Public bug reported: Backlight brightness control stopped working after upgrading from kernel 7.0.0-27 to 7.0.0-28 on ThinkPad T470 (Intel HD Graphics 620).
The KDE brightness OSD appears and F5/F6 keys respond, but the actual screen brightness does not change. Writing directly to /sys/class/backlight/intel_backlight/brightness has no effect either. Booting back into 7.0.0-27 restores full brightness control. Only one backlight interface exists (intel_backlight, no acpi_video0). This appears to be an i915 regression in 7.0.0-28. A user with a ThinkPad X250 (also Intel HD Graphics) reported the identical issue on the Ubuntu Discourse forum, also resolved by reverting to 7.0.0-27: https://discourse.ubuntu.com/t/screen-brightness-using-kernel-7-0-0-28-on-lenovo-thinkpad-x250-intel-hd-graphics/85267 ProblemType: Bug DistroRelease: Ubuntu 26.04 Package: linux-image-7.0.0-27-generic 7.0.0-27.27 ProcVersionSignature: Ubuntu 7.0.0-27.27-generic 7.0.6 Uname: Linux 7.0.0-27-generic x86_64 AlsaVersion: Advanced Linux Sound Architecture Driver Version k7.0.0-27-generic. AplayDevices: Error: [Errno 2] No such file or directory: 'aplay' ApportVersion: 2.34.1-0ubuntu0.1 Architecture: amd64 ArecordDevices: Error: [Errno 2] No such file or directory: 'arecord' AudioDevicesInUse: USER PID ACCESS COMMAND /dev/snd/controlC0: joel 2850 F.... pipewire joel 2861 F.... wireplumber /dev/snd/pcmC0D0p: joel 2850 F...m pipewire /dev/snd/seq: joel 2850 F.... pipewire CRDA: N/A Card0.Amixer.info: Error: [Errno 2] No such file or directory: 'amixer' Card0.Amixer.values: Error: [Errno 2] No such file or directory: 'amixer' CasperMD5CheckResult: pass CurrentDesktop: KDE Date: Mon Jul 27 11:57:16 2026 InstallationDate: Installed on 2026-07-02 (25 days ago) InstallationMedia: Ubuntu-Server 26.04 "Resolute Raccoon" - Release amd64 (20260420.1) MachineType: LENOVO 20JNS28G00 ProcFB: 0 i915drmfb ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-7.0.0-27-generic root=/dev/mapper/vg0-lv--0 ro 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. RfKill: Error: [Errno 2] No such file or directory: 'rfkill' SourcePackage: linux UpgradeStatus: No upgrade log present (probably fresh install) dmi.bios.date: 11/05/2024 dmi.bios.release: 1.79 dmi.bios.vendor: LENOVO dmi.bios.version: N1QETA4W (1.79 ) dmi.board.asset.tag: Not Available dmi.board.name: 20JNS28G00 dmi.board.vendor: LENOVO dmi.board.version: SDK0J40697 WIN dmi.chassis.asset.tag: PE03BQ37 dmi.chassis.type: 10 dmi.chassis.vendor: LENOVO dmi.chassis.version: None dmi.ec.firmware.release: 1.36 dmi.modalias: dmi:bvnLENOVO:bvrN1QETA4W(1.79):bd11/05/2024:br1.79:efr1.36:svnLENOVO:pn20JNS28G00:pvrThinkPadT470W10DG:rvnLENOVO:rn20JNS28G00:rvrSDK0J40697WIN:cvnLENOVO:ct10:cvrNone:skuLENOVO_MT_20JN_BU_Think_FM_ThinkPadT470W10DG:pfaThinkPadT470W10DG: dmi.product.family: ThinkPad T470 W10DG dmi.product.name: 20JNS28G00 dmi.product.sku: LENOVO_MT_20JN_BU_Think_FM_ThinkPad T470 W10DG dmi.product.version: ThinkPad T470 W10DG dmi.sys.vendor: LENOVO ** Affects: linux (Ubuntu) Importance: Undecided Status: New ** Tags: amd64 apport-bug resolute wayland-session -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/2161904 Title: i915 backlight brightness control broken on ThinkPad T470 after kernel 7.0.0-28 (works on -27) To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2161904/+subscriptions -- ubuntu-bugs mailing list [email protected] https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
