TTM and AGP conflicts

[James Simmons]

> >> Attached is patch to fix this, so sorry about that, i must have lost my
> >> agp change along the way when working on the patchset. This patch is not
> >> extensively tested, i will do more testing tomorrow on more gpu, might
> >> even found an nvidia agp i can try. Again sorry for breaking this.
> >
> > Thanks for the fix up. I was wondering if this purposed change could be
> > done instead. Its the same as your fix up except that you pass in the
> > ttm_buffer_object for tt_create. The reason is I really like to have the
> > ability to have more than one back end to grab a bunch pf pages from.
> > Currently its AGP or something else. On some of my embedded devices the
> > AGP space is not very large and can be exhausted very quickly. Those
> > embedded devices have DMA engines I could use instead.
> 
> This change violate the layer separation ttm wish to preserve see :
> http://www.mail-archive.com/dri-devel@lists.freedesktop.org/msg16443.html
> 
> You can achieve what you want by either adding a new domain so you would have
> system, vram, agp, pcidma and object can be bound to one and only one. Or you
> can hack your own agp ttm backend that could bind bo to agp or pci or
> both at the same time depending on what you want to achieve.

The question is how does one know which domain you want in tt_create. 
Currenty drivers are using there dev_priv but if you have have more than 
one option available how does one choose? Would you be okay with passing 
in a domain flag?