media: pci: tw68: 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>
CC: Fabrizio Castro <fabrizio.castro.jz@renesas.com>
Reviewed-by: Andrzej Pietrasiewicz <andrzej.p@collabora.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>

drivers/media/pci/tw68/tw68-video.c

@@ -360,13 +360,14 @@ static int tw68_queue_setup(struct vb2_queue *q,
 			   unsigned int sizes[], struct device *alloc_devs[])
 {
 	struct tw68_dev *dev = vb2_get_drv_priv(q);
-	unsigned tot_bufs = q->num_buffers + *num_buffers;
+	unsigned int q_num_bufs = vb2_get_num_buffers(q);
+	unsigned int tot_bufs = q_num_bufs + *num_buffers;
 	unsigned size = (dev->fmt->depth * dev->width * dev->height) >> 3;
 
 	if (tot_bufs < 2)
 		tot_bufs = 2;
 	tot_bufs = tw68_buffer_count(size, tot_bufs);
-	*num_buffers = tot_bufs - q->num_buffers;
+	*num_buffers = tot_bufs - q_num_bufs;
 	/*
 	 * We allow create_bufs, but only if the sizeimage is >= as the
 	 * current sizeimage. The tw68_buffer_count calculation becomes quite