Arch Linux

mankmonjre

Member

Registered: 2014-07-16

Posts: 8

Screen brightness reset to maximum, when un/plugging power cord

I am running Arch linux on Thinkpad Carbon X1 (gen 2). Whenever I plug in or unplug the power cord, the screen brightness is instantly reset to maximum. The problem also occurs when I have disabled any power management tools (tlp, kde). Please suggest possible agents causing the issue.

peschkaj

Member

From: Portland, OR

Registered: 2014-07-06

Posts: 16

Website

Re: Screen brightness reset to maximum, when un/plugging power cord

I'm running into the same problem on a Lenovo W540 - the brightness resets to full. Not sure if this is specific to Lenovos or something bigger.

Gulver

Member

Registered: 2013-05-24

Posts: 208

Re: Screen brightness reset to maximum, when un/plugging power cord

Screen brightness are configured distinctly as plugged or unplugged. Just like volume is different for plugged or speakers. If your problem is about not saving the last amount of brightness from last usage, that has to do with your DE if you are using GNOME. There is also a systemd service but that only handles for the boot process as far as I know.

mankmonjre

Member

Registered: 2014-07-16

Posts: 8

Re: Screen brightness reset to maximum, when un/plugging power cord

Screen brightness are configured distinctly as plugged or unplugged. Just like volume is different for plugged or speakers. If your problem is about not saving the last amount of brightness from last usage, that has to do with your DE if you are using GNOME. There is also a systemd service but that only handles for the boot process as far as I know.

I don't think that this problem has to do with the DE, since this happens even when I do not start the DE. Also, if enabled, the DE settings kick in after a second the brightness has increased. It could be an issue with the drivers, as the change occurs almost instantly.

Gulver

Member

Registered: 2013-05-24

Posts: 208

Re: Screen brightness reset to maximum, when un/plugging power cord

Then it is systemd files.

mankmonjre

Member

Registered: 2014-07-16

Posts: 8

Re: Screen brightness reset to maximum, when un/plugging power cord

Could you pleae tell which systemd files are relevant? I masked systemd-backlight@backlight:intel_backlight.service, with no change in behavior.

Gulver

Member

Registered: 2013-05-24

Posts: 208

Re: Screen brightness reset to maximum, when un/plugging power cord

I'm not sure how to diagnose it and it may not be sufficient to just disable them. There is, for example an acpi unit in my system. follows as:

 systemd-backlight@backlight:acpi_video0.service      systemd-backlight@backlight:intel_backlight.service                                                     
systemd-backlight@backlight:acpi_video1.service      systemd-backlight@.service 

Try to tinker it is content if disabling it simply doesn't work since there are services in systemd that you cannot simply turn off and they are enabled automagically upon every boot.

bio

Member

Registered: 2013-11-22

Posts: 8

Re: Screen brightness reset to maximum, when un/plugging power cord

i tried to open defect on kernel... But kernel developers won' t fix...
happens from kernel >= 3.13

https://bugzilla.kernel.org/show_bug.cgi?id=65601

stbinan

Member

Registered: 2013-11-18

Posts: 8

Re: Screen brightness reset to maximum, when un/plugging power cord

I also encountered backlight being reset to maximum everytime my laptop restarted. I disabled and stoped acpi_video1.service with

#systemctl stop systemd-backlight@backlight:acpi_video1.service

and

#systemctl disable systemd-backlight@backlight:acpi_video1.service

, then backlight worked fine again! I checked the systemctl and acpi_video1.service was still active. Maybe some configs went wrong during update, and disabled and stoped systemd-backlight service those configs would be reset.