drivers/isdn/tpam/tpam_crcpc.c

   1 /* $Id: tpam_crcpc.c,v 1.1.2.2 2001/09/23 22:25:03 kai Exp $
   2  *
   3  * Turbo PAM ISDN driver for Linux. (Kernel Driver - CRC encoding)
   4  *
   5  * Copyright 1998-2000 AUVERTECH Télécom
   6  * Copyright 2001 Stelian Pop <stelian.pop@fr.alcove.com>, Alcôve
   7  *
   8  * This software may be used and distributed according to the terms
   9  * of the GNU General Public License, incorporated herein by reference.
  10  *
  11  * For all support questions please contact: <support@auvertech.fr>
  12  *
  13  */
  14
  15 /*+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
  16
  17 Module Name:
  18
  19     crcpc.c
  20
  21 Abstract:
  22
  23     Modem HDLC coding
  24     Software HDLC coding / decoding
  25
  26 Revision History:
  27
  28 ---------------------------------------------------------------------------*/
  29
  30 #include "tpam.h"
  31
  32 #define  HDLC_CTRL_CHAR_CMPL_MASK       0x20    /* HDLC control character complement mask */
  33 #define  HDLC_FLAG                      0x7E    /* HDLC flag */
  34 #define  HDLC_CTRL_ESC                  0x7D    /* HDLC control escapr character */
  35 #define  HDLC_LIKE_FCS_INIT_VAL         0xFFFF  /* FCS initial value (0xFFFF for new equipment or 0) */
  36 #define  HDLC_FCS_OK                    0xF0B8  /* This value is the only valid value of FCS */
  37
  38 #define TRUE    1
  39 #define FALSE   0
  40
  41 static u16 t_ap_hdlc_like_fcs [256] = {
  42         0x0000, 0x1189, 0x2312, 0x329b, 0x4624, 0x57ad, 0x6536, 0x74bf,
  43         0x8c48, 0x9dc1, 0xaf5a, 0xbed3, 0xca6c, 0xdbe5, 0xe97e, 0xf8f7,
  44         0x1081, 0x0108, 0x3393, 0x221a, 0x56a5, 0x472c, 0x75b7, 0x643e,
  45         0x9cc9, 0x8d40, 0xbfdb, 0xae52, 0xdaed, 0xcb64, 0xf9ff, 0xe876,
  46         0x2102, 0x308b, 0x0210, 0x1399, 0x6726, 0x76af, 0x4434, 0x55bd,
  47         0xad4a, 0xbcc3, 0x8e58, 0x9fd1, 0xeb6e, 0xfae7, 0xc87c, 0xd9f5,
  48         0x3183, 0x200a, 0x1291, 0x0318, 0x77a7, 0x662e, 0x54b5, 0x453c,
  49         0xbdcb, 0xac42, 0x9ed9, 0x8f50, 0xfbef, 0xea66, 0xd8fd, 0xc974,
  50         0x4204, 0x538d, 0x6116, 0x709f, 0x0420, 0x15a9, 0x2732, 0x36bb,
  51         0xce4c, 0xdfc5, 0xed5e, 0xfcd7, 0x8868, 0x99e1, 0xab7a, 0xbaf3,
  52         0x5285, 0x430c, 0x7197, 0x601e, 0x14a1, 0x0528, 0x37b3, 0x263a,
  53         0xdecd, 0xcf44, 0xfddf, 0xec56, 0x98e9, 0x8960, 0xbbfb, 0xaa72,
  54         0x6306, 0x728f, 0x4014, 0x519d, 0x2522, 0x34ab, 0x0630, 0x17b9,
  55         0xef4e, 0xfec7, 0xcc5c, 0xddd5, 0xa96a, 0xb8e3, 0x8a78, 0x9bf1,
  56         0x7387, 0x620e, 0x5095, 0x411c, 0x35a3, 0x242a, 0x16b1, 0x0738,
  57         0xffcf, 0xee46, 0xdcdd, 0xcd54, 0xb9eb, 0xa862, 0x9af9, 0x8b70,
  58         0x8408, 0x9581, 0xa71a, 0xb693, 0xc22c, 0xd3a5, 0xe13e, 0xf0b7,
  59         0x0840, 0x19c9, 0x2b52, 0x3adb, 0x4e64, 0x5fed, 0x6d76, 0x7cff,
  60         0x9489, 0x8500, 0xb79b, 0xa612, 0xd2ad, 0xc324, 0xf1bf, 0xe036,
  61         0x18c1, 0x0948, 0x3bd3, 0x2a5a, 0x5ee5, 0x4f6c, 0x7df7, 0x6c7e,
  62         0xa50a, 0xb483, 0x8618, 0x9791, 0xe32e, 0xf2a7, 0xc03c, 0xd1b5,
  63         0x2942, 0x38cb, 0x0a50, 0x1bd9, 0x6f66, 0x7eef, 0x4c74, 0x5dfd,
  64         0xb58b, 0xa402, 0x9699, 0x8710, 0xf3af, 0xe226, 0xd0bd, 0xc134,
  65         0x39c3, 0x284a, 0x1ad1, 0x0b58, 0x7fe7, 0x6e6e, 0x5cf5, 0x4d7c,
  66         0xc60c, 0xd785, 0xe51e, 0xf497, 0x8028, 0x91a1, 0xa33a, 0xb2b3,
  67         0x4a44, 0x5bcd, 0x6956, 0x78df, 0x0c60, 0x1de9, 0x2f72, 0x3efb,
  68         0xd68d, 0xc704, 0xf59f, 0xe416, 0x90a9, 0x8120, 0xb3bb, 0xa232,
  69         0x5ac5, 0x4b4c, 0x79d7, 0x685e, 0x1ce1, 0x0d68, 0x3ff3, 0x2e7a,
  70         0xe70e, 0xf687, 0xc41c, 0xd595, 0xa12a, 0xb0a3, 0x8238, 0x93b1,
  71         0x6b46, 0x7acf, 0x4854, 0x59dd, 0x2d62, 0x3ceb, 0x0e70, 0x1ff9,
  72         0xf78f, 0xe606, 0xd49d, 0xc514, 0xb1ab, 0xa022, 0x92b9, 0x8330,
  73         0x7bc7, 0x6a4e, 0x58d5, 0x495c, 0x3de3, 0x2c6a, 0x1ef1, 0x0f78
  74 };
  75
  76 static u8 ap_t_ctrl_char_complemented[256]; /* list of characters to complement */
  77
  78 static void ap_hdlc_like_ctrl_char_list (u32 ctrl_char) {
  79         int i;
  80
  81         for (i = 0; i < 256; ++i)
  82                 ap_t_ctrl_char_complemented[i] = FALSE;
  83         for (i = 0; i < 32; ++i)
  84                 if ((ctrl_char >> i) & 0x0001)
  85                         ap_t_ctrl_char_complemented [i] = TRUE;
  86         ap_t_ctrl_char_complemented[HDLC_FLAG] = TRUE;
  87         ap_t_ctrl_char_complemented[HDLC_CTRL_ESC] = TRUE;
  88
  89 }
  90
  91 void init_CRC() {
  92         ap_hdlc_like_ctrl_char_list(0xffffffff);
  93 }
  94
  95 void hdlc_encode_modem(u8 *buffer_in, u32 lng_in,
  96                        u8 *buffer_out, u32 *lng_out) {
  97         u16 fcs;
  98         register u8 data;
  99         register u8 *p_data_out = buffer_out;
 100
 101         fcs = HDLC_LIKE_FCS_INIT_VAL;
 102
 103         /*
 104          *   Insert HDLC flag at the beginning of the frame
 105          */
 106         *p_data_out++ = HDLC_FLAG;
 107
 108 #define ESCAPE_CHAR(data_out, data) \
 109         if (ap_t_ctrl_char_complemented[data]) { \
 110                 *data_out++ = HDLC_CTRL_ESC; \
 111                 *data_out++ = data ^ 0x20; \
 112         } \
 113         else \
 114                 *data_out++ = data;
 115
 116         while (lng_in--) {
 117                 data = *buffer_in++;
 118
 119                 /*
 120                  *   FCS calculation
 121                  */
 122                 fcs = (fcs>>8) ^ t_ap_hdlc_like_fcs[((u8)(fcs^data)) & 0xff];
 123
 124                 ESCAPE_CHAR(p_data_out, data);
 125         }
 126
 127         /*
 128          *  Add FCS and closing flag
 129          */
 130         fcs ^= 0xFFFF;  // Complement
 131
 132         data = (u8)(fcs & 0xff);        /* LSB */
 133         ESCAPE_CHAR(p_data_out, data);
 134
 135         data = (u8)((fcs >> 8));        /* MSB */
 136         ESCAPE_CHAR(p_data_out, data);
 137 #undef ESCAPE_CHAR
 138
 139         *p_data_out++ = HDLC_FLAG;
 140
 141         *lng_out = (u32)(p_data_out - buffer_out);
 142 }
 143
 144 void hdlc_no_accm_encode(u8 *buffer_in, u32 lng_in,
 145                          u8 *buffer_out, u32 *lng_out) {
 146         u16 fcs;
 147         register u8 data;
 148         register u8 *p_data_out = buffer_out;
 149
 150         /*
 151          *   Insert HDLC flag at the beginning of the frame
 152          */
 153         fcs = HDLC_LIKE_FCS_INIT_VAL;
 154
 155         while (lng_in--) {
 156                 data = *buffer_in++;
 157                 /* calculate FCS */
 158                 fcs = (fcs>>8) ^ t_ap_hdlc_like_fcs[((u8)(fcs^data)) & 0xff];
 159                 *p_data_out++ = data;
 160         }
 161
 162         /*
 163          *  Add FCS and closing flag
 164          */
 165         fcs ^= 0xFFFF;  // Complement
 166         data = (u8)(fcs);
 167         *p_data_out++ = data;
 168
 169         data =(u8)((fcs >> 8));   // revense MSB / LSB
 170         *p_data_out++ = data;
 171
 172         *lng_out = (u32)(p_data_out - buffer_out);
 173 }
 174
 175 u32 hdlc_no_accm_decode(u8 *buffer_in, u32 lng_in) {
 176         u16 fcs;
 177         u32 lng = lng_in;
 178         register u8 data;
 179
 180         /*
 181          *   Insert HDLC flag at the beginning of the frame
 182          */
 183         fcs = HDLC_LIKE_FCS_INIT_VAL;
 184
 185         while (lng_in--) {
 186                 data = *buffer_in++;
 187                 /* calculate FCS */
 188                 fcs = (fcs>>8) ^ t_ap_hdlc_like_fcs[((u8)(fcs^data)) & 0xff];
 189         }
 190
 191         if (fcs == HDLC_FCS_OK)
 192                 return (lng-2);
 193         else
 194                 return 0;
 195 }
 196