drivers/acpi/namespace/nsaccess.c

   1 /*******************************************************************************
   2  *
   3  * Module Name: nsaccess - Top-level functions for accessing ACPI namespace
   4  *
   5  ******************************************************************************/
   6
   7 /*
   8  * Copyright (C) 2000 - 2006, R. Byron Moore
   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/amlcode.h>
  46 #include <acpi/acnamesp.h>
  47 #include <acpi/acdispat.h>
  48
  49 #define _COMPONENT          ACPI_NAMESPACE
  50 ACPI_MODULE_NAME("nsaccess")
  51
  52 /*******************************************************************************
  53  *
  54  * FUNCTION:    acpi_ns_root_initialize
  55  *
  56  * PARAMETERS:  None
  57  *
  58  * RETURN:      Status
  59  *
  60  * DESCRIPTION: Allocate and initialize the default root named objects
  61  *
  62  * MUTEX:       Locks namespace for entire execution
  63  *
  64  ******************************************************************************/
  65 acpi_status acpi_ns_root_initialize(void)
  66 {
  67         acpi_status status;
  68         const struct acpi_predefined_names *init_val = NULL;
  69         struct acpi_namespace_node *new_node;
  70         union acpi_operand_object *obj_desc;
  71         acpi_string val = NULL;
  72
  73         ACPI_FUNCTION_TRACE("ns_root_initialize");
  74
  75         status = acpi_ut_acquire_mutex(ACPI_MTX_NAMESPACE);
  76         if (ACPI_FAILURE(status)) {
  77                 return_ACPI_STATUS(status);
  78         }
  79
  80         /*
  81          * The global root ptr is initially NULL, so a non-NULL value indicates
  82          * that acpi_ns_root_initialize() has already been called; just return.
  83          */
  84         if (acpi_gbl_root_node) {
  85                 status = AE_OK;
  86                 goto unlock_and_exit;
  87         }
  88
  89         /*
  90          * Tell the rest of the subsystem that the root is initialized
  91          * (This is OK because the namespace is locked)
  92          */
  93         acpi_gbl_root_node = &acpi_gbl_root_node_struct;
  94
  95         /* Enter the pre-defined names in the name table */
  96
  97         ACPI_DEBUG_PRINT((ACPI_DB_INFO,
  98                           "Entering predefined entries into namespace\n"));
  99
 100         for (init_val = acpi_gbl_pre_defined_names; init_val->name; init_val++) {
 101                 /* _OSI is optional for now, will be permanent later */
 102
 103                 if (!ACPI_STRCMP(init_val->name, "_OSI")
 104                     && !acpi_gbl_create_osi_method) {
 105                         continue;
 106                 }
 107
 108                 status = acpi_ns_lookup(NULL, init_val->name, init_val->type,
 109                                         ACPI_IMODE_LOAD_PASS2,
 110                                         ACPI_NS_NO_UPSEARCH, NULL, &new_node);
 111
 112                 if (ACPI_FAILURE(status) || (!new_node)) {      /* Must be on same line for code converter */
 113                         ACPI_EXCEPTION((AE_INFO, status,
 114                                         "Could not create predefined name %s",
 115                                         init_val->name));
 116                 }
 117
 118                 /*
 119                  * Name entered successfully.
 120                  * If entry in pre_defined_names[] specifies an
 121                  * initial value, create the initial value.
 122                  */
 123                 if (init_val->val) {
 124                         status = acpi_os_predefined_override(init_val, &val);
 125                         if (ACPI_FAILURE(status)) {
 126                                 ACPI_ERROR((AE_INFO,
 127                                             "Could not override predefined %s",
 128                                             init_val->name));
 129                         }
 130
 131                         if (!val) {
 132                                 val = init_val->val;
 133                         }
 134
 135                         /*
 136                          * Entry requests an initial value, allocate a
 137                          * descriptor for it.
 138                          */
 139                         obj_desc =
 140                             acpi_ut_create_internal_object(init_val->type);
 141                         if (!obj_desc) {
 142                                 status = AE_NO_MEMORY;
 143                                 goto unlock_and_exit;
 144                         }
 145
 146                         /*
 147                          * Convert value string from table entry to
 148                          * internal representation. Only types actually
 149                          * used for initial values are implemented here.
 150                          */
 151                         switch (init_val->type) {
 152                         case ACPI_TYPE_METHOD:
 153                                 obj_desc->method.param_count =
 154                                     (u8) ACPI_TO_INTEGER(val);
 155                                 obj_desc->common.flags |= AOPOBJ_DATA_VALID;
 156
 157 #if defined (ACPI_ASL_COMPILER)
 158
 159                                 /* save the parameter count for the i_aSL compiler */
 160
 161                                 new_node->value = obj_desc->method.param_count;
 162 #else
 163                                 /* Mark this as a very SPECIAL method */
 164
 165                                 obj_desc->method.method_flags =
 166                                     AML_METHOD_INTERNAL_ONLY;
 167
 168 #ifndef ACPI_DUMP_APP
 169                                 obj_desc->method.implementation =
 170                                     acpi_ut_osi_implementation;
 171 #endif
 172 #endif
 173                                 break;
 174
 175                         case ACPI_TYPE_INTEGER:
 176
 177                                 obj_desc->integer.value = ACPI_TO_INTEGER(val);
 178                                 break;
 179
 180                         case ACPI_TYPE_STRING:
 181
 182                                 /*
 183                                  * Build an object around the static string
 184                                  */
 185                                 obj_desc->string.length =
 186                                     (u32) ACPI_STRLEN(val);
 187                                 obj_desc->string.pointer = val;
 188                                 obj_desc->common.flags |= AOPOBJ_STATIC_POINTER;
 189                                 break;
 190
 191                         case ACPI_TYPE_MUTEX:
 192
 193                                 obj_desc->mutex.node = new_node;
 194                                 obj_desc->mutex.sync_level =
 195                                     (u8) (ACPI_TO_INTEGER(val) - 1);
 196
 197                                 if (ACPI_STRCMP(init_val->name, "_GL_") == 0) {
 198                                         /*
 199                                          * Create a counting semaphore for the
 200                                          * global lock
 201                                          */
 202                                         status =
 203                                             acpi_os_create_semaphore
 204                                             (ACPI_NO_UNIT_LIMIT, 1,
 205                                              &obj_desc->mutex.semaphore);
 206                                         if (ACPI_FAILURE(status)) {
 207                                                 acpi_ut_remove_reference
 208                                                     (obj_desc);
 209                                                 goto unlock_and_exit;
 210                                         }
 211
 212                                         /*
 213                                          * We just created the mutex for the
 214                                          * global lock, save it
 215                                          */
 216                                         acpi_gbl_global_lock_semaphore =
 217                                             obj_desc->mutex.semaphore;
 218                                 } else {
 219                                         /* Create a mutex */
 220
 221                                         status = acpi_os_create_semaphore(1, 1,
 222                                                                           &obj_desc->
 223                                                                           mutex.
 224                                                                           semaphore);
 225                                         if (ACPI_FAILURE(status)) {
 226                                                 acpi_ut_remove_reference
 227                                                     (obj_desc);
 228                                                 goto unlock_and_exit;
 229                                         }
 230                                 }
 231                                 break;
 232
 233                         default:
 234
 235                                 ACPI_ERROR((AE_INFO,
 236                                             "Unsupported initial type value %X",
 237                                             init_val->type));
 238                                 acpi_ut_remove_reference(obj_desc);
 239                                 obj_desc = NULL;
 240                                 continue;
 241                         }
 242
 243                         /* Store pointer to value descriptor in the Node */
 244
 245                         status = acpi_ns_attach_object(new_node, obj_desc,
 246                                                        ACPI_GET_OBJECT_TYPE
 247                                                        (obj_desc));
 248
 249                         /* Remove local reference to the object */
 250
 251                         acpi_ut_remove_reference(obj_desc);
 252                 }
 253         }
 254
 255       unlock_and_exit:
 256         (void)acpi_ut_release_mutex(ACPI_MTX_NAMESPACE);
 257
 258         /* Save a handle to "_GPE", it is always present */
 259
 260         if (ACPI_SUCCESS(status)) {
 261                 status =
 262                     acpi_ns_get_node_by_path("\\_GPE", NULL,
 263                                              ACPI_NS_NO_UPSEARCH,
 264                                              &acpi_gbl_fadt_gpe_device);
 265         }
 266
 267         return_ACPI_STATUS(status);
 268 }
 269
 270 /*******************************************************************************
 271  *
 272  * FUNCTION:    acpi_ns_lookup
 273  *
 274  * PARAMETERS:  scope_info      - Current scope info block
 275  *              Pathname        - Search pathname, in internal format
 276  *                                (as represented in the AML stream)
 277  *              Type            - Type associated with name
 278  *              interpreter_mode - IMODE_LOAD_PASS2 => add name if not found
 279  *              Flags           - Flags describing the search restrictions
 280  *              walk_state      - Current state of the walk
 281  *              return_node     - Where the Node is placed (if found
 282  *                                or created successfully)
 283  *
 284  * RETURN:      Status
 285  *
 286  * DESCRIPTION: Find or enter the passed name in the name space.
 287  *              Log an error if name not found in Exec mode.
 288  *
 289  * MUTEX:       Assumes namespace is locked.
 290  *
 291  ******************************************************************************/
 292
 293 acpi_status
 294 acpi_ns_lookup(union acpi_generic_state *scope_info,
 295                char *pathname,
 296                acpi_object_type type,
 297                acpi_interpreter_mode interpreter_mode,
 298                u32 flags,
 299                struct acpi_walk_state *walk_state,
 300                struct acpi_namespace_node **return_node)
 301 {
 302         acpi_status status;
 303         char *path = pathname;
 304         struct acpi_namespace_node *prefix_node;
 305         struct acpi_namespace_node *current_node = NULL;
 306         struct acpi_namespace_node *this_node = NULL;
 307         u32 num_segments;
 308         u32 num_carats;
 309         acpi_name simple_name;
 310         acpi_object_type type_to_check_for;
 311         acpi_object_type this_search_type;
 312         u32 search_parent_flag = ACPI_NS_SEARCH_PARENT;
 313         u32 local_flags = flags & ~(ACPI_NS_ERROR_IF_FOUND |
 314                                     ACPI_NS_SEARCH_PARENT);
 315
 316         ACPI_FUNCTION_TRACE("ns_lookup");
 317
 318         if (!return_node) {
 319                 return_ACPI_STATUS(AE_BAD_PARAMETER);
 320         }
 321
 322         acpi_gbl_ns_lookup_count++;
 323         *return_node = ACPI_ENTRY_NOT_FOUND;
 324
 325         if (!acpi_gbl_root_node) {
 326                 return_ACPI_STATUS(AE_NO_NAMESPACE);
 327         }
 328
 329         /*
 330          * Get the prefix scope.
 331          * A null scope means use the root scope
 332          */
 333         if ((!scope_info) || (!scope_info->scope.node)) {
 334                 ACPI_DEBUG_PRINT((ACPI_DB_NAMES,
 335                                   "Null scope prefix, using root node (%p)\n",
 336                                   acpi_gbl_root_node));
 337
 338                 prefix_node = acpi_gbl_root_node;
 339         } else {
 340                 prefix_node = scope_info->scope.node;
 341                 if (ACPI_GET_DESCRIPTOR_TYPE(prefix_node) !=
 342                     ACPI_DESC_TYPE_NAMED) {
 343                         ACPI_ERROR((AE_INFO, "%p is not a namespace node [%s]",
 344                                     prefix_node,
 345                                     acpi_ut_get_descriptor_name(prefix_node)));
 346                         return_ACPI_STATUS(AE_AML_INTERNAL);
 347                 }
 348
 349                 /*
 350                  * This node might not be a actual "scope" node (such as a
 351                  * Device/Method, etc.)  It could be a Package or other object node.
 352                  * Backup up the tree to find the containing scope node.
 353                  */
 354                 while (!acpi_ns_opens_scope(prefix_node->type) &&
 355                        prefix_node->type != ACPI_TYPE_ANY) {
 356                         prefix_node = acpi_ns_get_parent_node(prefix_node);
 357                 }
 358         }
 359
 360         /* Save type   TBD: may be no longer necessary */
 361
 362         type_to_check_for = type;
 363
 364         /*
 365          * Begin examination of the actual pathname
 366          */
 367         if (!pathname) {
 368                 /* A Null name_path is allowed and refers to the root */
 369
 370                 num_segments = 0;
 371                 this_node = acpi_gbl_root_node;
 372                 path = "";
 373
 374                 ACPI_DEBUG_PRINT((ACPI_DB_NAMES,
 375                                   "Null Pathname (Zero segments), Flags=%X\n",
 376                                   flags));
 377         } else {
 378                 /*
 379                  * Name pointer is valid (and must be in internal name format)
 380                  *
 381                  * Check for scope prefixes:
 382                  *
 383                  * As represented in the AML stream, a namepath consists of an
 384                  * optional scope prefix followed by a name segment part.
 385                  *
 386                  * If present, the scope prefix is either a Root Prefix (in
 387                  * which case the name is fully qualified), or one or more
 388                  * Parent Prefixes (in which case the name's scope is relative
 389                  * to the current scope).
 390                  */
 391                 if (*path == (u8) AML_ROOT_PREFIX) {
 392                         /* Pathname is fully qualified, start from the root */
 393
 394                         this_node = acpi_gbl_root_node;
 395                         search_parent_flag = ACPI_NS_NO_UPSEARCH;
 396
 397                         /* Point to name segment part */
 398
 399                         path++;
 400
 401                         ACPI_DEBUG_PRINT((ACPI_DB_NAMES,
 402                                           "Path is absolute from root [%p]\n",
 403                                           this_node));
 404                 } else {
 405                         /* Pathname is relative to current scope, start there */
 406
 407                         ACPI_DEBUG_PRINT((ACPI_DB_NAMES,
 408                                           "Searching relative to prefix scope [%4.4s] (%p)\n",
 409                                           acpi_ut_get_node_name(prefix_node),
 410                                           prefix_node));
 411
 412                         /*
 413                          * Handle multiple Parent Prefixes (carat) by just getting
 414                          * the parent node for each prefix instance.
 415                          */
 416                         this_node = prefix_node;
 417                         num_carats = 0;
 418                         while (*path == (u8) AML_PARENT_PREFIX) {
 419                                 /* Name is fully qualified, no search rules apply */
 420
 421                                 search_parent_flag = ACPI_NS_NO_UPSEARCH;
 422                                 /*
 423                                  * Point past this prefix to the name segment
 424                                  * part or the next Parent Prefix
 425                                  */
 426                                 path++;
 427
 428                                 /* Backup to the parent node */
 429
 430                                 num_carats++;
 431                                 this_node = acpi_ns_get_parent_node(this_node);
 432                                 if (!this_node) {
 433                                         /* Current scope has no parent scope */
 434
 435                                         ACPI_ERROR((AE_INFO,
 436                                                     "ACPI path has too many parent prefixes (^) - reached beyond root node"));
 437                                         return_ACPI_STATUS(AE_NOT_FOUND);
 438                                 }
 439                         }
 440
 441                         if (search_parent_flag == ACPI_NS_NO_UPSEARCH) {
 442                                 ACPI_DEBUG_PRINT((ACPI_DB_NAMES,
 443                                                   "Search scope is [%4.4s], path has %d carat(s)\n",
 444                                                   acpi_ut_get_node_name
 445                                                   (this_node), num_carats));
 446                         }
 447                 }
 448
 449                 /*
 450                  * Determine the number of ACPI name segments in this pathname.
 451                  *
 452                  * The segment part consists of either:
 453                  *  - A Null name segment (0)
 454                  *  - A dual_name_prefix followed by two 4-byte name segments
 455                  *  - A multi_name_prefix followed by a byte indicating the
 456                  *      number of segments and the segments themselves.
 457                  *  - A single 4-byte name segment
 458                  *
 459                  * Examine the name prefix opcode, if any, to determine the number of
 460                  * segments.
 461                  */
 462                 switch (*path) {
 463                 case 0:
 464                         /*
 465                          * Null name after a root or parent prefixes. We already
 466                          * have the correct target node and there are no name segments.
 467                          */
 468                         num_segments = 0;
 469                         type = this_node->type;
 470
 471                         ACPI_DEBUG_PRINT((ACPI_DB_NAMES,
 472                                           "Prefix-only Pathname (Zero name segments), Flags=%X\n",
 473                                           flags));
 474                         break;
 475
 476                 case AML_DUAL_NAME_PREFIX:
 477
 478                         /* More than one name_seg, search rules do not apply */
 479
 480                         search_parent_flag = ACPI_NS_NO_UPSEARCH;
 481
 482                         /* Two segments, point to first name segment */
 483
 484                         num_segments = 2;
 485                         path++;
 486
 487                         ACPI_DEBUG_PRINT((ACPI_DB_NAMES,
 488                                           "Dual Pathname (2 segments, Flags=%X)\n",
 489                                           flags));
 490                         break;
 491
 492                 case AML_MULTI_NAME_PREFIX_OP:
 493
 494                         /* More than one name_seg, search rules do not apply */
 495
 496                         search_parent_flag = ACPI_NS_NO_UPSEARCH;
 497
 498                         /* Extract segment count, point to first name segment */
 499
 500                         path++;
 501                         num_segments = (u32) (u8) * path;
 502                         path++;
 503
 504                         ACPI_DEBUG_PRINT((ACPI_DB_NAMES,
 505                                           "Multi Pathname (%d Segments, Flags=%X)\n",
 506                                           num_segments, flags));
 507                         break;
 508
 509                 default:
 510                         /*
 511                          * Not a Null name, no Dual or Multi prefix, hence there is
 512                          * only one name segment and Pathname is already pointing to it.
 513                          */
 514                         num_segments = 1;
 515
 516                         ACPI_DEBUG_PRINT((ACPI_DB_NAMES,
 517                                           "Simple Pathname (1 segment, Flags=%X)\n",
 518                                           flags));
 519                         break;
 520                 }
 521
 522                 ACPI_DEBUG_EXEC(acpi_ns_print_pathname(num_segments, path));
 523         }
 524
 525         /*
 526          * Search namespace for each segment of the name.  Loop through and
 527          * verify (or add to the namespace) each name segment.
 528          *
 529          * The object type is significant only at the last name
 530          * segment.  (We don't care about the types along the path, only
 531          * the type of the final target object.)
 532          */
 533         this_search_type = ACPI_TYPE_ANY;
 534         current_node = this_node;
 535         while (num_segments && current_node) {
 536                 num_segments--;
 537                 if (!num_segments) {
 538                         /*
 539                          * This is the last segment, enable typechecking
 540                          */
 541                         this_search_type = type;
 542
 543                         /*
 544                          * Only allow automatic parent search (search rules) if the caller
 545                          * requested it AND we have a single, non-fully-qualified name_seg
 546                          */
 547                         if ((search_parent_flag != ACPI_NS_NO_UPSEARCH) &&
 548                             (flags & ACPI_NS_SEARCH_PARENT)) {
 549                                 local_flags |= ACPI_NS_SEARCH_PARENT;
 550                         }
 551
 552                         /* Set error flag according to caller */
 553
 554                         if (flags & ACPI_NS_ERROR_IF_FOUND) {
 555                                 local_flags |= ACPI_NS_ERROR_IF_FOUND;
 556                         }
 557                 }
 558
 559                 /* Extract one ACPI name from the front of the pathname */
 560
 561                 ACPI_MOVE_32_TO_32(&simple_name, path);
 562
 563                 /* Try to find the single (4 character) ACPI name */
 564
 565                 status =
 566                     acpi_ns_search_and_enter(simple_name, walk_state,
 567                                              current_node, interpreter_mode,
 568                                              this_search_type, local_flags,
 569                                              &this_node);
 570                 if (ACPI_FAILURE(status)) {
 571                         if (status == AE_NOT_FOUND) {
 572                                 /* Name not found in ACPI namespace */
 573
 574                                 ACPI_DEBUG_PRINT((ACPI_DB_NAMES,
 575                                                   "Name [%4.4s] not found in scope [%4.4s] %p\n",
 576                                                   (char *)&simple_name,
 577                                                   (char *)&current_node->name,
 578                                                   current_node));
 579                         }
 580
 581                         *return_node = this_node;
 582                         return_ACPI_STATUS(status);
 583                 }
 584
 585                 /*
 586                  * Sanity typecheck of the target object:
 587                  *
 588                  * If 1) This is the last segment (num_segments == 0)
 589                  *    2) And we are looking for a specific type
 590                  *       (Not checking for TYPE_ANY)
 591                  *    3) Which is not an alias
 592                  *    4) Which is not a local type (TYPE_SCOPE)
 593                  *    5) And the type of target object is known (not TYPE_ANY)
 594                  *    6) And target object does not match what we are looking for
 595                  *
 596                  * Then we have a type mismatch.  Just warn and ignore it.
 597                  */
 598                 if ((num_segments == 0) &&
 599                     (type_to_check_for != ACPI_TYPE_ANY) &&
 600                     (type_to_check_for != ACPI_TYPE_LOCAL_ALIAS) &&
 601                     (type_to_check_for != ACPI_TYPE_LOCAL_METHOD_ALIAS) &&
 602                     (type_to_check_for != ACPI_TYPE_LOCAL_SCOPE) &&
 603                     (this_node->type != ACPI_TYPE_ANY) &&
 604                     (this_node->type != type_to_check_for)) {
 605                         /* Complain about a type mismatch */
 606
 607                         ACPI_WARNING((AE_INFO,
 608                                       "ns_lookup: Type mismatch on %4.4s (%s), searching for (%s)",
 609                                       ACPI_CAST_PTR(char, &simple_name),
 610                                       acpi_ut_get_type_name(this_node->type),
 611                                       acpi_ut_get_type_name
 612                                       (type_to_check_for)));
 613                 }
 614
 615                 /*
 616                  * If this is the last name segment and we are not looking for a
 617                  * specific type, but the type of found object is known, use that type
 618                  * to see if it opens a scope.
 619                  */
 620                 if ((num_segments == 0) && (type == ACPI_TYPE_ANY)) {
 621                         type = this_node->type;
 622                 }
 623
 624                 /* Point to next name segment and make this node current */
 625
 626                 path += ACPI_NAME_SIZE;
 627                 current_node = this_node;
 628         }
 629
 630         /*
 631          * Always check if we need to open a new scope
 632          */
 633         if (!(flags & ACPI_NS_DONT_OPEN_SCOPE) && (walk_state)) {
 634                 /*
 635                  * If entry is a type which opens a scope, push the new scope on the
 636                  * scope stack.
 637                  */
 638                 if (acpi_ns_opens_scope(type)) {
 639                         status =
 640                             acpi_ds_scope_stack_push(this_node, type,
 641                                                      walk_state);
 642                         if (ACPI_FAILURE(status)) {
 643                                 return_ACPI_STATUS(status);
 644                         }
 645                 }
 646         }
 647
 648         *return_node = this_node;
 649         return_ACPI_STATUS(AE_OK);
 650 }