1 files changed, 10 insertions, 3 deletions

diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
index fd4aee29ad10..0c3eab1e39ac 100644
--- a/include/linux/dma-mapping.h
+++ b/include/linux/dma-mapping.h
@@ -8,6 +8,12 @@
 #include <linux/dma-direction.h>
 #include <linux/scatterlist.h>
 
+/*
+ * A dma_addr_t can hold any valid DMA or bus address for the platform.
+ * It can be given to a device to use as a DMA source or target.  A CPU cannot
+ * reference a dma_addr_t directly because there may be translation between
+ * its physical address space and the bus address space.
+ */
 struct dma_map_ops {
         void* (*alloc)(struct device *dev, size_t size,
                                 dma_addr_t *dma_handle, gfp_t gfp,
@@ -186,7 +192,7 @@ static inline int dma_get_cache_alignment(void)
 
 #ifndef ARCH_HAS_DMA_DECLARE_COHERENT_MEMORY
 static inline int
-dma_declare_coherent_memory(struct device *dev, dma_addr_t bus_addr,
+dma_declare_coherent_memory(struct device *dev, phys_addr_t phys_addr,
                             dma_addr_t device_addr, size_t size, int flags)
 {
         return 0;
@@ -217,13 +223,14 @@ extern void *dmam_alloc_noncoherent(struct device *dev, size_t size,
 extern void dmam_free_noncoherent(struct device *dev, size_t size, void *vaddr,
                                   dma_addr_t dma_handle);
 #ifdef ARCH_HAS_DMA_DECLARE_COHERENT_MEMORY
-extern int dmam_declare_coherent_memory(struct device *dev, dma_addr_t bus_addr,
+extern int dmam_declare_coherent_memory(struct device *dev,
+                                        phys_addr_t phys_addr,
                                         dma_addr_t device_addr, size_t size,
                                         int flags);
 extern void dmam_release_declared_memory(struct device *dev);
 #else /* ARCH_HAS_DMA_DECLARE_COHERENT_MEMORY */
 static inline int dmam_declare_coherent_memory(struct device *dev,
-                                dma_addr_t bus_addr, dma_addr_t device_addr,
+                                phys_addr_t phys_addr, dma_addr_t device_addr,
                                 size_t size, gfp_t gfp)
 {
         return 0;