From: Andrzej Pietrasiewicz
Add an implementation of DMA scatter/gather allocator and handling
routines for videobuf2.
For mmap operation mode it is implemented on top of
alloc_page + sg_set_page/_free_page.
For userptr operation mode it is impelmented on top of
get_user_pages + sg_set_page/put
From: Andrzej Pietrasiewicz
Add an implementation of DMA scatter/gather allocator and handling
routines for videobuf2.
For mmap operation mode it is implemented on top of
alloc_page + sg_set_page/_free_page.
For userptr operation mode it is impelmented on top of
get_user_pages + sg_set_page/put
