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After struggling to install NVIDIA drivers using the discrete graphics card, I finally recognized that my display backlight is always at full intensity and can not be changed via keyboard controls.

About my system

% sudo apt list --installed | grep nvidia
nvidia-387/artful,now 387.22-0ubuntu0~gpu17.10.2 amd64 [installed]
nvidia-opencl-icd-387/artful,now 387.22-0ubuntu0~gpu17.10.2 amd64 [installed,automatic]
nvidia-prime/artful,now 0.8.5 amd64 [installed,automatic]
nvidia-settings/artful,now 387.22-0ubuntu0~gpu17.10.1 amd64 [installed,automatic]

% ls /sys/class/backlight  # empty!

% ls /proc/acpi/ibm/                    
beep  bluetooth  cmos  driver  fan  hotkey  kbdlight  led  light  volume
% cat /proc/acpi/ibm/light
status:     off
commands:   on, off

% journalctl -b | grep backlight
Nov 17 10:46:10 P51 systemd[1]: Created slice system-systemd\x2dbacklight.slice.
Nov 17 10:46:10 P51 systemd[1]: Starting Load/Save Screen Backlight Brightness of leds:tpacpi::kbd_backlight...
Nov 17 10:46:10 P51 systemd[1]: Started Load/Save Screen Backlight Brightness of leds:tpacpi::kbd_backlight.
Nov 17 10:46:22 P51 gsd-media-keys[1489]: Failed to set new screen percentage: GDBus.Error:org.gtk.GDBus.UnmappedGError.Quark._gsd_5fpower_5fmanager_5ferror.Code0: Screen backlight not available

% journalctl | grep ACPI
[...]
Nov 17 10:46:10 P51 kernel: ACPI Error: [\_SB_.PCI0.XHC_.RHUB.HS11] Namespace lookup failure, AE_NOT_FOUND (20170531/dswload-210)
Nov 17 10:46:10 P51 kernel: ACPI Exception: AE_NOT_FOUND, During name lookup/catalog (20170531/psobject-252)
Nov 17 10:46:10 P51 kernel: ACPI Exception: AE_NOT_FOUND, (SSDT:ProjSsdt) while loading table (20170531/tbxfload-228)
Nov 17 10:46:10 P51 kernel: ACPI Error: 1 table load failures, 11 successful (20170531/tbxfload-246)
[...]

What I tried

  • I tried to modify GRUB_CMDLINE_LINUX_DEFAULT in /etc/default/grub (followed by update-grub2 and reboot) using always one of the following settings:

    acpi_backlight=video
acpi_backlight=vendor # thinkpad_acpi.brightness...
acpi_backlight=native

  • I created /usr/share/X11/xorg.conf.d/10-nvidia-brightness.conf:

    Section "Device"
    Identifier     "Device0"
    Driver         "nvidia"
    VendorName     "NVIDIA Corporation"
    BoardName      "Quadro M1200"
    Option         "RegistryDwords" "EnableBrightnessControl=1"
EndSection

None of the above methods did yield any results worth mentioning.

Michael Hoff
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  • Pretty much the identical issue. Ubuntu 17.10, on a Thinkpad P51. No solution yet but I've independently tried everything you've tried with one extra item.

    Adding this to grub instead:

    GRUB_CMDLINE_LINUX_DEFAULT="acpi_osi=Linux"

    Will cause the backlight prompt to react and seems to be "trying" but it seems to be incrementing/decrementing either by nothing or by too much?

     – samsquanch Jan 02 '18 at 23:50
  • Bug report filed: https://bugs.launchpad.net/ubuntu/+bug/1747273 – Michael Hoff Feb 04 '18 at 15:58

1 Answers1

-1

I found a workaround that work with my HP Zbook 15 with a nvidia quadro K610M. But none of the UI or hotkeys work. I always have to use a terminal...

My solution was to set the acpi_backlight to none in the grub config (/etc/default/grub): GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi_backlight=none"

Then I use the xbacklight command (just add it with apt-get install xbacklight) http://manpages.ubuntu.com/manpages/xenial/man1/xbacklight.1.html

For instance for 50% of brightness I can type xbacklight =50.

Source: https://askubuntu.com/a/937133/783249

gaetanc
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