// SPDX-License-Identifier: BSD-3-Clause OR GPL-2.0
/******************************************************************************
 *
 * Module Name: exfldio - Aml Field I/O
 *
 * Copyright (C) 2000 - 2021, Intel Corp.
 *
 *****************************************************************************/

#include <acpi/acpi.h>
#include "accommon.h"
#include "acinterp.h"
#include "amlcode.h"
#include "acevents.h"
#include "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, u64 *value, u32 read_write);

static u8
acpi_ex_register_overflow(union acpi_operand_object *obj_desc, u64 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;
        u8 space_id;

        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 (rgn_desc->common.type != ACPI_TYPE_REGION) {
                ACPI_ERROR((AE_INFO, "Needed Region, found type 0x%X (%s)",
                            rgn_desc->common.type,
                            acpi_ut_get_object_type_name(rgn_desc)));

                return_ACPI_STATUS(AE_AML_OPERAND_TYPE);
        }

        space_id = rgn_desc->region.space_id;

        /* Validate the Space ID */

        if (!acpi_is_valid_space_id(space_id)) {
                ACPI_ERROR((AE_INFO,
                            "Invalid/unknown Address Space ID: 0x%2.2X",
                            space_id));
                return_ACPI_STATUS(AE_AML_INVALID_SPACE_ID);
        }

        /*
         * 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);
                }
        }

        /*
         * Exit now for SMBus, GSBus or IPMI address space, it has a non-linear
         * address space and the request cannot be directly validated
         */
        if (space_id == ACPI_ADR_SPACE_SMBUS ||
            space_id == ACPI_ADR_SPACE_GSBUS ||
            space_id == ACPI_ADR_SPACE_IPMI) {

                /* SMBus or IPMI 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. acpi_size cast for 64-bit compile.
                         */
                        if (ACPI_ROUND_UP(rgn_desc->region.length,
                                          obj_desc->common_field.
                                          access_byte_width) >=
                            ((acpi_size)obj_desc->common_field.
                             base_byte_offset +
                             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_ERROR((AE_INFO,
                                    "Field [%4.4s] access width (%u bytes) "
                                    "too large for region [%4.4s] (length %u)",
                                    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_ERROR((AE_INFO,
                            "Field [%4.4s] Base+Offset+Width %u+%u+%u "
                            "is beyond end of region [%4.4s] (length %u)",
                            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
 *                                        64 bits)
 *              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, u64 *value, u32 function)
{
        acpi_status status;
        union acpi_operand_object *rgn_desc;
        u32 region_offset;

        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;
        region_offset =
            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, ByteBase %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(rgn_desc->region.address +
                                                 region_offset)));

        /* Invoke the appropriate address_space/op_region handler */

        status = acpi_ev_address_space_dispatch(rgn_desc, obj_desc,
                                                function, region_offset,
                                                ACPI_MUL_8(obj_desc->
                                                           common_field.
                                                           access_byte_width),
                                                value);

        if (ACPI_FAILURE(status)) {
                if (status == AE_NOT_IMPLEMENTED) {
                        ACPI_ERROR((AE_INFO,
                                    "Region %s (ID=%u) not implemented",
                                    acpi_ut_get_region_name(rgn_desc->region.
                                                            space_id),
                                    rgn_desc->region.space_id));
                } else if (status == AE_NOT_EXIST) {
                        ACPI_ERROR((AE_INFO,
                                    "Region %s (ID=%u) has no handler",
                                    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, u64 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 >= ((u64) 1 << obj_desc->common_field.bit_length)) {
                /*
                 * The Value is larger than the maximum value that can fit into
                 * the register.
                 */
                ACPI_ERROR((AE_INFO,
                            "Index value 0x%8.8X%8.8X overflows field width 0x%X",
                            ACPI_FORMAT_UINT64(value),
                            obj_desc->common_field.bit_length));

                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, u64 *value, u32 read_write)
{
        acpi_status status;
        u64 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 (obj_desc->common.type) {
        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.
                         */
                        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.
                         */
                        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,
                                              (u64) 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
                 */

                ACPI_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,
                                              (u64) 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);
                }

                if (read_write == ACPI_READ) {

                        /* Read the datum from the data_register */

                        ACPI_DEBUG_PRINT((ACPI_DB_BFIELD,
                                          "Read from Data Register\n"));

                        status =
                            acpi_ex_extract_from_field(obj_desc->index_field.
                                                       data_obj, value,
                                                       sizeof(u64));
                } else {
                        /* Write the datum to the data_register */

                        ACPI_DEBUG_PRINT((ACPI_DB_BFIELD,
                                          "Write to Data Register: Value %8.8X%8.8X\n",
                                          ACPI_FORMAT_UINT64(*value)));

                        status =
                            acpi_ex_insert_into_field(obj_desc->index_field.
                                                      data_obj, value,
                                                      sizeof(u64));
                }
                break;

        default:

                ACPI_ERROR((AE_INFO, "Wrong object type in field I/O %u",
                            obj_desc->common.type));
                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 %u\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 %u\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,
                               u64 mask,
                               u64 field_value, u32 field_datum_byte_offset)
{
        acpi_status status = AE_OK;
        u64 merged_value;
        u64 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_UINT64_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: 0x%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;
        u64 raw_datum;
        u64 merged_datum;
        u32 field_offset = 0;
        u32 buffer_offset = 0;
        u32 buffer_tail_bits;
        u32 datum_count;
        u32 field_datum_count;
        u32 access_bit_width;
        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 %u (bits) is too large for buffer (%u)",
                            obj_desc->common_field.bit_length, buffer_length));

                return_ACPI_STATUS(AE_BUFFER_OVERFLOW);
        }

        memset(buffer, 0, buffer_length);
        access_bit_width = ACPI_MUL_8(obj_desc->common_field.access_byte_width);

        /* Handle the simple case here */

        if ((obj_desc->common_field.start_field_bit_offset == 0) &&
            (obj_desc->common_field.bit_length == access_bit_width)) {
                if (buffer_length >= sizeof(u64)) {
                        status =
                            acpi_ex_field_datum_io(obj_desc, 0, buffer,
                                                   ACPI_READ);
                } else {
                        /* Use raw_datum (u64) to handle buffers < 64 bits */

                        status =
                            acpi_ex_field_datum_io(obj_desc, 0, &raw_datum,
                                                   ACPI_READ);
                        memcpy(buffer, &raw_datum, buffer_length);
                }

                return_ACPI_STATUS(status);
        }

/* TBD: Move to common setup code */

        /* Field algorithm is limited to sizeof(u64), truncate if needed */

        if (obj_desc->common_field.access_byte_width > sizeof(u64)) {
                obj_desc->common_field.access_byte_width = sizeof(u64);
                access_bit_width = sizeof(u64) * 8;
        }

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

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

        field_datum_count = ACPI_ROUND_UP_TO(obj_desc->common_field.bit_length +
                                             obj_desc->common_field.
                                             start_field_bit_offset,
                                             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 (access_bit_width -
                    obj_desc->common_field.start_field_bit_offset <
                    ACPI_INTEGER_BIT_SIZE) {
                        merged_datum |=
                            raw_datum << (access_bit_width -
                                          obj_desc->common_field.
                                          start_field_bit_offset);
                }

                if (i == datum_count) {
                        break;
                }

                /* Write merged datum to target buffer */

                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 % access_bit_width;
        if (buffer_tail_bits) {
                merged_datum &= ACPI_MASK_BITS_ABOVE(buffer_tail_bits);
        }

        /* Write the last datum to the buffer */

        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)
{
        void *new_buffer;
        acpi_status status;
        u64 mask;
        u64 width_mask;
        u64 merged_datum;
        u64 raw_datum = 0;
        u32 field_offset = 0;
        u32 buffer_offset = 0;
        u32 buffer_tail_bits;
        u32 datum_count;
        u32 field_datum_count;
        u32 access_bit_width;
        u32 required_length;
        u32 i;

        ACPI_FUNCTION_TRACE(ex_insert_into_field);

        /* Validate input buffer */

        new_buffer = NULL;
        required_length =
            ACPI_ROUND_BITS_UP_TO_BYTES(obj_desc->common_field.bit_length);

        /*
         * We must have a buffer that is at least as long as the field
         * we are writing to. This is because individual fields are
         * indivisible and partial writes are not supported -- as per
         * the ACPI specification.
         */
        if (buffer_length < required_length) {

                /* We need to create a new buffer */

                new_buffer = ACPI_ALLOCATE_ZEROED(required_length);
                if (!new_buffer) {
                        return_ACPI_STATUS(AE_NO_MEMORY);
                }

                /*
                 * Copy the original data to the new buffer, starting
                 * at Byte zero. All unused (upper) bytes of the
                 * buffer will be 0.
                 */
                memcpy((char *)new_buffer, (char *)buffer, buffer_length);
                buffer = new_buffer;
                buffer_length = required_length;
        }

/* TBD: Move to common setup code */

        /* Algo is limited to sizeof(u64), so cut the access_byte_width */
        if (obj_desc->common_field.access_byte_width > sizeof(u64)) {
                obj_desc->common_field.access_byte_width = sizeof(u64);
        }

        access_bit_width = ACPI_MUL_8(obj_desc->common_field.access_byte_width);

        /* Create the bitmasks used for bit insertion */

        width_mask = ACPI_MASK_BITS_ABOVE_64(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,
                                       access_bit_width);

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

        /* Get initial Datum from the input buffer */

        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)) {
                        goto exit;
                }

                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 ((access_bit_width -
                     obj_desc->common_field.start_field_bit_offset) <
                    ACPI_INTEGER_BIT_SIZE) {
                        merged_datum =
                            raw_datum >> (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;
                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) %
            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);

exit:
        /* Free temporary buffer if we used one */

        if (new_buffer) {
                ACPI_FREE(new_buffer);
        }
        return_ACPI_STATUS(status);
}