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fiona float 🐈's posts Post Back to profile
fiona float 🐈

fyi, since many people don't know this exists:
Almost all computer screens made in the last decade support DDC/CI. (The Display Data Channel Command Interface).
You can use it to control stuff like the backlight brightness without fiddling with the awful screen buttons and OSD.

On Linux once you load the ddcci kernel module the screens appear in /sys/class/backlights and can be controlled like a laptop screen.

screenshot of a terminal showing the following: sudo modprobe ddcci ls /sys/class/backlight it shows the internal laptop screen and ddcci11. Then I cat the value of /sys/class/backlight/ddcci11/brightness and it shows 100 then I show that brightnessctl can control the screen.
2 Feb 2023 at 11:17 | Open on chaos.social
6 comments
fiona float 🐈

Now you can go ahead and map the screen brightness to media keys on your keyboard, write a script to adapt it to the sunrise/sunset or even connect it to your Home Assistant.

Oh, and I'm sure that there are tools for other OSes as well. I know that I used one on MacOS years ago.

2 Feb 2023 at 11:20 | Open on chaos.social
SEGFAULT

@vidister what distro did you do this on? I didn't fi?d the module on fedora

2 Feb 2023 at 13:09 | Open on oldbytes.space
fiona float 🐈

@SEGFAULT On NixOS there's `linuxKernel.packages.linux_<version>.ddcci-driver` and I heard there's an AUR package for Arch.

Chances are you have to build it yourself: gitlab.com/ddcci-driver-linux/

2 Feb 2023 at 13:12 | Open on chaos.social
you found aurelia

@vidister wasn't there like a handful of displays that can be bricked with it too or was that just a false rumor?

I really wish mine (LG 27GL850, not even that old) supported source switching, but it doesn't :/

2 Feb 2023 at 11:44 | Open on chaos.social
Danu

@vidister @aurelia uff there are many posts with various problems related to this feature :(

2 Feb 2023 at 12:08 | Open on chaos.social
trilader

@vidister Thank you for that information. It works great with my Dell monitors from around 2015. On Arch this module is available as ddcci-driver-linux-dkms in the AUR. I thought it wasn't enabled as first as I didn't think it was an out-of-tree one

2 Feb 2023 at 11:58 | Open on chaos.social
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