[Bug 2163611] Re: ThinkPad L480 internal display backlight control does not work with >=7.0.0-28 kernel, works with 7.0.0-27

*** This bug is a duplicate of bug 2161309 *** https://bugs.launchpad.net/bugs/2161309 ** This bug has been marked a duplicate of bug 2161309 Backlight regression -- You received this bug notification because you are subscribed to linux in Ubuntu. Matching subscriptions: Bgg, Bmail, Nb https://bugs.launchpad.net/bugs/2163611 Title: ThinkPad L480 internal display backlight control does not work with >=7.0.0-28 kernel, works with 7.0.0-27 Status in linux package in Ubuntu: New Bug description: Changing internal display brightness with keyboard buttons or software slider does not work with kernel 7.0.0-28 and later. GUI responds correctly and shows OSD slider but with no effect on actual brightness. Reverting to 7.0.0-27 completely resolves the issue. Operating System: Kubuntu 26.04 LTS KDE Plasma Version: 6.6.6 KDE Frameworks Version: 6.24.0 Qt Version: 6.10.2 Kernel Version: 7.0.0-29-generic (64-bit) Graphics Platform: Wayland Processors: 8 × Intel® Core™ i5-8250U CPU @ 1.60GHz Memory: 16 GiB of RAM (15,4 GiB usable) Graphics Processor: Intel® UHD Graphics 620 Manufacturer: LENOVO Product Name: 20LS001APB System Version: ThinkPad L480 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: adrian 1683 F.... wireplumber /dev/snd/seq: adrian 1679 F.... pipewire CasperMD5CheckResult: unknown CurrentDesktop: KDE Date: Sun Aug 16 20:50:25 2026 InstallationDate: Installed on 2026-07-12 (35 days ago) InstallationMedia: Kubuntu 26.04 "Resolute Raccoon" - Release amd64 (20260423) Lsusb: Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub Bus 001 Device 002: ID 1038:184d SteelSeries ApS SteelSeries Prime Mini Bus 001 Device 004: ID 5986:2113 Bison Electronics Inc. SunplusIT Integrated Camera Bus 001 Device 005: ID 06cb:009a Synaptics, Inc. Metallica MIS Touch Fingerprint Reader Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub MachineType: LENOVO 20LS001APB ProcFB: 0 i915drmfb ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-7.0.0-29-generic root=UUID=3bf2d49d-799f-4ae6-b0de-64e14314f483 ro quiet cryptdevice=UUID=8cd4aa2b-6444-46ce-8ebb-1a320b5b0ad1:luks-8cd4aa2b-6444-46ce-8ebb-1a320b5b0ad1 root=/dev/mapper/luks-8cd4aa2b-6444-46ce-8ebb-1a320b5b0ad1 splash PulseList: Error: command ['pacmd', 'list'] failed with exit code 1: No PulseAudio daemon running, or not running as session daemon. SourcePackage: linux UpgradeStatus: No upgrade log present (probably fresh install) dmi.bios.date: 01/03/2023 dmi.bios.release: 1.46 dmi.bios.vendor: LENOVO dmi.bios.version: R0QET69W (1.46 ) dmi.board.asset.tag: Not Available dmi.board.name: 20LS001APB 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: 1.46 dmi.modalias: dmi:bvnLENOVO:bvrR0QET69W(1.46):bd01/03/2023:br1.46:efr1.46:svnLENOVO:pn20LS001APB:pvrThinkPadL480:rvnLENOVO:rn20LS001APB:rvrSDK0J40697WIN:cvnLENOVO:ct10:cvrNone:skuLENOVO_MT_20LS_BU_Think_FM_ThinkPadL480:pfaThinkPadL480: dmi.product.family: ThinkPad L480 dmi.product.name: 20LS001APB dmi.product.sku: LENOVO_MT_20LS_BU_Think_FM_ThinkPad L480 dmi.product.version: ThinkPad L480 dmi.sys.vendor: LENOVO To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2163611/+subscriptions