1/* SPDX-License-Identifier: GPL-2.0 */ 2#ifndef SCATTERLIST_H 3#define SCATTERLIST_H 4#include <linux/kernel.h> 5#include <linux/bug.h> 6 7struct scatterlist { 8 unsigned long page_link; 9 unsigned int offset; 10 unsigned int length; 11 dma_addr_t dma_address; 12}; 13 14/* Scatterlist helpers, stolen from linux/scatterlist.h */ 15#define sg_is_chain(sg) ((sg)->page_link & 0x01) 16#define sg_is_last(sg) ((sg)->page_link & 0x02) 17#define sg_chain_ptr(sg) \ 18 ((struct scatterlist *) ((sg)->page_link & ~0x03)) 19 20/** 21 * sg_assign_page - Assign a given page to an SG entry 22 * @sg: SG entry 23 * @page: The page 24 * 25 * Description: 26 * Assign page to sg entry. Also see sg_set_page(), the most commonly used 27 * variant. 28 * 29 **/ 30static inline void sg_assign_page(struct scatterlist *sg, struct page *page) 31{ 32 unsigned long page_link = sg->page_link & 0x3; 33 34 /* 35 * In order for the low bit stealing approach to work, pages 36 * must be aligned at a 32-bit boundary as a minimum. 37 */ 38 BUG_ON((unsigned long) page & 0x03); 39#ifdef CONFIG_DEBUG_SG 40 BUG_ON(sg_is_chain(sg)); 41#endif 42 sg->page_link = page_link | (unsigned long) page; 43} 44 45/** 46 * sg_set_page - Set sg entry to point at given page 47 * @sg: SG entry 48 * @page: The page 49 * @len: Length of data 50 * @offset: Offset into page 51 * 52 * Description: 53 * Use this function to set an sg entry pointing at a page, never assign 54 * the page directly. We encode sg table information in the lower bits 55 * of the page pointer. See sg_page() for looking up the page belonging 56 * to an sg entry. 57 * 58 **/ 59static inline void sg_set_page(struct scatterlist *sg, struct page *page, 60 unsigned int len, unsigned int offset) 61{ 62 sg_assign_page(sg, page); 63 sg->offset = offset; 64 sg->length = len; 65} 66 67static inline struct page *sg_page(struct scatterlist *sg) 68{ 69#ifdef CONFIG_DEBUG_SG 70 BUG_ON(sg_is_chain(sg)); 71#endif 72 return (struct page *)((sg)->page_link & ~0x3); 73} 74 75/* 76 * Loop over each sg element, following the pointer to a new list if necessary 77 */ 78#define for_each_sg(sglist, sg, nr, __i) \ 79 for (__i = 0, sg = (sglist); __i < (nr); __i++, sg = sg_next(sg)) 80 81/** 82 * sg_chain - Chain two sglists together 83 * @prv: First scatterlist 84 * @prv_nents: Number of entries in prv 85 * @sgl: Second scatterlist 86 * 87 * Description: 88 * Links @prv@ and @sgl@ together, to form a longer scatterlist. 89 * 90 **/ 91static inline void sg_chain(struct scatterlist *prv, unsigned int prv_nents, 92 struct scatterlist *sgl) 93{ 94 /* 95 * offset and length are unused for chain entry. Clear them. 96 */ 97 prv[prv_nents - 1].offset = 0; 98 prv[prv_nents - 1].length = 0; 99 100 /* 101 * Set lowest bit to indicate a link pointer, and make sure to clear 102 * the termination bit if it happens to be set. 103 */ 104 prv[prv_nents - 1].page_link = ((unsigned long) sgl | 0x01) & ~0x02; 105} 106 107/** 108 * sg_mark_end - Mark the end of the scatterlist 109 * @sg: SG entryScatterlist 110 * 111 * Description: 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. 114 * 115 **/ 116static inline void sg_mark_end(struct scatterlist *sg) 117{ 118 /* 119 * Set termination bit, clear potential chain bit 120 */ 121 sg->page_link |= 0x02; 122 sg->page_link &= ~0x01; 123} 124 125/** 126 * sg_unmark_end - Undo setting the end of the scatterlist 127 * @sg: SG entryScatterlist 128 * 129 * Description: 130 * Removes the termination marker from the given entry of the scatterlist. 131 * 132 **/ 133static inline void sg_unmark_end(struct scatterlist *sg) 134{ 135 sg->page_link &= ~0x02; 136} 137 138static inline struct scatterlist *sg_next(struct scatterlist *sg) 139{ 140 if (sg_is_last(sg)) 141 return NULL; 142 143 sg++; 144 if (unlikely(sg_is_chain(sg))) 145 sg = sg_chain_ptr(sg); 146 147 return sg; 148} 149 150static inline void sg_init_table(struct scatterlist *sgl, unsigned int nents) 151{ 152 memset(sgl, 0, sizeof(*sgl) * nents); 153 sg_mark_end(&sgl[nents - 1]); 154} 155 156static inline dma_addr_t sg_phys(struct scatterlist *sg) 157{ 158 return page_to_phys(sg_page(sg)) + sg->offset; 159} 160 161static inline void sg_set_buf(struct scatterlist *sg, const void *buf, 162 unsigned int buflen) 163{ 164 sg_set_page(sg, virt_to_page(buf), buflen, offset_in_page(buf)); 165} 166 167static inline void sg_init_one(struct scatterlist *sg, 168 const void *buf, unsigned int buflen) 169{ 170 sg_init_table(sg, 1); 171 sg_set_buf(sg, buf, buflen); 172} 173#endif /* SCATTERLIST_H */ 174