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Old 10th November 2018
vns3 vns3 is offline
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Default Equivalent to Linux's /sys/class/backlight?

I have been messing around with xorg.conf on my laptops, in order to get the TearFree option working with the intel driver. On one machine it works great, but I have not figured out the second one yet.

By default Xorg uses the modesetting driver, but if I specify intel in xorg.conf, it works, seems more responsive, and looks a lot better.

The only problem is that brightness (via xbacklight) does not work when I have it configured this way.

In man intel there is this:
Option "Backlight" "string"
    Override the probed backlight control interface. Sometimes the automatically selected
 backlight interface may not correspond to the correct, or simply most useful, interface
 available on the system. This allows you to override that choice by specifying the entry
 under /sys/class/backlight to use.

    Default: Automatic selection.
... but the reference "/sys/class/backlight" is a Linux reference I think? I searched around and found that in Linux there is a file in the above path that gives you direct access to your brightness setting.

Does anyone know if OpenBSD has a file that gives you access to the backlight like described above?
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Old 10th November 2018
shep shep is offline
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Some laptops control brightness via microcontrollers and have hotkeys (Fn).

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Old 10th November 2018
vns3 vns3 is offline
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With the "modesetting" driver my fn keys do not work, but xbacklight does.

With the "intel" driver fn keys do not work, and xbacklight reports no errors but does not have any effect.

The link you provided was helpful. Toward the bottom it talks about what I am experiencing. (My device is eDP)

Embedded Display Port (eDP) v1.2 introduced a new display panel control 
protocol for backlight and other controls that works through the AUX channel.[2]
By default the i915 driver tries to use PWM to control backlight brightness, which 
might not work.

To set the backlight through writes to DPCD registers using the AUX channel 
set i915.enable_dpcd_backlight as kernel parameter or set in /etc/modprobe/i915.conf:
I am not sure how or if that translates to OpenBSD, but it is more info.
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