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 - 2005, 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
  45 #include <acpi/acpi.h>
  46 #include <acpi/amlcode.h>
  47 #include <acpi/acnamesp.h>
  48 #include <acpi/acdispat.h>
  49
  50
  51 #define _COMPONENT          ACPI_NAMESPACE
  52          ACPI_MODULE_NAME    ("nsaccess")
  53
  54
  55 /*******************************************************************************
  56  *
  57  * FUNCTION:    acpi_ns_root_initialize
  58  *
  59  * PARAMETERS:  None
  60  *
  61  * RETURN:      Status
  62  *
  63  * DESCRIPTION: Allocate and initialize the default root named objects
  64  *
  65  * MUTEX:       Locks namespace for entire execution
  66  *
  67  ******************************************************************************/
  68
  69 acpi_status
  70 acpi_ns_root_initialize (void)
  71 {
  72         acpi_status                         status;
  73         const struct acpi_predefined_names *init_val = NULL;
  74         struct acpi_namespace_node          *new_node;
  75         union acpi_operand_object           *obj_desc;
  76         acpi_string                         val = NULL;
  77
  78
  79         ACPI_FUNCTION_TRACE ("ns_root_initialize");
  80
  81
  82         status = acpi_ut_acquire_mutex (ACPI_MTX_NAMESPACE);
  83         if (ACPI_FAILURE (status)) {
  84                 return_ACPI_STATUS (status);
  85         }
  86
  87         /*
  88          * The global root ptr is initially NULL, so a non-NULL value indicates
  89          * that acpi_ns_root_initialize() has already been called; just return.
  90          */
  91         if (acpi_gbl_root_node) {
  92                 status = AE_OK;
  93                 goto unlock_and_exit;
  94         }
  95
  96         /*
  97          * Tell the rest of the subsystem that the root is initialized
  98          * (This is OK because the namespace is locked)
  99          */
 100         acpi_gbl_root_node = &acpi_gbl_root_node_struct;
 101
 102         /* Enter the pre-defined names in the name table */
 103
 104         ACPI_DEBUG_PRINT ((ACPI_DB_INFO,
 105                 "Entering predefined entries into namespace\n"));
 106
 107         for (init_val = acpi_gbl_pre_defined_names; init_val->name; init_val++) {
 108                 /* _OSI is optional for now, will be permanent later */
 109
 110                 if (!ACPI_STRCMP (init_val->name, "_OSI") && !acpi_gbl_create_osi_method) {
 111                         continue;
 112                 }
 113
 114                 status = acpi_ns_lookup (NULL, init_val->name, init_val->type,
 115                                   ACPI_IMODE_LOAD_PASS2, ACPI_NS_NO_UPSEARCH,
 116                                   NULL, &new_node);
 117
 118                 if (ACPI_FAILURE (status) || (!new_node)) /* Must be on same line for code converter */ {
 119                         ACPI_DEBUG_PRINT ((ACPI_DB_ERROR,
 120                                 "Could not create predefined name %s, %s\n",
 121                                 init_val->name, acpi_format_exception (status)));
 122                 }
 123
 124                 /*
 125                  * Name entered successfully.
 126                  * If entry in pre_defined_names[] specifies an
 127                  * initial value, create the initial value.
 128                  */
 129                 if (init_val->val) {
 130                         status = acpi_os_predefined_override (init_val, &val);
 131                         if (ACPI_FAILURE (status)) {
 132                                 ACPI_DEBUG_PRINT ((ACPI_DB_ERROR,
 133                                         "Could not override predefined %s\n",
 134                                         init_val->name));
 135                         }
 136
 137                         if (!val) {
 138                                 val = init_val->val;
 139                         }
 140
 141                         /*
 142                          * Entry requests an initial value, allocate a
 143                          * descriptor for it.
 144                          */
 145                         obj_desc = acpi_ut_create_internal_object (init_val->type);
 146                         if (!obj_desc) {
 147                                 status = AE_NO_MEMORY;
 148                                 goto unlock_and_exit;
 149                         }
 150
 151                         /*
 152                          * Convert value string from table entry to
 153                          * internal representation. Only types actually
 154                          * used for initial values are implemented here.
 155                          */
 156                         switch (init_val->type) {
 157                         case ACPI_TYPE_METHOD:
 158                                 obj_desc->method.param_count = (u8) ACPI_TO_INTEGER (val);
 159                                 obj_desc->common.flags |= AOPOBJ_DATA_VALID;
 160
 161 #if defined (_ACPI_ASL_COMPILER) || defined (_ACPI_DUMP_App)
 162
 163                                 /*
 164                                  * i_aSL Compiler cheats by putting parameter count
 165                                  * in the owner_iD
 166                                  */
 167                                 new_node->owner_id = obj_desc->method.param_count;
 168 #else
 169                                 /* Mark this as a very SPECIAL method */
 170
 171                                 obj_desc->method.method_flags = AML_METHOD_INTERNAL_ONLY;
 172                                 obj_desc->method.implementation = acpi_ut_osi_implementation;
 173 #endif
 174                                 break;
 175
 176                         case ACPI_TYPE_INTEGER:
 177
 178                                 obj_desc->integer.value = ACPI_TO_INTEGER (val);
 179                                 break;
 180
 181
 182                         case ACPI_TYPE_STRING:
 183
 184                                 /*
 185                                  * Build an object around the static string
 186                                  */
 187                                 obj_desc->string.length = (u32) ACPI_STRLEN (val);
 188                                 obj_desc->string.pointer = val;
 189                                 obj_desc->common.flags |= AOPOBJ_STATIC_POINTER;
 190                                 break;
 191
 192
 193                         case ACPI_TYPE_MUTEX:
 194
 195                                 obj_desc->mutex.node = new_node;
 196                                 obj_desc->mutex.sync_level = (u8) (ACPI_TO_INTEGER (val) - 1);
 197
 198                                 if (ACPI_STRCMP (init_val->name, "_GL_") == 0) {
 199                                         /*
 200                                          * Create a counting semaphore for the
 201                                          * global lock
 202                                          */
 203                                         status = acpi_os_create_semaphore (ACPI_NO_UNIT_LIMIT,
 204                                                          1, &obj_desc->mutex.semaphore);
 205                                         if (ACPI_FAILURE (status)) {
 206                                                 acpi_ut_remove_reference (obj_desc);
 207                                                 goto unlock_and_exit;
 208                                         }
 209
 210                                         /*
 211                                          * We just created the mutex for the
 212                                          * global lock, save it
 213                                          */
 214                                         acpi_gbl_global_lock_semaphore = obj_desc->mutex.semaphore;
 215                                 }
 216                                 else {
 217                                         /* Create a mutex */
 218
 219                                         status = acpi_os_create_semaphore (1, 1,
 220                                                            &obj_desc->mutex.semaphore);
 221                                         if (ACPI_FAILURE (status)) {
 222                                                 acpi_ut_remove_reference (obj_desc);
 223                                                 goto unlock_and_exit;
 224                                         }
 225                                 }
 226                                 break;
 227
 228
 229                         default:
 230
 231                                 ACPI_REPORT_ERROR (("Unsupported initial type value %X\n",
 232                                         init_val->type));
 233                                 acpi_ut_remove_reference (obj_desc);
 234                                 obj_desc = NULL;
 235                                 continue;
 236                         }
 237
 238                         /* Store pointer to value descriptor in the Node */
 239
 240                         status = acpi_ns_attach_object (new_node, obj_desc,
 241                                          ACPI_GET_OBJECT_TYPE (obj_desc));
 242
 243                         /* Remove local reference to the object */
 244
 245                         acpi_ut_remove_reference (obj_desc);
 246                 }
 247         }
 248
 249
 250 unlock_and_exit:
 251         (void) acpi_ut_release_mutex (ACPI_MTX_NAMESPACE);
 252
 253         /* Save a handle to "_GPE", it is always present */
 254
 255         if (ACPI_SUCCESS (status)) {
 256                 status = acpi_ns_get_node_by_path ("\\_GPE", NULL, ACPI_NS_NO_UPSEARCH,
 257                                   &acpi_gbl_fadt_gpe_device);
 258         }
 259
 260         return_ACPI_STATUS (status);
 261 }
 262
 263
 264 /*******************************************************************************
 265  *
 266  * FUNCTION:    acpi_ns_lookup
 267  *
 268  * PARAMETERS:  prefix_node     - Search scope if name is not fully qualified
 269  *              Pathname        - Search pathname, in internal format
 270  *                                (as represented in the AML stream)
 271  *              Type            - Type associated with name
 272  *              interpreter_mode - IMODE_LOAD_PASS2 => add name if not found
 273  *              Flags           - Flags describing the search restrictions
 274  *              walk_state      - Current state of the walk
 275  *              return_node     - Where the Node is placed (if found
 276  *                                or created successfully)
 277  *
 278  * RETURN:      Status
 279  *
 280  * DESCRIPTION: Find or enter the passed name in the name space.
 281  *              Log an error if name not found in Exec mode.
 282  *
 283  * MUTEX:       Assumes namespace is locked.
 284  *
 285  ******************************************************************************/
 286
 287 acpi_status
 288 acpi_ns_lookup (
 289         union acpi_generic_state        *scope_info,
 290         char                            *pathname,
 291         acpi_object_type                type,
 292         acpi_interpreter_mode           interpreter_mode,
 293         u32                             flags,
 294         struct acpi_walk_state          *walk_state,
 295         struct acpi_namespace_node      **return_node)
 296 {
 297         acpi_status                     status;
 298         char                            *path = pathname;
 299         struct acpi_namespace_node      *prefix_node;
 300         struct acpi_namespace_node      *current_node = NULL;
 301         struct acpi_namespace_node      *this_node = NULL;
 302         u32                             num_segments;
 303         u32                             num_carats;
 304         acpi_name                       simple_name;
 305         acpi_object_type                type_to_check_for;
 306         acpi_object_type                this_search_type;
 307         u32                             search_parent_flag = ACPI_NS_SEARCH_PARENT;
 308         u32                             local_flags = flags & ~(ACPI_NS_ERROR_IF_FOUND |
 309                            ACPI_NS_SEARCH_PARENT);
 310
 311
 312         ACPI_FUNCTION_TRACE ("ns_lookup");
 313
 314
 315         if (!return_node) {
 316                 return_ACPI_STATUS (AE_BAD_PARAMETER);
 317         }
 318
 319         acpi_gbl_ns_lookup_count++;
 320         *return_node = ACPI_ENTRY_NOT_FOUND;
 321
 322         if (!acpi_gbl_root_node) {
 323                 return_ACPI_STATUS (AE_NO_NAMESPACE);
 324         }
 325
 326         /*
 327          * Get the prefix scope.
 328          * A null scope means use the root scope
 329          */
 330         if ((!scope_info) ||
 331                 (!scope_info->scope.node)) {
 332                 ACPI_DEBUG_PRINT ((ACPI_DB_NAMES,
 333                         "Null scope prefix, using root node (%p)\n",
 334                         acpi_gbl_root_node));
 335
 336                 prefix_node = acpi_gbl_root_node;
 337         }
 338         else {
 339                 prefix_node = scope_info->scope.node;
 340                 if (ACPI_GET_DESCRIPTOR_TYPE (prefix_node) != ACPI_DESC_TYPE_NAMED) {
 341                         ACPI_REPORT_ERROR (("ns_lookup: %p is not a namespace node [%s]\n",
 342                                         prefix_node, acpi_ut_get_descriptor_name (prefix_node)));
 343                         return_ACPI_STATUS (AE_AML_INTERNAL);
 344                 }
 345
 346                 /*
 347                  * This node might not be a actual "scope" node (such as a
 348                  * Device/Method, etc.)  It could be a Package or other object node.
 349                  * Backup up the tree to find the containing scope node.
 350                  */
 351                 while (!acpi_ns_opens_scope (prefix_node->type) &&
 352                                 prefix_node->type != ACPI_TYPE_ANY) {
 353                         prefix_node = acpi_ns_get_parent_node (prefix_node);
 354                 }
 355         }
 356
 357         /* Save type   TBD: may be no longer necessary */
 358
 359         type_to_check_for = type;
 360
 361         /*
 362          * Begin examination of the actual pathname
 363          */
 364         if (!pathname) {
 365                 /* A Null name_path is allowed and refers to the root */
 366
 367                 num_segments = 0;
 368                 this_node    = acpi_gbl_root_node;
 369                 path     = "";
 370
 371                 ACPI_DEBUG_PRINT ((ACPI_DB_NAMES,
 372                         "Null Pathname (Zero segments), Flags=%X\n", flags));
 373         }
 374         else {
 375                 /*
 376                  * Name pointer is valid (and must be in internal name format)
 377                  *
 378                  * Check for scope prefixes:
 379                  *
 380                  * As represented in the AML stream, a namepath consists of an
 381                  * optional scope prefix followed by a name segment part.
 382                  *
 383                  * If present, the scope prefix is either a Root Prefix (in
 384                  * which case the name is fully qualified), or one or more
 385                  * Parent Prefixes (in which case the name's scope is relative
 386                  * to the current scope).
 387                  */
 388                 if (*path == (u8) AML_ROOT_PREFIX) {
 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", this_node));
 400                 }
 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), prefix_node));
 407
 408                         /*
 409                          * Handle multiple Parent Prefixes (carat) by just getting
 410                          * the parent node for each prefix instance.
 411                          */
 412                         this_node = prefix_node;
 413                         num_carats = 0;
 414                         while (*path == (u8) AML_PARENT_PREFIX) {
 415                                 /* Name is fully qualified, no search rules apply */
 416
 417                                 search_parent_flag = ACPI_NS_NO_UPSEARCH;
 418                                 /*
 419                                  * Point past this prefix to the name segment
 420                                  * part or the next Parent Prefix
 421                                  */
 422                                 path++;
 423
 424                                 /* Backup to the parent node */
 425
 426                                 num_carats++;
 427                                 this_node = acpi_ns_get_parent_node (this_node);
 428                                 if (!this_node) {
 429                                         /* Current scope has no parent scope */
 430
 431                                         ACPI_REPORT_ERROR (
 432                                                 ("ACPI path has too many parent prefixes (^) - reached beyond root node\n"));
 433                                         return_ACPI_STATUS (AE_NOT_FOUND);
 434                                 }
 435                         }
 436
 437                         if (search_parent_flag == ACPI_NS_NO_UPSEARCH) {
 438                                 ACPI_DEBUG_PRINT ((ACPI_DB_NAMES,
 439                                         "Search scope is [%4.4s], path has %d carat(s)\n",
 440                                         acpi_ut_get_node_name (this_node), num_carats));
 441                         }
 442                 }
 443
 444                 /*
 445                  * Determine the number of ACPI name segments in this pathname.
 446                  *
 447                  * The segment part consists of either:
 448                  *  - A Null name segment (0)
 449                  *  - A dual_name_prefix followed by two 4-byte name segments
 450                  *  - A multi_name_prefix followed by a byte indicating the
 451                  *      number of segments and the segments themselves.
 452                  *  - A single 4-byte name segment
 453                  *
 454                  * Examine the name prefix opcode, if any, to determine the number of
 455                  * segments.
 456                  */
 457                 switch (*path) {
 458                 case 0:
 459                         /*
 460                          * Null name after a root or parent prefixes. We already
 461                          * have the correct target node and there are no name segments.
 462                          */
 463                         num_segments = 0;
 464                         type = this_node->type;
 465
 466                         ACPI_DEBUG_PRINT ((ACPI_DB_NAMES,
 467                                 "Prefix-only Pathname (Zero name segments), Flags=%X\n",
 468                                 flags));
 469                         break;
 470
 471                 case AML_DUAL_NAME_PREFIX:
 472
 473                         /* More than one name_seg, search rules do not apply */
 474
 475                         search_parent_flag = ACPI_NS_NO_UPSEARCH;
 476
 477                         /* Two segments, point to first name segment */
 478
 479                         num_segments = 2;
 480                         path++;
 481
 482                         ACPI_DEBUG_PRINT ((ACPI_DB_NAMES,
 483                                 "Dual Pathname (2 segments, Flags=%X)\n", flags));
 484                         break;
 485
 486                 case AML_MULTI_NAME_PREFIX_OP:
 487
 488                         /* More than one name_seg, search rules do not apply */
 489
 490                         search_parent_flag = ACPI_NS_NO_UPSEARCH;
 491
 492                         /* Extract segment count, point to first name segment */
 493
 494                         path++;
 495                         num_segments = (u32) (u8) *path;
 496                         path++;
 497
 498                         ACPI_DEBUG_PRINT ((ACPI_DB_NAMES,
 499                                 "Multi Pathname (%d Segments, Flags=%X) \n",
 500                                 num_segments, flags));
 501                         break;
 502
 503                 default:
 504                         /*
 505                          * Not a Null name, no Dual or Multi prefix, hence there is
 506                          * only one name segment and Pathname is already pointing to it.
 507                          */
 508                         num_segments = 1;
 509
 510                         ACPI_DEBUG_PRINT ((ACPI_DB_NAMES,
 511                                 "Simple Pathname (1 segment, Flags=%X)\n", flags));
 512                         break;
 513                 }
 514
 515                 ACPI_DEBUG_EXEC (acpi_ns_print_pathname (num_segments, path));
 516         }
 517
 518
 519         /*
 520          * Search namespace for each segment of the name.  Loop through and
 521          * verify (or add to the namespace) each name segment.
 522          *
 523          * The object type is significant only at the last name
 524          * segment.  (We don't care about the types along the path, only
 525          * the type of the final target object.)
 526          */
 527         this_search_type = ACPI_TYPE_ANY;
 528         current_node = this_node;
 529         while (num_segments && current_node) {
 530                 num_segments--;
 531                 if (!num_segments) {
 532                         /*
 533                          * This is the last segment, enable typechecking
 534                          */
 535                         this_search_type = type;
 536
 537                         /*
 538                          * Only allow automatic parent search (search rules) if the caller
 539                          * requested it AND we have a single, non-fully-qualified name_seg
 540                          */
 541                         if ((search_parent_flag != ACPI_NS_NO_UPSEARCH) &&
 542                                 (flags & ACPI_NS_SEARCH_PARENT)) {
 543                                 local_flags |= ACPI_NS_SEARCH_PARENT;
 544                         }
 545
 546                         /* Set error flag according to caller */
 547
 548                         if (flags & ACPI_NS_ERROR_IF_FOUND) {
 549                                 local_flags |= ACPI_NS_ERROR_IF_FOUND;
 550                         }
 551                 }
 552
 553                 /* Extract one ACPI name from the front of the pathname */
 554
 555                 ACPI_MOVE_32_TO_32 (&simple_name, path);
 556
 557                 /* Try to find the single (4 character) ACPI name */
 558
 559                 status = acpi_ns_search_and_enter (simple_name, walk_state, current_node,
 560                                  interpreter_mode, this_search_type, local_flags, &this_node);
 561                 if (ACPI_FAILURE (status)) {
 562                         if (status == AE_NOT_FOUND) {
 563                                 /* Name not found in ACPI namespace */
 564
 565                                 ACPI_DEBUG_PRINT ((ACPI_DB_NAMES,
 566                                         "Name [%4.4s] not found in scope [%4.4s] %p\n",
 567                                         (char *) &simple_name, (char *) &current_node->name,
 568                                         current_node));
 569                         }
 570
 571                         *return_node = this_node;
 572                         return_ACPI_STATUS (status);
 573                 }
 574
 575                 /*
 576                  * Sanity typecheck of the target object:
 577                  *
 578                  * If 1) This is the last segment (num_segments == 0)
 579                  *    2) And we are looking for a specific type
 580                  *       (Not checking for TYPE_ANY)
 581                  *    3) Which is not an alias
 582                  *    4) Which is not a local type (TYPE_SCOPE)
 583                  *    5) And the type of target object is known (not TYPE_ANY)
 584                  *    6) And target object does not match what we are looking for
 585                  *
 586                  * Then we have a type mismatch.  Just warn and ignore it.
 587                  */
 588                 if ((num_segments       == 0)                               &&
 589                         (type_to_check_for  != ACPI_TYPE_ANY)                   &&
 590                         (type_to_check_for  != ACPI_TYPE_LOCAL_ALIAS)           &&
 591                         (type_to_check_for  != ACPI_TYPE_LOCAL_METHOD_ALIAS)    &&
 592                         (type_to_check_for  != ACPI_TYPE_LOCAL_SCOPE)           &&
 593                         (this_node->type    != ACPI_TYPE_ANY)                   &&
 594                         (this_node->type    != type_to_check_for)) {
 595                         /* Complain about a type mismatch */
 596
 597                         ACPI_REPORT_WARNING (
 598                                 ("ns_lookup: Type mismatch on %4.4s (%s), searching for (%s)\n",
 599                                 (char *) &simple_name, acpi_ut_get_type_name (this_node->type),
 600                                 acpi_ut_get_type_name (type_to_check_for)));
 601                 }
 602
 603                 /*
 604                  * If this is the last name segment and we are not looking for a
 605                  * specific type, but the type of found object is known, use that type
 606                  * to see if it opens a scope.
 607                  */
 608                 if ((num_segments == 0) && (type == ACPI_TYPE_ANY)) {
 609                         type = this_node->type;
 610                 }
 611
 612                 /* Point to next name segment and make this node current */
 613
 614                 path += ACPI_NAME_SIZE;
 615                 current_node = this_node;
 616         }
 617
 618         /*
 619          * Always check if we need to open a new scope
 620          */
 621         if (!(flags & ACPI_NS_DONT_OPEN_SCOPE) && (walk_state)) {
 622                 /*
 623                  * If entry is a type which opens a scope, push the new scope on the
 624                  * scope stack.
 625                  */
 626                 if (acpi_ns_opens_scope (type)) {
 627                         status = acpi_ds_scope_stack_push (this_node, type, walk_state);
 628                         if (ACPI_FAILURE (status)) {
 629                                 return_ACPI_STATUS (status);
 630                         }
 631                 }
 632         }
 633
 634         *return_node = this_node;
 635         return_ACPI_STATUS (AE_OK);
 636 }
 637