Commit eba304c6 authored by Christoph Hellwig's avatar Christoph Hellwig
Browse files

dma-mapping: better document dma_addr_t and DMA_MAPPING_ERROR 



Move the comment documenting dma_addr_t away from the dma_map_ops
definition which isn't very related to it, and toward DMA_MAPPING_ERROR,
which is somewhat related.  Add a little blurb about DMA_MAPPING_ERROR
as well.

Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
parent db4268f8

include/linux/dma-mapping.h

+10 −6
Original line number Diff line number Diff line
@@ -67,12 +67,6 @@ 
 */

#define DMA_ATTR_PRIVILEGED		(1UL << 9)



/*

 * 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,
@@ -131,6 +125,16 @@ struct dma_map_ops { 
	unsigned long (*get_merge_boundary)(struct device *dev);

};



/*

 * 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.  It is specific to a

 * given device and there may be a translation between the CPU physical address

 * space and the bus address space.

 *

 * DMA_MAPPING_ERROR is the magic error code if a mapping failed.  It should not

 * be used directly in drivers, but checked for using dma_mapping_error()

 * instead.

 */

#define DMA_MAPPING_ERROR		(~(dma_addr_t)0)



extern const struct dma_map_ops dma_virt_ops;