dualhead broken with 6.12.2

[Alex Deucher]

On 4/14/09, di dit <didit21 at gmail.com> wrote:
> While upgrading from version 6.9.0 to 6.12.2, dualhead stopped
>  working. I didn't succeed to have
>  the two identical monitors displaying different content. Clone mode works fine.
>
>  Trying to setup dualhead with "xrandr --output DVI-1 --left-of DVI-0"
>  or similar commands turn one
>  monitor black (standby mode?) while the other output is as expected.
>
>  I already submitted a bug to debian BTS where the relevant logs can be found
>  http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=523589
>
>  Maybe it is related to the following bug, but I'm not sure:
>  http://bugs.freedesktop.org/show_bug.cgi?id=21050
>

Both heads are probably using the same crtc, but xrandr isn't smart
enough to assign a different one in the dualhead case.  You can see
what crtc is in use by running xrandr --verbose.  You can assign a
different crtc to the other head like so:
xrandr --output DVI-1 --crtc 1 --mode 1280x1024 --left-of DVI-0

Alex