media: vb2: skip request checks for VIDIOC_PREPARE_BUF

VIDIOC_PREPARE_BUF should ignore V4L2_BUF_FLAG_REQUEST_FD since it isn't
doing anything with requests. So inform vb2_queue_or_prepare_buf whether
it is called from vb2_prepare_buf or vb2_qbuf and just return 0 in the
first case.

This was found when adding new v4l2-compliance checks.
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Acked-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>

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

@@ -333,10 +333,10 @@ static int vb2_fill_vb2_v4l2_buffer(struct vb2_buffer *vb, struct v4l2_buffer *b
 }
 
 static int vb2_queue_or_prepare_buf(struct vb2_queue *q, struct media_device *mdev,
-				    struct v4l2_buffer *b,
-				    const char *opname,
+				    struct v4l2_buffer *b, bool is_prepare,
 				    struct media_request **p_req)
 {
+	const char *opname = is_prepare ? "prepare_buf" : "qbuf";
 	struct media_request *req;
 	struct vb2_v4l2_buffer *vbuf;
 	struct vb2_buffer *vb;
@@ -378,6 +378,9 @@ static int vb2_queue_or_prepare_buf(struct vb2_queue *q, struct media_device *md
 			return ret;
 	}
 
+	if (is_prepare)
+		return 0;
+
 	if (!(b->flags & V4L2_BUF_FLAG_REQUEST_FD)) {
 		if (q->uses_requests) {
 			dprintk(1, "%s: queue uses requests\n", opname);
@@ -657,7 +660,7 @@ int vb2_prepare_buf(struct vb2_queue *q, struct media_device *mdev,
 	if (b->flags & V4L2_BUF_FLAG_REQUEST_FD)
 		return -EINVAL;
 
-	ret = vb2_queue_or_prepare_buf(q, mdev, b, "prepare_buf", NULL);
+	ret = vb2_queue_or_prepare_buf(q, mdev, b, true, NULL);
 
 	return ret ? ret : vb2_core_prepare_buf(q, b->index, b);
 }
@@ -729,7 +732,7 @@ int vb2_qbuf(struct vb2_queue *q, struct media_device *mdev,
 		return -EBUSY;
 	}
 
-	ret = vb2_queue_or_prepare_buf(q, mdev, b, "qbuf", &req);
+	ret = vb2_queue_or_prepare_buf(q, mdev, b, false, &req);
 	if (ret)
 		return ret;
 	ret = vb2_core_qbuf(q, b->index, b, req);