Bug 510294

Summary:	Laptop brightness is higher than indicated in brightnessctl
Product:	[Plasma] plasmashell	Reporter:	slartibart70
Component:	Power management & brightness	Assignee:	Plasma Bugs List <plasma-bugs-null>
Status:	REPORTED ---
Severity:	normal	CC:	kde, kdedev
Priority:	NOR
Version First Reported In:	6.5.80
Target Milestone:	1.0
Platform:	Fedora RPMs
OS:	Linux
See Also:	https://bugs.kde.org/show_bug.cgi?id=503268
Latest Commit:		Version Fixed/Implemented In:
Sentry Crash Report:

Description slartibart70 2025-10-06 11:03:12 UTC

I have a laptop and external 4K screen.
Laptop is setup as having 30% screen brightness in 'power management > display and brightness'

This setting was working ok (reproducible brightness) but is now lost after sleep/standby.
The systray-brightness slider still says  30%, but the screen is noticeable brighter.
Just touching the slider 'fixes' the effective brightness immediately (so i set it back to point to exactly 30% again)

I did not yet check the output of 'brightnessctl info' directly after resume (will do...)

One more thing:
in power management > display and brightness' i can only preset the brightness for the laptop screen, not for the secondary monitor - although in systray we have two brightness sliders. Is this intentional?

Comment 1 slartibart70 2025-10-06 11:04:01 UTC

Operating System: Fedora Linux 42
KDE Plasma Version: 6.5.80
KDE Frameworks Version: 6.20.0
Qt Version: 6.9.2
Kernel Version: 6.16.10-200.fc42.x86_64 (64-bit)
Graphics Platform: Wayland
Processors: 16 × AMD Ryzen 7 PRO 7840U w/ Radeon 780M Graphics
Memory: 64 GiB of RAM (58,5 GiB usable)
Graphics Processor: AMD Radeon 780M Graphics
Manufacturer: LENOVO
Product Name: 21K5000JGE
System Version: ThinkPad P14s Gen 4

Comment 2 slartibart70 2025-10-06 12:37:06 UTC

it happens after sleeping and turning off/on the screens

laptop-screen is to bright:
brightnessctl -d 'amdgpu_bl1' get
119701

set same 30% again, screen is darkening to the expected 'brightness':
brightnessctl -d 'amdgpu_bl1' set 30%
Updated device 'amdgpu_bl1':
Device 'amdgpu_bl1' of class 'backlight':
        Current brightness: 119700 (30%)
        Max brightness: 399000

No change in output-values...
brightnessctl -d 'amdgpu_bl1' get
119701

Comment 3 TraceyC 2025-10-06 17:10:25 UTC

Can you please run `kscreen-doctor -o | grep -i bright` before putting the system to sleep, and then again afterwards?

This seems potentially related to bug 503268

Comment 4 slartibart70 2025-10-06 21:32:04 UTC

before sleeping (laptop and 4k screen are both at 30%)

kscreen-doctor -o | grep -i bright
        Brightness control: supported, set to 30% and dimming to 100%
        Brightness control: supported, set to 30% and dimming to 100%

after sleeping:
kscreen-doctor -o | grep -i bright
        Brightness control: supported, set to 30% and dimming to 100%
        Brightness control: supported, set to 30% and dimming to 100%

brightnessctl -d amdgpu_bl1 set 30%
Updated device 'amdgpu_bl1':
Device 'amdgpu_bl1' of class 'backlight':
        Current brightness: 119700 (30%)
        Max brightness: 399000

kscreen-doctor -o | grep -i bright
        Brightness control: supported, set to 30% and dimming to 100%
        Brightness control: supported, set to 30% and dimming to 100%


Btw, sleeping is not really necessary:
Lock screen, then press ESC to switch off both screens, wait a bit, re-login is sufficient for the increased brightness on the laptop screen

Comment 5 TraceyC 2025-10-06 21:52:40 UTC

Thanks! I'll let the Plasma developers take it from here