/*
   * T10 Data Integrity Field CRC16 calculation
   *
   * Copyright (c) 2007 Oracle Corporation.  All rights reserved.
   * Written by Martin K. Petersen <martin.petersen@oracle.com>
   *
   * This source code is licensed under the GNU General Public License,
   * Version 2. See the file COPYING for more details.
   */
  
  #include <linux/types.h>
  #include <linux/module.h>
  #include <linux/crc-t10dif.h>

  #include <linux/err.h>
  #include <linux/init.h>
  #include <crypto/hash.h>

  #include <linux/static_key.h>

  static struct crypto_shash *crct10dif_tfm;

  static struct static_key crct10dif_fallback __read_mostly;

  
  __u16 crc_t10dif(const unsigned char *buffer, size_t len)
  {

  	struct {
  		struct shash_desc shash;
  		char ctx[2];
  	} desc;
  	int err;

  	if (static_key_false(&crct10dif_fallback))
  		return crc_t10dif_generic(0, buffer, len);

  	desc.shash.tfm = crct10dif_tfm;
  	desc.shash.flags = 0;
  	*(__u16 *)desc.ctx = 0;

  	err = crypto_shash_update(&desc.shash, buffer, len);
  	BUG_ON(err);

  	return *(__u16 *)desc.ctx;

  }
  EXPORT_SYMBOL(crc_t10dif);

  static int __init crc_t10dif_mod_init(void)
  {
  	crct10dif_tfm = crypto_alloc_shash("crct10dif", 0, 0);

  	if (IS_ERR(crct10dif_tfm)) {
  		static_key_slow_inc(&crct10dif_fallback);
  		crct10dif_tfm = NULL;
  	}
  	return 0;

  }
  
  static void __exit crc_t10dif_mod_fini(void)
  {
  	crypto_free_shash(crct10dif_tfm);
  }
  
  module_init(crc_t10dif_mod_init);
  module_exit(crc_t10dif_mod_fini);

  MODULE_DESCRIPTION("T10 DIF CRC calculation");
  MODULE_LICENSE("GPL");

  MODULE_SOFTDEP("pre: crct10dif");