drivers/acpi/utils.c

   1 /*
   2  *  acpi_utils.c - ACPI Utility Functions ($Revision: 10 $)
   3  *
   4  *  Copyright (C) 2001, 2002 Andy Grover <andrew.grover@intel.com>
   5  *  Copyright (C) 2001, 2002 Paul Diefenbaugh <paul.s.diefenbaugh@intel.com>
   6  *
   7  * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   8  *
   9  *  This program is free software; you can redistribute it and/or modify
  10  *  it under the terms of the GNU General Public License as published by
  11  *  the Free Software Foundation; either version 2 of the License, or (at
  12  *  your option) any later version.
  13  *
  14  *  This program is distributed in the hope that it will be useful, but
  15  *  WITHOUT ANY WARRANTY; without even the implied warranty of
  16  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  17  *  General Public License for more details.
  18  *
  19  * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  20  */
  21
  22 #include <linux/kernel.h>
  23 #include <linux/module.h>
  24 #include <linux/slab.h>
  25 #include <linux/init.h>
  26 #include <linux/types.h>
  27 #include <linux/hardirq.h>
  28 #include <linux/acpi.h>
  29 #include <linux/dynamic_debug.h>
  30
  31 #include "internal.h"
  32
  33 #define _COMPONENT              ACPI_BUS_COMPONENT
  34 ACPI_MODULE_NAME("utils");
  35
  36 /* --------------------------------------------------------------------------
  37                             Object Evaluation Helpers
  38    -------------------------------------------------------------------------- */
  39 static void
  40 acpi_util_eval_error(acpi_handle h, acpi_string p, acpi_status s)
  41 {
  42 #ifdef ACPI_DEBUG_OUTPUT
  43         char prefix[80] = {'\0'};
  44         struct acpi_buffer buffer = {sizeof(prefix), prefix};
  45         acpi_get_name(h, ACPI_FULL_PATHNAME, &buffer);
  46         ACPI_DEBUG_PRINT((ACPI_DB_INFO, "Evaluate [%s.%s]: %s\n",
  47                 (char *) prefix, p, acpi_format_exception(s)));
  48 #else
  49         return;
  50 #endif
  51 }
  52
  53 acpi_status
  54 acpi_extract_package(union acpi_object *package,
  55                      struct acpi_buffer *format, struct acpi_buffer *buffer)
  56 {
  57         u32 size_required = 0;
  58         u32 tail_offset = 0;
  59         char *format_string = NULL;
  60         u32 format_count = 0;
  61         u32 i = 0;
  62         u8 *head = NULL;
  63         u8 *tail = NULL;
  64
  65
  66         if (!package || (package->type != ACPI_TYPE_PACKAGE)
  67             || (package->package.count < 1)) {
  68                 printk(KERN_WARNING PREFIX "Invalid package argument\n");
  69                 return AE_BAD_PARAMETER;
  70         }
  71
  72         if (!format || !format->pointer || (format->length < 1)) {
  73                 printk(KERN_WARNING PREFIX "Invalid format argument\n");
  74                 return AE_BAD_PARAMETER;
  75         }
  76
  77         if (!buffer) {
  78                 printk(KERN_WARNING PREFIX "Invalid buffer argument\n");
  79                 return AE_BAD_PARAMETER;
  80         }
  81
  82         format_count = (format->length / sizeof(char)) - 1;
  83         if (format_count > package->package.count) {
  84                 printk(KERN_WARNING PREFIX "Format specifies more objects [%d]"
  85                               " than exist in package [%d].\n",
  86                               format_count, package->package.count);
  87                 return AE_BAD_DATA;
  88         }
  89
  90         format_string = format->pointer;
  91
  92         /*
  93          * Calculate size_required.
  94          */
  95         for (i = 0; i < format_count; i++) {
  96
  97                 union acpi_object *element = &(package->package.elements[i]);
  98
  99                 switch (element->type) {
 100
 101                 case ACPI_TYPE_INTEGER:
 102                         switch (format_string[i]) {
 103                         case 'N':
 104                                 size_required += sizeof(u64);
 105                                 tail_offset += sizeof(u64);
 106                                 break;
 107                         case 'S':
 108                                 size_required +=
 109                                     sizeof(char *) + sizeof(u64) +
 110                                     sizeof(char);
 111                                 tail_offset += sizeof(char *);
 112                                 break;
 113                         default:
 114                                 printk(KERN_WARNING PREFIX "Invalid package element"
 115                                               " [%d]: got number, expecting"
 116                                               " [%c]\n",
 117                                               i, format_string[i]);
 118                                 return AE_BAD_DATA;
 119                                 break;
 120                         }
 121                         break;
 122
 123                 case ACPI_TYPE_STRING:
 124                 case ACPI_TYPE_BUFFER:
 125                         switch (format_string[i]) {
 126                         case 'S':
 127                                 size_required +=
 128                                     sizeof(char *) +
 129                                     (element->string.length * sizeof(char)) +
 130                                     sizeof(char);
 131                                 tail_offset += sizeof(char *);
 132                                 break;
 133                         case 'B':
 134                                 size_required +=
 135                                     sizeof(u8 *) + element->buffer.length;
 136                                 tail_offset += sizeof(u8 *);
 137                                 break;
 138                         default:
 139                                 printk(KERN_WARNING PREFIX "Invalid package element"
 140                                               " [%d] got string/buffer,"
 141                                               " expecting [%c]\n",
 142                                               i, format_string[i]);
 143                                 return AE_BAD_DATA;
 144                                 break;
 145                         }
 146                         break;
 147                 case ACPI_TYPE_LOCAL_REFERENCE:
 148                         switch (format_string[i]) {
 149                         case 'R':
 150                                 size_required += sizeof(void *);
 151                                 tail_offset += sizeof(void *);
 152                                 break;
 153                         default:
 154                                 printk(KERN_WARNING PREFIX "Invalid package element"
 155                                               " [%d] got reference,"
 156                                               " expecting [%c]\n",
 157                                               i, format_string[i]);
 158                                 return AE_BAD_DATA;
 159                                 break;
 160                         }
 161                         break;
 162
 163                 case ACPI_TYPE_PACKAGE:
 164                 default:
 165                         ACPI_DEBUG_PRINT((ACPI_DB_INFO,
 166                                           "Found unsupported element at index=%d\n",
 167                                           i));
 168                         /* TBD: handle nested packages... */
 169                         return AE_SUPPORT;
 170                         break;
 171                 }
 172         }
 173
 174         /*
 175          * Validate output buffer.
 176          */
 177         if (buffer->length == ACPI_ALLOCATE_BUFFER) {
 178                 buffer->pointer = ACPI_ALLOCATE_ZEROED(size_required);
 179                 if (!buffer->pointer)
 180                         return AE_NO_MEMORY;
 181                 buffer->length = size_required;
 182         } else {
 183                 if (buffer->length < size_required) {
 184                         buffer->length = size_required;
 185                         return AE_BUFFER_OVERFLOW;
 186                 } else if (buffer->length != size_required ||
 187                            !buffer->pointer) {
 188                         return AE_BAD_PARAMETER;
 189                 }
 190         }
 191
 192         head = buffer->pointer;
 193         tail = buffer->pointer + tail_offset;
 194
 195         /*
 196          * Extract package data.
 197          */
 198         for (i = 0; i < format_count; i++) {
 199
 200                 u8 **pointer = NULL;
 201                 union acpi_object *element = &(package->package.elements[i]);
 202
 203                 if (!element) {
 204                         return AE_BAD_DATA;
 205                 }
 206
 207                 switch (element->type) {
 208
 209                 case ACPI_TYPE_INTEGER:
 210                         switch (format_string[i]) {
 211                         case 'N':
 212                                 *((u64 *) head) =
 213                                     element->integer.value;
 214                                 head += sizeof(u64);
 215                                 break;
 216                         case 'S':
 217                                 pointer = (u8 **) head;
 218                                 *pointer = tail;
 219                                 *((u64 *) tail) =
 220                                     element->integer.value;
 221                                 head += sizeof(u64 *);
 222                                 tail += sizeof(u64);
 223                                 /* NULL terminate string */
 224                                 *tail = (char)0;
 225                                 tail += sizeof(char);
 226                                 break;
 227                         default:
 228                                 /* Should never get here */
 229                                 break;
 230                         }
 231                         break;
 232
 233                 case ACPI_TYPE_STRING:
 234                 case ACPI_TYPE_BUFFER:
 235                         switch (format_string[i]) {
 236                         case 'S':
 237                                 pointer = (u8 **) head;
 238                                 *pointer = tail;
 239                                 memcpy(tail, element->string.pointer,
 240                                        element->string.length);
 241                                 head += sizeof(char *);
 242                                 tail += element->string.length * sizeof(char);
 243                                 /* NULL terminate string */
 244                                 *tail = (char)0;
 245                                 tail += sizeof(char);
 246                                 break;
 247                         case 'B':
 248                                 pointer = (u8 **) head;
 249                                 *pointer = tail;
 250                                 memcpy(tail, element->buffer.pointer,
 251                                        element->buffer.length);
 252                                 head += sizeof(u8 *);
 253                                 tail += element->buffer.length;
 254                                 break;
 255                         default:
 256                                 /* Should never get here */
 257                                 break;
 258                         }
 259                         break;
 260                 case ACPI_TYPE_LOCAL_REFERENCE:
 261                         switch (format_string[i]) {
 262                         case 'R':
 263                                 *(void **)head =
 264                                     (void *)element->reference.handle;
 265                                 head += sizeof(void *);
 266                                 break;
 267                         default:
 268                                 /* Should never get here */
 269                                 break;
 270                         }
 271                         break;
 272                 case ACPI_TYPE_PACKAGE:
 273                         /* TBD: handle nested packages... */
 274                 default:
 275                         /* Should never get here */
 276                         break;
 277                 }
 278         }
 279
 280         return AE_OK;
 281 }
 282
 283 EXPORT_SYMBOL(acpi_extract_package);
 284
 285 acpi_status
 286 acpi_evaluate_integer(acpi_handle handle,
 287                       acpi_string pathname,
 288                       struct acpi_object_list *arguments, unsigned long long *data)
 289 {
 290         acpi_status status = AE_OK;
 291         union acpi_object element;
 292         struct acpi_buffer buffer = { 0, NULL };
 293
 294         if (!data)
 295                 return AE_BAD_PARAMETER;
 296
 297         buffer.length = sizeof(union acpi_object);
 298         buffer.pointer = &element;
 299         status = acpi_evaluate_object(handle, pathname, arguments, &buffer);
 300         if (ACPI_FAILURE(status)) {
 301                 acpi_util_eval_error(handle, pathname, status);
 302                 return status;
 303         }
 304
 305         if (element.type != ACPI_TYPE_INTEGER) {
 306                 acpi_util_eval_error(handle, pathname, AE_BAD_DATA);
 307                 return AE_BAD_DATA;
 308         }
 309
 310         *data = element.integer.value;
 311
 312         ACPI_DEBUG_PRINT((ACPI_DB_INFO, "Return value [%llu]\n", *data));
 313
 314         return AE_OK;
 315 }
 316
 317 EXPORT_SYMBOL(acpi_evaluate_integer);
 318
 319 acpi_status
 320 acpi_evaluate_reference(acpi_handle handle,
 321                         acpi_string pathname,
 322                         struct acpi_object_list *arguments,
 323                         struct acpi_handle_list *list)
 324 {
 325         acpi_status status = AE_OK;
 326         union acpi_object *package = NULL;
 327         union acpi_object *element = NULL;
 328         struct acpi_buffer buffer = { ACPI_ALLOCATE_BUFFER, NULL };
 329         u32 i = 0;
 330
 331
 332         if (!list) {
 333                 return AE_BAD_PARAMETER;
 334         }
 335
 336         /* Evaluate object. */
 337
 338         status = acpi_evaluate_object(handle, pathname, arguments, &buffer);
 339         if (ACPI_FAILURE(status))
 340                 goto end;
 341
 342         package = buffer.pointer;
 343
 344         if ((buffer.length == 0) || !package) {
 345                 status = AE_BAD_DATA;
 346                 acpi_util_eval_error(handle, pathname, status);
 347                 goto end;
 348         }
 349         if (package->type != ACPI_TYPE_PACKAGE) {
 350                 status = AE_BAD_DATA;
 351                 acpi_util_eval_error(handle, pathname, status);
 352                 goto end;
 353         }
 354         if (!package->package.count) {
 355                 status = AE_BAD_DATA;
 356                 acpi_util_eval_error(handle, pathname, status);
 357                 goto end;
 358         }
 359
 360         if (package->package.count > ACPI_MAX_HANDLES) {
 361                 return AE_NO_MEMORY;
 362         }
 363         list->count = package->package.count;
 364
 365         /* Extract package data. */
 366
 367         for (i = 0; i < list->count; i++) {
 368
 369                 element = &(package->package.elements[i]);
 370
 371                 if (element->type != ACPI_TYPE_LOCAL_REFERENCE) {
 372                         status = AE_BAD_DATA;
 373                         acpi_util_eval_error(handle, pathname, status);
 374                         break;
 375                 }
 376
 377                 if (!element->reference.handle) {
 378                         status = AE_NULL_ENTRY;
 379                         acpi_util_eval_error(handle, pathname, status);
 380                         break;
 381                 }
 382                 /* Get the  acpi_handle. */
 383
 384                 list->handles[i] = element->reference.handle;
 385                 ACPI_DEBUG_PRINT((ACPI_DB_INFO, "Found reference [%p]\n",
 386                                   list->handles[i]));
 387         }
 388
 389       end:
 390         if (ACPI_FAILURE(status)) {
 391                 list->count = 0;
 392                 //kfree(list->handles);
 393         }
 394
 395         kfree(buffer.pointer);
 396
 397         return status;
 398 }
 399
 400 EXPORT_SYMBOL(acpi_evaluate_reference);
 401
 402 acpi_status
 403 acpi_get_physical_device_location(acpi_handle handle, struct acpi_pld_info **pld)
 404 {
 405         acpi_status status;
 406         struct acpi_buffer buffer = { ACPI_ALLOCATE_BUFFER, NULL };
 407         union acpi_object *output;
 408
 409         status = acpi_evaluate_object(handle, "_PLD", NULL, &buffer);
 410
 411         if (ACPI_FAILURE(status))
 412                 return status;
 413
 414         output = buffer.pointer;
 415
 416         if (!output || output->type != ACPI_TYPE_PACKAGE
 417             || !output->package.count
 418             || output->package.elements[0].type != ACPI_TYPE_BUFFER
 419             || output->package.elements[0].buffer.length < ACPI_PLD_REV1_BUFFER_SIZE) {
 420                 status = AE_TYPE;
 421                 goto out;
 422         }
 423
 424         status = acpi_decode_pld_buffer(
 425                         output->package.elements[0].buffer.pointer,
 426                         output->package.elements[0].buffer.length,
 427                         pld);
 428
 429 out:
 430         kfree(buffer.pointer);
 431         return status;
 432 }
 433 EXPORT_SYMBOL(acpi_get_physical_device_location);
 434
 435 /**
 436  * acpi_evaluate_ost: Evaluate _OST for hotplug operations
 437  * @handle: ACPI device handle
 438  * @source_event: source event code
 439  * @status_code: status code
 440  * @status_buf: optional detailed information (NULL if none)
 441  *
 442  * Evaluate _OST for hotplug operations. All ACPI hotplug handlers
 443  * must call this function when evaluating _OST for hotplug operations.
 444  * When the platform does not support _OST, this function has no effect.
 445  */
 446 acpi_status
 447 acpi_evaluate_ost(acpi_handle handle, u32 source_event, u32 status_code,
 448                   struct acpi_buffer *status_buf)
 449 {
 450         union acpi_object params[3] = {
 451                 {.type = ACPI_TYPE_INTEGER,},
 452                 {.type = ACPI_TYPE_INTEGER,},
 453                 {.type = ACPI_TYPE_BUFFER,}
 454         };
 455         struct acpi_object_list arg_list = {3, params};
 456
 457         params[0].integer.value = source_event;
 458         params[1].integer.value = status_code;
 459         if (status_buf != NULL) {
 460                 params[2].buffer.pointer = status_buf->pointer;
 461                 params[2].buffer.length = status_buf->length;
 462         } else {
 463                 params[2].buffer.pointer = NULL;
 464                 params[2].buffer.length = 0;
 465         }
 466
 467         return acpi_evaluate_object(handle, "_OST", &arg_list, NULL);
 468 }
 469 EXPORT_SYMBOL(acpi_evaluate_ost);
 470
 471 /**
 472  * acpi_handle_path: Return the object path of handle
 473  *
 474  * Caller must free the returned buffer
 475  */
 476 static char *acpi_handle_path(acpi_handle handle)
 477 {
 478         struct acpi_buffer buffer = {
 479                 .length = ACPI_ALLOCATE_BUFFER,
 480                 .pointer = NULL
 481         };
 482
 483         if (in_interrupt() ||
 484             acpi_get_name(handle, ACPI_FULL_PATHNAME, &buffer) != AE_OK)
 485                 return NULL;
 486         return buffer.pointer;
 487 }
 488
 489 /**
 490  * acpi_handle_printk: Print message with ACPI prefix and object path
 491  *
 492  * This function is called through acpi_handle_<level> macros and prints
 493  * a message with ACPI prefix and object path.  This function acquires
 494  * the global namespace mutex to obtain an object path.  In interrupt
 495  * context, it shows the object path as <n/a>.
 496  */
 497 void
 498 acpi_handle_printk(const char *level, acpi_handle handle, const char *fmt, ...)
 499 {
 500         struct va_format vaf;
 501         va_list args;
 502         const char *path;
 503
 504         va_start(args, fmt);
 505         vaf.fmt = fmt;
 506         vaf.va = &args;
 507
 508         path = acpi_handle_path(handle);
 509         printk("%sACPI: %s: %pV", level, path ? path : "<n/a>" , &vaf);
 510
 511         va_end(args);
 512         kfree(path);
 513 }
 514 EXPORT_SYMBOL(acpi_handle_printk);
 515
 516 #if defined(CONFIG_DYNAMIC_DEBUG)
 517 /**
 518  * __acpi_handle_debug: pr_debug with ACPI prefix and object path
 519  *
 520  * This function is called through acpi_handle_debug macro and debug
 521  * prints a message with ACPI prefix and object path. This function
 522  * acquires the global namespace mutex to obtain an object path.  In
 523  * interrupt context, it shows the object path as <n/a>.
 524  */
 525 void
 526 __acpi_handle_debug(struct _ddebug *descriptor, acpi_handle handle,
 527                     const char *fmt, ...)
 528 {
 529         struct va_format vaf;
 530         va_list args;
 531         const char *path;
 532
 533         va_start(args, fmt);
 534         vaf.fmt = fmt;
 535         vaf.va = &args;
 536
 537         path = acpi_handle_path(handle);
 538         __dynamic_pr_debug(descriptor, "ACPI: %s: %pV", path ? path : "<n/a>", &vaf);
 539
 540         va_end(args);
 541         kfree(path);
 542 }
 543 EXPORT_SYMBOL(__acpi_handle_debug);
 544 #endif
 545
 546 /**
 547  * acpi_has_method: Check whether @handle has a method named @name
 548  * @handle: ACPI device handle
 549  * @name: name of object or method
 550  *
 551  * Check whether @handle has a method named @name.
 552  */
 553 bool acpi_has_method(acpi_handle handle, char *name)
 554 {
 555         acpi_handle tmp;
 556
 557         return ACPI_SUCCESS(acpi_get_handle(handle, name, &tmp));
 558 }
 559 EXPORT_SYMBOL(acpi_has_method);
 560
 561 acpi_status acpi_execute_simple_method(acpi_handle handle, char *method,
 562                                        u64 arg)
 563 {
 564         union acpi_object obj = { .type = ACPI_TYPE_INTEGER };
 565         struct acpi_object_list arg_list = { .count = 1, .pointer = &obj, };
 566
 567         obj.integer.value = arg;
 568
 569         return acpi_evaluate_object(handle, method, &arg_list, NULL);
 570 }
 571 EXPORT_SYMBOL(acpi_execute_simple_method);
 572
 573 /**
 574  * acpi_evaluate_ej0: Evaluate _EJ0 method for hotplug operations
 575  * @handle: ACPI device handle
 576  *
 577  * Evaluate device's _EJ0 method for hotplug operations.
 578  */
 579 acpi_status acpi_evaluate_ej0(acpi_handle handle)
 580 {
 581         acpi_status status;
 582
 583         status = acpi_execute_simple_method(handle, "_EJ0", 1);
 584         if (status == AE_NOT_FOUND)
 585                 acpi_handle_warn(handle, "No _EJ0 support for device\n");
 586         else if (ACPI_FAILURE(status))
 587                 acpi_handle_warn(handle, "Eject failed (0x%x)\n", status);
 588
 589         return status;
 590 }
 591
 592 /**
 593  * acpi_evaluate_lck: Evaluate _LCK method to lock/unlock device
 594  * @handle: ACPI device handle
 595  * @lock: lock device if non-zero, otherwise unlock device
 596  *
 597  * Evaluate device's _LCK method if present to lock/unlock device
 598  */
 599 acpi_status acpi_evaluate_lck(acpi_handle handle, int lock)
 600 {
 601         acpi_status status;
 602
 603         status = acpi_execute_simple_method(handle, "_LCK", !!lock);
 604         if (ACPI_FAILURE(status) && status != AE_NOT_FOUND) {
 605                 if (lock)
 606                         acpi_handle_warn(handle,
 607                                 "Locking device failed (0x%x)\n", status);
 608                 else
 609                         acpi_handle_warn(handle,
 610                                 "Unlocking device failed (0x%x)\n", status);
 611         }
 612
 613         return status;
 614 }
 615
 616 /**
 617  * acpi_evaluate_dsm - evaluate device's _DSM method
 618  * @handle: ACPI device handle
 619  * @uuid: UUID of requested functions, should be 16 bytes
 620  * @rev: revision number of requested function
 621  * @func: requested function number
 622  * @argv4: the function specific parameter
 623  *
 624  * Evaluate device's _DSM method with specified UUID, revision id and
 625  * function number. Caller needs to free the returned object.
 626  *
 627  * Though ACPI defines the fourth parameter for _DSM should be a package,
 628  * some old BIOSes do expect a buffer or an integer etc.
 629  */
 630 union acpi_object *
 631 acpi_evaluate_dsm(acpi_handle handle, const u8 *uuid, int rev, int func,
 632                   union acpi_object *argv4)
 633 {
 634         acpi_status ret;
 635         struct acpi_buffer buf = {ACPI_ALLOCATE_BUFFER, NULL};
 636         union acpi_object params[4];
 637         struct acpi_object_list input = {
 638                 .count = 4,
 639                 .pointer = params,
 640         };
 641
 642         params[0].type = ACPI_TYPE_BUFFER;
 643         params[0].buffer.length = 16;
 644         params[0].buffer.pointer = (char *)uuid;
 645         params[1].type = ACPI_TYPE_INTEGER;
 646         params[1].integer.value = rev;
 647         params[2].type = ACPI_TYPE_INTEGER;
 648         params[2].integer.value = func;
 649         if (argv4) {
 650                 params[3] = *argv4;
 651         } else {
 652                 params[3].type = ACPI_TYPE_PACKAGE;
 653                 params[3].package.count = 0;
 654                 params[3].package.elements = NULL;
 655         }
 656
 657         ret = acpi_evaluate_object(handle, "_DSM", &input, &buf);
 658         if (ACPI_SUCCESS(ret))
 659                 return (union acpi_object *)buf.pointer;
 660
 661         if (ret != AE_NOT_FOUND)
 662                 acpi_handle_warn(handle,
 663                                 "failed to evaluate _DSM (0x%x)\n", ret);
 664
 665         return NULL;
 666 }
 667 EXPORT_SYMBOL(acpi_evaluate_dsm);
 668
 669 /**
 670  * acpi_check_dsm - check if _DSM method supports requested functions.
 671  * @handle: ACPI device handle
 672  * @uuid: UUID of requested functions, should be 16 bytes at least
 673  * @rev: revision number of requested functions
 674  * @funcs: bitmap of requested functions
 675  *
 676  * Evaluate device's _DSM method to check whether it supports requested
 677  * functions. Currently only support 64 functions at maximum, should be
 678  * enough for now.
 679  */
 680 bool acpi_check_dsm(acpi_handle handle, const u8 *uuid, int rev, u64 funcs)
 681 {
 682         int i;
 683         u64 mask = 0;
 684         union acpi_object *obj;
 685
 686         if (funcs == 0)
 687                 return false;
 688
 689         obj = acpi_evaluate_dsm(handle, uuid, rev, 0, NULL);
 690         if (!obj)
 691                 return false;
 692
 693         /* For compatibility, old BIOSes may return an integer */
 694         if (obj->type == ACPI_TYPE_INTEGER)
 695                 mask = obj->integer.value;
 696         else if (obj->type == ACPI_TYPE_BUFFER)
 697                 for (i = 0; i < obj->buffer.length && i < 8; i++)
 698                         mask |= (((u8)obj->buffer.pointer[i]) << (i * 8));
 699         ACPI_FREE(obj);
 700
 701         /*
 702          * Bit 0 indicates whether there's support for any functions other than
 703          * function 0 for the specified UUID and revision.
 704          */
 705         if ((mask & 0x1) && (mask & funcs) == funcs)
 706                 return true;
 707
 708         return false;
 709 }
 710 EXPORT_SYMBOL(acpi_check_dsm);
 711
 712 /*
 713  * acpi_backlight= handling, this is done here rather then in video_detect.c
 714  * because __setup cannot be used in modules.
 715  */
 716 char acpi_video_backlight_string[16];
 717 EXPORT_SYMBOL(acpi_video_backlight_string);
 718
 719 static int __init acpi_backlight(char *str)
 720 {
 721         strlcpy(acpi_video_backlight_string, str,
 722                 sizeof(acpi_video_backlight_string));
 723         return 1;
 724 }
 725 __setup("acpi_backlight=", acpi_backlight);