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New kernel parameters

As of version 4.1 the "video.use_native_backlight=1" is now obsolete and ignored by the kernel.

The new parameter is "acpi_backlight=[video|vendor|native|none]" [1]

I will go ahead and change this section in a few hours if there are no objections.


Head on a Stick (talk) 10:21, 4 October 2015 (UTC)

+1, latest supported kernel version on Arch is 4.1 so articles should be updated accordingly. -- Alad (talk) 10:46, 4 October 2015 (UTC)

xbacklight workaround

Quick and dirty script to emulate xbacklight to when it fails to recognize your video card. Works on Samsung Activ Book 9 lite with a (radeon_bl0) card.

# It assumes only one directory in /sys/class/backlight/, edit if necessary!


case ${1:0:1} in
    NEW=$[ $CUR * 100 / $MAX ${1:0:1} ${1:1} ]
    echo usage: $0 [+-]brigthness_percentage
    exit -1

echo $[ $NEW * $MAX / 100 ] | sudo tee /sys/class/backlight/*/brightness > /dev/null && echo $NEW

May be useful to add a sudo nopasswod entry also:

%wheel ALL=(ALL) NOPASSWD: /usr/bin/tee /sys/class/backlight/[[\:alpha\:]]*/brightness

—This unsigned comment is by Fmatheus (talk) 15:16, 19 May 2016‎. Please sign your posts with ~~~~!

Why not use Acpid#Enabling_backlight_control ? -- Alad (talk) 13:25, 19 May 2016 (UTC)
Good reference. But, for some reason my radeon card (Temash HD 8250/8280G) does not shows up as acpi_video0, so I dont know how to do that, but will try mess with 'acpi_backlight' kernel parameter and see if it works. -- Fmatheus (talk) 23:49, 19 May 2016 (UTC)
And what does it shows up as? You've already used * instead of acpi_video0 in the paths, so I would have guessed that this is a trivial change... -- Lahwaacz (talk) 07:22, 20 May 2016 (UTC)
Good point, in this sense my script is analogous to /etc/acpi/handlers/bl, the diference been the card name (radeon_bl0). I create it as a xbacklight replacement since it does not recognize this card. I not using acpid to handle the special keys (did hardcoded in dwm :), but would be nice to have a package to handle that out of the box, than works also in console! -- Fmatheus (talk) 12:09, 20 May 2016 (UTC)
There is Backlight#acpilight :) Lahwaacz (talk) 12:16, 20 May 2016 (UTC)