/****************************************************************************** * * Module Name: exfldio - Aml Field I/O * *****************************************************************************/ /* * Copyright (C) 2000 - 2005, R. Byron Moore * 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 <acpi/acinterp.h> #include <acpi/amlcode.h> #include <acpi/acevents.h> #include <acpi/acdispat.h> #define _COMPONENT ACPI_EXECUTER ACPI_MODULE_NAME("exfldio") /* Local prototypes */ static acpi_status acpi_ex_field_datum_io(union acpi_operand_object *obj_desc, u32 field_datum_byte_offset, acpi_integer * value, u32 read_write); static u8 acpi_ex_register_overflow(union acpi_operand_object *obj_desc, acpi_integer value); static acpi_status acpi_ex_setup_region(union acpi_operand_object *obj_desc, u32 field_datum_byte_offset); /******************************************************************************* * * FUNCTION: acpi_ex_setup_region * * PARAMETERS: obj_desc - Field to be read or written * field_datum_byte_offset - Byte offset of this datum within the * parent field * * RETURN: Status * * DESCRIPTION: Common processing for acpi_ex_extract_from_field and * acpi_ex_insert_into_field. Initialize the Region if necessary and * validate the request. * ******************************************************************************/ static acpi_status acpi_ex_setup_region(union acpi_operand_object *obj_desc, u32 field_datum_byte_offset) { acpi_status status = AE_OK; union acpi_operand_object *rgn_desc; ACPI_FUNCTION_TRACE_U32("ex_setup_region", field_datum_byte_offset); rgn_desc = obj_desc->common_field.region_obj; /* We must have a valid region */ if (ACPI_GET_OBJECT_TYPE(rgn_desc) != ACPI_TYPE_REGION) { ACPI_DEBUG_PRINT((ACPI_DB_ERROR, "Needed Region, found type %X (%s)\n", ACPI_GET_OBJECT_TYPE(rgn_desc), acpi_ut_get_object_type_name(rgn_desc))); return_ACPI_STATUS(AE_AML_OPERAND_TYPE); } /* * If the Region Address and Length have not been previously evaluated, * evaluate them now and save the results. */ if (!(rgn_desc->common.flags & AOPOBJ_DATA_VALID)) { status = acpi_ds_get_region_arguments(rgn_desc); if (ACPI_FAILURE(status)) { return_ACPI_STATUS(status); } } if (rgn_desc->region.space_id == ACPI_ADR_SPACE_SMBUS) { /* SMBus has a non-linear address space */ return_ACPI_STATUS(AE_OK); } #ifdef ACPI_UNDER_DEVELOPMENT /* * If the Field access is any_acc, we can now compute the optimal * access (because we know know the length of the parent region) */ if (!(obj_desc->common.flags & AOPOBJ_DATA_VALID)) { if (ACPI_FAILURE(status)) { return_ACPI_STATUS(status); } } #endif /* * Validate the request. The entire request from the byte offset for a * length of one field datum (access width) must fit within the region. * (Region length is specified in bytes) */ if (rgn_desc->region.length < (obj_desc->common_field.base_byte_offset + field_datum_byte_offset + obj_desc->common_field. access_byte_width)) { if (acpi_gbl_enable_interpreter_slack) { /* * Slack mode only: We will go ahead and allow access to this * field if it is within the region length rounded up to the next * access width boundary. */ if (ACPI_ROUND_UP(rgn_desc->region.length, obj_desc->common_field. access_byte_width) >= (obj_desc->common_field.base_byte_offset + (acpi_native_uint) obj_desc->common_field. access_byte_width + field_datum_byte_offset)) { return_ACPI_STATUS(AE_OK); } } if (rgn_desc->region.length < obj_desc->common_field.access_byte_width) { /* * This is the case where the access_type (acc_word, etc.) is wider * than the region itself. For example, a region of length one * byte, and a field with Dword access specified. */ ACPI_DEBUG_PRINT((ACPI_DB_ERROR, "Field [%4.4s] access width (%d bytes) too large for region [%4.4s] (length %X)\n", acpi_ut_get_node_name(obj_desc-> common_field. node), obj_desc->common_field. access_byte_width, acpi_ut_get_node_name(rgn_desc-> region.node), rgn_desc->region.length)); } /* * Offset rounded up to next multiple of field width * exceeds region length, indicate an error */ ACPI_DEBUG_PRINT((ACPI_DB_ERROR, "Field [%4.4s] Base+Offset+Width %X+%X+%X is beyond end of region [%4.4s] (length %X)\n", acpi_ut_get_node_name(obj_desc->common_field. node), obj_desc->common_field.base_byte_offset, field_datum_byte_offset, obj_desc->common_field.access_byte_width, acpi_ut_get_node_name(rgn_desc->region.node), rgn_desc->region.length)); return_ACPI_STATUS(AE_AML_REGION_LIMIT); } return_ACPI_STATUS(AE_OK); } /******************************************************************************* * * FUNCTION: acpi_ex_access_region * * PARAMETERS: obj_desc - Field to be read * field_datum_byte_offset - Byte offset of this datum within the * parent field * Value - Where to store value (must at least * the size of acpi_integer) * Function - Read or Write flag plus other region- * dependent flags * * RETURN: Status * * DESCRIPTION: Read or Write a single field datum to an Operation Region. * ******************************************************************************/ acpi_status acpi_ex_access_region(union acpi_operand_object *obj_desc, u32 field_datum_byte_offset, acpi_integer * value, u32 function) { acpi_status status; union acpi_operand_object *rgn_desc; acpi_physical_address address; ACPI_FUNCTION_TRACE("ex_access_region"); /* * Ensure that the region operands are fully evaluated and verify * the validity of the request */ status = acpi_ex_setup_region(obj_desc, field_datum_byte_offset); if (ACPI_FAILURE(status)) { return_ACPI_STATUS(status); } /* * The physical address of this field datum is: * * 1) The base of the region, plus * 2) The base offset of the field, plus * 3) The current offset into the field */ rgn_desc = obj_desc->common_field.region_obj; address = rgn_desc->region.address + obj_desc->common_field.base_byte_offset + field_datum_byte_offset; if ((function & ACPI_IO_MASK) == ACPI_READ) { ACPI_DEBUG_PRINT((ACPI_DB_BFIELD, "[READ]")); } else { ACPI_DEBUG_PRINT((ACPI_DB_BFIELD, "[WRITE]")); } ACPI_DEBUG_PRINT_RAW((ACPI_DB_BFIELD, " Region [%s:%X], Width %X, byte_base %X, Offset %X at %8.8X%8.8X\n", acpi_ut_get_region_name(rgn_desc->region. space_id), rgn_desc->region.space_id, obj_desc->common_field.access_byte_width, obj_desc->common_field.base_byte_offset, field_datum_byte_offset, ACPI_FORMAT_UINT64(address))); /* Invoke the appropriate address_space/op_region handler */ status = acpi_ev_address_space_dispatch(rgn_desc, function, address, ACPI_MUL_8(obj_desc-> common_field. access_byte_width), value); if (ACPI_FAILURE(status)) { if (status == AE_NOT_IMPLEMENTED) { ACPI_DEBUG_PRINT((ACPI_DB_ERROR, "Region %s(%X) not implemented\n", acpi_ut_get_region_name(rgn_desc-> region. space_id), rgn_desc->region.space_id)); } else if (status == AE_NOT_EXIST) { ACPI_REPORT_ERROR(("Region %s(%X) has no handler\n", acpi_ut_get_region_name(rgn_desc-> region. space_id), rgn_desc->region.space_id)); } } return_ACPI_STATUS(status); } /******************************************************************************* * * FUNCTION: acpi_ex_register_overflow * * PARAMETERS: obj_desc - Register(Field) to be written * Value - Value to be stored * * RETURN: TRUE if value overflows the field, FALSE otherwise * * DESCRIPTION: Check if a value is out of range of the field being written. * Used to check if the values written to Index and Bank registers * are out of range. Normally, the value is simply truncated * to fit the field, but this case is most likely a serious * coding error in the ASL. * ******************************************************************************/ static u8 acpi_ex_register_overflow(union acpi_operand_object *obj_desc, acpi_integer value) { if (obj_desc->common_field.bit_length >= ACPI_INTEGER_BIT_SIZE) { /* * The field is large enough to hold the maximum integer, so we can * never overflow it. */ return (FALSE); } if (value >= ((acpi_integer) 1 << obj_desc->common_field.bit_length)) { /* * The Value is larger than the maximum value that can fit into * the register. */ return (TRUE); } /* The Value will fit into the field with no truncation */ return (FALSE); } /******************************************************************************* * * FUNCTION: acpi_ex_field_datum_io * * PARAMETERS: obj_desc - Field to be read * field_datum_byte_offset - Byte offset of this datum within the * parent field * Value - Where to store value (must be 64 bits) * read_write - Read or Write flag * * RETURN: Status * * DESCRIPTION: Read or Write a single datum of a field. The field_type is * demultiplexed here to handle the different types of fields * (buffer_field, region_field, index_field, bank_field) * ******************************************************************************/ static acpi_status acpi_ex_field_datum_io(union acpi_operand_object *obj_desc, u32 field_datum_byte_offset, acpi_integer * value, u32 read_write) { acpi_status status; acpi_integer local_value; ACPI_FUNCTION_TRACE_U32("ex_field_datum_io", field_datum_byte_offset); if (read_write == ACPI_READ) { if (!value) { local_value = 0; /* To support reads without saving return value */ value = &local_value; } /* Clear the entire return buffer first, [Very Important!] */ *value = 0; } /* * The four types of fields are: * * buffer_field - Read/write from/to a Buffer * region_field - Read/write from/to a Operation Region. * bank_field - Write to a Bank Register, then read/write from/to an * operation_region * index_field - Write to an Index Register, then read/write from/to a * Data Register */ switch (ACPI_GET_OBJECT_TYPE(obj_desc)) { case 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); } } if (read_write == ACPI_READ) { /* * Copy the data from the source buffer. * Length is the field width in bytes. */ ACPI_MEMCPY(value, (obj_desc->buffer_field.buffer_obj)->buffer. pointer + obj_desc->buffer_field.base_byte_offset + field_datum_byte_offset, obj_desc->common_field.access_byte_width); } else { /* * Copy the data to the target buffer. * Length is the field width in bytes. */ ACPI_MEMCPY((obj_desc->buffer_field.buffer_obj)->buffer. pointer + obj_desc->buffer_field.base_byte_offset + field_datum_byte_offset, value, obj_desc->common_field.access_byte_width); } status = AE_OK; break; case ACPI_TYPE_LOCAL_BANK_FIELD: /* * Ensure that the bank_value is not beyond the capacity of * the register */ if (acpi_ex_register_overflow(obj_desc->bank_field.bank_obj, (acpi_integer) obj_desc-> bank_field.value)) { return_ACPI_STATUS(AE_AML_REGISTER_LIMIT); } /* * For bank_fields, we must write the bank_value to the bank_register * (itself a region_field) before we can access the data. */ status = acpi_ex_insert_into_field(obj_desc->bank_field.bank_obj, &obj_desc->bank_field.value, sizeof(obj_desc->bank_field. value)); if (ACPI_FAILURE(status)) { return_ACPI_STATUS(status); } /* * Now that the Bank has been selected, fall through to the * region_field case and write the datum to the Operation Region */ /*lint -fallthrough */ case ACPI_TYPE_LOCAL_REGION_FIELD: /* * For simple region_fields, we just directly access the owning * Operation Region. */ 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: value_ptr %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_REPORT_ERROR(("Wrong object type in field I/O %X\n", 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, ¤t_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_DEBUG_PRINT((ACPI_DB_ERROR, "write_with_update_rule: Unknown update_rule setting: %X\n", (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, datum_offset %X, Width %X, Value %8.8X%8.8X, merged_value %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_DEBUG_PRINT((ACPI_DB_ERROR, "Field size %X (bits) is too large for buffer (%X)\n", 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 */ 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 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_DEBUG_PRINT((ACPI_DB_ERROR, "Field size %X (bits) is too large for buffer (%X)\n", obj_desc->common_field.bit_length, buffer_length)); return_ACPI_STATUS(AE_BUFFER_OVERFLOW); } /* Compute the number of datums (access width data items) */ mask = ACPI_MASK_BITS_BELOW(obj_desc->common_field.start_field_bit_offset); 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); } /* Start new output datum by merging with previous input datum */ field_offset += obj_desc->common_field.access_byte_width; merged_datum = raw_datum >> (obj_desc->common_field.access_bit_width - obj_desc->common_field.start_field_bit_offset); mask = ACPI_INTEGER_MAX; 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); }