diff options
Diffstat (limited to 'drivers/isdn/hisax/isdnhdlc.c')
| -rw-r--r-- | drivers/isdn/hisax/isdnhdlc.c | 603 |
1 files changed, 603 insertions, 0 deletions
diff --git a/drivers/isdn/hisax/isdnhdlc.c b/drivers/isdn/hisax/isdnhdlc.c new file mode 100644 index 0000000..c69a77a --- /dev/null +++ b/drivers/isdn/hisax/isdnhdlc.c @@ -0,0 +1,603 @@ +/* + * isdnhdlc.c -- General purpose ISDN HDLC decoder. + * + *Copyright (C) 2002 Wolfgang Mües <wolfgang@iksw-muees.de> + * 2001 Frode Isaksen <fisaksen@bewan.com> + * 2001 Kai Germaschewski <kai.germaschewski@gmx.de> + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, write to the Free Software + * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. + */ + +#include <linux/module.h> +#include <linux/init.h> +#include <linux/crc-ccitt.h> +#include "isdnhdlc.h" + +/*-------------------------------------------------------------------*/ + +MODULE_AUTHOR("Wolfgang Mües <wolfgang@iksw-muees.de>, " + "Frode Isaksen <fisaksen@bewan.com>, " + "Kai Germaschewski <kai.germaschewski@gmx.de>"); +MODULE_DESCRIPTION("General purpose ISDN HDLC decoder"); +MODULE_LICENSE("GPL"); + +/*-------------------------------------------------------------------*/ + +enum { + HDLC_FAST_IDLE,HDLC_GET_FLAG_B0,HDLC_GETFLAG_B1A6,HDLC_GETFLAG_B7, + HDLC_GET_DATA,HDLC_FAST_FLAG +}; + +enum { + HDLC_SEND_DATA,HDLC_SEND_CRC1,HDLC_SEND_FAST_FLAG, + HDLC_SEND_FIRST_FLAG,HDLC_SEND_CRC2,HDLC_SEND_CLOSING_FLAG, + HDLC_SEND_IDLE1,HDLC_SEND_FAST_IDLE,HDLC_SENDFLAG_B0, + HDLC_SENDFLAG_B1A6,HDLC_SENDFLAG_B7,STOPPED +}; + +void isdnhdlc_rcv_init (struct isdnhdlc_vars *hdlc, int do_adapt56) +{ + hdlc->bit_shift = 0; + hdlc->hdlc_bits1 = 0; + hdlc->data_bits = 0; + hdlc->ffbit_shift = 0; + hdlc->data_received = 0; + hdlc->state = HDLC_GET_DATA; + hdlc->do_adapt56 = do_adapt56; + hdlc->dchannel = 0; + hdlc->crc = 0; + hdlc->cbin = 0; + hdlc->shift_reg = 0; + hdlc->ffvalue = 0; + hdlc->dstpos = 0; +} + +void isdnhdlc_out_init (struct isdnhdlc_vars *hdlc, int is_d_channel, int do_adapt56) +{ + hdlc->bit_shift = 0; + hdlc->hdlc_bits1 = 0; + hdlc->data_bits = 0; + hdlc->ffbit_shift = 0; + hdlc->data_received = 0; + hdlc->do_closing = 0; + hdlc->ffvalue = 0; + if (is_d_channel) { + hdlc->dchannel = 1; + hdlc->state = HDLC_SEND_FIRST_FLAG; + } else { + hdlc->dchannel = 0; + hdlc->state = HDLC_SEND_FAST_FLAG; + hdlc->ffvalue = 0x7e; + } + hdlc->cbin = 0x7e; + hdlc->bit_shift = 0; + if(do_adapt56){ + hdlc->do_adapt56 = 1; + hdlc->data_bits = 0; + hdlc->state = HDLC_SENDFLAG_B0; + } else { + hdlc->do_adapt56 = 0; + hdlc->data_bits = 8; + } + hdlc->shift_reg = 0; +} + +/* + isdnhdlc_decode - decodes HDLC frames from a transparent bit stream. + + The source buffer is scanned for valid HDLC frames looking for + flags (01111110) to indicate the start of a frame. If the start of + the frame is found, the bit stuffing is removed (0 after 5 1's). + When a new flag is found, the complete frame has been received + and the CRC is checked. + If a valid frame is found, the function returns the frame length + excluding the CRC with the bit HDLC_END_OF_FRAME set. + If the beginning of a valid frame is found, the function returns + the length. + If a framing error is found (too many 1s and not a flag) the function + returns the length with the bit HDLC_FRAMING_ERROR set. + If a CRC error is found the function returns the length with the + bit HDLC_CRC_ERROR set. + If the frame length exceeds the destination buffer size, the function + returns the length with the bit HDLC_LENGTH_ERROR set. + + src - source buffer + slen - source buffer length + count - number of bytes removed (decoded) from the source buffer + dst _ destination buffer + dsize - destination buffer size + returns - number of decoded bytes in the destination buffer and status + flag. + */ +int isdnhdlc_decode (struct isdnhdlc_vars *hdlc, const unsigned char *src, + int slen, int *count, unsigned char *dst, int dsize) +{ + int status=0; + + static const unsigned char fast_flag[]={ + 0x00,0x00,0x00,0x20,0x30,0x38,0x3c,0x3e,0x3f + }; + + static const unsigned char fast_flag_value[]={ + 0x00,0x7e,0xfc,0xf9,0xf3,0xe7,0xcf,0x9f,0x3f + }; + + static const unsigned char fast_abort[]={ + 0x00,0x00,0x80,0xc0,0xe0,0xf0,0xf8,0xfc,0xfe,0xff + }; + + *count = slen; + + while(slen > 0){ + if(hdlc->bit_shift==0){ + hdlc->cbin = *src++; + slen--; + hdlc->bit_shift = 8; + if(hdlc->do_adapt56){ + hdlc->bit_shift --; + } + } + + switch(hdlc->state){ + case STOPPED: + return 0; + case HDLC_FAST_IDLE: + if(hdlc->cbin == 0xff){ + hdlc->bit_shift = 0; + break; + } + hdlc->state = HDLC_GET_FLAG_B0; + hdlc->hdlc_bits1 = 0; + hdlc->bit_shift = 8; + break; + case HDLC_GET_FLAG_B0: + if(!(hdlc->cbin & 0x80)) { + hdlc->state = HDLC_GETFLAG_B1A6; + hdlc->hdlc_bits1 = 0; + } else { + if(!hdlc->do_adapt56){ + if(++hdlc->hdlc_bits1 >=8 ) if(hdlc->bit_shift==1) + hdlc->state = HDLC_FAST_IDLE; + } + } + hdlc->cbin<<=1; + hdlc->bit_shift --; + break; + case HDLC_GETFLAG_B1A6: + if(hdlc->cbin & 0x80){ + hdlc->hdlc_bits1++; + if(hdlc->hdlc_bits1==6){ + hdlc->state = HDLC_GETFLAG_B7; + } + } else { + hdlc->hdlc_bits1 = 0; + } + hdlc->cbin<<=1; + hdlc->bit_shift --; + break; + case HDLC_GETFLAG_B7: + if(hdlc->cbin & 0x80) { + hdlc->state = HDLC_GET_FLAG_B0; + } else { + hdlc->state = HDLC_GET_DATA; + hdlc->crc = 0xffff; + hdlc->shift_reg = 0; + hdlc->hdlc_bits1 = 0; + hdlc->data_bits = 0; + hdlc->data_received = 0; + } + hdlc->cbin<<=1; + hdlc->bit_shift --; + break; + case HDLC_GET_DATA: + if(hdlc->cbin & 0x80){ + hdlc->hdlc_bits1++; + switch(hdlc->hdlc_bits1){ + case 6: + break; + case 7: + if(hdlc->data_received) { + // bad frame + status = -HDLC_FRAMING_ERROR; + } + if(!hdlc->do_adapt56){ + if(hdlc->cbin==fast_abort[hdlc->bit_shift+1]){ + hdlc->state = HDLC_FAST_IDLE; + hdlc->bit_shift=1; + break; + } + } else { + hdlc->state = HDLC_GET_FLAG_B0; + } + break; + default: + hdlc->shift_reg>>=1; + hdlc->shift_reg |= 0x80; + hdlc->data_bits++; + break; + } + } else { + switch(hdlc->hdlc_bits1){ + case 5: + break; + case 6: + if(hdlc->data_received){ + if (hdlc->dstpos < 2) { + status = -HDLC_FRAMING_ERROR; + } else if (hdlc->crc != 0xf0b8){ + // crc error + status = -HDLC_CRC_ERROR; + } else { + // remove CRC + hdlc->dstpos -= 2; + // good frame + status = hdlc->dstpos; + } + } + hdlc->crc = 0xffff; + hdlc->shift_reg = 0; + hdlc->data_bits = 0; + if(!hdlc->do_adapt56){ + if(hdlc->cbin==fast_flag[hdlc->bit_shift]){ + hdlc->ffvalue = fast_flag_value[hdlc->bit_shift]; + hdlc->state = HDLC_FAST_FLAG; + hdlc->ffbit_shift = hdlc->bit_shift; + hdlc->bit_shift = 1; + } else { + hdlc->state = HDLC_GET_DATA; + hdlc->data_received = 0; + } + } else { + hdlc->state = HDLC_GET_DATA; + hdlc->data_received = 0; + } + break; + default: + hdlc->shift_reg>>=1; + hdlc->data_bits++; + break; + } + hdlc->hdlc_bits1 = 0; + } + if (status) { + hdlc->dstpos = 0; + *count -= slen; + hdlc->cbin <<= 1; + hdlc->bit_shift--; + return status; + } + if(hdlc->data_bits==8){ + hdlc->data_bits = 0; + hdlc->data_received = 1; + hdlc->crc = crc_ccitt_byte(hdlc->crc, hdlc->shift_reg); + + // good byte received + if (hdlc->dstpos < dsize) { + dst[hdlc->dstpos++] = hdlc->shift_reg; + } else { + // frame too long + status = -HDLC_LENGTH_ERROR; + hdlc->dstpos = 0; + } + } + hdlc->cbin <<= 1; + hdlc->bit_shift--; + break; + case HDLC_FAST_FLAG: + if(hdlc->cbin==hdlc->ffvalue){ + hdlc->bit_shift = 0; + break; + } else { + if(hdlc->cbin == 0xff){ + hdlc->state = HDLC_FAST_IDLE; + hdlc->bit_shift=0; + } else if(hdlc->ffbit_shift==8){ + hdlc->state = HDLC_GETFLAG_B7; + break; + } else { + hdlc->shift_reg = fast_abort[hdlc->ffbit_shift-1]; + hdlc->hdlc_bits1 = hdlc->ffbit_shift-2; + if(hdlc->hdlc_bits1<0)hdlc->hdlc_bits1 = 0; + hdlc->data_bits = hdlc->ffbit_shift-1; + hdlc->state = HDLC_GET_DATA; + hdlc->data_received = 0; + } + } + break; + default: + break; + } + } + *count -= slen; + return 0; +} + +/* + isdnhdlc_encode - encodes HDLC frames to a transparent bit stream. + + The bit stream starts with a beginning flag (01111110). After + that each byte is added to the bit stream with bit stuffing added + (0 after 5 1's). + When the last byte has been removed from the source buffer, the + CRC (2 bytes is added) and the frame terminates with the ending flag. + For the dchannel, the idle character (all 1's) is also added at the end. + If this function is called with empty source buffer (slen=0), flags or + idle character will be generated. + + src - source buffer + slen - source buffer length + count - number of bytes removed (encoded) from source buffer + dst _ destination buffer + dsize - destination buffer size + returns - number of encoded bytes in the destination buffer +*/ +int isdnhdlc_encode(struct isdnhdlc_vars *hdlc, const unsigned char *src, + unsigned short slen, int *count, + unsigned char *dst, int dsize) +{ + static const unsigned char xfast_flag_value[] = { + 0x7e,0x3f,0x9f,0xcf,0xe7,0xf3,0xf9,0xfc,0x7e + }; + + int len = 0; + + *count = slen; + + while (dsize > 0) { + if(hdlc->bit_shift==0){ + if(slen && !hdlc->do_closing){ + hdlc->shift_reg = *src++; + slen--; + if (slen == 0) + hdlc->do_closing = 1; /* closing sequence, CRC + flag(s) */ + hdlc->bit_shift = 8; + } else { + if(hdlc->state == HDLC_SEND_DATA){ + if(hdlc->data_received){ + hdlc->state = HDLC_SEND_CRC1; + hdlc->crc ^= 0xffff; + hdlc->bit_shift = 8; + hdlc->shift_reg = hdlc->crc & 0xff; + } else if(!hdlc->do_adapt56){ + hdlc->state = HDLC_SEND_FAST_FLAG; + } else { + hdlc->state = HDLC_SENDFLAG_B0; + } + } + + } + } + + switch(hdlc->state){ + case STOPPED: + while (dsize--) + *dst++ = 0xff; + + return dsize; + case HDLC_SEND_FAST_FLAG: + hdlc->do_closing = 0; + if(slen == 0){ + *dst++ = hdlc->ffvalue; + len++; + dsize--; + break; + } + if(hdlc->bit_shift==8){ + hdlc->cbin = hdlc->ffvalue>>(8-hdlc->data_bits); + hdlc->state = HDLC_SEND_DATA; + hdlc->crc = 0xffff; + hdlc->hdlc_bits1 = 0; + hdlc->data_received = 1; + } + break; + case HDLC_SENDFLAG_B0: + hdlc->do_closing = 0; + hdlc->cbin <<= 1; + hdlc->data_bits++; + hdlc->hdlc_bits1 = 0; + hdlc->state = HDLC_SENDFLAG_B1A6; + break; + case HDLC_SENDFLAG_B1A6: + hdlc->cbin <<= 1; + hdlc->data_bits++; + hdlc->cbin++; + if(++hdlc->hdlc_bits1 == 6) + hdlc->state = HDLC_SENDFLAG_B7; + break; + case HDLC_SENDFLAG_B7: + hdlc->cbin <<= 1; + hdlc->data_bits++; + if(slen == 0){ + hdlc->state = HDLC_SENDFLAG_B0; + break; + } + if(hdlc->bit_shift==8){ + hdlc->state = HDLC_SEND_DATA; + hdlc->crc = 0xffff; + hdlc->hdlc_bits1 = 0; + hdlc->data_received = 1; + } + break; + case HDLC_SEND_FIRST_FLAG: + hdlc->data_received = 1; + if(hdlc->data_bits==8){ + hdlc->state = HDLC_SEND_DATA; + hdlc->crc = 0xffff; + hdlc->hdlc_bits1 = 0; + break; + } + hdlc->cbin <<= 1; + hdlc->data_bits++; + if(hdlc->shift_reg & 0x01) + hdlc->cbin++; + hdlc->shift_reg >>= 1; + hdlc->bit_shift--; + if(hdlc->bit_shift==0){ + hdlc->state = HDLC_SEND_DATA; + hdlc->crc = 0xffff; + hdlc->hdlc_bits1 = 0; + } + break; + case HDLC_SEND_DATA: + hdlc->cbin <<= 1; + hdlc->data_bits++; + if(hdlc->hdlc_bits1 == 5){ + hdlc->hdlc_bits1 = 0; + break; + } + if(hdlc->bit_shift==8){ + hdlc->crc = crc_ccitt_byte(hdlc->crc, hdlc->shift_reg); + } + if(hdlc->shift_reg & 0x01){ + hdlc->hdlc_bits1++; + hdlc->cbin++; + hdlc->shift_reg >>= 1; + hdlc->bit_shift--; + } else { + hdlc->hdlc_bits1 = 0; + hdlc->shift_reg >>= 1; + hdlc->bit_shift--; + } + break; + case HDLC_SEND_CRC1: + hdlc->cbin <<= 1; + hdlc->data_bits++; + if(hdlc->hdlc_bits1 == 5){ + hdlc->hdlc_bits1 = 0; + break; + } + if(hdlc->shift_reg & 0x01){ + hdlc->hdlc_bits1++; + hdlc->cbin++; + hdlc->shift_reg >>= 1; + hdlc->bit_shift--; + } else { + hdlc->hdlc_bits1 = 0; + hdlc->shift_reg >>= 1; + hdlc->bit_shift--; + } + if(hdlc->bit_shift==0){ + hdlc->shift_reg = (hdlc->crc >> 8); + hdlc->state = HDLC_SEND_CRC2; + hdlc->bit_shift = 8; + } + break; + case HDLC_SEND_CRC2: + hdlc->cbin <<= 1; + hdlc->data_bits++; + if(hdlc->hdlc_bits1 == 5){ + hdlc->hdlc_bits1 = 0; + break; + } + if(hdlc->shift_reg & 0x01){ + hdlc->hdlc_bits1++; + hdlc->cbin++; + hdlc->shift_reg >>= 1; + hdlc->bit_shift--; + } else { + hdlc->hdlc_bits1 = 0; + hdlc->shift_reg >>= 1; + hdlc->bit_shift--; + } + if(hdlc->bit_shift==0){ + hdlc->shift_reg = 0x7e; + hdlc->state = HDLC_SEND_CLOSING_FLAG; + hdlc->bit_shift = 8; + } + break; + case HDLC_SEND_CLOSING_FLAG: + hdlc->cbin <<= 1; + hdlc->data_bits++; + if(hdlc->hdlc_bits1 == 5){ + hdlc->hdlc_bits1 = 0; + break; + } + if(hdlc->shift_reg & 0x01){ + hdlc->cbin++; + } + hdlc->shift_reg >>= 1; + hdlc->bit_shift--; + if(hdlc->bit_shift==0){ + hdlc->ffvalue = xfast_flag_value[hdlc->data_bits]; + if(hdlc->dchannel){ + hdlc->ffvalue = 0x7e; + hdlc->state = HDLC_SEND_IDLE1; + hdlc->bit_shift = 8-hdlc->data_bits; + if(hdlc->bit_shift==0) + hdlc->state = HDLC_SEND_FAST_IDLE; + } else { + if(!hdlc->do_adapt56){ + hdlc->state = HDLC_SEND_FAST_FLAG; + hdlc->data_received = 0; + } else { + hdlc->state = HDLC_SENDFLAG_B0; + hdlc->data_received = 0; + } + // Finished with this frame, send flags + if (dsize > 1) dsize = 1; + } + } + break; + case HDLC_SEND_IDLE1: + hdlc->do_closing = 0; + hdlc->cbin <<= 1; + hdlc->cbin++; + hdlc->data_bits++; + hdlc->bit_shift--; + if(hdlc->bit_shift==0){ + hdlc->state = HDLC_SEND_FAST_IDLE; + hdlc->bit_shift = 0; + } + break; + case HDLC_SEND_FAST_IDLE: + hdlc->do_closing = 0; + hdlc->cbin = 0xff; + hdlc->data_bits = 8; + if(hdlc->bit_shift == 8){ + hdlc->cbin = 0x7e; + hdlc->state = HDLC_SEND_FIRST_FLAG; + } else { + *dst++ = hdlc->cbin; + hdlc->bit_shift = hdlc->data_bits = 0; + len++; + dsize = 0; + } + break; + default: + break; + } + if(hdlc->do_adapt56){ + if(hdlc->data_bits==7){ + hdlc->cbin <<= 1; + hdlc->cbin++; + hdlc->data_bits++; + } + } + if(hdlc->data_bits==8){ + *dst++ = hdlc->cbin; + hdlc->data_bits = 0; + len++; + dsize--; + } + } + *count -= slen; + + return len; +} + +EXPORT_SYMBOL(isdnhdlc_rcv_init); +EXPORT_SYMBOL(isdnhdlc_decode); +EXPORT_SYMBOL(isdnhdlc_out_init); +EXPORT_SYMBOL(isdnhdlc_encode); |
