include/asm-cris/arch-v32/checksum.h

   1 #ifndef _ASM_CRIS_ARCH_CHECKSUM_H
   2 #define _ASM_CRIS_ARCH_CHECKSUM_H
   3
   4 /*
   5  * Check values used in TCP/UDP headers.
   6  *
   7  * The gain of doing this in assembler instead of C, is that C doesn't
   8  * generate carry-additions for the 32-bit components of the
   9  * checksum. Which means it would be necessary to split all those into
  10  * 16-bit components and then add.
  11  */
  12 extern inline unsigned int
  13 csum_tcpudp_nofold(unsigned long saddr, unsigned long daddr,
  14                    unsigned short len, unsigned short proto, unsigned int sum)
  15 {
  16         int res;
  17
  18         __asm__ __volatile__ ("add.d %2, %0\n\t"
  19                               "addc %3, %0\n\t"
  20                               "addc %4, %0\n\t"
  21                               "addc 0, %0\n\t"
  22                               : "=r" (res)
  23                               : "0" (sum), "r" (daddr), "r" (saddr), \
  24                               "r" ((ntohs(len) << 16) + (proto << 8)));
  25
  26         return res;
  27 }
  28
  29 #endif /* _ASM_CRIS_ARCH_CHECKSUM_H */