Public bug reported:
System
Machine: Lenovo ThinkPad X270 (model 20K5S35P00)
CPU: Intel Core i5-7200U
GPU: Intel HD Graphics 620 (i915 driver)
OS: Linux Mint 22.3 Cinnamon (based on Ubuntu 24.04)
Problem
Backlight brightness control stopped working after upgrading from kernel
6.17.0-40 to 7.0.0-28. The issue persists on 7.0.0-29 and 7.0.0-30.
Neither the Fn brightness keys, nor the Power Management GUI, nor direct
sysfs writes have any effect.
Symptoms
/sys/class/backlight/intel_backlight is present but writes have no
effect:
$ cat /sys/class/backlight/intel_backlight/type
raw
$ sudo tee /sys/class/backlight/intel_backlight/brightness <<< 200
# no change
Key dmesg line on affected kernels:
i915 0000:00:02.0: [drm] Skipping intel_backlight registration
On working kernel (6.17.0-40), this line is absent and brightness
control works normally via intel_backlight (type: raw, sysfs writes
effective, Fn keys functional).
Tested kernel parameters (none resolved the issue on 7.0.0-x):
acpi_backlight=native
acpi_backlight=native video.use_native_backlight=1
acpi_osi='!Windows 2012'
acpi_backlight=video → exposes acpi_video0 but brightness still unresponsive
Bisect
✅ Working: 6.17.0-40-generic
❌ Broken: 7.0.0-28-generic, 7.0.0-29-generic, 7.0.0-30-generic
Workaround
Booting on kernel 6.17.0-40-generic restores full brightness control.
** Affects: linux (Ubuntu)
Importance: Undecided
Status: New
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https://bugs.launchpad.net/bugs/2165049
Title:
Backlight brightness control broken on ThinkPad X270 with kernel
7.0.0-28 and later
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