Public bug reported:
Display brightness is non-configurable in kernel package 7.0.0-28 on my
i915 / eDP display (Thinkpad T440s).
I tested the following kernels from 26.04, all worked prior to 7.0.0-28:
7.0.0-14
7.0.0-15
7.0.0-22
7.0.0-27
Additional info:
$ ls -l /sys/class/backlight/
total 0
lrwxrwxrwx 1 root root 0 Jul 28 17:04 intel_backlight ->
../../devices/pci0000:00/0000:00:02.0/drm/card1/card1-eDP-1/intel_backlight
I tried kernel options acpi_backlight=(native|vendor|video), and
i915.enable_dpcd_backlight=(1|3) -- no improvement.
In 7.0.0-28, even manually writing to, e.g.,
/sys/devices/pci0000:00/0000:00:02.0/backlight/acpi_video0/brightness ,
does not affect the brightness.
ProblemType: Bug
DistroRelease: Ubuntu 26.04
Package: linux-image-7.0.0-28-generic 7.0.0-28.28
ProcVersionSignature: Ubuntu 7.0.0-28.28-generic 7.0.12
Uname: Linux 7.0.0-28-generic x86_64
ApportVersion: 2.34.0-0ubuntu2
Architecture: amd64
AudioDevicesInUse:
USER PID ACCESS COMMAND
/dev/snd/controlC1: david 3833 F.... wireplumber
/dev/snd/controlC0: david 3833 F.... wireplumber
/dev/snd/seq: david 3821 F.... pipewire
CasperMD5CheckResult: unknown
CurrentDesktop: ubuntu:GNOME
Date: Tue Jul 28 17:05:13 2026
EcryptfsInUse: Yes
InstallationDate: Installed on 2014-04-25 (4477 days ago)
InstallationMedia: Ubuntu 14.04 LTS "Trusty Tahr" - Release amd64 (20140417)
MachineType: LENOVO 20AQCTO1WW
ProcEnviron:
LANG=en_US.utf8
PATH=(custom, no user)
SHELL=/bin/bash
TERM=xterm-256color
XDG_RUNTIME_DIR=<set>
ProcFB: 0 i915drmfb
ProcKernelCmdLine: BOOT_IMAGE=/@/boot/vmlinuz-7.0.0-28-generic
root=UUID=a2a884f3-8c85-4dd4-8668-4cebfde36f37 ro rootflags=subvol=@ nosplash
i915.enable_dpcd_backlight=3
crashkernel=2G-4G:320M,4G-32G:512M,32G-64G:1024M,64G-128G:2048M,128G-:4096M
PulseList: Error: command ['pacmd', 'list'] failed with exit code 1: No
PulseAudio daemon running, or not running as session daemon.
SourcePackage: linux
UpgradeStatus: Upgraded to resolute on 2026-04-23 (96 days ago)
dmi.bios.date: 03/27/2020
dmi.bios.release: 2.54
dmi.bios.vendor: LENOVO
dmi.bios.version: GJETA4WW (2.54 )
dmi.board.asset.tag: Not Available
dmi.board.name: 20AQCTO1WW
dmi.board.vendor: LENOVO
dmi.board.version: SDK0E50510 PRO
dmi.chassis.asset.tag: No Asset Information
dmi.chassis.type: 10
dmi.chassis.vendor: LENOVO
dmi.chassis.version: Not Available
dmi.ec.firmware.release: 1.14
dmi.modalias:
dmi:bvnLENOVO:bvrGJETA4WW(2.54):bd03/27/2020:br2.54:efr1.14:svnLENOVO:pn20AQCTO1WW:pvrThinkPadT440s:rvnLENOVO:rn20AQCTO1WW:rvrSDK0E50510PRO:cvnLENOVO:ct10:cvrNotAvailable:skuLENOVO_MT_20AQ_BU_Think_FM_ThinkPadT440s:pfaThinkPadT440s:
dmi.product.family: ThinkPad T440s
dmi.product.name: 20AQCTO1WW
dmi.product.sku: LENOVO_MT_20AQ_BU_Think_FM_ThinkPad T440s
dmi.product.version: ThinkPad T440s
dmi.sys.vendor: LENOVO
** Affects: linux (Ubuntu)
Importance: Undecided
Status: New
** Tags: amd64 apport-bug resolute wayland-session
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https://bugs.launchpad.net/bugs/2162017
Title:
i915 / eDP brightness regression in 7.0.0-28 (vs 7.0.0-27)
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