media: imx: Stop direct calls to queue num_buffers field

Use vb2_get_num_buffers() to avoid using queue num_buffers field directly.
This allows us to change how the number of buffers is computed in the
future.
Signed-off-by: Benjamin Gaignard <benjamin.gaignard@collabora.com>
Reviewed-by: Andrzej Pietrasiewicz <andrzej.p@collabora.com>
CC: Steve Longerbeam <slongerbeam@gmail.com>
CC: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>

drivers/staging/media/imx/imx-media-capture.c

@@ -605,6 +605,7 @@ static int capture_queue_setup(struct vb2_queue *vq,
 {
 	struct capture_priv *priv = vb2_get_drv_priv(vq);
 	struct v4l2_pix_format *pix = &priv->vdev.fmt;
+	unsigned int q_num_bufs = vb2_get_num_buffers(vq);
 	unsigned int count = *nbuffers;
 
 	if (vq->type != V4L2_BUF_TYPE_VIDEO_CAPTURE)
@@ -613,14 +614,14 @@ static int capture_queue_setup(struct vb2_queue *vq,
 	if (*nplanes) {
 		if (*nplanes != 1 || sizes[0] < pix->sizeimage)
 			return -EINVAL;
-		count += vq->num_buffers;
+		count += q_num_bufs;
 	}
 
 	count = min_t(__u32, VID_MEM_LIMIT / pix->sizeimage, count);
 
 	if (*nplanes)
-		*nbuffers = (count < vq->num_buffers) ? 0 :
-			count - vq->num_buffers;
+		*nbuffers = (count < q_num_bufs) ? 0 :
+			count - q_num_bufs;
 	else
 		*nbuffers = count;