[Nouveau] videowall

[Dave Airlie]

On Fri, Jan 31, 2014 at 7:24 AM, Ilia Mirkin <imirkin at alum.mit.edu> wrote:
> 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.

You'll probably run out of PCI address space with too many cards,

Dave.