Public bug reported:
Since the update two weeks ago, i was not able to dimm the brightness of my
T480 screen any more. In addition, the backlight was not working any more after
suspend.
I was able to fix that bug for me, by adding i915.enable_dpcd_backlight=0 to
grub.
Hope this helps to make it run again on other systems :)
Description: Ubuntu 26.04 LTS
Release: 26.04
Using KDE from the Kubuntu Repo
ProblemType: Bug
DistroRelease: Ubuntu 26.04
Package: linux-image-7.0.0-29-generic 7.0.0-29.29
ProcVersionSignature: Ubuntu 7.0.0-29.29-generic 7.0.12
Uname: Linux 7.0.0-29-generic x86_64
ApportVersion: 2.34.1-0ubuntu0.1
Architecture: amd64
AudioDevicesInUse:
USER PID ACCESS COMMAND
/dev/snd/controlC0: leon 3208 F.... wireplumber
/dev/snd/seq: leon 3193 F.... pipewire
CasperMD5CheckResult: unknown
CurrentDesktop: KDE
Date: Tue Aug 11 21:11:07 2026
InstallationDate: Installed on 2025-02-24 (533 days ago)
InstallationMedia: Kubuntu 24.10 "Oracular Oriole" - Release amd64 (20241007.6)
MachineType: LENOVO 20L6S69B00
ProcFB: 0 i915drmfb
ProcKernelCmdLine: BOOT_IMAGE=/@/boot/vmlinuz-7.0.0-29-generic
root=UUID=479d0569-3f49-4684-81d5-e523668c3705 ro rootflags=subvol=@ quiet
splash i915.enable_dpcd_backlight=0
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 2026-04-27 (106 days ago)
dmi.bios.date: 09/06/2025
dmi.bios.release: 1.56
dmi.bios.vendor: LENOVO
dmi.bios.version: N24ET81W (1.56 )
dmi.board.asset.tag: Not Available
dmi.board.name: 20L6S69B00
dmi.board.vendor: LENOVO
dmi.board.version: SDK0J40697 WIN
dmi.chassis.asset.tag: No Asset Information
dmi.chassis.type: 10
dmi.chassis.vendor: LENOVO
dmi.chassis.version: None
dmi.ec.firmware.release: 1.22
dmi.modalias:
dmi:bvnLENOVO:bvrN24ET81W(1.56):bd09/06/2025:br1.56:efr1.22:svnLENOVO:pn20L6S69B00:pvrThinkPadT480:rvnLENOVO:rn20L6S69B00:rvrSDK0J40697WIN:cvnLENOVO:ct10:cvrNone:skuLENOVO_MT_20L6_BU_Think_FM_ThinkPadT480:pfaThinkPadT480:
dmi.product.family: ThinkPad T480
dmi.product.name: 20L6S69B00
dmi.product.sku: LENOVO_MT_20L6_BU_Think_FM_ThinkPad T480
dmi.product.version: ThinkPad T480
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/2163269
Title:
Blackscreen and no brightness dimming after update
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