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linux-sg2042
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[SG] Add helpers for manipulating SG entries 

We can then transition drivers without changing the generated code.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
This commit is contained in:
Jens Axboe 2007-10-22 17:07:37 +02:00
parent 55b70a0300
commit 82f66fbef5
1 changed files with 104 additions and 8 deletions
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112
include/linux/scatterlist.h
View File

@ -2,24 +2,37 @@
#define _LINUX_SCATTERLIST_H
#include <asm/scatterlist.h>
#include <asm/io.h>
#include <linux/mm.h>
#include <linux/string.h>
/**
* sg_set_page - Set sg entry to point at given page
* @sg: SG entry
* @page: The page
*
* Description:
* Use this function to set an sg entry pointing at a page, never assign
* the page directly. We encode sg table information in the lower bits
* of the page pointer. See sg_page() for looking up the page belonging
* to an sg entry.
*
**/
static inline void sg_set_page(struct scatterlist *sg, struct page *page)
{
sg->page = page;
}
#define sg_page(sg) ((sg)->page)
static inline void sg_set_buf(struct scatterlist *sg, const void *buf,
unsigned int buflen)
{
sg->page = virt_to_page(buf);
sg_set_page(sg, virt_to_page(buf));
sg->offset = offset_in_page(buf);
sg->length = buflen;
}
static inline void sg_init_one(struct scatterlist *sg, const void *buf,
unsigned int buflen)
{
memset(sg, 0, sizeof(*sg));
sg_set_buf(sg, buf, buflen);
}
/*
* We overload the LSB of the page pointer to indicate whether it's
* a valid sg entry, or whether it points to the start of a new scatterlist.
@ -104,4 +117,87 @@ static inline void sg_chain(struct scatterlist *prv, unsigned int prv_nents,
prv[prv_nents - 1].page = (struct page *) ((unsigned long) sgl | 0x01);
}
/**
* sg_mark_end - Mark the end of the scatterlist
* @sgl: Scatterlist
* @nents: Number of entries in sgl
*
* Description:
* Marks the last entry as the termination point for sg_next()
*
**/
static inline void sg_mark_end(struct scatterlist *sgl, unsigned int nents)
{
}
static inline void __sg_mark_end(struct scatterlist *sg)
{
}
/**
* sg_init_one - Initialize a single entry sg list
* @sg: SG entry
* @buf: Virtual address for IO
* @buflen: IO length
*
* Notes:
* This should not be used on a single entry that is part of a larger
* table. Use sg_init_table() for that.
*
**/
static inline void sg_init_one(struct scatterlist *sg, const void *buf,
unsigned int buflen)
{
memset(sg, 0, sizeof(*sg));
sg_mark_end(sg, 1);
sg_set_buf(sg, buf, buflen);
}
/**
* sg_init_table - Initialize SG table
* @sgl: The SG table
* @nents: Number of entries in table
*
* Notes:
* If this is part of a chained sg table, sg_mark_end() should be
* used only on the last table part.
*
**/
static inline void sg_init_table(struct scatterlist *sgl, unsigned int nents)
{
memset(sgl, 0, sizeof(*sgl) * nents);
sg_mark_end(sgl, nents);
}
/**
* sg_phys - Return physical address of an sg entry
* @sg: SG entry
*
* Description:
* This calls page_to_phys() on the page in this sg entry, and adds the
* sg offset. The caller must know that it is legal to call page_to_phys()
* on the sg page.
*
**/
static inline unsigned long sg_phys(struct scatterlist *sg)
{
return page_to_phys(sg_page(sg)) + sg->offset;
}
/**
* sg_virt - Return virtual address of an sg entry
* @sg: SG entry
*
* Description:
* This calls page_address() on the page in this sg entry, and adds the
* sg offset. The caller must know that the sg page has a valid virtual
* mapping.
*
**/
static inline void *sg_virt(struct scatterlist *sg)
{
return page_address(sg_page(sg)) + sg->offset;
}
#endif /* _LINUX_SCATTERLIST_H */