EXA support for nv driver

[Lars Knoll]

Hi,

I've hacked the nvidia driver lately to add EXA support to it, and at the same 
time cleaned up some (but far from all) of the number magic in nv_hw.c. I 
also added some documentation on how to initialize the HW to be able to do 
DMA (at least as far as I understood it ;-)

I implemented the uploadToScreen/downloadFromScreen hooks, but they require 
access to the AGP file descriptor (so that the driver can allocate mmap the 
GART). Currently the AGP code in Xorg doesn't export this, so I had to add a 
small hook there as well.

The upload/download hooks are working for me on a GeForce 6600, but I had 
reports that they don't work on some other hardware. I hope to be able to get 
my hands on some older hardware soon, so I can test myself.

There is a preliminary implementation for the composite hook available, but 
the implementation is wrong, because the blending operation seems to expect 
non premultiplied pixmaps. I have an idea how to do it properly and will 
probably work on that as my time permits.

You can find the patches at: 

http://trolls.troll.no/lars/patches/nv.diff
http://trolls.troll.no/lars/patches/lnx_agp.diff


Related to this, I think we should change the signature of 
    Bool        (*UploadToScreen) (PixmapPtr            pDst,
                                   char                 *src,
                                   int                  src_pitch);
in ExaAccelInfoRec to
    Bool        (*UploadToScreen) (PixmapPtr            pDst,
                                   int x, int y, int w, int h,
                                   char                 *src,
                                   int                  src_pitch);

to match the DownloadFromScreen pointer, and allow us to use UploadToScreen to 
accelerate PutImage. Any opinions?

Lars