[Nouveau] videowall

[Ilia Mirkin]

On Wed, Jan 29, 2014 at 8:18 PM, Christian Stöveken
<christian.stoeveken at gmail.com> wrote:
> So I had this crazy idea to put together a cheap video wall in my local
> hackerspace using
> a lot of screens suffering from planned obsolescence or at least a poor
> choice in their used caps
> and cheap - used Nvidia NVS 440 cards.
>
> During evaluation of Win 7/8 I noticed there was an 8 gpu OS limit that I
> didn't know of before.
> I also ran into that limt using the proprietary nvidia driver on Linux.
>
> So now I'm trying to see how far nouveau is in regards to "multiple" gpu's
> and
> after 3 evenigs of fiddling with mostly xorg.conf I just got the first 4
> gpu's / 8 displays working.
>
> I'm stuck on the 3rd card / gpu 5+6 / monitors 9-12.
>
> Without spending another few evenings I thought I might check in with you
> guys first whether
> you think it's possible driving a 6400x4096 video wall with nouveau
> and 5 Nvidia NVS 440 cards (NV43) (10 gpus with dual head) - if not I might
> be willing to donate
> the cards for development if someone is interested.

Admittedly I've never tried this, but I can't think of anything that
would prevent you from doing this using the ZaphodHeads/Xinerama
approach. Take a look at
http://nouveau.freedesktop.org/wiki/MultiMonitorDesktop/ -- pay
special attention to the highly-unintuitive Screen setting inside of
the Device section -- it appears to be the index of the crtc to be
used on that device, not the overall screen number (so it just repeats
0/1/0/1/etc). Note that ZaphodHeads was broken for some number of
revisions of xf86-video-nouveau, but it should be all better now - if
you're getting crashes, try upgrading to the latest.

Perhaps you can share your non-working configuration and Xorg log?

Further, there should _definitely_ not be any issues running each
GPU's in a separate X screen and then using some sort of fanciness to
link it all together (e.g. dmx at which point it can all be on
separate machines).

  -ilia