release/src-rt-6.x.4708/linux/linux-2.6.36/drivers/staging/vt6655/tether.c

   1 /*
   2  * Copyright (c) 2003 VIA Networking, Inc. All rights reserved.
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License as published by
   6  * the Free Software Foundation; either version 2 of the License, or
   7  * (at your option) any later version.
   8  *
   9  * This program is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  * GNU General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License along
  15  * with this program; if not, write to the Free Software Foundation, Inc.,
  16  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  17  *
  18  *
  19  * File: tether.c
  20  *
  21  * Purpose:
  22  *
  23  * Author: Tevin Chen
  24  *
  25  * Date: May 21, 1996
  26  *
  27  * Functions:
  28  *      ETHbyGetHashIndexByCrc32 - Caculate multicast hash value by CRC32
  29  *      ETHbIsBufferCrc32Ok - Check CRC value of the buffer if Ok or not
  30  *
  31  * Revision History:
  32  *
  33  */
  34
  35 #include "device.h"
  36 #include "tmacro.h"
  37 #include "tcrc.h"
  38 #include "tether.h"
  39
  40 /*---------------------  Static Definitions -------------------------*/
  41
  42 /*---------------------  Static Classes  ----------------------------*/
  43
  44 /*---------------------  Static Variables  --------------------------*/
  45
  46 /*---------------------  Static Functions  --------------------------*/
  47
  48 /*---------------------  Export Variables  --------------------------*/
  49
  50
  51
  52 /*
  53  * Description: Caculate multicast hash value by CRC32
  54  *
  55  * Parameters:
  56  *  In:
  57  *              pbyMultiAddr    - Multicast Address
  58  *  Out:
  59  *      none
  60  *
  61  * Return Value: Hash value
  62  *
  63  */
  64 unsigned char ETHbyGetHashIndexByCrc32 (unsigned char *pbyMultiAddr)
  65 {
  66     int     ii;
  67     unsigned char byTmpHash;
  68     unsigned char byHash = 0;
  69
  70     // get the least 6-bits from CRC generator
  71     byTmpHash = (unsigned char)(CRCdwCrc32(pbyMultiAddr, ETH_ALEN,
  72             0xFFFFFFFFL) & 0x3F);
  73     // reverse most bit to least bit
  74     for (ii = 0; ii < (sizeof(byTmpHash) * 8); ii++) {
  75         byHash <<= 1;
  76         if (byTmpHash & 0x01)
  77             byHash |= 1;
  78         byTmpHash >>= 1;
  79     }
  80
  81     // adjust 6-bits to the right most
  82     return (byHash >> 2);
  83 }
  84
  85
  86 /*
  87  * Description: Check CRC value of the buffer if Ok or not
  88  *
  89  * Parameters:
  90  *  In:
  91  *              pbyBuffer           - pointer of buffer (normally is rx buffer)
  92  *              cbFrameLength   - length of buffer, including CRC portion
  93  *  Out:
  94  *      none
  95  *
  96  * Return Value: true if ok; false if error.
  97  *
  98  */
  99 bool ETHbIsBufferCrc32Ok (unsigned char *pbyBuffer, unsigned int cbFrameLength)
 100 {
 101     unsigned long dwCRC;
 102
 103     dwCRC = CRCdwGetCrc32(pbyBuffer, cbFrameLength - 4);
 104     if (cpu_to_le32(*((unsigned long *)(pbyBuffer + cbFrameLength - 4))) != dwCRC) {
 105         return false;
 106     }
 107     return true;
 108 }