media: v4l2-mem2mem: Document that v4l2_m2m_get_vq() never returns NULL

The v4l2_m2m_get_vq() never returns a NULL pointer, as the internal
get_queue_ctx() helper always returns a non-NULL pointer. Many drivers
check the return value against NULL, due to a combination of old code
and cargo-cult programming. Even v4l2-mem2mem.c contains unneeded NULL
checks.

Clarify the API by documenting explicitly that a NULL check is not
needed, and simplify the code by removing the unneeded NULL checks from
v4l2-mem2mem.c.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Stefan Klug <stefan.klug@ideasonboard.com>
Signed-off-by: Hans Verkuil <hverkuil+cisco@kernel.org>

1 files changed, 3 insertions, 0 deletions

diff --git a/include/media/v4l2-mem2mem.h b/include/media/v4l2-mem2mem.h
index 500f81f399df..c82445929c68 100644
--- a/include/media/v4l2-mem2mem.h
+++ b/include/media/v4l2-mem2mem.h
@@ -153,6 +153,9 @@ void *v4l2_m2m_get_curr_priv(struct v4l2_m2m_dev *m2m_dev);
  *
  * @m2m_ctx: m2m context assigned to the instance given by struct &v4l2_m2m_ctx
  * @type: type of the V4L2 buffer, as defined by enum &v4l2_buf_type
+ *
+ * This function returns the capture queue when @type is a capture type, and the
+ * output queue otherwise. It never returns a NULL pointer.
  */
 struct vb2_queue *v4l2_m2m_get_vq(struct v4l2_m2m_ctx *m2m_ctx,
 				       enum v4l2_buf_type type);