I have a display (OLED) that I actually want to use software brightness for. I know Plasma/Wayland has a mechanism for this because one of my systems just does it…..
This display lacks proper DDC controls, it’s kind of a custom job. On my Desktop running Manjaro/KDE/Wayland it just knows to use software brightness, presumably because powerdevil failed to poke it with DDC. journalctl shows something like this:
org_kde_powerdevil[4411]: [ 4585] Emitting DDCA_Display_Status_Event[4499.677: DDCA_EVENT_DISPLAY_CONNECTED, card1-DP-3, dref: DDCA_Display_Ref[8], io_path:/
dev/i2c-8, ddc working: false]
I don’t believe I installed or set anything extra, it just shows up with a brightness slider and the gamma job on an OLED is perfectly convincing so all is well.
On another Fedora based system this doesn’t happen. It may be because the GPU driver is preconfigured and it’s an eDP interface so it thinks there is a backlight to control because one is present in /sys/class/backlight.
I tried a couple of things like editing plasma-powerdevil.service with:
[Service]
Environment="POWERDEVIL_NO_DDCUTIL=1"
That didn’t work. Anyone have a suggestion?
I have KDE Plasma 6.4.3, and I can switch between software-based brightness changes in System Settings => Display & Monitor => Display Configuration => Control hardware brightness with DDC/CI
@katze_942 is that connected via eDP (usually Notebook/Tablet internal display)?
Because that switch is what I thought first as well but it does on 6.4.4, at least for me, only exist for my external Monitors not for the (non-HDR) eDP one and the OP asks specifically about eDP (Hardware brightness control works in my case, though).
Well KDE can be configured to do alot of things the problem is no one knows how it does it. I’ve never seen that specific checkbox but on my Manjaro KDE box it just knows it has to use software brightness on a specific display and it knows it has to use DDC on all the rest.
The problem is on 1 system running a Fedora based distro it has remnants of the stock display in the GPU driver or whatever so it has a /sys/class/backlight device present. I think that’s what causes KDE to skip the software brightness fallback because a backlight device is more or less a pre-managed control by whatever thing created it, so it’s presence usually means the backlight is controlled by an embedded controller or something that DDC, etc can’t query or control, so they just skip it….something else is dealing with it.
So I’d like to figure out a method of getting KDE to pretend the backlight device doesn’t exist, that may just do the trick. Otherwise the least intrusive means of just getting it to use software/gamma control
