Introduced two function glamor_get_sub_pixmap/glamor_put_sub_pixmap,
can easily used to get and put sub region of a big textured pixmap.
And it can use pbo if possible.
To support download a big textured pixmap's sub region to another
pixmap's pbo, we introduce a new type of pixmap GLAMOR_MEMORY_MAP.
This type of pixmap has a valid devPrivate.ptr pointer, and that
pointer points to a pbo mapped address.
Now, we are ready to refine those
glamor_prepare_access/glamor_finish_access pairs.
Signed-off-by: Zhigang Gong <zhigang.gong@linux.intel.com>
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