SUMMARY I have Endeavour OS (Arch Linux-based) installed on an old mid-2011 iMac. Every time I boot the computer, it resets the brightness to 95%, even when I had set it to a different level on the previous boot. The widget should enforce the previous brightness level on a new boot, rather than forcing the user to re-adjust the brightness every time. STEPS TO REPRODUCE 1. Set the brightness to your desired level, e.g. 15%. 2. Reboot. OBSERVED RESULT Brightness goes back up to 95%. EXPECTED RESULT Brightness stays at the desired level, e.g. 15%. SOFTWARE/OS VERSIONS Linux/KDE Plasma: Endeavour OS/Arch Linux KDE Plasma Version: 6.3.4 KDE Frameworks Version: 6.13.0 Qt Version: 6.9.0 ADDITIONAL INFORMATION
Does this happen on both X11 and Wayland, or only one session type?
Both session types.
Hi - just to check, if you set the brightness to specifically 100%, is it remembered across boots then? Thinking of what was reported in https://bugs.kde.org/show_bug.cgi?id=501415 , even though that particular case seemed to spontaneously resolve for that user.
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I've just tried this - no it is not remembered when setting it to 100% either. I'm now on Plasma 6.3.5, Frameworks 6.14, Qt 6.9.0.
I'm not able to reproduce this on git-master Just to double-check, can you take a look at System Settings -> Power Management - Display and Brightness Is the "Change screen brightness" checkbox checked?
No, because it's not there.
That definitely seems related. So there are no brightness controls in the KCM?
For what it's worth, I actually don't have a "Change screen brightness" checkbox in Power Management either (on Fedora 42 Plasma 6.3.5, or on git master) - just dropdowns for Dim automatically and Turn off screen.
Same here for me as well, there are only dropdowns to dim and turn off the screen after a given amount of time. I have checked on my laptop and the brightness controls are present there.
Do both of you have only desktop monitors plugged in?
At least for me, I only have one monitor attached to my desktop (ASUSTek COMPUTER INC VG27AQL1A). Just double-checking, we're talking about System Settings > Power Management, then the "Display and Brightness" section within that page, right? On System Settings > Display & Monitor > Display Configuration, I do have the checkbox for "Control hardware brightness with DDC/CI".
I experience this issue on an iMac that has an integrated screen and it's the only one; as far as I know it is treated like a laptop monitor.
Can affected people run `kscreen-doctor -o | grep -i bright` before rebooting, and then again afterwards?
Updating the status of this report, pending the reporter being able to provide that info (I'm not affected by the reported issue). Thanks!
(In reply to Nate Graham from comment #14) > Can affected people run `kscreen-doctor -o | grep -i bright` before > rebooting, and then again afterwards? Funnily enough, it says that brightness control is not supported!
Update: after a reboot, it actually does say that it is supported: Brightness control: supported, set to 15% and dimming to 100% What is happening with Plasma 6.4 is now slightly different to what it was when I opened the bug report: it now says that brightness is at 15% even though it is not, and when I change the brightness it adjusts it to the actual selected value - I can tell because the brightness is reduced dramatically when this happens.
(In reply to Nate Graham from comment #14) > Can affected people run `kscreen-doctor -o | grep -i bright` before > rebooting, and then again afterwards? Hello, The output is the same before and after reboot: > Brightness control: supported, set to 30% and dimming to 100% SOFTWARE/OS VERSIONS Operating System: Arch Linux KDE Plasma Version: 6.4.5 KDE Frameworks Version: 6.18.0 Qt Version: 6.9.2 Kernel Version: 6.16.10-arch1-1 (64-bit) Graphics Platform: Wayland Processors: 24 × AMD Ryzen AI 9 HX 370 w/ Radeon 890M Memory: 32 Gio of RAM (30.5 Gio usable) Graphics Processor: AMD Radeon 890M Graphics Manufacturer: ASUSTeK COMPUTER INC. Product Name: ASUS Zenbook S 16 UM5606WA_UM5606WA System Version: 1.0
I went to check if my other device was affected, but surprisingly it isn't. It's a laptop connected to two external displays, and the brightness for all displays is correctly set after reboot, whether the laptop is running on AC power or battery It also seems that I do not have a "Change screen brightness" checkbox in the Power Management KCM on this machine How can I help diagnose this issue ? SOFTWARE/OS VERSIONS Operating System: Kubuntu 25.04 KDE Plasma Version: 6.3.4 KDE Frameworks Version: 6.12.0 Qt Version: 6.8.3 Kernel Version: 6.14.0-29-generic (64-bit) Graphics Platform: Wayland Processors: 12 × AMD Ryzen 5 5600H with Radeon Graphics Memory: 27.3 Gio of RAM Graphics Processor 1: AMD Radeon Graphics Graphics Processor 2: NVIDIA GeForce RTX 3060 Laptop GPU Manufacturer: LENOVO Product Name: 82JU System Version: Legion 5 15ACH6H
*** Bug 508434 has been marked as a duplicate of this bug. ***
I have the same issue on an Intel laptop (Lunar Lake): Operating System: NixOS 25.11 KDE Plasma Version: 6.4.5 KDE Frameworks Version: 6.18.0 Qt Version: 6.9.2 Kernel Version: 6.16.7-zen1 (64-bit) Graphics Platform: Wayland Processors: 8 × Intel® Core™ Ultra 7 258V Memory: 32 GiB of RAM (30.9 GiB usable) Graphics Processor: Intel® Graphics Manufacturer: LENOVO Product Name: 83LC System Version: Yoga 9 2-in-1 14ILL10 Same as others, `brightnessctl` and `kscreen-doctor` both report the same value before and after sleep. I do have the "Change screen brightness" checkbox in Power Management. I had the same issue on Fedora 42, with both KDE Plasma and Cosmic desktops, but not on GNOME.
I'm marking this confirmed, since multiple people are able to reproduce it
My issue seems more similar to https://bugs.kde.org/show_bug.cgi?id=508434, but since it's been marked as duplicate of this bug, I'll post here: For me, brightness does seem to persist across reboots (I usually use suspend-to-disk though, not sure how it behaves across full reboots), but it resets when the laptop screen turns on again after being turned off due to inactivity. The external screen is unaffected. kscreen-doctor output doesn't change, in both states it reports $ kscreen-doctor -o | grep -i bright Brightness control: supported, set to 20% and dimming to 100% Brightness control: supported, set to 50% and dimming to 100% (20% is the laptop screen) I have the impression that this only started happening recently, perhaps with the upgrade to ddcutil 2.2.1?
ddcutil isn't involved for internal displays. The only thing I can think of happening there is a kernel bug, that it's doing something odd to the backlight when turning on the display. Could you try some older kernels and see if it still happens there?
It has been happening for at least six months in my case, so if it is a kernel bug, it is a long-standing one. It does not seem related to either X11 nor Wayland, as it happens on both, nor to the GPU manufacturer (it seems to happen for Intel, AMD and NVIDIA, judging by what people have reported).
@Zamundaaa You were right, it's the kernel. The issue first appears in 6.16.10 and is still present in 6.17.2. Kernel 6.16.9 works fine. I also realized that there are two other ways to trigger the brightness reset: - reboot, the screen will be much brighter than it should be - switch to a virtual terminal. Also here, the screen becomes much brighter and it does not dim when switching back to the graphical session I don't know if it helps, but this is on a Thinkpad T14 Gen5 with AMD Ryzen 7 PRO 8840U w/ Radeon 780M Graphics
I looked at the changelog for kernel 6.16.10, and this looks relevant (I don't have HDR enabled btw): commit 3bf00f58a8075fe881890cb21b753105f231713d Author: Matthew Schwartz <matthew.schwartz@linux.dev> Date: Thu Sep 11 10:48:51 2025 -0700 drm/amd/display: Only restore backlight after amdgpu_dm_init or dm_resume commit 44b0fed0a5947f54fd14255cd0766df952267bc5 upstream. On clients that utilize AMD_PRIVATE_COLOR properties for HDR support, brightness sliders can include a hardware controlled portion and a gamma-based portion. This is the case on the Steam Deck OLED when using gamescope with Steam as a client. When a user sets a brightness level while HDR is active, the gamma-based portion and/or hardware portion are adjusted to achieve the desired brightness. However, when a modeset takes place while the gamma-based portion is in-use, restoring the hardware brightness level overrides the user's overall brightness level and results in a mismatch between what the slider reports and the display's current brightness. To avoid overriding gamma-based brightness, only restore HW backlight level after boot or resume. This ensures that the backlight level is set correctly after the DC layer resets it while avoiding interference with subsequent modesets. Fixes: 7875afafba84 ("drm/amd/display: Fix brightness level not retained over reboot") Closes: https://gitlab.freedesktop.org/drm/amd/-/issues/4551 Signed-off-by: Matthew Schwartz <matthew.schwartz@linux.dev> Reviewed-by: Mario Limonciello <mario.limonciello@amd.com> Signed-off-by: Mario Limonciello <mario.limonciello@amd.com> Signed-off-by: Alex Deucher <alexander.deucher@amd.com> (cherry picked from commit a490c8d77d500b5981e739be3d59c60cfe382536) Cc: stable@vger.kernel.org Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
*** Bug 510743 has been marked as a duplicate of this bug. ***
Hello again. I'm no longer affected by this bug. Upgrading my kernel seems to have fixed it at some point. Is anyone else on the latest kernel still affected ? Operating System: Arch Linux KDE Plasma Version: 6.5.0 KDE Frameworks Version: 6.19.0 Qt Version: 6.10.0 Kernel Version: 6.17.5-arch1-1 (64-bit) Graphics Platform: Wayland Processors: 24 × AMD Ryzen AI 9 HX 370 w/ Radeon 890M Memory: 32 Gio of RAM (30.5 Gio usable) Graphics Processor: AMD Radeon 890M Graphics Manufacturer: ASUSTeK COMPUTER INC. Product Name: ASUS Zenbook S 16 UM5606WA_UM5606WA System Version: 1.0
It still happens on my iMac with the latest kernel installed (6.17.6).