media: vb2: add init_buffer buffer op

We need to initialize the request_fd field in struct vb2_v4l2_buffer
to -1 instead of the default of 0. So we need to add a new op that
is called when struct vb2_v4l2_buffer is allocated.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Reviewed-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>

drivers/media/common/videobuf2/videobuf2-core.c

@@ -356,6 +356,8 @@ static int __vb2_queue_alloc(struct vb2_queue *q, enum vb2_memory memory,
 			vb->planes[plane].length = plane_sizes[plane];
 			vb->planes[plane].min_length = plane_sizes[plane];
 		}
+		call_void_bufop(q, init_buffer, vb);
+
 		q->bufs[vb->index] = vb;
 
 		/* Allocate video buffer memory for the MMAP type */