[media] v4l: vb2: add buffer exporting via dmabuf

This patch adds extension to videobuf2-core. It allow to export an mmap buffer
as a DMABUF file descriptor.

Signed-off-by: Tomasz Stanislawski <t.stanislaws@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Hans Verkuil <hans.verkuil@cisco.com>
Tested-by: Mauro Carvalho Chehab <mchehab@redhat.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
diff --git a/drivers/media/v4l2-core/v4l2-mem2mem.c b/drivers/media/v4l2-core/v4l2-mem2mem.c
index 017fed8..438ea45 100644
--- a/drivers/media/v4l2-core/v4l2-mem2mem.c
+++ b/drivers/media/v4l2-core/v4l2-mem2mem.c
@@ -369,6 +369,19 @@
 EXPORT_SYMBOL_GPL(v4l2_m2m_dqbuf);
 
 /**
+ * v4l2_m2m_expbuf() - export a source or destination buffer, depending on
+ * the type
+ */
+int v4l2_m2m_expbuf(struct file *file, struct v4l2_m2m_ctx *m2m_ctx,
+		  struct v4l2_exportbuffer *eb)
+{
+	struct vb2_queue *vq;
+
+	vq = v4l2_m2m_get_vq(m2m_ctx, eb->type);
+	return vb2_expbuf(vq, eb);
+}
+EXPORT_SYMBOL_GPL(v4l2_m2m_expbuf);
+/**
  * v4l2_m2m_streamon() - turn on streaming for a video queue
  */
 int v4l2_m2m_streamon(struct file *file, struct v4l2_m2m_ctx *m2m_ctx,