Display Backlight does not respond

English Hardware
#1

Display backlight is not responding whether through the keyboard shortcut or with slider within the system.
The keyboard shortcuts work. I clearly see the display backlight on screen. The slider in Settings/Energy works as well but no response to the display backlight. Brightness is constant at 100%. I am blind now :slight_smile:

When powersaving kicks, displayed is dimmed.

Tried update GRUB with acpi_backlight (vendor/native/video/linux) but to no avail.

Any help is much appreciated because I am about to loose my eyes very soon.

KDE with Leap 15.3 (latest as of today)

#2

Hi
AMD graphics by chance? If it is then if you check the journal for backlight you will find acpi backlight and amd backlight fighting each other, disable and mask the acpi one.

#3

What exactly am I looking for ? I have an AMD graphics.
Looking through the logs
org.kde.powerdevil: org.kde.powerdevil.backlighthelper.brightness failed

#4

Hi
Something like the following;


journalctl -b | grep backlight


systemd[1]: Starting Load/Save Screen Backlight Brightness of backlight:amdgpu_bl0...


systemd-backlight[1384]: Failed to get backlight or LED device 'backlight:acpi_video0'

If so, then use;


systemctl stop systemd-backlight@backlight:acpi_video0.service


systemctl disable systemd-backlight@backlight:acpi_video0.service


systemctl mask systemd-backlight@backlight:acpi_video0.service
#5

I don’t have anything relating to ‘backlight:amdgpu_bl0’.
I do have ‘backlight:acpi_video0.service’
Nothing seems to be failed.
Power dims the laptop display backlight correctly.

#6

I went ahead and followed the code below but still a no go

systemctl stop systemd-backlight@backlight:acpi_video0.service
systemctl disable systemd-backlight@backlight:acpi_video0.service
systemctl mask systemd-backlight@backlight:acpi_video0.service

Probably because I don’t have the 'backlight:amdgpu_bl0" ?
I have added this ‘acpi_backlight=vendor’ but still no effect.

#7

I just discovered that if I remove ‘acpi_backlight=vendor’ in Grub, the slider within Setting/Energy is gone. The slider in any case does not work. It moves up and down but has no effect on the display backlight which is stuck at 100%

#8

Made it worked finally.
1 - make sure you are using the discrete card and not the switchable.
2 - Add this to grub “nvidia.NVreg_RegistryDwords=EnableBrightnessControl=1”

Now the brightness is working and can be dimmed down. I have just saved my eyes rotfl!

PS: If using KDE, the slider in Setting/Energy won’t work. Only the keyboard shortcut. I guess another story for another day…

#9

You said nothing about hardware.
Possibly too new AMD GPU for Leap 15.3. Try to use Live TW.