drivers/acpi/acpica/exfield.c - third_party/linux - Git at Google

 // SPDX-License-Identifier: BSD-3-Clause OR GPL-2.0
 /******************************************************************************
  *
  * Module Name: exfield - AML execution - field_unit read/write
  *
  * Copyright (C) 2000 - 2020, Intel Corp.
  *
  *****************************************************************************/

 #include <acpi/acpi.h>
 #include "accommon.h"
 #include "acdispat.h"
 #include "acinterp.h"
 #include "amlcode.h"

 #define _COMPONENT          ACPI_EXECUTER
 ACPI_MODULE_NAME("exfield")

 /*
  * This table maps the various Attrib protocols to the byte transfer
  * length. Used for the generic serial bus.
  */
 #define ACPI_INVALID_PROTOCOL_ID        0x80
 #define ACPI_MAX_PROTOCOL_ID            0x0F
 static const u8 acpi_protocol_lengths[] = {
 	ACPI_INVALID_PROTOCOL_ID,	/* 0 - reserved */
 	ACPI_INVALID_PROTOCOL_ID,	/* 1 - reserved */
 	0x00,			/* 2 - ATTRIB_QUICK */
 	ACPI_INVALID_PROTOCOL_ID,	/* 3 - reserved */
 	0x01,			/* 4 - ATTRIB_SEND_RECEIVE */
 	ACPI_INVALID_PROTOCOL_ID,	/* 5 - reserved */
 	0x01,			/* 6 - ATTRIB_BYTE */
 	ACPI_INVALID_PROTOCOL_ID,	/* 7 - reserved */
 	0x02,			/* 8 - ATTRIB_WORD */
 	ACPI_INVALID_PROTOCOL_ID,	/* 9 - reserved */
 	0xFF,			/* A - ATTRIB_BLOCK  */
 	0xFF,			/* B - ATTRIB_BYTES */
 	0x02,			/* C - ATTRIB_PROCESS_CALL */
 	0xFF,			/* D - ATTRIB_BLOCK_PROCESS_CALL */
 	0xFF,			/* E - ATTRIB_RAW_BYTES */
 	0xFF			/* F - ATTRIB_RAW_PROCESS_BYTES */
 };

 #define PCC_MASTER_SUBSPACE     3

 /*
  * The following macros determine a given offset is a COMD field.
  * According to the specification, generic subspaces (types 0-2) contains a
  * 2-byte COMD field at offset 4 and master subspaces (type 3) contains a 4-byte
  * COMD field starting at offset 12.
  */
 #define GENERIC_SUBSPACE_COMMAND(a)     (4 == a || a == 5)
 #define MASTER_SUBSPACE_COMMAND(a)      (12 <= a && a <= 15)

 /*******************************************************************************
  *
  * FUNCTION:    acpi_ex_get_protocol_buffer_length
  *
  * PARAMETERS:  protocol_id     - The type of the protocol indicated by region
  *                                field access attributes
  *              return_length   - Where the protocol byte transfer length is
  *                                returned
  *
  * RETURN:      Status and decoded byte transfer length
  *
  * DESCRIPTION: This routine returns the length of the generic_serial_bus
  *              protocol bytes
  *
  ******************************************************************************/

 acpi_status
 acpi_ex_get_protocol_buffer_length(u32 protocol_id, u32 *return_length)
 {

 	if ((protocol_id > ACPI_MAX_PROTOCOL_ID) ||
 	    (acpi_protocol_lengths[protocol_id] == ACPI_INVALID_PROTOCOL_ID)) {
 		ACPI_ERROR((AE_INFO,
 			    "Invalid Field/AccessAs protocol ID: 0x%4.4X",
 			    protocol_id));

 		return (AE_AML_PROTOCOL);
 	}

 	*return_length = acpi_protocol_lengths[protocol_id];
 	return (AE_OK);
 }

 /*******************************************************************************
  *
  * FUNCTION:    acpi_ex_read_data_from_field
  *
  * PARAMETERS:  walk_state          - Current execution state
  *              obj_desc            - The named field
  *              ret_buffer_desc     - Where the return data object is stored
  *
  * RETURN:      Status
  *
  * DESCRIPTION: Read from a named field. Returns either an Integer or a
  *              Buffer, depending on the size of the field and whether if a
  *              field is created by the create_field() operator.
  *
  ******************************************************************************/

 acpi_status
 acpi_ex_read_data_from_field(struct acpi_walk_state *walk_state,
 			     union acpi_operand_object *obj_desc,
 			     union acpi_operand_object **ret_buffer_desc)
 {
 	acpi_status status;
 	union acpi_operand_object *buffer_desc;
 	void *buffer;
 	u32 buffer_length;

 	ACPI_FUNCTION_TRACE_PTR(ex_read_data_from_field, obj_desc);

 	/* Parameter validation */

 	if (!obj_desc) {
 		return_ACPI_STATUS(AE_AML_NO_OPERAND);
 	}
 	if (!ret_buffer_desc) {
 		return_ACPI_STATUS(AE_BAD_PARAMETER);
 	}

 	if (obj_desc->common.type == ACPI_TYPE_BUFFER_FIELD) {
 		/*
 		 * If the buffer_field arguments have not been previously evaluated,
 		 * evaluate them now and save the results.
 		 */
 		if (!(obj_desc->common.flags & AOPOBJ_DATA_VALID)) {
 			status = acpi_ds_get_buffer_field_arguments(obj_desc);
 			if (ACPI_FAILURE(status)) {
 				return_ACPI_STATUS(status);
 			}
 		}
 	} else if ((obj_desc->common.type == ACPI_TYPE_LOCAL_REGION_FIELD) &&
 		   (obj_desc->field.region_obj->region.space_id ==
 		    ACPI_ADR_SPACE_SMBUS
 		    || obj_desc->field.region_obj->region.space_id ==
 		    ACPI_ADR_SPACE_GSBUS
 		    || obj_desc->field.region_obj->region.space_id ==
 		    ACPI_ADR_SPACE_IPMI)) {

 		/* SMBus, GSBus, IPMI serial */

 		status = acpi_ex_read_serial_bus(obj_desc, ret_buffer_desc);
 		return_ACPI_STATUS(status);
 	}

 	/*
 	 * Allocate a buffer for the contents of the field.
 	 *
 	 * If the field is larger than the current integer width, create
 	 * a BUFFER to hold it. Otherwise, use an INTEGER. This allows
 	 * the use of arithmetic operators on the returned value if the
 	 * field size is equal or smaller than an Integer.
 	 *
 	 * However, all buffer fields created by create_field operator needs to
 	 * remain as a buffer to match other AML interpreter implementations.
 	 *
 	 * Note: Field.length is in bits.
 	 */
 	buffer_length =
 	    (acpi_size)ACPI_ROUND_BITS_UP_TO_BYTES(obj_desc->field.bit_length);

 	if (buffer_length > acpi_gbl_integer_byte_width ||
 	    (obj_desc->common.type == ACPI_TYPE_BUFFER_FIELD &&
 	     obj_desc->buffer_field.is_create_field)) {

 		/* Field is too large for an Integer, create a Buffer instead */

 		buffer_desc = acpi_ut_create_buffer_object(buffer_length);
 		if (!buffer_desc) {
 			return_ACPI_STATUS(AE_NO_MEMORY);
 		}
 		buffer = buffer_desc->buffer.pointer;
 	} else {
 		/* Field will fit within an Integer (normal case) */

 		buffer_desc = acpi_ut_create_integer_object((u64) 0);
 		if (!buffer_desc) {
 			return_ACPI_STATUS(AE_NO_MEMORY);
 		}

 		buffer_length = acpi_gbl_integer_byte_width;
 		buffer = &buffer_desc->integer.value;
 	}

 	if ((obj_desc->common.type == ACPI_TYPE_LOCAL_REGION_FIELD) &&
 	    (obj_desc->field.region_obj->region.space_id ==
 	     ACPI_ADR_SPACE_GPIO)) {

 		/* General Purpose I/O */

 		status = acpi_ex_read_gpio(obj_desc, buffer);
 		goto exit;
 	} else if ((obj_desc->common.type == ACPI_TYPE_LOCAL_REGION_FIELD) &&
 		   (obj_desc->field.region_obj->region.space_id ==
 		    ACPI_ADR_SPACE_PLATFORM_COMM)) {
 		/*
 		 * Reading from a PCC field unit does not require the handler because
 		 * it only requires reading from the internal_pcc_buffer.
 		 */
 		ACPI_DEBUG_PRINT((ACPI_DB_BFIELD,
 				  "PCC FieldRead bits %u\n",
 				  obj_desc->field.bit_length));

 		memcpy(buffer,
 		       obj_desc->field.region_obj->field.internal_pcc_buffer +
 		       obj_desc->field.base_byte_offset,
 		       (acpi_size)ACPI_ROUND_BITS_UP_TO_BYTES(obj_desc->field.
 							      bit_length));

 		*ret_buffer_desc = buffer_desc;
 		return AE_OK;
 	}

 	ACPI_DEBUG_PRINT((ACPI_DB_BFIELD,
 			  "FieldRead [TO]:   Obj %p, Type %X, Buf %p, ByteLen %X\n",
 			  obj_desc, obj_desc->common.type, buffer,
 			  buffer_length));
 	ACPI_DEBUG_PRINT((ACPI_DB_BFIELD,
 			  "FieldRead [FROM]: BitLen %X, BitOff %X, ByteOff %X\n",
 			  obj_desc->common_field.bit_length,
 			  obj_desc->common_field.start_field_bit_offset,
 			  obj_desc->common_field.base_byte_offset));

 	/* Lock entire transaction if requested */

 	acpi_ex_acquire_global_lock(obj_desc->common_field.field_flags);

 	/* Read from the field */

 	status = acpi_ex_extract_from_field(obj_desc, buffer, buffer_length);
 	acpi_ex_release_global_lock(obj_desc->common_field.field_flags);

 exit:
 	if (ACPI_FAILURE(status)) {
 		acpi_ut_remove_reference(buffer_desc);
 	} else {
 		*ret_buffer_desc = buffer_desc;
 	}

 	return_ACPI_STATUS(status);
 }

 /*******************************************************************************
  *
  * FUNCTION:    acpi_ex_write_data_to_field
  *
  * PARAMETERS:  source_desc         - Contains data to write
  *              obj_desc            - The named field
  *              result_desc         - Where the return value is returned, if any
  *
  * RETURN:      Status
  *
  * DESCRIPTION: Write to a named field
  *
  ******************************************************************************/

 acpi_status
 acpi_ex_write_data_to_field(union acpi_operand_object *source_desc,
 			    union acpi_operand_object *obj_desc,
 			    union acpi_operand_object **result_desc)
 {
 	acpi_status status;
 	u32 buffer_length;
 	u32 data_length;
 	void *buffer;

 	ACPI_FUNCTION_TRACE_PTR(ex_write_data_to_field, obj_desc);

 	/* Parameter validation */

 	if (!source_desc || !obj_desc) {
 		return_ACPI_STATUS(AE_AML_NO_OPERAND);
 	}

 	if (obj_desc->common.type == ACPI_TYPE_BUFFER_FIELD) {
 		/*
 		 * If the buffer_field arguments have not been previously evaluated,
 		 * evaluate them now and save the results.
 		 */
 		if (!(obj_desc->common.flags & AOPOBJ_DATA_VALID)) {
 			status = acpi_ds_get_buffer_field_arguments(obj_desc);
 			if (ACPI_FAILURE(status)) {
 				return_ACPI_STATUS(status);
 			}
 		}
 	} else if ((obj_desc->common.type == ACPI_TYPE_LOCAL_REGION_FIELD) &&
 		   (obj_desc->field.region_obj->region.space_id ==
 		    ACPI_ADR_SPACE_GPIO)) {

 		/* General Purpose I/O */

 		status = acpi_ex_write_gpio(source_desc, obj_desc, result_desc);
 		return_ACPI_STATUS(status);
 	} else if ((obj_desc->common.type == ACPI_TYPE_LOCAL_REGION_FIELD) &&
 		   (obj_desc->field.region_obj->region.space_id ==
 		    ACPI_ADR_SPACE_SMBUS
 		    || obj_desc->field.region_obj->region.space_id ==
 		    ACPI_ADR_SPACE_GSBUS
 		    || obj_desc->field.region_obj->region.space_id ==
 		    ACPI_ADR_SPACE_IPMI)) {

 		/* SMBus, GSBus, IPMI serial */

 		status =
 		    acpi_ex_write_serial_bus(source_desc, obj_desc,
 					     result_desc);
 		return_ACPI_STATUS(status);
 	} else if ((obj_desc->common.type == ACPI_TYPE_LOCAL_REGION_FIELD) &&
 		   (obj_desc->field.region_obj->region.space_id ==
 		    ACPI_ADR_SPACE_PLATFORM_COMM)) {
 		/*
 		 * According to the spec a write to the COMD field will invoke the
 		 * region handler. Otherwise, write to the pcc_internal buffer. This
 		 * implementation will use the offsets specified rather than the name
 		 * of the field. This is considered safer because some firmware tools
 		 * are known to obfiscate named objects.
 		 */
 		data_length =
 		    (acpi_size)ACPI_ROUND_BITS_UP_TO_BYTES(obj_desc->field.
 							   bit_length);
 		memcpy(obj_desc->field.region_obj->field.internal_pcc_buffer +
 		       obj_desc->field.base_byte_offset,
 		       source_desc->buffer.pointer, data_length);

 		if (MASTER_SUBSPACE_COMMAND(obj_desc->field.base_byte_offset)) {

 			/* Perform the write */

 			ACPI_DEBUG_PRINT((ACPI_DB_BFIELD,
 					  "PCC COMD field has been written. Invoking PCC handler now.\n"));

 			status =
 			    acpi_ex_access_region(obj_desc, 0,
 						  (u64 *)obj_desc->field.
 						  region_obj->field.
 						  internal_pcc_buffer,
 						  ACPI_WRITE);
 			return_ACPI_STATUS(status);
 		}
 		return (AE_OK);
 	}

 	/* Get a pointer to the data to be written */

 	switch (source_desc->common.type) {
 	case ACPI_TYPE_INTEGER:

 		buffer = &source_desc->integer.value;
 		buffer_length = sizeof(source_desc->integer.value);
 		break;

 	case ACPI_TYPE_BUFFER:

 		buffer = source_desc->buffer.pointer;
 		buffer_length = source_desc->buffer.length;
 		break;

 	case ACPI_TYPE_STRING:

 		buffer = source_desc->string.pointer;
 		buffer_length = source_desc->string.length;
 		break;

 	default:
 		return_ACPI_STATUS(AE_AML_OPERAND_TYPE);
 	}

 	ACPI_DEBUG_PRINT((ACPI_DB_BFIELD,
 			  "FieldWrite [FROM]: Obj %p (%s:%X), Buf %p, ByteLen %X\n",
 			  source_desc,
 			  acpi_ut_get_type_name(source_desc->common.type),
 			  source_desc->common.type, buffer, buffer_length));

 	ACPI_DEBUG_PRINT((ACPI_DB_BFIELD,
 			  "FieldWrite [TO]:   Obj %p (%s:%X), BitLen %X, BitOff %X, ByteOff %X\n",
 			  obj_desc,
 			  acpi_ut_get_type_name(obj_desc->common.type),
 			  obj_desc->common.type,
 			  obj_desc->common_field.bit_length,
 			  obj_desc->common_field.start_field_bit_offset,
 			  obj_desc->common_field.base_byte_offset));

 	/* Lock entire transaction if requested */

 	acpi_ex_acquire_global_lock(obj_desc->common_field.field_flags);

 	/* Write to the field */

 	status = acpi_ex_insert_into_field(obj_desc, buffer, buffer_length);
 	acpi_ex_release_global_lock(obj_desc->common_field.field_flags);
 	return_ACPI_STATUS(status);
 }
	// SPDX-License-Identifier: BSD-3-Clause OR GPL-2.0
	/******************************************************************************
	*
	* Module Name: exfield - AML execution - field_unit read/write
	*
	* Copyright (C) 2000 - 2020, Intel Corp.
	*
	*****************************************************************************/

	#include <acpi/acpi.h>
	#include "accommon.h"
	#include "acdispat.h"
	#include "acinterp.h"
	#include "amlcode.h"

	#define _COMPONENT ACPI_EXECUTER
	ACPI_MODULE_NAME("exfield")

	/*
	* This table maps the various Attrib protocols to the byte transfer
	* length. Used for the generic serial bus.
	*/
	#define ACPI_INVALID_PROTOCOL_ID 0x80
	#define ACPI_MAX_PROTOCOL_ID 0x0F
	static const u8 acpi_protocol_lengths[] = {
	ACPI_INVALID_PROTOCOL_ID, /* 0 - reserved */
	ACPI_INVALID_PROTOCOL_ID, /* 1 - reserved */
	0x00, /* 2 - ATTRIB_QUICK */
	ACPI_INVALID_PROTOCOL_ID, /* 3 - reserved */
	0x01, /* 4 - ATTRIB_SEND_RECEIVE */
	ACPI_INVALID_PROTOCOL_ID, /* 5 - reserved */
	0x01, /* 6 - ATTRIB_BYTE */
	ACPI_INVALID_PROTOCOL_ID, /* 7 - reserved */
	0x02, /* 8 - ATTRIB_WORD */
	ACPI_INVALID_PROTOCOL_ID, /* 9 - reserved */
	0xFF, /* A - ATTRIB_BLOCK */
	0xFF, /* B - ATTRIB_BYTES */
	0x02, /* C - ATTRIB_PROCESS_CALL */
	0xFF, /* D - ATTRIB_BLOCK_PROCESS_CALL */
	0xFF, /* E - ATTRIB_RAW_BYTES */
	0xFF /* F - ATTRIB_RAW_PROCESS_BYTES */
	};

	#define PCC_MASTER_SUBSPACE 3

	/*
	* The following macros determine a given offset is a COMD field.
	* According to the specification, generic subspaces (types 0-2) contains a
	* 2-byte COMD field at offset 4 and master subspaces (type 3) contains a 4-byte
	* COMD field starting at offset 12.
	*/
	#define GENERIC_SUBSPACE_COMMAND(a) (4 == a \|\| a == 5)
	#define MASTER_SUBSPACE_COMMAND(a) (12 <= a && a <= 15)

	/*******************************************************************************
	*
	* FUNCTION: acpi_ex_get_protocol_buffer_length
	*
	* PARAMETERS: protocol_id - The type of the protocol indicated by region
	* field access attributes
	* return_length - Where the protocol byte transfer length is
	* returned
	*
	* RETURN: Status and decoded byte transfer length
	*
	* DESCRIPTION: This routine returns the length of the generic_serial_bus
	* protocol bytes
	*
	******************************************************************************/

	acpi_status
	acpi_ex_get_protocol_buffer_length(u32 protocol_id, u32 *return_length)
	{

	if ((protocol_id > ACPI_MAX_PROTOCOL_ID) \|\|
	(acpi_protocol_lengths[protocol_id] == ACPI_INVALID_PROTOCOL_ID)) {
	ACPI_ERROR((AE_INFO,
	"Invalid Field/AccessAs protocol ID: 0x%4.4X",
	protocol_id));

	return (AE_AML_PROTOCOL);
	}

	*return_length = acpi_protocol_lengths[protocol_id];
	return (AE_OK);
	}

	/*******************************************************************************
	*
	* FUNCTION: acpi_ex_read_data_from_field
	*
	* PARAMETERS: walk_state - Current execution state
	* obj_desc - The named field
	* ret_buffer_desc - Where the return data object is stored
	*
	* RETURN: Status
	*
	* DESCRIPTION: Read from a named field. Returns either an Integer or a
	* Buffer, depending on the size of the field and whether if a
	* field is created by the create_field() operator.
	*
	******************************************************************************/

	acpi_status
	acpi_ex_read_data_from_field(struct acpi_walk_state *walk_state,
	union acpi_operand_object *obj_desc,
	union acpi_operand_object **ret_buffer_desc)
	{
	acpi_status status;
	union acpi_operand_object *buffer_desc;
	void *buffer;
	u32 buffer_length;

	ACPI_FUNCTION_TRACE_PTR(ex_read_data_from_field, obj_desc);

	/* Parameter validation */

	if (!obj_desc) {
	return_ACPI_STATUS(AE_AML_NO_OPERAND);
	}
	if (!ret_buffer_desc) {
	return_ACPI_STATUS(AE_BAD_PARAMETER);
	}

	if (obj_desc->common.type == ACPI_TYPE_BUFFER_FIELD) {
	/*
	* If the buffer_field arguments have not been previously evaluated,
	* evaluate them now and save the results.
	*/
	if (!(obj_desc->common.flags & AOPOBJ_DATA_VALID)) {
	status = acpi_ds_get_buffer_field_arguments(obj_desc);
	if (ACPI_FAILURE(status)) {
	return_ACPI_STATUS(status);
	}
	}
	} else if ((obj_desc->common.type == ACPI_TYPE_LOCAL_REGION_FIELD) &&
	(obj_desc->field.region_obj->region.space_id ==
	ACPI_ADR_SPACE_SMBUS
	\|\| obj_desc->field.region_obj->region.space_id ==
	ACPI_ADR_SPACE_GSBUS
	\|\| obj_desc->field.region_obj->region.space_id ==
	ACPI_ADR_SPACE_IPMI)) {

	/* SMBus, GSBus, IPMI serial */

	status = acpi_ex_read_serial_bus(obj_desc, ret_buffer_desc);
	return_ACPI_STATUS(status);
	}

	/*
	* Allocate a buffer for the contents of the field.
	*
	* If the field is larger than the current integer width, create
	* a BUFFER to hold it. Otherwise, use an INTEGER. This allows
	* the use of arithmetic operators on the returned value if the
	* field size is equal or smaller than an Integer.
	*
	* However, all buffer fields created by create_field operator needs to
	* remain as a buffer to match other AML interpreter implementations.
	*
	* Note: Field.length is in bits.
	*/
	buffer_length =
	(acpi_size)ACPI_ROUND_BITS_UP_TO_BYTES(obj_desc->field.bit_length);

	if (buffer_length > acpi_gbl_integer_byte_width \|\|
	(obj_desc->common.type == ACPI_TYPE_BUFFER_FIELD &&
	obj_desc->buffer_field.is_create_field)) {

	/* Field is too large for an Integer, create a Buffer instead */

	buffer_desc = acpi_ut_create_buffer_object(buffer_length);
	if (!buffer_desc) {
	return_ACPI_STATUS(AE_NO_MEMORY);
	}
	buffer = buffer_desc->buffer.pointer;
	} else {
	/* Field will fit within an Integer (normal case) */

	buffer_desc = acpi_ut_create_integer_object((u64) 0);
	if (!buffer_desc) {
	return_ACPI_STATUS(AE_NO_MEMORY);
	}

	buffer_length = acpi_gbl_integer_byte_width;
	buffer = &buffer_desc->integer.value;
	}

	if ((obj_desc->common.type == ACPI_TYPE_LOCAL_REGION_FIELD) &&
	(obj_desc->field.region_obj->region.space_id ==
	ACPI_ADR_SPACE_GPIO)) {

	/* General Purpose I/O */

	status = acpi_ex_read_gpio(obj_desc, buffer);
	goto exit;
	} else if ((obj_desc->common.type == ACPI_TYPE_LOCAL_REGION_FIELD) &&
	(obj_desc->field.region_obj->region.space_id ==
	ACPI_ADR_SPACE_PLATFORM_COMM)) {
	/*
	* Reading from a PCC field unit does not require the handler because
	* it only requires reading from the internal_pcc_buffer.
	*/
	ACPI_DEBUG_PRINT((ACPI_DB_BFIELD,
	"PCC FieldRead bits %u\n",
	obj_desc->field.bit_length));

	memcpy(buffer,
	obj_desc->field.region_obj->field.internal_pcc_buffer +
	obj_desc->field.base_byte_offset,
	(acpi_size)ACPI_ROUND_BITS_UP_TO_BYTES(obj_desc->field.
	bit_length));

	*ret_buffer_desc = buffer_desc;
	return AE_OK;
	}

	ACPI_DEBUG_PRINT((ACPI_DB_BFIELD,
	"FieldRead [TO]: Obj %p, Type %X, Buf %p, ByteLen %X\n",
	obj_desc, obj_desc->common.type, buffer,
	buffer_length));
	ACPI_DEBUG_PRINT((ACPI_DB_BFIELD,
	"FieldRead [FROM]: BitLen %X, BitOff %X, ByteOff %X\n",
	obj_desc->common_field.bit_length,
	obj_desc->common_field.start_field_bit_offset,
	obj_desc->common_field.base_byte_offset));

	/* Lock entire transaction if requested */

	acpi_ex_acquire_global_lock(obj_desc->common_field.field_flags);

	/* Read from the field */

	status = acpi_ex_extract_from_field(obj_desc, buffer, buffer_length);
	acpi_ex_release_global_lock(obj_desc->common_field.field_flags);

	exit:
	if (ACPI_FAILURE(status)) {
	acpi_ut_remove_reference(buffer_desc);
	} else {
	*ret_buffer_desc = buffer_desc;
	}

	return_ACPI_STATUS(status);
	}

	/*******************************************************************************
	*
	* FUNCTION: acpi_ex_write_data_to_field
	*
	* PARAMETERS: source_desc - Contains data to write
	* obj_desc - The named field
	* result_desc - Where the return value is returned, if any
	*
	* RETURN: Status
	*
	* DESCRIPTION: Write to a named field
	*
	******************************************************************************/

	acpi_status
	acpi_ex_write_data_to_field(union acpi_operand_object *source_desc,
	union acpi_operand_object *obj_desc,
	union acpi_operand_object **result_desc)
	{
	acpi_status status;
	u32 buffer_length;
	u32 data_length;
	void *buffer;

	ACPI_FUNCTION_TRACE_PTR(ex_write_data_to_field, obj_desc);

	/* Parameter validation */

	if (!source_desc \|\| !obj_desc) {
	return_ACPI_STATUS(AE_AML_NO_OPERAND);
	}

	if (obj_desc->common.type == ACPI_TYPE_BUFFER_FIELD) {
	/*
	* If the buffer_field arguments have not been previously evaluated,
	* evaluate them now and save the results.
	*/
	if (!(obj_desc->common.flags & AOPOBJ_DATA_VALID)) {
	status = acpi_ds_get_buffer_field_arguments(obj_desc);
	if (ACPI_FAILURE(status)) {
	return_ACPI_STATUS(status);
	}
	}
	} else if ((obj_desc->common.type == ACPI_TYPE_LOCAL_REGION_FIELD) &&
	(obj_desc->field.region_obj->region.space_id ==
	ACPI_ADR_SPACE_GPIO)) {

	/* General Purpose I/O */

	status = acpi_ex_write_gpio(source_desc, obj_desc, result_desc);
	return_ACPI_STATUS(status);
	} else if ((obj_desc->common.type == ACPI_TYPE_LOCAL_REGION_FIELD) &&
	(obj_desc->field.region_obj->region.space_id ==
	ACPI_ADR_SPACE_SMBUS
	\|\| obj_desc->field.region_obj->region.space_id ==
	ACPI_ADR_SPACE_GSBUS
	\|\| obj_desc->field.region_obj->region.space_id ==
	ACPI_ADR_SPACE_IPMI)) {

	/* SMBus, GSBus, IPMI serial */

	status =
	acpi_ex_write_serial_bus(source_desc, obj_desc,
	result_desc);
	return_ACPI_STATUS(status);
	} else if ((obj_desc->common.type == ACPI_TYPE_LOCAL_REGION_FIELD) &&
	(obj_desc->field.region_obj->region.space_id ==
	ACPI_ADR_SPACE_PLATFORM_COMM)) {
	/*
	* According to the spec a write to the COMD field will invoke the
	* region handler. Otherwise, write to the pcc_internal buffer. This
	* implementation will use the offsets specified rather than the name
	* of the field. This is considered safer because some firmware tools
	* are known to obfiscate named objects.
	*/
	data_length =
	(acpi_size)ACPI_ROUND_BITS_UP_TO_BYTES(obj_desc->field.
	bit_length);
	memcpy(obj_desc->field.region_obj->field.internal_pcc_buffer +
	obj_desc->field.base_byte_offset,
	source_desc->buffer.pointer, data_length);

	if (MASTER_SUBSPACE_COMMAND(obj_desc->field.base_byte_offset)) {

	/* Perform the write */

	ACPI_DEBUG_PRINT((ACPI_DB_BFIELD,
	"PCC COMD field has been written. Invoking PCC handler now.\n"));

	status =
	acpi_ex_access_region(obj_desc, 0,
	(u64 *)obj_desc->field.
	region_obj->field.
	internal_pcc_buffer,
	ACPI_WRITE);
	return_ACPI_STATUS(status);
	}
	return (AE_OK);
	}

	/* Get a pointer to the data to be written */

	switch (source_desc->common.type) {
	case ACPI_TYPE_INTEGER:

	buffer = &source_desc->integer.value;
	buffer_length = sizeof(source_desc->integer.value);
	break;

	case ACPI_TYPE_BUFFER:

	buffer = source_desc->buffer.pointer;
	buffer_length = source_desc->buffer.length;
	break;

	case ACPI_TYPE_STRING:

	buffer = source_desc->string.pointer;
	buffer_length = source_desc->string.length;
	break;

	default:
	return_ACPI_STATUS(AE_AML_OPERAND_TYPE);
	}

	ACPI_DEBUG_PRINT((ACPI_DB_BFIELD,
	"FieldWrite [FROM]: Obj %p (%s:%X), Buf %p, ByteLen %X\n",
	source_desc,
	acpi_ut_get_type_name(source_desc->common.type),
	source_desc->common.type, buffer, buffer_length));

	ACPI_DEBUG_PRINT((ACPI_DB_BFIELD,
	"FieldWrite [TO]: Obj %p (%s:%X), BitLen %X, BitOff %X, ByteOff %X\n",
	obj_desc,
	acpi_ut_get_type_name(obj_desc->common.type),
	obj_desc->common.type,
	obj_desc->common_field.bit_length,
	obj_desc->common_field.start_field_bit_offset,
	obj_desc->common_field.base_byte_offset));

	/* Lock entire transaction if requested */

	acpi_ex_acquire_global_lock(obj_desc->common_field.field_flags);

	/* Write to the field */

	status = acpi_ex_insert_into_field(obj_desc, buffer, buffer_length);
	acpi_ex_release_global_lock(obj_desc->common_field.field_flags);
	return_ACPI_STATUS(status);
	}