[GitHub/mt8127/android_kernel_alcatel_ttab.git] / include / linux / scatterlist.h

#ifndef _LINUX_SCATTERLIST_H
#define _LINUX_SCATTERLIST_H

#include <linux/string.h>
#include <linux/bug.h>
#include <linux/mm.h>

#include <asm/types.h>
#include <asm/scatterlist.h>
#include <asm/io.h>

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)
{
#ifdef CONFIG_DEBUG_SG
	BUG_ON(!virt_addr_valid(buf));
#endif
	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		(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_next(struct sg_mapping_iter *miter);
void sg_miter_stop(struct sg_mapping_iter *miter);

#endif /* _LINUX_SCATTERLIST_H */
Commit	Line	Data
1da177e4 LT	1	#ifndef _LINUX_SCATTERLIST_H
	2	#define _LINUX_SCATTERLIST_H
	3
187f1882 PG	4	#include <linux/string.h>
	5	#include <linux/bug.h>
	6	#include <linux/mm.h>
	7
85cdffcd	8	#include <asm/types.h>
d32311fe	9	#include <asm/scatterlist.h>
18dabf47 JA	10	#include <asm/io.h>
18dabf47 JA	11
0db9299f JA	12	struct sg_table {
	13	struct scatterlist sgl; / the list */
	14	unsigned int nents; /* number of mapped entries */
	15	unsigned int orig_nents; /* original size of list */
	16	};
	17
18dabf47 JA	18	/*
	19	* Notes on SG table design.
	20	*
	21	* Architectures must provide an unsigned long page_link field in the
	22	* scatterlist struct. We use that to place the page pointer AND encode
	23	* information about the sg table as well. The two lower bits are reserved
	24	* for this information.
	25	*
	26	* If bit 0 is set, then the page_link contains a pointer to the next sg
	27	* table list. Otherwise the next entry is at sg + 1.
	28	*
	29	* If bit 1 is set, then this sg entry is the last element in a list.
	30	*
	31	* See sg_next().
	32	*
	33	*/
1da177e4	34
d6ec0842 JA	35	#define SG_MAGIC 0x87654321
d6ec0842 JA	36
645a8d94 TH	37	/*
	38	* We overload the LSB of the page pointer to indicate whether it's
	39	* a valid sg entry, or whether it points to the start of a new scatterlist.
	40	* Those low bits are there for everyone! (thanks mason :-)
	41	*/
	42	#define sg_is_chain(sg) ((sg)->page_link & 0x01)
	43	#define sg_is_last(sg) ((sg)->page_link & 0x02)
	44	#define sg_chain_ptr(sg) \
	45	((struct scatterlist *) ((sg)->page_link & ~0x03))
	46
82f66fbe	47	/**
642f1490 JA	48	* sg_assign_page - Assign a given page to an SG entry
	49	* @sg: SG entry
	50	* @page: The page
82f66fbe JA	51	*
82f66fbe JA	52	* Description:
642f1490 JA	53	* Assign page to sg entry. Also see sg_set_page(), the most commonly used
642f1490 JA	54	* variant.
82f66fbe JA	55	*
82f66fbe JA	56	**/
642f1490	57	static inline void sg_assign_page(struct scatterlist sg, struct page page)
82f66fbe	58	{
18dabf47 JA	59	unsigned long page_link = sg->page_link & 0x3;
18dabf47 JA	60
de26103d JA	61	/*
	62	* In order for the low bit stealing approach to work, pages
	63	* must be aligned at a 32-bit boundary as a minimum.
	64	*/
	65	BUG_ON((unsigned long) page & 0x03);
d6ec0842 JA	66	#ifdef CONFIG_DEBUG_SG
d6ec0842 JA	67	BUG_ON(sg->sg_magic != SG_MAGIC);
645a8d94	68	BUG_ON(sg_is_chain(sg));
d6ec0842	69	#endif
18dabf47	70	sg->page_link = page_link \| (unsigned long) page;
82f66fbe JA	71	}
82f66fbe JA	72
642f1490 JA	73	/**
	74	* sg_set_page - Set sg entry to point at given page
	75	* @sg: SG entry
	76	* @page: The page
	77	* @len: Length of data
	78	* @offset: Offset into page
	79	*
	80	* Description:
	81	* Use this function to set an sg entry pointing at a page, never assign
	82	* the page directly. We encode sg table information in the lower bits
	83	* of the page pointer. See sg_page() for looking up the page belonging
	84	* to an sg entry.
	85	*
	86	**/
	87	static inline void sg_set_page(struct scatterlist sg, struct page page,
	88	unsigned int len, unsigned int offset)
	89	{
	90	sg_assign_page(sg, page);
	91	sg->offset = offset;
	92	sg->length = len;
	93	}
	94
645a8d94 TH	95	static inline struct page sg_page(struct scatterlist sg)
	96	{
	97	#ifdef CONFIG_DEBUG_SG
	98	BUG_ON(sg->sg_magic != SG_MAGIC);
	99	BUG_ON(sg_is_chain(sg));
	100	#endif
	101	return (struct page *)((sg)->page_link & ~0x3);
	102	}
82f66fbe	103
18dabf47 JA	104	/**
	105	* sg_set_buf - Set sg entry to point at given data
	106	* @sg: SG entry
	107	* @buf: Data
	108	* @buflen: Data length
	109	*
	110	**/
03fd9cee	111	static inline void sg_set_buf(struct scatterlist sg, const void buf,
d32311fe HX	112	unsigned int buflen)
d32311fe HX	113	{
ac4e97ab RR	114	#ifdef CONFIG_DEBUG_SG
	115	BUG_ON(!virt_addr_valid(buf));
	116	#endif
642f1490	117	sg_set_page(sg, virt_to_page(buf), buflen, offset_in_page(buf));
1da177e4 LT	118	}
1da177e4 LT	119
96b418c9 JA	120	/*
	121	* Loop over each sg element, following the pointer to a new list if necessary
	122	*/
	123	#define for_each_sg(sglist, sg, nr, __i) \
	124	for (__i = 0, sg = (sglist); __i < (nr); __i++, sg = sg_next(sg))
	125
70eb8040 JA	126	/**
	127	* sg_chain - Chain two sglists together
	128	* @prv: First scatterlist
	129	* @prv_nents: Number of entries in prv
	130	* @sgl: Second scatterlist
	131	*
18dabf47 JA	132	* Description:
18dabf47 JA	133	* Links @prv@ and @sgl@ together, to form a longer scatterlist.
70eb8040	134	*
18dabf47	135	**/
70eb8040 JA	136	static inline void sg_chain(struct scatterlist *prv, unsigned int prv_nents,
	137	struct scatterlist *sgl)
	138	{
	139	#ifndef ARCH_HAS_SG_CHAIN
	140	BUG();
	141	#endif
645a8d94 TH	142
	143	/*
	144	* offset and length are unused for chain entry. Clear them.
	145	*/
b801a1e7 RR	146	prv[prv_nents - 1].offset = 0;
b801a1e7 RR	147	prv[prv_nents - 1].length = 0;
645a8d94	148
73fd546a JA	149	/*
	150	* Set lowest bit to indicate a link pointer, and make sure to clear
	151	* the termination bit if it happens to be set.
	152	*/
	153	prv[prv_nents - 1].page_link = ((unsigned long) sgl \| 0x01) & ~0x02;
70eb8040 JA	154	}
70eb8040 JA	155
82f66fbe JA	156	/**
82f66fbe JA	157	* sg_mark_end - Mark the end of the scatterlist
c46f2334	158	* @sg: SG entryScatterlist
82f66fbe JA	159	*
82f66fbe JA	160	* Description:
c46f2334 JA	161	* Marks the passed in sg entry as the termination point for the sg
c46f2334 JA	162	* table. A call to sg_next() on this entry will return NULL.
82f66fbe JA	163	*
82f66fbe JA	164	**/
c46f2334	165	static inline void sg_mark_end(struct scatterlist *sg)
82f66fbe	166	{
c46f2334 JA	167	#ifdef CONFIG_DEBUG_SG
	168	BUG_ON(sg->sg_magic != SG_MAGIC);
	169	#endif
	170	/*
	171	* Set termination bit, clear potential chain bit
	172	*/
18dabf47	173	sg->page_link \|= 0x02;
c46f2334	174	sg->page_link &= ~0x01;
82f66fbe JA	175	}
82f66fbe JA	176
c8164d89 PB	177	/**
	178	* sg_unmark_end - Undo setting the end of the scatterlist
	179	* @sg: SG entryScatterlist
	180	*
	181	* Description:
	182	* Removes the termination marker from the given entry of the scatterlist.
	183	*
	184	**/
	185	static inline void sg_unmark_end(struct scatterlist *sg)
	186	{
	187	#ifdef CONFIG_DEBUG_SG
	188	BUG_ON(sg->sg_magic != SG_MAGIC);
	189	#endif
	190	sg->page_link &= ~0x02;
	191	}
	192
82f66fbe JA	193	/**
	194	* sg_phys - Return physical address of an sg entry
	195	* @sg: SG entry
	196	*
	197	* Description:
	198	* This calls page_to_phys() on the page in this sg entry, and adds the
	199	* sg offset. The caller must know that it is legal to call page_to_phys()
	200	* on the sg page.
	201	*
	202	**/
85cdffcd	203	static inline dma_addr_t sg_phys(struct scatterlist *sg)
82f66fbe JA	204	{
	205	return page_to_phys(sg_page(sg)) + sg->offset;
	206	}
	207
	208	/**
	209	* sg_virt - Return virtual address of an sg entry
18dabf47	210	* @sg: SG entry
82f66fbe JA	211	*
	212	* Description:
	213	* This calls page_address() on the page in this sg entry, and adds the
	214	* sg offset. The caller must know that the sg page has a valid virtual
	215	* mapping.
	216	*
	217	**/
	218	static inline void sg_virt(struct scatterlist sg)
	219	{
	220	return page_address(sg_page(sg)) + sg->offset;
	221	}
	222
2e484610	223	int sg_nents(struct scatterlist *sg);
0db9299f JA	224	struct scatterlist sg_next(struct scatterlist );
	225	struct scatterlist sg_last(struct scatterlist s, unsigned int);
	226	void sg_init_table(struct scatterlist *, unsigned int);
	227	void sg_init_one(struct scatterlist , const void , unsigned int);
	228
	229	typedef struct scatterlist *(sg_alloc_fn)(unsigned int, gfp_t);
	230	typedef void (sg_free_fn)(struct scatterlist *, unsigned int);
	231
7cedb1f1	232	void __sg_free_table(struct sg_table , unsigned int, sg_free_fn );
0db9299f	233	void sg_free_table(struct sg_table *);
7cedb1f1 JB	234	int __sg_alloc_table(struct sg_table *, unsigned int, unsigned int, gfp_t,
7cedb1f1 JB	235	sg_alloc_fn *);
0db9299f	236	int sg_alloc_table(struct sg_table *, unsigned int, gfp_t);
efc42bc9 TS	237	int sg_alloc_table_from_pages(struct sg_table *sgt,
	238	struct page **pages, unsigned int n_pages,
	239	unsigned long offset, unsigned long size,
	240	gfp_t gfp_mask);
0db9299f	241
b1adaf65 FT	242	size_t sg_copy_from_buffer(struct scatterlist *sgl, unsigned int nents,
	243	void *buf, size_t buflen);
	244	size_t sg_copy_to_buffer(struct scatterlist *sgl, unsigned int nents,
	245	void *buf, size_t buflen);
	246
0db9299f JA	247	/*
	248	* Maximum number of entries that will be allocated in one piece, if
	249	* a list larger than this is required then chaining will be utilized.
	250	*/
	251	#define SG_MAX_SINGLE_ALLOC (PAGE_SIZE / sizeof(struct scatterlist))
	252
a321e91b ID	253	/*
	254	* sg page iterator
	255	*
	256	* Iterates over sg entries page-by-page. On each successful iteration,
2db76d7c ID	257	* you can call sg_page_iter_page(@piter) and sg_page_iter_dma_address(@piter)
	258	* to get the current page and its dma address. @piter->sg will point to the
	259	* sg holding this page and @piter->sg_pgoffset to the page's page offset
	260	* within the sg. The iteration will stop either when a maximum number of sg
	261	* entries was reached or a terminating sg (sg_last(sg) == true) was reached.
a321e91b ID	262	*/
a321e91b ID	263	struct sg_page_iter {
a321e91b ID	264	struct scatterlist sg; / sg holding the page */
	265	unsigned int sg_pgoffset; /* page offset within the sg */
	266
	267	/* these are internal states, keep away */
	268	unsigned int __nents; /* remaining sg entries */
	269	int __pg_advance; /* nr pages to advance at the
	270	* next step */
	271	};
	272
	273	bool __sg_page_iter_next(struct sg_page_iter *piter);
	274	void __sg_page_iter_start(struct sg_page_iter *piter,
	275	struct scatterlist *sglist, unsigned int nents,
	276	unsigned long pgoffset);
2db76d7c ID	277	/**
	278	* sg_page_iter_page - get the current page held by the page iterator
	279	* @piter: page iterator holding the page
	280	*/
	281	static inline struct page sg_page_iter_page(struct sg_page_iter piter)
	282	{
	283	return nth_page(sg_page(piter->sg), piter->sg_pgoffset);
	284	}
	285
	286	/**
	287	* sg_page_iter_dma_address - get the dma address of the current page held by
	288	* the page iterator.
	289	* @piter: page iterator holding the page
	290	*/
	291	static inline dma_addr_t sg_page_iter_dma_address(struct sg_page_iter *piter)
	292	{
	293	return sg_dma_address(piter->sg) + (piter->sg_pgoffset << PAGE_SHIFT);
	294	}
a321e91b ID	295
	296	/**
	297	* for_each_sg_page - iterate over the pages of the given sg list
	298	* @sglist: sglist to iterate over
	299	* @piter: page iterator to hold current page, sg, sg_pgoffset
	300	* @nents: maximum number of sg entries to iterate over
	301	* @pgoffset: starting page offset
	302	*/
	303	#define for_each_sg_page(sglist, piter, nents, pgoffset) \
	304	for (__sg_page_iter_start((piter), (sglist), (nents), (pgoffset)); \
	305	__sg_page_iter_next(piter);)
137d3edb TH	306
	307	/*
	308	* Mapping sg iterator
	309	*
	310	* Iterates over sg entries mapping page-by-page. On each successful
	311	* iteration, @miter->page points to the mapped page and
	312	* @miter->length bytes of data can be accessed at @miter->addr. As
	313	* long as an interation is enclosed between start and stop, the user
	314	* is free to choose control structure and when to stop.
	315	*
	316	* @miter->consumed is set to @miter->length on each iteration. It
	317	* can be adjusted if the user can't consume all the bytes in one go.
	318	* Also, a stopped iteration can be resumed by calling next on it.
	319	* This is useful when iteration needs to release all resources and
	320	* continue later (e.g. at the next interrupt).
	321	*/
	322
	323	#define SG_MITER_ATOMIC (1 << 0) /* use kmap_atomic */
6de7e356 SAS	324	#define SG_MITER_TO_SG (1 << 1) /* flush back to phys on unmap */
6de7e356 SAS	325	#define SG_MITER_FROM_SG (1 << 2) /* nop */
137d3edb TH	326
	327	struct sg_mapping_iter {
	328	/* the following three fields can be accessed directly */
	329	struct page page; / currently mapped page */
	330	void addr; / pointer to the mapped area */
	331	size_t length; /* length of the mapped area */
	332	size_t consumed; /* number of consumed bytes */
4225fc85	333	struct sg_page_iter piter; /* page iterator */
137d3edb TH	334
137d3edb TH	335	/* these are internal states, keep away */
4225fc85 ID	336	unsigned int __offset; /* offset within page */
4225fc85 ID	337	unsigned int __remaining; /* remaining bytes on page */
137d3edb TH	338	unsigned int __flags;
	339	};
	340
	341	void sg_miter_start(struct sg_mapping_iter miter, struct scatterlist sgl,
	342	unsigned int nents, unsigned int flags);
	343	bool sg_miter_next(struct sg_mapping_iter *miter);
	344	void sg_miter_stop(struct sg_mapping_iter *miter);
	345
1da177e4	346	#endif /* _LINUX_SCATTERLIST_H */