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#ifndef _LINUX_SCATTERLIST_H

#define _LINUX_SCATTERLIST_H

#include 

#include 

#include 

#include 

#include 

//#include 

struct sg_table {

	struct scatterlist *sgl;	/* the list */

	unsigned int nents;		/* number of mapped entries */

	unsigned int orig_nents;	/* original size of list */

};

/*

 * Notes on SG table design.

 *

 * Architectures must provide an unsigned long page_link field in the

 * scatterlist struct. We use that to place the page pointer AND encode

 * information about the sg table as well. The two lower bits are reserved

 * for this information.

 *

 * If bit 0 is set, then the page_link contains a pointer to the next sg

 * table list. Otherwise the next entry is at sg + 1.

 *

 * If bit 1 is set, then this sg entry is the last element in a list.

 *

 * See sg_next().

 *

 */

#define SG_MAGIC	0x87654321

/*

 * 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.

 * Those low bits are there for everyone! (thanks mason :-)

 */

#define sg_is_chain(sg)		((sg)->page_link & 0x01)

#define sg_is_last(sg)		((sg)->page_link & 0x02)

#define sg_chain_ptr(sg)	\

	((struct scatterlist *) ((sg)->page_link & ~0x03))

/**

 * sg_assign_page - Assign a given page to an SG entry

 * @sg:		    SG entry

 * @page:	    The page

 *

 * Description:

 *   Assign page to sg entry. Also see sg_set_page(), the most commonly used

 *   variant.

 *

 **/

static inline void sg_assign_page(struct scatterlist *sg, struct page *page)

{

	unsigned long page_link = sg->page_link & 0x3;

	/*

	 * In order for the low bit stealing approach to work, pages

	 * must be aligned at a 32-bit boundary as a minimum.

	 */

	BUG_ON((unsigned long) page & 0x03);

#ifdef CONFIG_DEBUG_SG

	BUG_ON(sg->sg_magic != SG_MAGIC);

	BUG_ON(sg_is_chain(sg));

#endif

	sg->page_link = page_link | (unsigned long) page;

}

/**

 * sg_set_page - Set sg entry to point at given page

 * @sg:		 SG entry

 * @page:	 The page

 * @len:	 Length of data

 * @offset:	 Offset into 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,

			       unsigned int len, unsigned int offset)

{

	sg_assign_page(sg, page);

	sg->offset = offset;

	sg->length = len;

}

static inline struct page *sg_page(struct scatterlist *sg)

{

#ifdef CONFIG_DEBUG_SG

	BUG_ON(sg->sg_magic != SG_MAGIC);

	BUG_ON(sg_is_chain(sg));

#endif

	return (struct page *)((sg)->page_link & ~0x3);

}

/**

 * sg_set_buf - Set sg entry to point at given data

 * @sg:		 SG entry

 * @buf:	 Data

 * @buflen:	 Data length

 *

 **/

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

//                 unsigned int buflen)

//{

//   sg_set_page(sg, virt_to_page(buf), buflen, offset_in_page(buf));

//}

/*

 * Loop over each sg element, following the pointer to a new list if necessary

 */

#define for_each_sg(sglist, sg, nr, __i)	\

	for (__i = 0, sg = (sglist); __i < (nr); __i++, sg = sg_next(sg))

/**

 * sg_chain - Chain two sglists together

 * @prv:	First scatterlist

 * @prv_nents:	Number of entries in prv

 * @sgl:	Second scatterlist

 *

 * Description:

 *   Links @prv@ and @sgl@ together, to form a longer scatterlist.

 *

 **/

static inline void sg_chain(struct scatterlist *prv, unsigned int prv_nents,

			    struct scatterlist *sgl)

{

#ifndef ARCH_HAS_SG_CHAIN

	BUG();

#endif

	/*

	 * offset and length are unused for chain entry.  Clear them.

	 */

	prv[prv_nents - 1].offset = 0;

	prv[prv_nents - 1].length = 0;

	/*

	 * Set lowest bit to indicate a link pointer, and make sure to clear

	 * the termination bit if it happens to be set.

	 */

	prv[prv_nents - 1].page_link = ((unsigned long) sgl | 0x01) & ~0x02;

}

/**

 * sg_mark_end - Mark the end of the scatterlist

 * @sg:		 SG entryScatterlist

 *

 * Description:

 *   Marks the passed in sg entry as the termination point for the sg

 *   table. A call to sg_next() on this entry will return NULL.

 *

 **/

static inline void sg_mark_end(struct scatterlist *sg)

{

#ifdef CONFIG_DEBUG_SG

	BUG_ON(sg->sg_magic != SG_MAGIC);

#endif

	/*

	 * Set termination bit, clear potential chain bit

	 */

	sg->page_link |= 0x02;

	sg->page_link &= ~0x01;

}

/**

 * sg_unmark_end - Undo setting the end of the scatterlist

 * @sg:		 SG entryScatterlist

 *

 * Description:

 *   Removes the termination marker from the given entry of the scatterlist.

 *

 **/

static inline void sg_unmark_end(struct scatterlist *sg)

{

#ifdef CONFIG_DEBUG_SG

	BUG_ON(sg->sg_magic != SG_MAGIC);

#endif

	sg->page_link &= ~0x02;

}

/**

 * 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 dma_addr_t 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;

//}

int sg_nents(struct scatterlist *sg);

struct scatterlist *sg_next(struct scatterlist *);

struct scatterlist *sg_last(struct scatterlist *s, unsigned int);

void sg_init_table(struct scatterlist *, unsigned int);

void sg_init_one(struct scatterlist *, const void *, unsigned int);

typedef struct scatterlist *(sg_alloc_fn)(unsigned int, gfp_t);

typedef void (sg_free_fn)(struct scatterlist *, unsigned int);

void __sg_free_table(struct sg_table *, unsigned int, sg_free_fn *);

void sg_free_table(struct sg_table *);

int __sg_alloc_table(struct sg_table *, unsigned int, unsigned int, gfp_t,

		     sg_alloc_fn *);

int sg_alloc_table(struct sg_table *, unsigned int, gfp_t);

int sg_alloc_table_from_pages(struct sg_table *sgt,

	struct page **pages, unsigned int n_pages,

	unsigned long offset, unsigned long size,

	gfp_t gfp_mask);

size_t sg_copy_from_buffer(struct scatterlist *sgl, unsigned int nents,

			   void *buf, size_t buflen);

size_t sg_copy_to_buffer(struct scatterlist *sgl, unsigned int nents,

			 void *buf, size_t buflen);

/*

 * Maximum number of entries that will be allocated in one piece, if

 * a list larger than this is required then chaining will be utilized.

 */

#define SG_MAX_SINGLE_ALLOC     (4*PAGE_SIZE / sizeof(struct scatterlist))

/*

 * sg page iterator

 *

 * Iterates over sg entries page-by-page.  On each successful iteration,

 * you can call sg_page_iter_page(@piter) and sg_page_iter_dma_address(@piter)

 * to get the current page and its dma address. @piter->sg will point to the

 * sg holding this page and @piter->sg_pgoffset to the page's page offset

 * within the sg. The iteration will stop either when a maximum number of sg

 * entries was reached or a terminating sg (sg_last(sg) == true) was reached.

 */

struct sg_page_iter {

	struct scatterlist	*sg;		/* sg holding the page */

	unsigned int		sg_pgoffset;	/* page offset within the sg */

	/* these are internal states, keep away */

	unsigned int		__nents;	/* remaining sg entries */

	int			__pg_advance;	/* nr pages to advance at the

						 * next step */

};

bool __sg_page_iter_next(struct sg_page_iter *piter);

void __sg_page_iter_start(struct sg_page_iter *piter,

			  struct scatterlist *sglist, unsigned int nents,

			  unsigned long pgoffset);

/**

 * sg_page_iter_page - get the current page held by the page iterator

 * @piter:	page iterator holding the page

 */

static inline struct page *sg_page_iter_page(struct sg_page_iter *piter)

{

	return nth_page(sg_page(piter->sg), piter->sg_pgoffset);

}

/**

 * sg_page_iter_dma_address - get the dma address of the current page held by

 * the page iterator.

 * @piter:	page iterator holding the page

 */

static inline dma_addr_t sg_page_iter_dma_address(struct sg_page_iter *piter)

{

	return sg_dma_address(piter->sg) + (piter->sg_pgoffset << PAGE_SHIFT);

}

/**

 * for_each_sg_page - iterate over the pages of the given sg list

 * @sglist:	sglist to iterate over

 * @piter:	page iterator to hold current page, sg, sg_pgoffset

 * @nents:	maximum number of sg entries to iterate over

 * @pgoffset:	starting page offset

 */

#define for_each_sg_page(sglist, piter, nents, pgoffset)		   \

	for (__sg_page_iter_start((piter), (sglist), (nents), (pgoffset)); \

	     __sg_page_iter_next(piter);)

/*

 * Mapping sg iterator

 *

 * Iterates over sg entries mapping page-by-page.  On each successful

 * iteration, @miter->page points to the mapped page and

 * @miter->length bytes of data can be accessed at @miter->addr.  As

 * long as an interation is enclosed between start and stop, the user

 * is free to choose control structure and when to stop.

 *

 * @miter->consumed is set to @miter->length on each iteration.  It

 * can be adjusted if the user can't consume all the bytes in one go.

 * Also, a stopped iteration can be resumed by calling next on it.

 * This is useful when iteration needs to release all resources and

 * continue later (e.g. at the next interrupt).

 */

#define SG_MITER_ATOMIC		(1 << 0)	 /* use kmap_atomic */

#define SG_MITER_TO_SG		(1 << 1)	/* flush back to phys on unmap */

#define SG_MITER_FROM_SG	(1 << 2)	/* nop */

struct sg_mapping_iter {

	/* the following three fields can be accessed directly */

	struct page		*page;		/* currently mapped page */

	void			*addr;		/* pointer to the mapped area */

	size_t			length;		/* length of the mapped area */

	size_t			consumed;	/* number of consumed bytes */

	struct sg_page_iter	piter;		/* page iterator */

	/* these are internal states, keep away */

	unsigned int		__offset;	/* offset within page */

	unsigned int		__remaining;	/* remaining bytes on page */

	unsigned int		__flags;

};

void sg_miter_start(struct sg_mapping_iter *miter, struct scatterlist *sgl,

		    unsigned int nents, unsigned int flags);

bool sg_miter_skip(struct sg_mapping_iter *miter, off_t offset);

bool sg_miter_next(struct sg_mapping_iter *miter);

void sg_miter_stop(struct sg_mapping_iter *miter);

#endif /* _LINUX_SCATTERLIST_H */