git.oblomov.eu Git - linux-2.6/blob - 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 - 2007, 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
 102                 /* _OSI is optional for now, will be permanent later */
 103
 104                 if (!ACPI_STRCMP(init_val->name, "_OSI")
 105                     && !acpi_gbl_create_osi_method) {
 106                         continue;
 107                 }
 108
 109                 status = acpi_ns_lookup(NULL, init_val->name, init_val->type,
 110                                         ACPI_IMODE_LOAD_PASS2,
 111                                         ACPI_NS_NO_UPSEARCH, NULL, &new_node);
 112
 113                 if (ACPI_FAILURE(status) || (!new_node)) {      /* Must be on same line for code converter */
 114                         ACPI_EXCEPTION((AE_INFO, status,
 115                                         "Could not create predefined name %s",
 116                                         init_val->name));
 117                 }
 118
 119                 /*
 120                  * Name entered successfully.
 121                  * If entry in pre_defined_names[] specifies an
 122                  * initial value, create the initial value.
 123                  */
 124                 if (init_val->val) {
 125                         status = acpi_os_predefined_override(init_val, &val);
 126                         if (ACPI_FAILURE(status)) {
 127                                 ACPI_ERROR((AE_INFO,
 128                                             "Could not override predefined %s",
 129                                             init_val->name));
 130                         }
 131
 132                         if (!val) {
 133                                 val = init_val->val;
 134                         }
 135
 136                         /*
 137                          * Entry requests an initial value, allocate a
 138                          * descriptor for it.
 139                          */
 140                         obj_desc =
 141                             acpi_ut_create_internal_object(init_val->type);
 142                         if (!obj_desc) {
 143                                 status = AE_NO_MEMORY;
 144                                 goto unlock_and_exit;
 145                         }
 146
 147                         /*
 148                          * Convert value string from table entry to
 149                          * internal representation. Only types actually
 150                          * used for initial values are implemented here.
 151                          */
 152                         switch (init_val->type) {
 153                         case ACPI_TYPE_METHOD:
 154                                 obj_desc->method.param_count =
 155                                     (u8) ACPI_TO_INTEGER(val);
 156                                 obj_desc->common.flags |= AOPOBJ_DATA_VALID;
 157
 158 #if defined (ACPI_ASL_COMPILER)
 159
 160                                 /* Save the parameter count for the i_aSL compiler */
 161
 162                                 new_node->value = obj_desc->method.param_count;
 163 #else
 164                                 /* Mark this as a very SPECIAL method */
 165
 166                                 obj_desc->method.method_flags =
 167                                     AML_METHOD_INTERNAL_ONLY;
 168
 169 #ifndef ACPI_DUMP_APP
 170                                 obj_desc->method.implementation =
 171                                     acpi_ut_osi_implementation;
 172 #endif
 173 #endif
 174                                 break;
 175
 176                         case ACPI_TYPE_INTEGER:
 177
 178                                 obj_desc->integer.value = ACPI_TO_INTEGER(val);
 179                                 break;
 180
 181                         case ACPI_TYPE_STRING:
 182
 183                                 /*
 184                                  * Build an object around the static string
 185                                  */
 186                                 obj_desc->string.length =
 187                                     (u32) ACPI_STRLEN(val);
 188                                 obj_desc->string.pointer = val;
 189                                 obj_desc->common.flags |= AOPOBJ_STATIC_POINTER;
 190                                 break;
 191
 192                         case ACPI_TYPE_MUTEX:
 193
 194                                 obj_desc->mutex.node = new_node;
 195                                 obj_desc->mutex.sync_level =
 196                                     (u8) (ACPI_TO_INTEGER(val) - 1);
 197
 198                                 /* Create a mutex */
 199
 200                                 status =
 201                                     acpi_os_create_mutex(&obj_desc->mutex.
 202                                                          os_mutex);
 203                                 if (ACPI_FAILURE(status)) {
 204                                         acpi_ut_remove_reference(obj_desc);
 205                                         goto unlock_and_exit;
 206                                 }
 207
 208                                 /* Special case for ACPI Global Lock */
 209
 210                                 if (ACPI_STRCMP(init_val->name, "_GL_") == 0) {
 211                                         acpi_gbl_global_lock_mutex =
 212                                             obj_desc->mutex.os_mutex;
 213
 214                                         /* Create additional counting semaphore for global lock */
 215
 216                                         status =
 217                                             acpi_os_create_semaphore(1, 0,
 218                                                                      &acpi_gbl_global_lock_semaphore);
 219                                         if (ACPI_FAILURE(status)) {
 220                                                 acpi_ut_remove_reference
 221                                                     (obj_desc);
 222                                                 goto unlock_and_exit;
 223                                         }
 224                                 }
 225                                 break;
 226
 227                         default:
 228
 229                                 ACPI_ERROR((AE_INFO,
 230                                             "Unsupported initial type value %X",
 231                                             init_val->type));
 232                                 acpi_ut_remove_reference(obj_desc);
 233                                 obj_desc = NULL;
 234                                 continue;
 235                         }
 236
 237                         /* Store pointer to value descriptor in the Node */
 238
 239                         status = acpi_ns_attach_object(new_node, obj_desc,
 240                                                        ACPI_GET_OBJECT_TYPE
 241                                                        (obj_desc));
 242
 243                         /* Remove local reference to the object */
 244
 245                         acpi_ut_remove_reference(obj_desc);
 246                 }
 247         }
 248
 249       unlock_and_exit:
 250         (void)acpi_ut_release_mutex(ACPI_MTX_NAMESPACE);
 251
 252         /* Save a handle to "_GPE", it is always present */
 253
 254         if (ACPI_SUCCESS(status)) {
 255                 status = acpi_ns_get_node(NULL, "\\_GPE", ACPI_NS_NO_UPSEARCH,
 256                                           &acpi_gbl_fadt_gpe_device);
 257         }
 258
 259         return_ACPI_STATUS(status);
 260 }
 261
 262 /*******************************************************************************
 263  *
 264  * FUNCTION:    acpi_ns_lookup
 265  *
 266  * PARAMETERS:  scope_info      - Current scope info block
 267  *              Pathname        - Search pathname, in internal format
 268  *                                (as represented in the AML stream)
 269  *              Type            - Type associated with name
 270  *              interpreter_mode - IMODE_LOAD_PASS2 => add name if not found
 271  *              Flags           - Flags describing the search restrictions
 272  *              walk_state      - Current state of the walk
 273  *              return_node     - Where the Node is placed (if found
 274  *                                or created successfully)
 275  *
 276  * RETURN:      Status
 277  *
 278  * DESCRIPTION: Find or enter the passed name in the name space.
 279  *              Log an error if name not found in Exec mode.
 280  *
 281  * MUTEX:       Assumes namespace is locked.
 282  *
 283  ******************************************************************************/
 284
 285 acpi_status
 286 acpi_ns_lookup(union acpi_generic_state *scope_info,
 287                char *pathname,
 288                acpi_object_type type,
 289                acpi_interpreter_mode interpreter_mode,
 290                u32 flags,
 291                struct acpi_walk_state *walk_state,
 292                struct acpi_namespace_node **return_node)
 293 {
 294         acpi_status status;
 295         char *path = pathname;
 296         struct acpi_namespace_node *prefix_node;
 297         struct acpi_namespace_node *current_node = NULL;
 298         struct acpi_namespace_node *this_node = NULL;
 299         u32 num_segments;
 300         u32 num_carats;
 301         acpi_name simple_name;
 302         acpi_object_type type_to_check_for;
 303         acpi_object_type this_search_type;
 304         u32 search_parent_flag = ACPI_NS_SEARCH_PARENT;
 305         u32 local_flags;
 306
 307         ACPI_FUNCTION_TRACE(ns_lookup);
 308
 309         if (!return_node) {
 310                 return_ACPI_STATUS(AE_BAD_PARAMETER);
 311         }
 312
 313         local_flags = flags & ~(ACPI_NS_ERROR_IF_FOUND | ACPI_NS_SEARCH_PARENT);
 314         *return_node = ACPI_ENTRY_NOT_FOUND;
 315         acpi_gbl_ns_lookup_count++;
 316
 317         if (!acpi_gbl_root_node) {
 318                 return_ACPI_STATUS(AE_NO_NAMESPACE);
 319         }
 320
 321         /*
 322          * Get the prefix scope.
 323          * A null scope means use the root scope
 324          */
 325         if ((!scope_info) || (!scope_info->scope.node)) {
 326                 ACPI_DEBUG_PRINT((ACPI_DB_NAMES,
 327                                   "Null scope prefix, using root node (%p)\n",
 328                                   acpi_gbl_root_node));
 329
 330                 prefix_node = acpi_gbl_root_node;
 331         } else {
 332                 prefix_node = scope_info->scope.node;
 333                 if (ACPI_GET_DESCRIPTOR_TYPE(prefix_node) !=
 334                     ACPI_DESC_TYPE_NAMED) {
 335                         ACPI_ERROR((AE_INFO, "%p is not a namespace node [%s]",
 336                                     prefix_node,
 337                                     acpi_ut_get_descriptor_name(prefix_node)));
 338                         return_ACPI_STATUS(AE_AML_INTERNAL);
 339                 }
 340
 341                 if (!(flags & ACPI_NS_PREFIX_IS_SCOPE)) {
 342                         /*
 343                          * This node might not be a actual "scope" node (such as a
 344                          * Device/Method, etc.)  It could be a Package or other object node.
 345                          * Backup up the tree to find the containing scope node.
 346                          */
 347                         while (!acpi_ns_opens_scope(prefix_node->type) &&
 348                                prefix_node->type != ACPI_TYPE_ANY) {
 349                                 prefix_node =
 350                                     acpi_ns_get_parent_node(prefix_node);
 351                         }
 352                 }
 353         }
 354
 355         /* Save type   TBD: may be no longer necessary */
 356
 357         type_to_check_for = type;
 358
 359         /*
 360          * Begin examination of the actual pathname
 361          */
 362         if (!pathname) {
 363
 364                 /* A Null name_path is allowed and refers to the root */
 365
 366                 num_segments = 0;
 367                 this_node = acpi_gbl_root_node;
 368                 path = "";
 369
 370                 ACPI_DEBUG_PRINT((ACPI_DB_NAMES,
 371                                   "Null Pathname (Zero segments), Flags=%X\n",
 372                                   flags));
 373         } else {
 374                 /*
 375                  * Name pointer is valid (and must be in internal name format)
 376                  *
 377                  * Check for scope prefixes:
 378                  *
 379                  * As represented in the AML stream, a namepath consists of an
 380                  * optional scope prefix followed by a name segment part.
 381                  *
 382                  * If present, the scope prefix is either a Root Prefix (in
 383                  * which case the name is fully qualified), or one or more
 384                  * Parent Prefixes (in which case the name's scope is relative
 385                  * to the current scope).
 386                  */
 387                 if (*path == (u8) AML_ROOT_PREFIX) {
 388
 389                         /* Pathname is fully qualified, start from the root */
 390
 391                         this_node = acpi_gbl_root_node;
 392                         search_parent_flag = ACPI_NS_NO_UPSEARCH;
 393
 394                         /* Point to name segment part */
 395
 396                         path++;
 397
 398                         ACPI_DEBUG_PRINT((ACPI_DB_NAMES,
 399                                           "Path is absolute from root [%p]\n",
 400                                           this_node));
 401                 } else {
 402                         /* Pathname is relative to current scope, start there */
 403
 404                         ACPI_DEBUG_PRINT((ACPI_DB_NAMES,
 405                                           "Searching relative to prefix scope [%4.4s] (%p)\n",
 406                                           acpi_ut_get_node_name(prefix_node),
 407                                           prefix_node));
 408
 409                         /*
 410                          * Handle multiple Parent Prefixes (carat) by just getting
 411                          * the parent node for each prefix instance.
 412                          */
 413                         this_node = prefix_node;
 414                         num_carats = 0;
 415                         while (*path == (u8) AML_PARENT_PREFIX) {
 416
 417                                 /* Name is fully qualified, no search rules apply */
 418
 419                                 search_parent_flag = ACPI_NS_NO_UPSEARCH;
 420                                 /*
 421                                  * Point past this prefix to the name segment
 422                                  * part or the next Parent Prefix
 423                                  */
 424                                 path++;
 425
 426                                 /* Backup to the parent node */
 427
 428                                 num_carats++;
 429                                 this_node = acpi_ns_get_parent_node(this_node);
 430                                 if (!this_node) {
 431
 432                                         /* Current scope has no parent scope */
 433
 434                                         ACPI_ERROR((AE_INFO,
 435                                                     "ACPI path has too many parent prefixes (^) - reached beyond root node"));
 436                                         return_ACPI_STATUS(AE_NOT_FOUND);
 437                                 }
 438                         }
 439
 440                         if (search_parent_flag == ACPI_NS_NO_UPSEARCH) {
 441                                 ACPI_DEBUG_PRINT((ACPI_DB_NAMES,
 442                                                   "Search scope is [%4.4s], path has %d carat(s)\n",
 443                                                   acpi_ut_get_node_name
 444                                                   (this_node), num_carats));
 445                         }
 446                 }
 447
 448                 /*
 449                  * Determine the number of ACPI name segments in this pathname.
 450                  *
 451                  * The segment part consists of either:
 452                  *  - A Null name segment (0)
 453                  *  - A dual_name_prefix followed by two 4-byte name segments
 454                  *  - A multi_name_prefix followed by a byte indicating the
 455                  *      number of segments and the segments themselves.
 456                  *  - A single 4-byte name segment
 457                  *
 458                  * Examine the name prefix opcode, if any, to determine the number of
 459                  * segments.
 460                  */
 461                 switch (*path) {
 462                 case 0:
 463                         /*
 464                          * Null name after a root or parent prefixes. We already
 465                          * have the correct target node and there are no name segments.
 466                          */
 467                         num_segments = 0;
 468                         type = this_node->type;
 469
 470                         ACPI_DEBUG_PRINT((ACPI_DB_NAMES,
 471                                           "Prefix-only Pathname (Zero name segments), Flags=%X\n",
 472                                           flags));
 473                         break;
 474
 475                 case AML_DUAL_NAME_PREFIX:
 476
 477                         /* More than one name_seg, search rules do not apply */
 478
 479                         search_parent_flag = ACPI_NS_NO_UPSEARCH;
 480
 481                         /* Two segments, point to first name segment */
 482
 483                         num_segments = 2;
 484                         path++;
 485
 486                         ACPI_DEBUG_PRINT((ACPI_DB_NAMES,
 487                                           "Dual Pathname (2 segments, Flags=%X)\n",
 488                                           flags));
 489                         break;
 490
 491                 case AML_MULTI_NAME_PREFIX_OP:
 492
 493                         /* More than one name_seg, search rules do not apply */
 494
 495                         search_parent_flag = ACPI_NS_NO_UPSEARCH;
 496
 497                         /* Extract segment count, point to first name segment */
 498
 499                         path++;
 500                         num_segments = (u32) (u8) * path;
 501                         path++;
 502
 503                         ACPI_DEBUG_PRINT((ACPI_DB_NAMES,
 504                                           "Multi Pathname (%d Segments, Flags=%X)\n",
 505                                           num_segments, flags));
 506                         break;
 507
 508                 default:
 509                         /*
 510                          * Not a Null name, no Dual or Multi prefix, hence there is
 511                          * only one name segment and Pathname is already pointing to it.
 512                          */
 513                         num_segments = 1;
 514
 515                         ACPI_DEBUG_PRINT((ACPI_DB_NAMES,
 516                                           "Simple Pathname (1 segment, Flags=%X)\n",
 517                                           flags));
 518                         break;
 519                 }
 520
 521                 ACPI_DEBUG_EXEC(acpi_ns_print_pathname(num_segments, path));
 522         }
 523
 524         /*
 525          * Search namespace for each segment of the name.  Loop through and
 526          * verify (or add to the namespace) each name segment.
 527          *
 528          * The object type is significant only at the last name
 529          * segment.  (We don't care about the types along the path, only
 530          * the type of the final target object.)
 531          */
 532         this_search_type = ACPI_TYPE_ANY;
 533         current_node = this_node;
 534         while (num_segments && current_node) {
 535                 num_segments--;
 536                 if (!num_segments) {
 537                         /*
 538                          * This is the last segment, enable typechecking
 539                          */
 540                         this_search_type = type;
 541
 542                         /*
 543                          * Only allow automatic parent search (search rules) if the caller
 544                          * requested it AND we have a single, non-fully-qualified name_seg
 545                          */
 546                         if ((search_parent_flag != ACPI_NS_NO_UPSEARCH) &&
 547                             (flags & ACPI_NS_SEARCH_PARENT)) {
 548                                 local_flags |= ACPI_NS_SEARCH_PARENT;
 549                         }
 550
 551                         /* Set error flag according to caller */
 552
 553                         if (flags & ACPI_NS_ERROR_IF_FOUND) {
 554                                 local_flags |= ACPI_NS_ERROR_IF_FOUND;
 555                         }
 556                 }
 557
 558                 /* Extract one ACPI name from the front of the pathname */
 559
 560                 ACPI_MOVE_32_TO_32(&simple_name, path);
 561
 562                 /* Try to find the single (4 character) ACPI name */
 563
 564                 status =
 565                     acpi_ns_search_and_enter(simple_name, walk_state,
 566                                              current_node, interpreter_mode,
 567                                              this_search_type, local_flags,
 568                                              &this_node);
 569                 if (ACPI_FAILURE(status)) {
 570                         if (status == AE_NOT_FOUND) {
 571
 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
 606                         /* Complain about a type mismatch */
 607
 608                         ACPI_WARNING((AE_INFO,
 609                                       "NsLookup: Type mismatch on %4.4s (%s), searching for (%s)",
 610                                       ACPI_CAST_PTR(char, &simple_name),
 611                                       acpi_ut_get_type_name(this_node->type),
 612                                       acpi_ut_get_type_name
 613                                       (type_to_check_for)));
 614                 }
 615
 616                 /*
 617                  * If this is the last name segment and we are not looking for a
 618                  * specific type, but the type of found object is known, use that type
 619                  * to see if it opens a scope.
 620                  */
 621                 if ((num_segments == 0) && (type == ACPI_TYPE_ANY)) {
 622                         type = this_node->type;
 623                 }
 624
 625                 /* Point to next name segment and make this node current */
 626
 627                 path += ACPI_NAME_SIZE;
 628                 current_node = this_node;
 629         }
 630
 631         /*
 632          * Always check if we need to open a new scope
 633          */
 634         if (!(flags & ACPI_NS_DONT_OPEN_SCOPE) && (walk_state)) {
 635                 /*
 636                  * If entry is a type which opens a scope, push the new scope on the
 637                  * scope stack.
 638                  */
 639                 if (acpi_ns_opens_scope(type)) {
 640                         status =
 641                             acpi_ds_scope_stack_push(this_node, type,
 642                                                      walk_state);
 643                         if (ACPI_FAILURE(status)) {
 644                                 return_ACPI_STATUS(status);
 645                         }
 646                 }
 647         }
 648
 649         *return_node = this_node;
 650         return_ACPI_STATUS(AE_OK);
 651 }