[Bug 2161423] [NEW] Kernel Regression Report: Internal Display Brightness No Longer Works on HP Envy x360 15-bp1xx (Kernel 7.0.0-28)

Public bug reported: A regression has been introduced in Linux kernel **7.0.0-28-generic** that prevents adjustment of the internal display brightness on an HP Envy x360 15-bp1xx laptop. The issue appeared immediately after updating from kernel **7.0.0-27-generic** to **7.0.0-28-generic**. Under kernel **7.0.0-28**, the GNOME brightness slider functions normally and the kernel exposes the expected `intel_backlight` interface. The reported brightness value changes correctly when the slider is moved or when values are written manually to the sysfs backlight interface. However, the physical brightness of the internal LCD panel never changes. Booting the same system using **kernel 7.0.0-27-generic** restores normal brightness control without any other configuration changes. This strongly indicates a kernel regression introduced between versions 7.0.0-27 and 7.0.0-28. ## Hardware Laptop: * HP Envy x360 Convertible 15-bp1xx Graphics: * Intel UHD Graphics 620 (internal display controller) * NVIDIA GeForce MX150 (Optimus hybrid graphics) Graphics mode: * `prime-select on-demand` NVIDIA driver: * Version 580.159.03 ## Software Ubuntu release: * Ubuntu 26.04 LTS Working kernel: * 7.0.0-27-generic Broken kernel: * 7.0.0-28-generic Backlight device: ``` /sys/class/backlight/intel_backlight ``` Maximum brightness: ``` 1023 ``` Example brightness value: ``` 638 ``` Kernel command line: ``` BOOT_IMAGE=/boot/vmlinuz-7.0.0-28-generic root=<UUID> ro quiet splash crashkernel=2G-4G:320M,4G-32G:512M,32G-64G:1024M,64G-128G:2048M,128G-:4096M ``` No custom backlight-related kernel parameters are present. ## Steps to Reproduce 1. Boot Ubuntu using Linux kernel 7.0.0-28-generic. 2. Open GNOME Settings → Display or use the brightness hotkeys. 3. Move the brightness slider across its full range. Alternatively: ``` echo <value> | sudo tee /sys/class/backlight/intel_backlight/brightness ``` using different values. ## Expected Result The brightness of the internal LCD panel should change according to the requested brightness value. ## Actual Result * The GNOME brightness slider moves normally. * The value in `/sys/class/backlight/intel_backlight/brightness` changes correctly. * Writes to the sysfs backlight interface succeed. * No errors are reported. * The physical brightness of the display remains unchanged. ## Regression Confirmation The issue disappears completely after booting kernel **7.0.0-27-generic**. No hardware changes, firmware changes, BIOS changes, or driver changes are required. The only difference is the kernel version. ## Additional Information * The laptop dual-boots Windows. * Brightness adjustment functions normally under Windows. * `intel_backlight` is detected correctly. * NVIDIA reports the internal display is not directly attached (`Disp.A Off`), consistent with Intel driving the internal panel in Optimus mode. * The issue therefore appears to affect the Intel backlight control path rather than the NVIDIA driver. ## Regression Assessment This appears to be a regression introduced between Linux kernels: * 7.0.0-27-generic (working) * 7.0.0-28-generic (broken) Potential areas worth investigating include: * Intel i915 display/backlight changes * ACPI backlight handling * HP firmware quirks * eDP panel backlight programming The regression is fully reproducible and disappears when reverting to the previous kernel. ProblemType: Bug DistroRelease: Ubuntu 26.04 Package: linux-image-7.0.0-28-generic 7.0.0-28.28 ProcVersionSignature: Ubuntu 7.0.0-28.28-generic 7.0.12 Uname: Linux 7.0.0-28-generic x86_64 NonfreeKernelModules: nvidia_modeset nvidia ApportVersion: 2.34.0-0ubuntu2 Architecture: amd64 AudioDevicesInUse: USER PID ACCESS COMMAND /dev/snd/controlC0: robin 5539 F.... wireplumber /dev/snd/seq: robin 5525 F.... pipewire CasperMD5CheckResult: pass CurrentDesktop: ubuntu:GNOME Date: Tue Jul 21 13:16:47 2026 InstallationDate: Installed on 2026-07-19 (2 days ago) InstallationMedia: Ubuntu 26.04 "Resolute Raccoon" - Release amd64 (20260423.1) Lsusb: Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub Bus 001 Device 002: ID 04f3:0235 Elan Microelectronics Corp. Optical Mouse Bus 001 Device 003: ID 0bda:58e6 Realtek Semiconductor Corp. HP Wide Vision FHD Camera Bus 001 Device 004: ID 8087:0a2a Intel Corp. Bluetooth wireless interface Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub MachineType: HP HP ENVY x360 Convertible 15-bp1xx 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=/boot/vmlinuz-7.0.0-28-generic root=UUID=8030bc2b-215f-43df-87c0-d9c8fe75e7c5 ro quiet splash 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: 07/24/2017 dmi.bios.release: 15.22 dmi.bios.vendor: Insyde dmi.bios.version: F.22 dmi.board.asset.tag: Type2 - Board Asset Tag dmi.board.name: 83C9 dmi.board.vendor: HP dmi.board.version: 32.60 dmi.chassis.asset.tag: Chassis Asset Tag dmi.chassis.type: 10 dmi.chassis.vendor: HP dmi.chassis.version: Chassis Version dmi.ec.firmware.release: 32.60 dmi.modalias: dmi:bvnInsyde:bvrF.22:bd07/24/2017:br15.22:efr32.60:svnHP:pnHPENVYx360Convertible15-bp1xx:pvrType1ProductConfigId:rvnHP:rn83C9:rvr32.60:cvnHP:ct10:cvrChassisVersion:sku1ZA17AV:pfa103C_5335KVHPEnvy: dmi.product.family: 103C_5335KV HP Envy dmi.product.name: HP ENVY x360 Convertible 15-bp1xx dmi.product.sku: 1ZA17AV dmi.product.version: Type1ProductConfigId dmi.sys.vendor: HP ** Affects: linux (Ubuntu) Importance: Undecided Status: New ** Tags: amd64 apport-bug resolute wayland-session -- You received this bug notification because you are subscribed to linux in Ubuntu. Matching subscriptions: Bgg, Bmail, Nb https://bugs.launchpad.net/bugs/2161423 Title: Kernel Regression Report: Internal Display Brightness No Longer Works on HP Envy x360 15-bp1xx (Kernel 7.0.0-28) Status in linux package in Ubuntu: New Bug description: A regression has been introduced in Linux kernel **7.0.0-28-generic** that prevents adjustment of the internal display brightness on an HP Envy x360 15-bp1xx laptop. The issue appeared immediately after updating from kernel **7.0.0-27-generic** to **7.0.0-28-generic**. Under kernel **7.0.0-28**, the GNOME brightness slider functions normally and the kernel exposes the expected `intel_backlight` interface. The reported brightness value changes correctly when the slider is moved or when values are written manually to the sysfs backlight interface. However, the physical brightness of the internal LCD panel never changes. Booting the same system using **kernel 7.0.0-27-generic** restores normal brightness control without any other configuration changes. This strongly indicates a kernel regression introduced between versions 7.0.0-27 and 7.0.0-28. ## Hardware Laptop: * HP Envy x360 Convertible 15-bp1xx Graphics: * Intel UHD Graphics 620 (internal display controller) * NVIDIA GeForce MX150 (Optimus hybrid graphics) Graphics mode: * `prime-select on-demand` NVIDIA driver: * Version 580.159.03 ## Software Ubuntu release: * Ubuntu 26.04 LTS Working kernel: * 7.0.0-27-generic Broken kernel: * 7.0.0-28-generic Backlight device: ``` /sys/class/backlight/intel_backlight ``` Maximum brightness: ``` 1023 ``` Example brightness value: ``` 638 ``` Kernel command line: ``` BOOT_IMAGE=/boot/vmlinuz-7.0.0-28-generic root=<UUID> ro quiet splash crashkernel=2G-4G:320M,4G-32G:512M,32G-64G:1024M,64G-128G:2048M,128G-:4096M ``` No custom backlight-related kernel parameters are present. ## Steps to Reproduce 1. Boot Ubuntu using Linux kernel 7.0.0-28-generic. 2. Open GNOME Settings → Display or use the brightness hotkeys. 3. Move the brightness slider across its full range. Alternatively: ``` echo <value> | sudo tee /sys/class/backlight/intel_backlight/brightness ``` using different values. ## Expected Result The brightness of the internal LCD panel should change according to the requested brightness value. ## Actual Result * The GNOME brightness slider moves normally. * The value in `/sys/class/backlight/intel_backlight/brightness` changes correctly. * Writes to the sysfs backlight interface succeed. * No errors are reported. * The physical brightness of the display remains unchanged. ## Regression Confirmation The issue disappears completely after booting kernel **7.0.0-27-generic**. No hardware changes, firmware changes, BIOS changes, or driver changes are required. The only difference is the kernel version. ## Additional Information * The laptop dual-boots Windows. * Brightness adjustment functions normally under Windows. * `intel_backlight` is detected correctly. * NVIDIA reports the internal display is not directly attached (`Disp.A Off`), consistent with Intel driving the internal panel in Optimus mode. * The issue therefore appears to affect the Intel backlight control path rather than the NVIDIA driver. ## Regression Assessment This appears to be a regression introduced between Linux kernels: * 7.0.0-27-generic (working) * 7.0.0-28-generic (broken) Potential areas worth investigating include: * Intel i915 display/backlight changes * ACPI backlight handling * HP firmware quirks * eDP panel backlight programming The regression is fully reproducible and disappears when reverting to the previous kernel. ProblemType: Bug DistroRelease: Ubuntu 26.04 Package: linux-image-7.0.0-28-generic 7.0.0-28.28 ProcVersionSignature: Ubuntu 7.0.0-28.28-generic 7.0.12 Uname: Linux 7.0.0-28-generic x86_64 NonfreeKernelModules: nvidia_modeset nvidia ApportVersion: 2.34.0-0ubuntu2 Architecture: amd64 AudioDevicesInUse: USER PID ACCESS COMMAND /dev/snd/controlC0: robin 5539 F.... wireplumber /dev/snd/seq: robin 5525 F.... pipewire CasperMD5CheckResult: pass CurrentDesktop: ubuntu:GNOME Date: Tue Jul 21 13:16:47 2026 InstallationDate: Installed on 2026-07-19 (2 days ago) InstallationMedia: Ubuntu 26.04 "Resolute Raccoon" - Release amd64 (20260423.1) Lsusb: Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub Bus 001 Device 002: ID 04f3:0235 Elan Microelectronics Corp. Optical Mouse Bus 001 Device 003: ID 0bda:58e6 Realtek Semiconductor Corp. HP Wide Vision FHD Camera Bus 001 Device 004: ID 8087:0a2a Intel Corp. Bluetooth wireless interface Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub MachineType: HP HP ENVY x360 Convertible 15-bp1xx 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=/boot/vmlinuz-7.0.0-28-generic root=UUID=8030bc2b-215f-43df-87c0-d9c8fe75e7c5 ro quiet splash 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: 07/24/2017 dmi.bios.release: 15.22 dmi.bios.vendor: Insyde dmi.bios.version: F.22 dmi.board.asset.tag: Type2 - Board Asset Tag dmi.board.name: 83C9 dmi.board.vendor: HP dmi.board.version: 32.60 dmi.chassis.asset.tag: Chassis Asset Tag dmi.chassis.type: 10 dmi.chassis.vendor: HP dmi.chassis.version: Chassis Version dmi.ec.firmware.release: 32.60 dmi.modalias: dmi:bvnInsyde:bvrF.22:bd07/24/2017:br15.22:efr32.60:svnHP:pnHPENVYx360Convertible15-bp1xx:pvrType1ProductConfigId:rvnHP:rn83C9:rvr32.60:cvnHP:ct10:cvrChassisVersion:sku1ZA17AV:pfa103C_5335KVHPEnvy: dmi.product.family: 103C_5335KV HP Envy dmi.product.name: HP ENVY x360 Convertible 15-bp1xx dmi.product.sku: 1ZA17AV dmi.product.version: Type1ProductConfigId dmi.sys.vendor: HP To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2161423/+subscriptions