Created attachment 171090 [details] output of ddcutil capabilities for both monitors SUMMARY In Plasma 6.0 (Wayland) I was able to control both my monitors brightnesses over DDC. After updating to Plasma 6.1 the brightness slider only dims my primary monitor, and leaves both monitors brightness setting unchanged. Notably my second monitor (Dell U2312HM) was affected by #484037 ( https://bugs.kde.org/show_bug.cgi?id=484037 ) SOFTWARE/OS VERSIONS Fedora Version: 40 Kernel: 6.9.5-200.fc40.x86_64 (64-bit) KDE Plasma Version: 6.1.0 KDE Frameworks Version: 6.3.0 Qt Version: 6.7.1 ADDITIONAL INFORMATION Some ddcutil capabilities info about the monitors are attached. If any more info is needed, feel free to ask. Monitors are DELL U2312HM and LG ULTRAGEAR 27GL850-B.
This is almost exactly the same issue i have too, except it seems to be a combination of this bug and bug 482713 Brightness control on my primary monitor is always available, but it disappears at random on my secondary monitor at boot, and then it's the same as this bug. I wonder if you would also have brightness control on your second monitor at random if you kept rebooting. Primary: Svive Pyx 34C601 Secondary: Philips Momentum 3000 27M1N3500LS (Both are using DisplayPort 1.4)
I think I'm running into this issue too, under Plasma 6.3 on Wayland. I have two identical Dell U2417H monitors connected over DisplayPort. ddcutil can control brightness on both monitors with `ddcutil -d <n> setvcp 10 <0-100>` for n=1 or 2. But KDE only shows a brightness control for one of them (oddly, the one that ddcutil sees as display 2). When I swap cables and monitors between DisplayPort outputs, or use only one monitor, the problem stays with the monitor. I have factory-reset both monitors just to make sure it is not a configuration issue. If it wasn't for the fact that ddcutil detects VCP 10 and can control the brightness both monitors just fine, I would chalk it up to that particular monitor having an issue. But IMO, if ddcutil can talk to it, KDE should be able to as well.
I'm sorry we weren't able to get to this report before now. Is this still happening with Plasma 6.3.2? There have been some improvements in this area.
(In reply to haavardandree from comment #1) > Brightness control on my primary monitor is always available, but it > disappears at random on my secondary monitor at boot, and then it's the same > as this bug. The brightness control disappearing sounds like bug 465256. If this is still happening for anyone, can you copy and paste the output of this to that report? kscreen-doctor -o
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(In reply to TraceyC from comment #3) > I'm sorry we weren't able to get to this report before now. Is this still > happening with Plasma 6.3.2? There have been some improvements in this area. Apologies for not responding sooner! I recently updated to 6.3.3, and yes, brightness control seems to work as expected for me across multiple displays now. Thanks a lot!
Thanks! Tjado, do you experience the same improvement with Plasma 6.3?
Hi again. I got the time to check now. The issue definitely changed. I have brightness sliders for both monitors now. On Plasma 6.3.3, my secondary monitor (DELL) works perfectly. My primary monitor is detected, however the brightness control seems to fall back to darkening every pixel on screen or something. I started using Luminance ( https://github.com/sidevesh/Luminance/releases ) which can control both monitors correctly via DDC. So the issue is not with the monitor not offering the capability. I think this is still related to the original issue, as my primary monitor can still not be controlled via DDC.
(In reply to Tjado Edzards from comment #8) > Hi again. I got the time to check now. > > The issue definitely changed. I have brightness sliders for both monitors > now. > > On Plasma 6.3.3, my secondary monitor (DELL) works perfectly. > > My primary monitor is detected, however the brightness control seems to fall > back to darkening every pixel on screen or something. Well darn. I'm sorry to hear this is still troublesome for you. Can you send a screen recording, or a recording from your phone, of what happens when you try to change brightness on the primary monitor? Thanks.
That "darkening every pixel" is software brightness being applied, this happens when hardware brightness control has never been detected for a screen. So either powerdevil never offers a brightness device for the second display, or KWin never assigns it to the correct display internally. Can you run powerdevil with WAYLAND_DEBUG=1, and post the output of that here? Should work like this: > killall org_kde_powerdevil; WAYLAND_DEBUG=1 /usr/lib64/libexec/org_kde_powerdevil
While tinkering around on unrelated stuff, I found myself in a Live USB of Fedora 41 and Fedora 42 with older Plasma versions (at least 6.2 and 6.3.2 respectively). There, brightness controls worked correctly. I am confused now as the problem seems to be in front of the display. Upon that, I already tried reinstalling powerdevil to no success, so it seems to be that my powerdevil config (if it exists) maybe got corrupted in an update between Plasma 6.0 and 6.1? Reinstalling Fedora is not really an option for me, and I don't know where a configuration to delete would be stored or if there is any other way to go about this. (In reply to Zamundaaa from comment #10) > That "darkening every pixel" is software brightness being applied, this > happens when hardware brightness control has never been detected for a > screen. > So either powerdevil never offers a brightness device for the second > display, or KWin never assigns it to the correct display internally. > > Can you run powerdevil with WAYLAND_DEBUG=1, and post the output of that > here? Should work like this: > > killall org_kde_powerdevil; WAYLAND_DEBUG=1 /usr/lib64/libexec/org_kde_powerdevil My logs (Startup and commented, the lines added after changing the brightness) https://notebin.de/?8bef324d0b87d96a#5Gk1DbpGHc8ThZKyz8qMzDTM8PL75ZMTqH18BQwwnSei