Kernel 6.5 breaks display brightness controls and sets it to 100% all the time
Affects | Status | Importance | Assigned to | Milestone | |
---|---|---|---|---|---|
linux-signed-hwe-6.5 (Ubuntu) |
Confirmed
|
Undecided
|
Unassigned |
Bug Description
Since kernel 6.5, monitor brightness is set to 100%, and cannot be changed: The brightness controls have disappeared from Settings, and brightness doesn't respond to the keypad controls.
See the attached screenshot, showing the difference between the settings in kernels 6.2 and 6.5.
This applies to Ubuntu 22.04 and 23.10, whether using Wayland or X.Org.
It's possible (when using X.Org) to adjust the brightness with…
$ xrandr --output [monitor] --brightness [brightness]
e.g. on my machine…
$ xrandr --output eDP-1 --brightness 0.5
… but, unfortunately, it doesn't last long — anywhere between a less than a second later and about a minute later, the screen reverts to 100% brightness.
As a workaround, I am running the following command in the background…
$ while true; do xrandr --output eDP-1 --brightness 0.5; sleep 1s; done
… which results in the screen at the correct brightness, but frequently flashing!
———————
UPDATES
———————
• See comment #7 — This is somehow linked to the Night Light.
• Even when Night Light is permanently turned off, the screen still (sometimes; it's intermittent) goes bright when…
— Playing a video full screen (e.g. VLC, YouTube).
— Chrome gives a pop-up dialogue (e.g. downloading) or a notification (e.g. Calendar notification).
—————————
TESTED ON
—————————
• Ubuntu 22.04
— Kernel 6.2.0-39 and prior works correctly
— Kernels 6.5.0-14 & 6.5.0.15 have the problem
• Ubuntu 23.10
— Kernel 6.5.0-9 has the problem
$ sudo lshw -numeric -C display
*-display
description: VGA compatible controller
product: CometLake-S GT2 [UHD Graphics 630] [8086:9BC5]
vendor: Intel Corporation [8086]
physical id: 2
bus info: pci@0000:00:02.0
logical name: /dev/fb0
version: 05
width: 64 bits
clock: 33MHz
resources: irq:145 memory:
ProblemType: Bug
DistroRelease: Ubuntu 22.04
Package: linux-image-
ProcVersionSign
Uname: Linux 6.5.0-14-generic x86_64
ApportVersion: 2.20.11-0ubuntu82.5
Architecture: amd64
CasperMD5CheckR
CurrentDesktop: ubuntu:GNOME
Date: Sat Jan 13 07:19:58 2024
InstallationDate: Installed on 2022-08-28 (502 days ago)
InstallationMedia: Ubuntu 22.04.1 LTS "Jammy Jellyfish" - Release amd64 (20220809.1)
SourcePackage: linux-signed-
UpgradeStatus: No upgrade log present (probably fresh install)
description: | updated |
I have been pointed to bug #2032174. It says that it has been fixed and ported to Jammy (22.04), but it seems that this is incorrect.
It is probably relevant to indicate my hardware, which is Dell OptiPlex 5480 All-In-One. hwe-6.5, so maybe it wasn't ported to the HWE version?
And my kernel is linux-signed-