diff options
Diffstat (limited to 'drivers/isdn/i4l/isdnhdlc.c')
| -rw-r--r-- | drivers/isdn/i4l/isdnhdlc.c | 630 |
1 files changed, 630 insertions, 0 deletions
diff --git a/drivers/isdn/i4l/isdnhdlc.c b/drivers/isdn/i4l/isdnhdlc.c new file mode 100644 index 000000000000..c989aa35dc2f --- /dev/null +++ b/drivers/isdn/i4l/isdnhdlc.c @@ -0,0 +1,630 @@ +/* + * isdnhdlc.c -- General purpose ISDN HDLC decoder. + * + * Copyright (C) + * 2009 Karsten Keil <keil@b1-systems.de> + * 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 <linux/isdn/hdlc.h> +#include <linux/bitrev.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, HDLC_SENDFLAG_ONE +}; + +void isdnhdlc_rcv_init(struct isdnhdlc_vars *hdlc, u32 features) +{ + memset(hdlc, 0, sizeof(struct isdnhdlc_vars)); + hdlc->state = HDLC_GET_DATA; + if (features & HDLC_56KBIT) + hdlc->do_adapt56 = 1; + if (features & HDLC_BITREVERSE) + hdlc->do_bitreverse = 1; +} +EXPORT_SYMBOL(isdnhdlc_out_init); + +void isdnhdlc_out_init(struct isdnhdlc_vars *hdlc, u32 features) +{ + memset(hdlc, 0, sizeof(struct isdnhdlc_vars)); + if (features & HDLC_DCHANNEL) { + 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; + if (features & HDLC_56KBIT) { + hdlc->do_adapt56 = 1; + hdlc->state = HDLC_SENDFLAG_B0; + } else + hdlc->data_bits = 8; + if (features & HDLC_BITREVERSE) + hdlc->do_bitreverse = 1; +} +EXPORT_SYMBOL(isdnhdlc_rcv_init); + +static int +check_frame(struct isdnhdlc_vars *hdlc) +{ + int status; + + if (hdlc->dstpos < 2) /* too small - framing error */ + 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; + } + return status; +} + +/* + 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 u8 *src, int slen, + int *count, u8 *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 + }; + +#define handle_fast_flag(h) \ + do {\ + if (h->cbin == fast_flag[h->bit_shift]) {\ + h->ffvalue = fast_flag_value[h->bit_shift];\ + h->state = HDLC_FAST_FLAG;\ + h->ffbit_shift = h->bit_shift;\ + h->bit_shift = 1;\ + } else {\ + h->state = HDLC_GET_DATA;\ + h->data_received = 0;\ + } \ + } while (0) + +#define handle_abort(h) \ + do {\ + h->shift_reg = fast_abort[h->ffbit_shift - 1];\ + h->hdlc_bits1 = h->ffbit_shift - 2;\ + if (h->hdlc_bits1 < 0)\ + h->hdlc_bits1 = 0;\ + h->data_bits = h->ffbit_shift - 1;\ + h->state = HDLC_GET_DATA;\ + h->data_received = 0;\ + } while (0) + + *count = slen; + + while (slen > 0) { + if (hdlc->bit_shift == 0) { + /* the code is for bitreverse streams */ + if (hdlc->do_bitreverse == 0) + hdlc->cbin = bitrev8(*src++); + else + 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) && + (++hdlc->hdlc_bits1 >= 8) && + (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) + status = check_frame(hdlc); + hdlc->crc = 0xffff; + hdlc->shift_reg = 0; + hdlc->data_bits = 0; + if (!hdlc->do_adapt56) + handle_fast_flag(hdlc); + 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 + handle_abort(hdlc); + } + break; + default: + break; + } + } + *count -= slen; + return 0; +} +EXPORT_SYMBOL(isdnhdlc_decode); +/* + 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 u8 *src, u16 slen, + int *count, u8 *dst, int dsize) +{ + static const unsigned char xfast_flag_value[] = { + 0x7e, 0x3f, 0x9f, 0xcf, 0xe7, 0xf3, 0xf9, 0xfc, 0x7e + }; + + int len = 0; + + *count = slen; + + /* special handling for one byte frames */ + if ((slen == 1) && (hdlc->state == HDLC_SEND_FAST_FLAG)) + hdlc->state = HDLC_SENDFLAG_ONE; + while (dsize > 0) { + if (hdlc->bit_shift == 0) { + if (slen && !hdlc->do_closing) { + hdlc->shift_reg = *src++; + slen--; + if (slen == 0) + /* closing sequence, CRC + flag(s) */ + hdlc->do_closing = 1; + 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) { + /* the code is for bitreverse streams */ + if (hdlc->do_bitreverse == 0) + *dst++ = bitrev8(hdlc->ffvalue); + else + *dst++ = hdlc->ffvalue; + len++; + dsize--; + break; + } + /* fall through */ + case HDLC_SENDFLAG_ONE: + 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 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 { + /* the code is for bitreverse streams */ + if (hdlc->do_bitreverse == 0) + *dst++ = bitrev8(hdlc->cbin); + else + *dst++ = hdlc->cbin; + hdlc->bit_shift = 0; + 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) { + /* the code is for bitreverse streams */ + if (hdlc->do_bitreverse == 0) + *dst++ = bitrev8(hdlc->cbin); + else + *dst++ = hdlc->cbin; + hdlc->data_bits = 0; + len++; + dsize--; + } + } + *count -= slen; + + return len; +} +EXPORT_SYMBOL(isdnhdlc_encode); |