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 which
  21  * driver should handle the backlight. RAW/GPU-driver backlight drivers must
  22  * use the acpi_video_backlight_use_native() helper for this.
  23  *
  24  * If CONFIG_ACPI_VIDEO is neither set as "compiled in" (y) nor as a module (m)
  25  * this file will not be compiled and acpi_video_get_backlight_type() will
  26  * always return acpi_backlight_vendor.
  27  */
  28
  29 #include <linux/export.h>
  30 #include <linux/acpi.h>
  31 #include <linux/backlight.h>
  32 #include <linux/dmi.h>
  33 #include <linux/module.h>
  34 #include <linux/pci.h>
  35 #include <linux/types.h>
  36 #include <linux/workqueue.h>
  37 #include <acpi/video.h>
  38
  39 void acpi_video_unregister_backlight(void);
  40
  41 static enum acpi_backlight_type acpi_backlight_cmdline = acpi_backlight_undef;
  42 static enum acpi_backlight_type acpi_backlight_dmi = acpi_backlight_undef;
  43
  44 static void acpi_video_parse_cmdline(void)
  45 {
  46         if (!strcmp("vendor", acpi_video_backlight_string))
  47                 acpi_backlight_cmdline = acpi_backlight_vendor;
  48         if (!strcmp("video", acpi_video_backlight_string))
  49                 acpi_backlight_cmdline = acpi_backlight_video;
  50         if (!strcmp("native", acpi_video_backlight_string))
  51                 acpi_backlight_cmdline = acpi_backlight_native;
  52         if (!strcmp("none", acpi_video_backlight_string))
  53                 acpi_backlight_cmdline = acpi_backlight_none;
  54 }
  55
  56 static acpi_status
  57 find_video(acpi_handle handle, u32 lvl, void *context, void **rv)
  58 {
  59         struct acpi_device *acpi_dev = acpi_fetch_acpi_dev(handle);
  60         long *cap = context;
  61         struct pci_dev *dev;
  62
  63         static const struct acpi_device_id video_ids[] = {
  64                 {ACPI_VIDEO_HID, 0},
  65                 {"", 0},
  66         };
  67
  68         if (acpi_dev && !acpi_match_device_ids(acpi_dev, video_ids)) {
  69                 dev = acpi_get_pci_dev(handle);
  70                 if (!dev)
  71                         return AE_OK;
  72                 pci_dev_put(dev);
  73                 *cap |= acpi_is_video_device(handle);
  74         }
  75         return AE_OK;
  76 }
  77
  78 /* Force to use vendor driver when the ACPI device is known to be
  79  * buggy */
  80 static int video_detect_force_vendor(const struct dmi_system_id *d)
  81 {
  82         acpi_backlight_dmi = acpi_backlight_vendor;
  83         return 0;
  84 }
  85
  86 static int video_detect_force_video(const struct dmi_system_id *d)
  87 {
  88         acpi_backlight_dmi = acpi_backlight_video;
  89         return 0;
  90 }
  91
  92 static int video_detect_force_native(const struct dmi_system_id *d)
  93 {
  94         acpi_backlight_dmi = acpi_backlight_native;
  95         return 0;
  96 }
  97
  98 static int video_detect_force_none(const struct dmi_system_id *d)
  99 {
 100         acpi_backlight_dmi = acpi_backlight_none;
 101         return 0;
 102 }
 103
 104 static const struct dmi_system_id video_detect_dmi_table[] = {
 105         /* On Samsung X360, the BIOS will set a flag (VDRV) if generic
 106          * ACPI backlight device is used. This flag will definitively break
 107          * the backlight interface (even the vendor interface) until next
 108          * reboot. It's why we should prevent video.ko from being used here
 109          * and we can't rely on a later call to acpi_video_unregister().
 110          */
 111         {
 112          .callback = video_detect_force_vendor,
 113          /* X360 */
 114          .matches = {
 115                 DMI_MATCH(DMI_SYS_VENDOR, "SAMSUNG ELECTRONICS CO., LTD."),
 116                 DMI_MATCH(DMI_PRODUCT_NAME, "X360"),
 117                 DMI_MATCH(DMI_BOARD_NAME, "X360"),
 118                 },
 119         },
 120         {
 121         .callback = video_detect_force_vendor,
 122         /* Asus UL30VT */
 123         .matches = {
 124                 DMI_MATCH(DMI_SYS_VENDOR, "ASUSTeK Computer Inc."),
 125                 DMI_MATCH(DMI_PRODUCT_NAME, "UL30VT"),
 126                 },
 127         },
 128         {
 129         .callback = video_detect_force_vendor,
 130         /* Asus UL30A */
 131         .matches = {
 132                 DMI_MATCH(DMI_SYS_VENDOR, "ASUSTeK Computer Inc."),
 133                 DMI_MATCH(DMI_PRODUCT_NAME, "UL30A"),
 134                 },
 135         },
 136         {
 137         .callback = video_detect_force_vendor,
 138         /* GIGABYTE GB-BXBT-2807 */
 139         .matches = {
 140                 DMI_MATCH(DMI_SYS_VENDOR, "GIGABYTE"),
 141                 DMI_MATCH(DMI_PRODUCT_NAME, "GB-BXBT-2807"),
 142                 },
 143         },
 144         {
 145         .callback = video_detect_force_vendor,
 146         /* Sony VPCEH3U1E */
 147         .matches = {
 148                 DMI_MATCH(DMI_SYS_VENDOR, "Sony Corporation"),
 149                 DMI_MATCH(DMI_PRODUCT_NAME, "VPCEH3U1E"),
 150                 },
 151         },
 152         {
 153         .callback = video_detect_force_vendor,
 154         /* Xiaomi Mi Pad 2 */
 155         .matches = {
 156                         DMI_MATCH(DMI_SYS_VENDOR, "Xiaomi Inc"),
 157                         DMI_MATCH(DMI_PRODUCT_NAME, "Mipad2"),
 158                 },
 159         },
 160
 161         /*
 162          * These models have a working acpi_video backlight control, and using
 163          * native backlight causes a regression where backlight does not work
 164          * when userspace is not handling brightness key events. Disable
 165          * native_backlight on these to fix this:
 166          * https://bugzilla.kernel.org/show_bug.cgi?id=81691
 167          */
 168         {
 169          .callback = video_detect_force_video,
 170          /* ThinkPad T420 */
 171          .matches = {
 172                 DMI_MATCH(DMI_SYS_VENDOR, "LENOVO"),
 173                 DMI_MATCH(DMI_PRODUCT_VERSION, "ThinkPad T420"),
 174                 },
 175         },
 176         {
 177          .callback = video_detect_force_video,
 178          /* ThinkPad T520 */
 179          .matches = {
 180                 DMI_MATCH(DMI_SYS_VENDOR, "LENOVO"),
 181                 DMI_MATCH(DMI_PRODUCT_VERSION, "ThinkPad T520"),
 182                 },
 183         },
 184         {
 185          .callback = video_detect_force_video,
 186          /* ThinkPad X201s */
 187          .matches = {
 188                 DMI_MATCH(DMI_SYS_VENDOR, "LENOVO"),
 189                 DMI_MATCH(DMI_PRODUCT_VERSION, "ThinkPad X201s"),
 190                 },
 191         },
 192         {
 193          .callback = video_detect_force_video,
 194          /* ThinkPad X201T */
 195          .matches = {
 196                 DMI_MATCH(DMI_SYS_VENDOR, "LENOVO"),
 197                 DMI_MATCH(DMI_PRODUCT_VERSION, "ThinkPad X201T"),
 198                 },
 199         },
 200
 201         /* The native backlight controls do not work on some older machines */
 202         {
 203          /* https://bugs.freedesktop.org/show_bug.cgi?id=81515 */
 204          .callback = video_detect_force_video,
 205          /* HP ENVY 15 Notebook */
 206          .matches = {
 207                 DMI_MATCH(DMI_SYS_VENDOR, "Hewlett-Packard"),
 208                 DMI_MATCH(DMI_PRODUCT_NAME, "HP ENVY 15 Notebook PC"),
 209                 },
 210         },
 211         {
 212          .callback = video_detect_force_video,
 213          /* SAMSUNG 870Z5E/880Z5E/680Z5E */
 214          .matches = {
 215                 DMI_MATCH(DMI_SYS_VENDOR, "SAMSUNG ELECTRONICS CO., LTD."),
 216                 DMI_MATCH(DMI_PRODUCT_NAME, "870Z5E/880Z5E/680Z5E"),
 217                 },
 218         },
 219         {
 220          .callback = video_detect_force_video,
 221          /* SAMSUNG 370R4E/370R4V/370R5E/3570RE/370R5V */
 222          .matches = {
 223                 DMI_MATCH(DMI_SYS_VENDOR, "SAMSUNG ELECTRONICS CO., LTD."),
 224                 DMI_MATCH(DMI_PRODUCT_NAME,
 225                           "370R4E/370R4V/370R5E/3570RE/370R5V"),
 226                 },
 227         },
 228         {
 229          /* https://bugzilla.redhat.com/show_bug.cgi?id=1186097 */
 230          .callback = video_detect_force_video,
 231          /* SAMSUNG 3570R/370R/470R/450R/510R/4450RV */
 232          .matches = {
 233                 DMI_MATCH(DMI_SYS_VENDOR, "SAMSUNG ELECTRONICS CO., LTD."),
 234                 DMI_MATCH(DMI_PRODUCT_NAME,
 235                           "3570R/370R/470R/450R/510R/4450RV"),
 236                 },
 237         },
 238         {
 239          /* https://bugzilla.redhat.com/show_bug.cgi?id=1557060 */
 240          .callback = video_detect_force_video,
 241          /* SAMSUNG 670Z5E */
 242          .matches = {
 243                 DMI_MATCH(DMI_SYS_VENDOR, "SAMSUNG ELECTRONICS CO., LTD."),
 244                 DMI_MATCH(DMI_PRODUCT_NAME, "670Z5E"),
 245                 },
 246         },
 247         {
 248          /* https://bugzilla.redhat.com/show_bug.cgi?id=1094948 */
 249          .callback = video_detect_force_video,
 250          /* SAMSUNG 730U3E/740U3E */
 251          .matches = {
 252                 DMI_MATCH(DMI_SYS_VENDOR, "SAMSUNG ELECTRONICS CO., LTD."),
 253                 DMI_MATCH(DMI_PRODUCT_NAME, "730U3E/740U3E"),
 254                 },
 255         },
 256         {
 257          /* https://bugs.freedesktop.org/show_bug.cgi?id=87286 */
 258          .callback = video_detect_force_video,
 259          /* SAMSUNG 900X3C/900X3D/900X3E/900X4C/900X4D */
 260          .matches = {
 261                 DMI_MATCH(DMI_SYS_VENDOR, "SAMSUNG ELECTRONICS CO., LTD."),
 262                 DMI_MATCH(DMI_PRODUCT_NAME,
 263                           "900X3C/900X3D/900X3E/900X4C/900X4D"),
 264                 },
 265         },
 266         {
 267          /* https://bugzilla.redhat.com/show_bug.cgi?id=1272633 */
 268          .callback = video_detect_force_video,
 269          /* Dell XPS14 L421X */
 270          .matches = {
 271                 DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
 272                 DMI_MATCH(DMI_PRODUCT_NAME, "XPS L421X"),
 273                 },
 274         },
 275         {
 276          /* https://bugzilla.redhat.com/show_bug.cgi?id=1163574 */
 277          .callback = video_detect_force_video,
 278          /* Dell XPS15 L521X */
 279          .matches = {
 280                 DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
 281                 DMI_MATCH(DMI_PRODUCT_NAME, "XPS L521X"),
 282                 },
 283         },
 284         {
 285          /* https://bugzilla.kernel.org/show_bug.cgi?id=108971 */
 286          .callback = video_detect_force_video,
 287          /* SAMSUNG 530U4E/540U4E */
 288          .matches = {
 289                 DMI_MATCH(DMI_SYS_VENDOR, "SAMSUNG ELECTRONICS CO., LTD."),
 290                 DMI_MATCH(DMI_PRODUCT_NAME, "530U4E/540U4E"),
 291                 },
 292         },
 293         /* https://bugs.launchpad.net/bugs/1894667 */
 294         {
 295          .callback = video_detect_force_video,
 296          /* HP 635 Notebook */
 297          .matches = {
 298                 DMI_MATCH(DMI_SYS_VENDOR, "Hewlett-Packard"),
 299                 DMI_MATCH(DMI_PRODUCT_NAME, "HP 635 Notebook PC"),
 300                 },
 301         },
 302
 303         /* Non win8 machines which need native backlight nevertheless */
 304         {
 305          /* https://bugzilla.redhat.com/show_bug.cgi?id=1201530 */
 306          .callback = video_detect_force_native,
 307          /* Lenovo Ideapad S405 */
 308          .matches = {
 309                 DMI_MATCH(DMI_SYS_VENDOR, "LENOVO"),
 310                 DMI_MATCH(DMI_BOARD_NAME, "Lenovo IdeaPad S405"),
 311                 },
 312         },
 313         {
 314          /* https://bugzilla.redhat.com/show_bug.cgi?id=1187004 */
 315          .callback = video_detect_force_native,
 316          /* Lenovo Ideapad Z570 */
 317          .matches = {
 318                 DMI_MATCH(DMI_SYS_VENDOR, "LENOVO"),
 319                 DMI_MATCH(DMI_PRODUCT_NAME, "102434U"),
 320                 },
 321         },
 322         {
 323          .callback = video_detect_force_native,
 324          /* Lenovo E41-25 */
 325          .matches = {
 326                 DMI_MATCH(DMI_SYS_VENDOR, "LENOVO"),
 327                 DMI_MATCH(DMI_PRODUCT_NAME, "81FS"),
 328                 },
 329         },
 330         {
 331          .callback = video_detect_force_native,
 332          /* Lenovo E41-45 */
 333          .matches = {
 334                 DMI_MATCH(DMI_SYS_VENDOR, "LENOVO"),
 335                 DMI_MATCH(DMI_PRODUCT_NAME, "82BK"),
 336                 },
 337         },
 338         {
 339          /* https://bugzilla.redhat.com/show_bug.cgi?id=1217249 */
 340          .callback = video_detect_force_native,
 341          /* Apple MacBook Pro 12,1 */
 342          .matches = {
 343                 DMI_MATCH(DMI_SYS_VENDOR, "Apple Inc."),
 344                 DMI_MATCH(DMI_PRODUCT_NAME, "MacBookPro12,1"),
 345                 },
 346         },
 347         {
 348          .callback = video_detect_force_native,
 349          /* Dell Inspiron N4010 */
 350          .matches = {
 351                 DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
 352                 DMI_MATCH(DMI_PRODUCT_NAME, "Inspiron N4010"),
 353                 },
 354         },
 355         {
 356          .callback = video_detect_force_native,
 357          /* Dell Vostro V131 */
 358          .matches = {
 359                 DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
 360                 DMI_MATCH(DMI_PRODUCT_NAME, "Vostro V131"),
 361                 },
 362         },
 363         {
 364          /* https://bugzilla.redhat.com/show_bug.cgi?id=1123661 */
 365          .callback = video_detect_force_native,
 366          /* Dell XPS 17 L702X */
 367          .matches = {
 368                 DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
 369                 DMI_MATCH(DMI_PRODUCT_NAME, "Dell System XPS L702X"),
 370                 },
 371         },
 372         {
 373          .callback = video_detect_force_native,
 374          /* Dell Precision 7510 */
 375          .matches = {
 376                 DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
 377                 DMI_MATCH(DMI_PRODUCT_NAME, "Precision 7510"),
 378                 },
 379         },
 380         {
 381          .callback = video_detect_force_native,
 382          /* Acer Aspire 5738z */
 383          .matches = {
 384                 DMI_MATCH(DMI_SYS_VENDOR, "Acer"),
 385                 DMI_MATCH(DMI_PRODUCT_NAME, "Aspire 5738"),
 386                 DMI_MATCH(DMI_BOARD_NAME, "JV50"),
 387                 },
 388         },
 389         {
 390          /* https://bugzilla.kernel.org/show_bug.cgi?id=207835 */
 391          .callback = video_detect_force_native,
 392          /* Acer TravelMate 5735Z */
 393          .matches = {
 394                 DMI_MATCH(DMI_SYS_VENDOR, "Acer"),
 395                 DMI_MATCH(DMI_PRODUCT_NAME, "TravelMate 5735Z"),
 396                 DMI_MATCH(DMI_BOARD_NAME, "BA51_MV"),
 397                 },
 398         },
 399         {
 400         .callback = video_detect_force_native,
 401         /* ASUSTeK COMPUTER INC. GA401 */
 402         .matches = {
 403                 DMI_MATCH(DMI_SYS_VENDOR, "ASUSTeK COMPUTER INC."),
 404                 DMI_MATCH(DMI_PRODUCT_NAME, "GA401"),
 405                 },
 406         },
 407         {
 408         .callback = video_detect_force_native,
 409         /* ASUSTeK COMPUTER INC. GA502 */
 410         .matches = {
 411                 DMI_MATCH(DMI_SYS_VENDOR, "ASUSTeK COMPUTER INC."),
 412                 DMI_MATCH(DMI_PRODUCT_NAME, "GA502"),
 413                 },
 414         },
 415         {
 416         .callback = video_detect_force_native,
 417         /* ASUSTeK COMPUTER INC. GA503 */
 418         .matches = {
 419                 DMI_MATCH(DMI_SYS_VENDOR, "ASUSTeK COMPUTER INC."),
 420                 DMI_MATCH(DMI_PRODUCT_NAME, "GA503"),
 421                 },
 422         },
 423         /*
 424          * Clevo NL5xRU and NL5xNU/TUXEDO Aura 15 Gen1 and Gen2 have both a
 425          * working native and video interface. However the default detection
 426          * mechanism first registers the video interface before unregistering
 427          * it again and switching to the native interface during boot. This
 428          * results in a dangling SBIOS request for backlight change for some
 429          * reason, causing the backlight to switch to ~2% once per boot on the
 430          * first power cord connect or disconnect event. Setting the native
 431          * interface explicitly circumvents this buggy behaviour, by avoiding
 432          * the unregistering process.
 433          */
 434         {
 435         .callback = video_detect_force_native,
 436         .ident = "Clevo NL5xRU",
 437         .matches = {
 438                 DMI_MATCH(DMI_BOARD_NAME, "NL5xRU"),
 439                 },
 440         },
 441         {
 442         .callback = video_detect_force_native,
 443         .ident = "Clevo NL5xRU",
 444         .matches = {
 445                 DMI_MATCH(DMI_SYS_VENDOR, "TUXEDO"),
 446                 DMI_MATCH(DMI_BOARD_NAME, "AURA1501"),
 447                 },
 448         },
 449         {
 450         .callback = video_detect_force_native,
 451         .ident = "Clevo NL5xRU",
 452         .matches = {
 453                 DMI_MATCH(DMI_SYS_VENDOR, "TUXEDO"),
 454                 DMI_MATCH(DMI_BOARD_NAME, "EDUBOOK1502"),
 455                 },
 456         },
 457         {
 458         .callback = video_detect_force_native,
 459         .ident = "Clevo NL5xNU",
 460         .matches = {
 461                 DMI_MATCH(DMI_BOARD_NAME, "NL5xNU"),
 462                 },
 463         },
 464         /*
 465          * The TongFang PF5PU1G, PF4NU1F, PF5NU1G, and PF5LUXG/TUXEDO BA15 Gen10,
 466          * Pulse 14/15 Gen1, and Pulse 15 Gen2 have the same problem as the Clevo
 467          * NL5xRU and NL5xNU/TUXEDO Aura 15 Gen1 and Gen2. See the description
 468          * above.
 469          */
 470         {
 471         .callback = video_detect_force_native,
 472         .ident = "TongFang PF5PU1G",
 473         .matches = {
 474                 DMI_MATCH(DMI_BOARD_NAME, "PF5PU1G"),
 475                 },
 476         },
 477         {
 478         .callback = video_detect_force_native,
 479         .ident = "TongFang PF4NU1F",
 480         .matches = {
 481                 DMI_MATCH(DMI_BOARD_NAME, "PF4NU1F"),
 482                 },
 483         },
 484         {
 485         .callback = video_detect_force_native,
 486         .ident = "TongFang PF4NU1F",
 487         .matches = {
 488                 DMI_MATCH(DMI_SYS_VENDOR, "TUXEDO"),
 489                 DMI_MATCH(DMI_BOARD_NAME, "PULSE1401"),
 490                 },
 491         },
 492         {
 493         .callback = video_detect_force_native,
 494         .ident = "TongFang PF5NU1G",
 495         .matches = {
 496                 DMI_MATCH(DMI_BOARD_NAME, "PF5NU1G"),
 497                 },
 498         },
 499         {
 500         .callback = video_detect_force_native,
 501         .ident = "TongFang PF5NU1G",
 502         .matches = {
 503                 DMI_MATCH(DMI_SYS_VENDOR, "TUXEDO"),
 504                 DMI_MATCH(DMI_BOARD_NAME, "PULSE1501"),
 505                 },
 506         },
 507         {
 508         .callback = video_detect_force_native,
 509         .ident = "TongFang PF5LUXG",
 510         .matches = {
 511                 DMI_MATCH(DMI_BOARD_NAME, "PF5LUXG"),
 512                 },
 513         },
 514         /*
 515          * Desktops which falsely report a backlight and which our heuristics
 516          * for this do not catch.
 517          */
 518         {
 519          .callback = video_detect_force_none,
 520          /* Dell OptiPlex 9020M */
 521          .matches = {
 522                 DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
 523                 DMI_MATCH(DMI_PRODUCT_NAME, "OptiPlex 9020M"),
 524                 },
 525         },
 526         {
 527          .callback = video_detect_force_none,
 528          /* MSI MS-7721 */
 529          .matches = {
 530                 DMI_MATCH(DMI_SYS_VENDOR, "MSI"),
 531                 DMI_MATCH(DMI_PRODUCT_NAME, "MS-7721"),
 532                 },
 533         },
 534         { },
 535 };
 536
 537 /*
 538  * Determine which type of backlight interface to use on this system,
 539  * First check cmdline, then dmi quirks, then do autodetect.
 540  */
 541 static enum acpi_backlight_type __acpi_video_get_backlight_type(bool native)
 542 {
 543         static DEFINE_MUTEX(init_mutex);
 544         static bool native_available;
 545         static bool init_done;
 546         static long video_caps;
 547
 548         /* Parse cmdline, dmi and acpi only once */
 549         mutex_lock(&init_mutex);
 550         if (!init_done) {
 551                 acpi_video_parse_cmdline();
 552                 dmi_check_system(video_detect_dmi_table);
 553                 acpi_walk_namespace(ACPI_TYPE_DEVICE, ACPI_ROOT_OBJECT,
 554                                     ACPI_UINT32_MAX, find_video, NULL,
 555                                     &video_caps, NULL);
 556                 init_done = true;
 557         }
 558         if (native)
 559                 native_available = true;
 560         mutex_unlock(&init_mutex);
 561
 562         /*
 563          * The below heuristics / detection steps are in order of descending
 564          * presedence. The commandline takes presedence over anything else.
 565          */
 566         if (acpi_backlight_cmdline != acpi_backlight_undef)
 567                 return acpi_backlight_cmdline;
 568
 569         /* DMI quirks override any autodetection. */
 570         if (acpi_backlight_dmi != acpi_backlight_undef)
 571                 return acpi_backlight_dmi;
 572
 573         /* On systems with ACPI video use either native or ACPI video. */
 574         if (video_caps & ACPI_VIDEO_BACKLIGHT) {
 575                 /*
 576                  * Windows 8 and newer no longer use the ACPI video interface,
 577                  * so it often does not work. If the ACPI tables are written
 578                  * for win8 and native brightness ctl is available, use that.
 579                  *
 580                  * The native check deliberately is inside the if acpi-video
 581                  * block on older devices without acpi-video support native
 582                  * is usually not the best choice.
 583                  */
 584                 if (acpi_osi_is_win8() && native_available)
 585                         return acpi_backlight_native;
 586                 else
 587                         return acpi_backlight_video;
 588         }
 589
 590         /* No ACPI video (old hw), use vendor specific fw methods. */
 591         return acpi_backlight_vendor;
 592 }
 593
 594 enum acpi_backlight_type acpi_video_get_backlight_type(void)
 595 {
 596         return __acpi_video_get_backlight_type(false);
 597 }
 598 EXPORT_SYMBOL(acpi_video_get_backlight_type);
 599
 600 bool acpi_video_backlight_use_native(void)
 601 {
 602         return __acpi_video_get_backlight_type(true) == acpi_backlight_native;
 603 }
 604 EXPORT_SYMBOL(acpi_video_backlight_use_native);
 605
 606 /*
 607  * Set the preferred backlight interface type based on DMI info.
 608  * This function allows DMI blacklists to be implemented by external
 609  * platform drivers instead of putting a big blacklist in video_detect.c
 610  */
 611 void acpi_video_set_dmi_backlight_type(enum acpi_backlight_type type)
 612 {
 613         acpi_backlight_dmi = type;
 614         /* Remove acpi-video backlight interface if it is no longer desired */
 615         if (acpi_video_get_backlight_type() != acpi_backlight_video)
 616                 acpi_video_unregister_backlight();
 617 }
 618 EXPORT_SYMBOL(acpi_video_set_dmi_backlight_type);