Well feel free to provide patches. The relevant source is in src/gallium/drivers/radeon/radeon_uvd.c. Probably all the 32 and 16 bit fields set into the message and feedback buffer in get_h264_msg(), get_h265_msg(), get_vc1_msg(), get_mpeg2_msg(), get_mpeg4_msg() and ruvd_end_frame() needs to be byte swapped. It should actually be pretty trivial to do so, it's just a huge bunch of work nobody so far has time to work on.