Arch Linux

kryo1

Member

Registered: 2024-06-11

Posts: 1

Monitor Brightness Issue

Hello everyone, first time poster here.

I'm encountering a weird monitor brightness issue. I suspect that either a kernel update, or me enabling the i2c kernel modules have allowed some process on my machine to change my monitors' brightness values over DisplayPort. This now automatically happens on suspend. The problem is, that my monitors have different values for the max brightness, which causes monitor 2 to be set the wrong max value after suspend (It stays dark). I found this out via the following commands (I can also use the setvcp variants as a quick fix, but it's getting annoying)

 
$ ddcutil getvcp 10
VCP code 0x10 (Brightness                    ): current value =   100, max value =   100

$ ddcutil getvcp 10 -d 2
VCP code 0x10 (Brightness                    ): current value =   255, max value =   255

I'd be glad to try and submit a patch for fixing this behavior, but I have no idea how to find out which piece of software is responsible. So my question is: How would I go about figuring this out?

For reference: I'm using the latest version of KDE and the amdgpu driver.

Cheers,
kryo

seth

Member

From: Won't reply 2 private help req

Registered: 2012-09-03

Posts: 75,979

Re: Monitor Brightness Issue

I suspect that either a kernel update, or me enabling the i2c kernel modules have allowed some process on my machine to change

* test the LTS kernel
* blacklist the relevant i2c modules
* try to only boot the multi-user.target (2nd link below) and suspend from there resp. some other session than KDE (eg. openbox)

---

How to upload text · How to boot w/o GUI · Disable Windows Fast-Start! · Fix your xinitrc