BO are referenced once by reloc to make sure that they not destroyed
before we get a chance to flush the cmd stream, so we need to unreference
them once in cs submit or cs erase if cs i never submitted so bo can
be destructed.
Relocation now consist of the following informations (in this order) :
handle buffer object handle identifier
start_offset start offset of first data of the buffer object used by the cs
end_offset end offset of last data of the buffer object used by the cs
read_domain read domain (either VRAM, or GTT as GPU is invalid for CS)
write_domain write domain (either VRAM, or GTT as GPU is invalid for CS)
flags flags used for further optimization (like discard previous
buffer content or forget buffer content after cs which can
help in avoiding moving content in or out)
Dave Airlie
Jesse Barnes
Jerome Glisse