Public bug reported:
Problem
With kernel 7.0.0-28-generic, the display backlight does not work
correctly on my Fujitsu LIFEBOOK E548 with Intel UHD Graphics 620.
The brightness keys display the KDE brightness indicator, but the actual
display brightness does not change.
When the display is automatically switched off due to inactivity, the
display wakes up but the image is only barely visible because the
backlight does not come back on. The system itself continues to run and
responds to input.
Important regression test
The exact same Kubuntu installation works correctly when booted with
kernel 6.17.0-40-generic:
brightness keys work normally
actual display brightness changes correctly
the display backlight comes back normally after automatic screen-off
Therefore this appears to be a kernel regression in 7.0.0-28-generic.
Hardware
Fujitsu LIFEBOOK E548
Intel UHD Graphics 620 (Kaby Lake), PCI ID 8086:5917
Kernel driver: i915
Internal display: LG Display 0x05b6, 1920x1080, eDP-1
Desktop: KDE Plasma / KWin X11
Additional test
The kernel backlight interface /sys/class/backlight/intel_backlight is
present and accepts brightness values. However, changing the value has
no physical effect on the display brightness under kernel 7.0.0-28.
For example:
echo 500 | sudo tee /sys/class/backlight/intel_backlight/brightness
changes the reported value from 1023 to 500, but the actual display
brightness does not change.
Booting kernel 6.17.0-40-generic immediately restores normal brightness
control and normal display wake-up behavior.
The problem is therefore reproducible and appears to be specific to
kernel 7.0.0-28.
ProblemType: Bug
DistroRelease: Ubuntu 24.04
Package: linux-image-7.0.0-28-generic 7.0.0-28.28~24.04.1
ProcVersionSignature: Ubuntu 7.0.0-28.28~24.04.1-generic 7.0.12
Uname: Linux 7.0.0-28-generic x86_64
ApportVersion: 2.28.3-0ubuntu0.1
Architecture: amd64
AudioDevicesInUse:
USER PID ACCESS COMMAND
/dev/snd/controlC0: frankb 1574 F.... wireplumber
/dev/snd/seq: frankb 1571 F.... pipewire
CRDA: N/A
CasperMD5CheckResult: unknown
CurrentDesktop: KDE
Date: Sat Aug 15 15:00:15 2026
InstallationDate: Installed on 2026-05-27 (80 days ago)
InstallationMedia: Kubuntu 24.04.4 LTS "Noble Numbat" - Release amd64 (20260210)
Lsusb:
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 001 Device 002: ID 8087:0a2b Intel Corp. Bluetooth wireless interface
Bus 001 Device 003: ID 04f2:b562 Chicony Electronics Co., Ltd FJ Camera
Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
MachineType: FUJITSU LIFEBOOK E548
ProcFB: 0 i915drmfb
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-7.0.0-28-generic
root=UUID=64b5a95e-10b0-46ad-a2e8-a0b60f4eedee ro quiet splash vt.handoff=7
PulseList: Error: command ['pacmd', 'list'] failed with exit code 1: No
PulseAudio daemon running, or not running as session daemon.
RelatedPackageVersions:
linux-restricted-modules-7.0.0-28-generic N/A
linux-backports-modules-7.0.0-28-generic N/A
linux-firmware 20240318.git3b128b60-0ubuntu2.29
SourcePackage: linux-hwe-7.0
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 05/15/2019
dmi.bios.release: 1.16
dmi.bios.vendor: FUJITSU // Insyde Software Corp.
dmi.bios.version: Version 1.16
dmi.board.name: FJNB2B7
dmi.board.vendor: FUJITSU
dmi.board.version: A1
dmi.chassis.type: 10
dmi.chassis.vendor: FUJITSU
dmi.chassis.version: LIFEBOOK E548
dmi.modalias:
dmi:bvnFUJITSU//InsydeSoftwareCorp.:bvrVersion1.16:bd05/15/2019:br1.16:svnFUJITSU:pnLIFEBOOKE548:pvr10601736746:rvnFUJITSU:rnFJNB2B7:rvrA1:cvnFUJITSU:ct10:cvrLIFEBOOKE548:sku:pfaLIFEBOOK-FTS:
dmi.product.family: LIFEBOOK-FTS
dmi.product.name: LIFEBOOK E548
dmi.product.version: 10601736746
dmi.sys.vendor: FUJITSU
** Affects: linux-hwe-7.0 (Ubuntu)
Importance: Undecided
Status: New
** Tags: amd64 apport-bug noble
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https://bugs.launchpad.net/bugs/2163569
Title:
[regression] Intel UHD 620 backlight broken with kernel 7.0.0-28 on
Fujitsu LIFEBOOK E548
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