exfldio.c

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		status =
		    acpi_ex_access_region(obj_desc, field_datum_byte_offset,
					  value, read_write);
		break;

	case ACPI_TYPE_LOCAL_INDEX_FIELD:

		/*
		 * Ensure that the index_value is not beyond the capacity of
		 * the register
		 */
		if (acpi_ex_register_overflow(obj_desc->index_field.index_obj,
					      (acpi_integer) obj_desc->
					      index_field.value)) {
			return_ACPI_STATUS(AE_AML_REGISTER_LIMIT);
		}

		/* Write the index value to the index_register (itself a region_field) */

		field_datum_byte_offset += obj_desc->index_field.value;

		ACPI_DEBUG_PRINT((ACPI_DB_BFIELD,
				  "Write to Index Register: Value %8.8X\n",
				  field_datum_byte_offset));

		status =
		    acpi_ex_insert_into_field(obj_desc->index_field.index_obj,
					      &field_datum_byte_offset,
					      sizeof(field_datum_byte_offset));
		if (ACPI_FAILURE(status)) {
			return_ACPI_STATUS(status);
		}

		ACPI_DEBUG_PRINT((ACPI_DB_BFIELD,
				  "I/O to Data Register: ValuePtr %p\n",
				  value));

		if (read_write == ACPI_READ) {

			/* Read the datum from the data_register */

			status =
			    acpi_ex_extract_from_field(obj_desc->index_field.
						       data_obj, value,
						       sizeof(acpi_integer));
		} else {
			/* Write the datum to the data_register */

			status =
			    acpi_ex_insert_into_field(obj_desc->index_field.
						      data_obj, value,
						      sizeof(acpi_integer));
		}
		break;

	default:

		ACPI_ERROR((AE_INFO, "Wrong object type in field I/O %X",
			    ACPI_GET_OBJECT_TYPE(obj_desc)));
		status = AE_AML_INTERNAL;
		break;
	}

	if (ACPI_SUCCESS(status)) {
		if (read_write == ACPI_READ) {
			ACPI_DEBUG_PRINT((ACPI_DB_BFIELD,
					  "Value Read %8.8X%8.8X, Width %d\n",
					  ACPI_FORMAT_UINT64(*value),
					  obj_desc->common_field.
					  access_byte_width));
		} else {
			ACPI_DEBUG_PRINT((ACPI_DB_BFIELD,
					  "Value Written %8.8X%8.8X, Width %d\n",
					  ACPI_FORMAT_UINT64(*value),
					  obj_desc->common_field.
					  access_byte_width));
		}
	}

	return_ACPI_STATUS(status);
}

/*******************************************************************************
 *
 * FUNCTION:    acpi_ex_write_with_update_rule
 *
 * PARAMETERS:  obj_desc                - Field to be written
 *              Mask                    - bitmask within field datum
 *              field_value             - Value to write
 *              field_datum_byte_offset - Offset of datum within field
 *
 * RETURN:      Status
 *
 * DESCRIPTION: Apply the field update rule to a field write
 *
 ******************************************************************************/

acpi_status
acpi_ex_write_with_update_rule(union acpi_operand_object *obj_desc,
			       acpi_integer mask,
			       acpi_integer field_value,
			       u32 field_datum_byte_offset)
{
	acpi_status status = AE_OK;
	acpi_integer merged_value;
	acpi_integer current_value;

	ACPI_FUNCTION_TRACE_U32(ex_write_with_update_rule, mask);

	/* Start with the new bits  */

	merged_value = field_value;

	/* If the mask is all ones, we don't need to worry about the update rule */

	if (mask != ACPI_INTEGER_MAX) {

		/* Decode the update rule */

		switch (obj_desc->common_field.
			field_flags & AML_FIELD_UPDATE_RULE_MASK) {
		case AML_FIELD_UPDATE_PRESERVE:
			/*
			 * Check if update rule needs to be applied (not if mask is all
			 * ones)  The left shift drops the bits we want to ignore.
			 */
			if ((~mask << (ACPI_MUL_8(sizeof(mask)) -
				       ACPI_MUL_8(obj_desc->common_field.
						  access_byte_width))) != 0) {
				/*
				 * Read the current contents of the byte/word/dword containing
				 * the field, and merge with the new field value.
				 */
				status =
				    acpi_ex_field_datum_io(obj_desc,
							   field_datum_byte_offset,
							   &current_value,
							   ACPI_READ);
				if (ACPI_FAILURE(status)) {
					return_ACPI_STATUS(status);
				}

				merged_value |= (current_value & ~mask);
			}
			break;

		case AML_FIELD_UPDATE_WRITE_AS_ONES:

			/* Set positions outside the field to all ones */

			merged_value |= ~mask;
			break;

		case AML_FIELD_UPDATE_WRITE_AS_ZEROS:

			/* Set positions outside the field to all zeros */

			merged_value &= mask;
			break;

		default:

			ACPI_ERROR((AE_INFO,
				    "Unknown UpdateRule value: %X",
				    (obj_desc->common_field.
				     field_flags &
				     AML_FIELD_UPDATE_RULE_MASK)));
			return_ACPI_STATUS(AE_AML_OPERAND_VALUE);
		}
	}

	ACPI_DEBUG_PRINT((ACPI_DB_BFIELD,
			  "Mask %8.8X%8.8X, DatumOffset %X, Width %X, Value %8.8X%8.8X, MergedValue %8.8X%8.8X\n",
			  ACPI_FORMAT_UINT64(mask),
			  field_datum_byte_offset,
			  obj_desc->common_field.access_byte_width,
			  ACPI_FORMAT_UINT64(field_value),
			  ACPI_FORMAT_UINT64(merged_value)));

	/* Write the merged value */

	status = acpi_ex_field_datum_io(obj_desc, field_datum_byte_offset,
					&merged_value, ACPI_WRITE);

	return_ACPI_STATUS(status);
}

/*******************************************************************************
 *
 * FUNCTION:    acpi_ex_extract_from_field
 *
 * PARAMETERS:  obj_desc            - Field to be read
 *              Buffer              - Where to store the field data
 *              buffer_length       - Length of Buffer
 *
 * RETURN:      Status
 *
 * DESCRIPTION: Retrieve the current value of the given field
 *
 ******************************************************************************/

acpi_status
acpi_ex_extract_from_field(union acpi_operand_object *obj_desc,
			   void *buffer, u32 buffer_length)
{
	acpi_status status;
	acpi_integer raw_datum;
	acpi_integer merged_datum;
	u32 field_offset = 0;
	u32 buffer_offset = 0;
	u32 buffer_tail_bits;
	u32 datum_count;
	u32 field_datum_count;
	u32 i;

	ACPI_FUNCTION_TRACE(ex_extract_from_field);

	/* Validate target buffer and clear it */

	if (buffer_length <
	    ACPI_ROUND_BITS_UP_TO_BYTES(obj_desc->common_field.bit_length)) {
		ACPI_ERROR((AE_INFO,
			    "Field size %X (bits) is too large for buffer (%X)",
			    obj_desc->common_field.bit_length, buffer_length));

		return_ACPI_STATUS(AE_BUFFER_OVERFLOW);
	}
	ACPI_MEMSET(buffer, 0, buffer_length);

	/* Compute the number of datums (access width data items) */

	datum_count = ACPI_ROUND_UP_TO(obj_desc->common_field.bit_length,
				       obj_desc->common_field.access_bit_width);
	field_datum_count = ACPI_ROUND_UP_TO(obj_desc->common_field.bit_length +
					     obj_desc->common_field.
					     start_field_bit_offset,
					     obj_desc->common_field.
					     access_bit_width);

	/* Priming read from the field */

	status =
	    acpi_ex_field_datum_io(obj_desc, field_offset, &raw_datum,
				   ACPI_READ);
	if (ACPI_FAILURE(status)) {
		return_ACPI_STATUS(status);
	}
	merged_datum =
	    raw_datum >> obj_desc->common_field.start_field_bit_offset;

	/* Read the rest of the field */

	for (i = 1; i < field_datum_count; i++) {

		/* Get next input datum from the field */

		field_offset += obj_desc->common_field.access_byte_width;
		status = acpi_ex_field_datum_io(obj_desc, field_offset,
						&raw_datum, ACPI_READ);
		if (ACPI_FAILURE(status)) {
			return_ACPI_STATUS(status);
		}

		/*
		 * Merge with previous datum if necessary.
		 *
		 * Note: Before the shift, check if the shift value will be larger than
		 * the integer size. If so, there is no need to perform the operation.
		 * This avoids the differences in behavior between different compilers
		 * concerning shift values larger than the target data width.
		 */
		if ((obj_desc->common_field.access_bit_width -
		     obj_desc->common_field.start_field_bit_offset) <
		    ACPI_INTEGER_BIT_SIZE) {
			merged_datum |=
			    raw_datum << (obj_desc->common_field.
					  access_bit_width -
					  obj_desc->common_field.
					  start_field_bit_offset);
		}

		if (i == datum_count) {
			break;
		}

		/* Write merged datum to target buffer */

		ACPI_MEMCPY(((char *)buffer) + buffer_offset, &merged_datum,
			    ACPI_MIN(obj_desc->common_field.access_byte_width,
				     buffer_length - buffer_offset));

		buffer_offset += obj_desc->common_field.access_byte_width;
		merged_datum =
		    raw_datum >> obj_desc->common_field.start_field_bit_offset;
	}

	/* Mask off any extra bits in the last datum */

	buffer_tail_bits = obj_desc->common_field.bit_length %
	    obj_desc->common_field.access_bit_width;
	if (buffer_tail_bits) {
		merged_datum &= ACPI_MASK_BITS_ABOVE(buffer_tail_bits);
	}

	/* Write the last datum to the buffer */

	ACPI_MEMCPY(((char *)buffer) + buffer_offset, &merged_datum,
		    ACPI_MIN(obj_desc->common_field.access_byte_width,
			     buffer_length - buffer_offset));

	return_ACPI_STATUS(AE_OK);
}

/*******************************************************************************
 *
 * FUNCTION:    acpi_ex_insert_into_field
 *
 * PARAMETERS:  obj_desc            - Field to be written
 *              Buffer              - Data to be written
 *              buffer_length       - Length of Buffer
 *
 * RETURN:      Status
 *
 * DESCRIPTION: Store the Buffer contents into the given field
 *
 ******************************************************************************/

acpi_status
acpi_ex_insert_into_field(union acpi_operand_object *obj_desc,
			  void *buffer, u32 buffer_length)
{
	acpi_status status;
	acpi_integer mask;
	acpi_integer width_mask;
	acpi_integer merged_datum;
	acpi_integer raw_datum = 0;
	u32 field_offset = 0;
	u32 buffer_offset = 0;
	u32 buffer_tail_bits;
	u32 datum_count;
	u32 field_datum_count;
	u32 i;

	ACPI_FUNCTION_TRACE(ex_insert_into_field);

	/* Validate input buffer */

	if (buffer_length <
	    ACPI_ROUND_BITS_UP_TO_BYTES(obj_desc->common_field.bit_length)) {
		ACPI_ERROR((AE_INFO,
			    "Field size %X (bits) is too large for buffer (%X)",
			    obj_desc->common_field.bit_length, buffer_length));

		return_ACPI_STATUS(AE_BUFFER_OVERFLOW);
	}

	/*
	 * Create the bitmasks used for bit insertion.
	 * Note: This if/else is used to bypass compiler differences with the
	 * shift operator
	 */
	if (obj_desc->common_field.access_bit_width == ACPI_INTEGER_BIT_SIZE) {
		width_mask = ACPI_INTEGER_MAX;
	} else {
		width_mask =
		    ACPI_MASK_BITS_ABOVE(obj_desc->common_field.
					 access_bit_width);
	}

	mask = width_mask &
	    ACPI_MASK_BITS_BELOW(obj_desc->common_field.start_field_bit_offset);

	/* Compute the number of datums (access width data items) */

	datum_count = ACPI_ROUND_UP_TO(obj_desc->common_field.bit_length,
				       obj_desc->common_field.access_bit_width);

	field_datum_count = ACPI_ROUND_UP_TO(obj_desc->common_field.bit_length +
					     obj_desc->common_field.
					     start_field_bit_offset,
					     obj_desc->common_field.
					     access_bit_width);

	/* Get initial Datum from the input buffer */

	ACPI_MEMCPY(&raw_datum, buffer,
		    ACPI_MIN(obj_desc->common_field.access_byte_width,
			     buffer_length - buffer_offset));

	merged_datum =
	    raw_datum << obj_desc->common_field.start_field_bit_offset;

	/* Write the entire field */

	for (i = 1; i < field_datum_count; i++) {

		/* Write merged datum to the target field */

		merged_datum &= mask;
		status = acpi_ex_write_with_update_rule(obj_desc, mask,
							merged_datum,
							field_offset);
		if (ACPI_FAILURE(status)) {
			return_ACPI_STATUS(status);
		}

		field_offset += obj_desc->common_field.access_byte_width;

		/*
		 * Start new output datum by merging with previous input datum
		 * if necessary.
		 *
		 * Note: Before the shift, check if the shift value will be larger than
		 * the integer size. If so, there is no need to perform the operation.
		 * This avoids the differences in behavior between different compilers
		 * concerning shift values larger than the target data width.
		 */
		if ((obj_desc->common_field.access_bit_width -
		     obj_desc->common_field.start_field_bit_offset) <
		    ACPI_INTEGER_BIT_SIZE) {
			merged_datum =
			    raw_datum >> (obj_desc->common_field.
					  access_bit_width -
					  obj_desc->common_field.
					  start_field_bit_offset);
		} else {
			merged_datum = 0;
		}

		mask = width_mask;

		if (i == datum_count) {
			break;
		}

		/* Get the next input datum from the buffer */

		buffer_offset += obj_desc->common_field.access_byte_width;
		ACPI_MEMCPY(&raw_datum, ((char *)buffer) + buffer_offset,
			    ACPI_MIN(obj_desc->common_field.access_byte_width,
				     buffer_length - buffer_offset));
		merged_datum |=
		    raw_datum << obj_desc->common_field.start_field_bit_offset;
	}

	/* Mask off any extra bits in the last datum */

	buffer_tail_bits = (obj_desc->common_field.bit_length +
			    obj_desc->common_field.start_field_bit_offset) %
	    obj_desc->common_field.access_bit_width;
	if (buffer_tail_bits) {
		mask &= ACPI_MASK_BITS_ABOVE(buffer_tail_bits);
	}

	/* Write the last datum to the field */

	merged_datum &= mask;
	status = acpi_ex_write_with_update_rule(obj_desc,
						mask, merged_datum,
						field_offset);

	return_ACPI_STATUS(status);
}