// SPDX-License-Identifier: BSD-3-Clause OR GPL-2.0
/******************************************************************************
 *
 * Module Name: evregion - Operation Region support
 *
 * Copyright (C) 2000 - 2019, Intel Corp.
 *
 *****************************************************************************/

#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 interpreter.
                 */
                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)));

                /*
                 * Special case for an EC timeout. These are seen so frequently
                 * that an additional error message is helpful
                 */
                if ((region_obj->region.space_id == ACPI_ADR_SPACE_EC) &&
                    (status == AE_TIME)) {
                        ACPI_ERROR((AE_INFO,
                                    "Timeout from EC hardware or EC device driver"));
                }
        }

        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);

        /*
         * These address spaces do not need a call to _REG, since the ACPI
         * specification defines them as: "must always be accessible". Since
         * they never change state (never become unavailable), no need to ever
         * call _REG on them. Also, a data_table is not a "real" address space,
         * so do not call _REG. September 2018.
         */
        if ((space_id == ACPI_ADR_SPACE_SYSTEM_MEMORY) ||
            (space_id == ACPI_ADR_SPACE_SYSTEM_IO) ||
            (space_id == ACPI_ADR_SPACE_DATA_TABLE)) {
                return_VOID;
        }

        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;
}