git.oblomov.eu Git - linux-2.6/blob - drivers/acpi/dispatcher/dswstate.c

   1 /******************************************************************************
   2  *
   3  * Module Name: dswstate - Dispatcher parse tree walk management routines
   4  *
   5  *****************************************************************************/
   6
   7 /*
   8  * Copyright (C) 2000 - 2008, 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 <acpi/acparser.h>
  46 #include <acpi/acdispat.h>
  47 #include <acpi/acnamesp.h>
  48
  49 #define _COMPONENT          ACPI_DISPATCHER
  50 ACPI_MODULE_NAME("dswstate")
  51
  52   /* Local prototypes */
  53 static acpi_status acpi_ds_result_stack_push(struct acpi_walk_state *ws);
  54 static acpi_status acpi_ds_result_stack_pop(struct acpi_walk_state *ws);
  55
  56 /*******************************************************************************
  57  *
  58  * FUNCTION:    acpi_ds_result_pop
  59  *
  60  * PARAMETERS:  Object              - Where to return the popped object
  61  *              walk_state          - Current Walk state
  62  *
  63  * RETURN:      Status
  64  *
  65  * DESCRIPTION: Pop an object off the top of this walk's result stack
  66  *
  67  ******************************************************************************/
  68
  69 acpi_status
  70 acpi_ds_result_pop(union acpi_operand_object **object,
  71                    struct acpi_walk_state *walk_state)
  72 {
  73         u32 index;
  74         union acpi_generic_state *state;
  75         acpi_status status;
  76
  77         ACPI_FUNCTION_NAME(ds_result_pop);
  78
  79         state = walk_state->results;
  80
  81         /* Incorrect state of result stack */
  82
  83         if (state && !walk_state->result_count) {
  84                 ACPI_ERROR((AE_INFO, "No results on result stack"));
  85                 return (AE_AML_INTERNAL);
  86         }
  87
  88         if (!state && walk_state->result_count) {
  89                 ACPI_ERROR((AE_INFO, "No result state for result stack"));
  90                 return (AE_AML_INTERNAL);
  91         }
  92
  93         /* Empty result stack */
  94
  95         if (!state) {
  96                 ACPI_ERROR((AE_INFO, "Result stack is empty! State=%p",
  97                             walk_state));
  98                 return (AE_AML_NO_RETURN_VALUE);
  99         }
 100
 101         /* Return object of the top element and clean that top element result stack */
 102
 103         walk_state->result_count--;
 104         index = walk_state->result_count % ACPI_RESULTS_FRAME_OBJ_NUM;
 105
 106         *object = state->results.obj_desc[index];
 107         if (!*object) {
 108                 ACPI_ERROR((AE_INFO,
 109                             "No result objects on result stack, State=%p",
 110                             walk_state));
 111                 return (AE_AML_NO_RETURN_VALUE);
 112         }
 113
 114         state->results.obj_desc[index] = NULL;
 115         if (index == 0) {
 116                 status = acpi_ds_result_stack_pop(walk_state);
 117                 if (ACPI_FAILURE(status)) {
 118                         return (status);
 119                 }
 120         }
 121
 122         ACPI_DEBUG_PRINT((ACPI_DB_EXEC,
 123                           "Obj=%p [%s] Index=%X State=%p Num=%X\n", *object,
 124                           acpi_ut_get_object_type_name(*object),
 125                           index, walk_state, walk_state->result_count));
 126
 127         return (AE_OK);
 128 }
 129
 130 /*******************************************************************************
 131  *
 132  * FUNCTION:    acpi_ds_result_push
 133  *
 134  * PARAMETERS:  Object              - Where to return the popped object
 135  *              walk_state          - Current Walk state
 136  *
 137  * RETURN:      Status
 138  *
 139  * DESCRIPTION: Push an object onto the current result stack
 140  *
 141  ******************************************************************************/
 142
 143 acpi_status
 144 acpi_ds_result_push(union acpi_operand_object * object,
 145                     struct acpi_walk_state * walk_state)
 146 {
 147         union acpi_generic_state *state;
 148         acpi_status status;
 149         u32 index;
 150
 151         ACPI_FUNCTION_NAME(ds_result_push);
 152
 153         if (walk_state->result_count > walk_state->result_size) {
 154                 ACPI_ERROR((AE_INFO, "Result stack is full"));
 155                 return (AE_AML_INTERNAL);
 156         } else if (walk_state->result_count == walk_state->result_size) {
 157
 158                 /* Extend the result stack */
 159
 160                 status = acpi_ds_result_stack_push(walk_state);
 161                 if (ACPI_FAILURE(status)) {
 162                         ACPI_ERROR((AE_INFO,
 163                                     "Failed to extend the result stack"));
 164                         return (status);
 165                 }
 166         }
 167
 168         if (!(walk_state->result_count < walk_state->result_size)) {
 169                 ACPI_ERROR((AE_INFO, "No free elements in result stack"));
 170                 return (AE_AML_INTERNAL);
 171         }
 172
 173         state = walk_state->results;
 174         if (!state) {
 175                 ACPI_ERROR((AE_INFO, "No result stack frame during push"));
 176                 return (AE_AML_INTERNAL);
 177         }
 178
 179         if (!object) {
 180                 ACPI_ERROR((AE_INFO,
 181                             "Null Object! Obj=%p State=%p Num=%X",
 182                             object, walk_state, walk_state->result_count));
 183                 return (AE_BAD_PARAMETER);
 184         }
 185
 186         /* Assign the address of object to the top free element of result stack */
 187
 188         index = walk_state->result_count % ACPI_RESULTS_FRAME_OBJ_NUM;
 189         state->results.obj_desc[index] = object;
 190         walk_state->result_count++;
 191
 192         ACPI_DEBUG_PRINT((ACPI_DB_EXEC, "Obj=%p [%s] State=%p Num=%X Cur=%X\n",
 193                           object,
 194                           acpi_ut_get_object_type_name((union
 195                                                         acpi_operand_object *)
 196                                                        object), walk_state,
 197                           walk_state->result_count,
 198                           walk_state->current_result));
 199
 200         return (AE_OK);
 201 }
 202
 203 /*******************************************************************************
 204  *
 205  * FUNCTION:    acpi_ds_result_stack_push
 206  *
 207  * PARAMETERS:  walk_state          - Current Walk state
 208  *
 209  * RETURN:      Status
 210  *
 211  * DESCRIPTION: Push an object onto the walk_state result stack
 212  *
 213  ******************************************************************************/
 214
 215 static acpi_status acpi_ds_result_stack_push(struct acpi_walk_state *walk_state)
 216 {
 217         union acpi_generic_state *state;
 218
 219         ACPI_FUNCTION_NAME(ds_result_stack_push);
 220
 221         /* Check for stack overflow */
 222
 223         if (((u32) walk_state->result_size + ACPI_RESULTS_FRAME_OBJ_NUM) >
 224             ACPI_RESULTS_OBJ_NUM_MAX) {
 225                 ACPI_ERROR((AE_INFO, "Result stack overflow: State=%p Num=%X",
 226                             walk_state, walk_state->result_size));
 227                 return (AE_STACK_OVERFLOW);
 228         }
 229
 230         state = acpi_ut_create_generic_state();
 231         if (!state) {
 232                 return (AE_NO_MEMORY);
 233         }
 234
 235         state->common.descriptor_type = ACPI_DESC_TYPE_STATE_RESULT;
 236         acpi_ut_push_generic_state(&walk_state->results, state);
 237
 238         /* Increase the length of the result stack by the length of frame */
 239
 240         walk_state->result_size += ACPI_RESULTS_FRAME_OBJ_NUM;
 241
 242         ACPI_DEBUG_PRINT((ACPI_DB_EXEC, "Results=%p State=%p\n",
 243                           state, walk_state));
 244
 245         return (AE_OK);
 246 }
 247
 248 /*******************************************************************************
 249  *
 250  * FUNCTION:    acpi_ds_result_stack_pop
 251  *
 252  * PARAMETERS:  walk_state          - Current Walk state
 253  *
 254  * RETURN:      Status
 255  *
 256  * DESCRIPTION: Pop an object off of the walk_state result stack
 257  *
 258  ******************************************************************************/
 259
 260 static acpi_status acpi_ds_result_stack_pop(struct acpi_walk_state *walk_state)
 261 {
 262         union acpi_generic_state *state;
 263
 264         ACPI_FUNCTION_NAME(ds_result_stack_pop);
 265
 266         /* Check for stack underflow */
 267
 268         if (walk_state->results == NULL) {
 269                 ACPI_DEBUG_PRINT((ACPI_DB_EXEC,
 270                                   "Result stack underflow - State=%p\n",
 271                                   walk_state));
 272                 return (AE_AML_NO_OPERAND);
 273         }
 274
 275         if (walk_state->result_size < ACPI_RESULTS_FRAME_OBJ_NUM) {
 276                 ACPI_ERROR((AE_INFO, "Insufficient result stack size"));
 277                 return (AE_AML_INTERNAL);
 278         }
 279
 280         state = acpi_ut_pop_generic_state(&walk_state->results);
 281         acpi_ut_delete_generic_state(state);
 282
 283         /* Decrease the length of result stack by the length of frame */
 284
 285         walk_state->result_size -= ACPI_RESULTS_FRAME_OBJ_NUM;
 286
 287         ACPI_DEBUG_PRINT((ACPI_DB_EXEC,
 288                           "Result=%p RemainingResults=%X State=%p\n",
 289                           state, walk_state->result_count, walk_state));
 290
 291         return (AE_OK);
 292 }
 293
 294 /*******************************************************************************
 295  *
 296  * FUNCTION:    acpi_ds_obj_stack_push
 297  *
 298  * PARAMETERS:  Object              - Object to push
 299  *              walk_state          - Current Walk state
 300  *
 301  * RETURN:      Status
 302  *
 303  * DESCRIPTION: Push an object onto this walk's object/operand stack
 304  *
 305  ******************************************************************************/
 306
 307 acpi_status
 308 acpi_ds_obj_stack_push(void *object, struct acpi_walk_state * walk_state)
 309 {
 310         ACPI_FUNCTION_NAME(ds_obj_stack_push);
 311
 312         /* Check for stack overflow */
 313
 314         if (walk_state->num_operands >= ACPI_OBJ_NUM_OPERANDS) {
 315                 ACPI_ERROR((AE_INFO,
 316                             "Object stack overflow! Obj=%p State=%p #Ops=%X",
 317                             object, walk_state, walk_state->num_operands));
 318                 return (AE_STACK_OVERFLOW);
 319         }
 320
 321         /* Put the object onto the stack */
 322
 323         walk_state->operands[walk_state->operand_index] = object;
 324         walk_state->num_operands++;
 325
 326         /* For the usual order of filling the operand stack */
 327
 328         walk_state->operand_index++;
 329
 330         ACPI_DEBUG_PRINT((ACPI_DB_EXEC, "Obj=%p [%s] State=%p #Ops=%X\n",
 331                           object,
 332                           acpi_ut_get_object_type_name((union
 333                                                         acpi_operand_object *)
 334                                                        object), walk_state,
 335                           walk_state->num_operands));
 336
 337         return (AE_OK);
 338 }
 339
 340 /*******************************************************************************
 341  *
 342  * FUNCTION:    acpi_ds_obj_stack_pop
 343  *
 344  * PARAMETERS:  pop_count           - Number of objects/entries to pop
 345  *              walk_state          - Current Walk state
 346  *
 347  * RETURN:      Status
 348  *
 349  * DESCRIPTION: Pop this walk's object stack.  Objects on the stack are NOT
 350  *              deleted by this routine.
 351  *
 352  ******************************************************************************/
 353
 354 acpi_status
 355 acpi_ds_obj_stack_pop(u32 pop_count, struct acpi_walk_state * walk_state)
 356 {
 357         u32 i;
 358
 359         ACPI_FUNCTION_NAME(ds_obj_stack_pop);
 360
 361         for (i = 0; i < pop_count; i++) {
 362
 363                 /* Check for stack underflow */
 364
 365                 if (walk_state->num_operands == 0) {
 366                         ACPI_ERROR((AE_INFO,
 367                                     "Object stack underflow! Count=%X State=%p #Ops=%X",
 368                                     pop_count, walk_state,
 369                                     walk_state->num_operands));
 370                         return (AE_STACK_UNDERFLOW);
 371                 }
 372
 373                 /* Just set the stack entry to null */
 374
 375                 walk_state->num_operands--;
 376                 walk_state->operands[walk_state->num_operands] = NULL;
 377         }
 378
 379         ACPI_DEBUG_PRINT((ACPI_DB_EXEC, "Count=%X State=%p #Ops=%X\n",
 380                           pop_count, walk_state, walk_state->num_operands));
 381
 382         return (AE_OK);
 383 }
 384
 385 /*******************************************************************************
 386  *
 387  * FUNCTION:    acpi_ds_obj_stack_pop_and_delete
 388  *
 389  * PARAMETERS:  pop_count           - Number of objects/entries to pop
 390  *              walk_state          - Current Walk state
 391  *
 392  * RETURN:      Status
 393  *
 394  * DESCRIPTION: Pop this walk's object stack and delete each object that is
 395  *              popped off.
 396  *
 397  ******************************************************************************/
 398
 399 void
 400 acpi_ds_obj_stack_pop_and_delete(u32 pop_count,
 401                                  struct acpi_walk_state *walk_state)
 402 {
 403         s32 i;
 404         union acpi_operand_object *obj_desc;
 405
 406         ACPI_FUNCTION_NAME(ds_obj_stack_pop_and_delete);
 407
 408         if (pop_count == 0) {
 409                 return;
 410         }
 411
 412         for (i = (s32) pop_count - 1; i >= 0; i--) {
 413                 if (walk_state->num_operands == 0) {
 414                         return;
 415                 }
 416
 417                 /* Pop the stack and delete an object if present in this stack entry */
 418
 419                 walk_state->num_operands--;
 420                 obj_desc = walk_state->operands[i];
 421                 if (obj_desc) {
 422                         acpi_ut_remove_reference(walk_state->operands[i]);
 423                         walk_state->operands[i] = NULL;
 424                 }
 425         }
 426
 427         ACPI_DEBUG_PRINT((ACPI_DB_EXEC, "Count=%X State=%p #Ops=%X\n",
 428                           pop_count, walk_state, walk_state->num_operands));
 429 }
 430
 431 /*******************************************************************************
 432  *
 433  * FUNCTION:    acpi_ds_get_current_walk_state
 434  *
 435  * PARAMETERS:  Thread          - Get current active state for this Thread
 436  *
 437  * RETURN:      Pointer to the current walk state
 438  *
 439  * DESCRIPTION: Get the walk state that is at the head of the list (the "current"
 440  *              walk state.)
 441  *
 442  ******************************************************************************/
 443
 444 struct acpi_walk_state *acpi_ds_get_current_walk_state(struct acpi_thread_state
 445                                                        *thread)
 446 {
 447         ACPI_FUNCTION_NAME(ds_get_current_walk_state);
 448
 449         if (!thread) {
 450                 return (NULL);
 451         }
 452
 453         ACPI_DEBUG_PRINT((ACPI_DB_PARSE, "Current WalkState %p\n",
 454                           thread->walk_state_list));
 455
 456         return (thread->walk_state_list);
 457 }
 458
 459 /*******************************************************************************
 460  *
 461  * FUNCTION:    acpi_ds_push_walk_state
 462  *
 463  * PARAMETERS:  walk_state      - State to push
 464  *              Thread          - Thread state object
 465  *
 466  * RETURN:      None
 467  *
 468  * DESCRIPTION: Place the Thread state at the head of the state list
 469  *
 470  ******************************************************************************/
 471
 472 void
 473 acpi_ds_push_walk_state(struct acpi_walk_state *walk_state,
 474                         struct acpi_thread_state *thread)
 475 {
 476         ACPI_FUNCTION_TRACE(ds_push_walk_state);
 477
 478         walk_state->next = thread->walk_state_list;
 479         thread->walk_state_list = walk_state;
 480
 481         return_VOID;
 482 }
 483
 484 /*******************************************************************************
 485  *
 486  * FUNCTION:    acpi_ds_pop_walk_state
 487  *
 488  * PARAMETERS:  Thread      - Current thread state
 489  *
 490  * RETURN:      A walk_state object popped from the thread's stack
 491  *
 492  * DESCRIPTION: Remove and return the walkstate object that is at the head of
 493  *              the walk stack for the given walk list.  NULL indicates that
 494  *              the list is empty.
 495  *
 496  ******************************************************************************/
 497
 498 struct acpi_walk_state *acpi_ds_pop_walk_state(struct acpi_thread_state *thread)
 499 {
 500         struct acpi_walk_state *walk_state;
 501
 502         ACPI_FUNCTION_TRACE(ds_pop_walk_state);
 503
 504         walk_state = thread->walk_state_list;
 505
 506         if (walk_state) {
 507
 508                 /* Next walk state becomes the current walk state */
 509
 510                 thread->walk_state_list = walk_state->next;
 511
 512                 /*
 513                  * Don't clear the NEXT field, this serves as an indicator
 514                  * that there is a parent WALK STATE
 515                  * Do Not: walk_state->Next = NULL;
 516                  */
 517         }
 518
 519         return_PTR(walk_state);
 520 }
 521
 522 /*******************************************************************************
 523  *
 524  * FUNCTION:    acpi_ds_create_walk_state
 525  *
 526  * PARAMETERS:  owner_id        - ID for object creation
 527  *              Origin          - Starting point for this walk
 528  *              method_desc     - Method object
 529  *              Thread          - Current thread state
 530  *
 531  * RETURN:      Pointer to the new walk state.
 532  *
 533  * DESCRIPTION: Allocate and initialize a new walk state.  The current walk
 534  *              state is set to this new state.
 535  *
 536  ******************************************************************************/
 537
 538 struct acpi_walk_state *acpi_ds_create_walk_state(acpi_owner_id owner_id, union acpi_parse_object
 539                                                   *origin, union acpi_operand_object
 540                                                   *method_desc, struct acpi_thread_state
 541                                                   *thread)
 542 {
 543         struct acpi_walk_state *walk_state;
 544
 545         ACPI_FUNCTION_TRACE(ds_create_walk_state);
 546
 547         walk_state = ACPI_ALLOCATE_ZEROED(sizeof(struct acpi_walk_state));
 548         if (!walk_state) {
 549                 return_PTR(NULL);
 550         }
 551
 552         walk_state->descriptor_type = ACPI_DESC_TYPE_WALK;
 553         walk_state->method_desc = method_desc;
 554         walk_state->owner_id = owner_id;
 555         walk_state->origin = origin;
 556         walk_state->thread = thread;
 557
 558         walk_state->parser_state.start_op = origin;
 559
 560         /* Init the method args/local */
 561
 562 #if (!defined (ACPI_NO_METHOD_EXECUTION) && !defined (ACPI_CONSTANT_EVAL_ONLY))
 563         acpi_ds_method_data_init(walk_state);
 564 #endif
 565
 566         /* Put the new state at the head of the walk list */
 567
 568         if (thread) {
 569                 acpi_ds_push_walk_state(walk_state, thread);
 570         }
 571
 572         return_PTR(walk_state);
 573 }
 574
 575 /*******************************************************************************
 576  *
 577  * FUNCTION:    acpi_ds_init_aml_walk
 578  *
 579  * PARAMETERS:  walk_state      - New state to be initialized
 580  *              Op              - Current parse op
 581  *              method_node     - Control method NS node, if any
 582  *              aml_start       - Start of AML
 583  *              aml_length      - Length of AML
 584  *              Info            - Method info block (params, etc.)
 585  *              pass_number     - 1, 2, or 3
 586  *
 587  * RETURN:      Status
 588  *
 589  * DESCRIPTION: Initialize a walk state for a pass 1 or 2 parse tree walk
 590  *
 591  ******************************************************************************/
 592
 593 acpi_status
 594 acpi_ds_init_aml_walk(struct acpi_walk_state *walk_state,
 595                       union acpi_parse_object *op,
 596                       struct acpi_namespace_node *method_node,
 597                       u8 * aml_start,
 598                       u32 aml_length,
 599                       struct acpi_evaluate_info *info, u8 pass_number)
 600 {
 601         acpi_status status;
 602         struct acpi_parse_state *parser_state = &walk_state->parser_state;
 603         union acpi_parse_object *extra_op;
 604
 605         ACPI_FUNCTION_TRACE(ds_init_aml_walk);
 606
 607         walk_state->parser_state.aml =
 608             walk_state->parser_state.aml_start = aml_start;
 609         walk_state->parser_state.aml_end =
 610             walk_state->parser_state.pkg_end = aml_start + aml_length;
 611
 612         /* The next_op of the next_walk will be the beginning of the method */
 613
 614         walk_state->next_op = NULL;
 615         walk_state->pass_number = pass_number;
 616
 617         if (info) {
 618                 walk_state->params = info->parameters;
 619                 walk_state->caller_return_desc = &info->return_object;
 620         }
 621
 622         status = acpi_ps_init_scope(&walk_state->parser_state, op);
 623         if (ACPI_FAILURE(status)) {
 624                 return_ACPI_STATUS(status);
 625         }
 626
 627         if (method_node) {
 628                 walk_state->parser_state.start_node = method_node;
 629                 walk_state->walk_type = ACPI_WALK_METHOD;
 630                 walk_state->method_node = method_node;
 631                 walk_state->method_desc =
 632                     acpi_ns_get_attached_object(method_node);
 633
 634                 /* Push start scope on scope stack and make it current  */
 635
 636                 status =
 637                     acpi_ds_scope_stack_push(method_node, ACPI_TYPE_METHOD,
 638                                              walk_state);
 639                 if (ACPI_FAILURE(status)) {
 640                         return_ACPI_STATUS(status);
 641                 }
 642
 643                 /* Init the method arguments */
 644
 645                 status = acpi_ds_method_data_init_args(walk_state->params,
 646                                                        ACPI_METHOD_NUM_ARGS,
 647                                                        walk_state);
 648                 if (ACPI_FAILURE(status)) {
 649                         return_ACPI_STATUS(status);
 650                 }
 651         } else {
 652                 /*
 653                  * Setup the current scope.
 654                  * Find a Named Op that has a namespace node associated with it.
 655                  * search upwards from this Op.  Current scope is the first
 656                  * Op with a namespace node.
 657                  */
 658                 extra_op = parser_state->start_op;
 659                 while (extra_op && !extra_op->common.node) {
 660                         extra_op = extra_op->common.parent;
 661                 }
 662
 663                 if (!extra_op) {
 664                         parser_state->start_node = NULL;
 665                 } else {
 666                         parser_state->start_node = extra_op->common.node;
 667                 }
 668
 669                 if (parser_state->start_node) {
 670
 671                         /* Push start scope on scope stack and make it current  */
 672
 673                         status =
 674                             acpi_ds_scope_stack_push(parser_state->start_node,
 675                                                      parser_state->start_node->
 676                                                      type, walk_state);
 677                         if (ACPI_FAILURE(status)) {
 678                                 return_ACPI_STATUS(status);
 679                         }
 680                 }
 681         }
 682
 683         status = acpi_ds_init_callbacks(walk_state, pass_number);
 684         return_ACPI_STATUS(status);
 685 }
 686
 687 /*******************************************************************************
 688  *
 689  * FUNCTION:    acpi_ds_delete_walk_state
 690  *
 691  * PARAMETERS:  walk_state      - State to delete
 692  *
 693  * RETURN:      Status
 694  *
 695  * DESCRIPTION: Delete a walk state including all internal data structures
 696  *
 697  ******************************************************************************/
 698
 699 void acpi_ds_delete_walk_state(struct acpi_walk_state *walk_state)
 700 {
 701         union acpi_generic_state *state;
 702
 703         ACPI_FUNCTION_TRACE_PTR(ds_delete_walk_state, walk_state);
 704
 705         if (!walk_state) {
 706                 return;
 707         }
 708
 709         if (walk_state->descriptor_type != ACPI_DESC_TYPE_WALK) {
 710                 ACPI_ERROR((AE_INFO, "%p is not a valid walk state",
 711                             walk_state));
 712                 return;
 713         }
 714
 715         /* There should not be any open scopes */
 716
 717         if (walk_state->parser_state.scope) {
 718                 ACPI_ERROR((AE_INFO, "%p walk still has a scope list",
 719                             walk_state));
 720                 acpi_ps_cleanup_scope(&walk_state->parser_state);
 721         }
 722
 723         /* Always must free any linked control states */
 724
 725         while (walk_state->control_state) {
 726                 state = walk_state->control_state;
 727                 walk_state->control_state = state->common.next;
 728
 729                 acpi_ut_delete_generic_state(state);
 730         }
 731
 732         /* Always must free any linked parse states */
 733
 734         while (walk_state->scope_info) {
 735                 state = walk_state->scope_info;
 736                 walk_state->scope_info = state->common.next;
 737
 738                 acpi_ut_delete_generic_state(state);
 739         }
 740
 741         /* Always must free any stacked result states */
 742
 743         while (walk_state->results) {
 744                 state = walk_state->results;
 745                 walk_state->results = state->common.next;
 746
 747                 acpi_ut_delete_generic_state(state);
 748         }
 749
 750         ACPI_FREE(walk_state);
 751         return_VOID;
 752 }