utresrc.c

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/*******************************************************************************
 *
 * Module Name: utresrc - Resource management utilities
 *
 ******************************************************************************/

/*
 * Copyright (C) 2000 - 2012, Intel Corp.
 * 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 "accommon.h"
#include "acresrc.h"

#define _COMPONENT          ACPI_UTILITIES
ACPI_MODULE_NAME("utresrc")
#if defined(ACPI_DISASSEMBLER) || defined (ACPI_DEBUGGER)
/*
 * Strings used to decode resource descriptors.
 * Used by both the disassembler and the debugger resource dump routines
 */
const char *acpi_gbl_bm_decode[] = {
    "NotBusMaster",
    "BusMaster"
};

const char *acpi_gbl_config_decode[] = {
    "0 - Good Configuration",
    "1 - Acceptable Configuration",
    "2 - Suboptimal Configuration",
    "3 - ***Invalid Configuration***",
};

const char *acpi_gbl_consume_decode[] = {
    "ResourceProducer",
    "ResourceConsumer"
};

const char *acpi_gbl_dec_decode[] = {
    "PosDecode",
    "SubDecode"
};

const char *acpi_gbl_he_decode[] = {
    "Level",
    "Edge"
};

const char *acpi_gbl_io_decode[] = {
    "Decode10",
    "Decode16"
};

const char *acpi_gbl_ll_decode[] = {
    "ActiveHigh",
    "ActiveLow"
};

const char *acpi_gbl_max_decode[] = {
    "MaxNotFixed",
    "MaxFixed"
};

const char *acpi_gbl_mem_decode[] = {
    "NonCacheable",
    "Cacheable",
    "WriteCombining",
    "Prefetchable"
};

const char *acpi_gbl_min_decode[] = {
    "MinNotFixed",
    "MinFixed"
};

const char *acpi_gbl_mtp_decode[] = {
    "AddressRangeMemory",
    "AddressRangeReserved",
    "AddressRangeACPI",
    "AddressRangeNVS"
};

const char *acpi_gbl_rng_decode[] = {
    "InvalidRanges",
    "NonISAOnlyRanges",
    "ISAOnlyRanges",
    "EntireRange"
};

const char *acpi_gbl_rw_decode[] = {
    "ReadOnly",
    "ReadWrite"
};

const char *acpi_gbl_shr_decode[] = {
    "Exclusive",
    "Shared"
};

const char *acpi_gbl_siz_decode[] = {
    "Transfer8",
    "Transfer8_16",
    "Transfer16",
    "InvalidSize"
};

const char *acpi_gbl_trs_decode[] = {
    "DenseTranslation",
    "SparseTranslation"
};

const char *acpi_gbl_ttp_decode[] = {
    "TypeStatic",
    "TypeTranslation"
};

const char *acpi_gbl_typ_decode[] = {
    "Compatibility",
    "TypeA",
    "TypeB",
    "TypeF"
};

const char *acpi_gbl_ppc_decode[] = {
    "PullDefault",
    "PullUp",
    "PullDown",
    "PullNone"
};

const char *acpi_gbl_ior_decode[] = {
    "IoRestrictionNone",
    "IoRestrictionInputOnly",
    "IoRestrictionOutputOnly",
    "IoRestrictionNoneAndPreserve"
};

const char *acpi_gbl_dts_decode[] = {
    "Width8bit",
    "Width16bit",
    "Width32bit",
    "Width64bit",
    "Width128bit",
    "Width256bit",
};

/* GPIO connection type */

const char *acpi_gbl_ct_decode[] = {
    "Interrupt",
    "I/O"
};

/* Serial bus type */

const char *acpi_gbl_sbt_decode[] = {
    "/* UNKNOWN serial bus type */",
    "I2C",
    "SPI",
    "UART"
};

/* I2C serial bus access mode */

const char *acpi_gbl_am_decode[] = {
    "AddressingMode7Bit",
    "AddressingMode10Bit"
};

/* I2C serial bus slave mode */

const char *acpi_gbl_sm_decode[] = {
    "ControllerInitiated",
    "DeviceInitiated"
};

/* SPI serial bus wire mode */

const char *acpi_gbl_wm_decode[] = {
    "FourWireMode",
    "ThreeWireMode"
};

/* SPI serial clock phase */

const char *acpi_gbl_cph_decode[] = {
    "ClockPhaseFirst",
    "ClockPhaseSecond"
};

/* SPI serial bus clock polarity */

const char *acpi_gbl_cpo_decode[] = {
    "ClockPolarityLow",
    "ClockPolarityHigh"
};

/* SPI serial bus device polarity */

const char *acpi_gbl_dp_decode[] = {
    "PolarityLow",
    "PolarityHigh"
};

/* UART serial bus endian */

const char *acpi_gbl_ed_decode[] = {
    "LittleEndian",
    "BigEndian"
};

/* UART serial bus bits per byte */

const char *acpi_gbl_bpb_decode[] = {
    "DataBitsFive",
    "DataBitsSix",
    "DataBitsSeven",
    "DataBitsEight",
    "DataBitsNine",
    "/* UNKNOWN Bits per byte */",
    "/* UNKNOWN Bits per byte */",
    "/* UNKNOWN Bits per byte */"
};

/* UART serial bus stop bits */

const char *acpi_gbl_sb_decode[] = {
    "StopBitsNone",
    "StopBitsOne",
    "StopBitsOnePlusHalf",
    "StopBitsTwo"
};

/* UART serial bus flow control */

const char *acpi_gbl_fc_decode[] = {
    "FlowControlNone",
    "FlowControlHardware",
    "FlowControlXON",
    "/* UNKNOWN flow control keyword */"
};

/* UART serial bus parity type */

const char *acpi_gbl_pt_decode[] = {
    "ParityTypeNone",
    "ParityTypeEven",
    "ParityTypeOdd",
    "ParityTypeMark",
    "ParityTypeSpace",
    "/* UNKNOWN parity keyword */",
    "/* UNKNOWN parity keyword */",
    "/* UNKNOWN parity keyword */"
};

#endif

/*
 * Base sizes of the raw AML resource descriptors, indexed by resource type.
 * Zero indicates a reserved (and therefore invalid) resource type.
 */
const u8 acpi_gbl_resource_aml_sizes[] = {
    /* Small descriptors */

    0,
    0,
    0,
    0,
    ACPI_AML_SIZE_SMALL(struct aml_resource_irq),
    ACPI_AML_SIZE_SMALL(struct aml_resource_dma),
    ACPI_AML_SIZE_SMALL(struct aml_resource_start_dependent),
    ACPI_AML_SIZE_SMALL(struct aml_resource_end_dependent),
    ACPI_AML_SIZE_SMALL(struct aml_resource_io),
    ACPI_AML_SIZE_SMALL(struct aml_resource_fixed_io),
    ACPI_AML_SIZE_SMALL(struct aml_resource_fixed_dma),
    0,
    0,
    0,
    ACPI_AML_SIZE_SMALL(struct aml_resource_vendor_small),
    ACPI_AML_SIZE_SMALL(struct aml_resource_end_tag),

    /* Large descriptors */

    0,
    ACPI_AML_SIZE_LARGE(struct aml_resource_memory24),
    ACPI_AML_SIZE_LARGE(struct aml_resource_generic_register),
    0,
    ACPI_AML_SIZE_LARGE(struct aml_resource_vendor_large),
    ACPI_AML_SIZE_LARGE(struct aml_resource_memory32),
    ACPI_AML_SIZE_LARGE(struct aml_resource_fixed_memory32),
    ACPI_AML_SIZE_LARGE(struct aml_resource_address32),
    ACPI_AML_SIZE_LARGE(struct aml_resource_address16),
    ACPI_AML_SIZE_LARGE(struct aml_resource_extended_irq),
    ACPI_AML_SIZE_LARGE(struct aml_resource_address64),
    ACPI_AML_SIZE_LARGE(struct aml_resource_extended_address64),
    ACPI_AML_SIZE_LARGE(struct aml_resource_gpio),
    0,
    ACPI_AML_SIZE_LARGE(struct aml_resource_common_serialbus),
};

const u8 acpi_gbl_resource_aml_serial_bus_sizes[] = {
    0,
    ACPI_AML_SIZE_LARGE(struct aml_resource_i2c_serialbus),
    ACPI_AML_SIZE_LARGE(struct aml_resource_spi_serialbus),
    ACPI_AML_SIZE_LARGE(struct aml_resource_uart_serialbus),
};

/*
 * Resource types, used to validate the resource length field.
 * The length of fixed-length types must match exactly, variable
 * lengths must meet the minimum required length, etc.
 * Zero indicates a reserved (and therefore invalid) resource type.
 */
static const u8 acpi_gbl_resource_types[] = {
    /* Small descriptors */

    0,
    0,
    0,
    0,
    ACPI_SMALL_VARIABLE_LENGTH, /* 04 IRQ */
    ACPI_FIXED_LENGTH,  /* 05 DMA */
    ACPI_SMALL_VARIABLE_LENGTH, /* 06 start_dependent_functions */
    ACPI_FIXED_LENGTH,  /* 07 end_dependent_functions */
    ACPI_FIXED_LENGTH,  /* 08 IO */
    ACPI_FIXED_LENGTH,  /* 09 fixed_IO */
    ACPI_FIXED_LENGTH,  /* 0A fixed_DMA */
    0,
    0,
    0,
    ACPI_VARIABLE_LENGTH,   /* 0E vendor_short */
    ACPI_FIXED_LENGTH,  /* 0F end_tag */

    /* Large descriptors */

    0,
    ACPI_FIXED_LENGTH,  /* 01 Memory24 */
    ACPI_FIXED_LENGTH,  /* 02 generic_register */
    0,
    ACPI_VARIABLE_LENGTH,   /* 04 vendor_long */
    ACPI_FIXED_LENGTH,  /* 05 Memory32 */
    ACPI_FIXED_LENGTH,  /* 06 memory32_fixed */
    ACPI_VARIABLE_LENGTH,   /* 07 Dword* address */
    ACPI_VARIABLE_LENGTH,   /* 08 Word* address */
    ACPI_VARIABLE_LENGTH,   /* 09 extended_IRQ */
    ACPI_VARIABLE_LENGTH,   /* 0A Qword* address */
    ACPI_FIXED_LENGTH,  /* 0B Extended* address */
    ACPI_VARIABLE_LENGTH,   /* 0C Gpio* */
    0,
    ACPI_VARIABLE_LENGTH    /* 0E *serial_bus */
};

/*
 * For the iASL compiler/disassembler, we don't want any error messages
 * because the disassembler uses the resource validation code to determine
 * if Buffer objects are actually Resource Templates.
 */
#ifdef ACPI_ASL_COMPILER
#define ACPI_RESOURCE_ERROR(plist)
#else
#define ACPI_RESOURCE_ERROR(plist)  ACPI_ERROR(plist)
#endif

/*******************************************************************************
 *
 * FUNCTION:    acpi_ut_walk_aml_resources
 *
 * PARAMETERS:  aml             - Pointer to the raw AML resource template
 *              aml_length      - Length of the entire template
 *              user_function   - Called once for each descriptor found. If
 *                                NULL, a pointer to the end_tag is returned
 *              context         - Passed to user_function
 *
 * RETURN:      Status
 *
 * DESCRIPTION: Walk a raw AML resource list(buffer). User function called
 *              once for each resource found.
 *
 ******************************************************************************/

acpi_status
acpi_ut_walk_aml_resources(u8 * aml,
               acpi_size aml_length,
               acpi_walk_aml_callback user_function, void **context)
{
    acpi_status status;
    u8 *end_aml;
    u8 resource_index;
    u32 length;
    u32 offset = 0;
    u8 end_tag[2] = { 0x79, 0x00 };

    ACPI_FUNCTION_TRACE(ut_walk_aml_resources);

    /* The absolute minimum resource template is one end_tag descriptor */

    if (aml_length < sizeof(struct aml_resource_end_tag)) {
        return_ACPI_STATUS(AE_AML_NO_RESOURCE_END_TAG);
    }

    /* Point to the end of the resource template buffer */

    end_aml = aml + aml_length;

    /* Walk the byte list, abort on any invalid descriptor type or length */

    while (aml < end_aml) {

        /* Validate the Resource Type and Resource Length */

        status = acpi_ut_validate_resource(aml, &resource_index);
        if (ACPI_FAILURE(status)) {
            /*
             * Exit on failure. Cannot continue because the descriptor length
             * may be bogus also.
             */
            return_ACPI_STATUS(status);
        }

        /* Get the length of this descriptor */

        length = acpi_ut_get_descriptor_length(aml);

        /* Invoke the user function */

        if (user_function) {
            status =
                user_function(aml, length, offset, resource_index,
                      context);
            if (ACPI_FAILURE(status)) {
                return_ACPI_STATUS(status);
            }
        }

        /* An end_tag descriptor terminates this resource template */

        if (acpi_ut_get_resource_type(aml) ==
            ACPI_RESOURCE_NAME_END_TAG) {
            /*
             * There must be at least one more byte in the buffer for
             * the 2nd byte of the end_tag
             */
            if ((aml + 1) >= end_aml) {
                return_ACPI_STATUS(AE_AML_NO_RESOURCE_END_TAG);
            }

            /* Return the pointer to the end_tag if requested */

            if (!user_function) {
                *context = aml;
            }

            /* Normal exit */

            return_ACPI_STATUS(AE_OK);
        }

        aml += length;
        offset += length;
    }

    /* Did not find an end_tag descriptor */

    if (user_function) {

        /* Insert an end_tag anyway. acpi_rs_get_list_length always leaves room */

        (void)acpi_ut_validate_resource(end_tag, &resource_index);
        status =
            user_function(end_tag, 2, offset, resource_index, context);
        if (ACPI_FAILURE(status)) {
            return_ACPI_STATUS(status);
        }
    }

    return_ACPI_STATUS(AE_AML_NO_RESOURCE_END_TAG);
}

/*******************************************************************************
 *
 * FUNCTION:    acpi_ut_validate_resource
 *
 * PARAMETERS:  aml             - Pointer to the raw AML resource descriptor
 *              return_index    - Where the resource index is returned. NULL
 *                                if the index is not required.
 *
 * RETURN:      Status, and optionally the Index into the global resource tables
 *
 * DESCRIPTION: Validate an AML resource descriptor by checking the Resource
 *              Type and Resource Length. Returns an index into the global
 *              resource information/dispatch tables for later use.
 *
 ******************************************************************************/

acpi_status acpi_ut_validate_resource(void *aml, u8 * return_index)
{
    union aml_resource *aml_resource;
    u8 resource_type;
    u8 resource_index;
    acpi_rs_length resource_length;
    acpi_rs_length minimum_resource_length;

    ACPI_FUNCTION_ENTRY();

    /*
     * 1) Validate the resource_type field (Byte 0)
     */
    resource_type = ACPI_GET8(aml);

    /*
     * Byte 0 contains the descriptor name (Resource Type)
     * Examine the large/small bit in the resource header
     */
    if (resource_type & ACPI_RESOURCE_NAME_LARGE) {

        /* Verify the large resource type (name) against the max */

        if (resource_type > ACPI_RESOURCE_NAME_LARGE_MAX) {
            goto invalid_resource;
        }

        /*
         * Large Resource Type -- bits 6:0 contain the name
         * Translate range 0x80-0x8B to index range 0x10-0x1B
         */
        resource_index = (u8) (resource_type - 0x70);
    } else {
        /*
         * Small Resource Type -- bits 6:3 contain the name
         * Shift range to index range 0x00-0x0F
         */
        resource_index = (u8)
            ((resource_type & ACPI_RESOURCE_NAME_SMALL_MASK) >> 3);
    }

    /*
     * Check validity of the resource type, via acpi_gbl_resource_types. Zero
     * indicates an invalid resource.
     */
    if (!acpi_gbl_resource_types[resource_index]) {
        goto invalid_resource;
    }

    /*
     * Validate the resource_length field. This ensures that the length
     * is at least reasonable, and guarantees that it is non-zero.
     */
    resource_length = acpi_ut_get_resource_length(aml);
    minimum_resource_length = acpi_gbl_resource_aml_sizes[resource_index];

    /* Validate based upon the type of resource - fixed length or variable */

    switch (acpi_gbl_resource_types[resource_index]) {
    case ACPI_FIXED_LENGTH:

        /* Fixed length resource, length must match exactly */

        if (resource_length != minimum_resource_length) {
            goto bad_resource_length;
        }
        break;

    case ACPI_VARIABLE_LENGTH:

        /* Variable length resource, length must be at least the minimum */

        if (resource_length < minimum_resource_length) {
            goto bad_resource_length;
        }
        break;

    case ACPI_SMALL_VARIABLE_LENGTH:

        /* Small variable length resource, length can be (Min) or (Min-1) */

        if ((resource_length > minimum_resource_length) ||
            (resource_length < (minimum_resource_length - 1))) {
            goto bad_resource_length;
        }
        break;

    default:

        /* Shouldn't happen (because of validation earlier), but be sure */

        goto invalid_resource;
    }

    aml_resource = ACPI_CAST_PTR(union aml_resource, aml);
    if (resource_type == ACPI_RESOURCE_NAME_SERIAL_BUS) {

        /* Validate the bus_type field */

        if ((aml_resource->common_serial_bus.type == 0) ||
            (aml_resource->common_serial_bus.type >
             AML_RESOURCE_MAX_SERIALBUSTYPE)) {
            ACPI_RESOURCE_ERROR((AE_INFO,
                         "Invalid/unsupported SerialBus resource descriptor: BusType 0x%2.2X",
                         aml_resource->common_serial_bus.
                         type));
            return (AE_AML_INVALID_RESOURCE_TYPE);
        }
    }

    /* Optionally return the resource table index */

    if (return_index) {
        *return_index = resource_index;
    }

    return (AE_OK);

      invalid_resource:

    ACPI_RESOURCE_ERROR((AE_INFO,
                 "Invalid/unsupported resource descriptor: Type 0x%2.2X",
                 resource_type));
    return (AE_AML_INVALID_RESOURCE_TYPE);

      bad_resource_length:

    ACPI_RESOURCE_ERROR((AE_INFO,
                 "Invalid resource descriptor length: Type "
                 "0x%2.2X, Length 0x%4.4X, MinLength 0x%4.4X",
                 resource_type, resource_length,
                 minimum_resource_length));
    return (AE_AML_BAD_RESOURCE_LENGTH);
}

/*******************************************************************************
 *
 * FUNCTION:    acpi_ut_get_resource_type
 *
 * PARAMETERS:  aml             - Pointer to the raw AML resource descriptor
 *
 * RETURN:      The Resource Type with no extraneous bits (except the
 *              Large/Small descriptor bit -- this is left alone)
 *
 * DESCRIPTION: Extract the Resource Type/Name from the first byte of
 *              a resource descriptor.
 *
 ******************************************************************************/

u8 acpi_ut_get_resource_type(void *aml)
{
    ACPI_FUNCTION_ENTRY();

    /*
     * Byte 0 contains the descriptor name (Resource Type)
     * Examine the large/small bit in the resource header
     */
    if (ACPI_GET8(aml) & ACPI_RESOURCE_NAME_LARGE) {

        /* Large Resource Type -- bits 6:0 contain the name */

        return (ACPI_GET8(aml));
    } else {
        /* Small Resource Type -- bits 6:3 contain the name */

        return ((u8) (ACPI_GET8(aml) & ACPI_RESOURCE_NAME_SMALL_MASK));
    }
}

/*******************************************************************************
 *
 * FUNCTION:    acpi_ut_get_resource_length
 *
 * PARAMETERS:  aml             - Pointer to the raw AML resource descriptor
 *
 * RETURN:      Byte Length
 *
 * DESCRIPTION: Get the "Resource Length" of a raw AML descriptor. By
 *              definition, this does not include the size of the descriptor
 *              header or the length field itself.
 *
 ******************************************************************************/

u16 acpi_ut_get_resource_length(void *aml)
{
    acpi_rs_length resource_length;

    ACPI_FUNCTION_ENTRY();

    /*
     * Byte 0 contains the descriptor name (Resource Type)
     * Examine the large/small bit in the resource header
     */
    if (ACPI_GET8(aml) & ACPI_RESOURCE_NAME_LARGE) {

        /* Large Resource type -- bytes 1-2 contain the 16-bit length */

        ACPI_MOVE_16_TO_16(&resource_length, ACPI_ADD_PTR(u8, aml, 1));

    } else {
        /* Small Resource type -- bits 2:0 of byte 0 contain the length */

        resource_length = (u16) (ACPI_GET8(aml) &
                     ACPI_RESOURCE_NAME_SMALL_LENGTH_MASK);
    }

    return (resource_length);
}

/*******************************************************************************
 *
 * FUNCTION:    acpi_ut_get_resource_header_length
 *
 * PARAMETERS:  aml             - Pointer to the raw AML resource descriptor
 *
 * RETURN:      Length of the AML header (depends on large/small descriptor)
 *
 * DESCRIPTION: Get the length of the header for this resource.
 *
 ******************************************************************************/

u8 acpi_ut_get_resource_header_length(void *aml)
{
    ACPI_FUNCTION_ENTRY();

    /* Examine the large/small bit in the resource header */

    if (ACPI_GET8(aml) & ACPI_RESOURCE_NAME_LARGE) {
        return (sizeof(struct aml_resource_large_header));
    } else {
        return (sizeof(struct aml_resource_small_header));
    }
}

/*******************************************************************************
 *
 * FUNCTION:    acpi_ut_get_descriptor_length
 *
 * PARAMETERS:  aml             - Pointer to the raw AML resource descriptor
 *
 * RETURN:      Byte length
 *
 * DESCRIPTION: Get the total byte length of a raw AML descriptor, including the
 *              length of the descriptor header and the length field itself.
 *              Used to walk descriptor lists.
 *
 ******************************************************************************/

u32 acpi_ut_get_descriptor_length(void *aml)
{
    ACPI_FUNCTION_ENTRY();

    /*
     * Get the Resource Length (does not include header length) and add
     * the header length (depends on if this is a small or large resource)
     */
    return (acpi_ut_get_resource_length(aml) +
        acpi_ut_get_resource_header_length(aml));
}

/*******************************************************************************
 *
 * FUNCTION:    acpi_ut_get_resource_end_tag
 *
 * PARAMETERS:  obj_desc        - The resource template buffer object
 *              end_tag         - Where the pointer to the end_tag is returned
 *
 * RETURN:      Status, pointer to the end tag
 *
 * DESCRIPTION: Find the end_tag resource descriptor in an AML resource template
 *              Note: allows a buffer length of zero.
 *
 ******************************************************************************/

acpi_status
acpi_ut_get_resource_end_tag(union acpi_operand_object * obj_desc,
                 u8 ** end_tag)
{
    acpi_status status;

    ACPI_FUNCTION_TRACE(ut_get_resource_end_tag);

    /* Allow a buffer length of zero */

    if (!obj_desc->buffer.length) {
        *end_tag = obj_desc->buffer.pointer;
        return_ACPI_STATUS(AE_OK);
    }

    /* Validate the template and get a pointer to the end_tag */

    status = acpi_ut_walk_aml_resources(obj_desc->buffer.pointer,
                        obj_desc->buffer.length, NULL,
                        (void **)end_tag);

    return_ACPI_STATUS(status);
}