release/src-rt-6.x.4708/linux/linux-2.6.36/drivers/acpi/acpica/dswstate.c

   1 /******************************************************************************
   2  *
   3  * Module Name: dswstate - Dispatcher parse tree walk management routines
   4  *
   5  *****************************************************************************/
   6
   7 /*
   8  * Copyright (C) 2000 - 2010, 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 #include <acpi/acpi.h>
  45 #include "accommon.h"
  46 #include "acparser.h"
  47 #include "acdispat.h"
  48 #include "acnamesp.h"
  49
  50 #define _COMPONENT          ACPI_DISPATCHER
  51 ACPI_MODULE_NAME("dswstate")
  52
  53   /* Local prototypes */
  54 static acpi_status acpi_ds_result_stack_push(struct acpi_walk_state *ws);
  55 static acpi_status acpi_ds_result_stack_pop(struct acpi_walk_state *ws);
  56
  57 /*******************************************************************************
  58  *
  59  * FUNCTION:    acpi_ds_result_pop
  60  *
  61  * PARAMETERS:  Object              - Where to return the popped object
  62  *              walk_state          - Current Walk state
  63  *
  64  * RETURN:      Status
  65  *
  66  * DESCRIPTION: Pop an object off the top of this walk's result stack
  67  *
  68  ******************************************************************************/
  69
  70 acpi_status
  71 acpi_ds_result_pop(union acpi_operand_object **object,
  72                    struct acpi_walk_state *walk_state)
  73 {
  74         u32 index;
  75         union acpi_generic_state *state;
  76         acpi_status status;
  77
  78         ACPI_FUNCTION_NAME(ds_result_pop);
  79
  80         state = walk_state->results;
  81
  82         /* Incorrect state of result stack */
  83
  84         if (state && !walk_state->result_count) {
  85                 ACPI_ERROR((AE_INFO, "No results on result stack"));
  86                 return (AE_AML_INTERNAL);
  87         }
  88
  89         if (!state && walk_state->result_count) {
  90                 ACPI_ERROR((AE_INFO, "No result state for result stack"));
  91                 return (AE_AML_INTERNAL);
  92         }
  93
  94         /* Empty result stack */
  95
  96         if (!state) {
  97                 ACPI_ERROR((AE_INFO, "Result stack is empty! State=%p",
  98                             walk_state));
  99                 return (AE_AML_NO_RETURN_VALUE);
 100         }
 101
 102         /* Return object of the top element and clean that top element result stack */
 103
 104         walk_state->result_count--;
 105         index = (u32)walk_state->result_count % ACPI_RESULTS_FRAME_OBJ_NUM;
 106
 107         *object = state->results.obj_desc[index];
 108         if (!*object) {
 109                 ACPI_ERROR((AE_INFO,
 110                             "No result objects on result stack, State=%p",
 111                             walk_state));
 112                 return (AE_AML_NO_RETURN_VALUE);
 113         }
 114
 115         state->results.obj_desc[index] = NULL;
 116         if (index == 0) {
 117                 status = acpi_ds_result_stack_pop(walk_state);
 118                 if (ACPI_FAILURE(status)) {
 119                         return (status);
 120                 }
 121         }
 122
 123         ACPI_DEBUG_PRINT((ACPI_DB_EXEC,
 124                           "Obj=%p [%s] Index=%X State=%p Num=%X\n", *object,
 125                           acpi_ut_get_object_type_name(*object),
 126                           index, walk_state, walk_state->result_count));
 127
 128         return (AE_OK);
 129 }
 130
 131 /*******************************************************************************
 132  *
 133  * FUNCTION:    acpi_ds_result_push
 134  *
 135  * PARAMETERS:  Object              - Where to return the popped object
 136  *              walk_state          - Current Walk state
 137  *
 138  * RETURN:      Status
 139  *
 140  * DESCRIPTION: Push an object onto the current result stack
 141  *
 142  ******************************************************************************/
 143
 144 acpi_status
 145 acpi_ds_result_push(union acpi_operand_object * object,
 146                     struct acpi_walk_state * walk_state)
 147 {
 148         union acpi_generic_state *state;
 149         acpi_status status;
 150         u32 index;
 151
 152         ACPI_FUNCTION_NAME(ds_result_push);
 153
 154         if (walk_state->result_count > walk_state->result_size) {
 155                 ACPI_ERROR((AE_INFO, "Result stack is full"));
 156                 return (AE_AML_INTERNAL);
 157         } else if (walk_state->result_count == walk_state->result_size) {
 158
 159                 /* Extend the result stack */
 160
 161                 status = acpi_ds_result_stack_push(walk_state);
 162                 if (ACPI_FAILURE(status)) {
 163                         ACPI_ERROR((AE_INFO,
 164                                     "Failed to extend the result stack"));
 165                         return (status);
 166                 }
 167         }
 168
 169         if (!(walk_state->result_count < walk_state->result_size)) {
 170                 ACPI_ERROR((AE_INFO, "No free elements in result stack"));
 171                 return (AE_AML_INTERNAL);
 172         }
 173
 174         state = walk_state->results;
 175         if (!state) {
 176                 ACPI_ERROR((AE_INFO, "No result stack frame during push"));
 177                 return (AE_AML_INTERNAL);
 178         }
 179
 180         if (!object) {
 181                 ACPI_ERROR((AE_INFO,
 182                             "Null Object! Obj=%p State=%p Num=%u",
 183                             object, walk_state, walk_state->result_count));
 184                 return (AE_BAD_PARAMETER);
 185         }
 186
 187         /* Assign the address of object to the top free element of result stack */
 188
 189         index = (u32)walk_state->result_count % ACPI_RESULTS_FRAME_OBJ_NUM;
 190         state->results.obj_desc[index] = object;
 191         walk_state->result_count++;
 192
 193         ACPI_DEBUG_PRINT((ACPI_DB_EXEC, "Obj=%p [%s] State=%p Num=%X Cur=%X\n",
 194                           object,
 195                           acpi_ut_get_object_type_name((union
 196                                                         acpi_operand_object *)
 197                                                        object), walk_state,
 198                           walk_state->result_count,
 199                           walk_state->current_result));
 200
 201         return (AE_OK);
 202 }
 203
 204 /*******************************************************************************
 205  *
 206  * FUNCTION:    acpi_ds_result_stack_push
 207  *
 208  * PARAMETERS:  walk_state          - Current Walk state
 209  *
 210  * RETURN:      Status
 211  *
 212  * DESCRIPTION: Push an object onto the walk_state result stack
 213  *
 214  ******************************************************************************/
 215
 216 static acpi_status acpi_ds_result_stack_push(struct acpi_walk_state *walk_state)
 217 {
 218         union acpi_generic_state *state;
 219
 220         ACPI_FUNCTION_NAME(ds_result_stack_push);
 221
 222         /* Check for stack overflow */
 223
 224         if (((u32) walk_state->result_size + ACPI_RESULTS_FRAME_OBJ_NUM) >
 225             ACPI_RESULTS_OBJ_NUM_MAX) {
 226                 ACPI_ERROR((AE_INFO, "Result stack overflow: State=%p Num=%u",
 227                             walk_state, walk_state->result_size));
 228                 return (AE_STACK_OVERFLOW);
 229         }
 230
 231         state = acpi_ut_create_generic_state();
 232         if (!state) {
 233                 return (AE_NO_MEMORY);
 234         }
 235
 236         state->common.descriptor_type = ACPI_DESC_TYPE_STATE_RESULT;
 237         acpi_ut_push_generic_state(&walk_state->results, state);
 238
 239         /* Increase the length of the result stack by the length of frame */
 240
 241         walk_state->result_size += ACPI_RESULTS_FRAME_OBJ_NUM;
 242
 243         ACPI_DEBUG_PRINT((ACPI_DB_EXEC, "Results=%p State=%p\n",
 244                           state, walk_state));
 245
 246         return (AE_OK);
 247 }
 248
 249 /*******************************************************************************
 250  *
 251  * FUNCTION:    acpi_ds_result_stack_pop
 252  *
 253  * PARAMETERS:  walk_state          - Current Walk state
 254  *
 255  * RETURN:      Status
 256  *
 257  * DESCRIPTION: Pop an object off of the walk_state result stack
 258  *
 259  ******************************************************************************/
 260
 261 static acpi_status acpi_ds_result_stack_pop(struct acpi_walk_state *walk_state)
 262 {
 263         union acpi_generic_state *state;
 264
 265         ACPI_FUNCTION_NAME(ds_result_stack_pop);
 266
 267         /* Check for stack underflow */
 268
 269         if (walk_state->results == NULL) {
 270                 ACPI_DEBUG_PRINT((ACPI_DB_EXEC,
 271                                   "Result stack underflow - State=%p\n",
 272                                   walk_state));
 273                 return (AE_AML_NO_OPERAND);
 274         }
 275
 276         if (walk_state->result_size < ACPI_RESULTS_FRAME_OBJ_NUM) {
 277                 ACPI_ERROR((AE_INFO, "Insufficient result stack size"));
 278                 return (AE_AML_INTERNAL);
 279         }
 280
 281         state = acpi_ut_pop_generic_state(&walk_state->results);
 282         acpi_ut_delete_generic_state(state);
 283
 284         /* Decrease the length of result stack by the length of frame */
 285
 286         walk_state->result_size -= ACPI_RESULTS_FRAME_OBJ_NUM;
 287
 288         ACPI_DEBUG_PRINT((ACPI_DB_EXEC,
 289                           "Result=%p RemainingResults=%X State=%p\n",
 290                           state, walk_state->result_count, walk_state));
 291
 292         return (AE_OK);
 293 }
 294
 295 /*******************************************************************************
 296  *
 297  * FUNCTION:    acpi_ds_obj_stack_push
 298  *
 299  * PARAMETERS:  Object              - Object to push
 300  *              walk_state          - Current Walk state
 301  *
 302  * RETURN:      Status
 303  *
 304  * DESCRIPTION: Push an object onto this walk's object/operand stack
 305  *
 306  ******************************************************************************/
 307
 308 acpi_status
 309 acpi_ds_obj_stack_push(void *object, struct acpi_walk_state * walk_state)
 310 {
 311         ACPI_FUNCTION_NAME(ds_obj_stack_push);
 312
 313         /* Check for stack overflow */
 314
 315         if (walk_state->num_operands >= ACPI_OBJ_NUM_OPERANDS) {
 316                 ACPI_ERROR((AE_INFO,
 317                             "Object stack overflow! Obj=%p State=%p #Ops=%u",
 318                             object, walk_state, walk_state->num_operands));
 319                 return (AE_STACK_OVERFLOW);
 320         }
 321
 322         /* Put the object onto the stack */
 323
 324         walk_state->operands[walk_state->operand_index] = object;
 325         walk_state->num_operands++;
 326
 327         /* For the usual order of filling the operand stack */
 328
 329         walk_state->operand_index++;
 330
 331         ACPI_DEBUG_PRINT((ACPI_DB_EXEC, "Obj=%p [%s] State=%p #Ops=%X\n",
 332                           object,
 333                           acpi_ut_get_object_type_name((union
 334                                                         acpi_operand_object *)
 335                                                        object), walk_state,
 336                           walk_state->num_operands));
 337
 338         return (AE_OK);
 339 }
 340
 341 /*******************************************************************************
 342  *
 343  * FUNCTION:    acpi_ds_obj_stack_pop
 344  *
 345  * PARAMETERS:  pop_count           - Number of objects/entries to pop
 346  *              walk_state          - Current Walk state
 347  *
 348  * RETURN:      Status
 349  *
 350  * DESCRIPTION: Pop this walk's object stack.  Objects on the stack are NOT
 351  *              deleted by this routine.
 352  *
 353  ******************************************************************************/
 354
 355 acpi_status
 356 acpi_ds_obj_stack_pop(u32 pop_count, struct acpi_walk_state * walk_state)
 357 {
 358         u32 i;
 359
 360         ACPI_FUNCTION_NAME(ds_obj_stack_pop);
 361
 362         for (i = 0; i < pop_count; i++) {
 363
 364                 /* Check for stack underflow */
 365
 366                 if (walk_state->num_operands == 0) {
 367                         ACPI_ERROR((AE_INFO,
 368                                     "Object stack underflow! Count=%X State=%p #Ops=%u",
 369                                     pop_count, walk_state,
 370                                     walk_state->num_operands));
 371                         return (AE_STACK_UNDERFLOW);
 372                 }
 373
 374                 /* Just set the stack entry to null */
 375
 376                 walk_state->num_operands--;
 377                 walk_state->operands[walk_state->num_operands] = NULL;
 378         }
 379
 380         ACPI_DEBUG_PRINT((ACPI_DB_EXEC, "Count=%X State=%p #Ops=%u\n",
 381                           pop_count, walk_state, walk_state->num_operands));
 382
 383         return (AE_OK);
 384 }
 385
 386 /*******************************************************************************
 387  *
 388  * FUNCTION:    acpi_ds_obj_stack_pop_and_delete
 389  *
 390  * PARAMETERS:  pop_count           - Number of objects/entries to pop
 391  *              walk_state          - Current Walk state
 392  *
 393  * RETURN:      Status
 394  *
 395  * DESCRIPTION: Pop this walk's object stack and delete each object that is
 396  *              popped off.
 397  *
 398  ******************************************************************************/
 399
 400 void
 401 acpi_ds_obj_stack_pop_and_delete(u32 pop_count,
 402                                  struct acpi_walk_state *walk_state)
 403 {
 404         s32 i;
 405         union acpi_operand_object *obj_desc;
 406
 407         ACPI_FUNCTION_NAME(ds_obj_stack_pop_and_delete);
 408
 409         if (pop_count == 0) {
 410                 return;
 411         }
 412
 413         for (i = (s32) pop_count - 1; i >= 0; i--) {
 414                 if (walk_state->num_operands == 0) {
 415                         return;
 416                 }
 417
 418                 /* Pop the stack and delete an object if present in this stack entry */
 419
 420                 walk_state->num_operands--;
 421                 obj_desc = walk_state->operands[i];
 422                 if (obj_desc) {
 423                         acpi_ut_remove_reference(walk_state->operands[i]);
 424                         walk_state->operands[i] = NULL;
 425                 }
 426         }
 427
 428         ACPI_DEBUG_PRINT((ACPI_DB_EXEC, "Count=%X State=%p #Ops=%X\n",
 429                           pop_count, walk_state, walk_state->num_operands));
 430 }
 431
 432 /*******************************************************************************
 433  *
 434  * FUNCTION:    acpi_ds_get_current_walk_state
 435  *
 436  * PARAMETERS:  Thread          - Get current active state for this Thread
 437  *
 438  * RETURN:      Pointer to the current walk state
 439  *
 440  * DESCRIPTION: Get the walk state that is at the head of the list (the "current"
 441  *              walk state.)
 442  *
 443  ******************************************************************************/
 444
 445 struct acpi_walk_state *acpi_ds_get_current_walk_state(struct acpi_thread_state
 446                                                        *thread)
 447 {
 448         ACPI_FUNCTION_NAME(ds_get_current_walk_state);
 449
 450         if (!thread) {
 451                 return (NULL);
 452         }
 453
 454         ACPI_DEBUG_PRINT((ACPI_DB_PARSE, "Current WalkState %p\n",
 455                           thread->walk_state_list));
 456
 457         return (thread->walk_state_list);
 458 }
 459
 460 /*******************************************************************************
 461  *
 462  * FUNCTION:    acpi_ds_push_walk_state
 463  *
 464  * PARAMETERS:  walk_state      - State to push
 465  *              Thread          - Thread state object
 466  *
 467  * RETURN:      None
 468  *
 469  * DESCRIPTION: Place the Thread state at the head of the state list
 470  *
 471  ******************************************************************************/
 472
 473 void
 474 acpi_ds_push_walk_state(struct acpi_walk_state *walk_state,
 475                         struct acpi_thread_state *thread)
 476 {
 477         ACPI_FUNCTION_TRACE(ds_push_walk_state);
 478
 479         walk_state->next = thread->walk_state_list;
 480         thread->walk_state_list = walk_state;
 481
 482         return_VOID;
 483 }
 484
 485 /*******************************************************************************
 486  *
 487  * FUNCTION:    acpi_ds_pop_walk_state
 488  *
 489  * PARAMETERS:  Thread      - Current thread state
 490  *
 491  * RETURN:      A walk_state object popped from the thread's stack
 492  *
 493  * DESCRIPTION: Remove and return the walkstate object that is at the head of
 494  *              the walk stack for the given walk list.  NULL indicates that
 495  *              the list is empty.
 496  *
 497  ******************************************************************************/
 498
 499 struct acpi_walk_state *acpi_ds_pop_walk_state(struct acpi_thread_state *thread)
 500 {
 501         struct acpi_walk_state *walk_state;
 502
 503         ACPI_FUNCTION_TRACE(ds_pop_walk_state);
 504
 505         walk_state = thread->walk_state_list;
 506
 507         if (walk_state) {
 508
 509                 /* Next walk state becomes the current walk state */
 510
 511                 thread->walk_state_list = walk_state->next;
 512
 513                 /*
 514                  * Don't clear the NEXT field, this serves as an indicator
 515                  * that there is a parent WALK STATE
 516                  * Do Not: walk_state->Next = NULL;
 517                  */
 518         }
 519
 520         return_PTR(walk_state);
 521 }
 522
 523 /*******************************************************************************
 524  *
 525  * FUNCTION:    acpi_ds_create_walk_state
 526  *
 527  * PARAMETERS:  owner_id        - ID for object creation
 528  *              Origin          - Starting point for this walk
 529  *              method_desc     - Method object
 530  *              Thread          - Current thread state
 531  *
 532  * RETURN:      Pointer to the new walk state.
 533  *
 534  * DESCRIPTION: Allocate and initialize a new walk state.  The current walk
 535  *              state is set to this new state.
 536  *
 537  ******************************************************************************/
 538
 539 struct acpi_walk_state *acpi_ds_create_walk_state(acpi_owner_id owner_id, union acpi_parse_object
 540                                                   *origin, union acpi_operand_object
 541                                                   *method_desc, struct acpi_thread_state
 542                                                   *thread)
 543 {
 544         struct acpi_walk_state *walk_state;
 545
 546         ACPI_FUNCTION_TRACE(ds_create_walk_state);
 547
 548         walk_state = ACPI_ALLOCATE_ZEROED(sizeof(struct acpi_walk_state));
 549         if (!walk_state) {
 550                 return_PTR(NULL);
 551         }
 552
 553         walk_state->descriptor_type = ACPI_DESC_TYPE_WALK;
 554         walk_state->method_desc = method_desc;
 555         walk_state->owner_id = owner_id;
 556         walk_state->origin = origin;
 557         walk_state->thread = thread;
 558
 559         walk_state->parser_state.start_op = origin;
 560
 561         /* Init the method args/local */
 562
 563 #if (!defined(ACPI_NO_METHOD_EXECUTION) && !defined(ACPI_CONSTANT_EVAL_ONLY))
 564         acpi_ds_method_data_init(walk_state);
 565 #endif
 566
 567         /* Put the new state at the head of the walk list */
 568
 569         if (thread) {
 570                 acpi_ds_push_walk_state(walk_state, thread);
 571         }
 572
 573         return_PTR(walk_state);
 574 }
 575
 576 /*******************************************************************************
 577  *
 578  * FUNCTION:    acpi_ds_init_aml_walk
 579  *
 580  * PARAMETERS:  walk_state      - New state to be initialized
 581  *              Op              - Current parse op
 582  *              method_node     - Control method NS node, if any
 583  *              aml_start       - Start of AML
 584  *              aml_length      - Length of AML
 585  *              Info            - Method info block (params, etc.)
 586  *              pass_number     - 1, 2, or 3
 587  *
 588  * RETURN:      Status
 589  *
 590  * DESCRIPTION: Initialize a walk state for a pass 1 or 2 parse tree walk
 591  *
 592  ******************************************************************************/
 593
 594 acpi_status
 595 acpi_ds_init_aml_walk(struct acpi_walk_state *walk_state,
 596                       union acpi_parse_object *op,
 597                       struct acpi_namespace_node *method_node,
 598                       u8 * aml_start,
 599                       u32 aml_length,
 600                       struct acpi_evaluate_info *info, u8 pass_number)
 601 {
 602         acpi_status status;
 603         struct acpi_parse_state *parser_state = &walk_state->parser_state;
 604         union acpi_parse_object *extra_op;
 605
 606         ACPI_FUNCTION_TRACE(ds_init_aml_walk);
 607
 608         walk_state->parser_state.aml =
 609             walk_state->parser_state.aml_start = aml_start;
 610         walk_state->parser_state.aml_end =
 611             walk_state->parser_state.pkg_end = aml_start + aml_length;
 612
 613         /* The next_op of the next_walk will be the beginning of the method */
 614
 615         walk_state->next_op = NULL;
 616         walk_state->pass_number = pass_number;
 617
 618         if (info) {
 619                 walk_state->params = info->parameters;
 620                 walk_state->caller_return_desc = &info->return_object;
 621         }
 622
 623         status = acpi_ps_init_scope(&walk_state->parser_state, op);
 624         if (ACPI_FAILURE(status)) {
 625                 return_ACPI_STATUS(status);
 626         }
 627
 628         if (method_node) {
 629                 walk_state->parser_state.start_node = method_node;
 630                 walk_state->walk_type = ACPI_WALK_METHOD;
 631                 walk_state->method_node = method_node;
 632                 walk_state->method_desc =
 633                     acpi_ns_get_attached_object(method_node);
 634
 635                 /* Push start scope on scope stack and make it current  */
 636
 637                 status =
 638                     acpi_ds_scope_stack_push(method_node, ACPI_TYPE_METHOD,
 639                                              walk_state);
 640                 if (ACPI_FAILURE(status)) {
 641                         return_ACPI_STATUS(status);
 642                 }
 643
 644                 /* Init the method arguments */
 645
 646                 status = acpi_ds_method_data_init_args(walk_state->params,
 647                                                        ACPI_METHOD_NUM_ARGS,
 648                                                        walk_state);
 649                 if (ACPI_FAILURE(status)) {
 650                         return_ACPI_STATUS(status);
 651                 }
 652         } else {
 653                 /*
 654                  * Setup the current scope.
 655                  * Find a Named Op that has a namespace node associated with it.
 656                  * search upwards from this Op.  Current scope is the first
 657                  * Op with a namespace node.
 658                  */
 659                 extra_op = parser_state->start_op;
 660                 while (extra_op && !extra_op->common.node) {
 661                         extra_op = extra_op->common.parent;
 662                 }
 663
 664                 if (!extra_op) {
 665                         parser_state->start_node = NULL;
 666                 } else {
 667                         parser_state->start_node = extra_op->common.node;
 668                 }
 669
 670                 if (parser_state->start_node) {
 671
 672                         /* Push start scope on scope stack and make it current  */
 673
 674                         status =
 675                             acpi_ds_scope_stack_push(parser_state->start_node,
 676                                                      parser_state->start_node->
 677                                                      type, walk_state);
 678                         if (ACPI_FAILURE(status)) {
 679                                 return_ACPI_STATUS(status);
 680                         }
 681                 }
 682         }
 683
 684         status = acpi_ds_init_callbacks(walk_state, pass_number);
 685         return_ACPI_STATUS(status);
 686 }
 687
 688 /*******************************************************************************
 689  *
 690  * FUNCTION:    acpi_ds_delete_walk_state
 691  *
 692  * PARAMETERS:  walk_state      - State to delete
 693  *
 694  * RETURN:      Status
 695  *
 696  * DESCRIPTION: Delete a walk state including all internal data structures
 697  *
 698  ******************************************************************************/
 699
 700 void acpi_ds_delete_walk_state(struct acpi_walk_state *walk_state)
 701 {
 702         union acpi_generic_state *state;
 703
 704         ACPI_FUNCTION_TRACE_PTR(ds_delete_walk_state, walk_state);
 705
 706         if (!walk_state) {
 707                 return;
 708         }
 709
 710         if (walk_state->descriptor_type != ACPI_DESC_TYPE_WALK) {
 711                 ACPI_ERROR((AE_INFO, "%p is not a valid walk state",
 712                             walk_state));
 713                 return;
 714         }
 715
 716         /* There should not be any open scopes */
 717
 718         if (walk_state->parser_state.scope) {
 719                 ACPI_ERROR((AE_INFO, "%p walk still has a scope list",
 720                             walk_state));
 721                 acpi_ps_cleanup_scope(&walk_state->parser_state);
 722         }
 723
 724         /* Always must free any linked control states */
 725
 726         while (walk_state->control_state) {
 727                 state = walk_state->control_state;
 728                 walk_state->control_state = state->common.next;
 729
 730                 acpi_ut_delete_generic_state(state);
 731         }
 732
 733         /* Always must free any linked parse states */
 734
 735         while (walk_state->scope_info) {
 736                 state = walk_state->scope_info;
 737                 walk_state->scope_info = state->common.next;
 738
 739                 acpi_ut_delete_generic_state(state);
 740         }
 741
 742         /* Always must free any stacked result states */
 743
 744         while (walk_state->results) {
 745                 state = walk_state->results;
 746                 walk_state->results = state->common.next;
 747
 748                 acpi_ut_delete_generic_state(state);
 749         }
 750
 751         ACPI_FREE(walk_state);
 752         return_VOID;
 753 }