NetBSD/sys/dev/acpi/acpi_powerres.c

/* $NetBSD: acpi_powerres.c,v 1.1 2004/05/26 17:15:17 kochi Exp $ */

/*-
 * 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 1.14 2002/10/16 17:28:52 jhb Exp $
 */

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: acpi_powerres.c,v 1.1 2004/05/26 17:15:17 kochi Exp $");

#include <sys/param.h>
#include <sys/kernel.h>
#include <sys/proc.h>
#include <sys/malloc.h>
#include <sys/conf.h>
#include <sys/systm.h>

#include <dev/acpi/acpica.h>
#include <dev/acpi/acpireg.h>
#include <dev/acpi/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.
 *
 * XXX locking
 */

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

/*
 * Hooks for the ACPI CA debugging infrastructure
 */
#define _COMPONENT	ACPI_BUS_COMPONENT
ACPI_MODULE_NAME("POWERRES")

/*
 * 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 {
	ACPI_HANDLE		ac_consumer; /* device which is powered */
	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; /* the resource's handle */
	ACPI_INTEGER	ap_systemlevel;
	ACPI_INTEGER	ap_order;
};

static TAILQ_HEAD(acpi_powerresource_list, acpi_powerresource)
	acpi_powerresources = TAILQ_HEAD_INITIALIZER(acpi_powerresources);
static TAILQ_HEAD(acpi_powerconsumer_list, acpi_powerconsumer)
	acpi_powerconsumers = TAILQ_HEAD_INITIALIZER(acpi_powerconsumers);

static ACPI_STATUS	acpi_pwr_register_consumer(ACPI_HANDLE consumer);
#if 0
static ACPI_STATUS	acpi_pwr_register_resource(ACPI_HANDLE res);
static ACPI_STATUS	acpi_pwr_deregister_consumer(ACPI_HANDLE consumer);
static ACPI_STATUS	acpi_pwr_deregister_resource(ACPI_HANDLE res);
#endif
static ACPI_STATUS	acpi_pwr_reference_resource(ACPI_OBJECT *obj, void *arg);
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);

/*
 * 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(__FUNCTION__);

	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 = malloc(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;
	status = AcpiEvaluateObject(res, NULL, NULL, &buf);
	if (ACPI_FAILURE(status)) {
		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;

	/* 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))
		free(rp, M_ACPIPWR);
	return_ACPI_STATUS(status);
}

#if 0
/*
 * Deregister a power resource.
 */
static ACPI_STATUS
acpi_pwr_deregister_resource(ACPI_HANDLE res)
{
	struct acpi_powerresource	*rp;

	ACPI_FUNCTION_TRACE(__FUNCTION__);

	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 free it */
	TAILQ_REMOVE(&acpi_powerresources, rp, ap_link);
	free(rp, M_ACPIPWR);

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

	return_ACPI_STATUS(AE_OK);
}
#endif

/*
 * 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(__FUNCTION__);

	/* check to see whether we know about this consumer already */
	if ((pc = acpi_pwr_find_consumer(consumer)) != NULL)
		return_ACPI_STATUS(AE_OK);

	/* allocate a new power consumer */
	if ((pc = malloc(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);
}

#if 0
/*
 * 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(__FUNCTION__);

	/* 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 free it */
	TAILQ_REMOVE(&acpi_powerconsumers, pc, ac_link);

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

	return_ACPI_STATUS(AE_OK);
}
#endif

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

	ACPI_FUNCTION_TRACE(__FUNCTION__);

	/* find the consumer */
	if ((pc = acpi_pwr_find_consumer(consumer)) == NULL) {
		status = acpi_pwr_register_consumer(consumer);
		if (ACPI_FAILURE(status))
			return_ACPI_STATUS(status);
		if ((pc = acpi_pwr_find_consumer(consumer)) == NULL) {
			return_ACPI_STATUS(AE_ERROR);	/* something very wrong */
		}
	}

	/* check for valid transitions */
	if ((pc->ac_state == ACPI_STATE_D3) && (state != ACPI_STATE_D0))
		return_ACPI_STATUS(AE_BAD_PARAMETER);	/* can only go to D0 from D3 */

	/* 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:
		return_ACPI_STATUS(AE_BAD_PARAMETER);
	}
	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.
	 */
	reslist_buffer.Pointer = NULL;
	reslist_object = NULL;
	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;
			return_ACPI_STATUS(AE_OK);
		}
		if (state != ACPI_STATE_D3) {
			goto bad;
		}

		/* turn off the resources listed in _PR0 to go to D3. */
		if (ACPI_FAILURE(AcpiGetHandle(consumer, "_PR0", &pr0_handle))) {
			goto bad;
		}
		reslist_buffer.Length = ACPI_ALLOCATE_BUFFER;
		status = AcpiEvaluateObject(pr0_handle, NULL, NULL, &reslist_buffer);
		if (ACPI_FAILURE(status))
			goto bad;
		reslist_object = (ACPI_OBJECT *)reslist_buffer.Pointer;
		if ((reslist_object->Type != ACPI_TYPE_PACKAGE) ||
		    (reslist_object->Package.Count == 0)) {
			goto bad;
		}
		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.
	 */
	res_changed = 0;
	while((pr = TAILQ_FIRST(&pc->ac_references)) != NULL) {
		res_changed = 1;
		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);
		free(pr, M_ACPIPWR);
	}

	/*
	 * 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_foreach_package_object(reslist_object,
		    acpi_pwr_reference_resource, pc);
		res_changed = 1;
	}

	/*
	 * If we changed anything in the resource list, we need to run a switch
	 * pass now.
	 */
	status = acpi_pwr_switch_power();
	if (ACPI_FAILURE(status)) {
		ACPI_DEBUG_PRINT((ACPI_DB_OBJECTS, "failed to correctly switch resources to move %s to D%d\n",
				     acpi_name(consumer), state));
		goto out;		/* XXX is this appropriate?  Should we return to previous state? */
	}

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

	/* transition was successful */
	pc->ac_state = state;
	return_ACPI_STATUS(AE_OK);

 bad:
	ACPI_DEBUG_PRINT((ACPI_DB_OBJECTS,
			     "attempt to set unsupported state D%d\n",
			     state));
	status = AE_BAD_PARAMETER;

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

/*
 * Called to create a reference between a power consumer and a power resource
 * identified in the object.
 */
static ACPI_STATUS
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(__FUNCTION__);

	/* check the object type */
	switch (obj->Type) {
	case ACPI_TYPE_ANY:
		ACPI_DEBUG_PRINT((ACPI_DB_OBJECTS, "building reference from %s to %s\n",
				     acpi_name(pc->ac_consumer), acpi_name(obj->Reference.Handle)));

		res = obj->Reference.Handle;
		break;

	case ACPI_TYPE_STRING:
		ACPI_DEBUG_PRINT((ACPI_DB_OBJECTS,
				     "building reference from %s to %s\n",
				     acpi_name(pc->ac_consumer),
				     obj->String.Pointer));

		/* get the handle of the resource */
		status = AcpiGetHandle(NULL, obj->String.Pointer, &res);
		if (ACPI_FAILURE(status)) {
			ACPI_DEBUG_PRINT((ACPI_DB_OBJECTS,
					     "couldn't find power resource %s\n",
					     obj->String.Pointer));
			return_ACPI_STATUS(AE_OK);
		}
		break;

	default:
		ACPI_DEBUG_PRINT((ACPI_DB_OBJECTS,
				     "don't know how to create a power reference to object type %d\n",
				     obj->Type));
		return_ACPI_STATUS(AE_OK);
	}

	/* create/look up the resource */
	status = acpi_pwr_register_resource(res);
	if (ACPI_FAILURE(status)) {
		ACPI_DEBUG_PRINT((ACPI_DB_OBJECTS,
				     "couldn't register power resource %s - %s\n",
				     obj->String.Pointer,
				     AcpiFormatException(status)));
		return_ACPI_STATUS(AE_OK);
	}
	if ((rp = acpi_pwr_find_resource(res)) == NULL) {
		ACPI_DEBUG_PRINT((ACPI_DB_OBJECTS,
				     "power resource list corrupted\n"));
		return_ACPI_STATUS(AE_OK);
	}
	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 = malloc(sizeof(*pr), M_ACPIPWR, M_NOWAIT | M_ZERO)) == NULL) {
		ACPI_DEBUG_PRINT((ACPI_DB_OBJECTS, "couldn't allocate memory for a power consumer reference\n"));
		return_ACPI_STATUS(AE_OK);
	}
	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_ACPI_STATUS(AE_OK);
}


/*
 * 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;
	ACPI_INTEGER			cur;

	ACPI_FUNCTION_TRACE(__FUNCTION__);

	/*
	 * 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_eval_integer(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;
		}

		/*
		 * 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 (cur != ACPI_STA_POW_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 {
				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_eval_integer(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));
			continue;	/* XXX is this correct?  Always switch if in doubt? */
		}

		/*
		 * 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 (cur != ACPI_STA_POW_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 {
				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(__FUNCTION__);

	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(__FUNCTION__);

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