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, mkyral
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

Comment 6 Marian Kyral 2025-12-11 14:11:44 UTC

I have the same issue on two different laptops with external monitor. On system start is the laptop screen very bright. But brightness applet shows that laptop screen is set to 25 %. I need to touch the slider to fix it.

I'm sure this is some regression as it worked correctly in past.

Operating System: Gentoo Linux 2.18
KDE Plasma Version: 6.5.4
KDE Frameworks Version: 6.20.0
Qt Version: 6.9.3
Kernel Version: 6.18.0-gentoo (64-bit)
Graphics Platform: Wayland
Processors: 12 × 12th Gen Intel® Core™ i7-1265U
Memory: 32 GiB of RAM (31.0 GiB usable)
Graphics Processor: Intel® Iris® Xe Graphics
Manufacturer: Dell Inc.
Product Name: Latitude 5530