[Bug 84561] [ivb] Intel backlight does not adjust, but only turns on/off in kernel 3.16 on Samsung 880Z5E laptop

[bugzilla-daemon at bugzilla.kernel.org]

https://bugzilla.kernel.org/show_bug.cgi?id=84561

--- Comment #13 from Laszlo KREKACS <laszlo.krekacs.list at gmail.com> ---
Aaron:

> On Vitaliy's system, the acpi_videoX interface works while the intel_backlight 
> doesn't. Is your system the same? From your description, it seems none of the 
> interfaces work.  And since which kernel version you start to have this problem or you always have this problem?

It never worked by default (tested on ubuntu 13.10, 14.04, 14.10 beta)
I tried now with these kernel versions 
(all from ubuntu package, I'm on 14.10 beta atm):
3.11.0-17 NOT WORKING BY DEFAULT
3.11.0-18 NOT WORKING BY DEFAULT
3.13.0-36 NOT WORKING BY DEFAULT
3.16.0-21 NOT WORKING BY DEFAULT

I always checked against /sys/class/backlight/intel_backlight/brightness.

After using "video.use_native_backlight=0", and checking against:
echo "5" > /sys/class/backlight/acpi_video0/brightness #WORKS
echo "5" > /sys/class/backlight/acpi_video1/brightness #WORKS
echo "5" > /sys/class/backlight/acpi_video1/brightness #NOT WORKING

So I think my case is identical to Vitaliy's case.

Vitaliy:
I have the exact same BIOS version:
P02ADH.008.130604.SK

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