Bug 198907 - Backlight control missing with /sys/class/backlight/ empty
Summary: Backlight control missing with /sys/class/backlight/ empty
Status: NEW
Alias: None
Product: Drivers
Classification: Unclassified
Component: Video(DRI - non Intel) (show other bugs)
Hardware: Intel Linux
: P1 normal
Assignee: drivers_video-dri
Depends on:
Reported: 2018-02-23 19:46 UTC by Andrew
Modified: 2018-04-28 07:53 UTC (History)
2 users (show)

See Also:
Kernel Version: 4.14.0-3-amd64 #1 SMP Debian 4.14.13-1 (2018-01-14) x86_64 GNU/Linux
Tree: Mainline
Regression: No

dmesg with drm.debug=14 added (61.75 KB, text/plain)
2018-03-22 10:58 UTC, Andrew

Description Andrew 2018-02-23 19:46:09 UTC
Laptop HP Omen 15-ce012ur 
4.14.0-3-amd64 #1 SMP Debian 4.14.13-1 (2018-01-14) x86_64 GNU/Linux.

My video card shows in lspci as:

01:00.0 VGA compatible controller: NVIDIA Corporation GP106M [GeForce GTX 1060] (rev a1).

Freshly installed Debian. While loading, shows numerous copies of "ACPI Error: namespace lookup failure. AE_NOT_FOUND".
/sys/class/backlight/ was empty from the start, all ways of changing brightness do not exist. 
That also holds for live-USB with Debian and Ubuntu as well.
Comment 1 Zhang Rui 2018-03-12 07:12:13 UTC
reassign to the graphics experts
Comment 2 Jani Nikula 2018-03-19 08:33:32 UTC
Please attach dmesg with drm.debug=14 added.
Comment 3 Andrew 2018-03-22 10:58:30 UTC
Created attachment 274865 [details]
dmesg with drm.debug=14 added
Comment 4 Andrew 2018-03-22 10:58:50 UTC
(In reply to Jani Nikula from comment #2)
> Please attach dmesg with drm.debug=14 added.

Comment 5 Jani Nikula 2018-04-11 15:09:29 UTC
[    6.112689] nvidia: loading out-of-tree module taints kernel.
[    6.112708] nvidia: module license 'NVIDIA' taints kernel.
Comment 6 Manuel 2018-04-28 07:53:24 UTC

I have a very similar situation, in my opinion. I'm running kernel 4.15.0-20, my distro is Kubuntu 18.04, my hardware is a Dell XPS 15 9560 running with latest firmware (1.9.4) in UEFI mode.

/sys/class/backlight is also empty for me. I have an Intel 591B as well as an discrete NVIDIA GeForce GTX 1050. Situation is the same, no matter whether I'm using Intel or NVIDIA graphics.

I'm also getting ACPI errors at startup.

[    0.000000] ACPI: Core revision 20170831
[    0.000000] ACPI Error: [\_SB_.PCI0.XHC_.RHUB.HS11] Namespace lookup failure, AE_NOT_FOUND (20170831/dswload-210)
[    0.000000] ACPI Exception: AE_NOT_FOUND, During name lookup/catalog (20170831/psobject-252)
[    0.000000] ACPI Exception: AE_NOT_FOUND, (SSDT:xh_rvp11) while loading table (20170831/tbxfload-228)
[    0.000000] ACPI Error: 1 table load failures, 12 successful (20170831/tbxfload-246)

I'm able to see ACPI events when pressing brightness down/up buttons:

 9DBB5994-A997-11� 000000d0 00000000
video/brightnessdown BRTDN 00000087 00000000 K
 9DBB5994-A997-11� 000000d0 00000000
video/brightnessup BRTUP 00000086 00000000 K

I played around with acpi_osi and acpi_backlight, but this doesn't change anything.


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