[Xorg-driver-geode] [PATCH-explain] Allocate video memory with exaOffscreenAlloc

[Cui, Hunk]

Hi, all,
	About video memory allocation issue, it have used
exaOffscreenAlloc replacement GeodeAllocOffscreen, this is the way to
make unity. In our geode driver, rotate shadow buffer and video overlay
buffer have to be allocated in offscreen memory range, it can manage the
buffer region more convenience, we should use exaOffscreenAlloc once
again, and give all the free video memory to EXA for handling, instead
of reserving it for video overlay. This way EXA has more memory
available for offscreen pixmaps while the user is not in rotated mode,
or isn't using video overlay (XVideo extension using video players).
Then when shadow buffer or video overlay is necessary, we should be able
to simply request for it on-demand with exaOffscreenAlloc. It will evict
offscreen pixmaps as necessary to make room for our consecutive video
memory needs and give us that video memory we need.

	This issue was tested in all cases, (e g: change the Graphic
memory in BIOS, long time
to playback the video file, this Patch has supported x-server
1.6/1.7/1.8/1.9, running on ubuntu 10.04 and Fedora 12 platform etc), it
can normally working.
	
	Any feedback, please let me know.

Thanks,
Hunk Cui