drivers/acpi/video_detect.c

   1 /*
   2  *  Copyright (C) 2015       Red Hat Inc.
   3  *                           Hans de Goede <hdegoede@redhat.com>
   4  *  Copyright (C) 2008       SuSE Linux Products GmbH
   5  *                           Thomas Renninger <trenn@suse.de>
   6  *
   7  *  May be copied or modified under the terms of the GNU General Public License
   8  *
   9  * video_detect.c:
  10  * After PCI devices are glued with ACPI devices
  11  * acpi_get_pci_dev() can be called to identify ACPI graphics
  12  * devices for which a real graphics card is plugged in
  13  *
  14  * Depending on whether ACPI graphics extensions (cmp. ACPI spec Appendix B)
  15  * are available, video.ko should be used to handle the device.
  16  *
  17  * Otherwise vendor specific drivers like thinkpad_acpi, asus-laptop,
  18  * sony_acpi,... can take care about backlight brightness.
  19  *
  20  * Backlight drivers can use acpi_video_get_backlight_type() to determine
  21  * which driver should handle the backlight.
  22  *
  23  * If CONFIG_ACPI_VIDEO is neither set as "compiled in" (y) nor as a module (m)
  24  * this file will not be compiled and acpi_video_get_backlight_type() will
  25  * always return acpi_backlight_vendor.
  26  */
  27
  28 #include <linux/export.h>
  29 #include <linux/acpi.h>
  30 #include <linux/backlight.h>
  31 #include <linux/dmi.h>
  32 #include <linux/module.h>
  33 #include <linux/pci.h>
  34 #include <linux/types.h>
  35 #include <linux/workqueue.h>
  36 #include <acpi/video.h>
  37
  38 void acpi_video_unregister_backlight(void);
  39
  40 static bool backlight_notifier_registered;
  41 static struct notifier_block backlight_nb;
  42 static struct work_struct backlight_notify_work;
  43
  44 static enum acpi_backlight_type acpi_backlight_cmdline = acpi_backlight_undef;
  45 static enum acpi_backlight_type acpi_backlight_dmi = acpi_backlight_undef;
  46
  47 static void acpi_video_parse_cmdline(void)
  48 {
  49         if (!strcmp("vendor", acpi_video_backlight_string))
  50                 acpi_backlight_cmdline = acpi_backlight_vendor;
  51         if (!strcmp("video", acpi_video_backlight_string))
  52                 acpi_backlight_cmdline = acpi_backlight_video;
  53         if (!strcmp("native", acpi_video_backlight_string))
  54                 acpi_backlight_cmdline = acpi_backlight_native;
  55         if (!strcmp("none", acpi_video_backlight_string))
  56                 acpi_backlight_cmdline = acpi_backlight_none;
  57 }
  58
  59 static acpi_status
  60 find_video(acpi_handle handle, u32 lvl, void *context, void **rv)
  61 {
  62         long *cap = context;
  63         struct pci_dev *dev;
  64         struct acpi_device *acpi_dev;
  65
  66         static const struct acpi_device_id video_ids[] = {
  67                 {ACPI_VIDEO_HID, 0},
  68                 {"", 0},
  69         };
  70         if (acpi_bus_get_device(handle, &acpi_dev))
  71                 return AE_OK;
  72
  73         if (!acpi_match_device_ids(acpi_dev, video_ids)) {
  74                 dev = acpi_get_pci_dev(handle);
  75                 if (!dev)
  76                         return AE_OK;
  77                 pci_dev_put(dev);
  78                 *cap |= acpi_is_video_device(handle);
  79         }
  80         return AE_OK;
  81 }
  82
  83 /* Force to use vendor driver when the ACPI device is known to be
  84  * buggy */
  85 static int video_detect_force_vendor(const struct dmi_system_id *d)
  86 {
  87         acpi_backlight_dmi = acpi_backlight_vendor;
  88         return 0;
  89 }
  90
  91 static int video_detect_force_video(const struct dmi_system_id *d)
  92 {
  93         acpi_backlight_dmi = acpi_backlight_video;
  94         return 0;
  95 }
  96
  97 static int video_detect_force_native(const struct dmi_system_id *d)
  98 {
  99         acpi_backlight_dmi = acpi_backlight_native;
 100         return 0;
 101 }
 102
 103 static int video_detect_force_none(const struct dmi_system_id *d)
 104 {
 105         acpi_backlight_dmi = acpi_backlight_none;
 106         return 0;
 107 }
 108
 109 static const struct dmi_system_id video_detect_dmi_table[] = {
 110         /* On Samsung X360, the BIOS will set a flag (VDRV) if generic
 111          * ACPI backlight device is used. This flag will definitively break
 112          * the backlight interface (even the vendor interface) until next
 113          * reboot. It's why we should prevent video.ko from being used here
 114          * and we can't rely on a later call to acpi_video_unregister().
 115          */
 116         {
 117          .callback = video_detect_force_vendor,
 118          .ident = "X360",
 119          .matches = {
 120                 DMI_MATCH(DMI_SYS_VENDOR, "SAMSUNG ELECTRONICS CO., LTD."),
 121                 DMI_MATCH(DMI_PRODUCT_NAME, "X360"),
 122                 DMI_MATCH(DMI_BOARD_NAME, "X360"),
 123                 },
 124         },
 125         {
 126         .callback = video_detect_force_vendor,
 127         .ident = "Asus UL30VT",
 128         .matches = {
 129                 DMI_MATCH(DMI_SYS_VENDOR, "ASUSTeK Computer Inc."),
 130                 DMI_MATCH(DMI_PRODUCT_NAME, "UL30VT"),
 131                 },
 132         },
 133         {
 134         .callback = video_detect_force_vendor,
 135         .ident = "Asus UL30A",
 136         .matches = {
 137                 DMI_MATCH(DMI_SYS_VENDOR, "ASUSTeK Computer Inc."),
 138                 DMI_MATCH(DMI_PRODUCT_NAME, "UL30A"),
 139                 },
 140         },
 141         {
 142         .callback = video_detect_force_vendor,
 143         .ident = "GIGABYTE GB-BXBT-2807",
 144         .matches = {
 145                 DMI_MATCH(DMI_SYS_VENDOR, "GIGABYTE"),
 146                 DMI_MATCH(DMI_PRODUCT_NAME, "GB-BXBT-2807"),
 147                 },
 148         },
 149         {
 150         .callback = video_detect_force_vendor,
 151         .ident = "Sony VPCEH3U1E",
 152         .matches = {
 153                 DMI_MATCH(DMI_SYS_VENDOR, "Sony Corporation"),
 154                 DMI_MATCH(DMI_PRODUCT_NAME, "VPCEH3U1E"),
 155                 },
 156         },
 157
 158         /*
 159          * These models have a working acpi_video backlight control, and using
 160          * native backlight causes a regression where backlight does not work
 161          * when userspace is not handling brightness key events. Disable
 162          * native_backlight on these to fix this:
 163          * https://bugzilla.kernel.org/show_bug.cgi?id=81691
 164          */
 165         {
 166          .callback = video_detect_force_video,
 167          .ident = "ThinkPad T420",
 168          .matches = {
 169                 DMI_MATCH(DMI_SYS_VENDOR, "LENOVO"),
 170                 DMI_MATCH(DMI_PRODUCT_VERSION, "ThinkPad T420"),
 171                 },
 172         },
 173         {
 174          .callback = video_detect_force_video,
 175          .ident = "ThinkPad T520",
 176          .matches = {
 177                 DMI_MATCH(DMI_SYS_VENDOR, "LENOVO"),
 178                 DMI_MATCH(DMI_PRODUCT_VERSION, "ThinkPad T520"),
 179                 },
 180         },
 181         {
 182          .callback = video_detect_force_video,
 183          .ident = "ThinkPad X201s",
 184          .matches = {
 185                 DMI_MATCH(DMI_SYS_VENDOR, "LENOVO"),
 186                 DMI_MATCH(DMI_PRODUCT_VERSION, "ThinkPad X201s"),
 187                 },
 188         },
 189         {
 190          .callback = video_detect_force_video,
 191          .ident = "ThinkPad X201T",
 192          .matches = {
 193                 DMI_MATCH(DMI_SYS_VENDOR, "LENOVO"),
 194                 DMI_MATCH(DMI_PRODUCT_VERSION, "ThinkPad X201T"),
 195                 },
 196         },
 197
 198         /* The native backlight controls do not work on some older machines */
 199         {
 200          /* https://bugs.freedesktop.org/show_bug.cgi?id=81515 */
 201          .callback = video_detect_force_video,
 202          .ident = "HP ENVY 15 Notebook",
 203          .matches = {
 204                 DMI_MATCH(DMI_SYS_VENDOR, "Hewlett-Packard"),
 205                 DMI_MATCH(DMI_PRODUCT_NAME, "HP ENVY 15 Notebook PC"),
 206                 },
 207         },
 208         {
 209          .callback = video_detect_force_video,
 210          .ident = "SAMSUNG 870Z5E/880Z5E/680Z5E",
 211          .matches = {
 212                 DMI_MATCH(DMI_SYS_VENDOR, "SAMSUNG ELECTRONICS CO., LTD."),
 213                 DMI_MATCH(DMI_PRODUCT_NAME, "870Z5E/880Z5E/680Z5E"),
 214                 },
 215         },
 216         {
 217          .callback = video_detect_force_video,
 218          .ident = "SAMSUNG 370R4E/370R4V/370R5E/3570RE/370R5V",
 219          .matches = {
 220                 DMI_MATCH(DMI_SYS_VENDOR, "SAMSUNG ELECTRONICS CO., LTD."),
 221                 DMI_MATCH(DMI_PRODUCT_NAME,
 222                           "370R4E/370R4V/370R5E/3570RE/370R5V"),
 223                 },
 224         },
 225         {
 226          /* https://bugzilla.redhat.com/show_bug.cgi?id=1186097 */
 227          .callback = video_detect_force_video,
 228          .ident = "SAMSUNG 3570R/370R/470R/450R/510R/4450RV",
 229          .matches = {
 230                 DMI_MATCH(DMI_SYS_VENDOR, "SAMSUNG ELECTRONICS CO., LTD."),
 231                 DMI_MATCH(DMI_PRODUCT_NAME,
 232                           "3570R/370R/470R/450R/510R/4450RV"),
 233                 },
 234         },
 235         {
 236          /* https://bugzilla.redhat.com/show_bug.cgi?id=1557060 */
 237          .callback = video_detect_force_video,
 238          .ident = "SAMSUNG 670Z5E",
 239          .matches = {
 240                 DMI_MATCH(DMI_SYS_VENDOR, "SAMSUNG ELECTRONICS CO., LTD."),
 241                 DMI_MATCH(DMI_PRODUCT_NAME, "670Z5E"),
 242                 },
 243         },
 244         {
 245          /* https://bugzilla.redhat.com/show_bug.cgi?id=1094948 */
 246          .callback = video_detect_force_video,
 247          .ident = "SAMSUNG 730U3E/740U3E",
 248          .matches = {
 249                 DMI_MATCH(DMI_SYS_VENDOR, "SAMSUNG ELECTRONICS CO., LTD."),
 250                 DMI_MATCH(DMI_PRODUCT_NAME, "730U3E/740U3E"),
 251                 },
 252         },
 253         {
 254          /* https://bugs.freedesktop.org/show_bug.cgi?id=87286 */
 255          .callback = video_detect_force_video,
 256          .ident = "SAMSUNG 900X3C/900X3D/900X3E/900X4C/900X4D",
 257          .matches = {
 258                 DMI_MATCH(DMI_SYS_VENDOR, "SAMSUNG ELECTRONICS CO., LTD."),
 259                 DMI_MATCH(DMI_PRODUCT_NAME,
 260                           "900X3C/900X3D/900X3E/900X4C/900X4D"),
 261                 },
 262         },
 263         {
 264          /* https://bugzilla.redhat.com/show_bug.cgi?id=1272633 */
 265          .callback = video_detect_force_video,
 266          .ident = "Dell XPS14 L421X",
 267          .matches = {
 268                 DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
 269                 DMI_MATCH(DMI_PRODUCT_NAME, "XPS L421X"),
 270                 },
 271         },
 272         {
 273          /* https://bugzilla.redhat.com/show_bug.cgi?id=1163574 */
 274          .callback = video_detect_force_video,
 275          .ident = "Dell XPS15 L521X",
 276          .matches = {
 277                 DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
 278                 DMI_MATCH(DMI_PRODUCT_NAME, "XPS L521X"),
 279                 },
 280         },
 281         {
 282          /* https://bugzilla.kernel.org/show_bug.cgi?id=108971 */
 283          .callback = video_detect_force_video,
 284          .ident = "SAMSUNG 530U4E/540U4E",
 285          .matches = {
 286                 DMI_MATCH(DMI_SYS_VENDOR, "SAMSUNG ELECTRONICS CO., LTD."),
 287                 DMI_MATCH(DMI_PRODUCT_NAME, "530U4E/540U4E"),
 288                 },
 289         },
 290         /* https://bugs.launchpad.net/bugs/1894667 */
 291         {
 292          .callback = video_detect_force_video,
 293          .ident = "HP 635 Notebook",
 294          .matches = {
 295                 DMI_MATCH(DMI_SYS_VENDOR, "Hewlett-Packard"),
 296                 DMI_MATCH(DMI_PRODUCT_NAME, "HP 635 Notebook PC"),
 297                 },
 298         },
 299
 300         /* Non win8 machines which need native backlight nevertheless */
 301         {
 302          /* https://bugzilla.redhat.com/show_bug.cgi?id=1201530 */
 303          .callback = video_detect_force_native,
 304          .ident = "Lenovo Ideapad S405",
 305          .matches = {
 306                 DMI_MATCH(DMI_SYS_VENDOR, "LENOVO"),
 307                 DMI_MATCH(DMI_BOARD_NAME, "Lenovo IdeaPad S405"),
 308                 },
 309         },
 310         {
 311          /* https://bugzilla.redhat.com/show_bug.cgi?id=1187004 */
 312          .callback = video_detect_force_native,
 313          .ident = "Lenovo Ideapad Z570",
 314          .matches = {
 315                 DMI_MATCH(DMI_SYS_VENDOR, "LENOVO"),
 316                 DMI_MATCH(DMI_PRODUCT_NAME, "102434U"),
 317                 },
 318         },
 319         {
 320          .callback = video_detect_force_native,
 321          .ident = "Lenovo E41-25",
 322          .matches = {
 323                 DMI_MATCH(DMI_SYS_VENDOR, "LENOVO"),
 324                 DMI_MATCH(DMI_PRODUCT_NAME, "81FS"),
 325                 },
 326         },
 327         {
 328          .callback = video_detect_force_native,
 329          .ident = "Lenovo E41-45",
 330          .matches = {
 331                 DMI_MATCH(DMI_SYS_VENDOR, "LENOVO"),
 332                 DMI_MATCH(DMI_PRODUCT_NAME, "82BK"),
 333                 },
 334         },
 335         {
 336          /* https://bugzilla.redhat.com/show_bug.cgi?id=1217249 */
 337          .callback = video_detect_force_native,
 338          .ident = "Apple MacBook Pro 12,1",
 339          .matches = {
 340                 DMI_MATCH(DMI_SYS_VENDOR, "Apple Inc."),
 341                 DMI_MATCH(DMI_PRODUCT_NAME, "MacBookPro12,1"),
 342                 },
 343         },
 344         {
 345          .callback = video_detect_force_native,
 346          .ident = "Dell Vostro V131",
 347          .matches = {
 348                 DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
 349                 DMI_MATCH(DMI_PRODUCT_NAME, "Vostro V131"),
 350                 },
 351         },
 352         {
 353          /* https://bugzilla.redhat.com/show_bug.cgi?id=1123661 */
 354          .callback = video_detect_force_native,
 355          .ident = "Dell XPS 17 L702X",
 356          .matches = {
 357                 DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
 358                 DMI_MATCH(DMI_PRODUCT_NAME, "Dell System XPS L702X"),
 359                 },
 360         },
 361         {
 362          .callback = video_detect_force_native,
 363          .ident = "Dell Precision 7510",
 364          .matches = {
 365                 DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
 366                 DMI_MATCH(DMI_PRODUCT_NAME, "Precision 7510"),
 367                 },
 368         },
 369         {
 370          .callback = video_detect_force_native,
 371          .ident = "Acer Aspire 5738z",
 372          .matches = {
 373                 DMI_MATCH(DMI_SYS_VENDOR, "Acer"),
 374                 DMI_MATCH(DMI_PRODUCT_NAME, "Aspire 5738"),
 375                 DMI_MATCH(DMI_BOARD_NAME, "JV50"),
 376                 },
 377         },
 378         {
 379          /* https://bugzilla.kernel.org/show_bug.cgi?id=207835 */
 380          .callback = video_detect_force_native,
 381          .ident = "Acer TravelMate 5735Z",
 382          .matches = {
 383                 DMI_MATCH(DMI_SYS_VENDOR, "Acer"),
 384                 DMI_MATCH(DMI_PRODUCT_NAME, "TravelMate 5735Z"),
 385                 DMI_MATCH(DMI_BOARD_NAME, "BA51_MV"),
 386                 },
 387         },
 388         {
 389         .callback = video_detect_force_native,
 390         .ident = "ASUSTeK COMPUTER INC. GA401",
 391         .matches = {
 392                 DMI_MATCH(DMI_SYS_VENDOR, "ASUSTeK COMPUTER INC."),
 393                 DMI_MATCH(DMI_PRODUCT_NAME, "GA401"),
 394                 },
 395         },
 396         {
 397         .callback = video_detect_force_native,
 398         .ident = "ASUSTeK COMPUTER INC. GA502",
 399         .matches = {
 400                 DMI_MATCH(DMI_SYS_VENDOR, "ASUSTeK COMPUTER INC."),
 401                 DMI_MATCH(DMI_PRODUCT_NAME, "GA502"),
 402                 },
 403         },
 404         {
 405         .callback = video_detect_force_native,
 406         .ident = "ASUSTeK COMPUTER INC. GA503",
 407         .matches = {
 408                 DMI_MATCH(DMI_SYS_VENDOR, "ASUSTeK COMPUTER INC."),
 409                 DMI_MATCH(DMI_PRODUCT_NAME, "GA503"),
 410                 },
 411         },
 412         /*
 413          * Clevo NL5xRU and NL5xNU/TUXEDO Aura 15 Gen1 and Gen2 have both a
 414          * working native and video interface. However the default detection
 415          * mechanism first registers the video interface before unregistering
 416          * it again and switching to the native interface during boot. This
 417          * results in a dangling SBIOS request for backlight change for some
 418          * reason, causing the backlight to switch to ~2% once per boot on the
 419          * first power cord connect or disconnect event. Setting the native
 420          * interface explicitly circumvents this buggy behaviour, by avoiding
 421          * the unregistering process.
 422          */
 423         {
 424         .callback = video_detect_force_native,
 425         .ident = "Clevo NL5xRU",
 426         .matches = {
 427                 DMI_MATCH(DMI_BOARD_NAME, "NL5xRU"),
 428                 },
 429         },
 430         {
 431         .callback = video_detect_force_native,
 432         .ident = "Clevo NL5xRU",
 433         .matches = {
 434                 DMI_MATCH(DMI_SYS_VENDOR, "TUXEDO"),
 435                 DMI_MATCH(DMI_BOARD_NAME, "AURA1501"),
 436                 },
 437         },
 438         {
 439         .callback = video_detect_force_native,
 440         .ident = "Clevo NL5xRU",
 441         .matches = {
 442                 DMI_MATCH(DMI_SYS_VENDOR, "TUXEDO"),
 443                 DMI_MATCH(DMI_BOARD_NAME, "EDUBOOK1502"),
 444                 },
 445         },
 446         {
 447         .callback = video_detect_force_native,
 448         .ident = "Clevo NL5xNU",
 449         .matches = {
 450                 DMI_MATCH(DMI_BOARD_NAME, "NL5xNU"),
 451                 },
 452         },
 453         /*
 454          * The TongFang PF5PU1G, PF4NU1F, PF5NU1G, and PF5LUXG/TUXEDO BA15 Gen10,
 455          * Pulse 14/15 Gen1, and Pulse 15 Gen2 have the same problem as the Clevo
 456          * NL5xRU and NL5xNU/TUXEDO Aura 15 Gen1 and Gen2. See the description
 457          * above.
 458          */
 459         {
 460         .callback = video_detect_force_native,
 461         .ident = "TongFang PF5PU1G",
 462         .matches = {
 463                 DMI_MATCH(DMI_BOARD_NAME, "PF5PU1G"),
 464                 },
 465         },
 466         {
 467         .callback = video_detect_force_native,
 468         .ident = "TongFang PF4NU1F",
 469         .matches = {
 470                 DMI_MATCH(DMI_BOARD_NAME, "PF4NU1F"),
 471                 },
 472         },
 473         {
 474         .callback = video_detect_force_native,
 475         .ident = "TongFang PF4NU1F",
 476         .matches = {
 477                 DMI_MATCH(DMI_SYS_VENDOR, "TUXEDO"),
 478                 DMI_MATCH(DMI_BOARD_NAME, "PULSE1401"),
 479                 },
 480         },
 481         {
 482         .callback = video_detect_force_native,
 483         .ident = "TongFang PF5NU1G",
 484         .matches = {
 485                 DMI_MATCH(DMI_BOARD_NAME, "PF5NU1G"),
 486                 },
 487         },
 488         {
 489         .callback = video_detect_force_native,
 490         .ident = "TongFang PF5NU1G",
 491         .matches = {
 492                 DMI_MATCH(DMI_SYS_VENDOR, "TUXEDO"),
 493                 DMI_MATCH(DMI_BOARD_NAME, "PULSE1501"),
 494                 },
 495         },
 496         {
 497         .callback = video_detect_force_native,
 498         .ident = "TongFang PF5LUXG",
 499         .matches = {
 500                 DMI_MATCH(DMI_BOARD_NAME, "PF5LUXG"),
 501                 },
 502         },
 503         /*
 504          * Desktops which falsely report a backlight and which our heuristics
 505          * for this do not catch.
 506          */
 507         {
 508          .callback = video_detect_force_none,
 509          .ident = "Dell OptiPlex 9020M",
 510          .matches = {
 511                 DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
 512                 DMI_MATCH(DMI_PRODUCT_NAME, "OptiPlex 9020M"),
 513                 },
 514         },
 515         {
 516          .callback = video_detect_force_none,
 517          .ident = "MSI MS-7721",
 518          .matches = {
 519                 DMI_MATCH(DMI_SYS_VENDOR, "MSI"),
 520                 DMI_MATCH(DMI_PRODUCT_NAME, "MS-7721"),
 521                 },
 522         },
 523         { },
 524 };
 525
 526 /* This uses a workqueue to avoid various locking ordering issues */
 527 static void acpi_video_backlight_notify_work(struct work_struct *work)
 528 {
 529         if (acpi_video_get_backlight_type() != acpi_backlight_video)
 530                 acpi_video_unregister_backlight();
 531 }
 532
 533 static int acpi_video_backlight_notify(struct notifier_block *nb,
 534                                        unsigned long val, void *bd)
 535 {
 536         struct backlight_device *backlight = bd;
 537
 538         /* A raw bl registering may change video -> native */
 539         if (backlight->props.type == BACKLIGHT_RAW &&
 540             val == BACKLIGHT_REGISTERED)
 541                 schedule_work(&backlight_notify_work);
 542
 543         return NOTIFY_OK;
 544 }
 545
 546 /*
 547  * Determine which type of backlight interface to use on this system,
 548  * First check cmdline, then dmi quirks, then do autodetect.
 549  *
 550  * The autodetect order is:
 551  * 1) Is the acpi-video backlight interface supported ->
 552  *  no, use a vendor interface
 553  * 2) Is this a win8 "ready" BIOS and do we have a native interface ->
 554  *  yes, use a native interface
 555  * 3) Else use the acpi-video interface
 556  *
 557  * Arguably the native on win8 check should be done first, but that would
 558  * be a behavior change, which may causes issues.
 559  */
 560 enum acpi_backlight_type acpi_video_get_backlight_type(void)
 561 {
 562         static DEFINE_MUTEX(init_mutex);
 563         static bool init_done;
 564         static long video_caps;
 565
 566         /* Parse cmdline, dmi and acpi only once */
 567         mutex_lock(&init_mutex);
 568         if (!init_done) {
 569                 acpi_video_parse_cmdline();
 570                 dmi_check_system(video_detect_dmi_table);
 571                 acpi_walk_namespace(ACPI_TYPE_DEVICE, ACPI_ROOT_OBJECT,
 572                                     ACPI_UINT32_MAX, find_video, NULL,
 573                                     &video_caps, NULL);
 574                 INIT_WORK(&backlight_notify_work,
 575                           acpi_video_backlight_notify_work);
 576                 backlight_nb.notifier_call = acpi_video_backlight_notify;
 577                 backlight_nb.priority = 0;
 578                 if (backlight_register_notifier(&backlight_nb) == 0)
 579                         backlight_notifier_registered = true;
 580                 init_done = true;
 581         }
 582         mutex_unlock(&init_mutex);
 583
 584         if (acpi_backlight_cmdline != acpi_backlight_undef)
 585                 return acpi_backlight_cmdline;
 586
 587         if (acpi_backlight_dmi != acpi_backlight_undef)
 588                 return acpi_backlight_dmi;
 589
 590         if (!(video_caps & ACPI_VIDEO_BACKLIGHT))
 591                 return acpi_backlight_vendor;
 592
 593         if (acpi_osi_is_win8() && backlight_device_get_by_type(BACKLIGHT_RAW))
 594                 return acpi_backlight_native;
 595
 596         return acpi_backlight_video;
 597 }
 598 EXPORT_SYMBOL(acpi_video_get_backlight_type);
 599
 600 /*
 601  * Set the preferred backlight interface type based on DMI info.
 602  * This function allows DMI blacklists to be implemented by external
 603  * platform drivers instead of putting a big blacklist in video_detect.c
 604  */
 605 void acpi_video_set_dmi_backlight_type(enum acpi_backlight_type type)
 606 {
 607         acpi_backlight_dmi = type;
 608         /* Remove acpi-video backlight interface if it is no longer desired */
 609         if (acpi_video_get_backlight_type() != acpi_backlight_video)
 610                 acpi_video_unregister_backlight();
 611 }
 612 EXPORT_SYMBOL(acpi_video_set_dmi_backlight_type);
 613
 614 void __exit acpi_video_detect_exit(void)
 615 {
 616         if (backlight_notifier_registered)
 617                 backlight_unregister_notifier(&backlight_nb);
 618 }