[XE303C Chromebook] Turn off screen using DPMS doesn't work!

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[XE303C Chromebook] Turn off screen using DPMS doesn't work!

Postby doragasu1 » Mon Feb 01, 2016 4:09 pm

I have been trying to configure screen to power off each time I lock the session. I have tested two methods: built-in i3lock dpms capabilities and xset:

i3lock is supposed to turn off screen if invoked with -d switch, but it does not work. Screen goes black, but I can see backlight is powered.
"sleep 1 && xset dpms force off" causes the same behavior: screen goes black, but backlight does not turn off.

I have observed that leaving the laptop unused for some minutes also makes the screen go black but the backlight never powers off!

How can I make screen to completely power off?
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Re: [XE303C Chromebook] Turn off screen using DPMS doesn't w

Postby WarheadsSE » Mon Feb 01, 2016 4:14 pm

What kernel is in use?

The GPIO, btw, should be ~ 25
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Re: [XE303C Chromebook] Turn off screen using DPMS doesn't w

Postby doragasu1 » Tue Feb 02, 2016 1:27 pm

Default kernel (linux-peach, latest version). Uname -a reports:
Linux arch-chrome 3.8.11-3-ARCH #1 SMP Wed Jan 20 13:44:59 MST 2016 armv7l GNU/Linux

Is it safe playing with GPIO25? It's not exported by default. I have tried exporting it, and by default "direction" is configured as "in". I'm afraid I might damage something if I set it to out and it is connected to other output or low impedance subcircuit.

EDIT: BTW, I'm using xf86-video-armsoc-git driver, maybe this is related to the problem (also I do not know which is the recommended video driver for my chromebook, but this one seems to run nice).
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Re: [XE303C Chromebook] Turn off screen using DPMS doesn't w

Postby doragasu1 » Wed Feb 03, 2016 8:30 am

I have tested also with xf86-video-armsoc-chromium and xf86-video-fbdev and behaviour is the same: screen goes black but backlight doesn't power off!
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