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Antonius

Member

Registered: 2023-03-16

Posts: 2

Nvidia brightness control with nvidia_0

Hello, I am unable to adjust the backlight of my laptop using an Nvidia graphics card, proprietary drivers (525.89.02), KDE Plasma, GRUB, Dell Precision 7760.

ls /sys/class/backlight/
nvidia_0

/etc/X11/xorg.conf.d/*nvidia.conf has

Option "RegistryDwords" "EnableBrightnessControl=1"

and as for kernel parameters in grub under /etc/default, I've tried each, and both arguments:

GRUB_CMDLINE_LINUX="nvidia-drm.modeset=0 nvidia.NVreg_RegistryDwords=EnableBrightnessControl=1"

But I've read that Nvidia removed this functionality from their drivers at some point. The only ways that I'm able to change perceived brightness is through the Nvidia X Server settings, and xrandr, nothing else has worked from the wiki backlight page. But those are not optimal, when a few months ago, with what I set above, I was able to raise/lower backlight brightness through my keyboard's brightness keys. I updated my system, and it hasn't worked ever since.

I can't find recent threads of people in the same scenario, many have acpi_0 instead of nvidia_0, or some combination of controllers. I can "raise/lower" the brightness using my keyboard, and the Plasma brightness bar will go up/down, and the values will reflect that within the nvidia_0 directory, but the display will not actually change.
Does anyone have any suggestions?

Last edited by Antonius (2023-03-16 22:40:30)

radiomike

Member

Registered: 2013-12-19

Posts: 71

Re: Nvidia brightness control with nvidia_0

Do you have an iGPU that's disabled in bios?

Antonius

Member

Registered: 2023-03-16

Posts: 2

Re: Nvidia brightness control with nvidia_0

Do you have an iGPU that's disabled in bios?

Indeed, dGPU only. Hybrid graphics is disabled.

Last edited by Antonius (2023-03-18 06:17:08)

radiomike

Member

Registered: 2013-12-19

Posts: 71

Re: Nvidia brightness control with nvidia_0

I think you'll need to enable the igpu to get backlight control.
As I understand it, the backlight gets associated with the card that it's attached to. In most optimus set ups that's the igpu, and that remains the case even when that device is disabled in bios. In order to control it you need the igpu drivers loaded, unfortunately disabling hybrid graphics means those drivers don't get loaded.
If you haven't already check the wiki for various options to set up optimus systems.