I have a desktop connected to two external monitors. I usually change the brightness and contrast of these monitors multiple times a day and I’d like to have an easy way to change the brightness and contrast.
However, I’d rather have a slider I can adjust. This other answer states that the ddcci-backlight module should enable the brightness slider:
The DDC/CI kernel module includes a
ddcci-backlightmodule which can integrate most DDC/CI-capable monitors into the kernel’s backlight system (
/sys/class/backlight). This allows any tool which can use the latter to drive the backlight on a DDC/CI monitor.
The Arch Linux wiki states something similar:
After some googling I found the ddcci-driver kernel module, which I enabled by including
boot.extraModulePackages = with config.boot.kernelPackages; [ ddcci-driver ];
in my configuration.nix. However, this doesn’t change anything. No slider shows up in the power management, and when I install acpilight and try to change the brightness it seems to have no effect. Also, when I list the devices no monitor seems to show up:
ruben@nixos> sudo xbacklight -l ~ input0::compose input0::scrolllock input0::kana input0::capslock input0::numlock
I haven’t done anything with kernel modules before and it feels like I’m missing steps here. Is there anyone who got brightness control for external monitors working on NixOS? I can’t imagine that I’m the only one who wants this, yet I can barely find any information on it.