[Bug 220326] New: Mismatch between the meanings of brightness and actual_brightness

bugzilla-daemon at kernel.org bugzilla-daemon at kernel.org
Tue Jul 8 16:35:06 UTC 2025


https://bugzilla.kernel.org/show_bug.cgi?id=220326

            Bug ID: 220326
           Summary: Mismatch between the meanings of brightness and
                    actual_brightness
           Product: Drivers
           Version: 2.5
          Hardware: AMD
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P3
         Component: Video(DRI - non Intel)
          Assignee: drivers_video-dri at kernel-bugs.osdl.org
          Reporter: kernvirt at gmail.com
        Regression: No

Amd ryzen 5 7520u (Mendocino)
/sys/class/backlight/amdgpu_bl1/type = raw
max_brightness = 255
Bug: The meaning of brightness does not match the meaning of actual_brightness
in /sys/class/backlight/amdgpu_bl1. For example, I set brightness 160 and
actual_brightness at this moment = 100, Also for example 80/25. In other words,
the higher the brightness level I set, the larger the adjustment step per
brightness percentage becomes of actual_brightness, for example 0-4% brightness
in kde = 0 in actual_brightness, While the difference between 40 and 45% is
already 11 units in actual_brightness. 
Tested kernels:6.13-6.15.5
Distro - debian/fedora/arch
I've tried:
-kernel parameters: acpi_backlight=video/vendor/native
amdgpu.backlight=0
-brightnessctl, acpilight 
-tty, DE
Everywhere the result is the same as I described above.

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