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 - Calculate 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  * Description: Calculate multicast hash value by CRC32
  52  *
  53  * Parameters:
  54  *  In:
  55  *              pbyMultiAddr    - Multicast Address
  56  *  Out:
  57  *      none
  58  *
  59  * Return Value: Hash value
  60  *
  61  */
  62 unsigned char ETHbyGetHashIndexByCrc32(unsigned char *pbyMultiAddr)
  63 {
  64         int     ii;
  65         unsigned char byTmpHash;
  66         unsigned char byHash = 0;
  67
  68         // get the least 6-bits from CRC generator
  69         byTmpHash = (unsigned char)(CRCdwCrc32(pbyMultiAddr, ETH_ALEN,
  70                                                0xFFFFFFFFL) & 0x3F);
  71         // reverse most bit to least bit
  72         for (ii = 0; ii < (sizeof(byTmpHash) * 8); ii++) {
  73                 byHash <<= 1;
  74                 if (byTmpHash & 0x01)
  75                         byHash |= 1;
  76                 byTmpHash >>= 1;
  77         }
  78
  79         // adjust 6-bits to the right most
  80         return byHash >> 2;
  81 }
  82
  83 /*
  84  * Description: Check CRC value of the buffer if Ok or not
  85  *
  86  * Parameters:
  87  *  In:
  88  *              pbyBuffer           - pointer of buffer (normally is rx buffer)
  89  *              cbFrameLength   - length of buffer, including CRC portion
  90  *  Out:
  91  *      none
  92  *
  93  * Return Value: true if ok; false if error.
  94  *
  95  */
  96 bool ETHbIsBufferCrc32Ok(unsigned char *pbyBuffer, unsigned int cbFrameLength)
  97 {
  98         unsigned long dwCRC;
  99
 100         dwCRC = CRCdwGetCrc32(pbyBuffer, cbFrameLength - 4);
 101         if (cpu_to_le32(*((unsigned long *)(pbyBuffer + cbFrameLength - 4))) != dwCRC)
 102                 return false;
 103
 104         return true;
 105 }