drivers/acpi/dispatcher/dsfield.c

   1 /******************************************************************************
   2  *
   3  * Module Name: dsfield - Dispatcher field 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/amlcode.h>
  46 #include <acpi/acdispat.h>
  47 #include <acpi/acinterp.h>
  48 #include <acpi/acnamesp.h>
  49 #include <acpi/acparser.h>
  50
  51 #define _COMPONENT          ACPI_DISPATCHER
  52 ACPI_MODULE_NAME("dsfield")
  53
  54 /* Local prototypes */
  55 static acpi_status
  56 acpi_ds_get_field_names(struct acpi_create_field_info *info,
  57                         struct acpi_walk_state *walk_state,
  58                         union acpi_parse_object *arg);
  59
  60 /*******************************************************************************
  61  *
  62  * FUNCTION:    acpi_ds_create_buffer_field
  63  *
  64  * PARAMETERS:  Op                  - Current parse op (create_xXField)
  65  *              walk_state          - Current state
  66  *
  67  * RETURN:      Status
  68  *
  69  * DESCRIPTION: Execute the create_field operators:
  70  *              create_bit_field_op,
  71  *              create_byte_field_op,
  72  *              create_word_field_op,
  73  *              create_dword_field_op,
  74  *              create_qword_field_op,
  75  *              create_field_op     (all of which define a field in a buffer)
  76  *
  77  ******************************************************************************/
  78
  79 acpi_status
  80 acpi_ds_create_buffer_field(union acpi_parse_object *op,
  81                             struct acpi_walk_state *walk_state)
  82 {
  83         union acpi_parse_object *arg;
  84         struct acpi_namespace_node *node;
  85         acpi_status status;
  86         union acpi_operand_object *obj_desc;
  87         union acpi_operand_object *second_desc = NULL;
  88         u32 flags;
  89
  90         ACPI_FUNCTION_TRACE(ds_create_buffer_field);
  91
  92         /*
  93          * Get the name_string argument (name of the new buffer_field)
  94          */
  95         if (op->common.aml_opcode == AML_CREATE_FIELD_OP) {
  96
  97                 /* For create_field, name is the 4th argument */
  98
  99                 arg = acpi_ps_get_arg(op, 3);
 100         } else {
 101                 /* For all other create_xXXField operators, name is the 3rd argument */
 102
 103                 arg = acpi_ps_get_arg(op, 2);
 104         }
 105
 106         if (!arg) {
 107                 return_ACPI_STATUS(AE_AML_NO_OPERAND);
 108         }
 109
 110         if (walk_state->deferred_node) {
 111                 node = walk_state->deferred_node;
 112                 status = AE_OK;
 113         } else {
 114                 /* Execute flag should always be set when this function is entered */
 115
 116                 if (!(walk_state->parse_flags & ACPI_PARSE_EXECUTE)) {
 117                         return_ACPI_STATUS(AE_AML_INTERNAL);
 118                 }
 119
 120                 /* Creating new namespace node, should not already exist */
 121
 122                 flags = ACPI_NS_NO_UPSEARCH | ACPI_NS_DONT_OPEN_SCOPE |
 123                     ACPI_NS_ERROR_IF_FOUND;
 124
 125                 /* Mark node temporary if we are executing a method */
 126
 127                 if (walk_state->method_node) {
 128                         flags |= ACPI_NS_TEMPORARY;
 129                 }
 130
 131                 /* Enter the name_string into the namespace */
 132
 133                 status =
 134                     acpi_ns_lookup(walk_state->scope_info,
 135                                    arg->common.value.string, ACPI_TYPE_ANY,
 136                                    ACPI_IMODE_LOAD_PASS1, flags, walk_state,
 137                                    &node);
 138                 if (ACPI_FAILURE(status)) {
 139                         ACPI_ERROR_NAMESPACE(arg->common.value.string, status);
 140                         return_ACPI_STATUS(status);
 141                 }
 142         }
 143
 144         /*
 145          * We could put the returned object (Node) on the object stack for later,
 146          * but for now, we will put it in the "op" object that the parser uses,
 147          * so we can get it again at the end of this scope.
 148          */
 149         op->common.node = node;
 150
 151         /*
 152          * If there is no object attached to the node, this node was just created
 153          * and we need to create the field object. Otherwise, this was a lookup
 154          * of an existing node and we don't want to create the field object again.
 155          */
 156         obj_desc = acpi_ns_get_attached_object(node);
 157         if (obj_desc) {
 158                 return_ACPI_STATUS(AE_OK);
 159         }
 160
 161         /*
 162          * The Field definition is not fully parsed at this time.
 163          * (We must save the address of the AML for the buffer and index operands)
 164          */
 165
 166         /* Create the buffer field object */
 167
 168         obj_desc = acpi_ut_create_internal_object(ACPI_TYPE_BUFFER_FIELD);
 169         if (!obj_desc) {
 170                 status = AE_NO_MEMORY;
 171                 goto cleanup;
 172         }
 173
 174         /*
 175          * Remember location in AML stream of the field unit opcode and operands --
 176          * since the buffer and index operands must be evaluated.
 177          */
 178         second_desc = obj_desc->common.next_object;
 179         second_desc->extra.aml_start = op->named.data;
 180         second_desc->extra.aml_length = op->named.length;
 181         obj_desc->buffer_field.node = node;
 182
 183         /* Attach constructed field descriptors to parent node */
 184
 185         status = acpi_ns_attach_object(node, obj_desc, ACPI_TYPE_BUFFER_FIELD);
 186         if (ACPI_FAILURE(status)) {
 187                 goto cleanup;
 188         }
 189
 190       cleanup:
 191
 192         /* Remove local reference to the object */
 193
 194         acpi_ut_remove_reference(obj_desc);
 195         return_ACPI_STATUS(status);
 196 }
 197
 198 /*******************************************************************************
 199  *
 200  * FUNCTION:    acpi_ds_get_field_names
 201  *
 202  * PARAMETERS:  Info            - create_field info structure
 203  *  `           walk_state      - Current method state
 204  *              Arg             - First parser arg for the field name list
 205  *
 206  * RETURN:      Status
 207  *
 208  * DESCRIPTION: Process all named fields in a field declaration.  Names are
 209  *              entered into the namespace.
 210  *
 211  ******************************************************************************/
 212
 213 static acpi_status
 214 acpi_ds_get_field_names(struct acpi_create_field_info *info,
 215                         struct acpi_walk_state *walk_state,
 216                         union acpi_parse_object *arg)
 217 {
 218         acpi_status status;
 219         acpi_integer position;
 220
 221         ACPI_FUNCTION_TRACE_PTR(ds_get_field_names, info);
 222
 223         /* First field starts at bit zero */
 224
 225         info->field_bit_position = 0;
 226
 227         /* Process all elements in the field list (of parse nodes) */
 228
 229         while (arg) {
 230                 /*
 231                  * Three types of field elements are handled:
 232                  * 1) Offset - specifies a bit offset
 233                  * 2) access_as - changes the access mode
 234                  * 3) Name - Enters a new named field into the namespace
 235                  */
 236                 switch (arg->common.aml_opcode) {
 237                 case AML_INT_RESERVEDFIELD_OP:
 238
 239                         position = (acpi_integer) info->field_bit_position
 240                             + (acpi_integer) arg->common.value.size;
 241
 242                         if (position > ACPI_UINT32_MAX) {
 243                                 ACPI_ERROR((AE_INFO,
 244                                             "Bit offset within field too large (> 0xFFFFFFFF)"));
 245                                 return_ACPI_STATUS(AE_SUPPORT);
 246                         }
 247
 248                         info->field_bit_position = (u32) position;
 249                         break;
 250
 251                 case AML_INT_ACCESSFIELD_OP:
 252
 253                         /*
 254                          * Get a new access_type and access_attribute -- to be used for all
 255                          * field units that follow, until field end or another access_as
 256                          * keyword.
 257                          *
 258                          * In field_flags, preserve the flag bits other than the
 259                          * ACCESS_TYPE bits
 260                          */
 261                         info->field_flags = (u8)
 262                             ((info->
 263                               field_flags & ~(AML_FIELD_ACCESS_TYPE_MASK)) |
 264                              ((u8) ((u32) arg->common.value.integer >> 8)));
 265
 266                         info->attribute = (u8) (arg->common.value.integer);
 267                         break;
 268
 269                 case AML_INT_NAMEDFIELD_OP:
 270
 271                         /* Lookup the name, it should already exist */
 272
 273                         status = acpi_ns_lookup(walk_state->scope_info,
 274                                                 (char *)&arg->named.name,
 275                                                 info->field_type,
 276                                                 ACPI_IMODE_EXECUTE,
 277                                                 ACPI_NS_DONT_OPEN_SCOPE,
 278                                                 walk_state, &info->field_node);
 279                         if (ACPI_FAILURE(status)) {
 280                                 ACPI_ERROR_NAMESPACE((char *)&arg->named.name,
 281                                                      status);
 282                                 return_ACPI_STATUS(status);
 283                         } else {
 284                                 arg->common.node = info->field_node;
 285                                 info->field_bit_length = arg->common.value.size;
 286
 287                                 /*
 288                                  * If there is no object attached to the node, this node was
 289                                  * just created and we need to create the field object.
 290                                  * Otherwise, this was a lookup of an existing node and we
 291                                  * don't want to create the field object again.
 292                                  */
 293                                 if (!acpi_ns_get_attached_object
 294                                     (info->field_node)) {
 295                                         status = acpi_ex_prep_field_value(info);
 296                                         if (ACPI_FAILURE(status)) {
 297                                                 return_ACPI_STATUS(status);
 298                                         }
 299                                 }
 300                         }
 301
 302                         /* Keep track of bit position for the next field */
 303
 304                         position = (acpi_integer) info->field_bit_position
 305                             + (acpi_integer) arg->common.value.size;
 306
 307                         if (position > ACPI_UINT32_MAX) {
 308                                 ACPI_ERROR((AE_INFO,
 309                                             "Field [%4.4s] bit offset too large (> 0xFFFFFFFF)",
 310                                             ACPI_CAST_PTR(char,
 311                                                           &info->field_node->
 312                                                           name)));
 313                                 return_ACPI_STATUS(AE_SUPPORT);
 314                         }
 315
 316                         info->field_bit_position += info->field_bit_length;
 317                         break;
 318
 319                 default:
 320
 321                         ACPI_ERROR((AE_INFO,
 322                                     "Invalid opcode in field list: %X",
 323                                     arg->common.aml_opcode));
 324                         return_ACPI_STATUS(AE_AML_BAD_OPCODE);
 325                 }
 326
 327                 arg = arg->common.next;
 328         }
 329
 330         return_ACPI_STATUS(AE_OK);
 331 }
 332
 333 /*******************************************************************************
 334  *
 335  * FUNCTION:    acpi_ds_create_field
 336  *
 337  * PARAMETERS:  Op              - Op containing the Field definition and args
 338  *              region_node     - Object for the containing Operation Region
 339  *  `           walk_state      - Current method state
 340  *
 341  * RETURN:      Status
 342  *
 343  * DESCRIPTION: Create a new field in the specified operation region
 344  *
 345  ******************************************************************************/
 346
 347 acpi_status
 348 acpi_ds_create_field(union acpi_parse_object *op,
 349                      struct acpi_namespace_node *region_node,
 350                      struct acpi_walk_state *walk_state)
 351 {
 352         acpi_status status;
 353         union acpi_parse_object *arg;
 354         struct acpi_create_field_info info;
 355
 356         ACPI_FUNCTION_TRACE_PTR(ds_create_field, op);
 357
 358         /* First arg is the name of the parent op_region (must already exist) */
 359
 360         arg = op->common.value.arg;
 361         if (!region_node) {
 362                 status =
 363                     acpi_ns_lookup(walk_state->scope_info,
 364                                    arg->common.value.name, ACPI_TYPE_REGION,
 365                                    ACPI_IMODE_EXECUTE, ACPI_NS_SEARCH_PARENT,
 366                                    walk_state, &region_node);
 367                 if (ACPI_FAILURE(status)) {
 368                         ACPI_ERROR_NAMESPACE(arg->common.value.name, status);
 369                         return_ACPI_STATUS(status);
 370                 }
 371         }
 372
 373         /* Second arg is the field flags */
 374
 375         arg = arg->common.next;
 376         info.field_flags = (u8) arg->common.value.integer;
 377         info.attribute = 0;
 378
 379         /* Each remaining arg is a Named Field */
 380
 381         info.field_type = ACPI_TYPE_LOCAL_REGION_FIELD;
 382         info.region_node = region_node;
 383
 384         status = acpi_ds_get_field_names(&info, walk_state, arg->common.next);
 385
 386         return_ACPI_STATUS(status);
 387 }
 388
 389 /*******************************************************************************
 390  *
 391  * FUNCTION:    acpi_ds_init_field_objects
 392  *
 393  * PARAMETERS:  Op              - Op containing the Field definition and args
 394  *  `           walk_state      - Current method state
 395  *
 396  * RETURN:      Status
 397  *
 398  * DESCRIPTION: For each "Field Unit" name in the argument list that is
 399  *              part of the field declaration, enter the name into the
 400  *              namespace.
 401  *
 402  ******************************************************************************/
 403
 404 acpi_status
 405 acpi_ds_init_field_objects(union acpi_parse_object *op,
 406                            struct acpi_walk_state *walk_state)
 407 {
 408         acpi_status status;
 409         union acpi_parse_object *arg = NULL;
 410         struct acpi_namespace_node *node;
 411         u8 type = 0;
 412         u32 flags;
 413
 414         ACPI_FUNCTION_TRACE_PTR(ds_init_field_objects, op);
 415
 416         /* Execute flag should always be set when this function is entered */
 417
 418         if (!(walk_state->parse_flags & ACPI_PARSE_EXECUTE)) {
 419                 if (walk_state->parse_flags & ACPI_PARSE_DEFERRED_OP) {
 420
 421                         /* bank_field Op is deferred, just return OK */
 422
 423                         return_ACPI_STATUS(AE_OK);
 424                 }
 425
 426                 return_ACPI_STATUS(AE_AML_INTERNAL);
 427         }
 428
 429         /*
 430          * Get the field_list argument for this opcode. This is the start of the
 431          * list of field elements.
 432          */
 433         switch (walk_state->opcode) {
 434         case AML_FIELD_OP:
 435                 arg = acpi_ps_get_arg(op, 2);
 436                 type = ACPI_TYPE_LOCAL_REGION_FIELD;
 437                 break;
 438
 439         case AML_BANK_FIELD_OP:
 440                 arg = acpi_ps_get_arg(op, 4);
 441                 type = ACPI_TYPE_LOCAL_BANK_FIELD;
 442                 break;
 443
 444         case AML_INDEX_FIELD_OP:
 445                 arg = acpi_ps_get_arg(op, 3);
 446                 type = ACPI_TYPE_LOCAL_INDEX_FIELD;
 447                 break;
 448
 449         default:
 450                 return_ACPI_STATUS(AE_BAD_PARAMETER);
 451         }
 452
 453         /* Creating new namespace node(s), should not already exist */
 454
 455         flags = ACPI_NS_NO_UPSEARCH | ACPI_NS_DONT_OPEN_SCOPE |
 456             ACPI_NS_ERROR_IF_FOUND;
 457
 458         /* Mark node(s) temporary if we are executing a method */
 459
 460         if (walk_state->method_node) {
 461                 flags |= ACPI_NS_TEMPORARY;
 462         }
 463
 464         /*
 465          * Walk the list of entries in the field_list
 466          * Note: field_list can be of zero length. In this case, Arg will be NULL.
 467          */
 468         while (arg) {
 469                 /*
 470                  * Ignore OFFSET and ACCESSAS terms here; we are only interested in the
 471                  * field names in order to enter them into the namespace.
 472                  */
 473                 if (arg->common.aml_opcode == AML_INT_NAMEDFIELD_OP) {
 474                         status = acpi_ns_lookup(walk_state->scope_info,
 475                                                 (char *)&arg->named.name, type,
 476                                                 ACPI_IMODE_LOAD_PASS1, flags,
 477                                                 walk_state, &node);
 478                         if (ACPI_FAILURE(status)) {
 479                                 ACPI_ERROR_NAMESPACE((char *)&arg->named.name,
 480                                                      status);
 481                                 if (status != AE_ALREADY_EXISTS) {
 482                                         return_ACPI_STATUS(status);
 483                                 }
 484
 485                                 /* Name already exists, just ignore this error */
 486
 487                                 status = AE_OK;
 488                         }
 489
 490                         arg->common.node = node;
 491                 }
 492
 493                 /* Get the next field element in the list */
 494
 495                 arg = arg->common.next;
 496         }
 497
 498         return_ACPI_STATUS(AE_OK);
 499 }
 500
 501 /*******************************************************************************
 502  *
 503  * FUNCTION:    acpi_ds_create_bank_field
 504  *
 505  * PARAMETERS:  Op              - Op containing the Field definition and args
 506  *              region_node     - Object for the containing Operation Region
 507  *              walk_state      - Current method state
 508  *
 509  * RETURN:      Status
 510  *
 511  * DESCRIPTION: Create a new bank field in the specified operation region
 512  *
 513  ******************************************************************************/
 514
 515 acpi_status
 516 acpi_ds_create_bank_field(union acpi_parse_object *op,
 517                           struct acpi_namespace_node *region_node,
 518                           struct acpi_walk_state *walk_state)
 519 {
 520         acpi_status status;
 521         union acpi_parse_object *arg;
 522         struct acpi_create_field_info info;
 523
 524         ACPI_FUNCTION_TRACE_PTR(ds_create_bank_field, op);
 525
 526         /* First arg is the name of the parent op_region (must already exist) */
 527
 528         arg = op->common.value.arg;
 529         if (!region_node) {
 530                 status =
 531                     acpi_ns_lookup(walk_state->scope_info,
 532                                    arg->common.value.name, ACPI_TYPE_REGION,
 533                                    ACPI_IMODE_EXECUTE, ACPI_NS_SEARCH_PARENT,
 534                                    walk_state, &region_node);
 535                 if (ACPI_FAILURE(status)) {
 536                         ACPI_ERROR_NAMESPACE(arg->common.value.name, status);
 537                         return_ACPI_STATUS(status);
 538                 }
 539         }
 540
 541         /* Second arg is the Bank Register (Field) (must already exist) */
 542
 543         arg = arg->common.next;
 544         status =
 545             acpi_ns_lookup(walk_state->scope_info, arg->common.value.string,
 546                            ACPI_TYPE_ANY, ACPI_IMODE_EXECUTE,
 547                            ACPI_NS_SEARCH_PARENT, walk_state,
 548                            &info.register_node);
 549         if (ACPI_FAILURE(status)) {
 550                 ACPI_ERROR_NAMESPACE(arg->common.value.string, status);
 551                 return_ACPI_STATUS(status);
 552         }
 553
 554         /*
 555          * Third arg is the bank_value
 556          * This arg is a term_arg, not a constant
 557          * It will be evaluated later, by acpi_ds_eval_bank_field_operands
 558          */
 559         arg = arg->common.next;
 560
 561         /* Fourth arg is the field flags */
 562
 563         arg = arg->common.next;
 564         info.field_flags = (u8) arg->common.value.integer;
 565
 566         /* Each remaining arg is a Named Field */
 567
 568         info.field_type = ACPI_TYPE_LOCAL_BANK_FIELD;
 569         info.region_node = region_node;
 570
 571         /*
 572          * Use Info.data_register_node to store bank_field Op
 573          * It's safe because data_register_node will never be used when create bank field
 574          * We store aml_start and aml_length in the bank_field Op for late evaluation
 575          * Used in acpi_ex_prep_field_value(Info)
 576          *
 577          * TBD: Or, should we add a field in struct acpi_create_field_info, like "void *ParentOp"?
 578          */
 579         info.data_register_node = (struct acpi_namespace_node *)op;
 580
 581         status = acpi_ds_get_field_names(&info, walk_state, arg->common.next);
 582         return_ACPI_STATUS(status);
 583 }
 584
 585 /*******************************************************************************
 586  *
 587  * FUNCTION:    acpi_ds_create_index_field
 588  *
 589  * PARAMETERS:  Op              - Op containing the Field definition and args
 590  *              region_node     - Object for the containing Operation Region
 591  *  `           walk_state      - Current method state
 592  *
 593  * RETURN:      Status
 594  *
 595  * DESCRIPTION: Create a new index field in the specified operation region
 596  *
 597  ******************************************************************************/
 598
 599 acpi_status
 600 acpi_ds_create_index_field(union acpi_parse_object *op,
 601                            struct acpi_namespace_node *region_node,
 602                            struct acpi_walk_state *walk_state)
 603 {
 604         acpi_status status;
 605         union acpi_parse_object *arg;
 606         struct acpi_create_field_info info;
 607
 608         ACPI_FUNCTION_TRACE_PTR(ds_create_index_field, op);
 609
 610         /* First arg is the name of the Index register (must already exist) */
 611
 612         arg = op->common.value.arg;
 613         status =
 614             acpi_ns_lookup(walk_state->scope_info, arg->common.value.string,
 615                            ACPI_TYPE_ANY, ACPI_IMODE_EXECUTE,
 616                            ACPI_NS_SEARCH_PARENT, walk_state,
 617                            &info.register_node);
 618         if (ACPI_FAILURE(status)) {
 619                 ACPI_ERROR_NAMESPACE(arg->common.value.string, status);
 620                 return_ACPI_STATUS(status);
 621         }
 622
 623         /* Second arg is the data register (must already exist) */
 624
 625         arg = arg->common.next;
 626         status =
 627             acpi_ns_lookup(walk_state->scope_info, arg->common.value.string,
 628                            ACPI_TYPE_ANY, ACPI_IMODE_EXECUTE,
 629                            ACPI_NS_SEARCH_PARENT, walk_state,
 630                            &info.data_register_node);
 631         if (ACPI_FAILURE(status)) {
 632                 ACPI_ERROR_NAMESPACE(arg->common.value.string, status);
 633                 return_ACPI_STATUS(status);
 634         }
 635
 636         /* Next arg is the field flags */
 637
 638         arg = arg->common.next;
 639         info.field_flags = (u8) arg->common.value.integer;
 640
 641         /* Each remaining arg is a Named Field */
 642
 643         info.field_type = ACPI_TYPE_LOCAL_INDEX_FIELD;
 644         info.region_node = region_node;
 645
 646         status = acpi_ds_get_field_names(&info, walk_state, arg->common.next);
 647
 648         return_ACPI_STATUS(status);
 649 }