Ubuntu – Ubuntu 20.04 laptop screen problems — birghtness can not be changed anymore


Since I upgraded from Ubuntu 19.10 to 20.04 (Gnome 3.36.1) I have some problems with the screen of my laptop (Clevo N151ZU, i7 8565U):

  • I can't change the screen brigthness with my keyboard (Fn + F8/9)
  • I can't change the screen brightness with the menu in the right top corner (where you can change the volume, shutdown the pc, etc.)
  • I can't change the screen brightness in the Gnome settings
    -My laptop display is shown as "Unknown Display" in the Gnome display settings
  • I can't change the Hz and the resolution (only avaiable option is 1920×1080) in the Gnome display settings
    -xbacklight is installed, the commands xbacklight -set 0, xbacklight -set 100 do nothing
  • When I close the lid of my laptop, it doesn't go to standby (I set the option "go to standby, when lid is closed" in the Gnome tweak tool)
  • The screen stays black, when I wake the laptop up from the standby (keyboard lights turn on, etc.)

On boot I get the error message:

i915: `' invalid for parameter `enable_dpcd_backlight

I tried it with these options in the GRUB_CMDLINE_LINUX_DEFAULT line in /etc/default/grub:

acpi_backlight=vendor, acpi_backlight=video, acpi_backlight=native

(with a sudo update-grub and a reboot after it, of course), didn't change anything.

I installed the xserver-xorg-video-intel, no differences.

Some system information:

$ glxinfo | grep "OpenGL core profile version string"
OpenGL core profile version string: 3.3 (Core Profile) Mesa 20.0.4

ls /sys/class/backlight/ returns nothing.

$ sudo find /sys/ -type f -iname '*brightness*'

Best Answer

  • I had the same issue with my Tuxedo laptop (slightly different model by Clevo). I just found that the syntax for enable_dpcd_backlight changed with the kernel version used in 20.04 (see here).

    Just change the corresponding line in /etc/modprobe.d/tuxedo-i915.conf to options i915 enable_dpcd_backlight=1 and reboot.