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-rw-r--r--include/linux/dma-mapping.h6
1 files changed, 6 insertions, 0 deletions
diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
index fd4aee29ad10..b9aa2b97aab5 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,