[media] media/videobuf2-dma-contig: Save output from dma_map_sg

dma_map_sg returns the number of areas mapped by the hardware,
which could be different than the areas given as an input.
The output must be saved to nent.

Signed-off-by: Ricardo Ribalda Delgado <ricardo.ribalda@gmail.com>
Reviewed-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>

drivers/media/v4l2-core/videobuf2-dma-contig.c

@@ -299,7 +299,6 @@ static struct sg_table *vb2_dc_dmabuf_ops_map(
 	/* stealing dmabuf mutex to serialize map/unmap operations */
 	struct mutex *lock = &db_attach->dmabuf->lock;
 	struct sg_table *sgt;
-	int ret;
 
 	mutex_lock(lock);
 
@@ -318,8 +317,9 @@ static struct sg_table *vb2_dc_dmabuf_ops_map(
 	}
 
 	/* mapping to the client with new direction */
-	ret = dma_map_sg(db_attach->dev, sgt->sgl, sgt->orig_nents, dma_dir);
-	if (ret <= 0) {
+	sgt->nents = dma_map_sg(db_attach->dev, sgt->sgl, sgt->orig_nents,
+				dma_dir);
+	if (!sgt->nents) {
 		pr_err("failed to map scatterlist\n");
 		mutex_unlock(lock);
 		return ERR_PTR(-EIO);