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>
7 * May be copied or modified under the terms of the GNU General Public License
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
14 * Depending on whether ACPI graphics extensions (cmp. ACPI spec Appendix B)
15 * are available, video.ko should be used to handle the device.
17 * Otherwise vendor specific drivers like thinkpad_acpi, asus-laptop,
18 * sony_acpi,... can take care about backlight brightness.
20 * Backlight drivers can use acpi_video_get_backlight_type() to determine
21 * which driver should handle the backlight.
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.
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>
38 void acpi_video_unregister_backlight(void);
40 static bool backlight_notifier_registered;
41 static struct notifier_block backlight_nb;
42 static struct work_struct backlight_notify_work;
44 static enum acpi_backlight_type acpi_backlight_cmdline = acpi_backlight_undef;
45 static enum acpi_backlight_type acpi_backlight_dmi = acpi_backlight_undef;
47 static void acpi_video_parse_cmdline(void)
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;
60 find_video(acpi_handle handle, u32 lvl, void *context, void **rv)
64 struct acpi_device *acpi_dev;
66 static const struct acpi_device_id video_ids[] = {
70 if (acpi_bus_get_device(handle, &acpi_dev))
73 if (!acpi_match_device_ids(acpi_dev, video_ids)) {
74 dev = acpi_get_pci_dev(handle);
78 *cap |= acpi_is_video_device(handle);
83 /* Force to use vendor driver when the ACPI device is known to be
85 static int video_detect_force_vendor(const struct dmi_system_id *d)
87 acpi_backlight_dmi = acpi_backlight_vendor;
91 static int video_detect_force_video(const struct dmi_system_id *d)
93 acpi_backlight_dmi = acpi_backlight_video;
97 static int video_detect_force_native(const struct dmi_system_id *d)
99 acpi_backlight_dmi = acpi_backlight_native;
103 static int video_detect_force_none(const struct dmi_system_id *d)
105 acpi_backlight_dmi = acpi_backlight_none;
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().
117 .callback = video_detect_force_vendor,
120 DMI_MATCH(DMI_SYS_VENDOR, "SAMSUNG ELECTRONICS CO., LTD."),
121 DMI_MATCH(DMI_PRODUCT_NAME, "X360"),
122 DMI_MATCH(DMI_BOARD_NAME, "X360"),
126 .callback = video_detect_force_vendor,
127 .ident = "Asus UL30VT",
129 DMI_MATCH(DMI_SYS_VENDOR, "ASUSTeK Computer Inc."),
130 DMI_MATCH(DMI_PRODUCT_NAME, "UL30VT"),
134 .callback = video_detect_force_vendor,
135 .ident = "Asus UL30A",
137 DMI_MATCH(DMI_SYS_VENDOR, "ASUSTeK Computer Inc."),
138 DMI_MATCH(DMI_PRODUCT_NAME, "UL30A"),
142 .callback = video_detect_force_vendor,
143 .ident = "GIGABYTE GB-BXBT-2807",
145 DMI_MATCH(DMI_SYS_VENDOR, "GIGABYTE"),
146 DMI_MATCH(DMI_PRODUCT_NAME, "GB-BXBT-2807"),
150 .callback = video_detect_force_vendor,
151 .ident = "Sony VPCEH3U1E",
153 DMI_MATCH(DMI_SYS_VENDOR, "Sony Corporation"),
154 DMI_MATCH(DMI_PRODUCT_NAME, "VPCEH3U1E"),
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
166 .callback = video_detect_force_video,
167 .ident = "ThinkPad T420",
169 DMI_MATCH(DMI_SYS_VENDOR, "LENOVO"),
170 DMI_MATCH(DMI_PRODUCT_VERSION, "ThinkPad T420"),
174 .callback = video_detect_force_video,
175 .ident = "ThinkPad T520",
177 DMI_MATCH(DMI_SYS_VENDOR, "LENOVO"),
178 DMI_MATCH(DMI_PRODUCT_VERSION, "ThinkPad T520"),
182 .callback = video_detect_force_video,
183 .ident = "ThinkPad X201s",
185 DMI_MATCH(DMI_SYS_VENDOR, "LENOVO"),
186 DMI_MATCH(DMI_PRODUCT_VERSION, "ThinkPad X201s"),
190 .callback = video_detect_force_video,
191 .ident = "ThinkPad X201T",
193 DMI_MATCH(DMI_SYS_VENDOR, "LENOVO"),
194 DMI_MATCH(DMI_PRODUCT_VERSION, "ThinkPad X201T"),
198 /* The native backlight controls do not work on some older machines */
200 /* https://bugs.freedesktop.org/show_bug.cgi?id=81515 */
201 .callback = video_detect_force_video,
202 .ident = "HP ENVY 15 Notebook",
204 DMI_MATCH(DMI_SYS_VENDOR, "Hewlett-Packard"),
205 DMI_MATCH(DMI_PRODUCT_NAME, "HP ENVY 15 Notebook PC"),
209 .callback = video_detect_force_video,
210 .ident = "SAMSUNG 870Z5E/880Z5E/680Z5E",
212 DMI_MATCH(DMI_SYS_VENDOR, "SAMSUNG ELECTRONICS CO., LTD."),
213 DMI_MATCH(DMI_PRODUCT_NAME, "870Z5E/880Z5E/680Z5E"),
217 .callback = video_detect_force_video,
218 .ident = "SAMSUNG 370R4E/370R4V/370R5E/3570RE/370R5V",
220 DMI_MATCH(DMI_SYS_VENDOR, "SAMSUNG ELECTRONICS CO., LTD."),
221 DMI_MATCH(DMI_PRODUCT_NAME,
222 "370R4E/370R4V/370R5E/3570RE/370R5V"),
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",
230 DMI_MATCH(DMI_SYS_VENDOR, "SAMSUNG ELECTRONICS CO., LTD."),
231 DMI_MATCH(DMI_PRODUCT_NAME,
232 "3570R/370R/470R/450R/510R/4450RV"),
236 /* https://bugzilla.redhat.com/show_bug.cgi?id=1557060 */
237 .callback = video_detect_force_video,
238 .ident = "SAMSUNG 670Z5E",
240 DMI_MATCH(DMI_SYS_VENDOR, "SAMSUNG ELECTRONICS CO., LTD."),
241 DMI_MATCH(DMI_PRODUCT_NAME, "670Z5E"),
245 /* https://bugzilla.redhat.com/show_bug.cgi?id=1094948 */
246 .callback = video_detect_force_video,
247 .ident = "SAMSUNG 730U3E/740U3E",
249 DMI_MATCH(DMI_SYS_VENDOR, "SAMSUNG ELECTRONICS CO., LTD."),
250 DMI_MATCH(DMI_PRODUCT_NAME, "730U3E/740U3E"),
254 /* https://bugs.freedesktop.org/show_bug.cgi?id=87286 */
255 .callback = video_detect_force_video,
256 .ident = "SAMSUNG 900X3C/900X3D/900X3E/900X4C/900X4D",
258 DMI_MATCH(DMI_SYS_VENDOR, "SAMSUNG ELECTRONICS CO., LTD."),
259 DMI_MATCH(DMI_PRODUCT_NAME,
260 "900X3C/900X3D/900X3E/900X4C/900X4D"),
264 /* https://bugzilla.redhat.com/show_bug.cgi?id=1272633 */
265 .callback = video_detect_force_video,
266 .ident = "Dell XPS14 L421X",
268 DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
269 DMI_MATCH(DMI_PRODUCT_NAME, "XPS L421X"),
273 /* https://bugzilla.redhat.com/show_bug.cgi?id=1163574 */
274 .callback = video_detect_force_video,
275 .ident = "Dell XPS15 L521X",
277 DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
278 DMI_MATCH(DMI_PRODUCT_NAME, "XPS L521X"),
282 /* https://bugzilla.kernel.org/show_bug.cgi?id=108971 */
283 .callback = video_detect_force_video,
284 .ident = "SAMSUNG 530U4E/540U4E",
286 DMI_MATCH(DMI_SYS_VENDOR, "SAMSUNG ELECTRONICS CO., LTD."),
287 DMI_MATCH(DMI_PRODUCT_NAME, "530U4E/540U4E"),
290 /* https://bugs.launchpad.net/bugs/1894667 */
292 .callback = video_detect_force_video,
293 .ident = "HP 635 Notebook",
295 DMI_MATCH(DMI_SYS_VENDOR, "Hewlett-Packard"),
296 DMI_MATCH(DMI_PRODUCT_NAME, "HP 635 Notebook PC"),
300 /* Non win8 machines which need native backlight nevertheless */
302 /* https://bugzilla.redhat.com/show_bug.cgi?id=1201530 */
303 .callback = video_detect_force_native,
304 .ident = "Lenovo Ideapad S405",
306 DMI_MATCH(DMI_SYS_VENDOR, "LENOVO"),
307 DMI_MATCH(DMI_BOARD_NAME, "Lenovo IdeaPad S405"),
311 /* https://bugzilla.suse.com/show_bug.cgi?id=1208724 */
312 .callback = video_detect_force_native,
313 /* Lenovo Ideapad Z470 */
315 DMI_MATCH(DMI_SYS_VENDOR, "LENOVO"),
316 DMI_MATCH(DMI_PRODUCT_VERSION, "IdeaPad Z470"),
320 /* https://bugzilla.redhat.com/show_bug.cgi?id=1187004 */
321 .callback = video_detect_force_native,
322 .ident = "Lenovo Ideapad Z570",
324 DMI_MATCH(DMI_SYS_VENDOR, "LENOVO"),
325 DMI_MATCH(DMI_PRODUCT_VERSION, "Ideapad Z570"),
329 .callback = video_detect_force_native,
330 .ident = "Lenovo E41-25",
332 DMI_MATCH(DMI_SYS_VENDOR, "LENOVO"),
333 DMI_MATCH(DMI_PRODUCT_NAME, "81FS"),
337 .callback = video_detect_force_native,
338 .ident = "Lenovo E41-45",
340 DMI_MATCH(DMI_SYS_VENDOR, "LENOVO"),
341 DMI_MATCH(DMI_PRODUCT_NAME, "82BK"),
345 .callback = video_detect_force_native,
346 /* Lenovo ThinkPad X131e (3371 AMD version) */
348 DMI_MATCH(DMI_SYS_VENDOR, "LENOVO"),
349 DMI_MATCH(DMI_PRODUCT_NAME, "3371"),
353 .callback = video_detect_force_native,
356 DMI_MATCH(DMI_SYS_VENDOR, "Apple Inc."),
357 DMI_MATCH(DMI_PRODUCT_NAME, "iMac11,3"),
361 /* https://gitlab.freedesktop.org/drm/amd/-/issues/1838 */
362 .callback = video_detect_force_native,
365 DMI_MATCH(DMI_SYS_VENDOR, "Apple Inc."),
366 DMI_MATCH(DMI_PRODUCT_NAME, "iMac12,1"),
370 /* https://gitlab.freedesktop.org/drm/amd/-/issues/2753 */
371 .callback = video_detect_force_native,
374 DMI_MATCH(DMI_SYS_VENDOR, "Apple Inc."),
375 DMI_MATCH(DMI_PRODUCT_NAME, "iMac12,2"),
379 /* https://bugzilla.redhat.com/show_bug.cgi?id=1217249 */
380 .callback = video_detect_force_native,
381 .ident = "Apple MacBook Pro 12,1",
383 DMI_MATCH(DMI_SYS_VENDOR, "Apple Inc."),
384 DMI_MATCH(DMI_PRODUCT_NAME, "MacBookPro12,1"),
388 .callback = video_detect_force_native,
389 .ident = "Dell Vostro V131",
391 DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
392 DMI_MATCH(DMI_PRODUCT_NAME, "Vostro V131"),
396 /* https://bugzilla.redhat.com/show_bug.cgi?id=1123661 */
397 .callback = video_detect_force_native,
398 .ident = "Dell XPS 17 L702X",
400 DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
401 DMI_MATCH(DMI_PRODUCT_NAME, "Dell System XPS L702X"),
405 .callback = video_detect_force_native,
406 .ident = "Dell Precision 7510",
408 DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
409 DMI_MATCH(DMI_PRODUCT_NAME, "Precision 7510"),
413 .callback = video_detect_force_native,
414 .ident = "Acer Aspire 5738z",
416 DMI_MATCH(DMI_SYS_VENDOR, "Acer"),
417 DMI_MATCH(DMI_PRODUCT_NAME, "Aspire 5738"),
418 DMI_MATCH(DMI_BOARD_NAME, "JV50"),
422 /* https://bugzilla.kernel.org/show_bug.cgi?id=207835 */
423 .callback = video_detect_force_native,
424 .ident = "Acer TravelMate 5735Z",
426 DMI_MATCH(DMI_SYS_VENDOR, "Acer"),
427 DMI_MATCH(DMI_PRODUCT_NAME, "TravelMate 5735Z"),
428 DMI_MATCH(DMI_BOARD_NAME, "BA51_MV"),
432 .callback = video_detect_force_native,
433 .ident = "ASUSTeK COMPUTER INC. GA401",
435 DMI_MATCH(DMI_SYS_VENDOR, "ASUSTeK COMPUTER INC."),
436 DMI_MATCH(DMI_PRODUCT_NAME, "GA401"),
440 .callback = video_detect_force_native,
441 .ident = "ASUSTeK COMPUTER INC. GA502",
443 DMI_MATCH(DMI_SYS_VENDOR, "ASUSTeK COMPUTER INC."),
444 DMI_MATCH(DMI_PRODUCT_NAME, "GA502"),
448 .callback = video_detect_force_native,
449 .ident = "ASUSTeK COMPUTER INC. GA503",
451 DMI_MATCH(DMI_SYS_VENDOR, "ASUSTeK COMPUTER INC."),
452 DMI_MATCH(DMI_PRODUCT_NAME, "GA503"),
456 * Clevo NL5xRU and NL5xNU/TUXEDO Aura 15 Gen1 and Gen2 have both a
457 * working native and video interface. However the default detection
458 * mechanism first registers the video interface before unregistering
459 * it again and switching to the native interface during boot. This
460 * results in a dangling SBIOS request for backlight change for some
461 * reason, causing the backlight to switch to ~2% once per boot on the
462 * first power cord connect or disconnect event. Setting the native
463 * interface explicitly circumvents this buggy behaviour, by avoiding
464 * the unregistering process.
467 .callback = video_detect_force_native,
468 .ident = "Clevo NL5xRU",
470 DMI_MATCH(DMI_BOARD_NAME, "NL5xRU"),
474 .callback = video_detect_force_native,
475 .ident = "Clevo NL5xRU",
477 DMI_MATCH(DMI_SYS_VENDOR, "TUXEDO"),
478 DMI_MATCH(DMI_BOARD_NAME, "AURA1501"),
482 .callback = video_detect_force_native,
483 .ident = "Clevo NL5xRU",
485 DMI_MATCH(DMI_SYS_VENDOR, "TUXEDO"),
486 DMI_MATCH(DMI_BOARD_NAME, "EDUBOOK1502"),
490 .callback = video_detect_force_native,
491 .ident = "Clevo NL5xNU",
493 DMI_MATCH(DMI_BOARD_NAME, "NL5xNU"),
497 * The TongFang PF5PU1G, PF4NU1F, PF5NU1G, and PF5LUXG/TUXEDO BA15 Gen10,
498 * Pulse 14/15 Gen1, and Pulse 15 Gen2 have the same problem as the Clevo
499 * NL5xRU and NL5xNU/TUXEDO Aura 15 Gen1 and Gen2. See the description
503 .callback = video_detect_force_native,
504 .ident = "TongFang PF5PU1G",
506 DMI_MATCH(DMI_BOARD_NAME, "PF5PU1G"),
510 .callback = video_detect_force_native,
511 .ident = "TongFang PF4NU1F",
513 DMI_MATCH(DMI_BOARD_NAME, "PF4NU1F"),
517 .callback = video_detect_force_native,
518 .ident = "TongFang PF4NU1F",
520 DMI_MATCH(DMI_SYS_VENDOR, "TUXEDO"),
521 DMI_MATCH(DMI_BOARD_NAME, "PULSE1401"),
525 .callback = video_detect_force_native,
526 .ident = "TongFang PF5NU1G",
528 DMI_MATCH(DMI_BOARD_NAME, "PF5NU1G"),
532 .callback = video_detect_force_native,
533 .ident = "TongFang PF5NU1G",
535 DMI_MATCH(DMI_SYS_VENDOR, "TUXEDO"),
536 DMI_MATCH(DMI_BOARD_NAME, "PULSE1501"),
540 .callback = video_detect_force_native,
541 .ident = "TongFang PF5LUXG",
543 DMI_MATCH(DMI_BOARD_NAME, "PF5LUXG"),
547 * More Tongfang devices with the same issue as the Clevo NL5xRU and
548 * NL5xNU/TUXEDO Aura 15 Gen1 and Gen2. See the description above.
551 .callback = video_detect_force_native,
552 .ident = "TongFang GKxNRxx",
554 DMI_MATCH(DMI_BOARD_NAME, "GKxNRxx"),
558 .callback = video_detect_force_native,
559 .ident = "TongFang GKxNRxx",
561 DMI_MATCH(DMI_SYS_VENDOR, "TUXEDO"),
562 DMI_MATCH(DMI_BOARD_NAME, "POLARIS1501A1650TI"),
566 .callback = video_detect_force_native,
567 .ident = "TongFang GKxNRxx",
569 DMI_MATCH(DMI_SYS_VENDOR, "TUXEDO"),
570 DMI_MATCH(DMI_BOARD_NAME, "POLARIS1501A2060"),
574 .callback = video_detect_force_native,
575 .ident = "TongFang GKxNRxx",
577 DMI_MATCH(DMI_SYS_VENDOR, "TUXEDO"),
578 DMI_MATCH(DMI_BOARD_NAME, "POLARIS1701A1650TI"),
582 .callback = video_detect_force_native,
583 .ident = "TongFang GKxNRxx",
585 DMI_MATCH(DMI_SYS_VENDOR, "TUXEDO"),
586 DMI_MATCH(DMI_BOARD_NAME, "POLARIS1701A2060"),
590 .callback = video_detect_force_native,
591 .ident = "TongFang GMxNGxx",
593 DMI_MATCH(DMI_BOARD_NAME, "GMxNGxx"),
597 .callback = video_detect_force_native,
598 .ident = "TongFang GMxZGxx",
600 DMI_MATCH(DMI_BOARD_NAME, "GMxZGxx"),
604 .callback = video_detect_force_native,
605 .ident = "TongFang GMxRGxx",
607 DMI_MATCH(DMI_BOARD_NAME, "GMxRGxx"),
611 * Desktops which falsely report a backlight and which our heuristics
612 * for this do not catch.
615 .callback = video_detect_force_none,
616 .ident = "Dell OptiPlex 9020M",
618 DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
619 DMI_MATCH(DMI_PRODUCT_NAME, "OptiPlex 9020M"),
623 .callback = video_detect_force_none,
624 .ident = "MSI MS-7721",
626 DMI_MATCH(DMI_SYS_VENDOR, "MSI"),
627 DMI_MATCH(DMI_PRODUCT_NAME, "MS-7721"),
633 /* This uses a workqueue to avoid various locking ordering issues */
634 static void acpi_video_backlight_notify_work(struct work_struct *work)
636 if (acpi_video_get_backlight_type() != acpi_backlight_video)
637 acpi_video_unregister_backlight();
640 static int acpi_video_backlight_notify(struct notifier_block *nb,
641 unsigned long val, void *bd)
643 struct backlight_device *backlight = bd;
645 /* A raw bl registering may change video -> native */
646 if (backlight->props.type == BACKLIGHT_RAW &&
647 val == BACKLIGHT_REGISTERED)
648 schedule_work(&backlight_notify_work);
654 * Determine which type of backlight interface to use on this system,
655 * First check cmdline, then dmi quirks, then do autodetect.
657 * The autodetect order is:
658 * 1) Is the acpi-video backlight interface supported ->
659 * no, use a vendor interface
660 * 2) Is this a win8 "ready" BIOS and do we have a native interface ->
661 * yes, use a native interface
662 * 3) Else use the acpi-video interface
664 * Arguably the native on win8 check should be done first, but that would
665 * be a behavior change, which may causes issues.
667 enum acpi_backlight_type acpi_video_get_backlight_type(void)
669 static DEFINE_MUTEX(init_mutex);
670 static bool init_done;
671 static long video_caps;
673 /* Parse cmdline, dmi and acpi only once */
674 mutex_lock(&init_mutex);
676 acpi_video_parse_cmdline();
677 dmi_check_system(video_detect_dmi_table);
678 acpi_walk_namespace(ACPI_TYPE_DEVICE, ACPI_ROOT_OBJECT,
679 ACPI_UINT32_MAX, find_video, NULL,
681 INIT_WORK(&backlight_notify_work,
682 acpi_video_backlight_notify_work);
683 backlight_nb.notifier_call = acpi_video_backlight_notify;
684 backlight_nb.priority = 0;
685 if (backlight_register_notifier(&backlight_nb) == 0)
686 backlight_notifier_registered = true;
689 mutex_unlock(&init_mutex);
691 if (acpi_backlight_cmdline != acpi_backlight_undef)
692 return acpi_backlight_cmdline;
694 if (acpi_backlight_dmi != acpi_backlight_undef)
695 return acpi_backlight_dmi;
697 if (!(video_caps & ACPI_VIDEO_BACKLIGHT))
698 return acpi_backlight_vendor;
700 if (acpi_osi_is_win8() && backlight_device_get_by_type(BACKLIGHT_RAW))
701 return acpi_backlight_native;
703 return acpi_backlight_video;
705 EXPORT_SYMBOL(acpi_video_get_backlight_type);
708 * Set the preferred backlight interface type based on DMI info.
709 * This function allows DMI blacklists to be implemented by external
710 * platform drivers instead of putting a big blacklist in video_detect.c
712 void acpi_video_set_dmi_backlight_type(enum acpi_backlight_type type)
714 acpi_backlight_dmi = type;
715 /* Remove acpi-video backlight interface if it is no longer desired */
716 if (acpi_video_get_backlight_type() != acpi_backlight_video)
717 acpi_video_unregister_backlight();
719 EXPORT_SYMBOL(acpi_video_set_dmi_backlight_type);
721 void __exit acpi_video_detect_exit(void)
723 if (backlight_notifier_registered)
724 backlight_unregister_notifier(&backlight_nb);