Out of the box on an Arch Linux setup, KDE can control my Gaming PC’s displayport monitor brightness. NixOS does not do this. What is the missing package/setting?
I think acpilight is what you want - provides xbacklight
Display brightness appears in the KDE bar now however it prints
“Error:
/run/current-system/sw/bin/python3: No module named ddcci_plasmoid_backend”
We’re getting somewhere! That’s awesome!
Mine just works -I don’t remember addin anything special…I am on unstable with Plasma 6.0.5, frameworks 6.3.0 and Qt version 6.7.1. Does that match your setup?
Are you also using an external monitor and if so which brand gpu?
I have the same situation as @Bitcoin21 where it worked ootb on Endeavour.
It would seem that you just need powermanagement.enable but after checking out the Powerdevil repo readme seeing that ddcutil is required but the only reference to ddcutil in a kde/plasma file in nixpkg is this kde-maintainer script not requiring ddcutil.
Kind of just seems like the monitor stuff isn’t supported altogether and I’m going to have to learn how this is packaged.
Running NixOs Unstable with:
Plasma: 6.10
Frameworks: 6.30
Nvidia 3070: 555.52.04
That’s what it was,
ddcutil is just not required for the powerdevil build. Just need to add it as a buildInput and the build will pick it up and monitor brightness should be available after maybe a service reload or log{in,out}?
I ended up just restarting I think.
There might be a simpler way but I’ve used overlays so it’s the hammer I’ll use: nixos overlay: include ddcutil in powerdevil build · GitHub
After getting this going though I think I’m still gonna stay with vdu_controls (has scheduling) and give ddcci-plasmoid a run (used to use this one prior to plasma6)
Hopefully it’s the same issue for you @Bitcoin21 as Arch’s package has ddcutil as a hard dep.
As soon as I figure out overlays I’ll let you know! 
The wiki has a solid explanation but it clicked with some other fixes I’ve grabbed online.
Only requires a few lines, they’re in my first link.
This solved!!
Do we open a ticket next?
Thank you!
It works OOTB on my laptop but not to the external dP monitor on my gaming rig. Solved with above.
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Possibly, was planning on doing some research into these kind of “optional” things.
Packages don’t really have settings and then on the options side there’s some ambiguity on a “best place”. Basically does it need a whole programs.powerdevil.* or just simply an option for services.desktopManager.plasma6.ddcutil 
But I think the first thing to check is why is it explicitly ignored as a dependency.
There’s been some issues with powerdevil and ddcutil historically where new versions cause issues, etc. I think that may be the root of the ignore and possibly if things have gotten more stable it can be re-introduced.
But for some these issues end up being pretty bad, like recurring system lag and what I’ve noticed myself with Nvidia cards is when ddcutil queries or sets values all my outputs experience frame drops/stuttering.
I clicked through to the ddci build-time stuff. Looks like the maintainer thinks it’s cursed! 
