It started happening when I switched to Gnome. At first I had both Gnome and
Unity next to each other and when I logged in to Unity, I could still change
the backlight normally.
It only doesn't work under Gnome strangely.
I've tested the new kernel, but it had no effect:
Linux 4.8.0-040800rc6-generic #201609121119 SMP Mon Sep 12 15:21:03 UTC 2016
x86_64 x86_64 x86_64 GNU/Linux
** Tags added: kernel-bug-exists-upstream
** Changed in: linux (Ubuntu)
Status: Incomplete => Confirmed
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Changing backlight doesn't work in Gnome
Status in linux package in Ubuntu:
With Unity I can change the backlight with the hotkeys out of the box, didn't
had to do anything to get that working.
I've now switched to Gnome (by installing ubuntu-gnome-desktop), but I've not
found a way to get the hotkeys working for the backlight again. I also don't
see the backlight slider in the upper right menu or in the settings.
I've tried everything on this page:
I've tried different combinations in my grub configuration:
I've also added 'EnableBrightnessControl' to my xorg.conf.
Unfortunately, nothing changes.
And /sys/class/backlight/ is always empty.
The only thing that did make a difference was adding 'acpi_os=' to my grub
This did show the backlight slider in the settings & menu. And did show the
pop-up when changing the backlight via the hotkeys.
Unfortunately, it didn't change the backlight. And the slider didn't go
futher than 5% or something.
During all my tests xbacklight always worked. That's the only way to change
my backlight in Gnome atm. Only when I added 'acpi_os=' xbacklight stopped
DistroRelease: Ubuntu 16.04
Package: linux-image-4.4.0-36-generic 4.4.0-36.55
ProcVersionSignature: Ubuntu 4.4.0-36.55-generic 4.4.16
Uname: Linux 4.4.0-36-generic x86_64
NonfreeKernelModules: nvidia_uvm nvidia_drm nvidia_modeset nvidia
USER PID ACCESS COMMAND
/dev/snd/controlC1: tpater 2523 F.... pulseaudio
/dev/snd/controlC0: tpater 2523 F.... pulseaudio
Date: Fri Sep 16 08:55:30 2016
InstallationDate: Installed on 2016-08-30 (17 days ago)
InstallationMedia: Ubuntu 16.04.1 LTS "Xenial Xerus" - Release amd64
MachineType: LENOVO 20ENCTO1WW
ProcFB: 0 EFI VGA
root=/dev/mapper/ubuntu--vg-root ro quiet splash vt.handoff=7
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.version: N1EET57W (1.30 )
dmi.board.asset.tag: Not Available
dmi.board.version: SDK0J40709 WIN
dmi.chassis.asset.tag: No Asset Information
dmi.product.version: ThinkPad P50
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