Public bug reported:
Dell Latitude 5491, BIOS 1.39.0, kernel 7.0.0-29-generic (Ubuntu 26.04).
Screen brightness cannot be controlled at all - neither via GNOME slider,
physical Fn keys, nor command line (brightnessctl, xrandr --brightness).
brightnessctl successfully updates intel_backlight sysfs value but has
no visible effect on screen.
Tested without success:
- acpi_backlight=vendor / native / video (individually and combined
with video.use_native_backlight=0)
- i915.enable_dpcd_backlight=0
- modprobe dell_laptop, dell_wmi, dell_smbios (loaded, no new backlight device)
- prime-select intel/nvidia/on-demand
- gsd-power restart
- fwupd firmware check (already latest)
- Brightness works correctly from BIOS setup screen itself, confirming
hardware is functional
Similar issue reported for Dell Latitude 7490 on kernel 7.0.0-28
(Linux Mint forums), suggesting a regression affecting this kernel
series on Dell Latitude models.
ProblemType: Bug
DistroRelease: Ubuntu 26.04
Package: linux-image-7.0.0-29-generic 7.0.0-29.29
ProcVersionSignature: Ubuntu 7.0.0-29.29-generic 7.0.12
Uname: Linux 7.0.0-29-generic x86_64
ApportVersion: 2.34.1-0ubuntu0.1
Architecture: amd64
AudioDevicesInUse:
USER PID ACCESS COMMAND
/dev/snd/controlC0: samuel 3186 F.... wireplumber
/dev/snd/seq: samuel 3170 F.... pipewire
CasperMD5CheckResult: pass
CurrentDesktop: ubuntu:GNOME
Date: Tue Aug 18 00:29:08 2026
InstallationDate: Installed on 2026-08-17 (0 days ago)
InstallationMedia: Ubuntu 26.04 "Resolute Raccoon" - Release amd64 (20260423.1)
MachineType: Dell Inc. Latitude 5491
ProcEnviron:
LANG=fr_FR.UTF-8
PATH=(custom, no user)
SHELL=/bin/bash
TERM=xterm-256color
XDG_RUNTIME_DIR=<set>
ProcFB: 0 i915drmfb
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-7.0.0-29-generic
root=UUID=a9b6bf24-9766-4d35-9a5c-ac2db4a1c917 ro quiet splash
acpi_backligt=vendor video.use_native_blacklight=0
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: 04/07/2025
dmi.bios.release: 1.39
dmi.bios.vendor: Dell Inc.
dmi.bios.version: 1.39.0
dmi.board.name: 0VK7YF
dmi.board.vendor: Dell Inc.
dmi.board.version: A00
dmi.chassis.type: 10
dmi.chassis.vendor: Dell Inc.
dmi.modalias:
dmi:bvnDellInc.:bvr1.39.0:bd04/07/2025:br1.39:svnDellInc.:pnLatitude5491:pvr:rvnDellInc.:rn0VK7YF:rvrA00:cvnDellInc.:ct10:cvr:sku0818:pfaLatitude:
dmi.product.family: Latitude
dmi.product.name: Latitude 5491
dmi.product.sku: 0818
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/2163706
Title:
Screen brightness bug
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