Arch Linux

morten

Member

Registered: 2021-02-02

Posts: 8

Systemd backlight services failing

I was reading the "System Maintenance" page on the arch wiki, and it is recommended to check systemctl --failed, so I did this with this result

[morten@thinkpad ~]$ systemctl --failed
  UNIT                                            LOAD   ACTIVE SUB    DESCRIPTION                                                   
● systemd-backlight@backlight:acpi_video0.service loaded failed failed Load/Save Screen Backlight Brightness of backlight:acpi_video0
● systemd-backlight@backlight:amdgpu_bl0.service  loaded failed failed Load/Save Screen Backlight Brightness of backlight:amdgpu_bl0 

LOAD   = Reflects whether the unit definition was properly loaded.
ACTIVE = The high-level unit activation state, i.e. generalization of SUB.
SUB    = The low-level unit activation state, values depend on unit type.
2 loaded units listed.

I discovered I can ammend the amdgpu_bl0 service by

sudo systemctl start systemd-backlight@backlight:acpi_video0

Checking the status of the acpi_video0 service returns

Failed to start Load/Save Screen Backlight Brightness of backlight:acpi_video0.

with the corresponding journal saying

systemd-backlight[3026]: Failed to get backlight or LED device 'backlight:acpi_video0': No such device

I have tried tweaking the grub as in https://unix.stackexchange.com/question … uch-device, but this just results in my losing control of the backlighting entirely. How should I proceed with repairing the systemd-backlight@backlight:acpi_video0.service failure?

Edit: Just looked at https://wiki.archlinux.org/index.php/Backlight#ACPI. When I run

[morten@thinkpad ~]$ ls /sys/class/backlight/
amdgpu_bl0

it shows that amdgpu_bl0 handles my backlight instead of acpi_video0, so maybe acpi_video0 is just a misnomer on my computer? Maybe the service failure comes because it's using amdgpu_bl0 instead?

Last edited by morten (2021-02-06 00:24:25)

PBS

Member

Registered: 2015-06-28

Posts: 53

Re: Systemd backlight services failing

For me the problem disappeared after enabling Early KMS for the amdgpu driver.

Now my systemctl status is error-free, so I can sleep again