@karolherbst @elly the KDE thing uses the user space ddd/ci libraries which requires i2c-dev and screwing up permissions on the device. some apple displays have a usb thingy for it instead of the i2c ddc/ci.

we could wire all of that up but because it requires a kernel module which is clearly not meant to be used in production and has issues with permissions, that never seemed like a good idea.

there were efforts to create a sysfs backlight from ddc/ci in the kernel but hans degoede didn't want to expose them because it could screw up the existing logic to bind a sysfs backlight to a display.

there is an out of tree kernel module which does this, but it can't properly autodetect ddc/ci, so you still have to much around and write magic values into sysfs to make it work. once you do that, you get a sysfs backlight and mutter will pick it up and bind it to the right monitor.

the realistic path forward is exposing backlights in KMS. it's new API, can't screw up existing sysfs user space, and fixes the issue with binding the backlight to a specific display (and a whole lot of other things). buuut, hans is now only doing camera stuff and mario limonciello wanted to work on this but probably has more important things to do.