linux-kernel - video breaks asus-laptop display switching

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Message-ID: <Pine.LNX.4.64.0712211433030.3239@0-11-d8-ea-8d-5b.dhcp.lbl.gov>
Date:	Fri, 21 Dec 2007 14:36:38 -0800 (PST)
From:	Andrei Gaponenko <andrei.gaponenko@...n.ch>
To:	linux-kernel@...r.kernel.org
cc:	rui.zhang@...el.com, corentincj@...aif.net,
	sziwan@...rs.sourceforge.net
Subject: video breaks asus-laptop display switching

Hi,

With 2.6.23 or newer (including 2.6.24-rc6) kernels, writing to the
/sys/devices/platform/asus-laptop/display file does not do anything:

Cold boot to single user, then connect an external monitor

# cat  /sys/devices/platform/asus-laptop/display
1

OK, only the built in LCD is enabled. Try to enable
the external monitor as well:

# echo 3 > /sys/devices/platform/asus-laptop/display

still no image on the external.

# cat  /sys/devices/platform/asus-laptop/display
1

Still "1", not the "3" we wrote. On the other hand if I boot with an
external monitor attached, the "display" file always contains 3, even
after writing 1 there, and there is image on both monitors.

In 2.6.22 I had to load asus-laptop by hand, but then display
switching worked nicely.  

I've noticed that if I do 

# rmmod video

display switching starts working again with the newer kernels.
The "video" module was auto-loaded on my system in 2.6.22, but
did not cause the conflict.

This is an ASUS Z71V based notebook (detected as M7V).

Regards,
Andrei

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