[PATCH] dma-debug: add comment for failed to check map error

[Miles Chen]

Add comment for failed to check map error to help driver
developers.

Signed-off-by: Miles Chen <miles.c...@mediatek.com>
---
 lib/dma-debug.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/lib/dma-debug.c b/lib/dma-debug.c
index 8971370..60c57ec 100644
--- a/lib/dma-debug.c
+++ b/lib/dma-debug.c
@@ -1155,6 +1155,11 @@ static void check_unmap(struct dma_debug_entry *ref)
                           dir2name[ref->direction]);
        }
 
+       /*
+        * Drivers should use dma_mapping_error() to check the returned
+        * addresses of dma_map_single() and dma_map_page().
+        * If not, print this warning message. See Documentation/DMA-API.txt.
+        */
        if (entry->map_err_type == MAP_ERR_NOT_CHECKED) {
                err_printk(ref->dev, entry,
                           "DMA-API: device driver failed to check map error"
-- 
1.9.1