https://bugzilla.kernel.org/show_bug.cgi?id=212003
Bug ID: 212003
Summary: Regression: Screen ignores ACPI intel_backlight sysfs
values greater than 1
Product: ACPI
Version: 2.5
Kernel Version: Linux 5.11.2-arch1-1 x86_64
Hardware: Intel
OS: Linux
Tree: Mainline
Status: NEW
Severity: normal
Priority: P1
Component: Other
Assignee: [email protected]
Reporter: [email protected]
Regression: No
Created attachment 295535
--> https://bugzilla.kernel.org/attachment.cgi?id=295535&action=edit
dmesg
In a recent update, the values of
/sys/class/backlight/intel_backlight/brightness no longer correspond with my
screen brightness.
Steps to reproduce:
Change the value of /sys/class/backlight/intel_backlight/brightness to an
integer from 0-255 (where 255 is the max_brightness).
Expected results:
At value 0, the screen is off, and at values 1-255, the screen gradually goes
from dim to full brightness.
Actual results:
At value 0, the screen is off, and at values 1-255, the screen is the same
brightness.
My system:
My system requires the i915.enable_dpcd_backlight=1 kernel parameter for this
feature to work. But I performed a normal Arch system upgrade to 5.11.2-arch1-1
on 2/21/2021, which has caused the behavior above. My linux version before the
upgrade was 5.10.16.arch1-1.
I tried many values of the other kernel parameters acpi_backlight but they did
not resolve anything. My hardware is Dell XPS 17 9700 with an NVIDIA Optimus
graphics hardware. The optimus setup uses i915 for the intel modesetting and
nvidia for the main nvidia setting.
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