2 files changed, 9 insertions, 0 deletions

diff --git a/include/asm-generic/dma-mapping-common.h b/include/asm-generic/dma-mapping-common.h
index 3378dcf4c31e..940d5ec122c9 100644
--- a/include/asm-generic/dma-mapping-common.h
+++ b/include/asm-generic/dma-mapping-common.h
@@ -39,6 +39,10 @@ static inline void dma_unmap_single_attrs(struct device *dev, dma_addr_t addr,
         debug_dma_unmap_page(dev, addr, size, dir, true);
 }
 
+/*
+ * dma_maps_sg_attrs returns 0 on error and > 0 on success.
+ * It should never return a value < 0.
+ */
 static inline int dma_map_sg_attrs(struct device *dev, struct scatterlist *sg,
                                    int nents, enum dma_data_direction dir,
                                    struct dma_attrs *attrs)
@@ -51,6 +55,7 @@ static inline int dma_map_sg_attrs(struct device *dev, struct scatterlist *sg,
                 kmemcheck_mark_initialized(sg_virt(s), s->length);
         BUG_ON(!valid_dma_direction(dir));
         ents = ops->map_sg(dev, sg, nents, dir, attrs);
+        BUG_ON(ents < 0);
         debug_dma_map_sg(dev, sg, nents, ents, dir);
 
         return ents;
diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
index c3007cb4bfa6..ac07ff090919 100644
--- a/include/linux/dma-mapping.h
+++ b/include/linux/dma-mapping.h
@@ -34,6 +34,10 @@ struct dma_map_ops {
         void (*unmap_page)(struct device *dev, dma_addr_t dma_handle,
                            size_t size, enum dma_data_direction dir,
                            struct dma_attrs *attrs);
+        /*
+         * map_sg returns 0 on error and a value > 0 on success.
+         * It should never return a value < 0.
+         */
         int (*map_sg)(struct device *dev, struct scatterlist *sg,
                       int nents, enum dma_data_direction dir,
                       struct dma_attrs *attrs);