Bug 494577

I can confirm this on the same setting (Fedora 40 with all updates) but DELL monitors. One has to set brightness every time.

I can confirm this issue as well with multiple systems and setups. I'm running archlinux.

In my case it is not happening on my home desktop (same configuration) but a single monitor. Is this true for everyone?

for me it happens with all external monitors independent of the manufacturer. the brightness can be restored manually by changing the value in brightness app which indicates that the value corresponding value is not considered after the wakeup.

By external monitor you mean you are using a laptop with an external monitor?

yes, that's correct

I have the same issue on my desktop using a single Dell monitor.

Same here: external monitor gets to 80% brightness each time I reboot.

My configuration is:
- Operating System: Fedora Linux 40
- KDE Plasma Version: 6.2.3
- KDE Frameworks Version: 6.8.0
- Qt Version: 6.7.2
- Kernel Version: 6.11.6-200.fc40.x86_64 (64-bit)
- Graphics Platform: Wayland
- Processors: 12 × AMD Ryzen 5 5625U with Radeon Graphics
- Memory: 14.4 GiB of RAM
- Graphics Processor: AMD Radeon Graphics
- Manufacturer: LENOVO
- Product Name: 21ED004NSP
- System Version: ThinkPad E15 Gen 4

Monitor: Dell Inc. DELL U2415

Please, let me know if you would need extra information about the issue.

Upgraded to Fedora 41, same issue !

That's a lot of confirmations. I wonder if you are all hitting the same issue, or if they are slightly different.

The original bug report mentions that the brightness slider doesn't work as expected anymore, "the monitor doesn't brighten beyond the dimmed value". This would happen if hardware brightness controls are lost and KWin on Wayland uses software brightness instead. There was a change that went into Plasma 6.2.3, which will make sure that the slider disappears instead of now confusingly controlling software brightness: https://invent.kde.org/plasma/kwin/-/merge_requests/6670. But this does not fix the underlying issue that Plasma gave up on hardware brightness controls.

There was another change that went into 6.2.1, which will retry any monitor commands several times (spaced out over a few seconds) before giving up on hardware brightness: https://invent.kde.org/plasma/powerdevil/-/merge_requests/441 plus a small addition for completeness, https://invent.kde.org/plasma/powerdevil/-/merge_requests/445.

The initial bug report was reported against Plasma 6.2.0 - could I ask for confirmation from the OP (hossainsany@proton.me) to report if this is still failing for you?

Other comments are mentioning that non-dimmed brightness needs to be restored by adjusting the slider in the brightness applet. This indicates that hardware brightness controls are generally working, so the root cause would be different from the originally reported issue. I improved the dimming code somewhat in Plasma 6.2.1 by restoring brightness values for each display individually: https://invent.kde.org/plasma/powerdevil/-/merge_requests/433. However, this isn't yet good enough if a dimmed monitor was unplugged and only comes back later. We need to further improve robustness for un-dimming monitors. Also see: https://invent.kde.org/plasma/powerdevil/-/issues/38

I am at frameworks 6.8.0, plasma 6.2.3, apps 24.08.3 on Fedora 41. This is only happening on my dual monitor desktop, not on my home desktop with a single monitor (all DELL but different models, the dual monitors are the same model). When screen goes to sleep and you wake it up with mouse movement (no locking) the screens are dimmed. Brightness slider still shows the brightness at the original setting.
Moving the slider slightly restores the brightness.

(In reply to Jakob Petsovits from comment #10)
> That's a lot of confirmations. I wonder if you are all hitting the same
> issue, or if they are slightly different.
> 
> The original bug report mentions that the brightness slider doesn't work as
> expected anymore, "the monitor doesn't brighten beyond the dimmed value".
> This would happen if hardware brightness controls are lost and KWin on
> Wayland uses software brightness instead. There was a change that went into
> Plasma 6.2.3, which will make sure that the slider disappears instead of now
> confusingly controlling software brightness:
> https://invent.kde.org/plasma/kwin/-/merge_requests/6670. But this does not
> fix the underlying issue that Plasma gave up on hardware brightness controls.
> 
> There was another change that went into 6.2.1, which will retry any monitor
> commands several times (spaced out over a few seconds) before giving up on
> hardware brightness:
> https://invent.kde.org/plasma/powerdevil/-/merge_requests/441 plus a small
> addition for completeness,
> https://invent.kde.org/plasma/powerdevil/-/merge_requests/445.
> 
> The initial bug report was reported against Plasma 6.2.0 - could I ask for
> confirmation from the OP (hossainsany@proton.me) to report if this is still
> failing for you?
> 
> Other comments are mentioning that non-dimmed brightness needs to be
> restored by adjusting the slider in the brightness applet. This indicates
> that hardware brightness controls are generally working, so the root cause
> would be different from the originally reported issue. I improved the
> dimming code somewhat in Plasma 6.2.1 by restoring brightness values for
> each display individually:
> https://invent.kde.org/plasma/powerdevil/-/merge_requests/433. However, this
> isn't yet good enough if a dimmed monitor was unplugged and only comes back
> later. We need to further improve robustness for un-dimming monitors. Also
> see: https://invent.kde.org/plasma/powerdevil/-/issues/38

Hi, after upgrading to Fedora 41, the issue has been resolved for me. The monitor brightness now behaves correctly after waking up.

Current software versions:
    KDE Plasma Version: 6.2.3
    KDE Frameworks Version: 6.8.0
    Qt Version: 6.8.0
    Kernel Version: 6.11.7-300.fc41.x86_64 (64-bit)
    Graphics Platform: Wayland

Thank you for the updates and improvements!

Is this a singe monitor or dual monitor? single monitor systems are behaving correctly for me too but not the dual monitor system.

Just noticed that you are on Wayland....I am on X11 perhaps this is a hint.

(In reply to S. Umar from comment #13)
Mine's dual monitor from different brands, one is LG and the other is Asus. I was having the issue on the LG monitor.

Thanks for the quick response(s). If the originally reported issue is working now for the reporter, I think it's best to close this bug as fixed so that we don't end up discussing subtly different issues in here, when those issues are hard to tell apart from each other.

Everyone who is still experiencing a related bug, please open a new bug report for your particular setup and reproduction steps. You can also check if any of the other reported issues are a close match and follow those instead - here's the link to all open PowerDevil bugs which would include brightness control issues:

https://bugs.kde.org/buglist.cgi?bug_status=UNCONFIRMED&bug_status=CONFIRMED&bug_status=ASSIGNED&bug_status=REOPENED&list_id=2900442&product=Powerdevil&query_format=advanced

Thank you, and sorry for the hassle.