Public bug reported:
# Dimmer Max Screen Brightness in linux-image-7.0.0-28-generic
Updating from `linux-image-6.17.0-40-generic` to `linux-
image-7.0.0-28-generic` affected the maximum range of brightness of the
monitor could reach, permanently. The only solution so far was to boot
from 6.x instead of 7.x
This is the summary of everything I tried to fix it.
Here is a comprehensive summary report of the troubleshooting steps,
findings, and the final resolution regarding the display brightness
issue on your Dell Latitude 2-in-1.
------------------------------
## Troubleshooting Report: Screen Brightness Regression
Device: Dell Latitude 2-in-1 (Intel HD/UHD 620 Graphics)
Operating System: Ubuntu
Issue: Screen permanently dimmed after a system update; unable to reach
original maximum brightness.
Root Cause: Kernel driver regression in version 7.0.0-28-generic.
------------------------------
## Part 1: Summary of Attempted Approaches
During troubleshooting, we moved from user-space software overrides down
to low-level hardware kernel adjustments. Here is everything we tested:
### 1. Software Display-Server Overrides (xrandr)
* Approach: Attempted to forcefully scale up the brightness multiplier on the
active display output (eDP-1).
* Commands used: xrandr --output eDP-1 --brightness 1.3 --gamma 1.0:1.0:1.0
* Result: Failed. The commands executed without error, but the physical panel
brightness remained completely unchanged. This indicated that user-space
software was locked out of communicating with the hardware.
### 2. Desktop Environment Power Scheme Adjustments (gsettings)
* Approach: Attempted to disable GNOME's automatic ambient dimming and force
user-profile parameters to 100%.
* Commands used: gsettings set org.gnome.settings-daemon.plugins.power
idle-brightness 100
* Result: Failed. The adjustments did not alter the screen state, proving the
desktop environment’s GUI sliders were disconnected from the backend. [1]
### 3. Disabling Ambient Light Sensors (ALS)
* Approach: Stopped and masked the background daemon responsible for managing
the physical light sensor next to the webcam.
* Commands used: sudo systemctl mask iio-sensor-proxy.service
* Result: Failed. Masking the sensor did not restore brightness, ruling out
environmental light tracking bugs.
### 4. Direct Kernel File Injection (/sys/class/backlight)
* Approach: Inspected the Linux system's backlight directory to force raw
values straight into the driver.
* Initial State: The directory was entirely missing the proper intel_backlight
profile, pointing instead to a generic fallback placeholder (acpi_video0).
* Correction: Built a native Xorg hardware configuration profile
(20-intel.conf) to force the generation of the intel_backlight folder.
* Execution: Successfully exposed the true hardware ceiling (1023), but
executing echo 1023 | sudo tee .../brightness was still blocked by the active
system.
### 5. Kernel Boot Parameter Modification (/etc/default/grub)
* Approach: Appended explicit hardware instructions to the system loader,
testing intel_backlight=native, acpi_backlight=video, and acpi_backlight=native.
* Result: Failed. The configurations were rejected or ignored by the new
graphics framework architecture.
------------------------------
## Part 2: Critical Discovery & Final Resolution## The Breakthrough
Observation
The defining clue occurred during reboots: The display achieved full, blinding
maximum brightness during the Dell splash logo and initial Ubuntu loading
sequence. The aggressive dimming only triggered the exact millisecond the user
desktop environment loaded.
This confirmed the hardware was intact, and that the fault lay purely with how
the newly updated operating system kernel interacted with the integrated Intel
graphics chip upon initialization.
### The Working Solution
By accessing the Advanced options for Ubuntu menu via the GRUB
bootloader, we bypassed the update and launched the computer using the
previous kernel profile:
* Working Kernel: 6.17.0-40-generic
* Buggy Kernel: 7.0.0-28-generic
Booting into the 6.17 series instantly restored the display to its
proper, full maximum hardware capability.
ProblemType: Bug
DistroRelease: Ubuntu 24.04
Package: linux-image-7.0.0-28-generic 7.0.0-28.28~24.04.1
ProcVersionSignature: Ubuntu 7.0.0-28.28~24.04.1-generic 7.0.12
Uname: Linux 7.0.0-28-generic x86_64
ApportVersion: 2.28.2-0ubuntu0.1
Architecture: amd64
AudioDevicesInUse:
USER PID ACCESS COMMAND
/dev/snd/controlC0: agc 5283 F.... wireplumber
/dev/snd/seq: agc 5276 F.... pipewire
CRDA: N/A
CasperMD5CheckResult: pass
CurrentDesktop: ubuntu:GNOME
Date: Fri Jul 24 09:08:27 2026
EcryptfsInUse: Yes
InstallationDate: Installed on 2025-05-24 (426 days ago)
InstallationMedia: Ubuntu 24.04.2 LTS "Noble Numbat" - Release amd64 (20250215)
MachineType: Dell Inc. Latitude 5300 2-in-1
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=6959d48c-4a01-432c-9b12-d4678c90a83c ro quiet splash vt.handoff=7
RelatedPackageVersions:
linux-restricted-modules-7.0.0-28-generic N/A
linux-backports-modules-7.0.0-28-generic N/A
linux-firmware 20240318.git3b128b60-0ubuntu2.27
SourcePackage: linux-hwe-7.0
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 08/05/2025
dmi.bios.release: 1.37
dmi.bios.vendor: Dell Inc.
dmi.bios.version: 1.37.0
dmi.board.name: 0J9C2F
dmi.board.vendor: Dell Inc.
dmi.board.version: A00
dmi.chassis.asset.tag: 8085105
dmi.chassis.type: 31
dmi.chassis.vendor: Dell Inc.
dmi.modalias:
dmi:bvnDellInc.:bvr1.37.0:bd08/05/2025:br1.37:svnDellInc.:pnLatitude53002-in-1:pvr:rvnDellInc.:rn0J9C2F:rvrA00:cvnDellInc.:ct31:cvr:sku08B6:pfaLatitude:
dmi.product.family: Latitude
dmi.product.name: Latitude 5300 2-in-1
dmi.product.sku: 08B6
dmi.sys.vendor: Dell Inc.
** Affects: linux-hwe-7.0 (Ubuntu)
Importance: Undecided
Status: New
** Tags: amd64 apport-bug noble wayland-session
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https://bugs.launchpad.net/bugs/2161741
Title:
MAX BRIGHTNESS AFFECTED (REDUCED)
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