#ifndef _LINUX_SCATTERLIST_H
#define _LINUX_SCATTERLIST_H
#include <asm/scatterlist.h>
#include <linux/mm.h>
#include <linux/string.h>
#include <asm/io.h>
/*
* Notes on SG table design.
*
* Architectures must provide an unsigned long page_link field in the
* scatterlist struct. We use that to place the page pointer AND encode
* information about the sg table as well. The two lower bits are reserved
* for this information.
*
* If bit 0 is set, then the page_link contains a pointer to the next sg
* table list. Otherwise the next entry is at sg + 1.
*
* If bit 1 is set, then this sg entry is the last element in a list.
*
* See sg_next().
*
*/
#define SG_MAGIC 0x87654321
/**
* sg_set_page - Set sg entry to point at given page
* @sg: SG entry
* @page: The 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 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);
#endif
sg->page_link = page_link | (unsigned long) page;
}
#define sg_page(sg) ((struct page *) ((sg)->page_link & ~0x3))
/**
* sg_set_buf - Set sg entry to point at given data
* @sg: SG entry
* @buf: Data
* @buflen: Data length
*
**/
static inline void sg_set_buf(struct scatterlist *sg, const void *buf,
unsigned int buflen)
{
sg_set_page(sg, virt_to_page(buf));
sg->offset = offset_in_page(buf);
sg->length = buflen;
}
/*
* We overload the LSB of the page pointer to indicate whether it's
* a valid sg entry, or whether it points to the start of a new scatterlist.
* Those low bits are there for everyone! (thanks mason :-)
*/
#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_next - return the next scatterlist entry in a list
* @sg: The current sg entry
*
* Description:
* Usually the next entry will be @sg@ + 1, but if this sg element is part
* of a chained scatterlist, it could jump to the start of a new
* scatterlist array.
*
**/
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;
}
/*
* 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_last - return the last scatterlist entry in a list
* @sgl: First entry in the scatterlist
* @nents: Number of entries in the scatterlist
*
* Description:
* Should only be used casually, it (currently) scan the entire list
* to get the last entry.
*
* Note that the @sgl@ pointer passed in need not be the first one,
* the important bit is that @nents@ denotes the number of entries that
* exist from @sgl@.
*
**/
static inline struct scatterlist *sg_last(struct scatterlist *sgl,
unsigned int nents)
{
#ifndef ARCH_HAS_SG_CHAIN
struct scatterlist *ret = &sgl[nents - 1];
#else
struct scatterlist *sg, *ret = NULL;
int i;
for_each_sg(sgl, sg, nents, i)
ret = sg;
#endif
#ifdef CONFIG_DEBUG_SG
BUG_ON(sgl[0].sg_magic != SG_MAGIC);
BUG_ON(!sg_is_last(ret));
#endif
return ret;
}
/**
* 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)
{
#ifndef ARCH_HAS_SG_CHAIN
BUG();
#endif
prv[prv_nents - 1].page_link = (unsigned long) sgl | 0x01;
}
/**
* sg_mark_end - Mark the end of the scatterlist
* @sgl: Scatterlist
* @nents: Number of entries in sgl
*
* Description:
* Marks the last entry as the termination point for sg_next()
*
**/
static inline void sg_mark_end(struct scatterlist *sgl, unsigned int nents)
{
sgl[nents - 1].page_link = 0x02;
}
static inline void __sg_mark_end(struct scatterlist *sg)
{
sg->page_link |= 0x02;
}
/**
* sg_init_one - Initialize a single entry sg list
* @sg: SG entry
* @buf: Virtual address for IO
* @buflen: IO length
*
* Notes:
* This should not be used on a single entry that is part of a larger
* table. Use sg_init_table() for that.
*
**/
static inline void sg_init_one(struct scatterlist *sg, const void *buf,
unsigned int buflen)
{
memset(sg, 0, sizeof(*sg));
#ifdef CONFIG_DEBUG_SG
sg->sg_magic = SG_MAGIC;
#endif
sg_mark_end(sg, 1);
sg_set_buf(sg, buf, buflen);
}
/**
* sg_init_table - Initialize SG table
* @sgl: The SG table
* @nents: Number of entries in table
*
* Notes:
* If this is part of a chained sg table, sg_mark_end() should be
* used only on the last table part.
*
**/
static inline void sg_init_table(struct scatterlist *sgl, unsigned int nents)
{
memset(sgl, 0, sizeof(*sgl) * nents);
sg_mark_end(sgl, nents);
#ifdef CONFIG_DEBUG_SG
{
int i;
for (i = 0; i < nents; i++)
sgl[i].sg_magic = SG_MAGIC;
}
#endif
}
/**
* sg_phys - Return physical address of an sg entry
* @sg: SG entry
*
* Description:
* This calls page_to_phys() on the page in this sg entry, and adds the
* sg offset. The caller must know that it is legal to call page_to_phys()
* on the sg page.
*
**/
static inline unsigned long sg_phys(struct scatterlist *sg)
{
return page_to_phys(sg_page(sg)) + sg->offset;
}
/**
* sg_virt - Return virtual address of an sg entry
* @sg: SG entry
*
* Description:
* This calls page_address() on the page in this sg entry, and adds the
* sg offset. The caller must know that the sg page has a valid virtual
* mapping.
*
**/
static inline void *sg_virt(struct scatterlist *sg)
{
return page_address(sg_page(sg)) + sg->offset;
}
#endif /* _LINUX_SCATTERLIST_H */
