3 #include <linux/kernel.h>
6 unsigned long page_link
;
9 dma_addr_t dma_address
;
12 /* Scatterlist helpers, stolen from linux/scatterlist.h */
13 #define sg_is_chain(sg) ((sg)->page_link & 0x01)
14 #define sg_is_last(sg) ((sg)->page_link & 0x02)
15 #define sg_chain_ptr(sg) \
16 ((struct scatterlist *) ((sg)->page_link & ~0x03))
19 * sg_assign_page - Assign a given page to an SG entry
24 * Assign page to sg entry. Also see sg_set_page(), the most commonly used
28 static inline void sg_assign_page(struct scatterlist
*sg
, struct page
*page
)
30 unsigned long page_link
= sg
->page_link
& 0x3;
33 * In order for the low bit stealing approach to work, pages
34 * must be aligned at a 32-bit boundary as a minimum.
36 BUG_ON((unsigned long) page
& 0x03);
37 #ifdef CONFIG_DEBUG_SG
38 BUG_ON(sg
->sg_magic
!= SG_MAGIC
);
39 BUG_ON(sg_is_chain(sg
));
41 sg
->page_link
= page_link
| (unsigned long) page
;
45 * sg_set_page - Set sg entry to point at given page
48 * @len: Length of data
49 * @offset: Offset into page
52 * Use this function to set an sg entry pointing at a page, never assign
53 * the page directly. We encode sg table information in the lower bits
54 * of the page pointer. See sg_page() for looking up the page belonging
58 static inline void sg_set_page(struct scatterlist
*sg
, struct page
*page
,
59 unsigned int len
, unsigned int offset
)
61 sg_assign_page(sg
, page
);
66 static inline struct page
*sg_page(struct scatterlist
*sg
)
68 #ifdef CONFIG_DEBUG_SG
69 BUG_ON(sg
->sg_magic
!= SG_MAGIC
);
70 BUG_ON(sg_is_chain(sg
));
72 return (struct page
*)((sg
)->page_link
& ~0x3);
76 * Loop over each sg element, following the pointer to a new list if necessary
78 #define for_each_sg(sglist, sg, nr, __i) \
79 for (__i = 0, sg = (sglist); __i < (nr); __i++, sg = sg_next(sg))
82 * sg_chain - Chain two sglists together
83 * @prv: First scatterlist
84 * @prv_nents: Number of entries in prv
85 * @sgl: Second scatterlist
88 * Links @prv@ and @sgl@ together, to form a longer scatterlist.
91 static inline void sg_chain(struct scatterlist
*prv
, unsigned int prv_nents
,
92 struct scatterlist
*sgl
)
95 * offset and length are unused for chain entry. Clear them.
97 prv
[prv_nents
- 1].offset
= 0;
98 prv
[prv_nents
- 1].length
= 0;
101 * Set lowest bit to indicate a link pointer, and make sure to clear
102 * the termination bit if it happens to be set.
104 prv
[prv_nents
- 1].page_link
= ((unsigned long) sgl
| 0x01) & ~0x02;
108 * sg_mark_end - Mark the end of the scatterlist
109 * @sg: SG entryScatterlist
112 * Marks the passed in sg entry as the termination point for the sg
113 * table. A call to sg_next() on this entry will return NULL.
116 static inline void sg_mark_end(struct scatterlist
*sg
)
118 #ifdef CONFIG_DEBUG_SG
119 BUG_ON(sg
->sg_magic
!= SG_MAGIC
);
122 * Set termination bit, clear potential chain bit
124 sg
->page_link
|= 0x02;
125 sg
->page_link
&= ~0x01;
129 * sg_unmark_end - Undo setting the end of the scatterlist
130 * @sg: SG entryScatterlist
133 * Removes the termination marker from the given entry of the scatterlist.
136 static inline void sg_unmark_end(struct scatterlist
*sg
)
138 #ifdef CONFIG_DEBUG_SG
139 BUG_ON(sg
->sg_magic
!= SG_MAGIC
);
141 sg
->page_link
&= ~0x02;
144 static inline struct scatterlist
*sg_next(struct scatterlist
*sg
)
146 #ifdef CONFIG_DEBUG_SG
147 BUG_ON(sg
->sg_magic
!= SG_MAGIC
);
153 if (unlikely(sg_is_chain(sg
)))
154 sg
= sg_chain_ptr(sg
);
159 static inline void sg_init_table(struct scatterlist
*sgl
, unsigned int nents
)
161 memset(sgl
, 0, sizeof(*sgl
) * nents
);
162 #ifdef CONFIG_DEBUG_SG
165 for (i
= 0; i
< nents
; i
++)
166 sgl
[i
].sg_magic
= SG_MAGIC
;
169 sg_mark_end(&sgl
[nents
- 1]);
172 static inline dma_addr_t
sg_phys(struct scatterlist
*sg
)
174 return page_to_phys(sg_page(sg
)) + sg
->offset
;
177 static inline void sg_set_buf(struct scatterlist
*sg
, const void *buf
,
180 sg_set_page(sg
, virt_to_page(buf
), buflen
, offset_in_page(buf
));
183 static inline void sg_init_one(struct scatterlist
*sg
,
184 const void *buf
, unsigned int buflen
)
186 sg_init_table(sg
, 1);
187 sg_set_buf(sg
, buf
, buflen
);
189 #endif /* SCATTERLIST_H */
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