xref: /freebsd/sys/contrib/dev/acpica/components/dispatcher/dswstate.c (revision 0677dfd1c4dadb62482e2c72fa4c6720902128a4)
1 /******************************************************************************
2  *
3  * Module Name: dswstate - Dispatcher parse tree walk management routines
4  *
5  *****************************************************************************/
6 
7 /*
8  * Copyright (C) 2000 - 2014, 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 MERCHANTIBILITY 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 __DSWSTATE_C__
45 
46 #include <contrib/dev/acpica/include/acpi.h>
47 #include <contrib/dev/acpica/include/accommon.h>
48 #include <contrib/dev/acpica/include/acparser.h>
49 #include <contrib/dev/acpica/include/acdispat.h>
50 #include <contrib/dev/acpica/include/acnamesp.h>
51 
52 #define _COMPONENT          ACPI_DISPATCHER
53         ACPI_MODULE_NAME    ("dswstate")
54 
55 /* Local prototypes */
56 
57 static ACPI_STATUS
58 AcpiDsResultStackPush (
59     ACPI_WALK_STATE         *WalkState);
60 
61 static ACPI_STATUS
62 AcpiDsResultStackPop (
63     ACPI_WALK_STATE         *WalkState);
64 
65 
66 /*******************************************************************************
67  *
68  * FUNCTION:    AcpiDsResultPop
69  *
70  * PARAMETERS:  Object              - Where to return the popped object
71  *              WalkState           - Current Walk state
72  *
73  * RETURN:      Status
74  *
75  * DESCRIPTION: Pop an object off the top of this walk's result stack
76  *
77  ******************************************************************************/
78 
79 ACPI_STATUS
80 AcpiDsResultPop (
81     ACPI_OPERAND_OBJECT     **Object,
82     ACPI_WALK_STATE         *WalkState)
83 {
84     UINT32                  Index;
85     ACPI_GENERIC_STATE      *State;
86     ACPI_STATUS             Status;
87 
88 
89     ACPI_FUNCTION_NAME (DsResultPop);
90 
91 
92     State = WalkState->Results;
93 
94     /* Incorrect state of result stack */
95 
96     if (State && !WalkState->ResultCount)
97     {
98         ACPI_ERROR ((AE_INFO, "No results on result stack"));
99         return (AE_AML_INTERNAL);
100     }
101 
102     if (!State && WalkState->ResultCount)
103     {
104         ACPI_ERROR ((AE_INFO, "No result state for result stack"));
105         return (AE_AML_INTERNAL);
106     }
107 
108     /* Empty result stack */
109 
110     if (!State)
111     {
112         ACPI_ERROR ((AE_INFO, "Result stack is empty! State=%p", WalkState));
113         return (AE_AML_NO_RETURN_VALUE);
114     }
115 
116     /* Return object of the top element and clean that top element result stack */
117 
118     WalkState->ResultCount--;
119     Index = (UINT32) WalkState->ResultCount % ACPI_RESULTS_FRAME_OBJ_NUM;
120 
121     *Object = State->Results.ObjDesc [Index];
122     if (!*Object)
123     {
124         ACPI_ERROR ((AE_INFO, "No result objects on result stack, State=%p",
125             WalkState));
126         return (AE_AML_NO_RETURN_VALUE);
127     }
128 
129     State->Results.ObjDesc [Index] = NULL;
130     if (Index == 0)
131     {
132         Status = AcpiDsResultStackPop (WalkState);
133         if (ACPI_FAILURE (Status))
134         {
135             return (Status);
136         }
137     }
138 
139     ACPI_DEBUG_PRINT ((ACPI_DB_EXEC,
140         "Obj=%p [%s] Index=%X State=%p Num=%X\n", *Object,
141         AcpiUtGetObjectTypeName (*Object),
142         Index, WalkState, WalkState->ResultCount));
143 
144     return (AE_OK);
145 }
146 
147 
148 /*******************************************************************************
149  *
150  * FUNCTION:    AcpiDsResultPush
151  *
152  * PARAMETERS:  Object              - Where to return the popped object
153  *              WalkState           - Current Walk state
154  *
155  * RETURN:      Status
156  *
157  * DESCRIPTION: Push an object onto the current result stack
158  *
159  ******************************************************************************/
160 
161 ACPI_STATUS
162 AcpiDsResultPush (
163     ACPI_OPERAND_OBJECT     *Object,
164     ACPI_WALK_STATE         *WalkState)
165 {
166     ACPI_GENERIC_STATE      *State;
167     ACPI_STATUS             Status;
168     UINT32                  Index;
169 
170 
171     ACPI_FUNCTION_NAME (DsResultPush);
172 
173 
174     if (WalkState->ResultCount > WalkState->ResultSize)
175     {
176         ACPI_ERROR ((AE_INFO, "Result stack is full"));
177         return (AE_AML_INTERNAL);
178     }
179     else if (WalkState->ResultCount == WalkState->ResultSize)
180     {
181         /* Extend the result stack */
182 
183         Status = AcpiDsResultStackPush (WalkState);
184         if (ACPI_FAILURE (Status))
185         {
186             ACPI_ERROR ((AE_INFO, "Failed to extend the result stack"));
187             return (Status);
188         }
189     }
190 
191     if (!(WalkState->ResultCount < WalkState->ResultSize))
192     {
193         ACPI_ERROR ((AE_INFO, "No free elements in result stack"));
194         return (AE_AML_INTERNAL);
195     }
196 
197     State = WalkState->Results;
198     if (!State)
199     {
200         ACPI_ERROR ((AE_INFO, "No result stack frame during push"));
201         return (AE_AML_INTERNAL);
202     }
203 
204     if (!Object)
205     {
206         ACPI_ERROR ((AE_INFO,
207             "Null Object! Obj=%p State=%p Num=%u",
208             Object, WalkState, WalkState->ResultCount));
209         return (AE_BAD_PARAMETER);
210     }
211 
212     /* Assign the address of object to the top free element of result stack */
213 
214     Index = (UINT32) WalkState->ResultCount % ACPI_RESULTS_FRAME_OBJ_NUM;
215     State->Results.ObjDesc [Index] = Object;
216     WalkState->ResultCount++;
217 
218     ACPI_DEBUG_PRINT ((ACPI_DB_EXEC, "Obj=%p [%s] State=%p Num=%X Cur=%X\n",
219         Object, AcpiUtGetObjectTypeName ((ACPI_OPERAND_OBJECT *) Object),
220         WalkState, WalkState->ResultCount, WalkState->CurrentResult));
221 
222     return (AE_OK);
223 }
224 
225 
226 /*******************************************************************************
227  *
228  * FUNCTION:    AcpiDsResultStackPush
229  *
230  * PARAMETERS:  WalkState           - Current Walk state
231  *
232  * RETURN:      Status
233  *
234  * DESCRIPTION: Push an object onto the WalkState result stack
235  *
236  ******************************************************************************/
237 
238 static ACPI_STATUS
239 AcpiDsResultStackPush (
240     ACPI_WALK_STATE         *WalkState)
241 {
242     ACPI_GENERIC_STATE      *State;
243 
244 
245     ACPI_FUNCTION_NAME (DsResultStackPush);
246 
247 
248     /* Check for stack overflow */
249 
250     if (((UINT32) WalkState->ResultSize + ACPI_RESULTS_FRAME_OBJ_NUM) >
251         ACPI_RESULTS_OBJ_NUM_MAX)
252     {
253         ACPI_ERROR ((AE_INFO, "Result stack overflow: State=%p Num=%u",
254             WalkState, WalkState->ResultSize));
255         return (AE_STACK_OVERFLOW);
256     }
257 
258     State = AcpiUtCreateGenericState ();
259     if (!State)
260     {
261         return (AE_NO_MEMORY);
262     }
263 
264     State->Common.DescriptorType = ACPI_DESC_TYPE_STATE_RESULT;
265     AcpiUtPushGenericState (&WalkState->Results, State);
266 
267     /* Increase the length of the result stack by the length of frame */
268 
269     WalkState->ResultSize += ACPI_RESULTS_FRAME_OBJ_NUM;
270 
271     ACPI_DEBUG_PRINT ((ACPI_DB_EXEC, "Results=%p State=%p\n",
272         State, WalkState));
273 
274     return (AE_OK);
275 }
276 
277 
278 /*******************************************************************************
279  *
280  * FUNCTION:    AcpiDsResultStackPop
281  *
282  * PARAMETERS:  WalkState           - Current Walk state
283  *
284  * RETURN:      Status
285  *
286  * DESCRIPTION: Pop an object off of the WalkState result stack
287  *
288  ******************************************************************************/
289 
290 static ACPI_STATUS
291 AcpiDsResultStackPop (
292     ACPI_WALK_STATE         *WalkState)
293 {
294     ACPI_GENERIC_STATE      *State;
295 
296 
297     ACPI_FUNCTION_NAME (DsResultStackPop);
298 
299 
300     /* Check for stack underflow */
301 
302     if (WalkState->Results == NULL)
303     {
304         ACPI_DEBUG_PRINT ((ACPI_DB_EXEC, "Result stack underflow - State=%p\n",
305             WalkState));
306         return (AE_AML_NO_OPERAND);
307     }
308 
309     if (WalkState->ResultSize < ACPI_RESULTS_FRAME_OBJ_NUM)
310     {
311         ACPI_ERROR ((AE_INFO, "Insufficient result stack size"));
312         return (AE_AML_INTERNAL);
313     }
314 
315     State = AcpiUtPopGenericState (&WalkState->Results);
316     AcpiUtDeleteGenericState (State);
317 
318     /* Decrease the length of result stack by the length of frame */
319 
320     WalkState->ResultSize -= ACPI_RESULTS_FRAME_OBJ_NUM;
321 
322     ACPI_DEBUG_PRINT ((ACPI_DB_EXEC,
323         "Result=%p RemainingResults=%X State=%p\n",
324         State, WalkState->ResultCount, WalkState));
325 
326     return (AE_OK);
327 }
328 
329 
330 /*******************************************************************************
331  *
332  * FUNCTION:    AcpiDsObjStackPush
333  *
334  * PARAMETERS:  Object              - Object to push
335  *              WalkState           - Current Walk state
336  *
337  * RETURN:      Status
338  *
339  * DESCRIPTION: Push an object onto this walk's object/operand stack
340  *
341  ******************************************************************************/
342 
343 ACPI_STATUS
344 AcpiDsObjStackPush (
345     void                    *Object,
346     ACPI_WALK_STATE         *WalkState)
347 {
348     ACPI_FUNCTION_NAME (DsObjStackPush);
349 
350 
351     /* Check for stack overflow */
352 
353     if (WalkState->NumOperands >= ACPI_OBJ_NUM_OPERANDS)
354     {
355         ACPI_ERROR ((AE_INFO,
356             "Object stack overflow! Obj=%p State=%p #Ops=%u",
357             Object, WalkState, WalkState->NumOperands));
358         return (AE_STACK_OVERFLOW);
359     }
360 
361     /* Put the object onto the stack */
362 
363     WalkState->Operands [WalkState->OperandIndex] = Object;
364     WalkState->NumOperands++;
365 
366     /* For the usual order of filling the operand stack */
367 
368     WalkState->OperandIndex++;
369 
370     ACPI_DEBUG_PRINT ((ACPI_DB_EXEC, "Obj=%p [%s] State=%p #Ops=%X\n",
371         Object, AcpiUtGetObjectTypeName ((ACPI_OPERAND_OBJECT *) Object),
372         WalkState, WalkState->NumOperands));
373 
374     return (AE_OK);
375 }
376 
377 
378 /*******************************************************************************
379  *
380  * FUNCTION:    AcpiDsObjStackPop
381  *
382  * PARAMETERS:  PopCount            - Number of objects/entries to pop
383  *              WalkState           - Current Walk state
384  *
385  * RETURN:      Status
386  *
387  * DESCRIPTION: Pop this walk's object stack. Objects on the stack are NOT
388  *              deleted by this routine.
389  *
390  ******************************************************************************/
391 
392 ACPI_STATUS
393 AcpiDsObjStackPop (
394     UINT32                  PopCount,
395     ACPI_WALK_STATE         *WalkState)
396 {
397     UINT32                  i;
398 
399 
400     ACPI_FUNCTION_NAME (DsObjStackPop);
401 
402 
403     for (i = 0; i < PopCount; i++)
404     {
405         /* Check for stack underflow */
406 
407         if (WalkState->NumOperands == 0)
408         {
409             ACPI_ERROR ((AE_INFO,
410                 "Object stack underflow! Count=%X State=%p #Ops=%u",
411                 PopCount, WalkState, WalkState->NumOperands));
412             return (AE_STACK_UNDERFLOW);
413         }
414 
415         /* Just set the stack entry to null */
416 
417         WalkState->NumOperands--;
418         WalkState->Operands [WalkState->NumOperands] = NULL;
419     }
420 
421     ACPI_DEBUG_PRINT ((ACPI_DB_EXEC, "Count=%X State=%p #Ops=%u\n",
422         PopCount, WalkState, WalkState->NumOperands));
423 
424     return (AE_OK);
425 }
426 
427 
428 /*******************************************************************************
429  *
430  * FUNCTION:    AcpiDsObjStackPopAndDelete
431  *
432  * PARAMETERS:  PopCount            - Number of objects/entries to pop
433  *              WalkState           - Current Walk state
434  *
435  * RETURN:      Status
436  *
437  * DESCRIPTION: Pop this walk's object stack and delete each object that is
438  *              popped off.
439  *
440  ******************************************************************************/
441 
442 void
443 AcpiDsObjStackPopAndDelete (
444     UINT32                  PopCount,
445     ACPI_WALK_STATE         *WalkState)
446 {
447     INT32                   i;
448     ACPI_OPERAND_OBJECT     *ObjDesc;
449 
450 
451     ACPI_FUNCTION_NAME (DsObjStackPopAndDelete);
452 
453 
454     if (PopCount == 0)
455     {
456         return;
457     }
458 
459     for (i = (INT32) PopCount - 1; i >= 0; i--)
460     {
461         if (WalkState->NumOperands == 0)
462         {
463             return;
464         }
465 
466         /* Pop the stack and delete an object if present in this stack entry */
467 
468         WalkState->NumOperands--;
469         ObjDesc = WalkState->Operands [i];
470         if (ObjDesc)
471         {
472             AcpiUtRemoveReference (WalkState->Operands [i]);
473             WalkState->Operands [i] = NULL;
474         }
475     }
476 
477     ACPI_DEBUG_PRINT ((ACPI_DB_EXEC, "Count=%X State=%p #Ops=%X\n",
478         PopCount, WalkState, WalkState->NumOperands));
479 }
480 
481 
482 /*******************************************************************************
483  *
484  * FUNCTION:    AcpiDsGetCurrentWalkState
485  *
486  * PARAMETERS:  Thread          - Get current active state for this Thread
487  *
488  * RETURN:      Pointer to the current walk state
489  *
490  * DESCRIPTION: Get the walk state that is at the head of the list (the "current"
491  *              walk state.)
492  *
493  ******************************************************************************/
494 
495 ACPI_WALK_STATE *
496 AcpiDsGetCurrentWalkState (
497     ACPI_THREAD_STATE       *Thread)
498 {
499     ACPI_FUNCTION_NAME (DsGetCurrentWalkState);
500 
501 
502     if (!Thread)
503     {
504         return (NULL);
505     }
506 
507     ACPI_DEBUG_PRINT ((ACPI_DB_PARSE, "Current WalkState %p\n",
508         Thread->WalkStateList));
509 
510     return (Thread->WalkStateList);
511 }
512 
513 
514 /*******************************************************************************
515  *
516  * FUNCTION:    AcpiDsPushWalkState
517  *
518  * PARAMETERS:  WalkState       - State to push
519  *              Thread          - Thread state object
520  *
521  * RETURN:      None
522  *
523  * DESCRIPTION: Place the Thread state at the head of the state list
524  *
525  ******************************************************************************/
526 
527 void
528 AcpiDsPushWalkState (
529     ACPI_WALK_STATE         *WalkState,
530     ACPI_THREAD_STATE       *Thread)
531 {
532     ACPI_FUNCTION_TRACE (DsPushWalkState);
533 
534 
535     WalkState->Next = Thread->WalkStateList;
536     Thread->WalkStateList = WalkState;
537 
538     return_VOID;
539 }
540 
541 
542 /*******************************************************************************
543  *
544  * FUNCTION:    AcpiDsPopWalkState
545  *
546  * PARAMETERS:  Thread      - Current thread state
547  *
548  * RETURN:      A WalkState object popped from the thread's stack
549  *
550  * DESCRIPTION: Remove and return the walkstate object that is at the head of
551  *              the walk stack for the given walk list. NULL indicates that
552  *              the list is empty.
553  *
554  ******************************************************************************/
555 
556 ACPI_WALK_STATE *
557 AcpiDsPopWalkState (
558     ACPI_THREAD_STATE       *Thread)
559 {
560     ACPI_WALK_STATE         *WalkState;
561 
562 
563     ACPI_FUNCTION_TRACE (DsPopWalkState);
564 
565 
566     WalkState = Thread->WalkStateList;
567 
568     if (WalkState)
569     {
570         /* Next walk state becomes the current walk state */
571 
572         Thread->WalkStateList = WalkState->Next;
573 
574         /*
575          * Don't clear the NEXT field, this serves as an indicator
576          * that there is a parent WALK STATE
577          * Do Not: WalkState->Next = NULL;
578          */
579     }
580 
581     return_PTR (WalkState);
582 }
583 
584 
585 /*******************************************************************************
586  *
587  * FUNCTION:    AcpiDsCreateWalkState
588  *
589  * PARAMETERS:  OwnerId         - ID for object creation
590  *              Origin          - Starting point for this walk
591  *              MethodDesc      - Method object
592  *              Thread          - Current thread state
593  *
594  * RETURN:      Pointer to the new walk state.
595  *
596  * DESCRIPTION: Allocate and initialize a new walk state. The current walk
597  *              state is set to this new state.
598  *
599  ******************************************************************************/
600 
601 ACPI_WALK_STATE *
602 AcpiDsCreateWalkState (
603     ACPI_OWNER_ID           OwnerId,
604     ACPI_PARSE_OBJECT       *Origin,
605     ACPI_OPERAND_OBJECT     *MethodDesc,
606     ACPI_THREAD_STATE       *Thread)
607 {
608     ACPI_WALK_STATE         *WalkState;
609 
610 
611     ACPI_FUNCTION_TRACE (DsCreateWalkState);
612 
613 
614     WalkState = ACPI_ALLOCATE_ZEROED (sizeof (ACPI_WALK_STATE));
615     if (!WalkState)
616     {
617         return_PTR (NULL);
618     }
619 
620     WalkState->DescriptorType = ACPI_DESC_TYPE_WALK;
621     WalkState->MethodDesc = MethodDesc;
622     WalkState->OwnerId = OwnerId;
623     WalkState->Origin = Origin;
624     WalkState->Thread = Thread;
625 
626     WalkState->ParserState.StartOp = Origin;
627 
628     /* Init the method args/local */
629 
630 #if (!defined (ACPI_NO_METHOD_EXECUTION) && !defined (ACPI_CONSTANT_EVAL_ONLY))
631     AcpiDsMethodDataInit (WalkState);
632 #endif
633 
634     /* Put the new state at the head of the walk list */
635 
636     if (Thread)
637     {
638         AcpiDsPushWalkState (WalkState, Thread);
639     }
640 
641     return_PTR (WalkState);
642 }
643 
644 
645 /*******************************************************************************
646  *
647  * FUNCTION:    AcpiDsInitAmlWalk
648  *
649  * PARAMETERS:  WalkState       - New state to be initialized
650  *              Op              - Current parse op
651  *              MethodNode      - Control method NS node, if any
652  *              AmlStart        - Start of AML
653  *              AmlLength       - Length of AML
654  *              Info            - Method info block (params, etc.)
655  *              PassNumber      - 1, 2, or 3
656  *
657  * RETURN:      Status
658  *
659  * DESCRIPTION: Initialize a walk state for a pass 1 or 2 parse tree walk
660  *
661  ******************************************************************************/
662 
663 ACPI_STATUS
664 AcpiDsInitAmlWalk (
665     ACPI_WALK_STATE         *WalkState,
666     ACPI_PARSE_OBJECT       *Op,
667     ACPI_NAMESPACE_NODE     *MethodNode,
668     UINT8                   *AmlStart,
669     UINT32                  AmlLength,
670     ACPI_EVALUATE_INFO      *Info,
671     UINT8                   PassNumber)
672 {
673     ACPI_STATUS             Status;
674     ACPI_PARSE_STATE        *ParserState = &WalkState->ParserState;
675     ACPI_PARSE_OBJECT       *ExtraOp;
676 
677 
678     ACPI_FUNCTION_TRACE (DsInitAmlWalk);
679 
680 
681     WalkState->ParserState.Aml =
682     WalkState->ParserState.AmlStart = AmlStart;
683     WalkState->ParserState.AmlEnd =
684     WalkState->ParserState.PkgEnd = AmlStart + AmlLength;
685 
686     /* The NextOp of the NextWalk will be the beginning of the method */
687 
688     WalkState->NextOp = NULL;
689     WalkState->PassNumber = PassNumber;
690 
691     if (Info)
692     {
693         WalkState->Params = Info->Parameters;
694         WalkState->CallerReturnDesc = &Info->ReturnObject;
695     }
696 
697     Status = AcpiPsInitScope (&WalkState->ParserState, Op);
698     if (ACPI_FAILURE (Status))
699     {
700         return_ACPI_STATUS (Status);
701     }
702 
703     if (MethodNode)
704     {
705         WalkState->ParserState.StartNode = MethodNode;
706         WalkState->WalkType = ACPI_WALK_METHOD;
707         WalkState->MethodNode = MethodNode;
708         WalkState->MethodDesc = AcpiNsGetAttachedObject (MethodNode);
709 
710         /* Push start scope on scope stack and make it current  */
711 
712         Status = AcpiDsScopeStackPush (MethodNode, ACPI_TYPE_METHOD, WalkState);
713         if (ACPI_FAILURE (Status))
714         {
715             return_ACPI_STATUS (Status);
716         }
717 
718         /* Init the method arguments */
719 
720         Status = AcpiDsMethodDataInitArgs (WalkState->Params,
721                     ACPI_METHOD_NUM_ARGS, WalkState);
722         if (ACPI_FAILURE (Status))
723         {
724             return_ACPI_STATUS (Status);
725         }
726     }
727     else
728     {
729         /*
730          * Setup the current scope.
731          * Find a Named Op that has a namespace node associated with it.
732          * search upwards from this Op. Current scope is the first
733          * Op with a namespace node.
734          */
735         ExtraOp = ParserState->StartOp;
736         while (ExtraOp && !ExtraOp->Common.Node)
737         {
738             ExtraOp = ExtraOp->Common.Parent;
739         }
740 
741         if (!ExtraOp)
742         {
743             ParserState->StartNode = NULL;
744         }
745         else
746         {
747             ParserState->StartNode = ExtraOp->Common.Node;
748         }
749 
750         if (ParserState->StartNode)
751         {
752             /* Push start scope on scope stack and make it current  */
753 
754             Status = AcpiDsScopeStackPush (ParserState->StartNode,
755                             ParserState->StartNode->Type, WalkState);
756             if (ACPI_FAILURE (Status))
757             {
758                 return_ACPI_STATUS (Status);
759             }
760         }
761     }
762 
763     Status = AcpiDsInitCallbacks (WalkState, PassNumber);
764     return_ACPI_STATUS (Status);
765 }
766 
767 
768 /*******************************************************************************
769  *
770  * FUNCTION:    AcpiDsDeleteWalkState
771  *
772  * PARAMETERS:  WalkState       - State to delete
773  *
774  * RETURN:      Status
775  *
776  * DESCRIPTION: Delete a walk state including all internal data structures
777  *
778  ******************************************************************************/
779 
780 void
781 AcpiDsDeleteWalkState (
782     ACPI_WALK_STATE         *WalkState)
783 {
784     ACPI_GENERIC_STATE      *State;
785 
786 
787     ACPI_FUNCTION_TRACE_PTR (DsDeleteWalkState, WalkState);
788 
789 
790     if (!WalkState)
791     {
792         return_VOID;
793     }
794 
795     if (WalkState->DescriptorType != ACPI_DESC_TYPE_WALK)
796     {
797         ACPI_ERROR ((AE_INFO, "%p is not a valid walk state",
798             WalkState));
799         return_VOID;
800     }
801 
802     /* There should not be any open scopes */
803 
804     if (WalkState->ParserState.Scope)
805     {
806         ACPI_ERROR ((AE_INFO, "%p walk still has a scope list",
807             WalkState));
808         AcpiPsCleanupScope (&WalkState->ParserState);
809     }
810 
811     /* Always must free any linked control states */
812 
813     while (WalkState->ControlState)
814     {
815         State = WalkState->ControlState;
816         WalkState->ControlState = State->Common.Next;
817 
818         AcpiUtDeleteGenericState (State);
819     }
820 
821     /* Always must free any linked parse states */
822 
823     while (WalkState->ScopeInfo)
824     {
825         State = WalkState->ScopeInfo;
826         WalkState->ScopeInfo = State->Common.Next;
827 
828         AcpiUtDeleteGenericState (State);
829     }
830 
831     /* Always must free any stacked result states */
832 
833     while (WalkState->Results)
834     {
835         State = WalkState->Results;
836         WalkState->Results = State->Common.Next;
837 
838         AcpiUtDeleteGenericState (State);
839     }
840 
841     ACPI_FREE (WalkState);
842     return_VOID;
843 }
844