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Old 30th March 2017
attilio attilio is offline
Port Guard
Join Date: Jun 2015
Posts: 34
Default I would like to understand how brightness works

On a laptop where
$ xbacklight...
doesn't work, I tried
$ xrandr --output outputName --brightness brightnessValue
and it works.
Reading something I understood that xrandr produces only a software modification.
On the other hand, xbacklight (if working) would produce a hardware modification.
I observed something I'm not able to understand.
Out of X (console mode) I'm not able to modify brightness with
$ wsconsctl display.brightness=value (obsd 6.0).
Inside X (after startx) I'm able to modify brightness with xrandr and, if I exit X, modification persists also in console mode.

The questions are:
1) is it correct to think that X is able to do software modification that persists out of X?
2)Which kind of modification does "wsconsctl display.brightness=..." produce? Hw or sw?
3) can anyone suggest me something to read if I want to understand more deeply how
brightness works?
Have a good day.
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