dtutils.c revision 1.1.1.25 1 /******************************************************************************
2 *
3 * Module Name: dtutils.c - Utility routines for the data table compiler
4 *
5 *****************************************************************************/
6
7 /*
8 * Copyright (C) 2000 - 2023, 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_FLAGS8_2:
307 case ACPI_DMT_FLAGS4:
308 case ACPI_DMT_FLAGS4_0:
309 case ACPI_DMT_FLAGS4_4:
310 case ACPI_DMT_FLAGS4_8:
311 case ACPI_DMT_FLAGS4_12:
312 case ACPI_DMT_FLAGS16_16:
313
314 Type = DT_FIELD_TYPE_FLAG;
315 break;
316
317 case ACPI_DMT_NAME4:
318 case ACPI_DMT_SIG:
319 case ACPI_DMT_NAME6:
320 case ACPI_DMT_NAME8:
321 case ACPI_DMT_STRING:
322 case ACPI_DMT_IVRS_UNTERMINATED_STRING:
323
324 Type = DT_FIELD_TYPE_STRING;
325 break;
326
327 case ACPI_DMT_BUFFER:
328 case ACPI_DMT_RAW_BUFFER:
329 case ACPI_DMT_BUF7:
330 case ACPI_DMT_BUF10:
331 case ACPI_DMT_BUF12:
332 case ACPI_DMT_BUF16:
333 case ACPI_DMT_BUF18:
334 case ACPI_DMT_BUF32:
335 case ACPI_DMT_BUF112:
336 case ACPI_DMT_BUF128:
337 case ACPI_DMT_PCI_PATH:
338 case ACPI_DMT_PMTT_VENDOR:
339
340 Type = DT_FIELD_TYPE_BUFFER;
341 break;
342
343 case ACPI_DMT_GAS:
344 case ACPI_DMT_HESTNTFY:
345 case ACPI_DMT_IORTMEM:
346
347 Type = DT_FIELD_TYPE_INLINE_SUBTABLE;
348 break;
349
350 case ACPI_DMT_UNICODE:
351 case ACPI_DMT_WPBT_UNICODE:
352
353 Type = DT_FIELD_TYPE_UNICODE;
354 break;
355
356 case ACPI_DMT_UUID:
357
358 Type = DT_FIELD_TYPE_UUID;
359 break;
360
361 case ACPI_DMT_DEVICE_PATH:
362
363 Type = DT_FIELD_TYPE_DEVICE_PATH;
364 break;
365
366 case ACPI_DMT_LABEL:
367
368 Type = DT_FIELD_TYPE_LABEL;
369 break;
370
371 default:
372
373 Type = DT_FIELD_TYPE_INTEGER;
374 break;
375 }
376
377 return (Type);
378 }
379
380
381 /******************************************************************************
382 *
383 * FUNCTION: DtGetBufferLength
384 *
385 * PARAMETERS: Buffer - List of integers,
386 * for example "10 3A 4F 2E"
387 *
388 * RETURN: Count of integer
389 *
390 * DESCRIPTION: Get length of bytes needed to store the integers
391 *
392 *****************************************************************************/
393
394 UINT32
395 DtGetBufferLength (
396 char *Buffer)
397 {
398 UINT32 ByteLength = 0;
399
400
401 while (*Buffer)
402 {
403 if (*Buffer == ' ')
404 {
405 ByteLength++;
406
407 while (*Buffer == ' ')
408 {
409 Buffer++;
410 }
411 }
412
413 Buffer++;
414 }
415
416 return (++ByteLength);
417 }
418
419
420 /******************************************************************************
421 *
422 * FUNCTION: DtGetFieldLength
423 *
424 * PARAMETERS: Field - Current field
425 * Info - Data table info
426 *
427 * RETURN: Field length
428 *
429 * DESCRIPTION: Get length of bytes needed to compile the field
430 *
431 * Note: This function must remain in sync with AcpiDmDumpTable.
432 *
433 *****************************************************************************/
434
435 UINT32
436 DtGetFieldLength (
437 DT_FIELD *Field,
438 ACPI_DMTABLE_INFO *Info)
439 {
440 UINT32 ByteLength = 0;
441 char *Value;
442
443
444 /* Length is based upon the opcode for this field in the info table */
445
446 switch (Info->Opcode)
447 {
448 case ACPI_DMT_FLAG0:
449 case ACPI_DMT_FLAG1:
450 case ACPI_DMT_FLAG2:
451 case ACPI_DMT_FLAG3:
452 case ACPI_DMT_FLAG4:
453 case ACPI_DMT_FLAG5:
454 case ACPI_DMT_FLAG6:
455 case ACPI_DMT_FLAG7:
456 case ACPI_DMT_FLAGS0:
457 case ACPI_DMT_FLAGS1:
458 case ACPI_DMT_FLAGS2:
459 case ACPI_DMT_FLAGS8_2:
460 case ACPI_DMT_FLAGS4:
461 case ACPI_DMT_FLAGS4_0:
462 case ACPI_DMT_FLAGS4_4:
463 case ACPI_DMT_FLAGS4_8:
464 case ACPI_DMT_FLAGS4_12:
465 case ACPI_DMT_FLAGS16_16:
466 case ACPI_DMT_LABEL:
467 case ACPI_DMT_EXTRA_TEXT:
468
469 ByteLength = 0;
470 break;
471
472 case ACPI_DMT_UINT8:
473 case ACPI_DMT_CHKSUM:
474 case ACPI_DMT_SPACEID:
475 case ACPI_DMT_ACCWIDTH:
476 case ACPI_DMT_CEDT:
477 case ACPI_DMT_IVRS:
478 case ACPI_DMT_IVRS_DE:
479 case ACPI_DMT_GTDT:
480 case ACPI_DMT_MADT:
481 case ACPI_DMT_MPAM_LOCATOR:
482 case ACPI_DMT_PCCT:
483 case ACPI_DMT_PMTT:
484 case ACPI_DMT_PPTT:
485 case ACPI_DMT_RGRT:
486 case ACPI_DMT_SDEV:
487 case ACPI_DMT_SRAT:
488 case ACPI_DMT_AEST:
489 case ACPI_DMT_AEST_RES:
490 case ACPI_DMT_AEST_XFACE:
491 case ACPI_DMT_AEST_XRUPT:
492 case ACPI_DMT_ASF:
493 case ACPI_DMT_CDAT:
494 case ACPI_DMT_HESTNTYP:
495 case ACPI_DMT_FADTPM:
496 case ACPI_DMT_EINJACT:
497 case ACPI_DMT_EINJINST:
498 case ACPI_DMT_ERSTACT:
499 case ACPI_DMT_ERSTINST:
500 case ACPI_DMT_DMAR_SCOPE:
501 case ACPI_DMT_VIOT:
502
503 ByteLength = 1;
504 break;
505
506 case ACPI_DMT_ASPT:
507 case ACPI_DMT_UINT16:
508 case ACPI_DMT_DMAR:
509 case ACPI_DMT_HEST:
510 case ACPI_DMT_HMAT:
511 case ACPI_DMT_NFIT:
512 case ACPI_DMT_PCI_PATH:
513 case ACPI_DMT_PHAT:
514
515 ByteLength = 2;
516 break;
517
518 case ACPI_DMT_UINT24:
519
520 ByteLength = 3;
521 break;
522
523 case ACPI_DMT_UINT32:
524 case ACPI_DMT_AEST_CACHE:
525 case ACPI_DMT_AEST_GIC:
526 case ACPI_DMT_NAME4:
527 case ACPI_DMT_SIG:
528 case ACPI_DMT_LPIT:
529 case ACPI_DMT_TPM2:
530
531 ByteLength = 4;
532 break;
533
534 case ACPI_DMT_UINT40:
535
536 ByteLength = 5;
537 break;
538
539 case ACPI_DMT_UINT48:
540 case ACPI_DMT_NAME6:
541
542 ByteLength = 6;
543 break;
544
545 case ACPI_DMT_UINT56:
546 case ACPI_DMT_BUF7:
547
548 ByteLength = 7;
549 break;
550
551 case ACPI_DMT_UINT64:
552 case ACPI_DMT_NAME8:
553
554 ByteLength = 8;
555 break;
556
557 case ACPI_DMT_STRING:
558
559 Value = DtGetFieldValue (Field);
560 if (Value)
561 {
562 ByteLength = strlen (Value) + 1;
563 }
564 else
565 { /* At this point, this is a fatal error */
566
567 sprintf (AslGbl_MsgBuffer, "Expected \"%s\"", Info->Name);
568 DtFatal (ASL_MSG_COMPILER_INTERNAL, NULL, AslGbl_MsgBuffer);
569 return (0);
570 }
571 break;
572
573 case ACPI_DMT_IVRS_UNTERMINATED_STRING:
574
575 Value = DtGetFieldValue (Field);
576 if (Value)
577 {
578 ByteLength = strlen (Value);
579 }
580 else
581 { /* At this point, this is a fatal error */
582
583 sprintf (AslGbl_MsgBuffer, "Expected \"%s\"", Info->Name);
584 DtFatal (ASL_MSG_COMPILER_INTERNAL, NULL, AslGbl_MsgBuffer);
585 return (0);
586 }
587 break;
588
589 case ACPI_DMT_GAS:
590
591 ByteLength = sizeof (ACPI_GENERIC_ADDRESS);
592 break;
593
594 case ACPI_DMT_HESTNTFY:
595
596 ByteLength = sizeof (ACPI_HEST_NOTIFY);
597 break;
598
599 case ACPI_DMT_IORTMEM:
600
601 ByteLength = sizeof (ACPI_IORT_MEMORY_ACCESS);
602 break;
603
604 case ACPI_DMT_BUFFER:
605 case ACPI_DMT_RAW_BUFFER:
606 case ACPI_DMT_PMTT_VENDOR:
607
608 Value = DtGetFieldValue (Field);
609 if (Value)
610 {
611 ByteLength = DtGetBufferLength (Value);
612 }
613 else
614 { /* At this point, this is a fatal error */
615
616 sprintf (AslGbl_MsgBuffer, "Expected \"%s\"", Info->Name);
617 DtFatal (ASL_MSG_COMPILER_INTERNAL, NULL, AslGbl_MsgBuffer);
618 return (0);
619 }
620 break;
621
622 case ACPI_DMT_BUF10:
623
624 ByteLength = 10;
625 break;
626
627 case ACPI_DMT_BUF12:
628
629 ByteLength = 12;
630 break;
631
632 case ACPI_DMT_BUF16:
633 case ACPI_DMT_UUID:
634
635 ByteLength = 16;
636 break;
637
638 case ACPI_DMT_BUF18:
639
640 ByteLength = 18;
641 break;
642
643 case ACPI_DMT_BUF32:
644
645 ByteLength = 32;
646 break;
647
648 case ACPI_DMT_BUF112:
649
650 ByteLength = 112;
651 break;
652
653 case ACPI_DMT_BUF128:
654
655 ByteLength = 128;
656 break;
657
658 case ACPI_DMT_UNICODE:
659 case ACPI_DMT_WPBT_UNICODE:
660
661 Value = DtGetFieldValue (Field);
662
663 /* TBD: error if Value is NULL? (as below?) */
664
665 ByteLength = (strlen (Value) + 1) * sizeof (UINT16);
666 break;
667
668 default:
669
670 DtFatal (ASL_MSG_COMPILER_INTERNAL, Field, "Invalid table opcode");
671 return (0);
672 }
673
674 return (ByteLength);
675 }
676
677
678 /******************************************************************************
679 *
680 * FUNCTION: DtSum
681 *
682 * PARAMETERS: DT_WALK_CALLBACK:
683 * Subtable - Subtable
684 * Context - Unused
685 * ReturnValue - Store the checksum of subtable
686 *
687 * RETURN: Status
688 *
689 * DESCRIPTION: Get the checksum of subtable
690 *
691 *****************************************************************************/
692
693 static void
694 DtSum (
695 DT_SUBTABLE *Subtable,
696 void *Context,
697 void *ReturnValue)
698 {
699 UINT8 Checksum;
700 UINT8 *Sum = ReturnValue;
701
702
703 Checksum = AcpiUtChecksum (Subtable->Buffer, Subtable->Length);
704 *Sum = (UINT8) (*Sum + Checksum);
705 }
706
707
708 /******************************************************************************
709 *
710 * FUNCTION: DtSetTableChecksum
711 *
712 * PARAMETERS: ChecksumPointer - Where to return the checksum
713 *
714 * RETURN: None
715 *
716 * DESCRIPTION: Set checksum of the whole data table into the checksum field
717 *
718 *****************************************************************************/
719
720 void
721 DtSetTableChecksum (
722 UINT8 *ChecksumPointer)
723 {
724 UINT8 Checksum = 0;
725 UINT8 OldSum;
726
727
728 DtWalkTableTree (AslGbl_RootTable, DtSum, NULL, &Checksum);
729
730 OldSum = *ChecksumPointer;
731 Checksum = (UINT8) (Checksum - OldSum);
732
733 /* Compute the final checksum */
734
735 Checksum = (UINT8) (0 - Checksum);
736 *ChecksumPointer = Checksum;
737 }
738
739
740 /******************************************************************************
741 *
742 * FUNCTION: DtSetTableLength
743 *
744 * PARAMETERS: None
745 *
746 * RETURN: None
747 *
748 * DESCRIPTION: Walk the subtables and set all the length fields
749 *
750 *****************************************************************************/
751
752 void
753 DtSetTableLength (
754 void)
755 {
756 DT_SUBTABLE *ParentTable;
757 DT_SUBTABLE *ChildTable;
758
759
760 ParentTable = AslGbl_RootTable;
761 ChildTable = NULL;
762
763 if (!ParentTable)
764 {
765 return;
766 }
767
768 DtSetSubtableLength (ParentTable);
769
770 while (1)
771 {
772 ChildTable = DtGetNextSubtable (ParentTable, ChildTable);
773 if (ChildTable)
774 {
775 if (ChildTable->LengthField)
776 {
777 DtSetSubtableLength (ChildTable);
778 }
779
780 if (ChildTable->Child)
781 {
782 ParentTable = ChildTable;
783 ChildTable = NULL;
784 }
785 else
786 {
787 ParentTable->TotalLength += ChildTable->TotalLength;
788 if (ParentTable->LengthField)
789 {
790 DtSetSubtableLength (ParentTable);
791 }
792 }
793 }
794 else
795 {
796 ChildTable = ParentTable;
797
798 if (ChildTable == AslGbl_RootTable)
799 {
800 break;
801 }
802
803 ParentTable = DtGetParentSubtable (ParentTable);
804
805 ParentTable->TotalLength += ChildTable->TotalLength;
806 if (ParentTable->LengthField)
807 {
808 DtSetSubtableLength (ParentTable);
809 }
810 }
811 }
812 }
813
814
815 /******************************************************************************
816 *
817 * FUNCTION: DtWalkTableTree
818 *
819 * PARAMETERS: StartTable - Subtable in the tree where walking begins
820 * UserFunction - Called during the walk
821 * Context - Passed to user function
822 * ReturnValue - The return value of UserFunction
823 *
824 * RETURN: None
825 *
826 * DESCRIPTION: Performs a depth-first walk of the subtable tree
827 *
828 *****************************************************************************/
829
830 void
831 DtWalkTableTree (
832 DT_SUBTABLE *StartTable,
833 DT_WALK_CALLBACK UserFunction,
834 void *Context,
835 void *ReturnValue)
836 {
837 DT_SUBTABLE *ParentTable;
838 DT_SUBTABLE *ChildTable;
839
840
841 ParentTable = StartTable;
842 ChildTable = NULL;
843
844 if (!ParentTable)
845 {
846 return;
847 }
848
849 UserFunction (ParentTable, Context, ReturnValue);
850
851 while (1)
852 {
853 ChildTable = DtGetNextSubtable (ParentTable, ChildTable);
854 if (ChildTable)
855 {
856 UserFunction (ChildTable, Context, ReturnValue);
857
858 if (ChildTable->Child)
859 {
860 ParentTable = ChildTable;
861 ChildTable = NULL;
862 }
863 }
864 else
865 {
866 ChildTable = ParentTable;
867 if (ChildTable == AslGbl_RootTable)
868 {
869 break;
870 }
871
872 ParentTable = DtGetParentSubtable (ParentTable);
873
874 if (ChildTable->Peer == StartTable)
875 {
876 break;
877 }
878 }
879 }
880 }
881