Kernel Bug Tracker – Bug 45311
[PATCH]After the brightness level decreasing it's not possible to increase it back higher some limited level (Samsung RV520 laptop)
Last modified: 2016-03-07 15:13:35 UTC
At the kernel >= 3.4 (samsung-laptop module) there has been appeared a Samsung RV520 laptop support (Product Name: RV420/RV520/RV720/E3530/S3530/E3420/E3520).
But the trouble with brightness adjustment exists:
When I try to change the brightness level, the maximum brightness limit becomes very low (~20...30%). Then, when I press <Fn + Up> (brightness up) further, a backlight is blinking for a short time, but the brightness level doesn't change. <Fn + Down> (brightness down) works well.
If I unplug the supply cable and then plug it back, the brightness level becomes maximum (100%). But after decreasing the brightness level the problem with <Fn + Up> repeats again.
> # cat /sys/devices/platform/samsung/backlight/samsung/max_brightness
> # echo 8 > /sys/devices/platform/samsung/backlight/samsung/actual_brightness
> -bash: /sys/devices/platform/samsung/backlight/samsung/actual_brightness: Permission denied
But the backlight is blinking for a short time, if I execute this:
> # echo 8 > /sys/devices/platform/samsung/backlight/samsung/brightness
I've updated kernel up to 3.5.0 ― the situation is the same: after the brightness level decreasing it's not possible to increase it back higher some limited level. That's some console output (after <Fn + Down> to min and <Fn + Up> to "max"):
> $ cat /sys/devices/platform/samsung/backlight/samsung/actual_brightness
> $ cat /sys/devices/platform/samsung/backlight/samsung/brightness
> $ cat /sys/devices/platform/samsung/backlight/samsung/max_brightness
The workaround is a using the rebuilt <samsung-laptop.ko> module (with the attached <samsung-laptop.ko> and <Makefile>).
Created attachment 76471 [details]
The <samsing-laptop> source (from a too old kernel version) with added RV520 support
Created attachment 76491 [details]
<Makefile> for building the module with attached <samsung-laptop.c>