#ifndef _S390_CHECKSUM_H
  #define _S390_CHECKSUM_H
  
  /*
   *  include/asm-s390/checksum.h
   *    S390 fast network checksum routines
   *    see also arch/S390/lib/checksum.c
   *
   *  S390 version
   *    Copyright (C) 1999 IBM Deutschland Entwicklung GmbH, IBM Corporation
   *    Author(s): Ulrich Hild        (first version)
   *               Martin Schwidefsky (heavily optimized CKSM version)
   *               D.J. Barrow        (third attempt) 
   */
  
  #include <asm/uaccess.h>
  
  /*
   * computes the checksum of a memory block at buff, length len,
   * and adds in "sum" (32-bit)
   *
   * returns a 32-bit number suitable for feeding into itself
   * or csum_tcpudp_magic
   *
   * this function must be called with even lengths, except
   * for the last fragment, which may be odd
   *
   * it's best to have buff aligned on a 32-bit boundary
   */

  static inline __wsum
  csum_partial(const void *buff, int len, __wsum sum)

  {

  	register unsigned long reg2 asm("2") = (unsigned long) buff;
  	register unsigned long reg3 asm("3") = (unsigned long) len;

  	asm volatile(
  		"0:	cksm	%0,%1
  "	/* do checksum on longs */
  		"	jo	0b
  "
  		: "+d" (sum), "+d" (reg2), "+d" (reg3) : : "cc", "memory");

  	return sum;
  }
  
  /*
   * the same as csum_partial_copy, but copies from user space.
   *
   * here even more important to align src and dst on a 32-bit (or even
   * better 64-bit) boundary
   *
   * Copy from userspace and compute checksum.  If we catch an exception
   * then zero the rest of the buffer.
   */

  static inline __wsum
  csum_partial_copy_from_user(const void __user *src, void *dst,
                                            int len, __wsum sum,

                                            int *err_ptr)
  {
  	int missing;
  
  	missing = copy_from_user(dst, src, len);
  	if (missing) {
  		memset(dst + len - missing, 0, missing);
  		*err_ptr = -EFAULT;
  	}
  		
  	return csum_partial(dst, len, sum);
  }

  static inline __wsum
  csum_partial_copy_nocheck (const void *src, void *dst, int len, __wsum sum)

  {
          memcpy(dst,src,len);

  	return csum_partial(dst, len, sum);

  }
  
  /*
   *      Fold a partial checksum without adding pseudo headers
   */

  static inline __sum16 csum_fold(__wsum sum)

  {
  #ifndef __s390x__
  	register_pair rp;

  	asm volatile(
  		"	slr	%N1,%N1
  "	/* %0 = H L */
  		"	lr	%1,%0
  "	/* %0 = H L, %1 = H L 0 0 */
  		"	srdl	%1,16
  "	/* %0 = H L, %1 = 0 H L 0 */
  		"	alr	%1,%N1
  "	/* %0 = H L, %1 = L H L 0 */
  		"	alr	%0,%1
  "	/* %0 = H+L+C L+H */
  		"	srl	%0,16
  "	/* %0 = H+L+C */
  		: "+&d" (sum), "=d" (rp) : : "cc");

  #else /* __s390x__ */

  	asm volatile(
  		"	sr	3,3
  "		/* %0 = H*65536 + L */
  		"	lr	2,%0
  "		/* %0 = H L, 2/3 = H L / 0 0 */
  		"	srdl	2,16
  "		/* %0 = H L, 2/3 = 0 H / L 0 */
  		"	alr	2,3
  "		/* %0 = H L, 2/3 = L H / L 0 */
  		"	alr	%0,2
  "		/* %0 = H+L+C L+H */
  		"	srl	%0,16
  "	/* %0 = H+L+C */

  		: "+&d" (sum) : : "cc", "2", "3");
  #endif /* __s390x__ */

  	return (__force __sum16) ~sum;

  }
  
  /*
   *	This is a version of ip_compute_csum() optimized for IP headers,
   *	which always checksum on 4 octet boundaries.
   *
   */

  static inline __sum16 ip_fast_csum(const void *iph, unsigned int ihl)

  {

  	return csum_fold(csum_partial(iph, ihl*4, 0));

  }
  
  /*
   * computes the checksum of the TCP/UDP pseudo-header
   * returns a 32-bit checksum
   */

  static inline __wsum
  csum_tcpudp_nofold(__be32 saddr, __be32 daddr,

                     unsigned short len, unsigned short proto,

                     __wsum sum)

  {

  	__u32 csum = (__force __u32)sum;
  
  	csum += (__force __u32)saddr;
  	if (csum < (__force __u32)saddr)
  		csum++;
  
  	csum += (__force __u32)daddr;
  	if (csum < (__force __u32)daddr)
  		csum++;
  
  	csum += len + proto;
  	if (csum < len + proto)
  		csum++;
  
  	return (__force __wsum)csum;

  }
  
  /*
   * computes the checksum of the TCP/UDP pseudo-header
   * returns a 16-bit checksum, already complemented
   */

  static inline __sum16
  csum_tcpudp_magic(__be32 saddr, __be32 daddr,

                    unsigned short len, unsigned short proto,

                    __wsum sum)

  {
  	return csum_fold(csum_tcpudp_nofold(saddr,daddr,len,proto,sum));
  }
  
  /*
   * this routine is used for miscellaneous IP-like checksums, mainly
   * in icmp.c
   */

  static inline __sum16 ip_compute_csum(const void *buff, int len)

  {
  	return csum_fold(csum_partial(buff, len, 0));
  }
  
  #endif /* _S390_CHECKSUM_H */