Probably a duplicate of bug 2161309 Please try kernel 7.0.0-31, which should be available on your repo mirror soon if it is not already. ** Changed in: linux (Ubuntu) Status: New => Incomplete -- You received this bug notification because you are subscribed to linux in Ubuntu. Matching subscriptions: Bgg, Bmail, Nb https://bugs.launchpad.net/bugs/2166520 Title: Dell XPS 13 9340: intel_backlight values change but Sharp C71M1 panel brightness does not Status in linux package in Ubuntu: Incomplete Bug description: Hardware: * Dell XPS 13 9340 * BIOS/firmware version: 1.24.0 * GPU: Intel Meteor Lake-P [Intel Arc Graphics], PCI ID 8086:7d55 * Kernel driver: i915 * Internal display: Sharp SHP 5519, Dell C71M1, 2560×1600 QHD+ LED-backlit LCD * 64 GiB RAM Software: * Ubuntu 26.04.1 LTS, 64-bit * GNOME 50 * Wayland * Kernel 7.0.0-30-generic Expected behaviour: Changing brightness with the keyboard brightness keys or GNOME brightness slider should change the physical brightness of the internal display. Actual behaviour: The brightness OSD appears and its slider changes, but the physical brightness of the display remains completely unchanged. Additional tests: 1. /sys/class/backlight/intel_backlight exists. 2. The interface reports max_brightness=1023 and type=raw. 3. Writing a value directly to /sys/class/backlight/intel_backlight/brightness changes both brightness and actual_brightness, but the physical display brightness remains unchanged. 4. For example, after writing 300, both brightness and actual_brightness reported 300, while the display remained visually identical. 5. Brightness adjustment works correctly inside the Dell BIOS, so the panel and backlight hardware are functional. 6. The issue also occurs with kernel 7.0.0-29-generic. 7. The following i915 DPCD backlight modes were tested without success: * i915.enable_dpcd_backlight=1 * i915.enable_dpcd_backlight=2 * i915.enable_dpcd_backlight=3 8. The original boot configuration has been restored to i915.enable_dpcd_backlight=1. The issue therefore appears to be in the i915 backlight control for this specific Sharp/Dell panel: the sysfs values change, but the corresponding hardware brightness command is not applied. ProblemType: Bug DistroRelease: Ubuntu 26.04 Package: linux-image-7.0.0-30-generic 7.0.0-30.30 ProcVersionSignature: Ubuntu 7.0.0-30.30-generic 7.0.12 Uname: Linux 7.0.0-30-generic x86_64 ApportVersion: 2.34.1-0ubuntu0.1 Architecture: amd64 AudioDevicesInUse: USER PID ACCESS COMMAND /dev/snd/controlC0: armando 6199 F.... pipewire armando 6209 F.... wireplumber /dev/snd/seq: armando 6199 F.... pipewire CasperMD5CheckResult: pass CurrentDesktop: ubuntu:GNOME Date: Fri Sep 4 18:43:49 2026 InstallationDate: Installed on 2026-06-05 (91 days ago) InstallationMedia: Ubuntu 26.04 "Resolute Raccoon" - Release amd64 (20260423.1) MachineType: Dell Inc. XPS 13 9340 ProcEnviron: LANG=en_US.UTF-8 PATH=(custom, no user) SHELL=/bin/bash TERM=xterm-256color XDG_RUNTIME_DIR=<set> ProcFB: 0 i915drmfb ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-7.0.0-30-generic root=/dev/mapper/ubuntu--vg-ubuntu--lv ro quiet splash xe.force_probe=7d14 i915.force_probe=!7d14 xe.fastboot=1 i915.enable_dpcd_backlight=1 crashkernel=2G-4G:320M,4G-32G:512M,32G-64G:1024M,64G-128G:2048M,128G-:4096M SourcePackage: linux UpgradeStatus: No upgrade log present (probably fresh install) dmi.bios.date: 01/27/2026 dmi.bios.release: 1.24 dmi.bios.vendor: Dell Inc. dmi.bios.version: 1.24.0 dmi.board.name: 08214J dmi.board.vendor: Dell Inc. dmi.board.version: A00 dmi.chassis.type: 10 dmi.chassis.vendor: Dell Inc. dmi.ec.firmware.release: 1.21 dmi.modalias: dmi:bvnDellInc.:bvr1.24.0:bd01/27/2026:br1.24:efr1.21:svnDellInc.:pnXPS139340:pvr:rvnDellInc.:rn08214J:rvrA00:cvnDellInc.:ct10:cvr:sku0C87:pfaXPS: dmi.product.family: XPS dmi.product.name: XPS 13 9340 dmi.product.sku: 0C87 dmi.sys.vendor: Dell Inc. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2166520/+subscriptions
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