nvidia geforce - Brightness control in FreeBSD 10.3 RELEASE on Dell XPS L702X

Tuesday, 4 February 2020

nvidia geforce - Brightness control in FreeBSD 10.3 RELEASE on Dell XPS L702X

I am trying to change the screen brightness.

I've already tried:

Loading acpi_video with kldload.

The module loads fine however sysctl hw.acpi.video prints only:

sysctl: unknown oid 'hw.acpi.video'

Adding Option "RegistryDwords" "EnableBrightnessControl=1" to the Device section. It doesn't work. Rebooting didn't help.

Running xbacklight(1).

Installing nvidia-settings. It seems like I cannot control the brightness from there.

Details

uname -a returns:

FreeBSD pc 10.3-RELEASE-p4 FreeBSD 10.3-RELEASE-p4 #0: Sat May 28 12:23:44 UTC 2016 root@amd64-builder.daemonology.net:/usr/obj/usr/src/sys/GENERIC amd64

The machine is Dell XPS L702X.

The graphic card is NVIDIA GT550M.

I use an external Samsung 2043NW display.

Related threads

Answer

I wasn't able to use xbacklight(1) and activate the brightness control keys but I've found a couple of other ways to change the brightness:

xrandr(1)

Thanks to How to change LCD intensivity/brightness I was able to change the brightness of the external monitor using xrandr. The command looks like this:
```
xrandr --output HDMI-0 --brightness 0.9
```
The default value seems to be 1.

redshift(1)

Redshift is a software allowing you to change the temperature of your screen. It has -b, -t and -g options which might come handy (see man redshift for more details).

One way or another, I would still like to know if it is possible to use xbacklight on this machine.

It looks like the problem with colors might be caused by the fact that I connect the monitor over a VGA-HDMI adapter. HDMI seem to mess up the colors of a connected monitor this way.

I've found a solution to this problem: Yellow and gray blend with white on a remote monitor connected with a HDMI-VGA adapter

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