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
--
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Bugs, which is subscribed to Ubuntu.
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)
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