media: vb2: add requires_requests bit for stateless codecs

Stateless codecs require the use of the Request API as opposed of it
being optional.

So add a bit to indicate this and let vb2 check for this.

If an attempt is made to queue a buffer without an associated request,
then the EBADR error is returned to userspace.

Doing this check in the vb2 core simplifies drivers, since they
don't have to check for this, they can just set this flag.
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Reviewed-by: Paul Kocialkowski <paul.kocialkowski@bootlin.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>

Documentation/media/uapi/v4l/vidioc-qbuf.rst

@@ -189,6 +189,10 @@ EACCES
     The ``V4L2_BUF_FLAG_REQUEST_FD`` flag was set but the device does not
     support requests for the given buffer type.
 
+EBADR
+    The ``V4L2_BUF_FLAG_REQUEST_FD`` flag was not set but the device requires
+    that the buffer is part of a request.
+
 EBUSY
     The first buffer was queued via a request, but the application now tries
     to queue it directly, or vice versa (it is not permitted to mix the two

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

@@ -1507,6 +1507,12 @@ int vb2_core_qbuf(struct vb2_queue *q, unsigned int index, void *pb,
 
 	vb = q->bufs[index];
 
+	if (!req && vb->state != VB2_BUF_STATE_IN_REQUEST &&
+	    q->requires_requests) {
+		dprintk(1, "qbuf requires a request\n");
+		return -EBADR;
+	}
+
 	if ((req && q->uses_qbuf) ||
 	    (!req && vb->state != VB2_BUF_STATE_IN_REQUEST &&
 	     q->uses_requests)) {
@@ -2238,6 +2244,9 @@ int vb2_core_queue_init(struct vb2_queue *q)
 	    WARN_ON(!q->ops->buf_queue))
 		return -EINVAL;
 
+	if (WARN_ON(q->requires_requests && !q->supports_requests))
+		return -EINVAL;
+
 	INIT_LIST_HEAD(&q->queued_list);
 	INIT_LIST_HEAD(&q->done_list);
 	spin_lock_init(&q->done_lock);

drivers/media/common/videobuf2/videobuf2-v4l2.c

@@ -381,6 +381,10 @@ static int vb2_queue_or_prepare_buf(struct vb2_queue *q, struct media_device *md
 		return 0;
 
 	if (!(b->flags & V4L2_BUF_FLAG_REQUEST_FD)) {
+		if (q->requires_requests) {
+			dprintk(1, "%s: queue requires requests\n", opname);
+			return -EBADR;
+		}
 		if (q->uses_requests) {
 			dprintk(1, "%s: queue uses requests\n", opname);
 			return -EBUSY;

include/media/videobuf2-core.h

@@ -482,6 +482,8 @@ struct vb2_buf_ops {
  *              has not been called. This is a vb1 idiom that has been adopted
  *              also by vb2.
  * @supports_requests: this queue supports the Request API.
+ * @requires_requests: this queue requires the Request API. If this is set to 1,
+ *		then supports_requests must be set to 1 as well.
  * @uses_qbuf:	qbuf was used directly for this queue. Set to 1 the first
  *		time this is called. Set to 0 when the queue is canceled.
  *		If this is 1, then you cannot queue buffers from a request.
@@ -556,6 +558,7 @@ struct vb2_queue {
 	unsigned			allow_zero_bytesused:1;
 	unsigned		   quirk_poll_must_check_waiting_for_buffers:1;
 	unsigned			supports_requests:1;
+	unsigned			requires_requests:1;
 	unsigned			uses_qbuf:1;
 	unsigned			uses_requests:1;