Lenovo a275 dims screen until reboot when the charger is pluged/unpluged


New Member
I run arch with bspwm on a Lenovo a275 using amdgpu drivers and i am very new to linux. I can adjust screen brightness with the xrandr --output MONITORNAME --brightness VALUE command.

This works fine on battery and with the charger connected. But when I plug/unplug the charger the screen dims significantly, and it cannot be brought up to full brightness with the above xrandr commands. Also the same values for above command produce different (noticeable less bright) results.

The screen also dims when I am still in tty. In tty I assume those xrandr commands are useless anyway, just noted that the dimming happens too without x running.

Using values greater than 1.0 to force more brightness after I plug/unplug results in higher contrast, but not higher brightness.

Rebooting brings everything back to normal, but it is annoying to be forced to do this. Is there a way I can "reset" my screen brightness to normal from the cli or stop the system to adjust screen brightness automatically every time plug or unplug?


New Member
Thanks. I am trying the acpi commands atm. Had to install udev. My main user is member of the following groups:

video storage optical audio wheel.

I added this line from the wiki to backlight.rules:

ACTION=="add", SUBSYSTEM=="backlight", KERNEL=="acpi_video0", GROUP="video", MODE="0664"

but replaced acpi_video0 with amdgpu_bl0

I had to create this file, there is nothing in it except the line copied from the wiki. So far I am unfamilar with everything concerning udev and I don't know how if this is sufficient to make it work.

Changing the backlight with the acpi commands works when loged in as root, but not when loged in as my main user. When I try to use the echo VALUE > /sys/class/backlight/amdgpu_bl0/brightness command I get a permission denied error. Even when I sudo this command I get a permission denied.

Edit: Just realized that I can log in to another tty as root to reset brightness without rebooting, but it is not very elegant. Has anyone a idea why I get a permission denied when I try to use the acpi command although my main user is in wheel and video?
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