Arch Linux

slowhand

Member

Registered: 2020-10-08

Posts: 3

Can't change brightness in Arch [solved]

I'm new to Arch and I had dual-booted it using grub with i3 and X in my Hp Envy 15 2020 with RTX 2060 Max Q and intel gpu 2 weeks back. I used Optimus-Manager with X to install. It is currently set at intel. But I can't change my brightness with the Backlight managers given in the Arch wiki. Although xbacklight updates intel_backlight/brightness, there is no change in the brightness. I am using xrandr for now and it works, but it is not exactly efficient battery-wise considering it alters perceived brightness and it cannot be changed via shortcuts. I tried light and brightnessctl but no luck.

I thought adding option "Backlight" would be a fix but I can't update the 10-optimus-manager.conf file as it reverts back to its previous version after reboot.
For now this is what it contains

Section "Device"
        Identifier "intel"
        Driver "modesetting"
        BusID "PCI:0:2:0"
        Option "DRI" "3"
EndSection

Can anybody suggest a solution? Thank you.

Last edited by slowhand (2021-01-19 13:53:01)

Ropid

Member

Registered: 2015-03-09

Posts: 1,069

Re: Can't change brightness in Arch [solved]

I tried looking up details about your laptop. It seemed to me it has an "OLED" display. Try looking up something about Linux and OLED and the Intel graphics driver to find out what's going on there.

OLED displays do not have a backlight. The pixels themselves are where the light is created. This means the graphics driver needs a special internal preparation to translate the things that xbacklight does into a changed brightness for the display.

You say you are using xrandr right now and you think that's not helping battery: this should be wrong because of how OLED works. With OLED it's not just the perceived brightness you are changing when you make the graphics darker, you are actually changing the real brightness because there is no backlight.

Maybe using xrandr is totally fine and you don't have to worry? I don't know if there is downsides to using xrandr. Maybe it reduces the value range of the pixel colors and then introduces color banding? There's a test image here with a grayscale gradient:

http://www.lagom.nl/lcd-test/gradient.php

That gradient should look perfectly smooth with no banding.

Last edited by Ropid (2020-10-09 05:25:51)

slowhand

Member

Registered: 2020-10-08

Posts: 3

Re: Can't change brightness in Arch [solved]

Ah, that might explain why brightness control don't work in any of the distros installed. I should have specified the screen type there. I had fedora installed earlier before removing it to install Arch and I had the same problem though I did not look into solving it then. Should I try switching to Nvidia or should I stick with Intel?
The gradient test looks smooth but the reason I came to the conclusion about xrandr is based on what I read here and also the frequency of using charger compared to windows.
Also my device heats up pretty quick compared to windows during browsing sessions so I think maybe it is not just the brightness. I should probably look into it. Thanks for the help.
Also I need a fix on the adding Options in the 10-optimus-manager.conf. I can't keep the changes permanent. I tried creating a xorg-intel file as given in their wiki but no luck. Am I missing something that should be done after making these changes? I generally reboot after saving the changes made from root; unless some specific command is specified to be run afterwards in the wiki.

Last edited by slowhand (2020-10-09 07:40:06)

euromatlox

Member

Registered: 2017-02-10

Posts: 153

Re: Can't change brightness in Arch [solved]

You can check also this earlier discussion about the issue with OLED.

Last edited by euromatlox (2020-10-09 08:35:17)

slowhand

Member

Registered: 2020-10-08

Posts: 3

Re: Can't change brightness in Arch [solved]

Thanks for the help y'all.

Also any suggestions on the optimus-manager problem?