/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _LINUX_SCATTERLIST_H
#define _LINUX_SCATTERLIST_H

#include <linux/string.h>
#include <linux/types.h>
#include <linux/bug.h>
#include <linux/mm.h>
#include <asm/io.h>

struct scatterlist {
#ifdef CONFIG_DEBUG_SG
        unsigned long   sg_magic;
#endif
        unsigned long   page_link;
        unsigned int    offset;
        unsigned int    length;
        dma_addr_t      dma_address;
#ifdef CONFIG_NEED_SG_DMA_LENGTH
        unsigned int    dma_length;
#endif
};

/*
 * These macros should be used after a dma_map_sg call has been done
 * to get bus addresses of each of the SG entries and their lengths.
 * You should only work with the number of sg entries dma_map_sg
 * returns, or alternatively stop on the first sg_dma_len(sg) which
 * is 0.
 */
#define sg_dma_address(sg)      ((sg)->dma_address)

#ifdef CONFIG_NEED_SG_DMA_LENGTH
#define sg_dma_len(sg)          ((sg)->dma_length)
#else
#define sg_dma_len(sg)          ((sg)->length)
#endif

struct sg_table {
        struct scatterlist *sgl;        /* the list */
        unsigned int nents;             /* number of mapped entries */
        unsigned int orig_nents;        /* original size of list */
};

/*
 * Notes on SG table design.
 *
 * We use the unsigned long page_link field in the scatterlist struct 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

/*
 * 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_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);
}

/**
 * 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)
{
#ifdef CONFIG_DEBUG_SG
        BUG_ON(!virt_addr_valid(buf));
#endif
        sg_set_page(sg, virt_to_page(buf), buflen, offset_in_page(buf));
}

/*
 * 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;
}

/**
 * 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 dma_addr_t 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;
}

int sg_nents(struct scatterlist *sg);
int sg_nents_for_len(struct scatterlist *sg, u64 len);
struct scatterlist *sg_next(struct scatterlist *);
struct scatterlist *sg_last(struct scatterlist *s, unsigned int);
void sg_init_table(struct scatterlist *, unsigned int);
void sg_init_one(struct scatterlist *, const void *, unsigned int);
int sg_split(struct scatterlist *in, const int in_mapped_nents,
             const off_t skip, const int nb_splits,
             const size_t *split_sizes,
             struct scatterlist **out, int *out_mapped_nents,
             gfp_t gfp_mask);

typedef struct scatterlist *(sg_alloc_fn)(unsigned int, gfp_t);
typedef void (sg_free_fn)(struct scatterlist *, unsigned int);

void __sg_free_table(struct sg_table *, unsigned int, bool, sg_free_fn *);
void sg_free_table(struct sg_table *);
int __sg_alloc_table(struct sg_table *, unsigned int, unsigned int,
                     struct scatterlist *, gfp_t, sg_alloc_fn *);
int sg_alloc_table(struct sg_table *, unsigned int, gfp_t);
int sg_alloc_table_from_pages(struct sg_table *sgt,
        struct page **pages, unsigned int n_pages,
        unsigned long offset, unsigned long size,
        gfp_t gfp_mask);

size_t sg_copy_buffer(struct scatterlist *sgl, unsigned int nents, void *buf,
                      size_t buflen, off_t skip, bool to_buffer);

size_t sg_copy_from_buffer(struct scatterlist *sgl, unsigned int nents,
                           const void *buf, size_t buflen);
size_t sg_copy_to_buffer(struct scatterlist *sgl, unsigned int nents,
                         void *buf, size_t buflen);

size_t sg_pcopy_from_buffer(struct scatterlist *sgl, unsigned int nents,
                            const void *buf, size_t buflen, off_t skip);
size_t sg_pcopy_to_buffer(struct scatterlist *sgl, unsigned int nents,
                          void *buf, size_t buflen, off_t skip);
size_t sg_zero_buffer(struct scatterlist *sgl, unsigned int nents,
                       size_t buflen, off_t skip);

/*
 * Maximum number of entries that will be allocated in one piece, if
 * a list larger than this is required then chaining will be utilized.
 */
#define SG_MAX_SINGLE_ALLOC             (PAGE_SIZE / sizeof(struct scatterlist))

/*
 * The maximum number of SG segments that we will put inside a
 * scatterlist (unless chaining is used). Should ideally fit inside a
 * single page, to avoid a higher order allocation.  We could define this
 * to SG_MAX_SINGLE_ALLOC to pack correctly at the highest order.  The
 * minimum value is 32
 */
#define SG_CHUNK_SIZE   128

/*
 * Like SG_CHUNK_SIZE, but for archs that have sg chaining. This limit
 * is totally arbitrary, a setting of 2048 will get you at least 8mb ios.
 */
#ifdef CONFIG_ARCH_HAS_SG_CHAIN
#define SG_MAX_SEGMENTS 2048
#else
#define SG_MAX_SEGMENTS SG_CHUNK_SIZE
#endif

#ifdef CONFIG_SG_POOL
void sg_free_table_chained(struct sg_table *table, bool first_chunk);
int sg_alloc_table_chained(struct sg_table *table, int nents,
                           struct scatterlist *first_chunk);
#endif

/*
 * sg page iterator
 *
 * Iterates over sg entries page-by-page.  On each successful iteration,
 * you can call sg_page_iter_page(@piter) and sg_page_iter_dma_address(@piter)
 * to get the current page and its dma address. @piter->sg will point to the
 * sg holding this page and @piter->sg_pgoffset to the page's page offset
 * within the sg. The iteration will stop either when a maximum number of sg
 * entries was reached or a terminating sg (sg_last(sg) == true) was reached.
 */
struct sg_page_iter {
        struct scatterlist      *sg;            /* sg holding the page */
        unsigned int            sg_pgoffset;    /* page offset within the sg */

        /* these are internal states, keep away */
        unsigned int            __nents;        /* remaining sg entries */
        int                     __pg_advance;   /* nr pages to advance at the
                                                 * next step */
};

bool __sg_page_iter_next(struct sg_page_iter *piter);
void __sg_page_iter_start(struct sg_page_iter *piter,
                          struct scatterlist *sglist, unsigned int nents,
                          unsigned long pgoffset);
/**
 * sg_page_iter_page - get the current page held by the page iterator
 * @piter:      page iterator holding the page
 */
static inline struct page *sg_page_iter_page(struct sg_page_iter *piter)
{
        return nth_page(sg_page(piter->sg), piter->sg_pgoffset);
}

/**
 * sg_page_iter_dma_address - get the dma address of the current page held by
 * the page iterator.
 * @piter:      page iterator holding the page
 */
static inline dma_addr_t sg_page_iter_dma_address(struct sg_page_iter *piter)
{
        return sg_dma_address(piter->sg) + (piter->sg_pgoffset << PAGE_SHIFT);
}

/**
 * for_each_sg_page - iterate over the pages of the given sg list
 * @sglist:     sglist to iterate over
 * @piter:      page iterator to hold current page, sg, sg_pgoffset
 * @nents:      maximum number of sg entries to iterate over
 * @pgoffset:   starting page offset
 */
#define for_each_sg_page(sglist, piter, nents, pgoffset)                   \
        for (__sg_page_iter_start((piter), (sglist), (nents), (pgoffset)); \
             __sg_page_iter_next(piter);)

/*
 * Mapping sg iterator
 *
 * Iterates over sg entries mapping page-by-page.  On each successful
 * iteration, @miter->page points to the mapped page and
 * @miter->length bytes of data can be accessed at @miter->addr.  As
 * long as an interation is enclosed between start and stop, the user
 * is free to choose control structure and when to stop.
 *
 * @miter->consumed is set to @miter->length on each iteration.  It
 * can be adjusted if the user can't consume all the bytes in one go.
 * Also, a stopped iteration can be resumed by calling next on it.
 * This is useful when iteration needs to release all resources and
 * continue later (e.g. at the next interrupt).
 */

#define SG_MITER_ATOMIC         (1 << 0)         /* use kmap_atomic */
#define SG_MITER_TO_SG          (1 << 1)        /* flush back to phys on unmap */
#define SG_MITER_FROM_SG        (1 << 2)        /* nop */

struct sg_mapping_iter {
        /* the following three fields can be accessed directly */
        struct page             *page;          /* currently mapped page */
        void                    *addr;          /* pointer to the mapped area */
        size_t                  length;         /* length of the mapped area */
        size_t                  consumed;       /* number of consumed bytes */
        struct sg_page_iter     piter;          /* page iterator */

        /* these are internal states, keep away */
        unsigned int            __offset;       /* offset within page */
        unsigned int            __remaining;    /* remaining bytes on page */
        unsigned int            __flags;
};

void sg_miter_start(struct sg_mapping_iter *miter, struct scatterlist *sgl,
                    unsigned int nents, unsigned int flags);
bool sg_miter_skip(struct sg_mapping_iter *miter, off_t offset);
bool sg_miter_next(struct sg_mapping_iter *miter);
void sg_miter_stop(struct sg_mapping_iter *miter);

#endif /* _LINUX_SCATTERLIST_H */