On 1/23/2018 8:02 AM, Foxtrot Mike via arch-general wrote: > I tried googling this error, but didn't find anything helpful. > > So I tried using xbacklight instead. It didn't give any positive results either, even when I provided different kernel paramters as discribed in [1]. No matter what I do with acpi and kernel parameters, "/sys/class/backlight/acpi_video0/brightness" doesn't give actual values. Also, 'xbacklight set' has no effect on screen brightness at all. > > I also tried adding `Option "RegistryDwords" "EnableBrightnessControl=1"` in "/usr/share/X11/xorg.conf.d/10-nvidia-drm-outputclass.conf". Still keyboard brigthness keys couldn't change the brightness. > > Can someone help me get ddcutil working with nvidia proprietary driver? I doubt I can held get ddcutil working, but the problem is a lack of an nvidia kernel module interface with /sys/class/backlight (which can be frustrating). You do not want to use xbacklight -- which ironically does not control actual backlight (display power), but instead controls pixel darkness (the amount of black/white per-pixel). Reducing backlight does not reduce display power, it just makes the pixels darker giving the impression of reduced brightness. (this is really bad for laptop battery life where reducing the display power is important) You want xrandr. Query with `xrandr -q` and find your interface and you can then set the desired brightness with something similar to xrandr --output LVDS-0 --brightness 42 (where LVDS-0 is your monitor connections shown by --query) Modern desktops generally integrate xrandr control (if not, you can simply implement a short script that allows you to check and set the desired brightness. There were also several AUR packages (nvidia-bl, and nvidiabl or similar) that provided a /sys/class/backlight kernel module that would would work with most laptops, but I don't think they are maintained any longer. (there was an example script on the X11 wiki some time ago for doing this) That is another option. -- David C. Rankin, J.D.,P.E.
