EXA for radeon experimental patch

[Benjamin Herrenschmidt]

On Thu, 2005-09-01 at 11:44 +0100, Alan Cox wrote:
> On Iau, 2005-09-01 at 09:16 +0200, Lars Knoll wrote:
> > What about writes from GPU to PCI? Maybe these exist.
> 
> Quite a few cards can do this. It is one reason things like VIA drivers
> have command filters for DRI - to stop people blitting patches into the
> kernel memory.
> 
> In addition almost any AGP card can copy from video memory to AGP. You
> then pull the pages out of the GART (fast), cache them (fast), use them
> (fast), flush them to ram (not too slow), and put them uncached back
> into the GART.

Yup, except that quite a bit of AGP chipsets don't support writes from
the card to AGP memory :(

It would be useful to have the AGP backend to expose that info

Ben.