checksum.h

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/*
 * Copyright (C) 2004-2006 Atmel Corporation
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */
#ifndef __ASM_AVR32_CHECKSUM_H
#define __ASM_AVR32_CHECKSUM_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
 */
__wsum csum_partial(const void *buff, int len, __wsum sum);

/*
 * the same as csum_partial, but copies from src while it
 * checksums, and handles user-space pointer exceptions correctly, when needed.
 *
 * here even more important to align src and dst on a 32-bit (or even
 * better 64-bit) boundary
 */
__wsum csum_partial_copy_generic(const void *src, void *dst, int len,
                       __wsum sum, int *src_err_ptr,
                       int *dst_err_ptr);

/*
 *  Note: when you get a NULL pointer exception here this means someone
 *  passed in an incorrect kernel address to one of these functions.
 *
 *  If you use these functions directly please don't forget the
 *  access_ok().
 */
static inline
__wsum csum_partial_copy_nocheck(const void *src, void *dst,
                       int len, __wsum sum)
{
    return csum_partial_copy_generic(src, dst, len, sum, NULL, NULL);
}

static inline
__wsum csum_partial_copy_from_user(const void __user *src, void *dst,
                      int len, __wsum sum, int *err_ptr)
{
    return csum_partial_copy_generic((const void __force *)src, dst, len,
                     sum, err_ptr, NULL);
}

/*
 *  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)
{
    unsigned int sum, tmp;

    __asm__ __volatile__(
        "   ld.w    %0, %1++\n"
        "   ld.w    %3, %1++\n"
        "   sub %2, 4\n"
        "   add %0, %3\n"
        "   ld.w    %3, %1++\n"
        "   adc %0, %0, %3\n"
        "   ld.w    %3, %1++\n"
        "   adc %0, %0, %3\n"
        "   acr %0\n"
        "1: ld.w    %3, %1++\n"
        "   add %0, %3\n"
        "   acr %0\n"
        "   sub %2, 1\n"
        "   brne    1b\n"
        "   lsl %3, %0, 16\n"
        "   andl    %0, 0\n"
        "   mov %2, 0xffff\n"
        "   add %0, %3\n"
        "   adc %0, %0, %2\n"
        "   com %0\n"
        "   lsr %0, 16\n"
        : "=r"(sum), "=r"(iph), "=r"(ihl), "=r"(tmp)
        : "1"(iph), "2"(ihl)
        : "memory", "cc");
    return (__force __sum16)sum;
}

/*
 *  Fold a partial checksum
 */

static inline __sum16 csum_fold(__wsum sum)
{
    unsigned int tmp;

    asm("   bfextu  %1, %0, 0, 16\n"
        "   lsr %0, 16\n"
        "   add %0, %1\n"
        "   bfextu  %1, %0, 16, 16\n"
        "   add %0, %1"
        : "=&r"(sum), "=&r"(tmp)
        : "0"(sum));

    return (__force __sum16)~sum;
}

static inline __wsum csum_tcpudp_nofold(__be32 saddr, __be32 daddr,
                           unsigned short len,
                           unsigned short proto,
                           __wsum sum)
{
    asm("   add %0, %1\n"
        "   adc %0, %0, %2\n"
        "   adc %0, %0, %3\n"
        "   acr %0"
        : "=r"(sum)
        : "r"(daddr), "r"(saddr), "r"(len + proto),
          "0"(sum)
        : "cc");

    return sum;
}

/*
 * 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 /* __ASM_AVR32_CHECKSUM_H */