Public bug reported:
Description:
I installed Ubuntu 26.04 fresh on my Dell Latitude E6440. After the first `sudo
apt update` and upgrade, brightness control stopped working completely. The
brightness slider and Fn keys do not change the screen brightness.
Observations:
- Only `intel_backlight` is detected in `/sys/class/backlight/`.
- Brightness values can be written to
`/sys/class/backlight/intel_backlight/brightness`, but they do not affect the
panel.
- Tried GRUB parameters (`acpi_backlight=native`, `vendor`, `video`) — no
effect.
- Tried kernel downgrade (6.8 series) and upgrade (mainline 7.x) — issue
persists.
- Tried `brightnessctl`, `xrandr`, GNOME Brightness Restore extension — none
worked.
- BIOS brightness control works fine, so hardware is OK.
- This looks like a regression in the i915 driver or ACPI backlight handling
specific to Dell Latitude E6440.
Steps to reproduce:
1. Install Ubuntu 26.04 on Dell Latitude E6440.
2. Run `sudo apt update && sudo apt upgrade`.
3. Reboot and try brightness control (slider or Fn keys).
4. Brightness does not change.
Expected result:
Brightness slider and Fn keys should adjust screen brightness.
Actual result:
Brightness remains fixed regardless of slider or key input.
ProblemType: Bug
DistroRelease: Ubuntu 26.04
Package: linux-image-7.0.0-30-generic 7.0.0-30.30
ProcVersionSignature: Ubuntu 7.0.0-30.30-generic 7.0.12
Uname: Linux 7.0.0-30-generic x86_64
ApportVersion: 2.34.1-0ubuntu0.1
Architecture: amd64
AudioDevicesInUse:
USER PID ACCESS COMMAND
/dev/snd/controlC0: smit 3169 F.... wireplumber
/dev/snd/controlC1: smit 3169 F.... wireplumber
/dev/snd/seq: smit 3159 F.... pipewire
CasperMD5CheckResult: pass
CurrentDesktop: ubuntu:GNOME
Date: Tue Aug 25 21:26:25 2026
InstallationDate: Installed on 2026-08-25 (0 days ago)
InstallationMedia: Ubuntu 26.04 "Resolute Raccoon" - Release amd64 (20260423.1)
MachineType: Dell Inc. Latitude E6440
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=/vmlinuz-7.0.0-30-generic
root=/dev/mapper/ubuntu--vg-ubuntu--lv 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: 06/13/2019
dmi.bios.release: 65.24
dmi.bios.vendor: Dell Inc.
dmi.bios.version: A24
dmi.board.name: 04F8XM
dmi.board.vendor: Dell Inc.
dmi.board.version: A00
dmi.chassis.type: 9
dmi.chassis.vendor: Dell Inc.
dmi.modalias:
dmi:bvnDellInc.:bvrA24:bd06/13/2019:br65.24:svnDellInc.:pnLatitudeE6440:pvr00:rvnDellInc.:rn04F8XM:rvrA00:cvnDellInc.:ct9:cvr:sku05BD:pfa:
dmi.product.name: Latitude E6440
dmi.product.sku: 05BD
dmi.product.version: 00
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/2165048
Title:
Brightness control not working on Dell Latitude E6440 after Ubuntu
26.04 update
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