sys: Some whitespace cleanup.

[dragonfly.git] / sys / dev / acpica / acpi_powerres.c

/*-
 * Copyright (c) 2001 Michael Smith
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 * $FreeBSD: src/sys/dev/acpica/acpi_powerres.c,v 1.30.8.1 2009/04/15 03:14:26 kensmith Exp $
 */

#include "opt_acpi.h"
#include <sys/param.h>
#include <sys/kernel.h>
#include <sys/malloc.h>
#include <sys/bus.h>

#include "acpi.h"
#include <dev/acpica/acpivar.h>

/*
 * ACPI power resource management.
 *
 * Power resource behaviour is slightly complicated by the fact that
 * a single power resource may provide power for more than one device.
 * Thus, we must track the device(s) being powered by a given power
 * resource, and only deactivate it when there are no powered devices.
 *
 * Note that this only manages resources for known devices.  There is an
 * ugly case where we may turn of power to a device which is in use because
 * we don't know that it depends on a given resource.  We should perhaps
 * try to be smarter about this, but a more complete solution would involve
 * scanning all of the ACPI namespace to find devices we're not currently
 * aware of, and this raises questions about whether they should be left 
 * on, turned off, etc.
 */

MALLOC_DEFINE(M_ACPIPWR, "acpipwr", "ACPI power resources");

/* Hooks for the ACPICA debugging infrastructure */
#define _COMPONENT      ACPI_POWERRES
ACPI_MODULE_NAME("POWERRES")

/* Return values from _STA on a power resource */
#define ACPI_PWR_OFF    0
#define ACPI_PWR_ON     1
#define ACPI_PWR_UNK    (-1)

/* A relationship between a power resource and a consumer. */
struct acpi_powerreference {
    struct acpi_powerconsumer           *ar_consumer;
    struct acpi_powerresource           *ar_resource;
    TAILQ_ENTRY(acpi_powerreference)    ar_rlink; /* link on resource list */
    TAILQ_ENTRY(acpi_powerreference)    ar_clink; /* link on consumer */
};
    
/* A power-managed device. */
struct acpi_powerconsumer {
    /* Device which is powered */
    ACPI_HANDLE                         ac_consumer;
    int                                 ac_state;
    TAILQ_ENTRY(acpi_powerconsumer)     ac_link;
    TAILQ_HEAD(,acpi_powerreference)    ac_references;
};

/* A power resource. */
struct acpi_powerresource {
    TAILQ_ENTRY(acpi_powerresource)     ap_link;
    TAILQ_HEAD(,acpi_powerreference)    ap_references;
    ACPI_HANDLE                         ap_resource;
    UINT64                              ap_systemlevel;
    UINT64                              ap_order;
    int                                 ap_state;
};

static TAILQ_HEAD(acpi_powerresource_list, acpi_powerresource)
        acpi_powerresources;
static TAILQ_HEAD(acpi_powerconsumer_list, acpi_powerconsumer)
        acpi_powerconsumers;
ACPI_SERIAL_DECL(powerres, "ACPI power resources");

static ACPI_STATUS      acpi_pwr_register_consumer(ACPI_HANDLE consumer);
#ifdef notyet
static ACPI_STATUS      acpi_pwr_deregister_consumer(ACPI_HANDLE consumer);
#endif /* notyet */
static ACPI_STATUS      acpi_pwr_register_resource(ACPI_HANDLE res);
#ifdef notyet
static ACPI_STATUS      acpi_pwr_deregister_resource(ACPI_HANDLE res);
#endif /* notyet */
static void             acpi_pwr_reference_resource(ACPI_OBJECT *obj,
                                                    void *arg);
static int              acpi_pwr_dereference_resource(struct acpi_powerconsumer
                            *pc);
static ACPI_STATUS      acpi_pwr_switch_power(void);
static struct acpi_powerresource
                        *acpi_pwr_find_resource(ACPI_HANDLE res);
static struct acpi_powerconsumer
                        *acpi_pwr_find_consumer(ACPI_HANDLE consumer);

/* Initialise our lists. */    
static void
acpi_pwr_init(void *junk)
{
    ACPI_SERIAL_INIT(powerres);
    TAILQ_INIT(&acpi_powerresources);
    TAILQ_INIT(&acpi_powerconsumers);
}
SYSINIT(acpi_powerresource, SI_BOOT1_TUNABLES, SI_ORDER_ANY, acpi_pwr_init, NULL);

/*
 * Register a power resource.
 *
 * It's OK to call this if we already know about the resource.
 */
static ACPI_STATUS
acpi_pwr_register_resource(ACPI_HANDLE res)
{
    ACPI_STATUS                 status;
    ACPI_BUFFER                 buf;
    ACPI_OBJECT                 *obj;
    struct acpi_powerresource   *rp, *srp;

    ACPI_FUNCTION_TRACE((char *)(uintptr_t)__func__);
    ACPI_SERIAL_ASSERT(powerres);

    rp = NULL;
    buf.Pointer = NULL;
    
    /* Look to see if we know about this resource */
    if (acpi_pwr_find_resource(res) != NULL)
        return_ACPI_STATUS (AE_OK);             /* already know about it */

    /* Allocate a new resource */
    if ((rp = kmalloc(sizeof(*rp), M_ACPIPWR, M_NOWAIT | M_ZERO)) == NULL) {
        status = AE_NO_MEMORY;
        goto out;
    }
    TAILQ_INIT(&rp->ap_references);
    rp->ap_resource = res;

    /* Get the Power Resource object */
    buf.Length = ACPI_ALLOCATE_BUFFER;
    if (ACPI_FAILURE(status = AcpiEvaluateObject(res, NULL, NULL, &buf))) {
        ACPI_DEBUG_PRINT((ACPI_DB_OBJECTS, "no power resource object\n"));
        goto out;
    }
    obj = buf.Pointer;
    if (obj->Type != ACPI_TYPE_POWER) {
        ACPI_DEBUG_PRINT((ACPI_DB_OBJECTS,
                         "questionable power resource object %s\n",
                         acpi_name(res)));
        status = AE_TYPE;
        goto out;
    }
    rp->ap_systemlevel = obj->PowerResource.SystemLevel;
    rp->ap_order = obj->PowerResource.ResourceOrder;
    rp->ap_state = ACPI_PWR_UNK;
    
    /* Sort the resource into the list */
    status = AE_OK;
    srp = TAILQ_FIRST(&acpi_powerresources);
    if (srp == NULL || rp->ap_order < srp->ap_order) {
        TAILQ_INSERT_HEAD(&acpi_powerresources, rp, ap_link);
        goto done;
    }
    TAILQ_FOREACH(srp, &acpi_powerresources, ap_link) {
        if (rp->ap_order < srp->ap_order) {
            TAILQ_INSERT_BEFORE(srp, rp, ap_link);
            goto done;
        }
    }
    TAILQ_INSERT_TAIL(&acpi_powerresources, rp, ap_link);

 done:
    ACPI_DEBUG_PRINT((ACPI_DB_OBJECTS,
                     "registered power resource %s\n", acpi_name(res)));

 out:
    if (buf.Pointer != NULL)
        AcpiOsFree(buf.Pointer);
    if (ACPI_FAILURE(status) && rp != NULL)
        kfree(rp, M_ACPIPWR);
    return_ACPI_STATUS (status);
}

#ifdef notyet
/*
 * Deregister a power resource.
 */
static ACPI_STATUS
acpi_pwr_deregister_resource(ACPI_HANDLE res)
{
    struct acpi_powerresource   *rp;

    ACPI_FUNCTION_TRACE((char *)(uintptr_t)__func__);
    ACPI_SERIAL_ASSERT(powerres);

    rp = NULL;
    
    /* Find the resource */
    if ((rp = acpi_pwr_find_resource(res)) == NULL)
        return_ACPI_STATUS (AE_BAD_PARAMETER);

    /* Check that there are no consumers referencing this resource */
    if (TAILQ_FIRST(&rp->ap_references) != NULL)
        return_ACPI_STATUS (AE_BAD_PARAMETER);

    /* Pull it off the list and kfree it */
    TAILQ_REMOVE(&acpi_powerresources, rp, ap_link);
    kfree(rp, M_ACPIPWR);

    ACPI_DEBUG_PRINT((ACPI_DB_OBJECTS, "deregistered power resource %s\n",
                     acpi_name(res)));

    return_ACPI_STATUS (AE_OK);
}
#endif /* notyet */

/*
 * Register a power consumer.  
 *
 * It's OK to call this if we already know about the consumer.
 */
static ACPI_STATUS
acpi_pwr_register_consumer(ACPI_HANDLE consumer)
{
    struct acpi_powerconsumer   *pc;
    
    ACPI_FUNCTION_TRACE((char *)(uintptr_t)__func__);
    ACPI_SERIAL_ASSERT(powerres);

    /* Check to see whether we know about this consumer already */
    if (acpi_pwr_find_consumer(consumer) != NULL)
        return_ACPI_STATUS (AE_OK);
    
    /* Allocate a new power consumer */
    if ((pc = kmalloc(sizeof(*pc), M_ACPIPWR, M_NOWAIT)) == NULL)
        return_ACPI_STATUS (AE_NO_MEMORY);
    TAILQ_INSERT_HEAD(&acpi_powerconsumers, pc, ac_link);
    TAILQ_INIT(&pc->ac_references);
    pc->ac_consumer = consumer;

    /* XXX we should try to find its current state */
    pc->ac_state = ACPI_STATE_UNKNOWN;

    ACPI_DEBUG_PRINT((ACPI_DB_OBJECTS, "registered power consumer %s\n",
                     acpi_name(consumer)));
    
    return_ACPI_STATUS (AE_OK);
}

#ifdef notyet
/*
 * Deregister a power consumer.
 *
 * This should only be done once the consumer has been powered off.
 * (XXX is this correct?  Check once implemented)
 */
static ACPI_STATUS
acpi_pwr_deregister_consumer(ACPI_HANDLE consumer)
{
    struct acpi_powerconsumer   *pc;
    
    ACPI_FUNCTION_TRACE((char *)(uintptr_t)__func__);
    ACPI_SERIAL_ASSERT(powerres);

    /* Find the consumer */
    if ((pc = acpi_pwr_find_consumer(consumer)) == NULL)
        return_ACPI_STATUS (AE_BAD_PARAMETER);
    
    /* Make sure the consumer's not referencing anything right now */
    if (TAILQ_FIRST(&pc->ac_references) != NULL)
        return_ACPI_STATUS (AE_BAD_PARAMETER);

    /* Pull the consumer off the list and kfree it */
    TAILQ_REMOVE(&acpi_powerconsumers, pc, ac_link);
    kfree(pc, M_ACPIPWR);

    ACPI_DEBUG_PRINT((ACPI_DB_OBJECTS, "deregistered power consumer %s\n",
                     acpi_name(consumer)));

    return_ACPI_STATUS (AE_OK);
}
#endif /* notyet */

/*
 * Set a power consumer to a particular power state.
 */
ACPI_STATUS
acpi_pwr_switch_consumer(ACPI_HANDLE consumer, int state)
{
    struct acpi_powerconsumer   *pc;
    ACPI_HANDLE                 method_handle, reslist_handle, pr0_handle;
    ACPI_BUFFER                 reslist_buffer;
    ACPI_OBJECT                 *reslist_object;
    ACPI_STATUS                 status;
    char                        *method_name, *reslist_name;

    ACPI_FUNCTION_TRACE((char *)(uintptr_t)__func__);

    /* It's never ok to switch a non-existent consumer. */
    if (consumer == NULL)
        return_ACPI_STATUS (AE_NOT_FOUND);
    reslist_buffer.Pointer = NULL;
    reslist_object = NULL;
    ACPI_SERIAL_BEGIN(powerres);

    /* Find the consumer */
    if ((pc = acpi_pwr_find_consumer(consumer)) == NULL) {
        if (ACPI_FAILURE(status = acpi_pwr_register_consumer(consumer)))
            goto out;
        if ((pc = acpi_pwr_find_consumer(consumer)) == NULL)
            panic("acpi added power consumer but can't find it");
    }

    /* Check for valid transitions.  We can only go to D0 from D3. */
    status = AE_BAD_PARAMETER;
    if (pc->ac_state == ACPI_STATE_D3 && state != ACPI_STATE_D0)
        goto out;

    /* Find transition mechanism(s) */
    switch (state) {
    case ACPI_STATE_D0:
        method_name = "_PS0";
        reslist_name = "_PR0";
        break;
    case ACPI_STATE_D1:
        method_name = "_PS1";
        reslist_name = "_PR1";
        break;
    case ACPI_STATE_D2:
        method_name = "_PS2";
        reslist_name = "_PR2";
        break;
    case ACPI_STATE_D3:
        method_name = "_PS3";
        reslist_name = "_PR3";
        break;
    default:
        goto out;
    }
    ACPI_DEBUG_PRINT((ACPI_DB_OBJECTS, "setup to switch %s D%d -> D%d\n",
                     acpi_name(consumer), pc->ac_state, state));

    /*
     * Verify that this state is supported, ie. one of method or
     * reslist must be present.  We need to do this before we go 
     * dereferencing resources (since we might be trying to go to
     * a state we don't support).
     *
     * Note that if any states are supported, the device has to
     * support D0 and D3.  It's never an error to try to go to
     * D0.
     */
    if (ACPI_FAILURE(AcpiGetHandle(consumer, method_name, &method_handle)))
        method_handle = NULL;
    if (ACPI_FAILURE(AcpiGetHandle(consumer, reslist_name, &reslist_handle)))
        reslist_handle = NULL;
    if (reslist_handle == NULL && method_handle == NULL) {
        if (state == ACPI_STATE_D0) {
            pc->ac_state = ACPI_STATE_D0;
            status = AE_OK;
            goto out;
        }
        if (state != ACPI_STATE_D3) {
            ACPI_DEBUG_PRINT((ACPI_DB_OBJECTS,
                "attempt to set unsupported state D%d\n", state));
            goto out;
        }

        /*
         * Turn off the resources listed in _PR0 to go to D3.  If there is
         * no _PR0 method, this object doesn't support ACPI power states.
         */
        if (ACPI_FAILURE(AcpiGetHandle(consumer, "_PR0", &pr0_handle))) {
            status = AE_NOT_FOUND;
            ACPI_DEBUG_PRINT((ACPI_DB_OBJECTS,
                "device missing _PR0 (desired state was D%d)\n", state));
            goto out;
        }
        reslist_buffer.Length = ACPI_ALLOCATE_BUFFER;
        status = AcpiEvaluateObject(pr0_handle, NULL, NULL, &reslist_buffer);
        if (ACPI_FAILURE(status)) {
            ACPI_DEBUG_PRINT((ACPI_DB_OBJECTS,
                "can't evaluate _PR0 for device %s, state D%d\n",
                acpi_name(consumer), state));
            goto out;
        }
        reslist_object = (ACPI_OBJECT *)reslist_buffer.Pointer;
        if (!ACPI_PKG_VALID(reslist_object, 1)) {
            ACPI_DEBUG_PRINT((ACPI_DB_OBJECTS,
                "invalid package object for state D%d\n", state));
            status = AE_TYPE;
            goto out;
        }
        AcpiOsFree(reslist_buffer.Pointer);
        reslist_buffer.Pointer = NULL;
        reslist_object = NULL;
    }

    /*
     * Check that we can actually fetch the list of power resources
     */
    if (reslist_handle != NULL) {
        reslist_buffer.Length = ACPI_ALLOCATE_BUFFER;
        status = AcpiEvaluateObject(reslist_handle, NULL, NULL,
                                    &reslist_buffer);
        if (ACPI_FAILURE(status)) {
            ACPI_DEBUG_PRINT((ACPI_DB_OBJECTS,
                             "can't evaluate resource list %s\n",
                             acpi_name(reslist_handle)));
            goto out;
        }
        reslist_object = (ACPI_OBJECT *)reslist_buffer.Pointer;
        if (reslist_object->Type != ACPI_TYPE_PACKAGE) {
            ACPI_DEBUG_PRINT((ACPI_DB_OBJECTS,
                             "resource list is not ACPI_TYPE_PACKAGE (%d)\n",
                             reslist_object->Type));
            status = AE_TYPE;
            goto out;
        }
    }

    /*
     * Now we are ready to switch, so kill off any current power
     * resource references.
     */
    acpi_pwr_dereference_resource(pc);

    /*
     * Add new power resource references, if we have any.  Traverse the
     * package that we got from evaluating reslist_handle, and look up each
     * of the resources that are referenced.
     */
    if (reslist_object != NULL) {
        ACPI_DEBUG_PRINT((ACPI_DB_OBJECTS, "referencing %d new resources\n", 
                          reslist_object->Package.Count));
        acpi_ForeachPackageObject(reslist_object, acpi_pwr_reference_resource,
                                  pc);
    }

    /*
     * If we changed anything in the resource list, we need to run a switch
     * pass now.
     */
    if (ACPI_FAILURE(status = acpi_pwr_switch_power())) {
        ACPI_DEBUG_PRINT((ACPI_DB_OBJECTS,
                         "failed to switch resources from %s to D%d\n",
                          acpi_name(consumer), state));

        /* XXX is this appropriate?  Should we return to previous state? */
        goto out;
    }

    /* Invoke power state switch method (if present) */
    if (method_handle != NULL) {
        ACPI_DEBUG_PRINT((ACPI_DB_OBJECTS,
                         "invoking state transition method %s\n",
                         acpi_name(method_handle)));
        status = AcpiEvaluateObject(method_handle, NULL, NULL, NULL);
        if (ACPI_FAILURE(status)) {
                ACPI_DEBUG_PRINT((ACPI_DB_OBJECTS, "failed to set state - %s\n",
                                 AcpiFormatException(status)));
                pc->ac_state = ACPI_STATE_UNKNOWN;

                /* XXX Should we return to previous state? */
                goto out;
        }
    }

    /* Transition was successful */
    pc->ac_state = state;
    status = AE_OK;

out:
    ACPI_SERIAL_END(powerres);
    if (reslist_buffer.Pointer != NULL)
        AcpiOsFree(reslist_buffer.Pointer);
    return_ACPI_STATUS (status);
}

/* Enable or disable a power resource for wake */
ACPI_STATUS
acpi_pwr_wake_enable(ACPI_HANDLE consumer, int enable)
{
    ACPI_STATUS status;
    struct acpi_powerconsumer *pc;
    struct acpi_prw_data prw;
    int i;

    ACPI_FUNCTION_TRACE((char *)(uintptr_t)__func__);

    if (consumer == NULL)
        return (AE_BAD_PARAMETER);

    ACPI_SERIAL_BEGIN(powerres);
    if ((pc = acpi_pwr_find_consumer(consumer)) == NULL) {
        if (ACPI_FAILURE(status = acpi_pwr_register_consumer(consumer)))
            goto out;
        if ((pc = acpi_pwr_find_consumer(consumer)) == NULL)
            panic("acpi wake added power consumer but can't find it");
    }

    status = AE_OK;
    if (acpi_parse_prw(consumer, &prw) != 0)
        goto out;
    for (i = 0; i < prw.power_res_count; i++)
        if (enable)
            acpi_pwr_reference_resource(&prw.power_res[i], pc);
        else
            acpi_pwr_dereference_resource(pc);

    if (prw.power_res_count > 0)
        acpi_pwr_switch_power();

out:
    ACPI_SERIAL_END(powerres);
    return (status);
}

/*
 * Called to create a reference between a power consumer and a power resource
 * identified in the object.
 */
static void
acpi_pwr_reference_resource(ACPI_OBJECT *obj, void *arg)
{
    struct acpi_powerconsumer   *pc = (struct acpi_powerconsumer *)arg;
    struct acpi_powerreference  *pr;
    struct acpi_powerresource   *rp;
    ACPI_HANDLE                 res;
    ACPI_STATUS                 status;

    ACPI_FUNCTION_TRACE((char *)(uintptr_t)__func__);
    ACPI_SERIAL_ASSERT(powerres);

    res = acpi_GetReference(NULL, obj);
    if (res == NULL) {
        ACPI_DEBUG_PRINT((ACPI_DB_OBJECTS,
                         "can't create a power reference for object type %d\n",
                         obj->Type));
        return_VOID;
    }

    /* Create/look up the resource */
    if (ACPI_FAILURE(status = acpi_pwr_register_resource(res))) {
        ACPI_DEBUG_PRINT((ACPI_DB_OBJECTS,
                         "couldn't register power resource %s - %s\n",
                         obj->String.Pointer, AcpiFormatException(status)));
        return_VOID;
    }
    if ((rp = acpi_pwr_find_resource(res)) == NULL) {
        ACPI_DEBUG_PRINT((ACPI_DB_OBJECTS, "power resource list corrupted\n"));
        return_VOID;
    }
    ACPI_DEBUG_PRINT((ACPI_DB_OBJECTS, "found power resource %s\n",
                     acpi_name(rp->ap_resource)));

    /* Create a reference between the consumer and resource */
    if ((pr = kmalloc(sizeof(*pr), M_ACPIPWR, M_NOWAIT | M_ZERO)) == NULL) {
        ACPI_DEBUG_PRINT((ACPI_DB_OBJECTS,
                         "allocation failed for a power consumer reference\n"));
        return_VOID;
    }
    pr->ar_consumer = pc;
    pr->ar_resource = rp;
    TAILQ_INSERT_TAIL(&pc->ac_references, pr, ar_clink);
    TAILQ_INSERT_TAIL(&rp->ap_references, pr, ar_rlink);

    return_VOID;
}

static int
acpi_pwr_dereference_resource(struct acpi_powerconsumer *pc)
{
    struct acpi_powerreference *pr;
    int changed;

    ACPI_FUNCTION_TRACE((char *)(uintptr_t)__func__);
    ACPI_SERIAL_ASSERT(powerres);

    changed = 0;
    while ((pr = TAILQ_FIRST(&pc->ac_references)) != NULL) {
        ACPI_DEBUG_PRINT((ACPI_DB_OBJECTS, "removing reference to %s\n",
                         acpi_name(pr->ar_resource->ap_resource)));
        TAILQ_REMOVE(&pr->ar_resource->ap_references, pr, ar_rlink);
        TAILQ_REMOVE(&pc->ac_references, pr, ar_clink);
        kfree(pr, M_ACPIPWR);
        changed = 1;
    }

    return (changed);
}

/*
 * Switch power resources to conform to the desired state.
 *
 * Consumers may have modified the power resource list in an arbitrary
 * fashion; we sweep it in sequence order.
 */
static ACPI_STATUS
acpi_pwr_switch_power(void)
{
    struct acpi_powerresource   *rp;
    ACPI_STATUS                 status;
    int                         cur;

    ACPI_FUNCTION_TRACE((char *)(uintptr_t)__func__);
    ACPI_SERIAL_ASSERT(powerres);

    /*
     * Sweep the list forwards turning things on.
     */
    TAILQ_FOREACH(rp, &acpi_powerresources, ap_link) {
        if (TAILQ_FIRST(&rp->ap_references) == NULL) {
            ACPI_DEBUG_PRINT((ACPI_DB_OBJECTS,
                             "%s has no references, not turning on\n",
                             acpi_name(rp->ap_resource)));
            continue;
        }

        /* We could cache this if we trusted it not to change under us */
        status = acpi_GetInteger(rp->ap_resource, "_STA", &cur);
        if (ACPI_FAILURE(status)) {
            ACPI_DEBUG_PRINT((ACPI_DB_OBJECTS, "can't get status of %s - %d\n",
                              acpi_name(rp->ap_resource), status));
            /* XXX is this correct?  Always switch if in doubt? */
            continue;
        } else if (rp->ap_state == ACPI_PWR_UNK)
            rp->ap_state = cur;

        /*
         * Switch if required.  Note that we ignore the result of the switch
         * effort; we don't know what to do if it fails, so checking wouldn't
         * help much.
         */
        if (rp->ap_state != ACPI_PWR_ON) {
            status = AcpiEvaluateObject(rp->ap_resource, "_ON", NULL, NULL);
            if (ACPI_FAILURE(status)) {
                ACPI_DEBUG_PRINT((ACPI_DB_OBJECTS,
                                 "failed to switch %s on - %s\n", 
                                 acpi_name(rp->ap_resource),
                                 AcpiFormatException(status)));
            } else {
                rp->ap_state = ACPI_PWR_ON;
                ACPI_DEBUG_PRINT((ACPI_DB_OBJECTS, "switched %s on\n",
                                 acpi_name(rp->ap_resource)));
            }
        } else {
            ACPI_DEBUG_PRINT((ACPI_DB_OBJECTS, "%s is already on\n",
                             acpi_name(rp->ap_resource)));
        }
    }
    
    /* Sweep the list backwards turning things off. */
    TAILQ_FOREACH_REVERSE(rp, &acpi_powerresources, acpi_powerresource_list,
        ap_link) {

        if (TAILQ_FIRST(&rp->ap_references) != NULL) {
            ACPI_DEBUG_PRINT((ACPI_DB_OBJECTS,
                             "%s has references, not turning off\n",
                             acpi_name(rp->ap_resource)));
            continue;
        }

        /* We could cache this if we trusted it not to change under us */
        status = acpi_GetInteger(rp->ap_resource, "_STA", &cur);
        if (ACPI_FAILURE(status)) {
            ACPI_DEBUG_PRINT((ACPI_DB_OBJECTS, "can't get status of %s - %d\n",
                              acpi_name(rp->ap_resource), status));
            /* XXX is this correct?  Always switch if in doubt? */
            continue;
        } else if (rp->ap_state == ACPI_PWR_UNK)
            rp->ap_state = cur;

        /*
         * Switch if required.  Note that we ignore the result of the switch
         * effort; we don't know what to do if it fails, so checking wouldn't
         * help much.
         */
        if (rp->ap_state != ACPI_PWR_OFF) {
            status = AcpiEvaluateObject(rp->ap_resource, "_OFF", NULL, NULL);
            if (ACPI_FAILURE(status)) {
                ACPI_DEBUG_PRINT((ACPI_DB_OBJECTS,
                                 "failed to switch %s off - %s\n", 
                                 acpi_name(rp->ap_resource),
                                 AcpiFormatException(status)));
            } else {
                rp->ap_state = ACPI_PWR_OFF;
                ACPI_DEBUG_PRINT((ACPI_DB_OBJECTS, "switched %s off\n",
                                 acpi_name(rp->ap_resource)));
            }
        } else {
            ACPI_DEBUG_PRINT((ACPI_DB_OBJECTS, "%s is already off\n",
                             acpi_name(rp->ap_resource)));
        }
    }

    return_ACPI_STATUS (AE_OK);
}

/*
 * Find a power resource's control structure.
 */
static struct acpi_powerresource *
acpi_pwr_find_resource(ACPI_HANDLE res)
{
    struct acpi_powerresource   *rp;
    
    ACPI_FUNCTION_TRACE((char *)(uintptr_t)__func__);
    ACPI_SERIAL_ASSERT(powerres);

    TAILQ_FOREACH(rp, &acpi_powerresources, ap_link) {
        if (rp->ap_resource == res)
            break;
    }

    return_PTR (rp);
}

/*
 * Find a power consumer's control structure.
 */
static struct acpi_powerconsumer *
acpi_pwr_find_consumer(ACPI_HANDLE consumer)
{
    struct acpi_powerconsumer   *pc;
    
    ACPI_FUNCTION_TRACE((char *)(uintptr_t)__func__);
    ACPI_SERIAL_ASSERT(powerres);

    TAILQ_FOREACH(pc, &acpi_powerconsumers, ac_link) {
        if (pc->ac_consumer == consumer)
            break;
    }

    return_PTR (pc);
}