Specifications

This is the Title of the Book, eMatter Edition

462

Chapter 15: Memory Mapping and DMA

dma_addr_t dma_map_single(struct device *dev, void *buffer, size_t size, enum

dma_data_direction direction);

void dma_unmap_single(struct device *dev, dma_addr_t bus_addr, size_t size,

enum dma_data_direction direction);

Create and destroy a single-use, streaming DMA mapping.

void dma_sync_single_for_cpu(struct device *dev, dma_handle_t bus_addr, size_t

size, enum dma_data_direction direction);

void dma_sync_single_for_device(struct device *dev, dma_handle_t bus_addr,

size_t size, enum dma_data_direction direction);

Synchronizes a buffer that has a streaming mapping. These functions must be

used if the processor must access a buffer while the streaming mapping is in

place (i.e., while the device owns the buffer).

#include <asm/scatterlist.h>

struct scatterlist { /* ... */ };

dma_addr_t sg_dma_address(struct scatterlist *sg);

unsigned int sg_dma_len(struct scatterlist *sg);

The scatterlist structure describes an I/O operation that involves more than

one buffer. The macros sg_dma_address and sg_dma_len may be used to extract

bus addresses and buffer lengths to pass to the device when implementing scat-

ter/gather operations.

dma_map_sg(struct device *dev, struct scatterlist *list, int nents,

enum dma_data_direction direction);

dma_unmap_sg(struct device *dev, struct scatterlist *list, int nents, enum

dma_data_direction direction);

void dma_sync_sg_for_cpu(struct device *dev, struct scatterlist *sg, int

nents, enum dma_data_direction direction);

void dma_sync_sg_for_device(struct device *dev, struct scatterlist *sg, int

nents, enum dma_data_direction direction);

dma_map_sg maps a scatter/gather operation, and dma_unmap_sg undoes

that mapping. If the buffers must be accessed while the mapping is active,

dma_sync_sg_* may be used to synchronize things.

/proc/dma

File that contains a textual snapshot of the allocated channels in the DMA con-

trollers. PCI-based DMA is not shown because each board works indepen-

dently, without the need to allocate a channel in the DMA controller.

#include <asm/dma.h>

Header that defines or prototypes all the functions and macros related to DMA.

It must be included to use any of the following symbols.

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