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 ACPI_MODULE_NAME("video");
  39 #define _COMPONENT              ACPI_VIDEO_COMPONENT
  40
  41 void acpi_video_unregister_backlight(void);
  42
  43 static bool backlight_notifier_registered;
  44 static struct notifier_block backlight_nb;
  45 static struct work_struct backlight_notify_work;
  46
  47 static enum acpi_backlight_type acpi_backlight_cmdline = acpi_backlight_undef;
  48 static enum acpi_backlight_type acpi_backlight_dmi = acpi_backlight_undef;
  49
  50 static void acpi_video_parse_cmdline(void)
  51 {
  52         if (!strcmp("vendor", acpi_video_backlight_string))
  53                 acpi_backlight_cmdline = acpi_backlight_vendor;
  54         if (!strcmp("video", acpi_video_backlight_string))
  55                 acpi_backlight_cmdline = acpi_backlight_video;
  56         if (!strcmp("native", acpi_video_backlight_string))
  57                 acpi_backlight_cmdline = acpi_backlight_native;
  58         if (!strcmp("none", acpi_video_backlight_string))
  59                 acpi_backlight_cmdline = acpi_backlight_none;
  60 }
  61
  62 static acpi_status
  63 find_video(acpi_handle handle, u32 lvl, void *context, void **rv)
  64 {
  65         long *cap = context;
  66         struct pci_dev *dev;
  67         struct acpi_device *acpi_dev;
  68
  69         static const struct acpi_device_id video_ids[] = {
  70                 {ACPI_VIDEO_HID, 0},
  71                 {"", 0},
  72         };
  73         if (acpi_bus_get_device(handle, &acpi_dev))
  74                 return AE_OK;
  75
  76         if (!acpi_match_device_ids(acpi_dev, video_ids)) {
  77                 dev = acpi_get_pci_dev(handle);
  78                 if (!dev)
  79                         return AE_OK;
  80                 pci_dev_put(dev);
  81                 *cap |= acpi_is_video_device(handle);
  82         }
  83         return AE_OK;
  84 }
  85
  86 /* Force to use vendor driver when the ACPI device is known to be
  87  * buggy */
  88 static int video_detect_force_vendor(const struct dmi_system_id *d)
  89 {
  90         acpi_backlight_dmi = acpi_backlight_vendor;
  91         return 0;
  92 }
  93
  94 static int video_detect_force_video(const struct dmi_system_id *d)
  95 {
  96         acpi_backlight_dmi = acpi_backlight_video;
  97         return 0;
  98 }
  99
 100 static int video_detect_force_native(const struct dmi_system_id *d)
 101 {
 102         acpi_backlight_dmi = acpi_backlight_native;
 103         return 0;
 104 }
 105
 106 static int video_detect_force_none(const struct dmi_system_id *d)
 107 {
 108         acpi_backlight_dmi = acpi_backlight_none;
 109         return 0;
 110 }
 111
 112 static const struct dmi_system_id video_detect_dmi_table[] = {
 113         /* On Samsung X360, the BIOS will set a flag (VDRV) if generic
 114          * ACPI backlight device is used. This flag will definitively break
 115          * the backlight interface (even the vendor interface) untill next
 116          * reboot. It's why we should prevent video.ko from being used here
 117          * and we can't rely on a later call to acpi_video_unregister().
 118          */
 119         {
 120          .callback = video_detect_force_vendor,
 121          .ident = "X360",
 122          .matches = {
 123                 DMI_MATCH(DMI_SYS_VENDOR, "SAMSUNG ELECTRONICS CO., LTD."),
 124                 DMI_MATCH(DMI_PRODUCT_NAME, "X360"),
 125                 DMI_MATCH(DMI_BOARD_NAME, "X360"),
 126                 },
 127         },
 128         {
 129         .callback = video_detect_force_vendor,
 130         .ident = "Asus UL30VT",
 131         .matches = {
 132                 DMI_MATCH(DMI_SYS_VENDOR, "ASUSTeK Computer Inc."),
 133                 DMI_MATCH(DMI_PRODUCT_NAME, "UL30VT"),
 134                 },
 135         },
 136         {
 137         .callback = video_detect_force_vendor,
 138         .ident = "Asus UL30A",
 139         .matches = {
 140                 DMI_MATCH(DMI_SYS_VENDOR, "ASUSTeK Computer Inc."),
 141                 DMI_MATCH(DMI_PRODUCT_NAME, "UL30A"),
 142                 },
 143         },
 144
 145         /*
 146          * These models have a working acpi_video backlight control, and using
 147          * native backlight causes a regression where backlight does not work
 148          * when userspace is not handling brightness key events. Disable
 149          * native_backlight on these to fix this:
 150          * https://bugzilla.kernel.org/show_bug.cgi?id=81691
 151          */
 152         {
 153          .callback = video_detect_force_video,
 154          .ident = "ThinkPad T420",
 155          .matches = {
 156                 DMI_MATCH(DMI_SYS_VENDOR, "LENOVO"),
 157                 DMI_MATCH(DMI_PRODUCT_VERSION, "ThinkPad T420"),
 158                 },
 159         },
 160         {
 161          .callback = video_detect_force_video,
 162          .ident = "ThinkPad T520",
 163          .matches = {
 164                 DMI_MATCH(DMI_SYS_VENDOR, "LENOVO"),
 165                 DMI_MATCH(DMI_PRODUCT_VERSION, "ThinkPad T520"),
 166                 },
 167         },
 168         {
 169          .callback = video_detect_force_video,
 170          .ident = "ThinkPad X201s",
 171          .matches = {
 172                 DMI_MATCH(DMI_SYS_VENDOR, "LENOVO"),
 173                 DMI_MATCH(DMI_PRODUCT_VERSION, "ThinkPad X201s"),
 174                 },
 175         },
 176         {
 177          .callback = video_detect_force_video,
 178          .ident = "ThinkPad X201T",
 179          .matches = {
 180                 DMI_MATCH(DMI_SYS_VENDOR, "LENOVO"),
 181                 DMI_MATCH(DMI_PRODUCT_VERSION, "ThinkPad X201T"),
 182                 },
 183         },
 184
 185         /* The native backlight controls do not work on some older machines */
 186         {
 187          /* https://bugs.freedesktop.org/show_bug.cgi?id=81515 */
 188          .callback = video_detect_force_video,
 189          .ident = "HP ENVY 15 Notebook",
 190          .matches = {
 191                 DMI_MATCH(DMI_SYS_VENDOR, "Hewlett-Packard"),
 192                 DMI_MATCH(DMI_PRODUCT_NAME, "HP ENVY 15 Notebook PC"),
 193                 },
 194         },
 195         {
 196          .callback = video_detect_force_video,
 197          .ident = "SAMSUNG 870Z5E/880Z5E/680Z5E",
 198          .matches = {
 199                 DMI_MATCH(DMI_SYS_VENDOR, "SAMSUNG ELECTRONICS CO., LTD."),
 200                 DMI_MATCH(DMI_PRODUCT_NAME, "870Z5E/880Z5E/680Z5E"),
 201                 },
 202         },
 203         {
 204          .callback = video_detect_force_video,
 205          .ident = "SAMSUNG 370R4E/370R4V/370R5E/3570RE/370R5V",
 206          .matches = {
 207                 DMI_MATCH(DMI_SYS_VENDOR, "SAMSUNG ELECTRONICS CO., LTD."),
 208                 DMI_MATCH(DMI_PRODUCT_NAME,
 209                           "370R4E/370R4V/370R5E/3570RE/370R5V"),
 210                 },
 211         },
 212         {
 213          /* https://bugzilla.redhat.com/show_bug.cgi?id=1186097 */
 214          .callback = video_detect_force_video,
 215          .ident = "SAMSUNG 3570R/370R/470R/450R/510R/4450RV",
 216          .matches = {
 217                 DMI_MATCH(DMI_SYS_VENDOR, "SAMSUNG ELECTRONICS CO., LTD."),
 218                 DMI_MATCH(DMI_PRODUCT_NAME,
 219                           "3570R/370R/470R/450R/510R/4450RV"),
 220                 },
 221         },
 222         {
 223          /* https://bugzilla.redhat.com/show_bug.cgi?id=1557060 */
 224          .callback = video_detect_force_video,
 225          .ident = "SAMSUNG 670Z5E",
 226          .matches = {
 227                 DMI_MATCH(DMI_SYS_VENDOR, "SAMSUNG ELECTRONICS CO., LTD."),
 228                 DMI_MATCH(DMI_PRODUCT_NAME, "670Z5E"),
 229                 },
 230         },
 231         {
 232          /* https://bugzilla.redhat.com/show_bug.cgi?id=1094948 */
 233          .callback = video_detect_force_video,
 234          .ident = "SAMSUNG 730U3E/740U3E",
 235          .matches = {
 236                 DMI_MATCH(DMI_SYS_VENDOR, "SAMSUNG ELECTRONICS CO., LTD."),
 237                 DMI_MATCH(DMI_PRODUCT_NAME, "730U3E/740U3E"),
 238                 },
 239         },
 240         {
 241          /* https://bugs.freedesktop.org/show_bug.cgi?id=87286 */
 242          .callback = video_detect_force_video,
 243          .ident = "SAMSUNG 900X3C/900X3D/900X3E/900X4C/900X4D",
 244          .matches = {
 245                 DMI_MATCH(DMI_SYS_VENDOR, "SAMSUNG ELECTRONICS CO., LTD."),
 246                 DMI_MATCH(DMI_PRODUCT_NAME,
 247                           "900X3C/900X3D/900X3E/900X4C/900X4D"),
 248                 },
 249         },
 250         {
 251          /* https://bugzilla.redhat.com/show_bug.cgi?id=1272633 */
 252          .callback = video_detect_force_video,
 253          .ident = "Dell XPS14 L421X",
 254          .matches = {
 255                 DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
 256                 DMI_MATCH(DMI_PRODUCT_NAME, "XPS L421X"),
 257                 },
 258         },
 259         {
 260          /* https://bugzilla.redhat.com/show_bug.cgi?id=1163574 */
 261          .callback = video_detect_force_video,
 262          .ident = "Dell XPS15 L521X",
 263          .matches = {
 264                 DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
 265                 DMI_MATCH(DMI_PRODUCT_NAME, "XPS L521X"),
 266                 },
 267         },
 268         {
 269          /* https://bugzilla.kernel.org/show_bug.cgi?id=108971 */
 270          .callback = video_detect_force_video,
 271          .ident = "SAMSUNG 530U4E/540U4E",
 272          .matches = {
 273                 DMI_MATCH(DMI_SYS_VENDOR, "SAMSUNG ELECTRONICS CO., LTD."),
 274                 DMI_MATCH(DMI_PRODUCT_NAME, "530U4E/540U4E"),
 275                 },
 276         },
 277         /* https://bugs.launchpad.net/bugs/1894667 */
 278         {
 279          .callback = video_detect_force_video,
 280          .ident = "HP 635 Notebook",
 281          .matches = {
 282                 DMI_MATCH(DMI_SYS_VENDOR, "Hewlett-Packard"),
 283                 DMI_MATCH(DMI_PRODUCT_NAME, "HP 635 Notebook PC"),
 284                 },
 285         },
 286
 287         /* Non win8 machines which need native backlight nevertheless */
 288         {
 289          /* https://bugzilla.redhat.com/show_bug.cgi?id=1201530 */
 290          .callback = video_detect_force_native,
 291          .ident = "Lenovo Ideapad S405",
 292          .matches = {
 293                 DMI_MATCH(DMI_SYS_VENDOR, "LENOVO"),
 294                 DMI_MATCH(DMI_BOARD_NAME, "Lenovo IdeaPad S405"),
 295                 },
 296         },
 297         {
 298          /* https://bugzilla.suse.com/show_bug.cgi?id=1208724 */
 299          .callback = video_detect_force_native,
 300          /* Lenovo Ideapad Z470 */
 301          .matches = {
 302                 DMI_MATCH(DMI_SYS_VENDOR, "LENOVO"),
 303                 DMI_MATCH(DMI_PRODUCT_VERSION, "IdeaPad Z470"),
 304                 },
 305         },
 306         {
 307          /* https://bugzilla.redhat.com/show_bug.cgi?id=1187004 */
 308          .callback = video_detect_force_native,
 309          .ident = "Lenovo Ideapad Z570",
 310          .matches = {
 311                 DMI_MATCH(DMI_SYS_VENDOR, "LENOVO"),
 312                 DMI_MATCH(DMI_PRODUCT_VERSION, "Ideapad Z570"),
 313                 },
 314         },
 315         {
 316          /* https://bugzilla.redhat.com/show_bug.cgi?id=1217249 */
 317          .callback = video_detect_force_native,
 318          .ident = "Apple MacBook Pro 12,1",
 319          .matches = {
 320                 DMI_MATCH(DMI_SYS_VENDOR, "Apple Inc."),
 321                 DMI_MATCH(DMI_PRODUCT_NAME, "MacBookPro12,1"),
 322                 },
 323         },
 324         {
 325          .callback = video_detect_force_native,
 326          .ident = "Dell Vostro V131",
 327          .matches = {
 328                 DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
 329                 DMI_MATCH(DMI_PRODUCT_NAME, "Vostro V131"),
 330                 },
 331         },
 332         {
 333          /* https://bugzilla.redhat.com/show_bug.cgi?id=1123661 */
 334          .callback = video_detect_force_native,
 335          .ident = "Dell XPS 17 L702X",
 336          .matches = {
 337                 DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
 338                 DMI_MATCH(DMI_PRODUCT_NAME, "Dell System XPS L702X"),
 339                 },
 340         },
 341         {
 342          .callback = video_detect_force_native,
 343          .ident = "Dell Precision 7510",
 344          .matches = {
 345                 DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
 346                 DMI_MATCH(DMI_PRODUCT_NAME, "Precision 7510"),
 347                 },
 348         },
 349         {
 350          .callback = video_detect_force_native,
 351          .ident = "Acer Aspire 5738z",
 352          .matches = {
 353                 DMI_MATCH(DMI_SYS_VENDOR, "Acer"),
 354                 DMI_MATCH(DMI_PRODUCT_NAME, "Aspire 5738"),
 355                 DMI_MATCH(DMI_BOARD_NAME, "JV50"),
 356                 },
 357         },
 358         {
 359          /* https://bugzilla.kernel.org/show_bug.cgi?id=207835 */
 360          .callback = video_detect_force_native,
 361          .ident = "Acer TravelMate 5735Z",
 362          .matches = {
 363                 DMI_MATCH(DMI_SYS_VENDOR, "Acer"),
 364                 DMI_MATCH(DMI_PRODUCT_NAME, "TravelMate 5735Z"),
 365                 DMI_MATCH(DMI_BOARD_NAME, "BA51_MV"),
 366                 },
 367         },
 368         /*
 369          * Clevo NL5xRU and NL5xNU/TUXEDO Aura 15 Gen1 and Gen2 have both a
 370          * working native and video interface. However the default detection
 371          * mechanism first registers the video interface before unregistering
 372          * it again and switching to the native interface during boot. This
 373          * results in a dangling SBIOS request for backlight change for some
 374          * reason, causing the backlight to switch to ~2% once per boot on the
 375          * first power cord connect or disconnect event. Setting the native
 376          * interface explicitly circumvents this buggy behaviour, by avoiding
 377          * the unregistering process.
 378          */
 379         {
 380         .callback = video_detect_force_native,
 381         .ident = "Clevo NL5xRU",
 382         .matches = {
 383                 DMI_MATCH(DMI_BOARD_NAME, "NL5xRU"),
 384                 },
 385         },
 386         {
 387         .callback = video_detect_force_native,
 388         .ident = "Clevo NL5xRU",
 389         .matches = {
 390                 DMI_MATCH(DMI_SYS_VENDOR, "TUXEDO"),
 391                 DMI_MATCH(DMI_BOARD_NAME, "AURA1501"),
 392                 },
 393         },
 394         {
 395         .callback = video_detect_force_native,
 396         .ident = "Clevo NL5xRU",
 397         .matches = {
 398                 DMI_MATCH(DMI_SYS_VENDOR, "TUXEDO"),
 399                 DMI_MATCH(DMI_BOARD_NAME, "EDUBOOK1502"),
 400                 },
 401         },
 402         {
 403         .callback = video_detect_force_native,
 404         .ident = "Clevo NL5xNU",
 405         .matches = {
 406                 DMI_MATCH(DMI_BOARD_NAME, "NL5xNU"),
 407                 },
 408         },
 409         /*
 410          * The TongFang PF5PU1G, PF4NU1F, PF5NU1G, and PF5LUXG/TUXEDO BA15 Gen10,
 411          * Pulse 14/15 Gen1, and Pulse 15 Gen2 have the same problem as the Clevo
 412          * NL5xRU and NL5xNU/TUXEDO Aura 15 Gen1 and Gen2. See the description
 413          * above.
 414          */
 415         {
 416         .callback = video_detect_force_native,
 417         .ident = "TongFang PF5PU1G",
 418         .matches = {
 419                 DMI_MATCH(DMI_BOARD_NAME, "PF5PU1G"),
 420                 },
 421         },
 422         {
 423         .callback = video_detect_force_native,
 424         .ident = "TongFang PF4NU1F",
 425         .matches = {
 426                 DMI_MATCH(DMI_BOARD_NAME, "PF4NU1F"),
 427                 },
 428         },
 429         {
 430         .callback = video_detect_force_native,
 431         .ident = "TongFang PF4NU1F",
 432         .matches = {
 433                 DMI_MATCH(DMI_SYS_VENDOR, "TUXEDO"),
 434                 DMI_MATCH(DMI_BOARD_NAME, "PULSE1401"),
 435                 },
 436         },
 437         {
 438         .callback = video_detect_force_native,
 439         .ident = "TongFang PF5NU1G",
 440         .matches = {
 441                 DMI_MATCH(DMI_BOARD_NAME, "PF5NU1G"),
 442                 },
 443         },
 444         {
 445         .callback = video_detect_force_native,
 446         .ident = "TongFang PF5NU1G",
 447         .matches = {
 448                 DMI_MATCH(DMI_SYS_VENDOR, "TUXEDO"),
 449                 DMI_MATCH(DMI_BOARD_NAME, "PULSE1501"),
 450                 },
 451         },
 452         {
 453         .callback = video_detect_force_native,
 454         .ident = "TongFang PF5LUXG",
 455         .matches = {
 456                 DMI_MATCH(DMI_BOARD_NAME, "PF5LUXG"),
 457                 },
 458         },
 459         /*
 460          * More Tongfang devices with the same issue as the Clevo NL5xRU and
 461          * NL5xNU/TUXEDO Aura 15 Gen1 and Gen2. See the description above.
 462          */
 463         {
 464         .callback = video_detect_force_native,
 465         .ident = "TongFang GKxNRxx",
 466         .matches = {
 467                 DMI_MATCH(DMI_BOARD_NAME, "GKxNRxx"),
 468                 },
 469         },
 470         {
 471         .callback = video_detect_force_native,
 472         .ident = "TongFang GKxNRxx",
 473         .matches = {
 474                 DMI_MATCH(DMI_SYS_VENDOR, "TUXEDO"),
 475                 DMI_MATCH(DMI_BOARD_NAME, "POLARIS1501A1650TI"),
 476                 },
 477         },
 478         {
 479         .callback = video_detect_force_native,
 480         .ident = "TongFang GKxNRxx",
 481         .matches = {
 482                 DMI_MATCH(DMI_SYS_VENDOR, "TUXEDO"),
 483                 DMI_MATCH(DMI_BOARD_NAME, "POLARIS1501A2060"),
 484                 },
 485         },
 486         {
 487         .callback = video_detect_force_native,
 488         .ident = "TongFang GKxNRxx",
 489         .matches = {
 490                 DMI_MATCH(DMI_SYS_VENDOR, "TUXEDO"),
 491                 DMI_MATCH(DMI_BOARD_NAME, "POLARIS1701A1650TI"),
 492                 },
 493         },
 494         {
 495         .callback = video_detect_force_native,
 496         .ident = "TongFang GKxNRxx",
 497         .matches = {
 498                 DMI_MATCH(DMI_SYS_VENDOR, "TUXEDO"),
 499                 DMI_MATCH(DMI_BOARD_NAME, "POLARIS1701A2060"),
 500                 },
 501         },
 502         {
 503         .callback = video_detect_force_native,
 504         .ident = "TongFang GMxNGxx",
 505         .matches = {
 506                 DMI_MATCH(DMI_BOARD_NAME, "GMxNGxx"),
 507                 },
 508         },
 509         {
 510         .callback = video_detect_force_native,
 511         .ident = "TongFang GMxZGxx",
 512         .matches = {
 513                 DMI_MATCH(DMI_BOARD_NAME, "GMxZGxx"),
 514                 },
 515         },
 516         {
 517         .callback = video_detect_force_native,
 518         .ident = "TongFang GMxRGxx",
 519         .matches = {
 520                 DMI_MATCH(DMI_BOARD_NAME, "GMxRGxx"),
 521                 },
 522         },
 523         /*
 524          * Desktops which falsely report a backlight and which our heuristics
 525          * for this do not catch.
 526          */
 527         {
 528          .callback = video_detect_force_none,
 529          .ident = "Dell OptiPlex 9020M",
 530          .matches = {
 531                 DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
 532                 DMI_MATCH(DMI_PRODUCT_NAME, "OptiPlex 9020M"),
 533                 },
 534         },
 535         {
 536          .callback = video_detect_force_none,
 537          .ident = "MSI MS-7721",
 538          .matches = {
 539                 DMI_MATCH(DMI_SYS_VENDOR, "MSI"),
 540                 DMI_MATCH(DMI_PRODUCT_NAME, "MS-7721"),
 541                 },
 542         },
 543         { },
 544 };
 545
 546 /* This uses a workqueue to avoid various locking ordering issues */
 547 static void acpi_video_backlight_notify_work(struct work_struct *work)
 548 {
 549         if (acpi_video_get_backlight_type() != acpi_backlight_video)
 550                 acpi_video_unregister_backlight();
 551 }
 552
 553 static int acpi_video_backlight_notify(struct notifier_block *nb,
 554                                        unsigned long val, void *bd)
 555 {
 556         struct backlight_device *backlight = bd;
 557
 558         /* A raw bl registering may change video -> native */
 559         if (backlight->props.type == BACKLIGHT_RAW &&
 560             val == BACKLIGHT_REGISTERED)
 561                 schedule_work(&backlight_notify_work);
 562
 563         return NOTIFY_OK;
 564 }
 565
 566 /*
 567  * Determine which type of backlight interface to use on this system,
 568  * First check cmdline, then dmi quirks, then do autodetect.
 569  *
 570  * The autodetect order is:
 571  * 1) Is the acpi-video backlight interface supported ->
 572  *  no, use a vendor interface
 573  * 2) Is this a win8 "ready" BIOS and do we have a native interface ->
 574  *  yes, use a native interface
 575  * 3) Else use the acpi-video interface
 576  *
 577  * Arguably the native on win8 check should be done first, but that would
 578  * be a behavior change, which may causes issues.
 579  */
 580 enum acpi_backlight_type acpi_video_get_backlight_type(void)
 581 {
 582         static DEFINE_MUTEX(init_mutex);
 583         static bool init_done;
 584         static long video_caps;
 585
 586         /* Parse cmdline, dmi and acpi only once */
 587         mutex_lock(&init_mutex);
 588         if (!init_done) {
 589                 acpi_video_parse_cmdline();
 590                 dmi_check_system(video_detect_dmi_table);
 591                 acpi_walk_namespace(ACPI_TYPE_DEVICE, ACPI_ROOT_OBJECT,
 592                                     ACPI_UINT32_MAX, find_video, NULL,
 593                                     &video_caps, NULL);
 594                 INIT_WORK(&backlight_notify_work,
 595                           acpi_video_backlight_notify_work);
 596                 backlight_nb.notifier_call = acpi_video_backlight_notify;
 597                 backlight_nb.priority = 0;
 598                 if (backlight_register_notifier(&backlight_nb) == 0)
 599                         backlight_notifier_registered = true;
 600                 init_done = true;
 601         }
 602         mutex_unlock(&init_mutex);
 603
 604         if (acpi_backlight_cmdline != acpi_backlight_undef)
 605                 return acpi_backlight_cmdline;
 606
 607         if (acpi_backlight_dmi != acpi_backlight_undef)
 608                 return acpi_backlight_dmi;
 609
 610         if (!(video_caps & ACPI_VIDEO_BACKLIGHT))
 611                 return acpi_backlight_vendor;
 612
 613         if (acpi_osi_is_win8() && backlight_device_get_by_type(BACKLIGHT_RAW))
 614                 return acpi_backlight_native;
 615
 616         return acpi_backlight_video;
 617 }
 618 EXPORT_SYMBOL(acpi_video_get_backlight_type);
 619
 620 /*
 621  * Set the preferred backlight interface type based on DMI info.
 622  * This function allows DMI blacklists to be implemented by external
 623  * platform drivers instead of putting a big blacklist in video_detect.c
 624  */
 625 void acpi_video_set_dmi_backlight_type(enum acpi_backlight_type type)
 626 {
 627         acpi_backlight_dmi = type;
 628         /* Remove acpi-video backlight interface if it is no longer desired */
 629         if (acpi_video_get_backlight_type() != acpi_backlight_video)
 630                 acpi_video_unregister_backlight();
 631 }
 632 EXPORT_SYMBOL(acpi_video_set_dmi_backlight_type);
 633
 634 void __exit acpi_video_detect_exit(void)
 635 {
 636         if (backlight_notifier_registered)
 637                 backlight_unregister_notifier(&backlight_nb);
 638 }