/*******************************************************************************
 *
 * Module Name: nsxfeval - Public interfaces to the ACPI subsystem
 *                         ACPI Object evaluation interfaces
 *
 ******************************************************************************/

/*
 * Copyright (C) 2000 - 2013, Intel Corp.
 * 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,
 *    without modification.
 * 2. Redistributions in binary form must reproduce at minimum a disclaimer
 *    substantially similar to the "NO WARRANTY" disclaimer below
 *    ("Disclaimer") and any redistribution must be conditioned upon
 *    including a substantially similar Disclaimer requirement for further
 *    binary redistribution.
 * 3. Neither the names of the above-listed copyright holders nor the names
 *    of any contributors may be used to endorse or promote products derived
 *    from this software without specific prior written permission.
 *
 * Alternatively, this software may be distributed under the terms of the
 * GNU General Public License ("GPL") version 2 as published by the Free
 * Software Foundation.
 *
 * NO WARRANTY
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * HOLDERS OR CONTRIBUTORS BE LIABLE FOR 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 DAMAGES.
 */

#define EXPORT_ACPI_INTERFACES

#include <acpi/acpi.h>
#include "accommon.h"
#include "acnamesp.h"
#include "acinterp.h"

#define _COMPONENT          ACPI_NAMESPACE
ACPI_MODULE_NAME("nsxfeval")

/* Local prototypes */
static void acpi_ns_resolve_references(struct acpi_evaluate_info *info);

/*******************************************************************************
 *
 * FUNCTION:    acpi_evaluate_object_typed
 *
 * PARAMETERS:  handle              - Object handle (optional)
 *              pathname            - Object pathname (optional)
 *              external_params     - List of parameters to pass to method,
 *                                    terminated by NULL. May be NULL
 *                                    if no parameters are being passed.
 *              return_buffer       - Where to put method's return value (if
 *                                    any). If NULL, no value is returned.
 *              return_type         - Expected type of return object
 *
 * RETURN:      Status
 *
 * DESCRIPTION: Find and evaluate the given object, passing the given
 *              parameters if necessary. One of "Handle" or "Pathname" must
 *              be valid (non-null)
 *
 ******************************************************************************/

acpi_status
acpi_evaluate_object_typed(acpi_handle handle,
                           acpi_string pathname,
                           struct acpi_object_list *external_params,
                           struct acpi_buffer *return_buffer,
                           acpi_object_type return_type)
{
        acpi_status status;
        u8 free_buffer_on_error = FALSE;

        ACPI_FUNCTION_TRACE(acpi_evaluate_object_typed);

        /* Return buffer must be valid */

        if (!return_buffer) {
                return_ACPI_STATUS(AE_BAD_PARAMETER);
        }

        if (return_buffer->length == ACPI_ALLOCATE_BUFFER) {
                free_buffer_on_error = TRUE;
        }

        /* Evaluate the object */

        status = acpi_evaluate_object(handle, pathname,
                                      external_params, return_buffer);
        if (ACPI_FAILURE(status)) {
                return_ACPI_STATUS(status);
        }

        /* Type ANY means "don't care" */

        if (return_type == ACPI_TYPE_ANY) {
                return_ACPI_STATUS(AE_OK);
        }

        if (return_buffer->length == 0) {

                /* Error because caller specifically asked for a return value */

                ACPI_ERROR((AE_INFO, "No return value"));
                return_ACPI_STATUS(AE_NULL_OBJECT);
        }

        /* Examine the object type returned from evaluate_object */

        if (((union acpi_object *)return_buffer->pointer)->type == return_type) {
                return_ACPI_STATUS(AE_OK);
        }

        /* Return object type does not match requested type */

        ACPI_ERROR((AE_INFO,
                    "Incorrect return type [%s] requested [%s]",
                    acpi_ut_get_type_name(((union acpi_object *)return_buffer->
                                           pointer)->type),
                    acpi_ut_get_type_name(return_type)));

        if (free_buffer_on_error) {
                /*
                 * Free a buffer created via ACPI_ALLOCATE_BUFFER.
                 * Note: We use acpi_os_free here because acpi_os_allocate was used
                 * to allocate the buffer. This purposefully bypasses the
                 * (optionally enabled) allocation tracking mechanism since we
                 * only want to track internal allocations.
                 */
                acpi_os_free(return_buffer->pointer);
                return_buffer->pointer = NULL;
        }

        return_buffer->length = 0;
        return_ACPI_STATUS(AE_TYPE);
}

ACPI_EXPORT_SYMBOL(acpi_evaluate_object_typed)

/*******************************************************************************
 *
 * FUNCTION:    acpi_evaluate_object
 *
 * PARAMETERS:  handle              - Object handle (optional)
 *              pathname            - Object pathname (optional)
 *              external_params     - List of parameters to pass to method,
 *                                    terminated by NULL. May be NULL
 *                                    if no parameters are being passed.
 *              return_buffer       - Where to put method's return value (if
 *                                    any). If NULL, no value is returned.
 *
 * RETURN:      Status
 *
 * DESCRIPTION: Find and evaluate the given object, passing the given
 *              parameters if necessary. One of "Handle" or "Pathname" must
 *              be valid (non-null)
 *
 ******************************************************************************/
acpi_status
acpi_evaluate_object(acpi_handle handle,
                     acpi_string pathname,
                     struct acpi_object_list *external_params,
                     struct acpi_buffer *return_buffer)
{
        acpi_status status;
        struct acpi_evaluate_info *info;
        acpi_size buffer_space_needed;
        u32 i;

        ACPI_FUNCTION_TRACE(acpi_evaluate_object);

        /* Allocate and initialize the evaluation information block */

        info = ACPI_ALLOCATE_ZEROED(sizeof(struct acpi_evaluate_info));
        if (!info) {
                return_ACPI_STATUS(AE_NO_MEMORY);
        }

        /* Convert and validate the device handle */

        info->prefix_node = acpi_ns_validate_handle(handle);
        if (!info->prefix_node) {
                status = AE_BAD_PARAMETER;
                goto cleanup;
        }

        /*
         * Get the actual namespace node for the target object.
         * Handles these cases:
         *
         * 1) Null node, valid pathname from root (absolute path)
         * 2) Node and valid pathname (path relative to Node)
         * 3) Node, Null pathname
         */
        if ((pathname) && (ACPI_IS_ROOT_PREFIX(pathname[0]))) {

                /* The path is fully qualified, just evaluate by name */

                info->prefix_node = NULL;
        } else if (!handle) {
                /*
                 * A handle is optional iff a fully qualified pathname is specified.
                 * Since we've already handled fully qualified names above, this is
                 * an error.
                 */
                if (!pathname) {
                        ACPI_DEBUG_PRINT((ACPI_DB_INFO,
                                          "Both Handle and Pathname are NULL"));
                } else {
                        ACPI_DEBUG_PRINT((ACPI_DB_INFO,
                                          "Null Handle with relative pathname [%s]",
                                          pathname));
                }

                status = AE_BAD_PARAMETER;
                goto cleanup;
        }

        info->relative_pathname = pathname;

        /*
         * Convert all external objects passed as arguments to the
         * internal version(s).
         */
        if (external_params && external_params->count) {
                info->param_count = (u16)external_params->count;

                /* Warn on impossible argument count */

                if (info->param_count > ACPI_METHOD_NUM_ARGS) {
                        ACPI_WARN_PREDEFINED((AE_INFO, pathname,
                                              ACPI_WARN_ALWAYS,
                                              "Excess arguments (%u) - using only %u",
                                              info->param_count,
                                              ACPI_METHOD_NUM_ARGS));

                        info->param_count = ACPI_METHOD_NUM_ARGS;
                }

                /*
                 * Allocate a new parameter block for the internal objects
                 * Add 1 to count to allow for null terminated internal list
                 */
                info->parameters = ACPI_ALLOCATE_ZEROED(((acpi_size) info->
                                                         param_count +
                                                         1) * sizeof(void *));
                if (!info->parameters) {
                        status = AE_NO_MEMORY;
                        goto cleanup;
                }

                /* Convert each external object in the list to an internal object */

                for (i = 0; i < info->param_count; i++) {
                        status =
                            acpi_ut_copy_eobject_to_iobject(&external_params->
                                                            pointer[i],
                                                            &info->
                                                            parameters[i]);
                        if (ACPI_FAILURE(status)) {
                                goto cleanup;
                        }
                }

                info->parameters[info->param_count] = NULL;
        }

#if 0

        /*
         * Begin incoming argument count analysis. Check for too few args
         * and too many args.
         */

        switch (acpi_ns_get_type(info->node)) {
        case ACPI_TYPE_METHOD:

                /* Check incoming argument count against the method definition */

                if (info->obj_desc->method.param_count > info->param_count) {
                        ACPI_ERROR((AE_INFO,
                                    "Insufficient arguments (%u) - %u are required",
                                    info->param_count,
                                    info->obj_desc->method.param_count));

                        status = AE_MISSING_ARGUMENTS;
                        goto cleanup;
                }

                else if (info->obj_desc->method.param_count < info->param_count) {
                        ACPI_WARNING((AE_INFO,
                                      "Excess arguments (%u) - only %u are required",
                                      info->param_count,
                                      info->obj_desc->method.param_count));

                        /* Just pass the required number of arguments */

                        info->param_count = info->obj_desc->method.param_count;
                }

                /*
                 * Any incoming external objects to be passed as arguments to the
                 * method must be converted to internal objects
                 */
                if (info->param_count) {
                        /*
                         * Allocate a new parameter block for the internal objects
                         * Add 1 to count to allow for null terminated internal list
                         */
                        info->parameters = ACPI_ALLOCATE_ZEROED(((acpi_size)
                                                                 info->
                                                                 param_count +
                                                                 1) *
                                                                sizeof(void *));
                        if (!info->parameters) {
                                status = AE_NO_MEMORY;
                                goto cleanup;
                        }

                        /* Convert each external object in the list to an internal object */

                        for (i = 0; i < info->param_count; i++) {
                                status =
                                    acpi_ut_copy_eobject_to_iobject
                                    (&external_params->pointer[i],
                                     &info->parameters[i]);
                                if (ACPI_FAILURE(status)) {
                                        goto cleanup;
                                }
                        }

                        info->parameters[info->param_count] = NULL;
                }
                break;

        default:

                /* Warn if arguments passed to an object that is not a method */

                if (info->param_count) {
                        ACPI_WARNING((AE_INFO,
                                      "%u arguments were passed to a non-method ACPI object",
                                      info->param_count));
                }
                break;
        }

#endif

        /* Now we can evaluate the object */

        status = acpi_ns_evaluate(info);

        /*
         * If we are expecting a return value, and all went well above,
         * copy the return value to an external object.
         */
        if (return_buffer) {
                if (!info->return_object) {
                        return_buffer->length = 0;
                } else {
                        if (ACPI_GET_DESCRIPTOR_TYPE(info->return_object) ==
                            ACPI_DESC_TYPE_NAMED) {
                                /*
                                 * If we received a NS Node as a return object, this means that
                                 * the object we are evaluating has nothing interesting to
                                 * return (such as a mutex, etc.)  We return an error because
                                 * these types are essentially unsupported by this interface.
                                 * We don't check up front because this makes it easier to add
                                 * support for various types at a later date if necessary.
                                 */
                                status = AE_TYPE;
                                info->return_object = NULL;     /* No need to delete a NS Node */
                                return_buffer->length = 0;
                        }

                        if (ACPI_SUCCESS(status)) {

                                /* Dereference Index and ref_of references */

                                acpi_ns_resolve_references(info);

                                /* Get the size of the returned object */

                                status =
                                    acpi_ut_get_object_size(info->return_object,
                                                            &buffer_space_needed);
                                if (ACPI_SUCCESS(status)) {

                                        /* Validate/Allocate/Clear caller buffer */

                                        status =
                                            acpi_ut_initialize_buffer
                                            (return_buffer,
                                             buffer_space_needed);
                                        if (ACPI_FAILURE(status)) {
                                                /*
                                                 * Caller's buffer is too small or a new one can't
                                                 * be allocated
                                                 */
                                                ACPI_DEBUG_PRINT((ACPI_DB_INFO,
                                                                  "Needed buffer size %X, %s\n",
                                                                  (u32)
                                                                  buffer_space_needed,
                                                                  acpi_format_exception
                                                                  (status)));
                                        } else {
                                                /* We have enough space for the object, build it */

                                                status =
                                                    acpi_ut_copy_iobject_to_eobject
                                                    (info->return_object,
                                                     return_buffer);
                                        }
                                }
                        }
                }
        }

        if (info->return_object) {
                /*
                 * Delete the internal return object. NOTE: Interpreter must be
                 * locked to avoid race condition.
                 */
                acpi_ex_enter_interpreter();

                /* Remove one reference on the return object (should delete it) */

                acpi_ut_remove_reference(info->return_object);
                acpi_ex_exit_interpreter();
        }

cleanup:

        /* Free the input parameter list (if we created one) */

        if (info->parameters) {

                /* Free the allocated parameter block */

                acpi_ut_delete_internal_object_list(info->parameters);
        }

        ACPI_FREE(info);
        return_ACPI_STATUS(status);
}

ACPI_EXPORT_SYMBOL(acpi_evaluate_object)

/*******************************************************************************
 *
 * FUNCTION:    acpi_ns_resolve_references
 *
 * PARAMETERS:  info                    - Evaluation info block
 *
 * RETURN:      Info->return_object is replaced with the dereferenced object
 *
 * DESCRIPTION: Dereference certain reference objects. Called before an
 *              internal return object is converted to an external union acpi_object.
 *
 * Performs an automatic dereference of Index and ref_of reference objects.
 * These reference objects are not supported by the union acpi_object, so this is a
 * last resort effort to return something useful. Also, provides compatibility
 * with other ACPI implementations.
 *
 * NOTE: does not handle references within returned package objects or nested
 * references, but this support could be added later if found to be necessary.
 *
 ******************************************************************************/
static void acpi_ns_resolve_references(struct acpi_evaluate_info *info)
{
        union acpi_operand_object *obj_desc = NULL;
        struct acpi_namespace_node *node;

        /* We are interested in reference objects only */

        if ((info->return_object)->common.type != ACPI_TYPE_LOCAL_REFERENCE) {
                return;
        }

        /*
         * Two types of references are supported - those created by Index and
         * ref_of operators. A name reference (AML_NAMEPATH_OP) can be converted
         * to an union acpi_object, so it is not dereferenced here. A ddb_handle
         * (AML_LOAD_OP) cannot be dereferenced, nor can it be converted to
         * an union acpi_object.
         */
        switch (info->return_object->reference.class) {
        case ACPI_REFCLASS_INDEX:

                obj_desc = *(info->return_object->reference.where);
                break;

        case ACPI_REFCLASS_REFOF:

                node = info->return_object->reference.object;
                if (node) {
                        obj_desc = node->object;
                }
                break;

        default:

                return;
        }

        /* Replace the existing reference object */

        if (obj_desc) {
                acpi_ut_add_reference(obj_desc);
                acpi_ut_remove_reference(info->return_object);
                info->return_object = obj_desc;
        }

        return;
}

/*******************************************************************************
 *
 * FUNCTION:    acpi_walk_namespace
 *
 * PARAMETERS:  type                - acpi_object_type to search for
 *              start_object        - Handle in namespace where search begins
 *              max_depth           - Depth to which search is to reach
 *              descending_callback - Called during tree descent
 *                                    when an object of "Type" is found
 *              ascending_callback  - Called during tree ascent
 *                                    when an object of "Type" is found
 *              context             - Passed to user function(s) above
 *              return_value        - Location where return value of
 *                                    user_function is put if terminated early
 *
 * RETURNS      Return value from the user_function if terminated early.
 *              Otherwise, returns NULL.
 *
 * DESCRIPTION: Performs a modified depth-first walk of the namespace tree,
 *              starting (and ending) at the object specified by start_handle.
 *              The callback function is called whenever an object that matches
 *              the type parameter is found. If the callback function returns
 *              a non-zero value, the search is terminated immediately and this
 *              value is returned to the caller.
 *
 *              The point of this procedure is to provide a generic namespace
 *              walk routine that can be called from multiple places to
 *              provide multiple services; the callback function(s) can be
 *              tailored to each task, whether it is a print function,
 *              a compare function, etc.
 *
 ******************************************************************************/

acpi_status
acpi_walk_namespace(acpi_object_type type,
                    acpi_handle start_object,
                    u32 max_depth,
                    acpi_walk_callback descending_callback,
                    acpi_walk_callback ascending_callback,
                    void *context, void **return_value)
{
        acpi_status status;

        ACPI_FUNCTION_TRACE(acpi_walk_namespace);

        /* Parameter validation */

        if ((type > ACPI_TYPE_LOCAL_MAX) ||
            (!max_depth) || (!descending_callback && !ascending_callback)) {
                return_ACPI_STATUS(AE_BAD_PARAMETER);
        }

        /*
         * Need to acquire the namespace reader lock to prevent interference
         * with any concurrent table unloads (which causes the deletion of
         * namespace objects). We cannot allow the deletion of a namespace node
         * while the user function is using it. The exception to this are the
         * nodes created and deleted during control method execution -- these
         * nodes are marked as temporary nodes and are ignored by the namespace
         * walk. Thus, control methods can be executed while holding the
         * namespace deletion lock (and the user function can execute control
         * methods.)
         */
        status = acpi_ut_acquire_read_lock(&acpi_gbl_namespace_rw_lock);
        if (ACPI_FAILURE(status)) {
                return_ACPI_STATUS(status);
        }

        /*
         * Lock the namespace around the walk. The namespace will be
         * unlocked/locked around each call to the user function - since the user
         * function must be allowed to make ACPICA calls itself (for example, it
         * will typically execute control methods during device enumeration.)
         */
        status = acpi_ut_acquire_mutex(ACPI_MTX_NAMESPACE);
        if (ACPI_FAILURE(status)) {
                goto unlock_and_exit;
        }

        /* Now we can validate the starting node */

        if (!acpi_ns_validate_handle(start_object)) {
                status = AE_BAD_PARAMETER;
                goto unlock_and_exit2;
        }

        status = acpi_ns_walk_namespace(type, start_object, max_depth,
                                        ACPI_NS_WALK_UNLOCK,
                                        descending_callback, ascending_callback,
                                        context, return_value);

unlock_and_exit2:
        (void)acpi_ut_release_mutex(ACPI_MTX_NAMESPACE);

unlock_and_exit:
        (void)acpi_ut_release_read_lock(&acpi_gbl_namespace_rw_lock);
        return_ACPI_STATUS(status);
}

ACPI_EXPORT_SYMBOL(acpi_walk_namespace)

/*******************************************************************************
 *
 * FUNCTION:    acpi_ns_get_device_callback
 *
 * PARAMETERS:  Callback from acpi_get_device
 *
 * RETURN:      Status
 *
 * DESCRIPTION: Takes callbacks from walk_namespace and filters out all non-
 *              present devices, or if they specified a HID, it filters based
 *              on that.
 *
 ******************************************************************************/
static acpi_status
acpi_ns_get_device_callback(acpi_handle obj_handle,
                            u32 nesting_level,
                            void *context, void **return_value)
{
        struct acpi_get_devices_info *info = context;
        acpi_status status;
        struct acpi_namespace_node *node;
        u32 flags;
        struct acpi_pnp_device_id *hid;
        struct acpi_pnp_device_id_list *cid;
        u32 i;
        u8 found;
        int no_match;

        status = acpi_ut_acquire_mutex(ACPI_MTX_NAMESPACE);
        if (ACPI_FAILURE(status)) {
                return (status);
        }

        node = acpi_ns_validate_handle(obj_handle);
        status = acpi_ut_release_mutex(ACPI_MTX_NAMESPACE);
        if (ACPI_FAILURE(status)) {
                return (status);
        }

        if (!node) {
                return (AE_BAD_PARAMETER);
        }

        /*
         * First, filter based on the device HID and CID.
         *
         * 01/2010: For this case where a specific HID is requested, we don't
         * want to run _STA until we have an actual HID match. Thus, we will
         * not unnecessarily execute _STA on devices for which the caller
         * doesn't care about. Previously, _STA was executed unconditionally
         * on all devices found here.
         *
         * A side-effect of this change is that now we will continue to search
         * for a matching HID even under device trees where the parent device
         * would have returned a _STA that indicates it is not present or
         * not functioning (thus aborting the search on that branch).
         */
        if (info->hid != NULL) {
                status = acpi_ut_execute_HID(node, &hid);
                if (status == AE_NOT_FOUND) {
                        return (AE_OK);
                } else if (ACPI_FAILURE(status)) {
                        return (AE_CTRL_DEPTH);
                }

                no_match = ACPI_STRCMP(hid->string, info->hid);
                ACPI_FREE(hid);

                if (no_match) {
                        /*
                         * HID does not match, attempt match within the
                         * list of Compatible IDs (CIDs)
                         */
                        status = acpi_ut_execute_CID(node, &cid);
                        if (status == AE_NOT_FOUND) {
                                return (AE_OK);
                        } else if (ACPI_FAILURE(status)) {
                                return (AE_CTRL_DEPTH);
                        }

                        /* Walk the CID list */

                        found = FALSE;
                        for (i = 0; i < cid->count; i++) {
                                if (ACPI_STRCMP(cid->ids[i].string, info->hid)
                                    == 0) {

                                        /* Found a matching CID */

                                        found = TRUE;
                                        break;
                                }
                        }

                        ACPI_FREE(cid);
                        if (!found) {
                                return (AE_OK);
                        }
                }
        }

        /* Run _STA to determine if device is present */

        status = acpi_ut_execute_STA(node, &flags);
        if (ACPI_FAILURE(status)) {
                return (AE_CTRL_DEPTH);
        }

        if (!(flags & ACPI_STA_DEVICE_PRESENT) &&
            !(flags & ACPI_STA_DEVICE_FUNCTIONING)) {
                /*
                 * Don't examine the children of the device only when the
                 * device is neither present nor functional. See ACPI spec,
                 * description of _STA for more information.
                 */
                return (AE_CTRL_DEPTH);
        }

        /* We have a valid device, invoke the user function */

        status = info->user_function(obj_handle, nesting_level, info->context,
                                     return_value);
        return (status);
}

/*******************************************************************************
 *
 * FUNCTION:    acpi_get_devices
 *
 * PARAMETERS:  HID                 - HID to search for. Can be NULL.
 *              user_function       - Called when a matching object is found
 *              context             - Passed to user function
 *              return_value        - Location where return value of
 *                                    user_function is put if terminated early
 *
 * RETURNS      Return value from the user_function if terminated early.
 *              Otherwise, returns NULL.
 *
 * DESCRIPTION: Performs a modified depth-first walk of the namespace tree,
 *              starting (and ending) at the object specified by start_handle.
 *              The user_function is called whenever an object of type
 *              Device is found. If the user function returns
 *              a non-zero value, the search is terminated immediately and this
 *              value is returned to the caller.
 *
 *              This is a wrapper for walk_namespace, but the callback performs
 *              additional filtering. Please see acpi_ns_get_device_callback.
 *
 ******************************************************************************/

acpi_status
acpi_get_devices(const char *HID,
                 acpi_walk_callback user_function,
                 void *context, void **return_value)
{
        acpi_status status;
        struct acpi_get_devices_info info;

        ACPI_FUNCTION_TRACE(acpi_get_devices);

        /* Parameter validation */

        if (!user_function) {
                return_ACPI_STATUS(AE_BAD_PARAMETER);
        }

        /*
         * We're going to call their callback from OUR callback, so we need
         * to know what it is, and their context parameter.
         */
        info.hid = HID;
        info.context = context;
        info.user_function = user_function;

        /*
         * Lock the namespace around the walk.
         * The namespace will be unlocked/locked around each call
         * to the user function - since this function
         * must be allowed to make Acpi calls itself.
         */
        status = acpi_ut_acquire_mutex(ACPI_MTX_NAMESPACE);
        if (ACPI_FAILURE(status)) {
                return_ACPI_STATUS(status);
        }

        status = acpi_ns_walk_namespace(ACPI_TYPE_DEVICE, ACPI_ROOT_OBJECT,
                                        ACPI_UINT32_MAX, ACPI_NS_WALK_UNLOCK,
                                        acpi_ns_get_device_callback, NULL,
                                        &info, return_value);

        (void)acpi_ut_release_mutex(ACPI_MTX_NAMESPACE);
        return_ACPI_STATUS(status);
}

ACPI_EXPORT_SYMBOL(acpi_get_devices)

/*******************************************************************************
 *
 * FUNCTION:    acpi_attach_data
 *
 * PARAMETERS:  obj_handle          - Namespace node
 *              handler             - Handler for this attachment
 *              data                - Pointer to data to be attached
 *
 * RETURN:      Status
 *
 * DESCRIPTION: Attach arbitrary data and handler to a namespace node.
 *
 ******************************************************************************/
acpi_status
acpi_attach_data(acpi_handle obj_handle,
                 acpi_object_handler handler, void *data)
{
        struct acpi_namespace_node *node;
        acpi_status status;

        /* Parameter validation */

        if (!obj_handle || !handler || !data) {
                return (AE_BAD_PARAMETER);
        }

        status = acpi_ut_acquire_mutex(ACPI_MTX_NAMESPACE);
        if (ACPI_FAILURE(status)) {
                return (status);
        }

        /* Convert and validate the handle */

        node = acpi_ns_validate_handle(obj_handle);
        if (!node) {
                status = AE_BAD_PARAMETER;
                goto unlock_and_exit;
        }

        status = acpi_ns_attach_data(node, handler, data);

unlock_and_exit:
        (void)acpi_ut_release_mutex(ACPI_MTX_NAMESPACE);
        return (status);
}

ACPI_EXPORT_SYMBOL(acpi_attach_data)

/*******************************************************************************
 *
 * FUNCTION:    acpi_detach_data
 *
 * PARAMETERS:  obj_handle          - Namespace node handle
 *              handler             - Handler used in call to acpi_attach_data
 *
 * RETURN:      Status
 *
 * DESCRIPTION: Remove data that was previously attached to a node.
 *
 ******************************************************************************/
acpi_status
acpi_detach_data(acpi_handle obj_handle, acpi_object_handler handler)
{
        struct acpi_namespace_node *node;
        acpi_status status;

        /* Parameter validation */

        if (!obj_handle || !handler) {
                return (AE_BAD_PARAMETER);
        }

        status = acpi_ut_acquire_mutex(ACPI_MTX_NAMESPACE);
        if (ACPI_FAILURE(status)) {
                return (status);
        }

        /* Convert and validate the handle */

        node = acpi_ns_validate_handle(obj_handle);
        if (!node) {
                status = AE_BAD_PARAMETER;
                goto unlock_and_exit;
        }

        status = acpi_ns_detach_data(node, handler);

unlock_and_exit:
        (void)acpi_ut_release_mutex(ACPI_MTX_NAMESPACE);
        return (status);
}

ACPI_EXPORT_SYMBOL(acpi_detach_data)

/*******************************************************************************
 *
 * FUNCTION:    acpi_get_data
 *
 * PARAMETERS:  obj_handle          - Namespace node
 *              handler             - Handler used in call to attach_data
 *              data                - Where the data is returned
 *
 * RETURN:      Status
 *
 * DESCRIPTION: Retrieve data that was previously attached to a namespace node.
 *
 ******************************************************************************/
acpi_status
acpi_get_data(acpi_handle obj_handle, acpi_object_handler handler, void **data)
{
        struct acpi_namespace_node *node;
        acpi_status status;

        /* Parameter validation */

        if (!obj_handle || !handler || !data) {
                return (AE_BAD_PARAMETER);
        }

        status = acpi_ut_acquire_mutex(ACPI_MTX_NAMESPACE);
        if (ACPI_FAILURE(status)) {
                return (status);
        }

        /* Convert and validate the handle */

        node = acpi_ns_validate_handle(obj_handle);
        if (!node) {
                status = AE_BAD_PARAMETER;
                goto unlock_and_exit;
        }

        status = acpi_ns_get_attached_data(node, handler, data);

unlock_and_exit:
        (void)acpi_ut_release_mutex(ACPI_MTX_NAMESPACE);
        return (status);
}

ACPI_EXPORT_SYMBOL(acpi_get_data)