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dtutils.c revision 1.15.2.1
      1 /******************************************************************************
      2  *
      3  * Module Name: dtutils.c - Utility routines for the data table compiler
      4  *
      5  *****************************************************************************/
      6 
      7 /*
      8  * Copyright (C) 2000 - 2021, 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 #include "aslcompiler.h"
     45 #include "actables.h"
     46 
     47 #define _COMPONENT          DT_COMPILER
     48         ACPI_MODULE_NAME    ("dtutils")
     49 
     50 /* Local prototypes */
     51 
     52 static void
     53 DtSum (
     54     DT_SUBTABLE             *Subtable,
     55     void                    *Context,
     56     void                    *ReturnValue);
     57 
     58 
     59 /******************************************************************************
     60  *
     61  * FUNCTION:    DtError
     62  *
     63  * PARAMETERS:  Level               - Seriousness (Warning/error, etc.)
     64  *              MessageId           - Index into global message buffer
     65  *              Op                  - Parse node where error happened
     66  *              ExtraMessage        - additional error message
     67  *
     68  * RETURN:      None
     69  *
     70  * DESCRIPTION: Common error interface for data table compiler
     71  *
     72  *****************************************************************************/
     73 
     74 void
     75 DtError (
     76     UINT8                   Level,
     77     UINT16                  MessageId,
     78     DT_FIELD                *FieldObject,
     79     char                    *ExtraMessage)
     80 {
     81     UINT32                  Line = 0;
     82 
     83 
     84     /* Field object could be NULL */
     85 
     86     if (FieldObject)
     87     {
     88         Line = FieldObject->Line;
     89     }
     90 
     91     /* Check if user wants to ignore this exception */
     92 
     93     if (AslIsExceptionIgnored (AslGbl_Files[ASL_FILE_INPUT].Filename,
     94         Line, Level, MessageId))
     95     {
     96         return;
     97     }
     98 
     99     if (FieldObject)
    100     {
    101         AslCommonError (Level, MessageId,
    102             FieldObject->Line,
    103             FieldObject->Line,
    104             FieldObject->ByteOffset,
    105             FieldObject->Column,
    106             AslGbl_Files[ASL_FILE_INPUT].Filename, ExtraMessage);
    107     }
    108     else
    109     {
    110         AslCommonError (Level, MessageId, 0,
    111             0, 0, 0, 0, ExtraMessage);
    112     }
    113 }
    114 
    115 
    116 /******************************************************************************
    117  *
    118  * FUNCTION:    DtNameError
    119  *
    120  * PARAMETERS:  Level               - Seriousness (Warning/error, etc.)
    121  *              MessageId           - Index into global message buffer
    122  *              Op                  - Parse node where error happened
    123  *              ExtraMessage        - additional error message
    124  *
    125  * RETURN:      None
    126  *
    127  * DESCRIPTION: Error interface for named objects
    128  *
    129  *****************************************************************************/
    130 
    131 void
    132 DtNameError (
    133     UINT8                   Level,
    134     UINT16                  MessageId,
    135     DT_FIELD                *FieldObject,
    136     char                    *ExtraMessage)
    137 {
    138 
    139     switch (Level)
    140     {
    141     case ASL_WARNING2:
    142     case ASL_WARNING3:
    143 
    144         if (AslGbl_WarningLevel < Level)
    145         {
    146             return;
    147         }
    148         break;
    149 
    150     default:
    151 
    152         break;
    153     }
    154 
    155     if (FieldObject)
    156     {
    157         AslCommonError (Level, MessageId,
    158             FieldObject->Line,
    159             FieldObject->Line,
    160             FieldObject->ByteOffset,
    161             FieldObject->NameColumn,
    162             AslGbl_Files[ASL_FILE_INPUT].Filename, ExtraMessage);
    163     }
    164     else
    165     {
    166         AslCommonError (Level, MessageId, 0,
    167             0, 0, 0, 0, ExtraMessage);
    168     }
    169 }
    170 
    171 
    172 /*******************************************************************************
    173  *
    174  * FUNCTION:    DtFatal
    175  *
    176  * PARAMETERS:  None
    177  *
    178  * RETURN:      None
    179  *
    180  * DESCRIPTION: Dump the error log and abort the compiler. Used for serious
    181  *              compile or I/O errors
    182  *
    183  ******************************************************************************/
    184 
    185 void
    186 DtFatal (
    187     UINT16                  MessageId,
    188     DT_FIELD                *FieldObject,
    189     char                    *ExtraMessage)
    190 {
    191 
    192     DtError (ASL_ERROR, MessageId, FieldObject, ExtraMessage);
    193 
    194 /*
    195  * TBD: remove this entire function, DtFatal
    196  *
    197  * We cannot abort the compiler on error, because we may be compiling a
    198  * list of files. We must move on to the next file.
    199  */
    200 #ifdef __OBSOLETE
    201     CmCleanupAndExit ();
    202     exit (1);
    203 #endif
    204 }
    205 
    206 
    207 /*******************************************************************************
    208  *
    209  * FUNCTION:    DtDoConstant
    210  *
    211  * PARAMETERS:  String              - Only hex constants are supported,
    212  *                                    regardless of whether the 0x prefix
    213  *                                    is used
    214  *
    215  * RETURN:      Converted Integer
    216  *
    217  * DESCRIPTION: Convert a string to an integer, with overflow/error checking.
    218  *
    219  ******************************************************************************/
    220 
    221 UINT64
    222 DtDoConstant (
    223     char                    *String)
    224 {
    225     UINT64                  ConvertedInteger;
    226 
    227 
    228     /*
    229      * TBD: The ImplicitStrtoul64 function does not report overflow
    230      * conditions. The input string is simply truncated. If it is
    231      * desired to report overflow to the table compiler, this should
    232      * somehow be added here. Note: integers that are prefixed with 0x
    233      * or not are both hex integers.
    234      */
    235     ConvertedInteger = AcpiUtImplicitStrtoul64 (String);
    236     return (ConvertedInteger);
    237 }
    238 
    239 /******************************************************************************
    240  *
    241  * FUNCTION:    DtGetFieldValue
    242  *
    243  * PARAMETERS:  Field               - Current field list pointer
    244  *
    245  * RETURN:      Field value
    246  *
    247  * DESCRIPTION: Get field value
    248  *
    249  *****************************************************************************/
    250 
    251 char *
    252 DtGetFieldValue (
    253     DT_FIELD                *Field)
    254 {
    255     if (!Field)
    256     {
    257         return (NULL);
    258     }
    259 
    260     return (Field->Value);
    261 }
    262 
    263 
    264 /******************************************************************************
    265  *
    266  * FUNCTION:    DtGetFieldType
    267  *
    268  * PARAMETERS:  Info                - Data table info
    269  *
    270  * RETURN:      Field type
    271  *
    272  * DESCRIPTION: Get field type
    273  *
    274  *****************************************************************************/
    275 
    276 UINT8
    277 DtGetFieldType (
    278     ACPI_DMTABLE_INFO       *Info)
    279 {
    280     UINT8                   Type;
    281 
    282 
    283     /* DT_FLAG means that this is the start of a block of flag bits */
    284     /* TBD - we can make these a separate opcode later */
    285 
    286     if (Info->Flags & DT_FLAG)
    287     {
    288         return (DT_FIELD_TYPE_FLAGS_INTEGER);
    289     }
    290 
    291     /* Type is based upon the opcode for this field in the info table */
    292 
    293     switch (Info->Opcode)
    294     {
    295     case ACPI_DMT_FLAG0:
    296     case ACPI_DMT_FLAG1:
    297     case ACPI_DMT_FLAG2:
    298     case ACPI_DMT_FLAG3:
    299     case ACPI_DMT_FLAG4:
    300     case ACPI_DMT_FLAG5:
    301     case ACPI_DMT_FLAG6:
    302     case ACPI_DMT_FLAG7:
    303     case ACPI_DMT_FLAGS0:
    304     case ACPI_DMT_FLAGS1:
    305     case ACPI_DMT_FLAGS2:
    306     case ACPI_DMT_FLAGS4:
    307     case ACPI_DMT_FLAGS4_0:
    308     case ACPI_DMT_FLAGS4_4:
    309     case ACPI_DMT_FLAGS4_8:
    310     case ACPI_DMT_FLAGS4_12:
    311     case ACPI_DMT_FLAGS16_16:
    312 
    313         Type = DT_FIELD_TYPE_FLAG;
    314         break;
    315 
    316     case ACPI_DMT_NAME4:
    317     case ACPI_DMT_SIG:
    318     case ACPI_DMT_NAME6:
    319     case ACPI_DMT_NAME8:
    320     case ACPI_DMT_STRING:
    321 
    322         Type = DT_FIELD_TYPE_STRING;
    323         break;
    324 
    325     case ACPI_DMT_BUFFER:
    326     case ACPI_DMT_RAW_BUFFER:
    327     case ACPI_DMT_BUF7:
    328     case ACPI_DMT_BUF10:
    329     case ACPI_DMT_BUF12:
    330     case ACPI_DMT_BUF16:
    331     case ACPI_DMT_BUF128:
    332     case ACPI_DMT_PCI_PATH:
    333     case ACPI_DMT_PMTT_VENDOR:
    334 
    335         Type = DT_FIELD_TYPE_BUFFER;
    336         break;
    337 
    338     case ACPI_DMT_GAS:
    339     case ACPI_DMT_HESTNTFY:
    340     case ACPI_DMT_IORTMEM:
    341 
    342         Type = DT_FIELD_TYPE_INLINE_SUBTABLE;
    343         break;
    344 
    345     case ACPI_DMT_UNICODE:
    346 
    347         Type = DT_FIELD_TYPE_UNICODE;
    348         break;
    349 
    350     case ACPI_DMT_UUID:
    351 
    352         Type = DT_FIELD_TYPE_UUID;
    353         break;
    354 
    355     case ACPI_DMT_DEVICE_PATH:
    356 
    357         Type = DT_FIELD_TYPE_DEVICE_PATH;
    358         break;
    359 
    360     case ACPI_DMT_LABEL:
    361 
    362         Type = DT_FIELD_TYPE_LABEL;
    363         break;
    364 
    365     default:
    366 
    367         Type = DT_FIELD_TYPE_INTEGER;
    368         break;
    369     }
    370 
    371     return (Type);
    372 }
    373 
    374 
    375 /******************************************************************************
    376  *
    377  * FUNCTION:    DtGetBufferLength
    378  *
    379  * PARAMETERS:  Buffer              - List of integers,
    380  *                                    for example "10 3A 4F 2E"
    381  *
    382  * RETURN:      Count of integer
    383  *
    384  * DESCRIPTION: Get length of bytes needed to store the integers
    385  *
    386  *****************************************************************************/
    387 
    388 UINT32
    389 DtGetBufferLength (
    390     char                    *Buffer)
    391 {
    392     UINT32                  ByteLength = 0;
    393 
    394 
    395     while (*Buffer)
    396     {
    397         if (*Buffer == ' ')
    398         {
    399             ByteLength++;
    400 
    401             while (*Buffer == ' ')
    402             {
    403                 Buffer++;
    404             }
    405         }
    406 
    407         Buffer++;
    408     }
    409 
    410     return (++ByteLength);
    411 }
    412 
    413 
    414 /******************************************************************************
    415  *
    416  * FUNCTION:    DtGetFieldLength
    417  *
    418  * PARAMETERS:  Field               - Current field
    419  *              Info                - Data table info
    420  *
    421  * RETURN:      Field length
    422  *
    423  * DESCRIPTION: Get length of bytes needed to compile the field
    424  *
    425  * Note: This function must remain in sync with AcpiDmDumpTable.
    426  *
    427  *****************************************************************************/
    428 
    429 UINT32
    430 DtGetFieldLength (
    431     DT_FIELD                *Field,
    432     ACPI_DMTABLE_INFO       *Info)
    433 {
    434     UINT32                  ByteLength = 0;
    435     char                    *Value;
    436 
    437 
    438     /* Length is based upon the opcode for this field in the info table */
    439 
    440     switch (Info->Opcode)
    441     {
    442     case ACPI_DMT_FLAG0:
    443     case ACPI_DMT_FLAG1:
    444     case ACPI_DMT_FLAG2:
    445     case ACPI_DMT_FLAG3:
    446     case ACPI_DMT_FLAG4:
    447     case ACPI_DMT_FLAG5:
    448     case ACPI_DMT_FLAG6:
    449     case ACPI_DMT_FLAG7:
    450     case ACPI_DMT_FLAGS0:
    451     case ACPI_DMT_FLAGS1:
    452     case ACPI_DMT_FLAGS2:
    453     case ACPI_DMT_FLAGS4:
    454     case ACPI_DMT_FLAGS4_0:
    455     case ACPI_DMT_FLAGS4_4:
    456     case ACPI_DMT_FLAGS4_8:
    457     case ACPI_DMT_FLAGS4_12:
    458     case ACPI_DMT_FLAGS16_16:
    459     case ACPI_DMT_LABEL:
    460     case ACPI_DMT_EXTRA_TEXT:
    461 
    462         ByteLength = 0;
    463         break;
    464 
    465     case ACPI_DMT_UINT8:
    466     case ACPI_DMT_CHKSUM:
    467     case ACPI_DMT_SPACEID:
    468     case ACPI_DMT_ACCWIDTH:
    469     case ACPI_DMT_CEDT:
    470     case ACPI_DMT_IVRS:
    471     case ACPI_DMT_GTDT:
    472     case ACPI_DMT_MADT:
    473     case ACPI_DMT_PCCT:
    474     case ACPI_DMT_PMTT:
    475     case ACPI_DMT_PPTT:
    476     case ACPI_DMT_SDEV:
    477     case ACPI_DMT_SRAT:
    478     case ACPI_DMT_ASF:
    479     case ACPI_DMT_HESTNTYP:
    480     case ACPI_DMT_FADTPM:
    481     case ACPI_DMT_EINJACT:
    482     case ACPI_DMT_EINJINST:
    483     case ACPI_DMT_ERSTACT:
    484     case ACPI_DMT_ERSTINST:
    485     case ACPI_DMT_DMAR_SCOPE:
    486     case ACPI_DMT_VIOT:
    487 
    488         ByteLength = 1;
    489         break;
    490 
    491     case ACPI_DMT_UINT16:
    492     case ACPI_DMT_DMAR:
    493     case ACPI_DMT_HEST:
    494     case ACPI_DMT_HMAT:
    495     case ACPI_DMT_NFIT:
    496     case ACPI_DMT_PCI_PATH:
    497     case ACPI_DMT_PHAT:
    498 
    499         ByteLength = 2;
    500         break;
    501 
    502     case ACPI_DMT_UINT24:
    503 
    504         ByteLength = 3;
    505         break;
    506 
    507     case ACPI_DMT_UINT32:
    508     case ACPI_DMT_NAME4:
    509     case ACPI_DMT_SIG:
    510     case ACPI_DMT_LPIT:
    511     case ACPI_DMT_TPM2:
    512 
    513         ByteLength = 4;
    514         break;
    515 
    516     case ACPI_DMT_UINT40:
    517 
    518         ByteLength = 5;
    519         break;
    520 
    521     case ACPI_DMT_UINT48:
    522     case ACPI_DMT_NAME6:
    523 
    524         ByteLength = 6;
    525         break;
    526 
    527     case ACPI_DMT_UINT56:
    528     case ACPI_DMT_BUF7:
    529 
    530         ByteLength = 7;
    531         break;
    532 
    533     case ACPI_DMT_UINT64:
    534     case ACPI_DMT_NAME8:
    535 
    536         ByteLength = 8;
    537         break;
    538 
    539     case ACPI_DMT_STRING:
    540 
    541         Value = DtGetFieldValue (Field);
    542         if (Value)
    543         {
    544             ByteLength = strlen (Value) + 1;
    545         }
    546         else
    547         {   /* At this point, this is a fatal error */
    548 
    549             snprintf (AslGbl_MsgBuffer, sizeof(AslGbl_MsgBuffer), "Expected \"%s\"", Info->Name);
    550             DtFatal (ASL_MSG_COMPILER_INTERNAL, NULL, AslGbl_MsgBuffer);
    551             return (0);
    552         }
    553         break;
    554 
    555     case ACPI_DMT_GAS:
    556 
    557         ByteLength = sizeof (ACPI_GENERIC_ADDRESS);
    558         break;
    559 
    560     case ACPI_DMT_HESTNTFY:
    561 
    562         ByteLength = sizeof (ACPI_HEST_NOTIFY);
    563         break;
    564 
    565     case ACPI_DMT_IORTMEM:
    566 
    567         ByteLength = sizeof (ACPI_IORT_MEMORY_ACCESS);
    568         break;
    569 
    570     case ACPI_DMT_BUFFER:
    571     case ACPI_DMT_RAW_BUFFER:
    572     case ACPI_DMT_PMTT_VENDOR:
    573 
    574         Value = DtGetFieldValue (Field);
    575         if (Value)
    576         {
    577             ByteLength = DtGetBufferLength (Value);
    578         }
    579         else
    580         {   /* At this point, this is a fatal error */
    581 
    582             snprintf (AslGbl_MsgBuffer, sizeof(AslGbl_MsgBuffer), "Expected \"%s\"", Info->Name);
    583             DtFatal (ASL_MSG_COMPILER_INTERNAL, NULL, AslGbl_MsgBuffer);
    584             return (0);
    585         }
    586         break;
    587 
    588     case ACPI_DMT_BUF10:
    589 
    590         ByteLength = 10;
    591         break;
    592 
    593     case ACPI_DMT_BUF12:
    594 
    595         ByteLength = 12;
    596         break;
    597 
    598     case ACPI_DMT_BUF16:
    599     case ACPI_DMT_UUID:
    600 
    601         ByteLength = 16;
    602         break;
    603 
    604     case ACPI_DMT_BUF128:
    605 
    606         ByteLength = 128;
    607         break;
    608 
    609     case ACPI_DMT_UNICODE:
    610 
    611         Value = DtGetFieldValue (Field);
    612 
    613         /* TBD: error if Value is NULL? (as below?) */
    614 
    615         ByteLength = (strlen (Value) + 1) * sizeof(UINT16);
    616         break;
    617 
    618     default:
    619 
    620         DtFatal (ASL_MSG_COMPILER_INTERNAL, Field, "Invalid table opcode");
    621         return (0);
    622     }
    623 
    624     return (ByteLength);
    625 }
    626 
    627 
    628 /******************************************************************************
    629  *
    630  * FUNCTION:    DtSum
    631  *
    632  * PARAMETERS:  DT_WALK_CALLBACK:
    633  *              Subtable            - Subtable
    634  *              Context             - Unused
    635  *              ReturnValue         - Store the checksum of subtable
    636  *
    637  * RETURN:      Status
    638  *
    639  * DESCRIPTION: Get the checksum of subtable
    640  *
    641  *****************************************************************************/
    642 
    643 static void
    644 DtSum (
    645     DT_SUBTABLE             *Subtable,
    646     void                    *Context,
    647     void                    *ReturnValue)
    648 {
    649     UINT8                   Checksum;
    650     UINT8                   *Sum = ReturnValue;
    651 
    652 
    653     Checksum = AcpiTbChecksum (Subtable->Buffer, Subtable->Length);
    654     *Sum = (UINT8) (*Sum + Checksum);
    655 }
    656 
    657 
    658 /******************************************************************************
    659  *
    660  * FUNCTION:    DtSetTableChecksum
    661  *
    662  * PARAMETERS:  ChecksumPointer     - Where to return the checksum
    663  *
    664  * RETURN:      None
    665  *
    666  * DESCRIPTION: Set checksum of the whole data table into the checksum field
    667  *
    668  *****************************************************************************/
    669 
    670 void
    671 DtSetTableChecksum (
    672     UINT8                   *ChecksumPointer)
    673 {
    674     UINT8                   Checksum = 0;
    675     UINT8                   OldSum;
    676 
    677 
    678     DtWalkTableTree (AslGbl_RootTable, DtSum, NULL, &Checksum);
    679 
    680     OldSum = *ChecksumPointer;
    681     Checksum = (UINT8) (Checksum - OldSum);
    682 
    683     /* Compute the final checksum */
    684 
    685     Checksum = (UINT8) (0 - Checksum);
    686     *ChecksumPointer = Checksum;
    687 }
    688 
    689 
    690 /******************************************************************************
    691  *
    692  * FUNCTION:    DtSetTableLength
    693  *
    694  * PARAMETERS:  None
    695  *
    696  * RETURN:      None
    697  *
    698  * DESCRIPTION: Walk the subtables and set all the length fields
    699  *
    700  *****************************************************************************/
    701 
    702 void
    703 DtSetTableLength (
    704     void)
    705 {
    706     DT_SUBTABLE             *ParentTable;
    707     DT_SUBTABLE             *ChildTable;
    708 
    709 
    710     ParentTable = AslGbl_RootTable;
    711     ChildTable = NULL;
    712 
    713     if (!ParentTable)
    714     {
    715         return;
    716     }
    717 
    718     DtSetSubtableLength (ParentTable);
    719 
    720     while (1)
    721     {
    722         ChildTable = DtGetNextSubtable (ParentTable, ChildTable);
    723         if (ChildTable)
    724         {
    725             if (ChildTable->LengthField)
    726             {
    727                 DtSetSubtableLength (ChildTable);
    728             }
    729 
    730             if (ChildTable->Child)
    731             {
    732                 ParentTable = ChildTable;
    733                 ChildTable = NULL;
    734             }
    735             else
    736             {
    737                 ParentTable->TotalLength += ChildTable->TotalLength;
    738                 if (ParentTable->LengthField)
    739                 {
    740                     DtSetSubtableLength (ParentTable);
    741                 }
    742             }
    743         }
    744         else
    745         {
    746             ChildTable = ParentTable;
    747 
    748             if (ChildTable == AslGbl_RootTable)
    749             {
    750                 break;
    751             }
    752 
    753             ParentTable = DtGetParentSubtable (ParentTable);
    754 
    755             ParentTable->TotalLength += ChildTable->TotalLength;
    756             if (ParentTable->LengthField)
    757             {
    758                 DtSetSubtableLength (ParentTable);
    759             }
    760         }
    761     }
    762 }
    763 
    764 
    765 /******************************************************************************
    766  *
    767  * FUNCTION:    DtWalkTableTree
    768  *
    769  * PARAMETERS:  StartTable          - Subtable in the tree where walking begins
    770  *              UserFunction        - Called during the walk
    771  *              Context             - Passed to user function
    772  *              ReturnValue         - The return value of UserFunction
    773  *
    774  * RETURN:      None
    775  *
    776  * DESCRIPTION: Performs a depth-first walk of the subtable tree
    777  *
    778  *****************************************************************************/
    779 
    780 void
    781 DtWalkTableTree (
    782     DT_SUBTABLE             *StartTable,
    783     DT_WALK_CALLBACK        UserFunction,
    784     void                    *Context,
    785     void                    *ReturnValue)
    786 {
    787     DT_SUBTABLE             *ParentTable;
    788     DT_SUBTABLE             *ChildTable;
    789 
    790 
    791     ParentTable = StartTable;
    792     ChildTable = NULL;
    793 
    794     if (!ParentTable)
    795     {
    796         return;
    797     }
    798 
    799     UserFunction (ParentTable, Context, ReturnValue);
    800 
    801     while (1)
    802     {
    803         ChildTable = DtGetNextSubtable (ParentTable, ChildTable);
    804         if (ChildTable)
    805         {
    806             UserFunction (ChildTable, Context, ReturnValue);
    807 
    808             if (ChildTable->Child)
    809             {
    810                 ParentTable = ChildTable;
    811                 ChildTable = NULL;
    812             }
    813         }
    814         else
    815         {
    816             ChildTable = ParentTable;
    817             if (ChildTable == AslGbl_RootTable)
    818             {
    819                 break;
    820             }
    821 
    822             ParentTable = DtGetParentSubtable (ParentTable);
    823 
    824             if (ChildTable->Peer == StartTable)
    825             {
    826                 break;
    827             }
    828         }
    829     }
    830 }
    831