diff --git a/drivers/media/common/videobuf2/videobuf2-core.c b/drivers/media/common/videobuf2/videobuf2-core.c
index cfccee87909a..4489744fbbd9 100644
--- a/drivers/media/common/videobuf2/videobuf2-core.c
+++ b/drivers/media/common/videobuf2/videobuf2-core.c
@@ -205,6 +205,7 @@ static int __vb2_buf_mem_alloc(struct vb2_buffer *vb)
 	 * NOTE: mmapped areas should be page aligned
 	 */
 	for (plane = 0; plane < vb->num_planes; ++plane) {
+		/* Memops alloc requires size to be page aligned. */
 		unsigned long size = PAGE_ALIGN(vb->planes[plane].length);
 
 		/* Did it wrap around? */
diff --git a/include/media/videobuf2-core.h b/include/media/videobuf2-core.h
index 22f3ff76a8b5..c03ef7cc5071 100644
--- a/include/media/videobuf2-core.h
+++ b/include/media/videobuf2-core.h
@@ -54,7 +54,8 @@ struct vb2_threadio_data;
  *		will then be passed as @buf_priv argument to other ops in this
  *		structure. Additional gfp_flags to use when allocating the
  *		are also passed to this operation. These flags are from the
- *		gfp_flags field of vb2_queue.
+ *		gfp_flags field of vb2_queue. The size argument to this function
+ *		shall be *page aligned*.
  * @put:	inform the allocator that the buffer will no longer be used;
  *		usually will result in the allocator freeing the buffer (if
  *		no other users of this buffer are present); the @buf_priv