media: videobuf2-v4l2.c: add vb2_queue_change_type() helper

On some platforms a video device can capture either video data or
metadata. The driver can implement vidioc functions for both video and
metadata, and use a single vb2_queue for the buffers. However, vb2_queue
requires choosing a single buffer type, which conflicts with the idea of
capturing either video or metadata.

The buffer type of vb2_queue can be changed, but it's not obvious how
this should be done in the drivers. To help this, add a new helper
function vb2_queue_change_type() which ensures the correct checks and
documents how it can be used.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

1 files changed, 14 insertions, 0 deletions

diff --git a/drivers/media/common/videobuf2/videobuf2-v4l2.c b/drivers/media/common/videobuf2/videobuf2-v4l2.c
index 7e96f67c60ba..2988bb38ceb1 100644
--- a/drivers/media/common/videobuf2/videobuf2-v4l2.c
+++ b/drivers/media/common/videobuf2/videobuf2-v4l2.c
@@ -939,6 +939,20 @@ void vb2_queue_release(struct vb2_queue *q)
 }
 EXPORT_SYMBOL_GPL(vb2_queue_release);
 
+int vb2_queue_change_type(struct vb2_queue *q, unsigned int type)
+{
+	if (type == q->type)
+		return 0;
+
+	if (vb2_is_busy(q))
+		return -EBUSY;
+
+	q->type = type;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(vb2_queue_change_type);
+
 __poll_t vb2_poll(struct vb2_queue *q, struct file *file, poll_table *wait)
 {
 	struct video_device *vfd = video_devdata(file);