diff --git a/drivers/dma-buf/dma-buf-io.c b/drivers/dma-buf/dma-buf-io.c
index e432194a5dfc..8440151de860 100644
--- a/drivers/dma-buf/dma-buf-io.c
+++ b/drivers/dma-buf/dma-buf-io.c
@@ -43,6 +43,18 @@ static void dma_buf_io_kill_map(struct dma_buf_io_ctx *ctx)
 	dma_buf_io_map_release(map);
 }
 
+/**
+ * dma_buf_io_init_map - Initialise the map.
+ * @ctx:	[in]	dma-buf I/O context the map is created for
+ * @map:	[in]	dma-buf I/O map
+ * @sgt:	[in]	the backing scatter-gather table
+ *
+ * Importer's helper that initialises @map for the provided I/O context
+ * and scatter-gather table. The importer should call it once for each map
+ * on creation.
+ *
+ * Return: 0 on success, or a negative errno code otherwise.
+ */
 int dma_buf_io_init_map(struct dma_buf_io_ctx *ctx, struct dma_buf_io_map *map,
 			struct sg_table *sgt)
 {