scatterlist.h

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#ifndef __ASM_GENERIC_SCATTERLIST_H
#define __ASM_GENERIC_SCATTERLIST_H

#include <linux/types.h>

struct scatterlist {
#ifdef CONFIG_DEBUG_SG
    unsigned long   sg_magic;
#endif
    unsigned long   page_link;
    unsigned int    offset;
    unsigned int    length;
    dma_addr_t  dma_address;
#ifdef CONFIG_NEED_SG_DMA_LENGTH
    unsigned int    dma_length;
#endif
};

/*
 * These macros should be used after a dma_map_sg call has been done
 * to get bus addresses of each of the SG entries and their lengths.
 * You should only work with the number of sg entries pci_map_sg
 * returns, or alternatively stop on the first sg_dma_len(sg) which
 * is 0.
 */
#define sg_dma_address(sg)  ((sg)->dma_address)

#ifdef CONFIG_NEED_SG_DMA_LENGTH
#define sg_dma_len(sg)      ((sg)->dma_length)
#else
#define sg_dma_len(sg)      ((sg)->length)
#endif

#endif /* __ASM_GENERIC_SCATTERLIST_H */