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 */

include/media/videobuf2-core.h

@@ -412,6 +412,9 @@ struct vb2_ops {
  * @verify_planes_array: Verify that a given user space structure contains
  *			enough planes for the buffer. This is called
  *			for each dequeued buffer.
+ * @init_buffer:	given a &vb2_buffer initialize the extra data after
+ *			struct vb2_buffer.
+ *			For V4L2 this is a &struct vb2_v4l2_buffer.
  * @fill_user_buffer:	given a &vb2_buffer fill in the userspace structure.
  *			For V4L2 this is a &struct v4l2_buffer.
  * @fill_vb2_buffer:	given a userspace structure, fill in the &vb2_buffer.
@@ -422,6 +425,7 @@ struct vb2_ops {
  */
 struct vb2_buf_ops {
 	int (*verify_planes_array)(struct vb2_buffer *vb, const void *pb);
+	void (*init_buffer)(struct vb2_buffer *vb);
 	void (*fill_user_buffer)(struct vb2_buffer *vb, void *pb);
 	int (*fill_vb2_buffer)(struct vb2_buffer *vb, struct vb2_plane *planes);
 	void (*copy_timestamp)(struct vb2_buffer *vb, const void *pb);