drivers/acpi/acpica/evregion.c

/******************************************************************************
 *
 * Module Name: evregion - Operation Region support
 *
 *****************************************************************************/

/*
 * Copyright (C) 2000 - 2016, 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.
 */

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

#define _COMPONENT          ACPI_EVENTS
ACPI_MODULE_NAME("evregion")

extern u8 acpi_gbl_default_address_spaces[];

/* Local prototypes */

static void
acpi_ev_orphan_ec_reg_method(struct acpi_namespace_node *ec_device_node);

static acpi_status
acpi_ev_reg_run(acpi_handle obj_handle,
		u32 level, void *context, void **return_value);

/*******************************************************************************
 *
 * FUNCTION:    acpi_ev_initialize_op_regions
 *
 * PARAMETERS:  None
 *
 * RETURN:      Status
 *
 * DESCRIPTION: Execute _REG methods for all Operation Regions that have
 *              an installed default region handler.
 *
 ******************************************************************************/

acpi_status acpi_ev_initialize_op_regions(void)
{
	acpi_status status;
	u32 i;

	ACPI_FUNCTION_TRACE(ev_initialize_op_regions);

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

	/* Run the _REG methods for op_regions in each default address space */

	for (i = 0; i < ACPI_NUM_DEFAULT_SPACES; i++) {
		/*
		 * Make sure the installed handler is the DEFAULT handler. If not the
		 * default, the _REG methods will have already been run (when the
		 * handler was installed)
		 */
		if (acpi_ev_has_default_handler(acpi_gbl_root_node,
						acpi_gbl_default_address_spaces
						[i])) {
			acpi_ev_execute_reg_methods(acpi_gbl_root_node,
						    acpi_gbl_default_address_spaces
						    [i], ACPI_REG_CONNECT);
		}
	}

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

/*******************************************************************************
 *
 * FUNCTION:    acpi_ev_address_space_dispatch
 *
 * PARAMETERS:  region_obj          - Internal region object
 *              field_obj           - Corresponding field. Can be NULL.
 *              function            - Read or Write operation
 *              region_offset       - Where in the region to read or write
 *              bit_width           - Field width in bits (8, 16, 32, or 64)
 *              value               - Pointer to in or out value, must be
 *                                    a full 64-bit integer
 *
 * RETURN:      Status
 *
 * DESCRIPTION: Dispatch an address space or operation region access to
 *              a previously installed handler.
 *
 * NOTE: During early initialization, we always install the default region
 * handlers for Memory, I/O and PCI_Config. This ensures that these operation
 * region address spaces are always available as per the ACPI specification.
 * This is especially needed in order to support the execution of
 * module-level AML code during loading of the ACPI tables.
 *
 ******************************************************************************/

acpi_status
acpi_ev_address_space_dispatch(union acpi_operand_object *region_obj,
			       union acpi_operand_object *field_obj,
			       u32 function,
			       u32 region_offset, u32 bit_width, u64 *value)
{
	acpi_status status;
	acpi_adr_space_handler handler;
	acpi_adr_space_setup region_setup;
	union acpi_operand_object *handler_desc;
	union acpi_operand_object *region_obj2;
	void *region_context = NULL;
	struct acpi_connection_info *context;
	acpi_physical_address address;

	ACPI_FUNCTION_TRACE(ev_address_space_dispatch);

	region_obj2 = acpi_ns_get_secondary_object(region_obj);
	if (!region_obj2) {
		return_ACPI_STATUS(AE_NOT_EXIST);
	}

	/* Ensure that there is a handler associated with this region */

	handler_desc = region_obj->region.handler;
	if (!handler_desc) {
		ACPI_ERROR((AE_INFO,
			    "No handler for Region [%4.4s] (%p) [%s]",
			    acpi_ut_get_node_name(region_obj->region.node),
			    region_obj,
			    acpi_ut_get_region_name(region_obj->region.
						    space_id)));

		return_ACPI_STATUS(AE_NOT_EXIST);
	}

	context = handler_desc->address_space.context;

	/*
	 * It may be the case that the region has never been initialized.
	 * Some types of regions require special init code
	 */
	if (!(region_obj->region.flags & AOPOBJ_SETUP_COMPLETE)) {

		/* This region has not been initialized yet, do it */

		region_setup = handler_desc->address_space.setup;
		if (!region_setup) {

			/* No initialization routine, exit with error */

			ACPI_ERROR((AE_INFO,
				    "No init routine for region(%p) [%s]",
				    region_obj,
				    acpi_ut_get_region_name(region_obj->region.
							    space_id)));
			return_ACPI_STATUS(AE_NOT_EXIST);
		}

		/*
		 * We must exit the interpreter because the region setup will
		 * potentially execute control methods (for example, the _REG method
		 * for this region)
		 */
		acpi_ex_exit_interpreter();

		status = region_setup(region_obj, ACPI_REGION_ACTIVATE,
				      context, &region_context);

		/* Re-enter the interpreter */

		acpi_ex_enter_interpreter();

		/* Check for failure of the Region Setup */

		if (ACPI_FAILURE(status)) {
			ACPI_EXCEPTION((AE_INFO, status,
					"During region initialization: [%s]",
					acpi_ut_get_region_name(region_obj->
								region.
								space_id)));
			return_ACPI_STATUS(status);
		}

		/* Region initialization may have been completed by region_setup */

		if (!(region_obj->region.flags & AOPOBJ_SETUP_COMPLETE)) {
			region_obj->region.flags |= AOPOBJ_SETUP_COMPLETE;

			/*
			 * Save the returned context for use in all accesses to
			 * the handler for this particular region
			 */
			if (!(region_obj2->extra.region_context)) {
				region_obj2->extra.region_context =
				    region_context;
			}
		}
	}

	/* We have everything we need, we can invoke the address space handler */

	handler = handler_desc->address_space.handler;
	address = (region_obj->region.address + region_offset);

	/*
	 * Special handling for generic_serial_bus and general_purpose_io:
	 * There are three extra parameters that must be passed to the
	 * handler via the context:
	 *   1) Connection buffer, a resource template from Connection() op
	 *   2) Length of the above buffer
	 *   3) Actual access length from the access_as() op
	 *
	 * In addition, for general_purpose_io, the Address and bit_width fields
	 * are defined as follows:
	 *   1) Address is the pin number index of the field (bit offset from
	 *      the previous Connection)
	 *   2) bit_width is the actual bit length of the field (number of pins)
	 */
	if ((region_obj->region.space_id == ACPI_ADR_SPACE_GSBUS) &&
	    context && field_obj) {

		/* Get the Connection (resource_template) buffer */

		context->connection = field_obj->field.resource_buffer;
		context->length = field_obj->field.resource_length;
		context->access_length = field_obj->field.access_length;
	}
	if ((region_obj->region.space_id == ACPI_ADR_SPACE_GPIO) &&
	    context && field_obj) {

		/* Get the Connection (resource_template) buffer */

		context->connection = field_obj->field.resource_buffer;
		context->length = field_obj->field.resource_length;
		context->access_length = field_obj->field.access_length;
		address = field_obj->field.pin_number_index;
		bit_width = field_obj->field.bit_length;
	}

	ACPI_DEBUG_PRINT((ACPI_DB_OPREGION,
			  "Handler %p (@%p) Address %8.8X%8.8X [%s]\n",
			  &region_obj->region.handler->address_space, handler,
			  ACPI_FORMAT_UINT64(address),
			  acpi_ut_get_region_name(region_obj->region.
						  space_id)));

	if (!(handler_desc->address_space.handler_flags &
	      ACPI_ADDR_HANDLER_DEFAULT_INSTALLED)) {
		/*
		 * For handlers other than the default (supplied) handlers, we must
		 * exit the interpreter because the handler *might* block -- we don't
		 * know what it will do, so we can't hold the lock on the intepreter.
		 */
		acpi_ex_exit_interpreter();
	}

	/* Call the handler */

	status = handler(function, address, bit_width, value, context,
			 region_obj2->extra.region_context);

	if (ACPI_FAILURE(status)) {
		ACPI_EXCEPTION((AE_INFO, status, "Returned by Handler for [%s]",
				acpi_ut_get_region_name(region_obj->region.
							space_id)));
	}

	if (!(handler_desc->address_space.handler_flags &
	      ACPI_ADDR_HANDLER_DEFAULT_INSTALLED)) {
		/*
		 * We just returned from a non-default handler, we must re-enter the
		 * interpreter
		 */
		acpi_ex_enter_interpreter();
	}

	return_ACPI_STATUS(status);
}

/*******************************************************************************
 *
 * FUNCTION:    acpi_ev_detach_region
 *
 * PARAMETERS:  region_obj          - Region Object
 *              acpi_ns_is_locked   - Namespace Region Already Locked?
 *
 * RETURN:      None
 *
 * DESCRIPTION: Break the association between the handler and the region
 *              this is a two way association.
 *
 ******************************************************************************/

void
acpi_ev_detach_region(union acpi_operand_object *region_obj,
		      u8 acpi_ns_is_locked)
{
	union acpi_operand_object *handler_obj;
	union acpi_operand_object *obj_desc;
	union acpi_operand_object *start_desc;
	union acpi_operand_object **last_obj_ptr;
	acpi_adr_space_setup region_setup;
	void **region_context;
	union acpi_operand_object *region_obj2;
	acpi_status status;

	ACPI_FUNCTION_TRACE(ev_detach_region);

	region_obj2 = acpi_ns_get_secondary_object(region_obj);
	if (!region_obj2) {
		return_VOID;
	}
	region_context = &region_obj2->extra.region_context;

	/* Get the address handler from the region object */

	handler_obj = region_obj->region.handler;
	if (!handler_obj) {

		/* This region has no handler, all done */

		return_VOID;
	}

	/* Find this region in the handler's list */

	obj_desc = handler_obj->address_space.region_list;
	start_desc = obj_desc;
	last_obj_ptr = &handler_obj->address_space.region_list;

	while (obj_desc) {

		/* Is this the correct Region? */

		if (obj_desc == region_obj) {
			ACPI_DEBUG_PRINT((ACPI_DB_OPREGION,
					  "Removing Region %p from address handler %p\n",
					  region_obj, handler_obj));

			/* This is it, remove it from the handler's list */

			*last_obj_ptr = obj_desc->region.next;
			obj_desc->region.next = NULL;	/* Must clear field */

			if (acpi_ns_is_locked) {
				status =
				    acpi_ut_release_mutex(ACPI_MTX_NAMESPACE);
				if (ACPI_FAILURE(status)) {
					return_VOID;
				}
			}

			/* Now stop region accesses by executing the _REG method */

			status =
			    acpi_ev_execute_reg_method(region_obj,
						       ACPI_REG_DISCONNECT);
			if (ACPI_FAILURE(status)) {
				ACPI_EXCEPTION((AE_INFO, status,
						"from region _REG, [%s]",
						acpi_ut_get_region_name
						(region_obj->region.space_id)));
			}

			if (acpi_ns_is_locked) {
				status =
				    acpi_ut_acquire_mutex(ACPI_MTX_NAMESPACE);
				if (ACPI_FAILURE(status)) {
					return_VOID;
				}
			}

			/*
			 * If the region has been activated, call the setup handler with
			 * the deactivate notification
			 */
			if (region_obj->region.flags & AOPOBJ_SETUP_COMPLETE) {
				region_setup = handler_obj->address_space.setup;
				status =
				    region_setup(region_obj,
						 ACPI_REGION_DEACTIVATE,
						 handler_obj->address_space.
						 context, region_context);

				/*
				 * region_context should have been released by the deactivate
				 * operation. We don't need access to it anymore here.
				 */
				if (region_context) {
					*region_context = NULL;
				}

				/* Init routine may fail, Just ignore errors */

				if (ACPI_FAILURE(status)) {
					ACPI_EXCEPTION((AE_INFO, status,
							"from region handler - deactivate, [%s]",
							acpi_ut_get_region_name
							(region_obj->region.
							 space_id)));
				}

				region_obj->region.flags &=
				    ~(AOPOBJ_SETUP_COMPLETE);
			}

			/*
			 * Remove handler reference in the region
			 *
			 * NOTE: this doesn't mean that the region goes away, the region
			 * is just inaccessible as indicated to the _REG method
			 *
			 * If the region is on the handler's list, this must be the
			 * region's handler
			 */
			region_obj->region.handler = NULL;
			acpi_ut_remove_reference(handler_obj);

			return_VOID;
		}

		/* Walk the linked list of handlers */

		last_obj_ptr = &obj_desc->region.next;
		obj_desc = obj_desc->region.next;

		/* Prevent infinite loop if list is corrupted */

		if (obj_desc == start_desc) {
			ACPI_ERROR((AE_INFO,
				    "Circular handler list in region object %p",
				    region_obj));
			return_VOID;
		}
	}

	/* If we get here, the region was not in the handler's region list */

	ACPI_DEBUG_PRINT((ACPI_DB_OPREGION,
			  "Cannot remove region %p from address handler %p\n",
			  region_obj, handler_obj));

	return_VOID;
}

/*******************************************************************************
 *
 * FUNCTION:    acpi_ev_attach_region
 *
 * PARAMETERS:  handler_obj         - Handler Object
 *              region_obj          - Region Object
 *              acpi_ns_is_locked   - Namespace Region Already Locked?
 *
 * RETURN:      None
 *
 * DESCRIPTION: Create the association between the handler and the region
 *              this is a two way association.
 *
 ******************************************************************************/

acpi_status
acpi_ev_attach_region(union acpi_operand_object *handler_obj,
		      union acpi_operand_object *region_obj,
		      u8 acpi_ns_is_locked)
{

	ACPI_FUNCTION_TRACE(ev_attach_region);

	/* Install the region's handler */

	if (region_obj->region.handler) {
		return_ACPI_STATUS(AE_ALREADY_EXISTS);
	}

	ACPI_DEBUG_PRINT((ACPI_DB_OPREGION,
			  "Adding Region [%4.4s] %p to address handler %p [%s]\n",
			  acpi_ut_get_node_name(region_obj->region.node),
			  region_obj, handler_obj,
			  acpi_ut_get_region_name(region_obj->region.
						  space_id)));

	/* Link this region to the front of the handler's list */

	region_obj->region.next = handler_obj->address_space.region_list;
	handler_obj->address_space.region_list = region_obj;
	region_obj->region.handler = handler_obj;
	acpi_ut_add_reference(handler_obj);

	return_ACPI_STATUS(AE_OK);
}

/*******************************************************************************
 *
 * FUNCTION:    acpi_ev_execute_reg_method
 *
 * PARAMETERS:  region_obj          - Region object
 *              function            - Passed to _REG: On (1) or Off (0)
 *
 * RETURN:      Status
 *
 * DESCRIPTION: Execute _REG method for a region
 *
 ******************************************************************************/

acpi_status
acpi_ev_execute_reg_method(union acpi_operand_object *region_obj, u32 function)
{
	struct acpi_evaluate_info *info;
	union acpi_operand_object *args[3];
	union acpi_operand_object *region_obj2;
	const acpi_name *reg_name_ptr =
	    ACPI_CAST_PTR(acpi_name, METHOD_NAME__REG);
	struct acpi_namespace_node *method_node;
	struct acpi_namespace_node *node;
	acpi_status status;

	ACPI_FUNCTION_TRACE(ev_execute_reg_method);

	if (!acpi_gbl_namespace_initialized ||
	    region_obj->region.handler == NULL) {
		return_ACPI_STATUS(AE_OK);
	}

	region_obj2 = acpi_ns_get_secondary_object(region_obj);
	if (!region_obj2) {
		return_ACPI_STATUS(AE_NOT_EXIST);
	}

	/*
	 * Find any "_REG" method associated with this region definition.
	 * The method should always be updated as this function may be
	 * invoked after a namespace change.
	 */
	node = region_obj->region.node->parent;
	status =
	    acpi_ns_search_one_scope(*reg_name_ptr, node, ACPI_TYPE_METHOD,
				     &method_node);
	if (ACPI_SUCCESS(status)) {
		/*
		 * The _REG method is optional and there can be only one per
		 * region definition. This will be executed when the handler is
		 * attached or removed.
		 */
		region_obj2->extra.method_REG = method_node;
	}
	if (region_obj2->extra.method_REG == NULL) {
		return_ACPI_STATUS(AE_OK);
	}

	/* _REG(DISCONNECT) should be paired with _REG(CONNECT) */

	if ((function == ACPI_REG_CONNECT &&
	     region_obj->common.flags & AOPOBJ_REG_CONNECTED) ||
	    (function == ACPI_REG_DISCONNECT &&
	     !(region_obj->common.flags & AOPOBJ_REG_CONNECTED))) {
		return_ACPI_STATUS(AE_OK);
	}

	/* Allocate and initialize the evaluation information block */

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

	info->prefix_node = region_obj2->extra.method_REG;
	info->relative_pathname = NULL;
	info->parameters = args;
	info->flags = ACPI_IGNORE_RETURN_VALUE;

	/*
	 * The _REG method has two arguments:
	 *
	 * arg0 - Integer:
	 *  Operation region space ID Same value as region_obj->Region.space_id
	 *
	 * arg1 - Integer:
	 *  connection status 1 for connecting the handler, 0 for disconnecting
	 *  the handler (Passed as a parameter)
	 */
	args[0] =
	    acpi_ut_create_integer_object((u64)region_obj->region.space_id);
	if (!args[0]) {
		status = AE_NO_MEMORY;
		goto cleanup1;
	}

	args[1] = acpi_ut_create_integer_object((u64)function);
	if (!args[1]) {
		status = AE_NO_MEMORY;
		goto cleanup2;
	}

	args[2] = NULL;		/* Terminate list */

	/* Execute the method, no return value */

	ACPI_DEBUG_EXEC(acpi_ut_display_init_pathname
			(ACPI_TYPE_METHOD, info->prefix_node, NULL));

	status = acpi_ns_evaluate(info);
	acpi_ut_remove_reference(args[1]);

	if (ACPI_FAILURE(status)) {
		goto cleanup2;
	}

	if (function == ACPI_REG_CONNECT) {
		region_obj->common.flags |= AOPOBJ_REG_CONNECTED;
	} else {
		region_obj->common.flags &= ~AOPOBJ_REG_CONNECTED;
	}

cleanup2:
	acpi_ut_remove_reference(args[0]);

cleanup1:
	ACPI_FREE(info);
	return_ACPI_STATUS(status);
}

/*******************************************************************************
 *
 * FUNCTION:    acpi_ev_execute_reg_methods
 *
 * PARAMETERS:  node            - Namespace node for the device
 *              space_id        - The address space ID
 *              function        - Passed to _REG: On (1) or Off (0)
 *
 * RETURN:      None
 *
 * DESCRIPTION: Run all _REG methods for the input Space ID;
 *              Note: assumes namespace is locked, or system init time.
 *
 ******************************************************************************/

void
acpi_ev_execute_reg_methods(struct acpi_namespace_node *node,
			    acpi_adr_space_type space_id, u32 function)
{
	struct acpi_reg_walk_info info;

	ACPI_FUNCTION_TRACE(ev_execute_reg_methods);

	info.space_id = space_id;
	info.function = function;
	info.reg_run_count = 0;

	ACPI_DEBUG_PRINT_RAW((ACPI_DB_NAMES,
			      "    Running _REG methods for SpaceId %s\n",
			      acpi_ut_get_region_name(info.space_id)));

	/*
	 * Run all _REG methods for all Operation Regions for this space ID. This
	 * is a separate walk in order to handle any interdependencies between
	 * regions and _REG methods. (i.e. handlers must be installed for all
	 * regions of this Space ID before we can run any _REG methods)
	 */
	(void)acpi_ns_walk_namespace(ACPI_TYPE_ANY, node, ACPI_UINT32_MAX,
				     ACPI_NS_WALK_UNLOCK, acpi_ev_reg_run, NULL,
				     &info, NULL);

	/* Special case for EC: handle "orphan" _REG methods with no region */

	if (space_id == ACPI_ADR_SPACE_EC) {
		acpi_ev_orphan_ec_reg_method(node);
	}

	ACPI_DEBUG_PRINT_RAW((ACPI_DB_NAMES,
			      "    Executed %u _REG methods for SpaceId %s\n",
			      info.reg_run_count,
			      acpi_ut_get_region_name(info.space_id)));

	return_VOID;
}

/*******************************************************************************
 *
 * FUNCTION:    acpi_ev_reg_run
 *
 * PARAMETERS:  walk_namespace callback
 *
 * DESCRIPTION: Run _REG method for region objects of the requested spaceID
 *
 ******************************************************************************/

static acpi_status
acpi_ev_reg_run(acpi_handle obj_handle,
		u32 level, void *context, void **return_value)
{
	union acpi_operand_object *obj_desc;
	struct acpi_namespace_node *node;
	acpi_status status;
	struct acpi_reg_walk_info *info;

	info = ACPI_CAST_PTR(struct acpi_reg_walk_info, context);

	/* Convert and validate the device handle */

	node = acpi_ns_validate_handle(obj_handle);
	if (!node) {
		return (AE_BAD_PARAMETER);
	}

	/*
	 * We only care about regions.and objects that are allowed to have address
	 * space handlers
	 */
	if ((node->type != ACPI_TYPE_REGION) && (node != acpi_gbl_root_node)) {
		return (AE_OK);
	}

	/* Check for an existing internal object */

	obj_desc = acpi_ns_get_attached_object(node);
	if (!obj_desc) {

		/* No object, just exit */

		return (AE_OK);
	}

	/* Object is a Region */

	if (obj_desc->region.space_id != info->space_id) {

		/* This region is for a different address space, just ignore it */

		return (AE_OK);
	}

	info->reg_run_count++;
	status = acpi_ev_execute_reg_method(obj_desc, info->function);
	return (status);
}

/*******************************************************************************
 *
 * FUNCTION:    acpi_ev_orphan_ec_reg_method
 *
 * PARAMETERS:  ec_device_node      - Namespace node for an EC device
 *
 * RETURN:      None
 *
 * DESCRIPTION: Execute an "orphan" _REG method that appears under the EC
 *              device. This is a _REG method that has no corresponding region
 *              within the EC device scope. The orphan _REG method appears to
 *              have been enabled by the description of the ECDT in the ACPI
 *              specification: "The availability of the region space can be
 *              detected by providing a _REG method object underneath the
 *              Embedded Controller device."
 *
 *              To quickly access the EC device, we use the ec_device_node used
 *              during EC handler installation. Otherwise, we would need to
 *              perform a time consuming namespace walk, executing _HID
 *              methods to find the EC device.
 *
 *  MUTEX:      Assumes the namespace is locked
 *
 ******************************************************************************/

static void
acpi_ev_orphan_ec_reg_method(struct acpi_namespace_node *ec_device_node)
{
	acpi_handle reg_method;
	struct acpi_namespace_node *next_node;
	acpi_status status;
	struct acpi_object_list args;
	union acpi_object objects[2];

	ACPI_FUNCTION_TRACE(ev_orphan_ec_reg_method);

	if (!ec_device_node) {
		return_VOID;
	}

	/* Namespace is currently locked, must release */

	(void)acpi_ut_release_mutex(ACPI_MTX_NAMESPACE);

	/* Get a handle to a _REG method immediately under the EC device */

	status = acpi_get_handle(ec_device_node, METHOD_NAME__REG, &reg_method);
	if (ACPI_FAILURE(status)) {
		goto exit;	/* There is no _REG method present */
	}

	/*
	 * Execute the _REG method only if there is no Operation Region in
	 * this scope with the Embedded Controller space ID. Otherwise, it
	 * will already have been executed. Note, this allows for Regions
	 * with other space IDs to be present; but the code below will then
	 * execute the _REG method with the embedded_control space_ID argument.
	 */
	next_node = acpi_ns_get_next_node(ec_device_node, NULL);
	while (next_node) {
		if ((next_node->type == ACPI_TYPE_REGION) &&
		    (next_node->object) &&
		    (next_node->object->region.space_id == ACPI_ADR_SPACE_EC)) {
			goto exit;	/* Do not execute the _REG */
		}

		next_node = acpi_ns_get_next_node(ec_device_node, next_node);
	}

	/* Evaluate the _REG(embedded_control,Connect) method */

	args.count = 2;
	args.pointer = objects;
	objects[0].type = ACPI_TYPE_INTEGER;
	objects[0].integer.value = ACPI_ADR_SPACE_EC;
	objects[1].type = ACPI_TYPE_INTEGER;
	objects[1].integer.value = ACPI_REG_CONNECT;

	status = acpi_evaluate_object(reg_method, NULL, &args, NULL);

exit:
	/* We ignore all errors from above, don't care */

	status = acpi_ut_acquire_mutex(ACPI_MTX_NAMESPACE);
	return_VOID;
}