/* SPDX-License-Identifier: GPL-2.0-or-later */

  /*

   * Cryptographic scatter and gather helpers.

   *
   * Copyright (c) 2002 James Morris <jmorris@intercode.com.au>
   * Copyright (c) 2002 Adam J. Richter <adam@yggdrasil.com>
   * Copyright (c) 2004 Jean-Luc Cooke <jlcooke@certainkey.com>

   * Copyright (c) 2007 Herbert Xu <herbert@gondor.apana.org.au>

   */
  
  #ifndef _CRYPTO_SCATTERWALK_H
  #define _CRYPTO_SCATTERWALK_H

  #include <crypto/algapi.h>

  #include <linux/highmem.h>
  #include <linux/kernel.h>

  #include <linux/scatterlist.h>

  static inline void scatterwalk_crypto_chain(struct scatterlist *head,

  					    struct scatterlist *sg, int num)

  {

  	if (sg)

  		sg_chain(head, num, sg);

  	else
  		sg_mark_end(head);
  }

  static inline unsigned int scatterwalk_pagelen(struct scatter_walk *walk)
  {
  	unsigned int len = walk->sg->offset + walk->sg->length - walk->offset;
  	unsigned int len_this_page = offset_in_page(~walk->offset) + 1;
  	return len_this_page > len ? len : len_this_page;

  }

  static inline unsigned int scatterwalk_clamp(struct scatter_walk *walk,
  					     unsigned int nbytes)

  {

  	unsigned int len_this_page = scatterwalk_pagelen(walk);
  	return nbytes > len_this_page ? len_this_page : nbytes;

  }
  
  static inline void scatterwalk_advance(struct scatter_walk *walk,
  				       unsigned int nbytes)
  {

  	walk->offset += nbytes;

  }

  static inline unsigned int scatterwalk_aligned(struct scatter_walk *walk,
  					       unsigned int alignmask)
  {
  	return !(walk->offset & alignmask);
  }

  static inline struct page *scatterwalk_page(struct scatter_walk *walk)
  {

  	return sg_page(walk->sg) + (walk->offset >> PAGE_SHIFT);

  }

  static inline void scatterwalk_unmap(void *vaddr)

  {

  	kunmap_atomic(vaddr);

  }

  static inline void scatterwalk_start(struct scatter_walk *walk,
  				     struct scatterlist *sg)
  {
  	walk->sg = sg;
  	walk->offset = sg->offset;
  }
  
  static inline void *scatterwalk_map(struct scatter_walk *walk)
  {
  	return kmap_atomic(scatterwalk_page(walk)) +
  	       offset_in_page(walk->offset);
  }
  
  static inline void scatterwalk_pagedone(struct scatter_walk *walk, int out,
  					unsigned int more)
  {
  	if (out) {
  		struct page *page;
  
  		page = sg_page(walk->sg) + ((walk->offset - 1) >> PAGE_SHIFT);
  		/* Test ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE first as
  		 * PageSlab cannot be optimised away per se due to
  		 * use of volatile pointer.
  		 */
  		if (ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE && !PageSlab(page))
  			flush_dcache_page(page);
  	}
  
  	if (more && walk->offset >= walk->sg->offset + walk->sg->length)
  		scatterwalk_start(walk, sg_next(walk->sg));
  }
  
  static inline void scatterwalk_done(struct scatter_walk *walk, int out,
  				    int more)
  {
  	if (!more || walk->offset >= walk->sg->offset + walk->sg->length ||
  	    !(walk->offset & (PAGE_SIZE - 1)))
  		scatterwalk_pagedone(walk, out, more);
  }

  void scatterwalk_copychunks(void *buf, struct scatter_walk *walk,
  			    size_t nbytes, int out);

  void *scatterwalk_map(struct scatter_walk *walk);

  void scatterwalk_map_and_copy(void *buf, struct scatterlist *sg,
  			      unsigned int start, unsigned int nbytes, int out);

  struct scatterlist *scatterwalk_ffwd(struct scatterlist dst[2],
  				     struct scatterlist *src,
  				     unsigned int len);

  #endif  /* _CRYPTO_SCATTERWALK_H */