source/compiler/dtcompile.c

/******************************************************************************
 *
 * Module Name: dtcompile.c - Front-end for data table compiler
 *
 *****************************************************************************/

/******************************************************************************
 *
 * 1. Copyright Notice
 *
 * Some or all of this work - Copyright (c) 1999 - 2017, Intel Corp.
 * All rights reserved.
 *
 * 2. License
 *
 * 2.1. This is your license from Intel Corp. under its intellectual property
 * rights. You may have additional license terms from the party that provided
 * you this software, covering your right to use that party's intellectual
 * property rights.
 *
 * 2.2. Intel grants, free of charge, to any person ("Licensee") obtaining a
 * copy of the source code appearing in this file ("Covered Code") an
 * irrevocable, perpetual, worldwide license under Intel's copyrights in the
 * base code distributed originally by Intel ("Original Intel Code") to copy,
 * make derivatives, distribute, use and display any portion of the Covered
 * Code in any form, with the right to sublicense such rights; and
 *
 * 2.3. Intel grants Licensee a non-exclusive and non-transferable patent
 * license (with the right to sublicense), under only those claims of Intel
 * patents that are infringed by the Original Intel Code, to make, use, sell,
 * offer to sell, and import the Covered Code and derivative works thereof
 * solely to the minimum extent necessary to exercise the above copyright
 * license, and in no event shall the patent license extend to any additions
 * to or modifications of the Original Intel Code. No other license or right
 * is granted directly or by implication, estoppel or otherwise;
 *
 * The above copyright and patent license is granted only if the following
 * conditions are met:
 *
 * 3. Conditions
 *
 * 3.1. Redistribution of Source with Rights to Further Distribute Source.
 * Redistribution of source code of any substantial portion of the Covered
 * Code or modification with rights to further distribute source must include
 * the above Copyright Notice, the above License, this list of Conditions,
 * and the following Disclaimer and Export Compliance provision. In addition,
 * Licensee must cause all Covered Code to which Licensee contributes to
 * contain a file documenting the changes Licensee made to create that Covered
 * Code and the date of any change. Licensee must include in that file the
 * documentation of any changes made by any predecessor Licensee. Licensee
 * must include a prominent statement that the modification is derived,
 * directly or indirectly, from Original Intel Code.
 *
 * 3.2. Redistribution of Source with no Rights to Further Distribute Source.
 * Redistribution of source code of any substantial portion of the Covered
 * Code or modification without rights to further distribute source must
 * include the following Disclaimer and Export Compliance provision in the
 * documentation and/or other materials provided with distribution. In
 * addition, Licensee may not authorize further sublicense of source of any
 * portion of the Covered Code, and must include terms to the effect that the
 * license from Licensee to its licensee is limited to the intellectual
 * property embodied in the software Licensee provides to its licensee, and
 * not to intellectual property embodied in modifications its licensee may
 * make.
 *
 * 3.3. Redistribution of Executable. Redistribution in executable form of any
 * substantial portion of the Covered Code or modification must reproduce the
 * above Copyright Notice, and the following Disclaimer and Export Compliance
 * provision in the documentation and/or other materials provided with the
 * distribution.
 *
 * 3.4. Intel retains all right, title, and interest in and to the Original
 * Intel Code.
 *
 * 3.5. Neither the name Intel nor any other trademark owned or controlled by
 * Intel shall be used in advertising or otherwise to promote the sale, use or
 * other dealings in products derived from or relating to the Covered Code
 * without prior written authorization from Intel.
 *
 * 4. Disclaimer and Export Compliance
 *
 * 4.1. INTEL MAKES NO WARRANTY OF ANY KIND REGARDING ANY SOFTWARE PROVIDED
 * HERE. ANY SOFTWARE ORIGINATING FROM INTEL OR DERIVED FROM INTEL SOFTWARE
 * IS PROVIDED "AS IS," AND INTEL WILL NOT PROVIDE ANY SUPPORT, ASSISTANCE,
 * INSTALLATION, TRAINING OR OTHER SERVICES. INTEL WILL NOT PROVIDE ANY
 * UPDATES, ENHANCEMENTS OR EXTENSIONS. INTEL SPECIFICALLY DISCLAIMS ANY
 * IMPLIED WARRANTIES OF MERCHANTABILITY, NONINFRINGEMENT AND FITNESS FOR A
 * PARTICULAR PURPOSE.
 *
 * 4.2. IN NO EVENT SHALL INTEL HAVE ANY LIABILITY TO LICENSEE, ITS LICENSEES
 * OR ANY OTHER THIRD PARTY, FOR ANY LOST PROFITS, LOST DATA, LOSS OF USE OR
 * COSTS OF PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES, OR FOR ANY INDIRECT,
 * SPECIAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THIS AGREEMENT, UNDER ANY
 * CAUSE OF ACTION OR THEORY OF LIABILITY, AND IRRESPECTIVE OF WHETHER INTEL
 * HAS ADVANCE NOTICE OF THE POSSIBILITY OF SUCH DAMAGES. THESE LIMITATIONS
 * SHALL APPLY NOTWITHSTANDING THE FAILURE OF THE ESSENTIAL PURPOSE OF ANY
 * LIMITED REMEDY.
 *
 * 4.3. Licensee shall not export, either directly or indirectly, any of this
 * software or system incorporating such software without first obtaining any
 * required license or other approval from the U. S. Department of Commerce or
 * any other agency or department of the United States Government. In the
 * event Licensee exports any such software from the United States or
 * re-exports any such software from a foreign destination, Licensee shall
 * ensure that the distribution and export/re-export of the software is in
 * compliance with all laws, regulations, orders, or other restrictions of the
 * U.S. Export Administration Regulations. Licensee agrees that neither it nor
 * any of its subsidiaries will export/re-export any technical data, process,
 * software, or service, directly or indirectly, to any country for which the
 * United States government or any agency thereof requires an export license,
 * other governmental approval, or letter of assurance, without first obtaining
 * such license, approval or letter.
 *
 *****************************************************************************
 *
 * Alternatively, you may choose to be licensed under the terms of the
 * following license:
 *
 * 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.
 *
 * 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 MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * 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 DAMAGE.
 *
 * Alternatively, you may choose to be licensed under the terms of the
 * GNU General Public License ("GPL") version 2 as published by the Free
 * Software Foundation.
 *
 *****************************************************************************/

#define _DECLARE_DT_GLOBALS

#include "aslcompiler.h"
#include "dtcompiler.h"

#define _COMPONENT          DT_COMPILER
        ACPI_MODULE_NAME    ("dtcompile")

static char                 VersionString[9];


/* Local prototypes */

static ACPI_STATUS
DtInitialize (
    void);

static ACPI_STATUS
DtCompileDataTable (
    DT_FIELD                **Field);

static void
DtInsertCompilerIds (
    DT_FIELD                *FieldList);


/******************************************************************************
 *
 * FUNCTION:    DtDoCompile
 *
 * PARAMETERS:  None
 *
 * RETURN:      Status
 *
 * DESCRIPTION: Main entry point for the data table compiler.
 *
 * Note: Assumes Gbl_Files[ASL_FILE_INPUT] is initialized and the file is
 *          open at seek offset zero.
 *
 *****************************************************************************/

ACPI_STATUS
DtDoCompile (
    void)
{
    ACPI_STATUS             Status;
    UINT8                   Event;
    DT_FIELD                *FieldList;


    /* Initialize globals */

    Status = DtInitialize ();
    if (ACPI_FAILURE (Status))
    {
        printf ("Error during compiler initialization, 0x%X\n", Status);
        return (Status);
    }

    /* Preprocessor */

    if (Gbl_PreprocessFlag)
    {
        /* Preprocessor */

        Event = UtBeginEvent ("Preprocess input file");
        PrDoPreprocess ();
        UtEndEvent (Event);

        if (Gbl_PreprocessOnly)
        {
            return (AE_OK);
        }
    }

    /*
     * Scan the input file (file is already open) and
     * build the parse tree
     */
    Event = UtBeginEvent ("Scan and parse input file");
    FieldList = DtScanFile (Gbl_Files[ASL_FILE_INPUT].Handle);
    UtEndEvent (Event);

    /* Did the parse tree get successfully constructed? */

    if (!FieldList)
    {
        /* TBD: temporary error message. Msgs should come from function above */

        DtError (ASL_ERROR, ASL_MSG_SYNTAX, NULL,
            "Input file does not appear to be an ASL or data table source file");

        Status = AE_ERROR;
        goto CleanupAndExit;
    }

    Event = UtBeginEvent ("Compile parse tree");

    /*
     * Compile the parse tree
     */
    Status = DtCompileDataTable (&FieldList);
    UtEndEvent (Event);

    if (ACPI_FAILURE (Status))
    {
        /* TBD: temporary error message. Msgs should come from function above */

        DtError (ASL_ERROR, ASL_MSG_SYNTAX, NULL,
            "Could not compile input file");

        goto CleanupAndExit;
    }

    /* Create/open the binary output file */

    Gbl_Files[ASL_FILE_AML_OUTPUT].Filename = NULL;
    Status = FlOpenAmlOutputFile (Gbl_OutputFilenamePrefix);
    if (ACPI_FAILURE (Status))
    {
        goto CleanupAndExit;
    }

    /* Write the binary, then the optional hex file */

    DtOutputBinary (Gbl_RootTable);
    HxDoHexOutput ();
    DtWriteTableToListing ();

CleanupAndExit:

    AcpiUtDeleteCaches ();
    DtDeleteCaches ();
    CmCleanupAndExit ();
    return (Status);
}


/******************************************************************************
 *
 * FUNCTION:    DtInitialize
 *
 * PARAMETERS:  None
 *
 * RETURN:      Status
 *
 * DESCRIPTION: Initialize data table compiler globals. Enables multiple
 *              compiles per invocation.
 *
 *****************************************************************************/

static ACPI_STATUS
DtInitialize (
    void)
{
    ACPI_STATUS             Status;


    Status = AcpiOsInitialize ();
    if (ACPI_FAILURE (Status))
    {
        return (Status);
    }

    Status = AcpiUtInitGlobals ();
    if (ACPI_FAILURE (Status))
    {
        return (Status);
    }

    Gbl_FieldList = NULL;
    Gbl_RootTable = NULL;
    Gbl_SubtableStack = NULL;

    sprintf (VersionString, "%X", (UINT32) ACPI_CA_VERSION);
    return (AE_OK);
}


/******************************************************************************
 *
 * FUNCTION:    DtInsertCompilerIds
 *
 * PARAMETERS:  FieldList           - Current field list pointer
 *
 * RETURN:      None
 *
 * DESCRIPTION: Insert the IDs (Name, Version) of the current compiler into
 *              the original ACPI table header.
 *
 *****************************************************************************/

static void
DtInsertCompilerIds (
    DT_FIELD                *FieldList)
{
    DT_FIELD                *Next;
    UINT32                  i;


    /*
     * Don't insert current compiler ID if requested. Used for compiler
     * debug/validation only.
     */
    if (Gbl_UseOriginalCompilerId)
    {
        return;
    }

    /* Walk to the Compiler fields at the end of the header */

    Next = FieldList;
    for (i = 0; i < 7; i++)
    {
        Next = Next->Next;
    }

    Next->Value = ASL_CREATOR_ID;
    Next->Flags = DT_FIELD_NOT_ALLOCATED;

    Next = Next->Next;
    Next->Value = VersionString;
    Next->Flags = DT_FIELD_NOT_ALLOCATED;
}


/******************************************************************************
 *
 * FUNCTION:    DtCompileDataTable
 *
 * PARAMETERS:  FieldList           - Current field list pointer
 *
 * RETURN:      Status
 *
 * DESCRIPTION: Entry point to compile one data table
 *
 *****************************************************************************/

static ACPI_STATUS
DtCompileDataTable (
    DT_FIELD                **FieldList)
{
    const ACPI_DMTABLE_DATA *TableData;
    DT_SUBTABLE             *Subtable;
    char                    *Signature;
    ACPI_TABLE_HEADER       *AcpiTableHeader;
    ACPI_STATUS             Status;
    DT_FIELD                *RootField = *FieldList;


    /* Verify that we at least have a table signature and save it */

    Signature = DtGetFieldValue (*FieldList);
    if (!Signature)
    {
        sprintf (MsgBuffer, "Expected \"%s\"", "Signature");
        DtNameError (ASL_ERROR, ASL_MSG_INVALID_FIELD_NAME,
            *FieldList, MsgBuffer);
        return (AE_ERROR);
    }

    Gbl_Signature = UtStringCacheCalloc (strlen (Signature) + 1);
    strcpy (Gbl_Signature, Signature);

    /*
     * Handle tables that don't use the common ACPI table header structure.
     * Currently, these are the FACS and RSDP. Also check for an OEMx table,
     * these tables have user-defined contents.
     */
    if (ACPI_COMPARE_NAME (Signature, ACPI_SIG_FACS))
    {
        Status = DtCompileFacs (FieldList);
        if (ACPI_FAILURE (Status))
        {
            return (Status);
        }

        DtSetTableLength ();
        return (Status);
    }
    else if (ACPI_VALIDATE_RSDP_SIG (Signature))
    {
        Status = DtCompileRsdp (FieldList);
        return (Status);
    }
    else if (ACPI_COMPARE_NAME (Signature, ACPI_SIG_S3PT))
    {
        Status = DtCompileS3pt (FieldList);
        if (ACPI_FAILURE (Status))
        {
            return (Status);
        }

        DtSetTableLength ();
        return (Status);
    }

    /*
     * All other tables must use the common ACPI table header. Insert the
     * current iASL IDs (name, version), and compile the header now.
     */
    DtInsertCompilerIds (*FieldList);

    Status = DtCompileTable (FieldList, AcpiDmTableInfoHeader,
        &Gbl_RootTable, TRUE);
    if (ACPI_FAILURE (Status))
    {
        return (Status);
    }

    DtPushSubtable (Gbl_RootTable);

    /* Validate the signature via the ACPI table list */

    TableData = AcpiDmGetTableData (Signature);
    if (!TableData || Gbl_CompileGeneric)
    {
        /* Unknown table signature and/or force generic compile */

        DtCompileGeneric ((void **) FieldList, NULL, NULL);
        goto FinishHeader;
    }

    /* Dispatch to per-table compile */

    if (TableData->CmTableHandler)
    {
        /* Complex table, has a handler */

        Status = TableData->CmTableHandler ((void **) FieldList);
        if (ACPI_FAILURE (Status))
        {
            return (Status);
        }
    }
    else if (TableData->TableInfo)
    {
        /* Simple table, just walk the info table */

        Subtable = NULL;
        Status = DtCompileTable (FieldList, TableData->TableInfo,
            &Subtable, TRUE);
        if (ACPI_FAILURE (Status))
        {
            return (Status);
        }

        DtInsertSubtable (Gbl_RootTable, Subtable);
        DtPopSubtable ();
    }
    else
    {
        DtFatal (ASL_MSG_COMPILER_INTERNAL, *FieldList,
            "Missing table dispatch info");
        return (AE_ERROR);
    }

FinishHeader:

    /* Set the final table length and then the checksum */

    DtSetTableLength ();
    AcpiTableHeader = ACPI_CAST_PTR (
        ACPI_TABLE_HEADER, Gbl_RootTable->Buffer);
    DtSetTableChecksum (&AcpiTableHeader->Checksum);

    DtDumpFieldList (RootField);
    DtDumpSubtableList ();
    return (AE_OK);
}


/******************************************************************************
 *
 * FUNCTION:    DtCompileTable
 *
 * PARAMETERS:  Field               - Current field list pointer
 *              Info                - Info table for this ACPI table
 *              RetSubtable         - Compile result of table
 *              Required            - If this subtable must exist
 *
 * RETURN:      Status
 *
 * DESCRIPTION: Compile a subtable
 *
 *****************************************************************************/

ACPI_STATUS
DtCompileTable (
    DT_FIELD                **Field,
    ACPI_DMTABLE_INFO       *Info,
    DT_SUBTABLE             **RetSubtable,
    BOOLEAN                 Required)
{
    DT_FIELD                *LocalField;
    UINT32                  Length;
    DT_SUBTABLE             *Subtable;
    DT_SUBTABLE             *InlineSubtable = NULL;
    UINT32                  FieldLength = 0;
    UINT8                   FieldType;
    UINT8                   *Buffer;
    UINT8                   *FlagBuffer = NULL;
    char                    *String;
    UINT32                  CurrentFlagByteOffset = 0;
    ACPI_STATUS             Status = AE_OK;


    if (!Field || !*Field)
    {
        return (AE_BAD_PARAMETER);
    }

    /* Ignore optional subtable if name does not match */

    if ((Info->Flags & DT_OPTIONAL) &&
        strcmp ((*Field)->Name, Info->Name))
    {
        *RetSubtable = NULL;
        return (AE_OK);
    }

    Length = DtGetSubtableLength (*Field, Info);
    if (Length == ASL_EOF)
    {
        return (AE_ERROR);
    }

    Subtable = UtSubtableCacheCalloc ();

    if (Length > 0)
    {
        String = UtStringCacheCalloc (Length);
        Subtable->Buffer = ACPI_CAST_PTR (UINT8, String);
    }

    Subtable->Length = Length;
    Subtable->TotalLength = Length;
    Buffer = Subtable->Buffer;

    LocalField = *Field;
    Subtable->Name = LocalField->Name;

    /*
     * Main loop walks the info table for this ACPI table or subtable
     */
    for (; Info->Name; Info++)
    {
        if (Info->Opcode == ACPI_DMT_EXTRA_TEXT)
        {
            continue;
        }

        if (!LocalField)
        {
            sprintf (MsgBuffer, "Found NULL field - Field name \"%s\" needed",
                Info->Name);
            DtFatal (ASL_MSG_COMPILER_INTERNAL, NULL, MsgBuffer);
            Status = AE_BAD_DATA;
            goto Error;
        }

        /* Maintain table offsets */

        LocalField->TableOffset = Gbl_CurrentTableOffset;
        FieldLength = DtGetFieldLength (LocalField, Info);
        Gbl_CurrentTableOffset += FieldLength;

        FieldType = DtGetFieldType (Info);
        Gbl_InputFieldCount++;

        switch (FieldType)
        {
        case DT_FIELD_TYPE_FLAGS_INTEGER:
            /*
             * Start of the definition of a flags field.
             * This master flags integer starts at value zero, in preparation
             * to compile and insert the flag fields from the individual bits
             */
            LocalField = LocalField->Next;
            *Field = LocalField;

            FlagBuffer = Buffer;
            CurrentFlagByteOffset = Info->Offset;
            break;

        case DT_FIELD_TYPE_FLAG:

            /* Individual Flag field, can be multiple bits */

            if (FlagBuffer)
            {
                /*
                 * We must increment the FlagBuffer when we have crossed
                 * into the next flags byte within the flags field
                 * of type DT_FIELD_TYPE_FLAGS_INTEGER.
                 */
                FlagBuffer += (Info->Offset - CurrentFlagByteOffset);
                CurrentFlagByteOffset = Info->Offset;

                DtCompileFlag (FlagBuffer, LocalField, Info);
            }
            else
            {
                /* TBD - this is an internal error */
            }

            LocalField = LocalField->Next;
            *Field = LocalField;
            break;

        case DT_FIELD_TYPE_INLINE_SUBTABLE:
            /*
             * Recursion (one level max): compile GAS (Generic Address)
             * or Notify in-line subtable
             */
            *Field = LocalField;

            switch (Info->Opcode)
            {
            case ACPI_DMT_GAS:

                Status = DtCompileTable (Field, AcpiDmTableInfoGas,
                    &InlineSubtable, TRUE);
                break;

            case ACPI_DMT_HESTNTFY:

                Status = DtCompileTable (Field, AcpiDmTableInfoHestNotify,
                    &InlineSubtable, TRUE);
                break;

            case ACPI_DMT_IORTMEM:

                Status = DtCompileTable (Field, AcpiDmTableInfoIortAcc,
                    &InlineSubtable, TRUE);
                break;

            default:
                sprintf (MsgBuffer, "Invalid DMT opcode: 0x%.2X",
                    Info->Opcode);
                DtFatal (ASL_MSG_COMPILER_INTERNAL, NULL, MsgBuffer);
                Status = AE_BAD_DATA;
                break;
            }

            if (ACPI_FAILURE (Status))
            {
                goto Error;
            }

            DtSetSubtableLength (InlineSubtable);

            memcpy (Buffer, InlineSubtable->Buffer, FieldLength);
            LocalField = *Field;
            break;

        case DT_FIELD_TYPE_LABEL:

            DtWriteFieldToListing (Buffer, LocalField, 0);
            LocalField = LocalField->Next;
            break;

        default:

            /* Normal case for most field types (Integer, String, etc.) */

            DtCompileOneField (Buffer, LocalField,
                FieldLength, FieldType, Info->Flags);

            DtWriteFieldToListing (Buffer, LocalField, FieldLength);
            LocalField = LocalField->Next;

            if (Info->Flags & DT_LENGTH)
            {
                /* Field is an Integer that will contain a subtable length */

                Subtable->LengthField = Buffer;
                Subtable->SizeOfLengthField = FieldLength;
            }
            break;
        }

        Buffer += FieldLength;
    }

    *Field = LocalField;
    *RetSubtable = Subtable;
    return (AE_OK);

Error:
    ACPI_FREE (Subtable->Buffer);
    ACPI_FREE (Subtable);
    return (Status);
}


/******************************************************************************
 *
 * FUNCTION:    DtCompileTwoSubtables
 *
 * PARAMETERS:  List                - Current field list pointer
 *              TableInfo1          - Info table 1
 *              TableInfo1          - Info table 2
 *
 * RETURN:      Status
 *
 * DESCRIPTION: Compile tables with a header and one or more same subtables.
 *              Include CPEP, EINJ, ERST, MCFG, MSCT, WDAT
 *
 *****************************************************************************/

ACPI_STATUS
DtCompileTwoSubtables (
    void                    **List,
    ACPI_DMTABLE_INFO       *TableInfo1,
    ACPI_DMTABLE_INFO       *TableInfo2)
{
    ACPI_STATUS             Status;
    DT_SUBTABLE             *Subtable;
    DT_SUBTABLE             *ParentTable;
    DT_FIELD                **PFieldList = (DT_FIELD **) List;


    Status = DtCompileTable (PFieldList, TableInfo1, &Subtable, TRUE);
    if (ACPI_FAILURE (Status))
    {
        return (Status);
    }

    ParentTable = DtPeekSubtable ();
    DtInsertSubtable (ParentTable, Subtable);

    while (*PFieldList)
    {
        Status = DtCompileTable (PFieldList, TableInfo2, &Subtable, FALSE);
        if (ACPI_FAILURE (Status))
        {
            return (Status);
        }

        DtInsertSubtable (ParentTable, Subtable);
    }

    return (AE_OK);
}


/******************************************************************************
 *
 * FUNCTION:    DtCompilePadding
 *
 * PARAMETERS:  Length              - Padding field size
 *              RetSubtable         - Compile result of table
 *
 * RETURN:      Status
 *
 * DESCRIPTION: Compile a subtable for padding purpose
 *
 *****************************************************************************/

ACPI_STATUS
DtCompilePadding (
    UINT32                  Length,
    DT_SUBTABLE             **RetSubtable)
{
    DT_SUBTABLE             *Subtable;
    /* UINT8                   *Buffer; */
    char                    *String;


    Subtable = UtSubtableCacheCalloc ();

    if (Length > 0)
    {
        String = UtStringCacheCalloc (Length);
        Subtable->Buffer = ACPI_CAST_PTR (UINT8, String);
    }

    Subtable->Length = Length;
    Subtable->TotalLength = Length;
    /* Buffer = Subtable->Buffer; */

    *RetSubtable = Subtable;
    return (AE_OK);
}