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 - 2013, 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
  55 acpi_ds_result_stack_push(struct acpi_walk_state *walk_state);
  56 static acpi_status acpi_ds_result_stack_pop(struct acpi_walk_state *walk_state);
  57
  58 /*******************************************************************************
  59  *
  60  * FUNCTION:    acpi_ds_result_pop
  61  *
  62  * PARAMETERS:  object              - Where to return the popped object
  63  *              walk_state          - Current Walk state
  64  *
  65  * RETURN:      Status
  66  *
  67  * DESCRIPTION: Pop an object off the top of this walk's result stack
  68  *
  69  ******************************************************************************/
  70
  71 acpi_status
  72 acpi_ds_result_pop(union acpi_operand_object **object,
  73                    struct acpi_walk_state *walk_state)
  74 {
  75         u32 index;
  76         union acpi_generic_state *state;
  77         acpi_status status;
  78
  79         ACPI_FUNCTION_NAME(ds_result_pop);
  80
  81         state = walk_state->results;
  82
  83         /* Incorrect state of result stack */
  84
  85         if (state && !walk_state->result_count) {
  86                 ACPI_ERROR((AE_INFO, "No results on result stack"));
  87                 return (AE_AML_INTERNAL);
  88         }
  89
  90         if (!state && walk_state->result_count) {
  91                 ACPI_ERROR((AE_INFO, "No result state for result stack"));
  92                 return (AE_AML_INTERNAL);
  93         }
  94
  95         /* Empty result stack */
  96
  97         if (!state) {
  98                 ACPI_ERROR((AE_INFO, "Result stack is empty! State=%p",
  99                             walk_state));
 100                 return (AE_AML_NO_RETURN_VALUE);
 101         }
 102
 103         /* Return object of the top element and clean that top element result stack */
 104
 105         walk_state->result_count--;
 106         index = (u32)walk_state->result_count % ACPI_RESULTS_FRAME_OBJ_NUM;
 107
 108         *object = state->results.obj_desc[index];
 109         if (!*object) {
 110                 ACPI_ERROR((AE_INFO,
 111                             "No result objects on result stack, State=%p",
 112                             walk_state));
 113                 return (AE_AML_NO_RETURN_VALUE);
 114         }
 115
 116         state->results.obj_desc[index] = NULL;
 117         if (index == 0) {
 118                 status = acpi_ds_result_stack_pop(walk_state);
 119                 if (ACPI_FAILURE(status)) {
 120                         return (status);
 121                 }
 122         }
 123
 124         ACPI_DEBUG_PRINT((ACPI_DB_EXEC,
 125                           "Obj=%p [%s] Index=%X State=%p Num=%X\n", *object,
 126                           acpi_ut_get_object_type_name(*object),
 127                           index, walk_state, walk_state->result_count));
 128
 129         return (AE_OK);
 130 }
 131
 132 /*******************************************************************************
 133  *
 134  * FUNCTION:    acpi_ds_result_push
 135  *
 136  * PARAMETERS:  object              - Where to return the popped object
 137  *              walk_state          - Current Walk state
 138  *
 139  * RETURN:      Status
 140  *
 141  * DESCRIPTION: Push an object onto the current result stack
 142  *
 143  ******************************************************************************/
 144
 145 acpi_status
 146 acpi_ds_result_push(union acpi_operand_object * object,
 147                     struct acpi_walk_state * walk_state)
 148 {
 149         union acpi_generic_state *state;
 150         acpi_status status;
 151         u32 index;
 152
 153         ACPI_FUNCTION_NAME(ds_result_push);
 154
 155         if (walk_state->result_count > walk_state->result_size) {
 156                 ACPI_ERROR((AE_INFO, "Result stack is full"));
 157                 return (AE_AML_INTERNAL);
 158         } else if (walk_state->result_count == walk_state->result_size) {
 159
 160                 /* Extend the result stack */
 161
 162                 status = acpi_ds_result_stack_push(walk_state);
 163                 if (ACPI_FAILURE(status)) {
 164                         ACPI_ERROR((AE_INFO,
 165                                     "Failed to extend the result stack"));
 166                         return (status);
 167                 }
 168         }
 169
 170         if (!(walk_state->result_count < walk_state->result_size)) {
 171                 ACPI_ERROR((AE_INFO, "No free elements in result stack"));
 172                 return (AE_AML_INTERNAL);
 173         }
 174
 175         state = walk_state->results;
 176         if (!state) {
 177                 ACPI_ERROR((AE_INFO, "No result stack frame during push"));
 178                 return (AE_AML_INTERNAL);
 179         }
 180
 181         if (!object) {
 182                 ACPI_ERROR((AE_INFO,
 183                             "Null Object! Obj=%p State=%p Num=%u",
 184                             object, walk_state, walk_state->result_count));
 185                 return (AE_BAD_PARAMETER);
 186         }
 187
 188         /* Assign the address of object to the top free element of result stack */
 189
 190         index = (u32)walk_state->result_count % ACPI_RESULTS_FRAME_OBJ_NUM;
 191         state->results.obj_desc[index] = object;
 192         walk_state->result_count++;
 193
 194         ACPI_DEBUG_PRINT((ACPI_DB_EXEC, "Obj=%p [%s] State=%p Num=%X Cur=%X\n",
 195                           object,
 196                           acpi_ut_get_object_type_name((union
 197                                                         acpi_operand_object *)
 198                                                        object), walk_state,
 199                           walk_state->result_count,
 200                           walk_state->current_result));
 201
 202         return (AE_OK);
 203 }
 204
 205 /*******************************************************************************
 206  *
 207  * FUNCTION:    acpi_ds_result_stack_push
 208  *
 209  * PARAMETERS:  walk_state          - Current Walk state
 210  *
 211  * RETURN:      Status
 212  *
 213  * DESCRIPTION: Push an object onto the walk_state result stack
 214  *
 215  ******************************************************************************/
 216
 217 static acpi_status acpi_ds_result_stack_push(struct acpi_walk_state *walk_state)
 218 {
 219         union acpi_generic_state *state;
 220
 221         ACPI_FUNCTION_NAME(ds_result_stack_push);
 222
 223         /* Check for stack overflow */
 224
 225         if (((u32) walk_state->result_size + ACPI_RESULTS_FRAME_OBJ_NUM) >
 226             ACPI_RESULTS_OBJ_NUM_MAX) {
 227                 ACPI_ERROR((AE_INFO, "Result stack overflow: State=%p Num=%u",
 228                             walk_state, walk_state->result_size));
 229                 return (AE_STACK_OVERFLOW);
 230         }
 231
 232         state = acpi_ut_create_generic_state();
 233         if (!state) {
 234                 return (AE_NO_MEMORY);
 235         }
 236
 237         state->common.descriptor_type = ACPI_DESC_TYPE_STATE_RESULT;
 238         acpi_ut_push_generic_state(&walk_state->results, state);
 239
 240         /* Increase the length of the result stack by the length of frame */
 241
 242         walk_state->result_size += ACPI_RESULTS_FRAME_OBJ_NUM;
 243
 244         ACPI_DEBUG_PRINT((ACPI_DB_EXEC, "Results=%p State=%p\n",
 245                           state, walk_state));
 246
 247         return (AE_OK);
 248 }
 249
 250 /*******************************************************************************
 251  *
 252  * FUNCTION:    acpi_ds_result_stack_pop
 253  *
 254  * PARAMETERS:  walk_state          - Current Walk state
 255  *
 256  * RETURN:      Status
 257  *
 258  * DESCRIPTION: Pop an object off of the walk_state result stack
 259  *
 260  ******************************************************************************/
 261
 262 static acpi_status acpi_ds_result_stack_pop(struct acpi_walk_state *walk_state)
 263 {
 264         union acpi_generic_state *state;
 265
 266         ACPI_FUNCTION_NAME(ds_result_stack_pop);
 267
 268         /* Check for stack underflow */
 269
 270         if (walk_state->results == NULL) {
 271                 ACPI_DEBUG_PRINT((ACPI_DB_EXEC,
 272                                   "Result stack underflow - State=%p\n",
 273                                   walk_state));
 274                 return (AE_AML_NO_OPERAND);
 275         }
 276
 277         if (walk_state->result_size < ACPI_RESULTS_FRAME_OBJ_NUM) {
 278                 ACPI_ERROR((AE_INFO, "Insufficient result stack size"));
 279                 return (AE_AML_INTERNAL);
 280         }
 281
 282         state = acpi_ut_pop_generic_state(&walk_state->results);
 283         acpi_ut_delete_generic_state(state);
 284
 285         /* Decrease the length of result stack by the length of frame */
 286
 287         walk_state->result_size -= ACPI_RESULTS_FRAME_OBJ_NUM;
 288
 289         ACPI_DEBUG_PRINT((ACPI_DB_EXEC,
 290                           "Result=%p RemainingResults=%X State=%p\n",
 291                           state, walk_state->result_count, walk_state));
 292
 293         return (AE_OK);
 294 }
 295
 296 /*******************************************************************************
 297  *
 298  * FUNCTION:    acpi_ds_obj_stack_push
 299  *
 300  * PARAMETERS:  object              - Object to push
 301  *              walk_state          - Current Walk state
 302  *
 303  * RETURN:      Status
 304  *
 305  * DESCRIPTION: Push an object onto this walk's object/operand stack
 306  *
 307  ******************************************************************************/
 308
 309 acpi_status
 310 acpi_ds_obj_stack_push(void *object, struct acpi_walk_state * walk_state)
 311 {
 312         ACPI_FUNCTION_NAME(ds_obj_stack_push);
 313
 314         /* Check for stack overflow */
 315
 316         if (walk_state->num_operands >= ACPI_OBJ_NUM_OPERANDS) {
 317                 ACPI_ERROR((AE_INFO,
 318                             "Object stack overflow! Obj=%p State=%p #Ops=%u",
 319                             object, walk_state, walk_state->num_operands));
 320                 return (AE_STACK_OVERFLOW);
 321         }
 322
 323         /* Put the object onto the stack */
 324
 325         walk_state->operands[walk_state->operand_index] = object;
 326         walk_state->num_operands++;
 327
 328         /* For the usual order of filling the operand stack */
 329
 330         walk_state->operand_index++;
 331
 332         ACPI_DEBUG_PRINT((ACPI_DB_EXEC, "Obj=%p [%s] State=%p #Ops=%X\n",
 333                           object,
 334                           acpi_ut_get_object_type_name((union
 335                                                         acpi_operand_object *)
 336                                                        object), walk_state,
 337                           walk_state->num_operands));
 338
 339         return (AE_OK);
 340 }
 341
 342 /*******************************************************************************
 343  *
 344  * FUNCTION:    acpi_ds_obj_stack_pop
 345  *
 346  * PARAMETERS:  pop_count           - Number of objects/entries to pop
 347  *              walk_state          - Current Walk state
 348  *
 349  * RETURN:      Status
 350  *
 351  * DESCRIPTION: Pop this walk's object stack. Objects on the stack are NOT
 352  *              deleted by this routine.
 353  *
 354  ******************************************************************************/
 355
 356 acpi_status
 357 acpi_ds_obj_stack_pop(u32 pop_count, struct acpi_walk_state * walk_state)
 358 {
 359         u32 i;
 360
 361         ACPI_FUNCTION_NAME(ds_obj_stack_pop);
 362
 363         for (i = 0; i < pop_count; i++) {
 364
 365                 /* Check for stack underflow */
 366
 367                 if (walk_state->num_operands == 0) {
 368                         ACPI_ERROR((AE_INFO,
 369                                     "Object stack underflow! Count=%X State=%p #Ops=%u",
 370                                     pop_count, walk_state,
 371                                     walk_state->num_operands));
 372                         return (AE_STACK_UNDERFLOW);
 373                 }
 374
 375                 /* Just set the stack entry to null */
 376
 377                 walk_state->num_operands--;
 378                 walk_state->operands[walk_state->num_operands] = NULL;
 379         }
 380
 381         ACPI_DEBUG_PRINT((ACPI_DB_EXEC, "Count=%X State=%p #Ops=%u\n",
 382                           pop_count, walk_state, walk_state->num_operands));
 383
 384         return (AE_OK);
 385 }
 386
 387 /*******************************************************************************
 388  *
 389  * FUNCTION:    acpi_ds_obj_stack_pop_and_delete
 390  *
 391  * PARAMETERS:  pop_count           - Number of objects/entries to pop
 392  *              walk_state          - Current Walk state
 393  *
 394  * RETURN:      Status
 395  *
 396  * DESCRIPTION: Pop this walk's object stack and delete each object that is
 397  *              popped off.
 398  *
 399  ******************************************************************************/
 400
 401 void
 402 acpi_ds_obj_stack_pop_and_delete(u32 pop_count,
 403                                  struct acpi_walk_state *walk_state)
 404 {
 405         s32 i;
 406         union acpi_operand_object *obj_desc;
 407
 408         ACPI_FUNCTION_NAME(ds_obj_stack_pop_and_delete);
 409
 410         if (pop_count == 0) {
 411                 return;
 412         }
 413
 414         for (i = (s32) pop_count - 1; i >= 0; i--) {
 415                 if (walk_state->num_operands == 0) {
 416                         return;
 417                 }
 418
 419                 /* Pop the stack and delete an object if present in this stack entry */
 420
 421                 walk_state->num_operands--;
 422                 obj_desc = walk_state->operands[i];
 423                 if (obj_desc) {
 424                         acpi_ut_remove_reference(walk_state->operands[i]);
 425                         walk_state->operands[i] = NULL;
 426                 }
 427         }
 428
 429         ACPI_DEBUG_PRINT((ACPI_DB_EXEC, "Count=%X State=%p #Ops=%X\n",
 430                           pop_count, walk_state, walk_state->num_operands));
 431 }
 432
 433 /*******************************************************************************
 434  *
 435  * FUNCTION:    acpi_ds_get_current_walk_state
 436  *
 437  * PARAMETERS:  thread          - Get current active state for this Thread
 438  *
 439  * RETURN:      Pointer to the current walk state
 440  *
 441  * DESCRIPTION: Get the walk state that is at the head of the list (the "current"
 442  *              walk state.)
 443  *
 444  ******************************************************************************/
 445
 446 struct acpi_walk_state *acpi_ds_get_current_walk_state(struct acpi_thread_state
 447                                                        *thread)
 448 {
 449         ACPI_FUNCTION_NAME(ds_get_current_walk_state);
 450
 451         if (!thread) {
 452                 return (NULL);
 453         }
 454
 455         ACPI_DEBUG_PRINT((ACPI_DB_PARSE, "Current WalkState %p\n",
 456                           thread->walk_state_list));
 457
 458         return (thread->walk_state_list);
 459 }
 460
 461 /*******************************************************************************
 462  *
 463  * FUNCTION:    acpi_ds_push_walk_state
 464  *
 465  * PARAMETERS:  walk_state      - State to push
 466  *              thread          - Thread state object
 467  *
 468  * RETURN:      None
 469  *
 470  * DESCRIPTION: Place the Thread state at the head of the state list
 471  *
 472  ******************************************************************************/
 473
 474 void
 475 acpi_ds_push_walk_state(struct acpi_walk_state *walk_state,
 476                         struct acpi_thread_state *thread)
 477 {
 478         ACPI_FUNCTION_TRACE(ds_push_walk_state);
 479
 480         walk_state->next = thread->walk_state_list;
 481         thread->walk_state_list = walk_state;
 482
 483         return_VOID;
 484 }
 485
 486 /*******************************************************************************
 487  *
 488  * FUNCTION:    acpi_ds_pop_walk_state
 489  *
 490  * PARAMETERS:  thread      - Current thread state
 491  *
 492  * RETURN:      A walk_state object popped from the thread's stack
 493  *
 494  * DESCRIPTION: Remove and return the walkstate object that is at the head of
 495  *              the walk stack for the given walk list. NULL indicates that
 496  *              the list is empty.
 497  *
 498  ******************************************************************************/
 499
 500 struct acpi_walk_state *acpi_ds_pop_walk_state(struct acpi_thread_state *thread)
 501 {
 502         struct acpi_walk_state *walk_state;
 503
 504         ACPI_FUNCTION_TRACE(ds_pop_walk_state);
 505
 506         walk_state = thread->walk_state_list;
 507
 508         if (walk_state) {
 509
 510                 /* Next walk state becomes the current walk state */
 511
 512                 thread->walk_state_list = walk_state->next;
 513
 514                 /*
 515                  * Don't clear the NEXT field, this serves as an indicator
 516                  * that there is a parent WALK STATE
 517                  * Do Not: walk_state->Next = NULL;
 518                  */
 519         }
 520
 521         return_PTR(walk_state);
 522 }
 523
 524 /*******************************************************************************
 525  *
 526  * FUNCTION:    acpi_ds_create_walk_state
 527  *
 528  * PARAMETERS:  owner_id        - ID for object creation
 529  *              origin          - Starting point for this walk
 530  *              method_desc     - Method object
 531  *              thread          - Current thread state
 532  *
 533  * RETURN:      Pointer to the new walk state.
 534  *
 535  * DESCRIPTION: Allocate and initialize a new walk state. The current walk
 536  *              state is set to this new state.
 537  *
 538  ******************************************************************************/
 539
 540 struct acpi_walk_state *acpi_ds_create_walk_state(acpi_owner_id owner_id,
 541                                                   union acpi_parse_object
 542                                                   *origin,
 543                                                   union acpi_operand_object
 544                                                   *method_desc,
 545                                                   struct acpi_thread_state
 546                                                   *thread)
 547 {
 548         struct acpi_walk_state *walk_state;
 549
 550         ACPI_FUNCTION_TRACE(ds_create_walk_state);
 551
 552         walk_state = ACPI_ALLOCATE_ZEROED(sizeof(struct acpi_walk_state));
 553         if (!walk_state) {
 554                 return_PTR(NULL);
 555         }
 556
 557         walk_state->descriptor_type = ACPI_DESC_TYPE_WALK;
 558         walk_state->method_desc = method_desc;
 559         walk_state->owner_id = owner_id;
 560         walk_state->origin = origin;
 561         walk_state->thread = thread;
 562
 563         walk_state->parser_state.start_op = origin;
 564
 565         /* Init the method args/local */
 566
 567 #if (!defined (ACPI_NO_METHOD_EXECUTION) && !defined (ACPI_CONSTANT_EVAL_ONLY))
 568         acpi_ds_method_data_init(walk_state);
 569 #endif
 570
 571         /* Put the new state at the head of the walk list */
 572
 573         if (thread) {
 574                 acpi_ds_push_walk_state(walk_state, thread);
 575         }
 576
 577         return_PTR(walk_state);
 578 }
 579
 580 /*******************************************************************************
 581  *
 582  * FUNCTION:    acpi_ds_init_aml_walk
 583  *
 584  * PARAMETERS:  walk_state      - New state to be initialized
 585  *              op              - Current parse op
 586  *              method_node     - Control method NS node, if any
 587  *              aml_start       - Start of AML
 588  *              aml_length      - Length of AML
 589  *              info            - Method info block (params, etc.)
 590  *              pass_number     - 1, 2, or 3
 591  *
 592  * RETURN:      Status
 593  *
 594  * DESCRIPTION: Initialize a walk state for a pass 1 or 2 parse tree walk
 595  *
 596  ******************************************************************************/
 597
 598 acpi_status
 599 acpi_ds_init_aml_walk(struct acpi_walk_state *walk_state,
 600                       union acpi_parse_object *op,
 601                       struct acpi_namespace_node *method_node,
 602                       u8 * aml_start,
 603                       u32 aml_length,
 604                       struct acpi_evaluate_info *info, u8 pass_number)
 605 {
 606         acpi_status status;
 607         struct acpi_parse_state *parser_state = &walk_state->parser_state;
 608         union acpi_parse_object *extra_op;
 609
 610         ACPI_FUNCTION_TRACE(ds_init_aml_walk);
 611
 612         walk_state->parser_state.aml =
 613             walk_state->parser_state.aml_start = aml_start;
 614         walk_state->parser_state.aml_end =
 615             walk_state->parser_state.pkg_end = aml_start + aml_length;
 616
 617         /* The next_op of the next_walk will be the beginning of the method */
 618
 619         walk_state->next_op = NULL;
 620         walk_state->pass_number = pass_number;
 621
 622         if (info) {
 623                 walk_state->params = info->parameters;
 624                 walk_state->caller_return_desc = &info->return_object;
 625         }
 626
 627         status = acpi_ps_init_scope(&walk_state->parser_state, op);
 628         if (ACPI_FAILURE(status)) {
 629                 return_ACPI_STATUS(status);
 630         }
 631
 632         if (method_node) {
 633                 walk_state->parser_state.start_node = method_node;
 634                 walk_state->walk_type = ACPI_WALK_METHOD;
 635                 walk_state->method_node = method_node;
 636                 walk_state->method_desc =
 637                     acpi_ns_get_attached_object(method_node);
 638
 639                 /* Push start scope on scope stack and make it current  */
 640
 641                 status =
 642                     acpi_ds_scope_stack_push(method_node, ACPI_TYPE_METHOD,
 643                                              walk_state);
 644                 if (ACPI_FAILURE(status)) {
 645                         return_ACPI_STATUS(status);
 646                 }
 647
 648                 /* Init the method arguments */
 649
 650                 status = acpi_ds_method_data_init_args(walk_state->params,
 651                                                        ACPI_METHOD_NUM_ARGS,
 652                                                        walk_state);
 653                 if (ACPI_FAILURE(status)) {
 654                         return_ACPI_STATUS(status);
 655                 }
 656         } else {
 657                 /*
 658                  * Setup the current scope.
 659                  * Find a Named Op that has a namespace node associated with it.
 660                  * search upwards from this Op. Current scope is the first
 661                  * Op with a namespace node.
 662                  */
 663                 extra_op = parser_state->start_op;
 664                 while (extra_op && !extra_op->common.node) {
 665                         extra_op = extra_op->common.parent;
 666                 }
 667
 668                 if (!extra_op) {
 669                         parser_state->start_node = NULL;
 670                 } else {
 671                         parser_state->start_node = extra_op->common.node;
 672                 }
 673
 674                 if (parser_state->start_node) {
 675
 676                         /* Push start scope on scope stack and make it current  */
 677
 678                         status =
 679                             acpi_ds_scope_stack_push(parser_state->start_node,
 680                                                      parser_state->start_node->
 681                                                      type, walk_state);
 682                         if (ACPI_FAILURE(status)) {
 683                                 return_ACPI_STATUS(status);
 684                         }
 685                 }
 686         }
 687
 688         status = acpi_ds_init_callbacks(walk_state, pass_number);
 689         return_ACPI_STATUS(status);
 690 }
 691
 692 /*******************************************************************************
 693  *
 694  * FUNCTION:    acpi_ds_delete_walk_state
 695  *
 696  * PARAMETERS:  walk_state      - State to delete
 697  *
 698  * RETURN:      Status
 699  *
 700  * DESCRIPTION: Delete a walk state including all internal data structures
 701  *
 702  ******************************************************************************/
 703
 704 void acpi_ds_delete_walk_state(struct acpi_walk_state *walk_state)
 705 {
 706         union acpi_generic_state *state;
 707
 708         ACPI_FUNCTION_TRACE_PTR(ds_delete_walk_state, walk_state);
 709
 710         if (!walk_state) {
 711                 return_VOID;
 712         }
 713
 714         if (walk_state->descriptor_type != ACPI_DESC_TYPE_WALK) {
 715                 ACPI_ERROR((AE_INFO, "%p is not a valid walk state",
 716                             walk_state));
 717                 return_VOID;
 718         }
 719
 720         /* There should not be any open scopes */
 721
 722         if (walk_state->parser_state.scope) {
 723                 ACPI_ERROR((AE_INFO, "%p walk still has a scope list",
 724                             walk_state));
 725                 acpi_ps_cleanup_scope(&walk_state->parser_state);
 726         }
 727
 728         /* Always must free any linked control states */
 729
 730         while (walk_state->control_state) {
 731                 state = walk_state->control_state;
 732                 walk_state->control_state = state->common.next;
 733
 734                 acpi_ut_delete_generic_state(state);
 735         }
 736
 737         /* Always must free any linked parse states */
 738
 739         while (walk_state->scope_info) {
 740                 state = walk_state->scope_info;
 741                 walk_state->scope_info = state->common.next;
 742
 743                 acpi_ut_delete_generic_state(state);
 744         }
 745
 746         /* Always must free any stacked result states */
 747
 748         while (walk_state->results) {
 749                 state = walk_state->results;
 750                 walk_state->results = state->common.next;
 751
 752                 acpi_ut_delete_generic_state(state);
 753         }
 754
 755         ACPI_FREE(walk_state);
 756         return_VOID;
 757 }