Public bug reported:
Summary: Backlight control and display resume broken after upgrade to
linux-image-7.0.0-28-generic (regression from 7.0.0-27-generic)
Hardware: Dell Latitude 5490, Intel Core i5-8350U, Intel UHD Graphics 620
Distro: Kubuntu 26.04 LTS
Session: Wayland, KDE Plasma 6.6.5
Description:
After upgrading the kernel from linux-image-7.0.0-27-generic to
linux-image-7.0.0-28-generic, two related display issues appeared:
1. Backlight brightness control stopped working entirely. Neither the
keyboard brightness keys nor the Plasma brightness slider have any
effect on the actual screen brightness. Writing directly to
/sys/class/backlight/intel_backlight/brightness as root also has no
visible effect on screen brightness, even though the value is
correctly stored in the file (verified with `cat`).
2. After suspending the laptop (sleep) and waking it up, the display
stays black / never lights up again, while audio and the rest of
the system remain functional (system is clearly awake, just no
video output). A full power-off and power-on is required to recover;
normal resume-from-sleep is not possible.
Steps to reproduce:
1. Boot with kernel 7.0.0-28-generic
2. Try changing brightness via keyboard keys or Plasma slider -> no
change in actual screen brightness
3. Suspend the laptop and wake it up -> screen stays black, audio still
works
Expected behavior:
Brightness control and resume-from-suspend should work as they did
previously.
Additional testing:
Booting the previous kernel, linux-image-7.0.0-27-generic, on the same
hardware/session resolves both issues completely — brightness control
and suspend/resume both work correctly. This strongly suggests a
regression introduced between 7.0.0-27-generic and 7.0.0-28-generic,
likely in the i915 driver or associated ACPI/backlight handling.
Kernel cmdline used for testing (both kernels):
acpi_backlight=native was added during troubleshooting but had no
effect on the issue either way.
Workaround:
Pinning/holding the system to linux-image-7.0.0-27-generic via
apt-mark hold resolves both issues.
ProblemType: Bug
DistroRelease: Ubuntu 26.04
Package: linux-image-7.0.0-28-generic 7.0.0-28.28
ProcVersionSignature: Ubuntu 7.0.0-27.27-generic 7.0.6
Uname: Linux 7.0.0-27-generic x86_64
ApportVersion: 2.34.0-0ubuntu2
Architecture: amd64
AudioDevicesInUse:
USER PID ACCESS COMMAND
/dev/snd/controlC0: andrey 1553 F.... pipewire
andrey 1567 F.... wireplumber
/dev/snd/pcmC0D0p: andrey 1553 F...m pipewire
/dev/snd/seq: andrey 1553 F.... pipewire
CasperMD5CheckResult: unknown
CurrentDesktop: KDE
Date: Wed Jul 22 23:36:18 2026
InstallationDate: Installed on 2026-04-28 (86 days ago)
InstallationMedia: Kubuntu 26.04 "Resolute Raccoon" - Release amd64 (20260423)
Lsusb:
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 001 Device 002: ID 0bda:58f6 Realtek Semiconductor Corp.
Integrated_Webcam_HD
Bus 001 Device 004: ID 0a5c:5832 Broadcom Corp. BCM5880 Secure Applications
Processor Smartcard reader
Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
MachineType: Dell Inc. Latitude 5490
ProcFB: 0 i915drmfb
ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-7.0.0-27-generic
root=UUID=75c737ca-9493-4a20-969c-32867fc21eac ro rootflags=subvol=@ quiet
cryptdevice=UUID=c480f37d-597e-41d4-b18a-235da99384b2:luks-c480f37d-597e-41d4-b18a-235da99384b2
root=/dev/mapper/luks-c480f37d-597e-41d4-b18a-235da99384b2 splash
acpi_backlight=native
PulseList: Error: command ['pacmd', 'list'] failed with exit code 1: No
PulseAudio daemon running, or not running as session daemon.
SourcePackage: linux
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 03/06/2025
dmi.bios.release: 1.40
dmi.bios.vendor: Dell Inc.
dmi.bios.version: 1.40.0
dmi.board.name: 0DH2HV
dmi.board.vendor: Dell Inc.
dmi.board.version: A00
dmi.chassis.type: 10
dmi.chassis.vendor: Dell Inc.
dmi.modalias:
dmi:bvnDellInc.:bvr1.40.0:bd03/06/2025:br1.40:svnDellInc.:pnLatitude5490:pvr:rvnDellInc.:rn0DH2HV:rvrA00:cvnDellInc.:ct10:cvr:sku0816:pfaLatitude:
dmi.product.family: Latitude
dmi.product.name: Latitude 5490
dmi.product.sku: 0816
dmi.sys.vendor: Dell Inc.
** Affects: linux (Ubuntu)
Importance: Undecided
Status: New
** Tags: amd64 apport-bug resolute wayland-session
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https://bugs.launchpad.net/bugs/2161568
Title:
Summary: Backlight control and display resume broken after upgrade to
linux-image-7.0.0-28-generic (regression from 7.0.0-27-generic)
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