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Commit 82f66fbe authored by Jens Axboe's avatar Jens Axboe
Browse files

[SG] Add helpers for manipulating SG entries 



We can then transition drivers without changing the generated code.

Signed-off-by: default avatarJens Axboe <jens.axboe@oracle.com>
parent 55b70a03

include/linux/scatterlist.h

+104 −8
Original line number Diff line number Diff line
@@ -2,22 +2,35 @@ 
#define _LINUX_SCATTERLIST_H



#include <asm/scatterlist.h>

#include <asm/io.h>

#include <linux/mm.h>

#include <linux/string.h>



static inline void sg_set_buf(struct scatterlist *sg, const void *buf,

			      unsigned int buflen)

/**

 * 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 = virt_to_page(buf);

	sg->offset = offset_in_page(buf);

	sg->length = buflen;

	sg->page = page;

}



static inline void sg_init_one(struct scatterlist *sg, const void *buf,

#define sg_page(sg)	((sg)->page)



static inline void sg_set_buf(struct scatterlist *sg, const void *buf,

			      unsigned int buflen)

{

	memset(sg, 0, sizeof(*sg));

	sg_set_buf(sg, buf, buflen);

	sg_set_page(sg, virt_to_page(buf));

	sg->offset = offset_in_page(buf);

	sg->length = buflen;

}



/*
@@ -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 */