root/tools/virtio/linux/scatterlist.h

INCLUDED FROM

DEFINITIONS

1. sg_assign_page
2. sg_set_page
3. sg_page
4. sg_chain
5. sg_mark_end
6. sg_unmark_end
7. sg_next
8. sg_init_table
9. sg_phys
10. sg_set_buf
11. sg_init_one

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 #ifndef SCATTERLIST_H
   3 #define SCATTERLIST_H
   4 #include <linux/kernel.h>
   5 
   6 struct scatterlist {
   7         unsigned long   page_link;
   8         unsigned int    offset;
   9         unsigned int    length;
  10         dma_addr_t      dma_address;
  11 };
  12 
  13 /* Scatterlist helpers, stolen from linux/scatterlist.h */
  14 #define sg_is_chain(sg)         ((sg)->page_link & 0x01)
  15 #define sg_is_last(sg)          ((sg)->page_link & 0x02)
  16 #define sg_chain_ptr(sg)        \
  17         ((struct scatterlist *) ((sg)->page_link & ~0x03))
  18 
  19 /**
  20  * sg_assign_page - Assign a given page to an SG entry
  21  * @sg:             SG entry
  22  * @page:           The page
  23  *
  24  * Description:
  25  *   Assign page to sg entry. Also see sg_set_page(), the most commonly used
  26  *   variant.
  27  *
  28  **/
  29 static inline void sg_assign_page(struct scatterlist *sg, struct page *page)
  30 {
  31         unsigned long page_link = sg->page_link & 0x3;
  32 
  33         /*
  34          * In order for the low bit stealing approach to work, pages
  35          * must be aligned at a 32-bit boundary as a minimum.
  36          */
  37         BUG_ON((unsigned long) page & 0x03);
  38 #ifdef CONFIG_DEBUG_SG
  39         BUG_ON(sg_is_chain(sg));
  40 #endif
  41         sg->page_link = page_link | (unsigned long) page;
  42 }
  43 
  44 /**
  45  * sg_set_page - Set sg entry to point at given page
  46  * @sg:          SG entry
  47  * @page:        The page
  48  * @len:         Length of data
  49  * @offset:      Offset into page
  50  *
  51  * Description:
  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
  55  *   to an sg entry.
  56  *
  57  **/
  58 static inline void sg_set_page(struct scatterlist *sg, struct page *page,
  59                                unsigned int len, unsigned int offset)
  60 {
  61         sg_assign_page(sg, page);
  62         sg->offset = offset;
  63         sg->length = len;
  64 }
  65 
  66 static inline struct page *sg_page(struct scatterlist *sg)
  67 {
  68 #ifdef CONFIG_DEBUG_SG
  69         BUG_ON(sg_is_chain(sg));
  70 #endif
  71         return (struct page *)((sg)->page_link & ~0x3);
  72 }
  73 
  74 /*
  75  * Loop over each sg element, following the pointer to a new list if necessary
  76  */
  77 #define for_each_sg(sglist, sg, nr, __i)        \
  78         for (__i = 0, sg = (sglist); __i < (nr); __i++, sg = sg_next(sg))
  79 
  80 /**
  81  * sg_chain - Chain two sglists together
  82  * @prv:        First scatterlist
  83  * @prv_nents:  Number of entries in prv
  84  * @sgl:        Second scatterlist
  85  *
  86  * Description:
  87  *   Links @prv@ and @sgl@ together, to form a longer scatterlist.
  88  *
  89  **/
  90 static inline void sg_chain(struct scatterlist *prv, unsigned int prv_nents,
  91                             struct scatterlist *sgl)
  92 {
  93         /*
  94          * offset and length are unused for chain entry.  Clear them.
  95          */
  96         prv[prv_nents - 1].offset = 0;
  97         prv[prv_nents - 1].length = 0;
  98 
  99         /*
 100          * Set lowest bit to indicate a link pointer, and make sure to clear
 101          * the termination bit if it happens to be set.
 102          */
 103         prv[prv_nents - 1].page_link = ((unsigned long) sgl | 0x01) & ~0x02;
 104 }
 105 
 106 /**
 107  * sg_mark_end - Mark the end of the scatterlist
 108  * @sg:          SG entryScatterlist
 109  *
 110  * Description:
 111  *   Marks the passed in sg entry as the termination point for the sg
 112  *   table. A call to sg_next() on this entry will return NULL.
 113  *
 114  **/
 115 static inline void sg_mark_end(struct scatterlist *sg)
 116 {
 117         /*
 118          * Set termination bit, clear potential chain bit
 119          */
 120         sg->page_link |= 0x02;
 121         sg->page_link &= ~0x01;
 122 }
 123 
 124 /**
 125  * sg_unmark_end - Undo setting the end of the scatterlist
 126  * @sg:          SG entryScatterlist
 127  *
 128  * Description:
 129  *   Removes the termination marker from the given entry of the scatterlist.
 130  *
 131  **/
 132 static inline void sg_unmark_end(struct scatterlist *sg)
 133 {
 134         sg->page_link &= ~0x02;
 135 }
 136 
 137 static inline struct scatterlist *sg_next(struct scatterlist *sg)
 138 {
 139         if (sg_is_last(sg))
 140                 return NULL;
 141 
 142         sg++;
 143         if (unlikely(sg_is_chain(sg)))
 144                 sg = sg_chain_ptr(sg);
 145 
 146         return sg;
 147 }
 148 
 149 static inline void sg_init_table(struct scatterlist *sgl, unsigned int nents)
 150 {
 151         memset(sgl, 0, sizeof(*sgl) * nents);
 152         sg_mark_end(&sgl[nents - 1]);
 153 }
 154 
 155 static inline dma_addr_t sg_phys(struct scatterlist *sg)
 156 {
 157         return page_to_phys(sg_page(sg)) + sg->offset;
 158 }
 159 
 160 static inline void sg_set_buf(struct scatterlist *sg, const void *buf,
 161                               unsigned int buflen)
 162 {
 163         sg_set_page(sg, virt_to_page(buf), buflen, offset_in_page(buf));
 164 }
 165 
 166 static inline void sg_init_one(struct scatterlist *sg,
 167                                const void *buf, unsigned int buflen)
 168 {
 169         sg_init_table(sg, 1);
 170         sg_set_buf(sg, buf, buflen);
 171 }
 172 #endif /* SCATTERLIST_H */