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/* SPDX-License-Identifier: GPL-2.0 */
#ifndef SCATTERLIST_H
#define SCATTERLIST_H
#include <linux/kernel.h>
struct scatterlist {
unsigned long page_link;
unsigned int offset;
unsigned int length;
dma_addr_t dma_address;
};
/* Scatterlist helpers, stolen from linux/scatterlist.h */
#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);
}
/*
* 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)
{
/*
* 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;
}
static inline struct scatterlist *sg_next(struct scatterlist *sg)
{
#ifdef CONFIG_DEBUG_SG
BUG_ON(sg->sg_magic != SG_MAGIC);
#endif
if (sg_is_last(sg))
return NULL;
sg++;
if (unlikely(sg_is_chain(sg)))
sg = sg_chain_ptr(sg);
return sg;
}
static inline void sg_init_table(struct scatterlist *sgl, unsigned int nents)
{
memset(sgl, 0, sizeof(*sgl) * nents);
#ifdef CONFIG_DEBUG_SG
{
unsigned int i;
for (i = 0; i < nents; i++)
sgl[i].sg_magic = SG_MAGIC;
}
#endif
sg_mark_end(&sgl[nents - 1]);
}
static inline dma_addr_t sg_phys(struct scatterlist *sg)
{
return page_to_phys(sg_page(sg)) + sg->offset;
}
static inline void sg_set_buf(struct scatterlist *sg, const void *buf,
unsigned int buflen)
{
sg_set_page(sg, virt_to_page(buf), buflen, offset_in_page(buf));
}
static inline void sg_init_one(struct scatterlist *sg,
const void *buf, unsigned int buflen)
{
sg_init_table(sg, 1);
sg_set_buf(sg, buf, buflen);
}
#endif /* SCATTERLIST_H */
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