Public bug reported:
After booting Ubuntu 24.04 with kernel 7.0.0-28-generic, the internal
eDP panel stays at approximately minimum physical backlight brightness.
GNOME's brightness OSD and slider move normally, but the panel
brightness does not change.
The kernel backlight interface also reports successful changes:
/sys/class/backlight/intel_backlight/brightness and actual_brightness
both move through the full 0..1023 range. Directly writing values 1 and
1023 does not change physical brightness. Cycling bl_power and
disabling/re-enabling eDP-1 with xrandr also have no effect.
Booting the same installation and hardware with 6.17.0-40-generic
immediately restores normal brightness control. Hotkeys, GNOME slider,
and the physical panel brightness all work correctly. No userspace,
BIOS, or hardware changes were made between these boots.
Steps to reproduce:
1. Boot 7.0.0-28-generic on this HP Pavilion x360.
2. Use the brightness hotkeys or GNOME brightness slider.
3. Observe that the OSD and sysfs values change, but physical panel brightness
remains dim.
4. Boot 6.17.0-40-generic and observe that physical brightness control works
normally.
Expected result: Physical panel brightness follows the GNOME slider and
intel_backlight values.
Actual result: On 7.0.0-28 the physical backlight ignores all brightness values
while software reports success.
ProblemType: Bug
DistroRelease: Ubuntu 24.04
Package: linux-image-7.0.0-28-generic 7.0.0-28.28~24.04.1
Regression: Yes; 6.17.0-40 works, 7.0.0-28 fails on identical hardware and
userspace.
ProcVersionSignature: Ubuntu 6.17.0-40.40~24.04.1-generic 6.17.13
Uname: Linux 6.17.0-40-generic x86_64
ApportVersion: 2.28.1-0ubuntu3.8
Architecture: amd64
BrokenKernel: 7.0.0-28-generic (7.0.0-28.28~24.04.1)
CasperMD5CheckResult: pass
CurrentDesktop: GNOME
Date: Fri Aug 7 13:54:40 2026
GraphicsDevice: Intel HD Graphics 610 [8086:5906], subsystem HP [103c:830f],
i915
InstallationDate: Installed on 2024-07-02 (766 days ago)
InstallationMedia: Ubuntu 24.04 LTS "Noble Numbat" - Release amd64 (20240424)
MachineType: HP Pavilion x360 Convertible 14-ba0xx, BIOS F.60
SourcePackage: linux-hwe-7.0
Title: [i915] Backlight PWM changes ignored on HP Pavilion x360 14-ba0xx with
7.0.0-28; 6.17.0-40 works
UpgradeStatus: No upgrade log present (probably fresh install)
WorkingKernel: 6.17.0-40-generic (6.17.0-40.40~24.04.1)
** Affects: linux-hwe-7.0 (Ubuntu)
Importance: Undecided
Status: New
** Tags: amd64 apport-bug i915 noble regression-update
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https://bugs.launchpad.net/bugs/2163014
Title:
[i915] Backlight PWM changes ignored on HP Pavilion x360 14-ba0xx with
7.0.0-28; 6.17.0-40 works
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