b1adaf65ba
This patch adds new three helper functions to copy data between an SG list and a linear buffer. - sg_copy_from_buffer copies data from linear buffer to an SG list - sg_copy_to_buffer copies data from an SG list to a linear buffer When the APIs copy data from a linear buffer to an SG list, flush_kernel_dcache_page is called. It's not necessary for everyone but it's a no-op on most architectures and in general the API is not used in performance critical path. Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp> Acked-by: Jens Axboe <jens.axboe@oracle.com> Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
228 lines
6.2 KiB
C
228 lines
6.2 KiB
C
#ifndef _LINUX_SCATTERLIST_H
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#define _LINUX_SCATTERLIST_H
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#include <asm/types.h>
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#include <asm/scatterlist.h>
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#include <linux/mm.h>
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#include <linux/string.h>
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#include <asm/io.h>
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struct sg_table {
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struct scatterlist *sgl; /* the list */
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unsigned int nents; /* number of mapped entries */
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unsigned int orig_nents; /* original size of list */
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};
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/*
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* Notes on SG table design.
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*
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* Architectures must provide an unsigned long page_link field in the
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* scatterlist struct. We use that to place the page pointer AND encode
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* information about the sg table as well. The two lower bits are reserved
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* for this information.
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*
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* If bit 0 is set, then the page_link contains a pointer to the next sg
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* table list. Otherwise the next entry is at sg + 1.
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*
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* If bit 1 is set, then this sg entry is the last element in a list.
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*
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* See sg_next().
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*
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*/
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#define SG_MAGIC 0x87654321
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/*
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* We overload the LSB of the page pointer to indicate whether it's
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* a valid sg entry, or whether it points to the start of a new scatterlist.
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* Those low bits are there for everyone! (thanks mason :-)
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*/
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#define sg_is_chain(sg) ((sg)->page_link & 0x01)
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#define sg_is_last(sg) ((sg)->page_link & 0x02)
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#define sg_chain_ptr(sg) \
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((struct scatterlist *) ((sg)->page_link & ~0x03))
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/**
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* sg_assign_page - Assign a given page to an SG entry
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* @sg: SG entry
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* @page: The page
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*
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* Description:
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* Assign page to sg entry. Also see sg_set_page(), the most commonly used
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* variant.
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*
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**/
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static inline void sg_assign_page(struct scatterlist *sg, struct page *page)
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{
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unsigned long page_link = sg->page_link & 0x3;
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/*
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* In order for the low bit stealing approach to work, pages
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* must be aligned at a 32-bit boundary as a minimum.
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*/
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BUG_ON((unsigned long) page & 0x03);
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#ifdef CONFIG_DEBUG_SG
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BUG_ON(sg->sg_magic != SG_MAGIC);
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BUG_ON(sg_is_chain(sg));
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#endif
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sg->page_link = page_link | (unsigned long) page;
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}
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/**
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* sg_set_page - Set sg entry to point at given page
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* @sg: SG entry
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* @page: The page
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* @len: Length of data
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* @offset: Offset into page
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*
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* Description:
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* Use this function to set an sg entry pointing at a page, never assign
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* the page directly. We encode sg table information in the lower bits
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* of the page pointer. See sg_page() for looking up the page belonging
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* to an sg entry.
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*
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**/
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static inline void sg_set_page(struct scatterlist *sg, struct page *page,
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unsigned int len, unsigned int offset)
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{
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sg_assign_page(sg, page);
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sg->offset = offset;
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sg->length = len;
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}
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static inline struct page *sg_page(struct scatterlist *sg)
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{
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#ifdef CONFIG_DEBUG_SG
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BUG_ON(sg->sg_magic != SG_MAGIC);
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BUG_ON(sg_is_chain(sg));
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#endif
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return (struct page *)((sg)->page_link & ~0x3);
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}
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/**
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* sg_set_buf - Set sg entry to point at given data
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* @sg: SG entry
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* @buf: Data
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* @buflen: Data length
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*
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**/
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static inline void sg_set_buf(struct scatterlist *sg, const void *buf,
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unsigned int buflen)
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{
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sg_set_page(sg, virt_to_page(buf), buflen, offset_in_page(buf));
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}
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/*
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* Loop over each sg element, following the pointer to a new list if necessary
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*/
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#define for_each_sg(sglist, sg, nr, __i) \
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for (__i = 0, sg = (sglist); __i < (nr); __i++, sg = sg_next(sg))
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/**
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* sg_chain - Chain two sglists together
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* @prv: First scatterlist
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* @prv_nents: Number of entries in prv
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* @sgl: Second scatterlist
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*
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* Description:
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* Links @prv@ and @sgl@ together, to form a longer scatterlist.
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*
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**/
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static inline void sg_chain(struct scatterlist *prv, unsigned int prv_nents,
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struct scatterlist *sgl)
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{
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#ifndef ARCH_HAS_SG_CHAIN
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BUG();
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#endif
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/*
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* offset and length are unused for chain entry. Clear them.
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*/
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prv[prv_nents - 1].offset = 0;
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prv[prv_nents - 1].length = 0;
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/*
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* Set lowest bit to indicate a link pointer, and make sure to clear
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* the termination bit if it happens to be set.
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*/
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prv[prv_nents - 1].page_link = ((unsigned long) sgl | 0x01) & ~0x02;
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}
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/**
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* sg_mark_end - Mark the end of the scatterlist
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* @sg: SG entryScatterlist
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*
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* Description:
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* Marks the passed in sg entry as the termination point for the sg
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* table. A call to sg_next() on this entry will return NULL.
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*
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**/
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static inline void sg_mark_end(struct scatterlist *sg)
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{
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#ifdef CONFIG_DEBUG_SG
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BUG_ON(sg->sg_magic != SG_MAGIC);
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#endif
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/*
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* Set termination bit, clear potential chain bit
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*/
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sg->page_link |= 0x02;
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sg->page_link &= ~0x01;
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}
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/**
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* sg_phys - Return physical address of an sg entry
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* @sg: SG entry
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*
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* Description:
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* This calls page_to_phys() on the page in this sg entry, and adds the
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* sg offset. The caller must know that it is legal to call page_to_phys()
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* on the sg page.
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*
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**/
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static inline dma_addr_t sg_phys(struct scatterlist *sg)
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{
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return page_to_phys(sg_page(sg)) + sg->offset;
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}
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/**
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* sg_virt - Return virtual address of an sg entry
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* @sg: SG entry
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*
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* Description:
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* This calls page_address() on the page in this sg entry, and adds the
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* sg offset. The caller must know that the sg page has a valid virtual
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* mapping.
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*
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**/
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static inline void *sg_virt(struct scatterlist *sg)
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{
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return page_address(sg_page(sg)) + sg->offset;
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}
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struct scatterlist *sg_next(struct scatterlist *);
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struct scatterlist *sg_last(struct scatterlist *s, unsigned int);
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void sg_init_table(struct scatterlist *, unsigned int);
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void sg_init_one(struct scatterlist *, const void *, unsigned int);
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typedef struct scatterlist *(sg_alloc_fn)(unsigned int, gfp_t);
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typedef void (sg_free_fn)(struct scatterlist *, unsigned int);
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void __sg_free_table(struct sg_table *, unsigned int, sg_free_fn *);
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void sg_free_table(struct sg_table *);
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int __sg_alloc_table(struct sg_table *, unsigned int, unsigned int, gfp_t,
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sg_alloc_fn *);
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int sg_alloc_table(struct sg_table *, unsigned int, gfp_t);
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size_t sg_copy_from_buffer(struct scatterlist *sgl, unsigned int nents,
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void *buf, size_t buflen);
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size_t sg_copy_to_buffer(struct scatterlist *sgl, unsigned int nents,
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void *buf, size_t buflen);
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/*
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* Maximum number of entries that will be allocated in one piece, if
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* a list larger than this is required then chaining will be utilized.
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*/
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#define SG_MAX_SINGLE_ALLOC (PAGE_SIZE / sizeof(struct scatterlist))
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#endif /* _LINUX_SCATTERLIST_H */
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