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dtcompile.c revision 1.18
      1 /******************************************************************************
      2  *
      3  * Module Name: dtcompile.c - Front-end for data table compiler
      4  *
      5  *****************************************************************************/
      6 
      7 /*
      8  * Copyright (C) 2000 - 2022, Intel Corp.
      9  * All rights reserved.
     10  *
     11  * Redistribution and use in source and binary forms, with or without
     12  * modification, are permitted provided that the following conditions
     13  * are met:
     14  * 1. Redistributions of source code must retain the above copyright
     15  *    notice, this list of conditions, and the following disclaimer,
     16  *    without modification.
     17  * 2. Redistributions in binary form must reproduce at minimum a disclaimer
     18  *    substantially similar to the "NO WARRANTY" disclaimer below
     19  *    ("Disclaimer") and any redistribution must be conditioned upon
     20  *    including a substantially similar Disclaimer requirement for further
     21  *    binary redistribution.
     22  * 3. Neither the names of the above-listed copyright holders nor the names
     23  *    of any contributors may be used to endorse or promote products derived
     24  *    from this software without specific prior written permission.
     25  *
     26  * Alternatively, this software may be distributed under the terms of the
     27  * GNU General Public License ("GPL") version 2 as published by the Free
     28  * Software Foundation.
     29  *
     30  * NO WARRANTY
     31  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
     32  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
     33  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
     34  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
     35  * HOLDERS OR CONTRIBUTORS BE LIABLE FOR SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     36  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     37  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     38  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
     39  * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
     40  * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     41  * POSSIBILITY OF SUCH DAMAGES.
     42  */
     43 
     44 #define _DECLARE_DT_GLOBALS
     45 
     46 #include "aslcompiler.h"
     47 
     48 #define _COMPONENT          DT_COMPILER
     49         ACPI_MODULE_NAME    ("dtcompile")
     50 
     51 static char                 VersionString[9];
     52 
     53 
     54 /* Local prototypes */
     55 
     56 void
     57 DtInitialize (
     58     void);
     59 
     60 static ACPI_STATUS
     61 DtCompileDataTable (
     62     DT_FIELD                **Field);
     63 
     64 static void
     65 DtInsertCompilerIds (
     66     DT_FIELD                *FieldList);
     67 
     68 
     69 /******************************************************************************
     70  *
     71  * FUNCTION:    DtDoCompile
     72  *
     73  * PARAMETERS:  None
     74  *
     75  * RETURN:      Status
     76  *
     77  * DESCRIPTION: Main entry point for the data table compiler.
     78  *
     79  * Note: Assumes AslGbl_Files[ASL_FILE_INPUT] is initialized and the file is
     80  *          open at seek offset zero.
     81  *
     82  *****************************************************************************/
     83 
     84 ACPI_STATUS
     85 DtDoCompile (
     86     void)
     87 {
     88     ACPI_STATUS             Status;
     89     UINT8                   Event;
     90     DT_FIELD                *FieldList;
     91     ASL_GLOBAL_FILE_NODE    *FileNode;
     92 
     93 
     94     /* Initialize globals */
     95 
     96     DtInitialize ();
     97 
     98     /* Preprocessor */
     99 
    100     if (AslGbl_PreprocessFlag)
    101     {
    102         /* Preprocessor */
    103 
    104         Event = UtBeginEvent ("Preprocess input file");
    105         PrDoPreprocess ();
    106         UtEndEvent (Event);
    107 
    108         if (AslGbl_PreprocessOnly)
    109         {
    110             return (AE_OK);
    111         }
    112     }
    113 
    114     /* Compile the parse tree */
    115 
    116     if (AslGbl_DtLexBisonPrototype)
    117     {
    118         Event = UtBeginEvent ("Parse data table in prototype mode");
    119 
    120         DtCompilerInitLexer (AslGbl_Files[ASL_FILE_INPUT].Handle);
    121         DtCompilerParserparse ();
    122         FieldList = AslGbl_FieldList;
    123         DtCompilerTerminateLexer ();
    124 
    125         UtEndEvent (Event);
    126     }
    127     else
    128     {
    129         /*
    130          * Scan the input file (file is already open) and
    131          * build the parse tree
    132          */
    133         Event = UtBeginEvent ("Scan and parse input file");
    134         FieldList = DtScanFile (AslGbl_Files[ASL_FILE_INPUT].Handle);
    135         UtEndEvent (Event);
    136     }
    137 
    138     /* Did the parse tree get successfully constructed? */
    139 
    140     if (!FieldList)
    141     {
    142         /* TBD: temporary error message. Msgs should come from function above */
    143 
    144         DtError (ASL_ERROR, ASL_MSG_SYNTAX, NULL,
    145             "Input file does not appear to be an ASL or data table source file");
    146 
    147         return (AE_ERROR);
    148     }
    149 
    150     Event = UtBeginEvent ("Compile parse tree");
    151 
    152     Status = DtCompileDataTable (&FieldList);
    153     UtEndEvent (Event);
    154 
    155     FileNode = FlGetCurrentFileNode ();
    156 
    157     FileNode->TotalLineCount = AslGbl_CurrentLineNumber;
    158     FileNode->OriginalInputFileSize = AslGbl_InputByteCount;
    159     DbgPrint (ASL_PARSE_OUTPUT, "Line count: %u input file size: %u\n",
    160             FileNode->TotalLineCount, FileNode->OriginalInputFileSize);
    161 
    162     if (ACPI_FAILURE (Status))
    163     {
    164         FileNode->ParserErrorDetected = TRUE;
    165 
    166         /* TBD: temporary error message. Msgs should come from function above */
    167 
    168         DtError (ASL_ERROR, ASL_MSG_SYNTAX, NULL,
    169             "Could not compile input file");
    170 
    171         return (Status);
    172     }
    173 
    174     /* Create/open the binary output file */
    175 
    176     AslGbl_Files[ASL_FILE_AML_OUTPUT].Filename = NULL;
    177     Status = FlOpenAmlOutputFile (AslGbl_OutputFilenamePrefix);
    178     if (ACPI_FAILURE (Status))
    179     {
    180         return (Status);
    181     }
    182 
    183     /* Write the binary, then the optional hex file */
    184 
    185     DtOutputBinary (AslGbl_RootTable);
    186     HxDoHexOutput ();
    187     DtWriteTableToListing ();
    188 
    189     /* Save the compile time statistics to the current file node */
    190 
    191     FileNode->TotalFields = AslGbl_InputFieldCount;
    192     FileNode->OutputByteLength = AslGbl_TableLength;
    193 
    194     return (Status);
    195 }
    196 
    197 
    198 /******************************************************************************
    199  *
    200  * FUNCTION:    DtInitialize
    201  *
    202  * PARAMETERS:  None
    203  *
    204  * RETURN:      Status
    205  *
    206  * DESCRIPTION: Initialize data table compiler globals. Enables multiple
    207  *              compiles per invocation.
    208  *
    209  *****************************************************************************/
    210 
    211 void
    212 DtInitialize (
    213     void)
    214 {
    215 
    216 
    217     AcpiUtSetIntegerWidth (2); /* Set width to 64 bits */
    218 
    219     AslGbl_FieldList = NULL;
    220     AslGbl_RootTable = NULL;
    221     AslGbl_SubtableStack = NULL;
    222 
    223     snprintf (VersionString, sizeof(VersionString), "%X",
    224 	(UINT32) ACPI_CA_VERSION);
    225     return;
    226 }
    227 
    228 
    229 /******************************************************************************
    230  *
    231  * FUNCTION:    DtInsertCompilerIds
    232  *
    233  * PARAMETERS:  FieldList           - Current field list pointer
    234  *
    235  * RETURN:      None
    236  *
    237  * DESCRIPTION: Insert the IDs (Name, Version) of the current compiler into
    238  *              the original ACPI table header.
    239  *
    240  *****************************************************************************/
    241 
    242 static void
    243 DtInsertCompilerIds (
    244     DT_FIELD                *FieldList)
    245 {
    246     DT_FIELD                *Next;
    247     UINT32                  i;
    248 
    249 
    250     /*
    251      * Don't insert current compiler ID if requested. Used for compiler
    252      * debug/validation only.
    253      */
    254     if (AslGbl_UseOriginalCompilerId)
    255     {
    256         return;
    257     }
    258 
    259     /* Walk to the Compiler fields at the end of the header */
    260 
    261     Next = FieldList;
    262     for (i = 0; i < 7; i++)
    263     {
    264         Next = Next->Next;
    265     }
    266 
    267     Next->Value = ASL_CREATOR_ID;
    268     Next->Flags = DT_FIELD_NOT_ALLOCATED;
    269 
    270     Next = Next->Next;
    271     Next->Value = VersionString;
    272     Next->Flags = DT_FIELD_NOT_ALLOCATED;
    273 }
    274 
    275 
    276 /******************************************************************************
    277  *
    278  * FUNCTION:    DtCompileDataTable
    279  *
    280  * PARAMETERS:  FieldList           - Current field list pointer
    281  *
    282  * RETURN:      Status
    283  *
    284  * DESCRIPTION: Entry point to compile one data table
    285  *
    286  *****************************************************************************/
    287 
    288 static ACPI_STATUS
    289 DtCompileDataTable (
    290     DT_FIELD                **FieldList)
    291 {
    292     const ACPI_DMTABLE_DATA *TableData;
    293     DT_SUBTABLE             *Subtable;
    294     char                    *Signature;
    295     ACPI_TABLE_HEADER       *AcpiTableHeader;
    296     ACPI_STATUS             Status;
    297     DT_FIELD                *RootField = *FieldList;
    298 
    299 
    300     /* Verify that we at least have a table signature and save it */
    301 
    302     Signature = DtGetFieldValue (*FieldList);
    303     if (!Signature)
    304     {
    305         snprintf (AslGbl_MsgBuffer, sizeof(AslGbl_MsgBuffer), "Expected \"%s\"", "Signature");
    306         DtNameError (ASL_ERROR, ASL_MSG_INVALID_FIELD_NAME,
    307             *FieldList, AslGbl_MsgBuffer);
    308         return (AE_ERROR);
    309     }
    310 
    311     AslGbl_Signature = UtLocalCacheCalloc (strlen (Signature) + 1);
    312     strcpy (AslGbl_Signature, Signature);
    313 
    314     /*
    315      * Handle tables that don't use the common ACPI table header structure.
    316      * Currently, these are the FACS and RSDP. Also check for an OEMx table,
    317      * these tables have user-defined contents.
    318      */
    319     if (ACPI_COMPARE_NAMESEG (Signature, ACPI_SIG_FACS))
    320     {
    321         Status = DtCompileFacs (FieldList);
    322         if (ACPI_FAILURE (Status))
    323         {
    324             return (Status);
    325         }
    326 
    327         DtSetTableLength ();
    328         return (Status);
    329     }
    330     else if (ACPI_VALIDATE_RSDP_SIG (Signature))
    331     {
    332         Status = DtCompileRsdp (FieldList);
    333         return (Status);
    334     }
    335     else if (ACPI_COMPARE_NAMESEG (Signature, ACPI_SIG_S3PT))
    336     {
    337         Status = DtCompileS3pt (FieldList);
    338         if (ACPI_FAILURE (Status))
    339         {
    340             return (Status);
    341         }
    342 
    343         DtSetTableLength ();
    344         return (Status);
    345     }
    346 
    347     /*
    348      * All other tables must use the common ACPI table header. Insert the
    349      * current iASL IDs (name, version), and compile the header now.
    350      */
    351     DtInsertCompilerIds (*FieldList);
    352 
    353     Status = DtCompileTable (FieldList, AcpiDmTableInfoHeader,
    354         &AslGbl_RootTable);
    355     if (ACPI_FAILURE (Status))
    356     {
    357         return (Status);
    358     }
    359 
    360     DtPushSubtable (AslGbl_RootTable);
    361 
    362     /* Validate the signature via the ACPI table list */
    363 
    364     TableData = AcpiDmGetTableData (Signature);
    365     if (!TableData || AslGbl_CompileGeneric)
    366     {
    367         /* Unknown table signature and/or force generic compile */
    368 
    369         DtCompileGeneric ((void **) FieldList, NULL, NULL);
    370         goto FinishHeader;
    371     }
    372 
    373     /* Dispatch to per-table compile */
    374 
    375     if (TableData->CmTableHandler)
    376     {
    377         /* Complex table, has a handler */
    378 
    379         Status = TableData->CmTableHandler ((void **) FieldList);
    380         if (ACPI_FAILURE (Status))
    381         {
    382             return (Status);
    383         }
    384     }
    385     else if (TableData->TableInfo)
    386     {
    387         /* Simple table, just walk the info table, unless its empty */
    388 
    389         if (FieldList && *FieldList)
    390         {
    391             Subtable = NULL;
    392             Status = DtCompileTable (FieldList, TableData->TableInfo,
    393                 &Subtable);
    394             if (ACPI_FAILURE (Status))
    395             {
    396                 return (Status);
    397             }
    398 
    399             DtInsertSubtable (AslGbl_RootTable, Subtable);
    400             DtPopSubtable ();
    401         }
    402     }
    403     else
    404     {
    405         DtFatal (ASL_MSG_COMPILER_INTERNAL, *FieldList,
    406             "Missing table dispatch info");
    407         return (AE_ERROR);
    408     }
    409 
    410 FinishHeader:
    411 
    412     /* Set the final table length and then the checksum */
    413 
    414     DtSetTableLength ();
    415     AcpiTableHeader = ACPI_CAST_PTR (
    416         ACPI_TABLE_HEADER, AslGbl_RootTable->Buffer);
    417     DtSetTableChecksum (&AcpiTableHeader->Checksum);
    418 
    419     DtDumpFieldList (RootField);
    420     DtDumpSubtableList ();
    421     return (AE_OK);
    422 }
    423 
    424 
    425 /******************************************************************************
    426  *
    427  * FUNCTION:    DtCompileTable
    428  *
    429  * PARAMETERS:  Field               - Current field list pointer
    430  *              Info                - Info table for this ACPI table
    431  *              RetSubtable         - Compile result of table
    432  *
    433  * RETURN:      Status
    434  *
    435  * DESCRIPTION: Compile a subtable
    436  *
    437  *****************************************************************************/
    438 
    439 ACPI_STATUS
    440 DtCompileTable (
    441     DT_FIELD                **Field,
    442     ACPI_DMTABLE_INFO       *Info,
    443     DT_SUBTABLE             **RetSubtable)
    444 {
    445     DT_FIELD                *LocalField;
    446     UINT32                  Length;
    447     DT_SUBTABLE             *Subtable;
    448     DT_SUBTABLE             *InlineSubtable = NULL;
    449     UINT32                  FieldLength = 0;
    450     UINT8                   FieldType;
    451     UINT8                   *Buffer;
    452     UINT8                   *FlagBuffer = NULL;
    453     char                    *String;
    454     UINT32                  CurrentFlagByteOffset = 0;
    455     ACPI_STATUS             Status = AE_OK;
    456 
    457 
    458     if (!Field || !Info)
    459     {
    460         return (AE_BAD_PARAMETER);
    461     }
    462     if (!*Field)
    463     {
    464         /*
    465          * The field list is empty, this means that we are out of fields to
    466          * parse. In other words, we are at the end of the table.
    467          */
    468         return (AE_END_OF_TABLE);
    469     }
    470 
    471     /* Ignore optional subtable if name does not match */
    472 
    473     if ((Info->Flags & DT_OPTIONAL) &&
    474         strcmp ((*Field)->Name, Info->Name))
    475     {
    476         *RetSubtable = NULL;
    477         return (AE_OK);
    478     }
    479 
    480     Length = DtGetSubtableLength (*Field, Info);
    481     if (Length == ASL_EOF)
    482     {
    483         return (AE_ERROR);
    484     }
    485 
    486     Subtable = UtSubtableCacheCalloc ();
    487 
    488     if (Length > 0)
    489     {
    490         String = UtLocalCacheCalloc (Length);
    491         Subtable->Buffer = ACPI_CAST_PTR (UINT8, String);
    492     }
    493 
    494     Subtable->Length = Length;
    495     Subtable->TotalLength = Length;
    496     Buffer = Subtable->Buffer;
    497 
    498     LocalField = *Field;
    499     Subtable->Name = LocalField->Name;
    500 
    501     /*
    502      * Main loop walks the info table for this ACPI table or subtable
    503      */
    504     for (; Info->Name; Info++)
    505     {
    506         if (Info->Opcode == ACPI_DMT_EXTRA_TEXT)
    507         {
    508             continue;
    509         }
    510 
    511         if (!LocalField)
    512         {
    513             snprintf (AslGbl_MsgBuffer, sizeof(AslGbl_MsgBuffer), "Found NULL field - Field name \"%s\" needed",
    514                 Info->Name);
    515             DtFatal (ASL_MSG_COMPILER_INTERNAL, NULL, AslGbl_MsgBuffer);
    516             Status = AE_BAD_DATA;
    517             goto Error;
    518         }
    519 
    520         /* Maintain table offsets */
    521 
    522         LocalField->TableOffset = AslGbl_CurrentTableOffset;
    523         FieldLength = DtGetFieldLength (LocalField, Info);
    524         AslGbl_CurrentTableOffset += FieldLength;
    525 
    526         FieldType = DtGetFieldType (Info);
    527         AslGbl_InputFieldCount++;
    528 
    529         if (FieldType != DT_FIELD_TYPE_INLINE_SUBTABLE &&
    530             strcmp (Info->Name, LocalField->Name))
    531         {
    532             sprintf (AslGbl_MsgBuffer, "found \"%s\" expected \"%s\"",
    533                 LocalField->Name, Info->Name);
    534             DtError (ASL_ERROR, ASL_MSG_INVALID_LABEL, LocalField, AslGbl_MsgBuffer);
    535         }
    536 
    537         switch (FieldType)
    538         {
    539         case DT_FIELD_TYPE_FLAGS_INTEGER:
    540             /*
    541              * Start of the definition of a flags field.
    542              * This master flags integer starts at value zero, in preparation
    543              * to compile and insert the flag fields from the individual bits
    544              */
    545             LocalField = LocalField->Next;
    546             *Field = LocalField;
    547 
    548             FlagBuffer = Buffer;
    549             CurrentFlagByteOffset = Info->Offset;
    550             break;
    551 
    552         case DT_FIELD_TYPE_FLAG:
    553 
    554             /* Individual Flag field, can be multiple bits */
    555 
    556             if (FlagBuffer)
    557             {
    558                 /*
    559                  * We must increment the FlagBuffer when we have crossed
    560                  * into the next flags byte within the flags field
    561                  * of type DT_FIELD_TYPE_FLAGS_INTEGER.
    562                  */
    563                 FlagBuffer += (Info->Offset - CurrentFlagByteOffset);
    564                 CurrentFlagByteOffset = Info->Offset;
    565 
    566                 DtCompileFlag (FlagBuffer, LocalField, Info);
    567             }
    568             else
    569             {
    570                 /* TBD - this is an internal error */
    571             }
    572 
    573             LocalField = LocalField->Next;
    574             *Field = LocalField;
    575             break;
    576 
    577         case DT_FIELD_TYPE_INLINE_SUBTABLE:
    578             /*
    579              * Recursion (one level max): compile GAS (Generic Address)
    580              * or Notify in-line subtable
    581              */
    582             *Field = LocalField;
    583 
    584             switch (Info->Opcode)
    585             {
    586             case ACPI_DMT_GAS:
    587 
    588                 Status = DtCompileTable (Field, AcpiDmTableInfoGas,
    589                     &InlineSubtable);
    590                 break;
    591 
    592             case ACPI_DMT_HESTNTFY:
    593 
    594                 Status = DtCompileTable (Field, AcpiDmTableInfoHestNotify,
    595                     &InlineSubtable);
    596                 break;
    597 
    598             case ACPI_DMT_IORTMEM:
    599 
    600                 Status = DtCompileTable (Field, AcpiDmTableInfoIortAcc,
    601                     &InlineSubtable);
    602                 break;
    603 
    604             default:
    605                 sprintf (AslGbl_MsgBuffer, "Invalid DMT opcode: 0x%.2X",
    606                     Info->Opcode);
    607                 DtFatal (ASL_MSG_COMPILER_INTERNAL, NULL, AslGbl_MsgBuffer);
    608                 Status = AE_BAD_DATA;
    609                 break;
    610             }
    611 
    612             if (ACPI_FAILURE (Status))
    613             {
    614                 goto Error;
    615             }
    616 
    617             DtSetSubtableLength (InlineSubtable);
    618 
    619             memcpy (Buffer, InlineSubtable->Buffer, FieldLength);
    620             LocalField = *Field;
    621             break;
    622 
    623         case DT_FIELD_TYPE_LABEL:
    624 
    625             DtWriteFieldToListing (Buffer, LocalField, 0);
    626             LocalField = LocalField->Next;
    627             break;
    628 
    629         default:
    630 
    631             /* Normal case for most field types (Integer, String, etc.) */
    632 
    633             DtCompileOneField (Buffer, LocalField,
    634                 FieldLength, FieldType, Info->Flags);
    635 
    636             DtWriteFieldToListing (Buffer, LocalField, FieldLength);
    637             LocalField = LocalField->Next;
    638 
    639             if (Info->Flags & DT_LENGTH)
    640             {
    641                 /* Field is an Integer that will contain a subtable length */
    642 
    643                 Subtable->LengthField = Buffer;
    644                 Subtable->SizeOfLengthField = FieldLength;
    645             }
    646             break;
    647         }
    648 
    649         Buffer += FieldLength;
    650     }
    651 
    652     *Field = LocalField;
    653     *RetSubtable = Subtable;
    654     return (AE_OK);
    655 
    656 Error:
    657     ACPI_FREE (Subtable->Buffer);
    658     ACPI_FREE (Subtable);
    659     return (Status);
    660 }
    661 
    662 
    663 /******************************************************************************
    664  *
    665  * FUNCTION:    DtCompileTwoSubtables
    666  *
    667  * PARAMETERS:  List                - Current field list pointer
    668  *              TableInfo1          - Info table 1
    669  *              TableInfo1          - Info table 2
    670  *
    671  * RETURN:      Status
    672  *
    673  * DESCRIPTION: Compile tables with a header and one or more same subtables.
    674  *              Include CPEP, EINJ, ERST, MCFG, MSCT, WDAT
    675  *
    676  *****************************************************************************/
    677 
    678 ACPI_STATUS
    679 DtCompileTwoSubtables (
    680     void                    **List,
    681     ACPI_DMTABLE_INFO       *TableInfo1,
    682     ACPI_DMTABLE_INFO       *TableInfo2)
    683 {
    684     ACPI_STATUS             Status;
    685     DT_SUBTABLE             *Subtable;
    686     DT_SUBTABLE             *ParentTable;
    687     DT_FIELD                **PFieldList = (DT_FIELD **) List;
    688 
    689 
    690     Status = DtCompileTable (PFieldList, TableInfo1, &Subtable);
    691     if (ACPI_FAILURE (Status))
    692     {
    693         return (Status);
    694     }
    695 
    696     ParentTable = DtPeekSubtable ();
    697     DtInsertSubtable (ParentTable, Subtable);
    698 
    699     while (*PFieldList)
    700     {
    701         Status = DtCompileTable (PFieldList, TableInfo2, &Subtable);
    702         if (ACPI_FAILURE (Status))
    703         {
    704             return (Status);
    705         }
    706 
    707         DtInsertSubtable (ParentTable, Subtable);
    708     }
    709 
    710     return (AE_OK);
    711 }
    712 
    713 
    714 /******************************************************************************
    715  *
    716  * FUNCTION:    DtCompilePadding
    717  *
    718  * PARAMETERS:  Length              - Padding field size
    719  *              RetSubtable         - Compile result of table
    720  *
    721  * RETURN:      Status
    722  *
    723  * DESCRIPTION: Compile a subtable for padding purpose
    724  *
    725  *****************************************************************************/
    726 
    727 ACPI_STATUS
    728 DtCompilePadding (
    729     UINT32                  Length,
    730     DT_SUBTABLE             **RetSubtable)
    731 {
    732     DT_SUBTABLE             *Subtable;
    733     /* UINT8                   *Buffer; */
    734     char                    *String;
    735 
    736 
    737     Subtable = UtSubtableCacheCalloc ();
    738 
    739     if (Length > 0)
    740     {
    741         String = UtLocalCacheCalloc (Length);
    742         Subtable->Buffer = ACPI_CAST_PTR (UINT8, String);
    743     }
    744 
    745     Subtable->Length = Length;
    746     Subtable->TotalLength = Length;
    747     /* Buffer = Subtable->Buffer; */
    748 
    749     *RetSubtable = Subtable;
    750     return (AE_OK);
    751 }
    752