drivers/acpi/property.c - kernel/msm-4.9 - Gitiles

 /*
  * ACPI device specific properties support.
  *
  * Copyright (C) 2014, Intel Corporation
  * All rights reserved.
  *
  * Authors: Mika Westerberg <mika.westerberg@linux.intel.com>
  *          Darren Hart <dvhart@linux.intel.com>
  *          Rafael J. Wysocki <rafael.j.wysocki@intel.com>
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 2 as
  * published by the Free Software Foundation.
  */

 #include <linux/acpi.h>
 #include <linux/device.h>
 #include <linux/export.h>

 #include "internal.h"

 /* ACPI _DSD device properties UUID: daffd814-6eba-4d8c-8a91-bc9bbf4aa301 */
 static const u8 prp_uuid[16] = {
 	0x14, 0xd8, 0xff, 0xda, 0xba, 0x6e, 0x8c, 0x4d,
 	0x8a, 0x91, 0xbc, 0x9b, 0xbf, 0x4a, 0xa3, 0x01
 };

 static bool acpi_property_value_ok(const union acpi_object *value)
 {
 	int j;

 	/*
 	 * The value must be an integer, a string, a reference, or a package
 	 * whose every element must be an integer, a string, or a reference.
 	 */
 	switch (value->type) {
 	case ACPI_TYPE_INTEGER:
 	case ACPI_TYPE_STRING:
 	case ACPI_TYPE_LOCAL_REFERENCE:
 		return true;

 	case ACPI_TYPE_PACKAGE:
 		for (j = 0; j < value->package.count; j++)
 			switch (value->package.elements[j].type) {
 			case ACPI_TYPE_INTEGER:
 			case ACPI_TYPE_STRING:
 			case ACPI_TYPE_LOCAL_REFERENCE:
 				continue;

 			default:
 				return false;
 			}

 		return true;
 	}
 	return false;
 }

 static bool acpi_properties_format_valid(const union acpi_object *properties)
 {
 	int i;

 	for (i = 0; i < properties->package.count; i++) {
 		const union acpi_object *property;

 		property = &properties->package.elements[i];
 		/*
 		 * Only two elements allowed, the first one must be a string and
 		 * the second one has to satisfy certain conditions.
 		 */
 		if (property->package.count != 2
 		    || property->package.elements[0].type != ACPI_TYPE_STRING
 		    || !acpi_property_value_ok(&property->package.elements[1]))
 			return false;
 	}
 	return true;
 }

 static void acpi_init_of_compatible(struct acpi_device *adev)
 {
 	const union acpi_object *of_compatible;
 	struct acpi_hardware_id *hwid;
 	bool acpi_of = false;
 	int ret;

 	/*
 	 * Check if the special PRP0001 ACPI ID is present and in that
 	 * case we fill in Device Tree compatible properties for this
 	 * device.
 	 */
 	list_for_each_entry(hwid, &adev->pnp.ids, list) {
 		if (!strcmp(hwid->id, "PRP0001")) {
 			acpi_of = true;
 			break;
 		}
 	}

 	if (!acpi_of)
 		return;

 	ret = acpi_dev_get_property_array(adev, "compatible", ACPI_TYPE_STRING,
 					  &of_compatible);
 	if (ret) {
 		ret = acpi_dev_get_property(adev, "compatible",
 					    ACPI_TYPE_STRING, &of_compatible);
 		if (ret) {
 			acpi_handle_warn(adev->handle,
 					 "PRP0001 requires compatible property\n");
 			return;
 		}
 	}
 	adev->data.of_compatible = of_compatible;
 }

 void acpi_init_properties(struct acpi_device *adev)
 {
 	struct acpi_buffer buf = { ACPI_ALLOCATE_BUFFER };
 	const union acpi_object *desc;
 	acpi_status status;
 	int i;

 	status = acpi_evaluate_object_typed(adev->handle, "_DSD", NULL, &buf,
 					    ACPI_TYPE_PACKAGE);
 	if (ACPI_FAILURE(status))
 		return;

 	desc = buf.pointer;
 	if (desc->package.count % 2)
 		goto fail;

 	/* Look for the device properties UUID. */
 	for (i = 0; i < desc->package.count; i += 2) {
 		const union acpi_object *uuid, *properties;

 		uuid = &desc->package.elements[i];
 		properties = &desc->package.elements[i + 1];

 		/*
 		 * The first element must be a UUID and the second one must be
 		 * a package.
 		 */
 		if (uuid->type != ACPI_TYPE_BUFFER || uuid->buffer.length != 16
 		    || properties->type != ACPI_TYPE_PACKAGE)
 			break;

 		if (memcmp(uuid->buffer.pointer, prp_uuid, sizeof(prp_uuid)))
 			continue;

 		/*
 		 * We found the matching UUID. Now validate the format of the
 		 * package immediately following it.
 		 */
 		if (!acpi_properties_format_valid(properties))
 			break;

 		adev->data.pointer = buf.pointer;
 		adev->data.properties = properties;

 		acpi_init_of_compatible(adev);
 		return;
 	}

  fail:
 	dev_warn(&adev->dev, "Returned _DSD data is not valid, skipping\n");
 	ACPI_FREE(buf.pointer);
 }

 void acpi_free_properties(struct acpi_device *adev)
 {
 	ACPI_FREE((void *)adev->data.pointer);
 	adev->data.of_compatible = NULL;
 	adev->data.pointer = NULL;
 	adev->data.properties = NULL;
 }

 /**
  * acpi_dev_get_property - return an ACPI property with given name
  * @adev: ACPI device to get property
  * @name: Name of the property
  * @type: Expected property type
  * @obj: Location to store the property value (if not %NULL)
  *
  * Look up a property with @name and store a pointer to the resulting ACPI
  * object at the location pointed to by @obj if found.
  *
  * Callers must not attempt to free the returned objects.  These objects will be
  * freed by the ACPI core automatically during the removal of @adev.
  *
  * Return: %0 if property with @name has been found (success),
  *         %-EINVAL if the arguments are invalid,
  *         %-ENODATA if the property doesn't exist,
  *         %-EPROTO if the property value type doesn't match @type.
  */
 int acpi_dev_get_property(struct acpi_device *adev, const char *name,
 			  acpi_object_type type, const union acpi_object **obj)
 {
 	const union acpi_object *properties;
 	int i;

 	if (!adev || !name)
 		return -EINVAL;

 	if (!adev->data.pointer || !adev->data.properties)
 		return -ENODATA;

 	properties = adev->data.properties;
 	for (i = 0; i < properties->package.count; i++) {
 		const union acpi_object *propname, *propvalue;
 		const union acpi_object *property;

 		property = &properties->package.elements[i];

 		propname = &property->package.elements[0];
 		propvalue = &property->package.elements[1];

 		if (!strcmp(name, propname->string.pointer)) {
 			if (type != ACPI_TYPE_ANY && propvalue->type != type)
 				return -EPROTO;
 			else if (obj)
 				*obj = propvalue;

 			return 0;
 		}
 	}
 	return -ENODATA;
 }
 EXPORT_SYMBOL_GPL(acpi_dev_get_property);

 /**
  * acpi_dev_get_property_array - return an ACPI array property with given name
  * @adev: ACPI device to get property
  * @name: Name of the property
  * @type: Expected type of array elements
  * @obj: Location to store a pointer to the property value (if not NULL)
  *
  * Look up an array property with @name and store a pointer to the resulting
  * ACPI object at the location pointed to by @obj if found.
  *
  * Callers must not attempt to free the returned objects.  Those objects will be
  * freed by the ACPI core automatically during the removal of @adev.
  *
  * Return: %0 if array property (package) with @name has been found (success),
  *         %-EINVAL if the arguments are invalid,
  *         %-ENODATA if the property doesn't exist,
  *         %-EPROTO if the property is not a package or the type of its elements
  *           doesn't match @type.
  */
 int acpi_dev_get_property_array(struct acpi_device *adev, const char *name,
 				acpi_object_type type,
 				const union acpi_object **obj)
 {
 	const union acpi_object *prop;
 	int ret, i;

 	ret = acpi_dev_get_property(adev, name, ACPI_TYPE_PACKAGE, &prop);
 	if (ret)
 		return ret;

 	if (type != ACPI_TYPE_ANY) {
 		/* Check that all elements are of correct type. */
 		for (i = 0; i < prop->package.count; i++)
 			if (prop->package.elements[i].type != type)
 				return -EPROTO;
 	}
 	if (obj)
 		*obj = prop;

 	return 0;
 }
 EXPORT_SYMBOL_GPL(acpi_dev_get_property_array);

 /**
  * acpi_dev_get_property_reference - returns handle to the referenced object
  * @adev: ACPI device to get property
  * @name: Name of the property
  * @index: Index of the reference to return
  * @args: Location to store the returned reference with optional arguments
  *
  * Find property with @name, verifify that it is a package containing at least
  * one object reference and if so, store the ACPI device object pointer to the
  * target object in @args->adev.  If the reference includes arguments, store
  * them in the @args->args[] array.
  *
  * If there's more than one reference in the property value package, @index is
  * used to select the one to return.
  *
  * Return: %0 on success, negative error code on failure.
  */
 int acpi_dev_get_property_reference(struct acpi_device *adev,
 				    const char *name, size_t index,
 				    struct acpi_reference_args *args)
 {
 	const union acpi_object *element, *end;
 	const union acpi_object *obj;
 	struct acpi_device *device;
 	int ret, idx = 0;

 	ret = acpi_dev_get_property(adev, name, ACPI_TYPE_ANY, &obj);
 	if (ret)
 		return ret;

 	/*
 	 * The simplest case is when the value is a single reference.  Just
 	 * return that reference then.
 	 */
 	if (obj->type == ACPI_TYPE_LOCAL_REFERENCE) {
 		if (index)
 			return -EINVAL;

 		ret = acpi_bus_get_device(obj->reference.handle, &device);
 		if (ret)
 			return ret;

 		args->adev = device;
 		args->nargs = 0;
 		return 0;
 	}

 	/*
 	 * If it is not a single reference, then it is a package of
 	 * references followed by number of ints as follows:
 	 *
 	 *  Package () { REF, INT, REF, INT, INT }
 	 *
 	 * The index argument is then used to determine which reference
 	 * the caller wants (along with the arguments).
 	 */
 	if (obj->type != ACPI_TYPE_PACKAGE || index >= obj->package.count)
 		return -EPROTO;

 	element = obj->package.elements;
 	end = element + obj->package.count;

 	while (element < end) {
 		u32 nargs, i;

 		if (element->type != ACPI_TYPE_LOCAL_REFERENCE)
 			return -EPROTO;

 		ret = acpi_bus_get_device(element->reference.handle, &device);
 		if (ret)
 			return -ENODEV;

 		element++;
 		nargs = 0;

 		/* assume following integer elements are all args */
 		for (i = 0; element + i < end; i++) {
 			int type = element[i].type;

 			if (type == ACPI_TYPE_INTEGER)
 				nargs++;
 			else if (type == ACPI_TYPE_LOCAL_REFERENCE)
 				break;
 			else
 				return -EPROTO;
 		}

 		if (idx++ == index) {
 			args->adev = device;
 			args->nargs = nargs;
 			for (i = 0; i < nargs; i++)
 				args->args[i] = element[i].integer.value;

 			return 0;
 		}

 		element += nargs;
 	}

 	return -EPROTO;
 }
 EXPORT_SYMBOL_GPL(acpi_dev_get_property_reference);

 int acpi_dev_prop_get(struct acpi_device *adev, const char *propname,
 		      void **valptr)
 {
 	return acpi_dev_get_property(adev, propname, ACPI_TYPE_ANY,
 				     (const union acpi_object **)valptr);
 }

 int acpi_dev_prop_read_single(struct acpi_device *adev, const char *propname,
 			      enum dev_prop_type proptype, void *val)
 {
 	const union acpi_object *obj;
 	int ret;

 	if (!val)
 		return -EINVAL;

 	if (proptype >= DEV_PROP_U8 && proptype <= DEV_PROP_U64) {
 		ret = acpi_dev_get_property(adev, propname, ACPI_TYPE_INTEGER, &obj);
 		if (ret)
 			return ret;

 		switch (proptype) {
 		case DEV_PROP_U8:
 			if (obj->integer.value > U8_MAX)
 				return -EOVERFLOW;
 			*(u8 *)val = obj->integer.value;
 			break;
 		case DEV_PROP_U16:
 			if (obj->integer.value > U16_MAX)
 				return -EOVERFLOW;
 			*(u16 *)val = obj->integer.value;
 			break;
 		case DEV_PROP_U32:
 			if (obj->integer.value > U32_MAX)
 				return -EOVERFLOW;
 			*(u32 *)val = obj->integer.value;
 			break;
 		default:
 			*(u64 *)val = obj->integer.value;
 			break;
 		}
 	} else if (proptype == DEV_PROP_STRING) {
 		ret = acpi_dev_get_property(adev, propname, ACPI_TYPE_STRING, &obj);
 		if (ret)
 			return ret;

 		*(char **)val = obj->string.pointer;
 	} else {
 		ret = -EINVAL;
 	}
 	return ret;
 }

 static int acpi_copy_property_array_u8(const union acpi_object *items, u8 *val,
 				       size_t nval)
 {
 	int i;

 	for (i = 0; i < nval; i++) {
 		if (items[i].type != ACPI_TYPE_INTEGER)
 			return -EPROTO;
 		if (items[i].integer.value > U8_MAX)
 			return -EOVERFLOW;

 		val[i] = items[i].integer.value;
 	}
 	return 0;
 }

 static int acpi_copy_property_array_u16(const union acpi_object *items,
 					u16 *val, size_t nval)
 {
 	int i;

 	for (i = 0; i < nval; i++) {
 		if (items[i].type != ACPI_TYPE_INTEGER)
 			return -EPROTO;
 		if (items[i].integer.value > U16_MAX)
 			return -EOVERFLOW;

 		val[i] = items[i].integer.value;
 	}
 	return 0;
 }

 static int acpi_copy_property_array_u32(const union acpi_object *items,
 					u32 *val, size_t nval)
 {
 	int i;

 	for (i = 0; i < nval; i++) {
 		if (items[i].type != ACPI_TYPE_INTEGER)
 			return -EPROTO;
 		if (items[i].integer.value > U32_MAX)
 			return -EOVERFLOW;

 		val[i] = items[i].integer.value;
 	}
 	return 0;
 }

 static int acpi_copy_property_array_u64(const union acpi_object *items,
 					u64 *val, size_t nval)
 {
 	int i;

 	for (i = 0; i < nval; i++) {
 		if (items[i].type != ACPI_TYPE_INTEGER)
 			return -EPROTO;

 		val[i] = items[i].integer.value;
 	}
 	return 0;
 }

 static int acpi_copy_property_array_string(const union acpi_object *items,
 					   char **val, size_t nval)
 {
 	int i;

 	for (i = 0; i < nval; i++) {
 		if (items[i].type != ACPI_TYPE_STRING)
 			return -EPROTO;

 		val[i] = items[i].string.pointer;
 	}
 	return 0;
 }

 int acpi_dev_prop_read(struct acpi_device *adev, const char *propname,
 		       enum dev_prop_type proptype, void *val, size_t nval)
 {
 	const union acpi_object *obj;
 	const union acpi_object *items;
 	int ret;

 	if (val && nval == 1) {
 		ret = acpi_dev_prop_read_single(adev, propname, proptype, val);
 		if (!ret)
 			return ret;
 	}

 	ret = acpi_dev_get_property_array(adev, propname, ACPI_TYPE_ANY, &obj);
 	if (ret)
 		return ret;

 	if (!val)
 		return obj->package.count;
 	else if (nval <= 0)
 		return -EINVAL;

 	if (nval > obj->package.count)
 		return -EOVERFLOW;

 	items = obj->package.elements;
 	switch (proptype) {
 	case DEV_PROP_U8:
 		ret = acpi_copy_property_array_u8(items, (u8 *)val, nval);
 		break;
 	case DEV_PROP_U16:
 		ret = acpi_copy_property_array_u16(items, (u16 *)val, nval);
 		break;
 	case DEV_PROP_U32:
 		ret = acpi_copy_property_array_u32(items, (u32 *)val, nval);
 		break;
 	case DEV_PROP_U64:
 		ret = acpi_copy_property_array_u64(items, (u64 *)val, nval);
 		break;
 	case DEV_PROP_STRING:
 		ret = acpi_copy_property_array_string(items, (char **)val, nval);
 		break;
 	default:
 		ret = -EINVAL;
 		break;
 	}
 	return ret;
 }
	/*
	* ACPI device specific properties support.
	*
	* Copyright (C) 2014, Intel Corporation
	* All rights reserved.
	*
	* Authors: Mika Westerberg <mika.westerberg@linux.intel.com>
	* Darren Hart <dvhart@linux.intel.com>
	* Rafael J. Wysocki <rafael.j.wysocki@intel.com>
	*
	* This program is free software; you can redistribute it and/or modify
	* it under the terms of the GNU General Public License version 2 as
	* published by the Free Software Foundation.
	*/

	#include <linux/acpi.h>
	#include <linux/device.h>
	#include <linux/export.h>

	#include "internal.h"

	/* ACPI _DSD device properties UUID: daffd814-6eba-4d8c-8a91-bc9bbf4aa301 */
	static const u8 prp_uuid[16] = {
	0x14, 0xd8, 0xff, 0xda, 0xba, 0x6e, 0x8c, 0x4d,
	0x8a, 0x91, 0xbc, 0x9b, 0xbf, 0x4a, 0xa3, 0x01
	};

	static bool acpi_property_value_ok(const union acpi_object *value)
	{
	int j;

	/*
	* The value must be an integer, a string, a reference, or a package
	* whose every element must be an integer, a string, or a reference.
	*/
	switch (value->type) {
	case ACPI_TYPE_INTEGER:
	case ACPI_TYPE_STRING:
	case ACPI_TYPE_LOCAL_REFERENCE:
	return true;

	case ACPI_TYPE_PACKAGE:
	for (j = 0; j < value->package.count; j++)
	switch (value->package.elements[j].type) {
	case ACPI_TYPE_INTEGER:
	case ACPI_TYPE_STRING:
	case ACPI_TYPE_LOCAL_REFERENCE:
	continue;

	default:
	return false;
	}

	return true;
	}
	return false;
	}

	static bool acpi_properties_format_valid(const union acpi_object *properties)
	{
	int i;

	for (i = 0; i < properties->package.count; i++) {
	const union acpi_object *property;

	property = &properties->package.elements[i];
	/*
	* Only two elements allowed, the first one must be a string and
	* the second one has to satisfy certain conditions.
	*/
	if (property->package.count != 2
	\|\| property->package.elements[0].type != ACPI_TYPE_STRING
	\|\| !acpi_property_value_ok(&property->package.elements[1]))
	return false;
	}
	return true;
	}

	static void acpi_init_of_compatible(struct acpi_device *adev)
	{
	const union acpi_object *of_compatible;
	struct acpi_hardware_id *hwid;
	bool acpi_of = false;
	int ret;

	/*
	* Check if the special PRP0001 ACPI ID is present and in that
	* case we fill in Device Tree compatible properties for this
	* device.
	*/
	list_for_each_entry(hwid, &adev->pnp.ids, list) {
	if (!strcmp(hwid->id, "PRP0001")) {
	acpi_of = true;
	break;
	}
	}

	if (!acpi_of)
	return;

	ret = acpi_dev_get_property_array(adev, "compatible", ACPI_TYPE_STRING,
	&of_compatible);
	if (ret) {
	ret = acpi_dev_get_property(adev, "compatible",
	ACPI_TYPE_STRING, &of_compatible);
	if (ret) {
	acpi_handle_warn(adev->handle,
	"PRP0001 requires compatible property\n");
	return;
	}
	}
	adev->data.of_compatible = of_compatible;
	}

	void acpi_init_properties(struct acpi_device *adev)
	{
	struct acpi_buffer buf = { ACPI_ALLOCATE_BUFFER };
	const union acpi_object *desc;
	acpi_status status;
	int i;

	status = acpi_evaluate_object_typed(adev->handle, "_DSD", NULL, &buf,
	ACPI_TYPE_PACKAGE);
	if (ACPI_FAILURE(status))
	return;

	desc = buf.pointer;
	if (desc->package.count % 2)
	goto fail;

	/* Look for the device properties UUID. */
	for (i = 0; i < desc->package.count; i += 2) {
	const union acpi_object uuid, properties;

	uuid = &desc->package.elements[i];
	properties = &desc->package.elements[i + 1];

	/*
	* The first element must be a UUID and the second one must be
	* a package.
	*/
	if (uuid->type != ACPI_TYPE_BUFFER \|\| uuid->buffer.length != 16
	\|\| properties->type != ACPI_TYPE_PACKAGE)
	break;

	if (memcmp(uuid->buffer.pointer, prp_uuid, sizeof(prp_uuid)))
	continue;

	/*
	* We found the matching UUID. Now validate the format of the
	* package immediately following it.
	*/
	if (!acpi_properties_format_valid(properties))
	break;

	adev->data.pointer = buf.pointer;
	adev->data.properties = properties;

	acpi_init_of_compatible(adev);
	return;
	}

	fail:
	dev_warn(&adev->dev, "Returned _DSD data is not valid, skipping\n");
	ACPI_FREE(buf.pointer);
	}

	void acpi_free_properties(struct acpi_device *adev)
	{
	ACPI_FREE((void *)adev->data.pointer);
	adev->data.of_compatible = NULL;
	adev->data.pointer = NULL;
	adev->data.properties = NULL;
	}

	/**
	* acpi_dev_get_property - return an ACPI property with given name
	* @adev: ACPI device to get property
	* @name: Name of the property
	* @type: Expected property type
	* @obj: Location to store the property value (if not %NULL)
	*
	* Look up a property with @name and store a pointer to the resulting ACPI
	* object at the location pointed to by @obj if found.
	*
	* Callers must not attempt to free the returned objects. These objects will be
	* freed by the ACPI core automatically during the removal of @adev.
	*
	* Return: %0 if property with @name has been found (success),
	* %-EINVAL if the arguments are invalid,
	* %-ENODATA if the property doesn't exist,
	* %-EPROTO if the property value type doesn't match @type.
	*/
	int acpi_dev_get_property(struct acpi_device adev, const char name,
	acpi_object_type type, const union acpi_object **obj)
	{
	const union acpi_object *properties;
	int i;

	if (!adev \|\| !name)
	return -EINVAL;

	if (!adev->data.pointer \|\| !adev->data.properties)
	return -ENODATA;

	properties = adev->data.properties;
	for (i = 0; i < properties->package.count; i++) {
	const union acpi_object propname, propvalue;
	const union acpi_object *property;

	property = &properties->package.elements[i];

	propname = &property->package.elements[0];
	propvalue = &property->package.elements[1];

	if (!strcmp(name, propname->string.pointer)) {
	if (type != ACPI_TYPE_ANY && propvalue->type != type)
	return -EPROTO;
	else if (obj)
	*obj = propvalue;

	return 0;
	}
	}
	return -ENODATA;
	}
	EXPORT_SYMBOL_GPL(acpi_dev_get_property);

	/**
	* acpi_dev_get_property_array - return an ACPI array property with given name
	* @adev: ACPI device to get property
	* @name: Name of the property
	* @type: Expected type of array elements
	* @obj: Location to store a pointer to the property value (if not NULL)
	*
	* Look up an array property with @name and store a pointer to the resulting
	* ACPI object at the location pointed to by @obj if found.
	*
	* Callers must not attempt to free the returned objects. Those objects will be
	* freed by the ACPI core automatically during the removal of @adev.
	*
	* Return: %0 if array property (package) with @name has been found (success),
	* %-EINVAL if the arguments are invalid,
	* %-ENODATA if the property doesn't exist,
	* %-EPROTO if the property is not a package or the type of its elements
	* doesn't match @type.
	*/
	int acpi_dev_get_property_array(struct acpi_device adev, const char name,
	acpi_object_type type,
	const union acpi_object **obj)
	{
	const union acpi_object *prop;
	int ret, i;

	ret = acpi_dev_get_property(adev, name, ACPI_TYPE_PACKAGE, &prop);
	if (ret)
	return ret;

	if (type != ACPI_TYPE_ANY) {
	/* Check that all elements are of correct type. */
	for (i = 0; i < prop->package.count; i++)
	if (prop->package.elements[i].type != type)
	return -EPROTO;
	}
	if (obj)
	*obj = prop;

	return 0;
	}
	EXPORT_SYMBOL_GPL(acpi_dev_get_property_array);

	/**
	* acpi_dev_get_property_reference - returns handle to the referenced object
	* @adev: ACPI device to get property
	* @name: Name of the property
	* @index: Index of the reference to return
	* @args: Location to store the returned reference with optional arguments
	*
	* Find property with @name, verifify that it is a package containing at least
	* one object reference and if so, store the ACPI device object pointer to the
	* target object in @args->adev. If the reference includes arguments, store
	* them in the @args->args[] array.
	*
	* If there's more than one reference in the property value package, @index is
	* used to select the one to return.
	*
	* Return: %0 on success, negative error code on failure.
	*/
	int acpi_dev_get_property_reference(struct acpi_device *adev,
	const char *name, size_t index,
	struct acpi_reference_args *args)
	{
	const union acpi_object element, end;
	const union acpi_object *obj;
	struct acpi_device *device;
	int ret, idx = 0;

	ret = acpi_dev_get_property(adev, name, ACPI_TYPE_ANY, &obj);
	if (ret)
	return ret;

	/*
	* The simplest case is when the value is a single reference. Just
	* return that reference then.
	*/
	if (obj->type == ACPI_TYPE_LOCAL_REFERENCE) {
	if (index)
	return -EINVAL;

	ret = acpi_bus_get_device(obj->reference.handle, &device);
	if (ret)
	return ret;

	args->adev = device;
	args->nargs = 0;
	return 0;
	}

	/*
	* If it is not a single reference, then it is a package of
	* references followed by number of ints as follows:
	*
	* Package () { REF, INT, REF, INT, INT }
	*
	* The index argument is then used to determine which reference
	* the caller wants (along with the arguments).
	*/
	if (obj->type != ACPI_TYPE_PACKAGE \|\| index >= obj->package.count)
	return -EPROTO;

	element = obj->package.elements;
	end = element + obj->package.count;

	while (element < end) {
	u32 nargs, i;

	if (element->type != ACPI_TYPE_LOCAL_REFERENCE)
	return -EPROTO;

	ret = acpi_bus_get_device(element->reference.handle, &device);
	if (ret)
	return -ENODEV;

	element++;
	nargs = 0;

	/* assume following integer elements are all args */
	for (i = 0; element + i < end; i++) {
	int type = element[i].type;

	if (type == ACPI_TYPE_INTEGER)
	nargs++;
	else if (type == ACPI_TYPE_LOCAL_REFERENCE)
	break;
	else
	return -EPROTO;
	}

	if (idx++ == index) {
	args->adev = device;
	args->nargs = nargs;
	for (i = 0; i < nargs; i++)
	args->args[i] = element[i].integer.value;

	return 0;
	}

	element += nargs;
	}

	return -EPROTO;
	}
	EXPORT_SYMBOL_GPL(acpi_dev_get_property_reference);

	int acpi_dev_prop_get(struct acpi_device adev, const char propname,
	void **valptr)
	{
	return acpi_dev_get_property(adev, propname, ACPI_TYPE_ANY,
	(const union acpi_object **)valptr);
	}

	int acpi_dev_prop_read_single(struct acpi_device adev, const char propname,
	enum dev_prop_type proptype, void *val)
	{
	const union acpi_object *obj;
	int ret;

	if (!val)
	return -EINVAL;

	if (proptype >= DEV_PROP_U8 && proptype <= DEV_PROP_U64) {
	ret = acpi_dev_get_property(adev, propname, ACPI_TYPE_INTEGER, &obj);
	if (ret)
	return ret;

	switch (proptype) {
	case DEV_PROP_U8:
	if (obj->integer.value > U8_MAX)
	return -EOVERFLOW;
	(u8 )val = obj->integer.value;
	break;
	case DEV_PROP_U16:
	if (obj->integer.value > U16_MAX)
	return -EOVERFLOW;
	(u16 )val = obj->integer.value;
	break;
	case DEV_PROP_U32:
	if (obj->integer.value > U32_MAX)
	return -EOVERFLOW;
	(u32 )val = obj->integer.value;
	break;
	default:
	(u64 )val = obj->integer.value;
	break;
	}
	} else if (proptype == DEV_PROP_STRING) {
	ret = acpi_dev_get_property(adev, propname, ACPI_TYPE_STRING, &obj);
	if (ret)
	return ret;

	(char *)val = obj->string.pointer;
	} else {
	ret = -EINVAL;
	}
	return ret;
	}

	static int acpi_copy_property_array_u8(const union acpi_object items, u8 val,
	size_t nval)
	{
	int i;

	for (i = 0; i < nval; i++) {
	if (items[i].type != ACPI_TYPE_INTEGER)
	return -EPROTO;
	if (items[i].integer.value > U8_MAX)
	return -EOVERFLOW;

	val[i] = items[i].integer.value;
	}
	return 0;
	}

	static int acpi_copy_property_array_u16(const union acpi_object *items,
	u16 *val, size_t nval)
	{
	int i;

	for (i = 0; i < nval; i++) {
	if (items[i].type != ACPI_TYPE_INTEGER)
	return -EPROTO;
	if (items[i].integer.value > U16_MAX)
	return -EOVERFLOW;

	val[i] = items[i].integer.value;
	}
	return 0;
	}

	static int acpi_copy_property_array_u32(const union acpi_object *items,
	u32 *val, size_t nval)
	{
	int i;

	for (i = 0; i < nval; i++) {
	if (items[i].type != ACPI_TYPE_INTEGER)
	return -EPROTO;
	if (items[i].integer.value > U32_MAX)
	return -EOVERFLOW;

	val[i] = items[i].integer.value;
	}
	return 0;
	}

	static int acpi_copy_property_array_u64(const union acpi_object *items,
	u64 *val, size_t nval)
	{
	int i;

	for (i = 0; i < nval; i++) {
	if (items[i].type != ACPI_TYPE_INTEGER)
	return -EPROTO;

	val[i] = items[i].integer.value;
	}
	return 0;
	}

	static int acpi_copy_property_array_string(const union acpi_object *items,
	char **val, size_t nval)
	{
	int i;

	for (i = 0; i < nval; i++) {
	if (items[i].type != ACPI_TYPE_STRING)
	return -EPROTO;

	val[i] = items[i].string.pointer;
	}
	return 0;
	}

	int acpi_dev_prop_read(struct acpi_device adev, const char propname,
	enum dev_prop_type proptype, void *val, size_t nval)
	{
	const union acpi_object *obj;
	const union acpi_object *items;
	int ret;

	if (val && nval == 1) {
	ret = acpi_dev_prop_read_single(adev, propname, proptype, val);
	if (!ret)
	return ret;
	}

	ret = acpi_dev_get_property_array(adev, propname, ACPI_TYPE_ANY, &obj);
	if (ret)
	return ret;

	if (!val)
	return obj->package.count;
	else if (nval <= 0)
	return -EINVAL;

	if (nval > obj->package.count)
	return -EOVERFLOW;

	items = obj->package.elements;
	switch (proptype) {
	case DEV_PROP_U8:
	ret = acpi_copy_property_array_u8(items, (u8 *)val, nval);
	break;
	case DEV_PROP_U16:
	ret = acpi_copy_property_array_u16(items, (u16 *)val, nval);
	break;
	case DEV_PROP_U32:
	ret = acpi_copy_property_array_u32(items, (u32 *)val, nval);
	break;
	case DEV_PROP_U64:
	ret = acpi_copy_property_array_u64(items, (u64 *)val, nval);
	break;
	case DEV_PROP_STRING:
	ret = acpi_copy_property_array_string(items, (char **)val, nval);
	break;
	default:
	ret = -EINVAL;
	break;
	}
	return ret;
	}