Public bug reported:
Description:
After updating to kernel 7.0.0-28-generic on a Dell G5 laptop (hybrid graphics
setup), the display backlight drops to near-zero/unusable brightness as soon as
the display manager (GDM/login screen) loads.
During early boot (GRUB and initial splash screen), the screen
brightness remains normal. Rolling back to kernel 7.0.0-27-generic or
7.0.0-22-generic completely fixes the issue and restores full backlight
control.
Expected Behavior:
Display backlight should maintain normal brightness levels when transition to
GDM / desktop session occurs.
Actual Behavior:
Display backlight drops drastically to minimal output upon reaching GDM.
Steps to Reproduce:
Boot system using kernel 7.0.0-28-generic.
Wait for the boot sequence to transition from splash screen to GDM /
login screen.
Display brightness drops to near-zero.
System Information:
Hardware: Dell G5 Laptop
OS: Ubuntu 26.04
Affected Kernel: 7.0.0-28-generic (Regression)
Working Kernel: 7.0.0-27-generic / 7.0.0-22-generic
NVIDIA Driver Version: 595.71.05
Log Diagnostic Snippet (dmesg):
The kernel appears to register two competing ACPI video devices (GFX0 and
PEGP), creating conflicting backlight buses:
Plaintext
[ 0.228094] ACPI: [Firmware Bug]: BIOS _OSI(Linux) query ignored
[ 11.173678] ACPI: video: Video Device [GFX0] (multi-head: yes rom: no post:
no)
[ 11.191146] input: Video Bus as /devices/pci0000:00/acpi.video_bus.0/
[ 11.204954] ACPI: video: Video Device [PEGP] (multi-head: no rom: yes post:
no)
[ 11.205018] input: Video Bus as
/devices/pci0000:00/0000:00:01.0/acpi.video_bus.1/
Tested kernel parameters acpi_backlight=native and acpi_backlight=vendor, but
neither resolved the brightness drop at GDM initialization.
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
ApportVersion: 2.34.0-0ubuntu2
Architecture: amd64
CasperMD5CheckResult: pass
CurrentDesktop: ubuntu:GNOME
Date: Wed Jul 22 19:57:06 2026
InstallationDate: Installed on 2026-04-24 (89 days ago)
InstallationMedia: Ubuntu 26.04 "Resolute Raccoon" - Release amd64 (20260423.1)
MachineType: Dell Inc. G5 5590
ProcEnviron:
LANG=pt_BR.UTF-8
PATH=(custom, no user)
SHELL=/bin/bash
TERM=xterm-256color
XDG_RUNTIME_DIR=<set>
ProcFB:
0 i915drmfb
1 nvidia-drmdrmfb
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-7.0.0-28-generic
root=UUID=8a9d9f1b-8831-4873-b653-bd4d6aed24c3 ro quiet splash
acpi_backlight=vendor
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: 06/01/2023
dmi.bios.release: 1.25
dmi.bios.vendor: Dell Inc.
dmi.bios.version: 1.25.0
dmi.board.name: 04F57P
dmi.board.vendor: Dell Inc.
dmi.board.version: A00
dmi.chassis.type: 10
dmi.chassis.vendor: Dell Inc.
dmi.modalias:
dmi:bvnDellInc.:bvr1.25.0:bd06/01/2023:br1.25:svnDellInc.:pnG55590:pvr:rvnDellInc.:rn04F57P:rvrA00:cvnDellInc.:ct10:cvr:sku08EA:pfaGSeries:
dmi.product.family: GSeries
dmi.product.name: G5 5590
dmi.product.sku: 08EA
dmi.sys.vendor: Dell Inc.
** Affects: linux (Ubuntu)
Importance: Undecided
Status: New
** Tags: amd64 apport-bug kernel-daily-bug resolute wayland-session
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https://bugs.launchpad.net/bugs/2161579
Title:
Lost Bright after install kernel 7.0.0-28-generic on a Dell G5
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