include: gcc 7's cpp has problems with the line continuations in .x files

[unleashed.git] / kernel / os / instance.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) 1992, 2010, Oracle and/or its affiliates. All rights reserved.
 */

/*
 * Instance number assignment code
 */

#include <sys/types.h>
#include <sys/param.h>
#include <sys/errno.h>
#include <sys/systm.h>
#include <sys/kobj.h>
#include <sys/t_lock.h>
#include <sys/kmem.h>
#include <sys/cmn_err.h>
#include <sys/ddi.h>
#include <sys/sunddi.h>
#include <sys/autoconf.h>
#include <sys/systeminfo.h>
#include <sys/hwconf.h>
#include <sys/reboot.h>
#include <sys/ddi_impldefs.h>
#include <sys/instance.h>
#include <sys/debug.h>
#include <sys/sysevent.h>
#include <sys/modctl.h>
#include <sys/console.h>
#include <sys/sysmacros.h>
#include <sys/crc32.h>


static void in_preassign_instance(void);
static void i_log_devfs_instance_mod(void);
static int in_get_infile(char *);
static void in_removenode(struct devnames *dnp, in_node_t *mp, in_node_t *ap);
static in_node_t *in_alloc_node(char *name, char *addr);
static int in_eqstr(char *a, char *b);
static char *in_name_addr(char **cpp, char **addrp);
static in_node_t *in_devwalk(dev_info_t *dip, in_node_t **ap, char *addr);
static void in_dealloc_node(in_node_t *np);
static in_node_t *in_make_path(char *path);
static void in_enlist(in_node_t *ap, in_node_t *np);
static int in_inuse(int instance, char *name);
static void in_hashdrv(in_drv_t *dp);
static in_drv_t *in_drvwalk(in_node_t *np, char *binding_name);
static in_drv_t *in_alloc_drv(char *bindingname);
static void in_endrv(in_node_t *np, in_drv_t *dp);
static void in_dq_drv(in_drv_t *np);
static void in_removedrv(struct devnames *dnp, in_drv_t *mp);
static int in_pathin(char *cp, int instance, char *bname, struct bind **args);
static int in_next_instance_block(major_t, int);
static int in_next_instance(major_t);

#pragma weak plat_ioaliases_init


/* external functions */
extern char *i_binding_to_drv_name(char *bname);
extern void plat_ioaliases_init(void);

/*
 * This plus devnames defines the entire software state of the instance world.
 */
typedef struct in_softstate {
        in_node_t       *ins_root;      /* the root of our instance tree */
        in_drv_t        *ins_no_major;  /* majorless drv entries */
        /*
         * Used to serialize access to data structures
         */
        void            *ins_thread;
        kmutex_t        ins_serial;
        kcondvar_t      ins_serial_cv;
        int             ins_busy;
        boolean_t       ins_dirty;      /* instance info needs flush */
} in_softstate_t;

static in_softstate_t e_ddi_inst_state;

/*
 * State transition information:
 * e_ddi_inst_state contains, among other things, the root of a tree of
 * device nodes used to track instance number assignments.
 * Each device node may contain multiple driver bindings, represented
 * by a linked list of in_drv_t nodes, each with an instance assignment
 * (except for root node). Each in_drv node can be in one of 3 states,
 * indicated by ind_state:
 *
 * IN_UNKNOWN:  Each node created in this state.  The instance number of
 *      this node is not known.  ind_instance is set to -1.
 * IN_PROVISIONAL:  When a node is assigned an instance number in
 *      e_ddi_assign_instance(), its state is set to IN_PROVISIONAL.
 *      Subsequently, the framework will always call either
 *      e_ddi_keep_instance() which makes the node IN_PERMANENT
 *      or e_ddi_free_instance(), which deletes the node.
 * IN_PERMANENT:
 *      If e_ddi_keep_instance() is called on an IN_PROVISIONAL node,
 *      its state is set to IN_PERMANENT.
 */

static char *instance_file = INSTANCE_FILE;
static char *instance_file_backup = INSTANCE_FILE INSTANCE_FILE_SUFFIX;

/*
 * Return values for in_get_infile().
 */
#define PTI_FOUND       0
#define PTI_NOT_FOUND   1
#define PTI_REBUILD     2

int     instance_searchme = 0;  /* testing: use complex code path */

/*
 * Path to instance file magic string used for first time boot after
 * an install.  If this is the first string in the file we will
 * automatically rebuild the file.
 */
#define PTI_MAGIC_STR           "#path_to_inst_bootstrap_1"
#define PTI_MAGIC_STR_LEN       (sizeof (PTI_MAGIC_STR) - 1)

void
e_ddi_instance_init(void)
{
        char *file;
        int rebuild = 1;
        struct in_drv *dp;

        mutex_init(&e_ddi_inst_state.ins_serial, NULL, MUTEX_DEFAULT, NULL);
        cv_init(&e_ddi_inst_state.ins_serial_cv, NULL, CV_DEFAULT, NULL);

        /*
         * Only one thread is allowed to change the state of the instance
         * number assignments on the system at any given time.
         * Note that this is not really necessary, as we are single-threaded
         * here, but it won't hurt, and it allows us to keep ASSERTS for
         * our assumptions in the code.
         */
        e_ddi_enter_instance();

        /*
         * Init the ioaliases if the platform supports it
         */
        if (&plat_ioaliases_init)
                plat_ioaliases_init();

        /*
         * Create the root node, instance zallocs to 0.
         * The name and address of this node never get examined, we always
         * start searching with its first child.
         */
        ASSERT(e_ddi_inst_state.ins_root == NULL);
        e_ddi_inst_state.ins_root = in_alloc_node(NULL, NULL);
        dp = in_alloc_drv("rootnex");
        in_endrv(e_ddi_inst_state.ins_root, dp);

        file = instance_file;
        switch (in_get_infile(file)) {
        default:
        case PTI_NOT_FOUND:
                /* make sure path_to_inst is recreated */
                boothowto |= RB_RECONFIG;

                /*
                 * Something is wrong. First try the backup file.
                 * If not found, rebuild path_to_inst. Emit a
                 * message about the problem.
                 */
                cmn_err(CE_WARN, "%s empty or not found", file);

                file = instance_file_backup;
                if (in_get_infile(file) != PTI_FOUND) {
                        cmn_err(CE_NOTE, "rebuilding device instance data");
                        break;
                }
                cmn_err(CE_NOTE, "using backup instance data in %s", file);
                /*FALLTHROUGH*/

        case PTI_FOUND:
                /*
                 * We've got a readable file
                 * parse the file into the instance tree
                 */
                (void) read_binding_file(file, NULL, in_pathin);
                rebuild = 0;
                break;

        case PTI_REBUILD:
                /*
                 * path_to_inst has magic str requesting a create
                 * Convert boot to reconfig boot to ensure /dev is
                 * in sync with new path_to_inst.
                 */
                boothowto |= RB_RECONFIG;
                cmn_err(CE_CONT,
                    "?Using default device instance data\n");
                break;
        }

        /*
         * The OBP device tree has been copied to the kernel and
         * bound to drivers at this point. We walk the per-driver
         * list to preassign instances. Since the bus addr is
         * unknown at this point, we cannot place the instance
         * number in the instance tree. This will be done at
         * a later time.
         */
        if (rebuild)
                in_preassign_instance();

        e_ddi_exit_instance();
}

static void
in_preassign_instance()
{
        major_t         m;
        struct devnames *dnp;
        dev_info_t      *dip;
        extern major_t  devcnt;

        for (m = 0; m < devcnt; m++) {
                dnp = &devnamesp[m];
                dip = dnp->dn_head;
                while (dip) {
                        DEVI(dip)->devi_instance = dnp->dn_instance;
                        dnp->dn_instance++;
                        dip = ddi_get_next(dip);
                }

                /*
                 * The preassign instance numbers are not fully
                 * accounted for until e_ddi_assign_instance().
                 * We can't fully account for them now because we
                 * don't currently have a unit-address. Because of
                 * this, we need to remember the preassign boundary
                 * to avoid ordering issues related to
                 * e_ddi_assign_instance of a preassigned value .vs.
                 * re-assignment of the same value for a dynamic
                 * SID node created by bus_config.
                 */
                dnp->dn_pinstance = dnp->dn_instance;
                dnp->dn_instance = IN_SEARCHME;
        }
}

/*
 * Checks to see if the /etc/path_to_inst file exists and whether or not
 * it has the magic string in it.
 *
 * Returns one of the following:
 *
 *      PTI_FOUND       - We have found the /etc/path_to_inst file
 *      PTI_REBUILD     - We have found the /etc/path_to_inst file and the
 *                        first line was PTI_MAGIC_STR.
 *      PTI_NOT_FOUND   - We did not find the /etc/path_to_inst file
 *
 */
static int
in_get_infile(char *filename)
{
        struct _buf *file;
        int return_val;
        char buf[PTI_MAGIC_STR_LEN];

        /*
         * Try to open the file.
         */
        if ((file = kobj_open_file(filename)) == (struct _buf *)-1) {
                return (PTI_NOT_FOUND);
        }
        return_val = PTI_FOUND;

        /*
         * Read the first PTI_MAGIC_STR_LEN bytes from the file to see if
         * it contains the magic string.  If there aren't that many bytes
         * in the file, then assume file is correct and no magic string
         * and move on.
         */
        switch (kobj_read_file(file, buf, PTI_MAGIC_STR_LEN, 0)) {

        case PTI_MAGIC_STR_LEN:
                /*
                 * If the first PTI_MAGIC_STR_LEN bytes are the magic string
                 * then return PTI_REBUILD.
                 */
                if (strncmp(PTI_MAGIC_STR, buf, PTI_MAGIC_STR_LEN) == 0)
                        return_val = PTI_REBUILD;
                break;

        case 0:
                /*
                 * If the file is zero bytes in length, then consider the
                 * file to not be found
                 */
                return_val = PTI_NOT_FOUND;

        default: /* Do nothing we have a good file */
                break;
        }

        kobj_close_file(file);
        return (return_val);
}

int
is_pseudo_device(dev_info_t *dip)
{
        dev_info_t      *pdip;

        for (pdip = ddi_get_parent(dip); pdip && pdip != ddi_root_node();
            pdip = ddi_get_parent(pdip)) {
                if (strcmp(ddi_get_name(pdip), DEVI_PSEUDO_NEXNAME) == 0)
                        return (1);
        }
        return (0);
}


static void
in_set_instance(dev_info_t *dip, in_drv_t *dp, major_t major)
{
        /* use preassigned instance if available */
        if (DEVI(dip)->devi_instance != -1)
                dp->ind_instance = DEVI(dip)->devi_instance;
        else
                dp->ind_instance = in_next_instance(major);
}

/*
 * Return 1 if instance block was assigned for the path.
 *
 * For multi-port NIC cards, sequential instance assignment across all
 * ports on a card is highly desirable since the ppa is typically the
 * same as the instance number, and the ppa is used in the NIC's public
 * /dev name. This sequential assignment typically occurs as a result
 * of in_preassign_instance() after initial install, or by
 * i_ndi_init_hw_children() for NIC ports that share a common parent.
 *
 * Some NIC cards however use multi-function bridge chips, and to
 * support sequential instance assignment accross all ports, without
 * disabling multi-threaded attach, we have a (currently) undocumented
 * hack to allocate instance numbers in contiguous blocks based on
 * driver.conf properties.
 *
 *                       ^
 *           /----------   ------------\
 *        pci@0                      pci@0,1    MULTI-FUNCTION BRIDGE CHIP
 *       /     \                    /       \
 * FJSV,e4ta@4  FJSV,e4ta@4,1   FJSV,e4ta@6 FJSV,e4ta@6,1       NIC PORTS
 *      n            n+2             n+2         n+3            INSTANCE
 *
 * For the above example, the following driver.conf properties would be
 * used to guarantee sequential instance number assignment.
 *
 * ddi-instance-blocks ="ib-FJSVe4ca", "ib-FJSVe4ta", "ib-generic";
 * ib-FJSVe4ca =        "/pci@0/FJSV,e4ca@4", "/pci@0/FJSV,e4ca@4,1",
 *                      "/pci@0,1/FJSV,e4ca@6", "/pci@0,1/FJSV,e4ca@6,1";
 * ib-FJSVe4ta =        "/pci@0/FJSV,e4ta@4", "/pci@0/FJSV,e4ta@4,1",
 *                      "/pci@0,1/FJSV,e4ta@6", "/pci@0,1/FJSV,e4ta@6,1";
 * ib-generic =         "/pci@0/network@4", "/pci@0/network@4,1",
 *                      "/pci@0,1/network@6", "/pci@0,1/network@6,1";
 *
 * The value of the 'ddi-instance-blocks' property references a series
 * of card specific properties, like 'ib-FJSV-e4ta', who's value
 * defines a single 'instance block'.  The 'instance block' describes
 * all the paths below a multi-function bridge, where each path is
 * called an 'instance path'.  The 'instance block' property value is a
 * series of 'instance paths'.  The number of 'instance paths' in an
 * 'instance block' defines the size of the instance block, and the
 * ordering of the 'instance paths' defines the instance number
 * assignment order for paths going through the 'instance block'.
 *
 * In the instance assignment code below, if a (path, driver) that
 * currently has no instance number has a path that goes through an
 * 'instance block', then block instance number allocation occurs.  The
 * block allocation code will find a sequential set of unused instance
 * numbers, and assign instance numbers for all the paths in the
 * 'instance block'.  Each path is assigned a persistent instance
 * number, even paths that don't exist in the device tree or fail
 * probe(9E).
 */
static int
in_assign_instance_block(dev_info_t *dip)
{
        char            **ibn;          /* instance block names */
        uint_t          nibn;           /* number of instance block names */
        uint_t          ibni;           /* ibn index */
        char            *driver;
        major_t         major;
        char            *path;
        char            *addr;
        int             plen;
        char            **ibp;          /* instance block paths */
        uint_t          nibp;           /* number of paths in instance block */
        uint_t          ibpi;           /* ibp index */
        int             ibplen;         /* length of instance block path */
        char            *ipath;
        int             instance_base;
        int             splice;
        int             i;

        /* check for fresh install case (in miniroot) */
        if (DEVI(dip)->devi_instance != -1)
                return (0);                     /* already assigned */

        /*
         * Check to see if we need to allocate a block of contiguous instance
         * numbers by looking for the 'ddi-instance-blocks' property.
         */
        if (ddi_prop_lookup_string_array(DDI_DEV_T_ANY, dip, DDI_PROP_DONTPASS,
            "ddi-instance-blocks", &ibn, &nibn) != DDI_SUCCESS)
                return (0);                     /* no instance block needed */

        /*
         * Get information out about node we are processing.
         *
         * NOTE: Since the node is not yet at DS_INITIALIZED, ddi_pathname()
         * will not return the unit-address of the final path component even
         * though the node has an established devi_addr unit-address - so we
         * need to add the unit-address by hand.
         */
        driver = (char *)ddi_driver_name(dip);
        major = ddi_driver_major(dip);
        path = kmem_alloc(MAXPATHLEN, KM_SLEEP);
        (void) ddi_pathname(dip, path);
        if ((addr =  ddi_get_name_addr(dip)) != NULL) {
                (void) strcat(path, "@");
                (void) strcat(path, addr);
        }
        plen = strlen(path);

        /* loop through instance block names */
        for (ibni = 0; ibni < nibn; ibni++) {
                if (ibn[ibni] == NULL)
                        continue;

                /* lookup instance block */
                if (ddi_prop_lookup_string_array(DDI_DEV_T_ANY, dip,
                    DDI_PROP_DONTPASS, ibn[ibni],
                    &ibp, &nibp) != DDI_SUCCESS) {
                        cmn_err(CE_WARN,
                            "no devinition for instance block '%s' in %s.conf",
                            ibn[ibni], driver);
                        continue;
                }

                /* Does 'path' go through this instance block? */
                for (ibpi = 0; ibpi < nibp; ibpi++) {
                        if (ibp[ibpi] == NULL)
                                continue;
                        ibplen = strlen(ibp[ibpi]);
                        if ((ibplen <= plen) &&
                            (strcmp(ibp[ibpi], path + plen - ibplen) == 0))
                                break;

                }
                if (ibpi >= nibp) {
                        ddi_prop_free(ibp);
                        continue;               /* no try next instance block */
                }

                /* yes, allocate and assign instances for all paths in block */

                /*
                 * determine where we splice in instance paths and verify
                 * that none of the paths are too long.
                 */
                splice = plen - ibplen;
                for (i = 0; i < nibp; i++) {
                        if ((splice + strlen(ibp[i])+ 1) >= MAXPATHLEN) {
                                cmn_err(CE_WARN,
                                    "path %d through instance block '%s' from "
                                    "%s.conf too long", i, ibn[ibni], driver);
                                break;
                        }
                }
                if (i < nibp) {
                        ddi_prop_free(ibp);
                        continue;               /* too long */
                }

                /* allocate the instance block - no more failures */
                instance_base = in_next_instance_block(major, nibp);

                ipath = kmem_alloc(MAXPATHLEN, KM_SLEEP);
                for (ibpi = 0; ibpi < nibp; ibpi++) {
                        if (ibp[ibpi] == NULL)
                                continue;
                        (void) strcpy(ipath, path);
                        (void) strcpy(ipath + splice, ibp[ibpi]);
                        (void) in_pathin(ipath,
                            instance_base + ibpi, driver, NULL);
                }

                /* free allocations */
                kmem_free(ipath, MAXPATHLEN);
                ddi_prop_free(ibp);
                kmem_free(path, MAXPATHLEN);
                ddi_prop_free(ibn);

                /* notify devfsadmd to sync of path_to_inst file */
                mutex_enter(&e_ddi_inst_state.ins_serial);
                i_log_devfs_instance_mod();
                e_ddi_inst_state.ins_dirty = B_TRUE;
                mutex_exit(&e_ddi_inst_state.ins_serial);
                return (1);
        }

        /* our path did not go through any of of the instance blocks */
        kmem_free(path, MAXPATHLEN);
        ddi_prop_free(ibn);
        return (0);
}

/*
 * Look up an instance number for a dev_info node, and assign one if it does
 * not have one (the dev_info node has devi_name and devi_addr already set).
 */
uint_t
e_ddi_assign_instance(dev_info_t *dip)
{
        char *name;
        in_node_t *ap, *np;
        in_drv_t *dp;
        major_t major;
        uint_t ret;
        char *bname;

        /*
         * Allow implementation to override
         */
        if ((ret = impl_assign_instance(dip)) != (uint_t)-1)
                return (ret);

        /*
         * If this is a pseudo-device, use the instance number
         * assigned by the pseudo nexus driver. The mutex is
         * not needed since the instance tree is not used.
         */
        if (is_pseudo_device(dip)) {
                return (ddi_get_instance(dip));
        }

        /*
         * Only one thread is allowed to change the state of the instance
         * number assignments on the system at any given time.
         */
        e_ddi_enter_instance();

        /*
         * Look for instance node, allocate one if not found
         */
        np = in_devwalk(dip, &ap, NULL);
        if (np == NULL) {
                if (in_assign_instance_block(dip)) {
                        np = in_devwalk(dip, &ap, NULL);
                } else {
                        name = ddi_node_name(dip);
                        np = in_alloc_node(name, ddi_get_name_addr(dip));
                        ASSERT(np != NULL);
                        in_enlist(ap, np);      /* insert into tree */
                }
        }
        ASSERT(np == in_devwalk(dip, &ap, NULL));

        /*
         * Link the devinfo node and in_node_t
         */
        if (DEVI(dip)->devi_in_node || np->in_devi) {
                ddi_err(DER_MODE, dip, "devinfo and  instance node (%p) "
                    "interlink fields are not NULL", (void *)np);
        }
        DEVI(dip)->devi_in_node = np;
        np->in_devi = dip;

        /*
         * Look for driver entry, allocate one if not found
         */
        bname = (char *)ddi_driver_name(dip);
        dp = in_drvwalk(np, bname);
        if (dp == NULL) {

                if (ddi_aliases_present == B_TRUE) {
                        e_ddi_borrow_instance(dip, np);
                }

                if ((dp = in_drvwalk(np, bname)) == NULL) {
                        dp = in_alloc_drv(bname);
                        ASSERT(dp != NULL);
                        major = ddi_driver_major(dip);
                        ASSERT(major != DDI_MAJOR_T_NONE);
                        in_endrv(np, dp);
                        in_set_instance(dip, dp, major);
                        dp->ind_state = IN_PROVISIONAL;
                        in_hashdrv(dp);
                } else {
                        dp->ind_state = IN_BORROWED;
                }
        }

        ret = dp->ind_instance;

        e_ddi_exit_instance();
        return (ret);
}

static int
mkpathname(char *path, in_node_t *np, int len)
{
        int len_needed;

        if (np == e_ddi_inst_state.ins_root)
                return (DDI_SUCCESS);

        if (mkpathname(path, np->in_parent, len) == DDI_FAILURE)
                return (DDI_FAILURE);

        len_needed = strlen(path);
        len_needed += strlen(np->in_node_name) + 1;     /* for '/' */
        if (np->in_unit_addr) {
                len_needed += strlen(np->in_unit_addr) + 1;  /* for '@' */
        }
        len_needed += 1; /* for '\0' */

        /*
         * XX complain
         */
        if (len_needed > len)
                return (DDI_FAILURE);

        if (np->in_unit_addr[0] == '\0')
                (void) sprintf(path+strlen(path), "/%s", np->in_node_name);
        else
                (void) sprintf(path+strlen(path), "/%s@%s", np->in_node_name,
                    np->in_unit_addr);

        return (DDI_SUCCESS);
}

/*
 * produce the path to the given instance of a major number.
 * path must hold MAXPATHLEN string
 */
int
e_ddi_instance_majorinstance_to_path(major_t major, uint_t inst, char *path)
{
        struct devnames *dnp;
        in_drv_t        *dp;
        int             ret;

        e_ddi_enter_instance();

        /* look for the instance threaded off major */
        dnp = &devnamesp[major];
        for (dp = dnp->dn_inlist; dp != NULL; dp = dp->ind_next)
                if (dp->ind_instance == inst)
                        break;

        /* produce path from the node that uses the instance */
        if (dp) {
                *path = 0;
                ret = mkpathname(path, dp->ind_node, MAXPATHLEN);
        } else
                ret = DDI_FAILURE;

        e_ddi_exit_instance();
        return (ret);
}

/*
 * Allocate a sequential block of instance numbers for the specified driver,
 * and return the base instance number of the block.  The implementation
 * depends on the list being sorted in ascending instance number sequence.
 * When there are no 'holes' in the allocation sequence, dn_instance is the
 * next available instance number. When dn_instance is IN_SEARCHME, hole(s)
 * exists and a slower code path executes which tries to fill holes.
 *
 * The block returned can't be in the preassigned range.
 */
static int
in_next_instance_block(major_t major, int block_size)
{
        int             prev;
        struct devnames *dnp;
        in_drv_t        *dp;
        int             base;
        int             hole;

        dnp = &devnamesp[major];
        ASSERT(major != DDI_MAJOR_T_NONE);
        ASSERT(e_ddi_inst_state.ins_busy);
        ASSERT(block_size);

        /* check to see if we can do a quick allocation */
        if (!instance_searchme && (dnp->dn_instance != IN_SEARCHME)) {
                base = dnp->dn_instance;
                dnp->dn_instance += block_size;
                return (base);
        }

        /*
         * Use more complex code path, start by skipping preassign entries.
         */
        for (dp = dnp->dn_inlist; dp; dp = dp->ind_next)
                if (dp->ind_instance >= dnp->dn_pinstance)
                        break;          /* beyond preassign */

        /* No non-preassign entries, allocate block at preassign base. */
        if (dp == NULL) {
                base = dnp->dn_pinstance;
                if (base == 0)
                        dnp->dn_instance = block_size;
                return (base);
        }

        /* See if we fit in hole at beginning (after preassigns) */
        prev = dp->ind_instance;
        if ((prev - dnp->dn_pinstance) >= block_size)
                return (dnp->dn_pinstance);     /* we fit in beginning hole */

        /* search the list for a large enough hole */
        for (dp = dp->ind_next, hole = 0; dp; dp = dp->ind_next) {
                if (dp->ind_instance != (prev + 1))
                        hole++;                 /* we have a hole */
                if (dp->ind_instance >= (prev + block_size + 1))
                        break;                  /* we fit in hole */
                prev = dp->ind_instance;
        }

        /*
         * If hole is zero then all holes are patched and we can resume
         * quick allocations, but don't resume quick allocation if there is
         * a preassign.
         */
        if ((hole == 0) && (dnp->dn_pinstance == 0))
                dnp->dn_instance = prev + 1 + block_size;

        return (prev + 1);
}

/* assign instance block of size 1 */
static int
in_next_instance(major_t major)
{
        return (in_next_instance_block(major, 1));
}

/*
 * This call causes us to *forget* the instance number we've generated
 * for a given device if it was not permanent.
 */
void
e_ddi_free_instance(dev_info_t *dip, char *addr)
{
        char *name;
        in_node_t *np;
        in_node_t *ap;  /* ancestor node */
        major_t major;
        struct devnames *dnp;
        in_drv_t *dp;   /* in_drv entry */

        /*
         * Allow implementation override
         */
        if (impl_free_instance(dip) == DDI_SUCCESS)
                return;

        /*
         * If this is a pseudo-device, no instance number
         * was assigned.
         */
        if (is_pseudo_device(dip)) {
                return;
        }

        name = (char *)ddi_driver_name(dip);
        major = ddi_driver_major(dip);
        ASSERT(major != DDI_MAJOR_T_NONE);
        dnp = &devnamesp[major];
        /*
         * Only one thread is allowed to change the state of the instance
         * number assignments on the system at any given time.
         */
        e_ddi_enter_instance();
        np = in_devwalk(dip, &ap, addr);
        ASSERT(np);

        /*
         * Break the interlink between dip and np
         */
        if (DEVI(dip)->devi_in_node != np || np->in_devi != dip) {
                ddi_err(DER_MODE, dip, "devinfo node linked to "
                    "wrong instance node: %p", (void *)np);
        }
        DEVI(dip)->devi_in_node = NULL;
        np->in_devi = NULL;

        dp = in_drvwalk(np, name);
        ASSERT(dp);
        if (dp->ind_state == IN_PROVISIONAL) {
                in_removedrv(dnp, dp);
        } else if (dp->ind_state == IN_BORROWED) {
                dp->ind_state = IN_PERMANENT;
                e_ddi_return_instance(dip, addr, np);
        }
        if (np->in_drivers == NULL) {
                in_removenode(dnp, np, ap);
        }
        e_ddi_exit_instance();
}

/*
 * This makes our memory of an instance assignment permanent
 */
void
e_ddi_keep_instance(dev_info_t *dip)
{
        in_node_t *np, *ap;
        in_drv_t *dp;

        /* Don't make nulldriver instance assignments permanent */
        if (ddi_driver_major(dip) == nulldriver_major)
                return;

        /*
         * Allow implementation override
         */
        if (impl_keep_instance(dip) == DDI_SUCCESS)
                return;

        /*
         * Nothing to do for pseudo devices.
         */
        if (is_pseudo_device(dip))
                return;

        /*
         * Only one thread is allowed to change the state of the instance
         * number assignments on the system at any given time.
         */
        e_ddi_enter_instance();
        np = in_devwalk(dip, &ap, NULL);
        ASSERT(np);
        dp = in_drvwalk(np, (char *)ddi_driver_name(dip));
        ASSERT(dp);

        mutex_enter(&e_ddi_inst_state.ins_serial);
        if (dp->ind_state == IN_PROVISIONAL || dp->ind_state == IN_BORROWED) {
                dp->ind_state = IN_PERMANENT;
                i_log_devfs_instance_mod();
                e_ddi_inst_state.ins_dirty = B_TRUE;
        }
        mutex_exit(&e_ddi_inst_state.ins_serial);
        e_ddi_exit_instance();
}

/*
 * A new major has been added to the system.  Run through the orphan list
 * and try to attach each one to a driver's list.
 */
void
e_ddi_unorphan_instance_nos()
{
        in_drv_t *dp, *ndp;

        /*
         * disconnect the orphan list, and call in_hashdrv for each item
         * on it
         */

        /*
         * Only one thread is allowed to change the state of the instance
         * number assignments on the system at any given time.
         */
        e_ddi_enter_instance();
        if (e_ddi_inst_state.ins_no_major == NULL) {
                e_ddi_exit_instance();
                return;
        }
        /*
         * Hash instance list to devnames structure of major.
         * Note that if there is not a valid major number for the
         * node, in_hashdrv will put it back on the no_major list.
         */
        dp = e_ddi_inst_state.ins_no_major;
        e_ddi_inst_state.ins_no_major = NULL;
        while (dp) {
                ndp = dp->ind_next;
                ASSERT(dp->ind_state != IN_UNKNOWN);
                dp->ind_next = NULL;
                in_hashdrv(dp);
                dp = ndp;
        }
        e_ddi_exit_instance();
}

static void
in_removenode(struct devnames *dnp, in_node_t *mp, in_node_t *ap)
{
        in_node_t *np;

        ASSERT(e_ddi_inst_state.ins_busy);

        /*
         * Assertion: parents are always instantiated by the framework
         * before their children, destroyed after them
         */
        ASSERT(mp->in_child == NULL);
        /*
         * Assertion: drv entries are always removed before their owning nodes
         */
        ASSERT(mp->in_drivers == NULL);
        /*
         * Take the node out of the tree
         */
        if (ap->in_child == mp) {
                ap->in_child = mp->in_sibling;
                in_dealloc_node(mp);
                return;
        } else {
                for (np = ap->in_child; np; np = np->in_sibling) {
                        if (np->in_sibling == mp) {
                                np->in_sibling = mp->in_sibling;
                                in_dealloc_node(mp);
                                return;
                        }
                }
        }
        panic("in_removenode dnp %p mp %p", (void *)dnp, (void *)mp);
}

/*
 * Recursive ascent
 *
 * This now only does half the job.  It finds the node, then the caller
 * has to search the node for the binding name
 */
static in_node_t *
in_devwalk(dev_info_t *dip, in_node_t **ap, char *addr)
{
        in_node_t *np;
        char *name;

        ASSERT(dip);
        ASSERT(e_ddi_inst_state.ins_busy);
        if (dip == ddi_root_node()) {
                *ap = NULL;
                return (e_ddi_inst_state.ins_root);
        }
        /*
         * call up to find parent, then look through the list of kids
         * for a match
         */
        np = in_devwalk(ddi_get_parent(dip), ap, NULL);
        if (np == NULL)
                return (np);
        *ap = np;
        np = np->in_child;
        name = ddi_node_name(dip);
        if (addr == NULL)
                addr = ddi_get_name_addr(dip);

        while (np) {
                if (in_eqstr(np->in_node_name, name) &&
                    in_eqstr(np->in_unit_addr, addr)) {
                        return (np);
                }
                np = np->in_sibling;
        }

        return (np);
}

/*
 * Create a node specified by cp and assign it the given instance no.
 */
static int
in_pathin(char *cp, int instance, char *bname, struct bind **args)
{
        in_node_t *np;
        in_drv_t *dp;
        char *name;

        ASSERT(e_ddi_inst_state.ins_busy);
        ASSERT(args == NULL);

        /*
         * Give a warning to the console.
         * return value ignored
         */
        if (cp[0] != '/' || instance == -1 || bname == NULL) {
                cmn_err(CE_WARN,
                    "invalid instance file entry %s %d",
                    cp, instance);
                return (0);
        }

        if ((name  = i_binding_to_drv_name(bname)) != NULL)
                bname = name;

        np = in_make_path(cp);
        ASSERT(np);

        dp = in_drvwalk(np, bname);
        if (dp != NULL) {
                cmn_err(CE_WARN,
                    "multiple instance number assignments for "
                    "'%s' (driver %s), %d used",
                    cp, bname, dp->ind_instance);
                return (0);
        }

        if (in_inuse(instance, bname)) {
                cmn_err(CE_WARN,
                    "instance already in use: %s %d", cp, instance);
                return (0);
        }

        dp = in_alloc_drv(bname);
        in_endrv(np, dp);
        dp->ind_instance = instance;
        dp->ind_state = IN_PERMANENT;
        in_hashdrv(dp);

        return (0);
}

/*
 * Create (or find) the node named by path by recursively descending from the
 * root's first child (we ignore the root, which is never named)
 */
static in_node_t *
in_make_path(char *path)
{
        in_node_t *ap;          /* ancestor pointer */
        in_node_t *np;          /* working node pointer */
        in_node_t *rp;          /* return node pointer */
        char buf[MAXPATHLEN];   /* copy of string so we can change it */
        char *cp, *name, *addr;

        ASSERT(e_ddi_inst_state.ins_busy);

        if (path == NULL || path[0] != '/')
                return (NULL);

        (void) snprintf(buf, sizeof (buf), "%s", path);
        cp = buf + 1;   /* skip over initial '/' in path */
        name = in_name_addr(&cp, &addr);

        ap = e_ddi_inst_state.ins_root;
        np = e_ddi_inst_state.ins_root->in_child;
        rp = np;
        while (name) {
                while (name && np) {
                        if (in_eqstr(name, np->in_node_name) &&
                            in_eqstr(addr, np->in_unit_addr)) {
                                name = in_name_addr(&cp, &addr);
                                if (name == NULL)
                                        return (np);
                                ap = np;
                                np = np->in_child;
                        } else {
                                np = np->in_sibling;
                        }
                }
                np = in_alloc_node(name, addr);
                in_enlist(ap, np);      /* insert into tree */
                rp = np;        /* value to return if we quit */
                ap = np;        /* new parent */
                np = NULL;      /* can have no children */
                name = in_name_addr(&cp, &addr);
        }

        return (rp);
}

/*
 * Insert node np into the tree as one of ap's children.
 */
static void
in_enlist(in_node_t *ap, in_node_t *np)
{
        in_node_t *mp;
        ASSERT(e_ddi_inst_state.ins_busy);
        /*
         * Make this node some other node's child or child's sibling
         */
        ASSERT(ap && np);
        if (ap->in_child == NULL) {
                ap->in_child = np;
        } else {
                for (mp = ap->in_child; mp; mp = mp->in_sibling)
                        if (mp->in_sibling == NULL) {
                                mp->in_sibling = np;
                                break;
                        }
        }
        np->in_parent = ap;
}

/*
 * Insert drv entry dp onto a node's driver list
 */
static void
in_endrv(in_node_t *np, in_drv_t *dp)
{
        in_drv_t *mp;
        ASSERT(e_ddi_inst_state.ins_busy);
        ASSERT(np && dp);
        mp = np->in_drivers;
        np->in_drivers = dp;
        dp->ind_next_drv = mp;
        dp->ind_node = np;
}

/*
 * Parse the next name out of the path, null terminate it and update cp.
 * caller has copied string so we can mess with it.
 * Upon return *cpp points to the next section to be parsed, *addrp points
 * to the current address substring (or NULL if none) and we return the
 * current name substring (or NULL if none).  name and address substrings
 * are null terminated in place.
 */

static char *
in_name_addr(char **cpp, char **addrp)
{
        char *namep;    /* return value holder */
        char *ap;       /* pointer to '@' in string */
        char *sp;       /* pointer to '/' in string */

        if (*cpp == NULL || **cpp == '\0') {
                *addrp = NULL;
                return (NULL);
        }
        namep = *cpp;
        sp = strchr(*cpp, '/');
        if (sp != NULL) {       /* more to follow */
                *sp = '\0';
                *cpp = sp + 1;
        } else {                /* this is last component. */
                *cpp = NULL;
        }
        ap = strchr(namep, '@');
        if (ap == NULL) {
                *addrp = NULL;
        } else {
                *ap = '\0';             /* terminate the name */
                *addrp = ap + 1;
        }
        return (namep);
}

/*
 * Allocate a node and storage for name and addr strings, and fill them in.
 */
static in_node_t *
in_alloc_node(char *name, char *addr)
{
        in_node_t *np;
        char *cp;
        size_t namelen;

        ASSERT(e_ddi_inst_state.ins_busy);
        /*
         * Has name or will become root
         */
        ASSERT(name || e_ddi_inst_state.ins_root == NULL);
        if (addr == NULL)
                addr = "";
        if (name == NULL)
                namelen = 0;
        else
                namelen = strlen(name) + 1;
        cp = kmem_zalloc(sizeof (in_node_t) + namelen + strlen(addr) + 1,
            KM_SLEEP);
        np = (in_node_t *)cp;
        if (name) {
                np->in_node_name = cp + sizeof (in_node_t);
                (void) strcpy(np->in_node_name, name);
        }
        np->in_unit_addr = cp + sizeof (in_node_t) + namelen;
        (void) strcpy(np->in_unit_addr, addr);
        return (np);
}

/*
 * Allocate a drv entry and storage for binding name string, and fill it in.
 */
static in_drv_t *
in_alloc_drv(char *bindingname)
{
        in_drv_t *dp;
        char *cp;
        size_t namelen;

        ASSERT(e_ddi_inst_state.ins_busy);
        /*
         * Has name or will become root
         */
        ASSERT(bindingname || e_ddi_inst_state.ins_root == NULL);
        if (bindingname == NULL)
                namelen = 0;
        else
                namelen = strlen(bindingname) + 1;
        cp = kmem_zalloc(sizeof (in_drv_t) + namelen, KM_SLEEP);
        dp = (in_drv_t *)cp;
        if (bindingname) {
                dp->ind_driver_name = cp + sizeof (in_drv_t);
                (void) strcpy(dp->ind_driver_name, bindingname);
        }
        dp->ind_state = IN_UNKNOWN;
        dp->ind_instance = -1;
        return (dp);
}

static void
in_dealloc_node(in_node_t *np)
{
        /*
         * The root node can never be de-allocated
         */
        ASSERT(np->in_node_name && np->in_unit_addr);
        ASSERT(e_ddi_inst_state.ins_busy);
        kmem_free(np, sizeof (in_node_t) + strlen(np->in_node_name)
            + strlen(np->in_unit_addr) + 2);
}

static void
in_dealloc_drv(in_drv_t *dp)
{
        ASSERT(dp->ind_driver_name);
        ASSERT(e_ddi_inst_state.ins_busy);
        kmem_free(dp, sizeof (in_drv_t) + strlen(dp->ind_driver_name)
            + 1);
}

/*
 * Handle the various possible versions of "no address"
 */
static int
in_eqstr(char *a, char *b)
{
        if (a == b)     /* covers case where both are nulls */
                return (1);
        if (a == NULL && *b == 0)
                return (1);
        if (b == NULL && *a == 0)
                return (1);
        if (a == NULL || b == NULL)
                return (0);
        return (strcmp(a, b) == 0);
}

/*
 * Returns true if instance no. is already in use by named driver
 */
static int
in_inuse(int instance, char *name)
{
        major_t major;
        in_drv_t *dp;
        struct devnames *dnp;

        ASSERT(e_ddi_inst_state.ins_busy);
        /*
         * For now, if we've never heard of this device we assume it is not
         * in use, since we can't tell
         * XXX could do the weaker search through the nomajor list checking
         * XXX for the same name
         */
        if ((major = ddi_name_to_major(name)) == DDI_MAJOR_T_NONE)
                return (0);
        dnp = &devnamesp[major];

        dp = dnp->dn_inlist;
        while (dp) {
                if (dp->ind_instance == instance)
                        return (1);
                dp = dp->ind_next;
        }
        return (0);
}

static void
in_hashdrv(in_drv_t *dp)
{
        struct devnames *dnp;
        in_drv_t *mp, *pp;
        major_t major;

        /* hash to no major list */
        major = ddi_name_to_major(dp->ind_driver_name);
        if (major == DDI_MAJOR_T_NONE) {
                dp->ind_next = e_ddi_inst_state.ins_no_major;
                e_ddi_inst_state.ins_no_major = dp;
                return;
        }

        /*
         * dnp->dn_inlist is sorted by instance number.
         * Adding a new instance entry may introduce holes,
         * set dn_instance to IN_SEARCHME so the next instance
         * assignment may fill in holes.
         */
        dnp = &devnamesp[major];
        pp = mp = dnp->dn_inlist;
        if (mp == NULL || dp->ind_instance < mp->ind_instance) {
                /* prepend as the first entry, turn on IN_SEARCHME */
                dnp->dn_instance = IN_SEARCHME;
                dp->ind_next = mp;
                dnp->dn_inlist = dp;
                return;
        }

        ASSERT(mp->ind_instance != dp->ind_instance);
        while (mp->ind_instance < dp->ind_instance && mp->ind_next) {
                pp = mp;
                mp = mp->ind_next;
                ASSERT(mp->ind_instance != dp->ind_instance);
        }

        if (mp->ind_instance < dp->ind_instance) { /* end of list */
                dp->ind_next = NULL;
                mp->ind_next = dp;
        } else {
                dp->ind_next = pp->ind_next;
                pp->ind_next = dp;
        }
}

/*
 * Remove a driver entry from the list, given a previous pointer
 */
static void
in_removedrv(struct devnames *dnp, in_drv_t *mp)
{
        in_drv_t *dp;
        in_drv_t *prevp;

        if (dnp->dn_inlist == mp) {     /* head of list */
                dnp->dn_inlist = mp->ind_next;
                dnp->dn_instance = IN_SEARCHME;
                in_dq_drv(mp);
                in_dealloc_drv(mp);
                return;
        }
        prevp = dnp->dn_inlist;
        for (dp = prevp->ind_next; dp; dp = dp->ind_next) {
                if (dp == mp) {         /* found it */
                        break;
                }
                prevp = dp;
        }

        ASSERT(dp == mp);
        dnp->dn_instance = IN_SEARCHME;
        prevp->ind_next = mp->ind_next;
        in_dq_drv(mp);
        in_dealloc_drv(mp);
}

static void
in_dq_drv(in_drv_t *mp)
{
        struct in_node *node = mp->ind_node;
        in_drv_t *ptr, *prev;

        if (mp == node->in_drivers) {
                node->in_drivers = mp->ind_next_drv;
                return;
        }
        prev = node->in_drivers;
        for (ptr = prev->ind_next_drv; ptr != NULL;
            ptr = ptr->ind_next_drv) {
                if (ptr == mp) {
                        prev->ind_next_drv = ptr->ind_next_drv;
                        return;
                }
                prev = ptr;
        }
        panic("in_dq_drv: in_drv not found on node driver list");
}


in_drv_t *
in_drvwalk(in_node_t *np, char *binding_name)
{
        char *name;
        in_drv_t *dp = np->in_drivers;
        while (dp) {
                if ((name = i_binding_to_drv_name(dp->ind_driver_name))
                    == NULL) {
                        name = dp->ind_driver_name;
                }
                if (strcmp(binding_name, name) == 0) {
                        break;
                }
                dp = dp->ind_next_drv;
        }
        return (dp);
}



static void
i_log_devfs_instance_mod(void)
{
        sysevent_t      *ev;
        sysevent_id_t   eid;
        static int      sent_one = 0;

        /*
         * Prevent unnecessary event generation.  Do not generate more than
         * one event during boot.
         */
        if (sent_one && !i_ddi_io_initialized())
                return;

        ev = sysevent_alloc(EC_DEVFS, ESC_DEVFS_INSTANCE_MOD, EP_DDI,
            SE_NOSLEEP);
        if (ev == NULL) {
                return;
        }
        if (log_sysevent(ev, SE_NOSLEEP, &eid) != 0) {
                cmn_err(CE_WARN, "i_log_devfs_instance_mod: failed to post "
                    "event");
        } else {
                sent_one = 1;
        }
        sysevent_free(ev);
}

void
e_ddi_enter_instance(void)
{
        mutex_enter(&e_ddi_inst_state.ins_serial);
        if (e_ddi_inst_state.ins_thread == curthread)
                e_ddi_inst_state.ins_busy++;
        else {
                while (e_ddi_inst_state.ins_busy)
                        cv_wait(&e_ddi_inst_state.ins_serial_cv,
                            &e_ddi_inst_state.ins_serial);
                e_ddi_inst_state.ins_thread = curthread;
                e_ddi_inst_state.ins_busy = 1;
        }
        mutex_exit(&e_ddi_inst_state.ins_serial);
}

void
e_ddi_exit_instance(void)
{
        mutex_enter(&e_ddi_inst_state.ins_serial);
        e_ddi_inst_state.ins_busy--;
        if (e_ddi_inst_state.ins_busy == 0) {
                cv_broadcast(&e_ddi_inst_state.ins_serial_cv);
                e_ddi_inst_state.ins_thread = NULL;
        }
        mutex_exit(&e_ddi_inst_state.ins_serial);
}

int
e_ddi_instance_is_clean(void)
{
        return (e_ddi_inst_state.ins_dirty == B_FALSE);
}

void
e_ddi_instance_set_clean(void)
{
        e_ddi_inst_state.ins_dirty = B_FALSE;
}

in_node_t *
e_ddi_instance_root(void)
{
        return (e_ddi_inst_state.ins_root);
}

/*
 * Visit a node in the instance tree
 */
static int
in_walk_instances(in_node_t *np, char *path, char *this,
    int (*f)(const char *, in_node_t *, in_drv_t *, void *), void *arg)
{
        in_drv_t *dp;
        int rval = INST_WALK_CONTINUE;
        char *next;

        while (np != NULL) {

                if (np->in_unit_addr[0] == 0)
                        (void) sprintf(this, "/%s", np->in_node_name);
                else
                        (void) sprintf(this, "/%s@%s", np->in_node_name,
                            np->in_unit_addr);
                next = this + strlen(this);

                for (dp = np->in_drivers; dp; dp = dp->ind_next_drv) {
                        if (dp->ind_state == IN_PERMANENT) {
                                rval = (*f)(path, np, dp, arg);
                                if (rval == INST_WALK_TERMINATE)
                                        break;
                        }
                }

                if (np->in_child) {
                        rval = in_walk_instances(np->in_child,
                            path, next, f, arg);
                        if (rval == INST_WALK_TERMINATE)
                                break;
                }

                np = np->in_sibling;
        }

        return (rval);
}

/*
 * A general interface for walking the instance tree,
 * calling a user-supplied callback for each node.
 */
int
e_ddi_walk_instances(int (*f)(const char *,
        in_node_t *, in_drv_t *, void *), void *arg)
{
        in_node_t *root;
        int rval;
        char *path;

        path = kmem_zalloc(MAXPATHLEN, KM_SLEEP);

        e_ddi_enter_instance();
        root = e_ddi_instance_root();
        rval = in_walk_instances(root->in_child, path, path, f, arg);

        e_ddi_exit_instance();

        kmem_free(path, MAXPATHLEN);
        return (rval);
}

in_node_t *
e_ddi_path_to_instance(char *path)
{
        in_node_t *np;

        np = in_make_path(path);
        if (np && np->in_drivers && np->in_drivers->ind_state == IN_PERMANENT) {
                return (np);
        }
        return (NULL);
}

void
e_ddi_borrow_instance(dev_info_t *cdip, in_node_t *cnp)
{
        char            *alias;
        in_node_t       *anp;
        char            *curr = kmem_alloc(MAXPATHLEN, KM_NOSLEEP);

        if (curr == NULL) {
                ddi_err(DER_PANIC, cdip, "curr alloc failed");
                /*NOTREACHED*/
        }

        (void) ddi_pathname(cdip, curr);

        if (cnp->in_drivers) {
                /* there can be multiple drivers bound */
                ddi_err(DER_LOG, cdip, "%s has previous binding: %s", curr,
                    cnp->in_drivers->ind_driver_name);
        }

        alias = ddi_curr_redirect(curr);

        /* bail here if the alias matches any other current path or itself */
        if (alias && ((strcmp(curr, alias) == 0) ||
            (ddi_curr_redirect(alias) != 0))) {
                DDI_MP_DBG((CE_NOTE, "not borrowing current: %s alias: %s",
                    curr, alias));
                goto out;
        }

        if (alias && (anp = e_ddi_path_to_instance(alias)) != NULL) {
                /*
                 * Since pcieb nodes can split and merge, it is dangerous
                 * to borrow and instance for them. However since they do
                 * not expose their instance numbers it is safe to never
                 * borrow one.
                 */
                if (anp->in_drivers->ind_driver_name &&
                    (strcmp(anp->in_drivers->ind_driver_name, "pcieb") == 0)) {
                        DDI_MP_DBG((CE_NOTE, "not borrowing pcieb: "
                            "%s alias: %s", curr, alias));
                        goto out;
                }
                DDI_MP_DBG((CE_NOTE, "borrowing current: %s alias: %s",
                    curr, alias));
                cnp->in_drivers = anp->in_drivers;
                anp->in_drivers = NULL;
        }
out:
        kmem_free(curr, MAXPATHLEN);
}

void
e_ddi_return_instance(dev_info_t *cdip, char *addr, in_node_t *cnp)
{
        in_node_t       *anp;
        char            *alias;
        char            *curr = kmem_alloc(MAXPATHLEN, KM_NOSLEEP);

        if (curr == NULL) {
                ddi_err(DER_PANIC, cdip, "alloc of curr failed");
                /*NOTREACHED*/
        }

        (void) ddi_pathname(cdip, curr);
        if (addr) {
                (void) strlcat(curr, "@", MAXPATHLEN);
                (void) strlcat(curr, addr, MAXPATHLEN);

        }
        if (cnp->in_drivers == NULL) {
                ddi_err(DER_PANIC, cdip, "cnp has no inst: %p", cnp);
                /*NOTREACHED*/
        }

        alias = ddi_curr_redirect(curr);
        kmem_free(curr, MAXPATHLEN);

        if (alias && (anp = e_ddi_path_to_instance(alias)) != NULL) {
                ASSERT(anp->in_drivers == NULL);
                anp->in_drivers = cnp->in_drivers;
                cnp->in_drivers = NULL;
        }
}