Public bug reported: This is a kernel regression affecting the internal display backlight on a Dell XPS 13 Plus 9320.
Hardware: Dell XPS 13 Plus 9320 Intel Alder Lake-P GT2 [Iris Xe Graphics] Kernel driver: i915 Working kernel: 6.8.0-137-generic Broken kernel: 7.0.0-28-generic With 7.0.0-28-generic, the GNOME brightness slider and keyboard brightness controls behave normally and the on-screen brightness indicator changes, but the physical brightness of the internal display does not change. The kernel backlight interface also appears to accept the changes. For example: /sys/class/backlight/intel_backlight/brightness and /sys/class/backlight/intel_backlight/actual_brightness both change when adjusting the brightness. I tested values including approximately 50 and 700, and both sysfs values change accordingly, while the actual screen luminance remains visually identical. There is only one backlight interface present: intel_backlight Booting the same machine with 6.8.0-137-generic immediately restores normal brightness control, without changing any other configuration. Steps to reproduce Boot the Dell XPS 13 Plus 9320 with 7.0.0-28-generic. Adjust brightness using the keyboard brightness keys or GNOME slider. Observe that the OSD/slider changes. Observe that brightness and actual_brightness under /sys/class/backlight/intel_backlight/ also change. Physical display brightness remains unchanged. Reboot using 6.8.0-137-generic. Brightness control works normally. Expected result: Internal-panel brightness follows the requested backlight value. Actual result: The requested and reported backlight values change, but panel luminance remains fixed. This therefore appears to be a regression in the Intel i915 backlight/display handling between the working Ubuntu kernel 6.8.0-137-generic and 7.0.0-28-generic. 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: 2.28.2-0ubuntu0.1 Architecture: amd64 CRDA: N/A CasperMD5CheckMismatches: ./casper/initrd ./casper/vmlinuz ./scripts/chroot-scripts/os-post/70_fix-apt-installed.sh CasperMD5CheckResult: fail CurrentDesktop: KDE Date: Mon Aug 17 12:47:33 2026 DistributionChannelDescriptor: # This is the distribution channel descriptor for the OEM CDs # For more information see http://wiki.ubuntu.com/DistributionChannelDescriptor canonical-oem-somerville-jammy-amd64-20220504-33 InstallationDate: Installed on 2022-11-19 (1367 days ago) InstallationMedia: Ubuntu 22.04 LTS "Jammy Jellyfish" - somerville-jammy-amd64-20220504-33 MachineType: Dell Inc. XPS 9320 ProcFB: 0 i915drmfb ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-7.0.0-28-generic root=UUID=aa87ea66-9773-4eb7-82cb-af6b3eae464a 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.git3b128b60-0ubuntu2.27 SourcePackage: linux-hwe-7.0 UpgradeStatus: Upgraded to noble on 2024-10-14 (672 days ago) dmi.bios.date: 04/23/2026 dmi.bios.release: 2.30 dmi.bios.vendor: Dell Inc. dmi.bios.version: 2.30.0 dmi.board.name: 0CW9KM dmi.board.vendor: Dell Inc. dmi.board.version: A00 dmi.chassis.type: 10 dmi.chassis.vendor: Dell Inc. dmi.ec.firmware.release: 1.19 dmi.modalias: dmi:bvnDellInc.:bvr2.30.0:bd04/23/2026:br2.30:efr1.19:svnDellInc.:pnXPS9320:pvr:rvnDellInc.:rn0CW9KM:rvrA00:cvnDellInc.:ct10:cvr:sku0AF3:pfaXPS: dmi.product.family: XPS dmi.product.name: XPS 9320 dmi.product.sku: 0AF3 dmi.sys.vendor: Dell Inc. ** Affects: linux-hwe-7.0 (Ubuntu) Importance: Undecided Status: New ** Tags: amd64 apport-bug noble -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/2163645 Title: Dell XPS 13 Plus 9320: internal display brightness broken in 7.0.0-28-generic, works in 6.8.0-137-generic (i915 regression) To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux-hwe-7.0/+bug/2163645/+subscriptions -- ubuntu-bugs mailing list [email protected] https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
