS_RUN, minclsyspri);
}

/*
 * Return number of online paths for the specified client.
 */
static int
nonline_paths(mdi_vhcache_client_t *cct)
{
        mdi_vhcache_pathinfo_t *cpi;
        int online_count = 0;

        for (cpi = cct->cct_cpi_head; cpi != NULL; cpi = cpi->cpi_next) {
                if (cpi->cpi_pip != NULL) {
                        MDI_PI_LOCK(cpi->cpi_pip);
                        if (cpi->cpi_pip->pi_state == MDI_PATHINFO_STATE_ONLINE)
                                online_count++;
                        MDI_PI_UNLOCK(cpi->cpi_pip);
                }
        }

        return (online_count);
}

/*
 * Bus configure all paths for the specified vhci client.
 * If at least one path for the client is already online, the remaining paths
 * will be configured asynchronously. Otherwise, it synchronously configures
 * the paths until at least one path is online and then rest of the paths
 * will be configured asynchronously.
 */
static void
config_client_paths(mdi_vhci_config_t *vhc, char *ct_name, char *ct_addr)
{
        mdi_vhci_cache_t *vhcache = &vhc->vhc_vhcache;
        mdi_phys_path_t *pp_head, *pp;
        mdi_vhcache_client_t *cct;
        mdi_vhcache_lookup_token_t tok;

        ASSERT(RW_LOCK_HELD(&vhcache->vhcache_lock));

        init_vhcache_lookup_token(&tok, NULL);

        if (ct_name == NULL || ct_addr == NULL ||
            (cct = lookup_vhcache_client(vhcache, ct_name, ct_addr, &tok))
            == NULL ||
            (pp_head = build_phclient_path_list(cct, ct_name)) == NULL) {
                rw_exit(&vhcache->vhcache_lock);
                return;
        }

        /* if at least one path is online, configure the rest asynchronously */
        if (nonline_paths(cct) > 0) {
                rw_exit(&vhcache->vhcache_lock);
                config_client_paths_async(vhc, ct_name, ct_addr, pp_head, &tok);
                return;
        }

        rw_exit(&vhcache->vhcache_lock);

        for (pp = pp_head; pp != NULL; pp = pp->phys_path_next) {
                if (bus_config_one_phci_child(pp->phys_path) == MDI_SUCCESS) {
                        rw_enter(&vhcache->vhcache_lock, RW_READER);

                        if ((cct = lookup_vhcache_client(vhcache, ct_name,
                            ct_addr, &tok)) == NULL) {
                                rw_exit(&vhcache->vhcache_lock);
                                goto out;
                        }

                        if (nonline_paths(cct) > 0 &&
                            pp->phys_path_next != NULL) {
                                rw_exit(&vhcache->vhcache_lock);
                                config_client_paths_async(vhc, ct_name, ct_addr,
                                    pp->phys_path_next, &tok);
                                pp->phys_path_next = NULL;
                                goto out;
                        }

                        rw_exit(&vhcache->vhcache_lock);
                }
        }

        adjust_sort_vhcache_paths(vhc, ct_name, ct_addr, &tok);
out:
        free_phclient_path_list(pp_head);
}

static void
single_threaded_vhconfig_enter(mdi_vhci_config_t *vhc)
{
        mutex_enter(&vhc->vhc_lock);
        while (vhc->vhc_flags & MDI_VHC_SINGLE_THREADED)
                cv_wait(&vhc->vhc_cv, &vhc->vhc_lock);
        vhc->vhc_flags |= MDI_VHC_SINGLE_THREADED;
        mutex_exit(&vhc->vhc_lock);
}

static void
single_threaded_vhconfig_exit(mdi_vhci_config_t *vhc)
{
        mutex_enter(&vhc->vhc_lock);
        vhc->vhc_flags &= ~MDI_VHC_SINGLE_THREADED;
        cv_broadcast(&vhc->vhc_cv);
        mutex_exit(&vhc->vhc_lock);
}

typedef struct mdi_phci_driver_info {
        char    *phdriver_name; /* name of the phci driver */

        /* set to non zero if the phci driver supports root device */
        int     phdriver_root_support;
} mdi_phci_driver_info_t;

/*
 * vhci class and root support capability of a phci driver can be
 * specified using ddi-vhci-class and ddi-no-root-support properties in the
 * phci driver.conf file. The built-in tables below contain this information
 * for those phci drivers whose driver.conf files don't yet contain this info.
 *
 * All phci drivers expect iscsi have root device support.
 */
static mdi_phci_driver_info_t scsi_phci_driver_list[] = {
        { "fp", 1 },
        { "iscsi", 0 },
        { "ibsrp", 1 }
        };

static mdi_phci_driver_info_t ib_phci_driver_list[] = { "tavor", 1 };

static void *
mdi_realloc(void *old_ptr, size_t old_size, size_t new_size)
{
        void *new_ptr;

        new_ptr = kmem_zalloc(new_size, KM_SLEEP);
        if (old_ptr) {
                bcopy(old_ptr, new_ptr, MIN(old_size, new_size));
                kmem_free(old_ptr, old_size);
        }
        return (new_ptr);
}

static void
add_to_phci_list(char ***driver_list, int **root_support_list,
    int *cur_elements, int *max_elements, char *driver_name, int root_support)
{
        ASSERT(*cur_elements <= *max_elements);
        if (*cur_elements == *max_elements) {
                *max_elements += 10;
                *driver_list = mdi_realloc(*driver_list,
                    sizeof (char *) * (*cur_elements),
                    sizeof (char *) * (*max_elements));
                *root_support_list = mdi_realloc(*root_support_list,
                    sizeof (int) * (*cur_elements),
                    sizeof (int) * (*max_elements));
        }
        (*driver_list)[*cur_elements] = i_ddi_strdup(driver_name, KM_SLEEP);
        (*root_support_list)[*cur_elements] = root_support;
        (*cur_elements)++;
}

static void
get_phci_driver_list(char *vhci_class, char ***driver_list,
    int **root_support_list, int *cur_elements, int *max_elements)
{
        mdi_phci_driver_info_t  *st_driver_list, *p;
        int             st_ndrivers, root_support, i, j, driver_conf_count;
        major_t         m;
        struct devnames *dnp;
        ddi_prop_t      *propp;

        *driver_list = NULL;
        *root_support_list = NULL;
        *cur_elements = 0;
        *max_elements = 0;

        /* add the phci drivers derived from the phci driver.conf files */
        for (m = 0; m < devcnt; m++) {
                dnp = &devnamesp[m];

                if (dnp->dn_flags & DN_PHCI_DRIVER) {
                        LOCK_DEV_OPS(&dnp->dn_lock);
                        if (dnp->dn_global_prop_ptr != NULL &&
                            (propp = i_ddi_prop_search(DDI_DEV_T_ANY,
                            DDI_VHCI_CLASS, DDI_PROP_TYPE_STRING,
                            &dnp->dn_global_prop_ptr->prop_list)) != NULL &&
                            strcmp(propp->prop_val, vhci_class) == 0) {

                                root_support = (i_ddi_prop_search(DDI_DEV_T_ANY,
                                    DDI_NO_ROOT_SUPPORT, DDI_PROP_TYPE_INT,
                                    &dnp->dn_global_prop_ptr->prop_list)
                                    == NULL) ? 1 : 0;

                                add_to_phci_list(driver_list, root_support_list,
                                    cur_elements, max_elements, dnp->dn_name,
                                    root_support);

                                UNLOCK_DEV_OPS(&dnp->dn_lock);
                        } else
                                UNLOCK_DEV_OPS(&dnp->dn_lock);
                }
        }

        driver_conf_count = *cur_elements;

        /* add the phci drivers specified in the built-in tables */
        if (strcmp(vhci_class, MDI_HCI_CLASS_SCSI) == 0) {
                st_driver_list = scsi_phci_driver_list;
                st_ndrivers = sizeof (scsi_phci_driver_list) /
                    sizeof (mdi_phci_driver_info_t);
        } else if (strcmp(vhci_class, MDI_HCI_CLASS_IB) == 0) {
                st_driver_list = ib_phci_driver_list;
                st_ndrivers = sizeof (ib_phci_driver_list) /
                    sizeof (mdi_phci_driver_info_t);
        } else {
                st_driver_list = NULL;
                st_ndrivers = 0;
        }

        for (i = 0, p = st_driver_list; i < st_ndrivers; i++, p++) {
                /* add this phci driver if not already added before */
                for (j = 0; j < driver_conf_count; j++) {
                        if (strcmp((*driver_list)[j], p->phdriver_name) == 0)
                                break;
                }
                if (j == driver_conf_count) {
                        add_to_phci_list(driver_list, root_support_list,
                            cur_elements, max_elements, p->phdriver_name,
                            p->phdriver_root_support);
                }
        }
}

/*
 * Attach the phci driver instances associated with the specified vhci class.
 * If root is mounted attach all phci driver instances.
 * If root is not mounted, attach the instances of only those phci
 * drivers that have the root support.
 */
static void
attach_phci_drivers(char *vhci_class)
{
        char    **driver_list, **p;
        int     *root_support_list;
        int     cur_elements, max_elements, i;
        major_t m;

        get_phci_driver_list(vhci_class, &driver_list, &root_support_list,
            &cur_elements, &max_elements);

        for (i = 0; i < cur_elements; i++) {
                if (modrootloaded || root_support_list[i]) {
                        m = ddi_name_to_major(driver_list[i]);
                        if (m != DDI_MAJOR_T_NONE &&
                            ddi_hold_installed_driver(m))
                                ddi_rele_driver(m);
                }
        }

        if (driver_list) {
                for (i = 0, p = driver_list; i < cur_elements; i++, p++)
                        kmem_free(*p, strlen(*p) + 1);
                kmem_free(driver_list, sizeof (char *) * max_elements);
                kmem_free(root_support_list, sizeof (int) * max_elements);
        }
}

/*
 * Build vhci cache:
 *
 * Attach phci driver instances and then drive BUS_CONFIG_ALL on
 * the phci driver instances. During this process the cache gets built.
 *
 * Cache is built fully if the root is mounted.
 * If the root is not mounted, phci drivers that do not have root support
 * are not attached. As a result the cache is built partially. The entries
 * in the cache reflect only those phci drivers that have root support.
 */
static int
build_vhci_cache(mdi_vhci_t *vh)
{
        mdi_vhci_config_t *vhc = vh->vh_config;
        mdi_vhci_cache_t *vhcache = &vhc->vhc_vhcache;

        single_threaded_vhconfig_enter(vhc);

        rw_enter(&vhcache->vhcache_lock, RW_READER);
        if (vhcache->vhcache_flags & MDI_VHCI_CACHE_SETUP_DONE) {
                rw_exit(&vhcache->vhcache_lock);
                single_threaded_vhconfig_exit(vhc);
                return (0);
        }
        rw_exit(&vhcache->vhcache_lock);

        attach_phci_drivers(vh->vh_class);
        bus_config_all_phcis(vhcache, NDI_DRV_CONF_REPROBE | NDI_NO_EVENT,
            BUS_CONFIG_ALL, DDI_MAJOR_T_NONE);

        rw_enter(&vhcache->vhcache_lock, RW_WRITER);
        vhcache->vhcache_flags |= MDI_VHCI_CACHE_SETUP_DONE;
        rw_exit(&vhcache->vhcache_lock);

        single_threaded_vhconfig_exit(vhc);
        vhcache_dirty(vhc);
        return (1);
}

/*
 * Determine if discovery of paths is needed.
 */
static int
vhcache_do_discovery(mdi_vhci_config_t *vhc)
{
        int rv = 1;

        mutex_enter(&vhc->vhc_lock);
        if (i_ddi_io_initialized() == 0) {
                if (vhc->vhc_path_discovery_boot > 0) {
                        vhc->vhc_path_discovery_boot--;
                        goto out;
                }
        } else {
                if (vhc->vhc_path_discovery_postboot > 0) {
                        vhc->vhc_path_discovery_postboot--;
                        goto out;
                }
        }

        /*
         * Do full path discovery at most once per mdi_path_discovery_interval.
         * This is to avoid a series of full path discoveries when opening
         * stale /dev/[r]dsk links.
         */
        if (mdi_path_discovery_interval != -1 &&
            ddi_get_lbolt64() >= vhc->vhc_path_discovery_cutoff_time)
                goto out;

        rv = 0;
out:
        mutex_exit(&vhc->vhc_lock);
        return (rv);
}

/*
 * Discover all paths:
 *
 * Attach phci driver instances and then drive BUS_CONFIG_ALL on all the phci
 * driver instances. During this process all paths will be discovered.
 */
static int
vhcache_discover_paths(mdi_vhci_t *vh)
{
        mdi_vhci_config_t *vhc = vh->vh_config;
        mdi_vhci_cache_t *vhcache = &vhc->vhc_vhcache;
        int rv = 0;

        single_threaded_vhconfig_enter(vhc);

        if (vhcache_do_discovery(vhc)) {
                attach_phci_drivers(vh->vh_class);
                bus_config_all_phcis(vhcache, NDI_DRV_CONF_REPROBE |
                    NDI_NO_EVENT, BUS_CONFIG_ALL, DDI_MAJOR_T_NONE);

                mutex_enter(&vhc->vhc_lock);
                vhc->vhc_path_discovery_cutoff_time = ddi_get_lbolt64() +
                    mdi_path_discovery_interval * TICKS_PER_SECOND;
                mutex_exit(&vhc->vhc_lock);
                rv = 1;
        }

        single_threaded_vhconfig_exit(vhc);
        return (rv);
}

/*
 * Generic vhci bus config implementation:
 *
 * Parameters
 *      vdip    vhci dip
 *      flags   bus config flags
 *      op      bus config operation
 *      The remaining parameters are bus config operation specific
 *
 * for BUS_CONFIG_ONE
 *      arg     pointer to name@addr
 *      child   upon successful return from this function, *child will be
 *              set to the configured and held devinfo child node of vdip.
 *      ct_addr pointer to client address (i.e. GUID)
 *
 * for BUS_CONFIG_DRIVER
 *      arg     major number of the driver
 *      child and ct_addr parameters are ignored
 *
 * for BUS_CONFIG_ALL
 *      arg, child, and ct_addr parameters are ignored
 *
 * Note that for the rest of the bus config operations, this function simply
 * calls the framework provided default bus config routine.
 */
int
mdi_vhci_bus_config(dev_info_t *vdip, uint_t flags, ddi_bus_config_op_t op,
    void *arg, dev_info_t **child, char *ct_addr)
{
        mdi_vhci_t *vh = i_devi_get_vhci(vdip);
        mdi_vhci_config_t *vhc = vh->vh_config;
        mdi_vhci_cache_t *vhcache = &vhc->vhc_vhcache;
        int rv = 0;
        int params_valid = 0;
        char *cp;

        /*
         * To bus config vhcis we relay operation, possibly using another
         * thread, to phcis. The phci driver then interacts with MDI to cause
         * vhci child nodes to be enumerated under the vhci node.  Adding a
         * vhci child requires an ndi_devi_enter of the vhci. Since another
         * thread may be adding the child, to avoid deadlock we can't wait
         * for the relayed operations to complete if we have already entered
         * the vhci node.
         */
        if (DEVI_BUSY_OWNED(vdip)) {
                MDI_DEBUG(2, (MDI_NOTE, vdip,
                    "vhci dip is busy owned %p", (void *)vdip));
                goto default_bus_config;
        }

        rw_enter(&vhcache->vhcache_lock, RW_READER);
        if (!(vhcache->vhcache_flags & MDI_VHCI_CACHE_SETUP_DONE)) {
                rw_exit(&vhcache->vhcache_lock);
                rv = build_vhci_cache(vh);
                rw_enter(&vhcache->vhcache_lock, RW_READER);
        }

        switch (op) {
        case BUS_CONFIG_ONE:
                if (arg != NULL && ct_addr != NULL) {
                        /* extract node name */
                        cp = (char *)arg;
                        while (*cp != '\0' && *cp != '@')
                                cp++;
                        if (*cp == '@') {
                                params_valid = 1;
                                *cp = '\0';
                                config_client_paths(vhc, (char *)arg, ct_addr);
                                /* config_client_paths() releases cache_lock */
                                *cp = '@';
                                break;
                        }
                }

                rw_exit(&vhcache->vhcache_lock);
                break;

        case BUS_CONFIG_DRIVER:
                rw_exit(&vhcache->vhcache_lock);
                if (rv == 0)
                        st_bus_config_all_phcis(vhc, flags, op,
                            (major_t)(uintptr_t)arg);
                break;

        case BUS_CONFIG_ALL:
                rw_exit(&vhcache->vhcache_lock);
                if (rv == 0)
                        st_bus_config_all_phcis(vhc, flags, op, -1);
                break;

        default:
                rw_exit(&vhcache->vhcache_lock);
                break;
        }


default_bus_config:
        /*
         * All requested child nodes are enumerated under the vhci.
         * Now configure them.
         */
        if (ndi_busop_bus_config(vdip, flags, op, arg, child, 0) ==
            NDI_SUCCESS) {
                return (MDI_SUCCESS);
        } else if (op == BUS_CONFIG_ONE && rv == 0 && params_valid) {
                /* discover all paths and try configuring again */
                if (vhcache_discover_paths(vh) &&
                    ndi_busop_bus_config(vdip, flags, op, arg, child, 0) ==
                    NDI_SUCCESS)
                        return (MDI_SUCCESS);
        }

        return (MDI_FAILURE);
}

/*
 * Read the on-disk vhci cache into an nvlist for the specified vhci class.
 */
static nvlist_t *
read_on_disk_vhci_cache(char *vhci_class)
{
        nvlist_t *nvl;
        int err;
        char *filename;

        filename = vhclass2vhcache_filename(vhci_class);

        if ((err = fread_nvlist(filename, &nvl)) == 0) {
                kmem_free(filename, strlen(filename) + 1);
                return (nvl);
        } else if (err == EIO)
                cmn_err(CE_WARN, "%s: I/O error, will recreate", filename);
        else if (err == EINVAL)
                cmn_err(CE_WARN,
                    "%s: data file corrupted, will recreate", filename);

        kmem_free(filename, strlen(filename) + 1);
        return (NULL);
}

/*
 * Read on-disk vhci cache into nvlists for all vhci classes.
 * Called during booting by i_ddi_read_devices_files().
 */
void
mdi_read_devices_files(void)
{
        int i;

        for (i = 0; i < N_VHCI_CLASSES; i++)
                vhcache_nvl[i] = read_on_disk_vhci_cache(vhci_class_list[i]);
}

/*
 * Remove all stale entries from vhci cache.
 */
static void
clean_vhcache(mdi_vhci_config_t *vhc)
{
        mdi_vhci_cache_t        *vhcache = &vhc->vhc_vhcache;
        mdi_vhcache_phci_t      *phci, *nxt_phci;
        mdi_vhcache_client_t    *client, *nxt_client;
        mdi_vhcache_pathinfo_t  *path, *nxt_path;

        rw_enter(&vhcache->vhcache_lock, RW_WRITER);

        client = vhcache->vhcache_client_head;
        vhcache->vhcache_client_head = vhcache->vhcache_client_tail = NULL;
        for ( ; client != NULL; client = nxt_client) {
                nxt_client = client->cct_next;

                path = client->cct_cpi_head;
                client->cct_cpi_head = client->cct_cpi_tail = NULL;
                for ( ; path != NULL; path = nxt_path) {
                        nxt_path = path->cpi_next;
                        if ((path->cpi_cphci->cphci_phci != NULL) &&
                            (path->cpi_pip != NULL)) {
                                enqueue_tail_vhcache_pathinfo(client, path);
                        } else if (path->cpi_pip != NULL) {
                                /* Not valid to have a path without a phci. */
                                free_vhcache_pathinfo(path);
                        }
                }

                if (client->cct_cpi_head != NULL)
                        enqueue_vhcache_client(vhcache, client);
                else {
                        (void) mod_hash_destroy(vhcache->vhcache_client_hash,
                            (mod_hash_key_t)client->cct_name_addr);
                        free_vhcache_client(client);
                }
        }

        phci = vhcache->vhcache_phci_head;
        vhcache->vhcache_phci_head = vhcache->vhcache_phci_tail = NULL;
        for ( ; phci != NULL; phci = nxt_phci) {

                nxt_phci = phci->cphci_next;
                if (phci->cphci_phci != NULL)
                        enqueue_vhcache_phci(vhcache, phci);
                else
                        free_vhcache_phci(phci);
        }

        vhcache->vhcache_clean_time = ddi_get_lbolt64();
        rw_exit(&vhcache->vhcache_lock);
        vhcache_dirty(vhc);
}

/*
 * Remove all stale entries from vhci cache.
 * Called by i_ddi_clean_devices_files() during the execution of devfsadm -C
 */
void
mdi_clean_vhcache(void)
{
        mdi_vhci_t *vh;

        mutex_enter(&mdi_mutex);
        for (vh = mdi_vhci_head; vh != NULL; vh = vh->vh_next) {
                vh->vh_refcnt++;
                mutex_exit(&mdi_mutex);
                clean_vhcache(vh->vh_config);
                mutex_enter(&mdi_mutex);
                vh->vh_refcnt--;
        }
        mutex_exit(&mdi_mutex);
}

/*
 * mdi_vhci_walk_clients():
 *              Walker routine to traverse client dev_info nodes
 * ddi_walk_devs(ddi_get_child(vdip), f, arg) returns the entire tree
 * below the client, including nexus devices, which we dont want.
 * So we just traverse the immediate siblings, starting from 1st client.
 */
void
mdi_vhci_walk_clients(dev_info_t *vdip,
    int (*f)(dev_info_t *, void *), void *arg)
{
        mdi_vhci_t      *vh = i_devi_get_vhci(vdip);
        dev_info_t      *cdip;
        mdi_client_t    *ct;

        MDI_VHCI_CLIENT_LOCK(vh);
        cdip = ddi_get_child(vdip);
        while (cdip) {
                ct = i_devi_get_client(cdip);
                MDI_CLIENT_LOCK(ct);

                if (((*f)(cdip, arg)) == DDI_WALK_CONTINUE)
                        cdip = ddi_get_next_sibling(cdip);
                else
                        cdip = NULL;

                MDI_CLIENT_UNLOCK(ct);
        }
        MDI_VHCI_CLIENT_UNLOCK(vh);
}

/*
 * mdi_vhci_walk_phcis():
 *              Walker routine to traverse phci dev_info nodes
 */
void
mdi_vhci_walk_phcis(dev_info_t *vdip,
    int (*f)(dev_info_t *, void *), void *arg)
{
        mdi_vhci_t      *vh = i_devi_get_vhci(vdip);
        mdi_phci_t      *ph, *next;

        MDI_VHCI_PHCI_LOCK(vh);
        ph = vh->vh_phci_head;
        while (ph) {
                MDI_PHCI_LOCK(ph);

                if (((*f)(ph->ph_dip, arg)) == DDI_WALK_CONTINUE)
                        next = ph->ph_next;
                else
                        next = NULL;

                MDI_PHCI_UNLOCK(ph);
                ph = next;
        }
        MDI_VHCI_PHCI_UNLOCK(vh);
}


/*
 * mdi_walk_vhcis():
 *              Walker routine to traverse vhci dev_info nodes
 */
void
mdi_walk_vhcis(int (*f)(dev_info_t *, void *), void *arg)
{
        mdi_vhci_t      *vh = NULL;

        mutex_enter(&mdi_mutex);
        /*
         * Scan for already registered vhci
         */
        for (vh = mdi_vhci_head; vh != NULL; vh = vh->vh_next) {
                vh->vh_refcnt++;
                mutex_exit(&mdi_mutex);
                if (((*f)(vh->vh_dip, arg)) != DDI_WALK_CONTINUE) {
                        mutex_enter(&mdi_mutex);
                        vh->vh_refcnt--;
                        break;
                } else {
                        mutex_enter(&mdi_mutex);
                        vh->vh_refcnt--;
                }
        }

        mutex_exit(&mdi_mutex);
}

/*
 * i_mdi_log_sysevent():
 *              Logs events for pickup by syseventd
 */
static void
i_mdi_log_sysevent(dev_info_t *dip, char *ph_vh_class, char *subclass)
{
        char            *path_name;
        nvlist_t        *attr_list;

        if (nvlist_alloc(&attr_list, NV_UNIQUE_NAME_TYPE,
            KM_SLEEP) != DDI_SUCCESS) {
                goto alloc_failed;
        }

        path_name = kmem_zalloc(MAXPATHLEN, KM_SLEEP);
        (void) ddi_pathname(dip, path_name);

        if (nvlist_add_string(attr_list, DDI_DRIVER_NAME,
            ddi_driver_name(dip)) != DDI_SUCCESS) {
                goto error;
        }

        if (nvlist_add_int32(attr_list, DDI_DRIVER_MAJOR,
            (int32_t)ddi_driver_major(dip)) != DDI_SUCCESS) {
                goto error;
        }

        if (nvlist_add_int32(attr_list, DDI_INSTANCE,
            (int32_t)ddi_get_instance(dip)) != DDI_SUCCESS) {
                goto error;
        }

        if (nvlist_add_string(attr_list, DDI_PATHNAME,
            path_name) != DDI_SUCCESS) {
                goto error;
        }

        if (nvlist_add_string(attr_list, DDI_CLASS,
            ph_vh_class) != DDI_SUCCESS) {
                goto error;
        }

        (void) ddi_log_sysevent(dip, DDI_VENDOR_SUNW, EC_DDI, subclass,
            attr_list, NULL, DDI_SLEEP);

error:
        kmem_free(path_name, MAXPATHLEN);
        nvlist_free(attr_list);
        return;

alloc_failed:
        MDI_DEBUG(1, (MDI_WARN, dip, "!unable to send sysevent"));
}

char **
mdi_get_phci_driver_list(char *vhci_class, int  *ndrivers)
{
        char    **driver_list, **ret_driver_list = NULL;
        int     *root_support_list;
        int     cur_elements, max_elements;

        get_phci_driver_list(vhci_class, &driver_list, &root_support_list,
            &cur_elements, &max_elements);


        if (driver_list) {
                kmem_free(root_support_list, sizeof (int) * max_elements);
                ret_driver_list = mdi_realloc(driver_list, sizeof (char *)
                    * max_elements, sizeof (char *) * cur_elements);
        }
        *ndrivers = cur_elements;

        return (ret_driver_list);

}

void
mdi_free_phci_driver_list(char **driver_list, int ndrivers)
{
        char    **p;
        int     i;

        if (driver_list) {
                for (i = 0, p = driver_list; i < ndrivers; i++, p++)
                        kmem_free(*p, strlen(*p) + 1);
                kmem_free(driver_list, sizeof (char *) * ndrivers);
        }
}

/*
 * mdi_is_dev_supported():
 *              function called by pHCI bus config operation to determine if a
 *              device should be represented as a child of the vHCI or the
 *              pHCI.  This decision is made by the vHCI, using cinfo idenity
 *              information passed by the pHCI - specifics of the cinfo
 *              representation are by agreement between the pHCI and vHCI.
 * Return Values:
 *              MDI_SUCCESS
 *              MDI_FAILURE
 */
int
mdi_is_dev_supported(char *class, dev_info_t *pdip, void *cinfo)
{
        mdi_vhci_t      *vh;

        ASSERT(class && pdip);

        /*
         * For dev_supported, mdi_phci_register() must have established pdip as
         * a pHCI.
         *
         * NOTE: mdi_phci_register() does "mpxio-disable" processing, and
         * MDI_PHCI(pdip) will return false if mpxio is disabled.
         */
        if (!MDI_PHCI(pdip))
                return (MDI_FAILURE);

        /* Return MDI_FAILURE if vHCI does not support asking the question. */
        vh = (mdi_vhci_t *)i_mdi_vhci_class2vhci(class);
        if ((vh == NULL) || (vh->vh_ops->vo_is_dev_supported == NULL)) {
                return (MDI_FAILURE);
        }

        /* Return vHCI answer */
        return (vh->vh_ops->vo_is_dev_supported(vh->vh_dip, pdip, cinfo));
}

int
mdi_dc_return_dev_state(mdi_pathinfo_t *pip, struct devctl_iocdata *dcp)
{
        uint_t devstate = 0;
        dev_info_t *cdip;

        if ((pip == NULL) || (dcp == NULL))
                return (MDI_FAILURE);

        cdip = mdi_pi_get_client(pip);

        switch (mdi_pi_get_state(pip)) {
        case MDI_PATHINFO_STATE_INIT:
                devstate = DEVICE_DOWN;
                break;
        case MDI_PATHINFO_STATE_ONLINE:
                devstate = DEVICE_ONLINE;
                if ((cdip) && (devi_stillreferenced(cdip) == DEVI_REFERENCED))
                        devstate |= DEVICE_BUSY;
                break;
        case MDI_PATHINFO_STATE_STANDBY:
                devstate = DEVICE_ONLINE;
                break;
        case MDI_PATHINFO_STATE_FAULT:
                devstate = DEVICE_DOWN;
                break;
        case MDI_PATHINFO_STATE_OFFLINE:
                devstate = DEVICE_OFFLINE;
                break;
        default:
                ASSERT(MDI_PI(pip)->pi_state);
        }

        if (copyout(&devstate, dcp->cpyout_buf, sizeof (uint_t)) != 0)
                return (MDI_FAILURE);

        return (MDI_SUCCESS);
}