cregit-Linux how code gets into the kernel

Release 4.7 drivers/isdn/i4l/isdnhdlc.c

Directory: drivers/isdn/i4l
/*
 * 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; }

Contributors

PersonTokensPropCommitsCommitProp
andrew mortonandrew morton2951.79%150.00%
karsten keilkarsten keil2748.21%150.00%
Total56100.00%2100.00%

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; }

Contributors

PersonTokensPropCommitsCommitProp
andrew mortonandrew morton8676.79%150.00%
karsten keilkarsten keil2623.21%150.00%
Total112100.00%2100.00%

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; }

Contributors

PersonTokensPropCommitsCommitProp
karsten keilkarsten keil63100.00%1100.00%
Total63100.00%1100.00%

/* 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; }

Contributors

PersonTokensPropCommitsCommitProp
andrew mortonandrew morton79091.97%114.29%
karsten keilkarsten keil576.64%228.57%
andrey paninandrey panin60.70%228.57%
oskar senftoskar senft40.47%114.29%
joe perchesjoe perches20.23%114.29%
Total859100.00%7100.00%

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; }

Contributors

PersonTokensPropCommitsCommitProp
andrew mortonandrew morton123092.27%116.67%
karsten keilkarsten keil977.28%350.00%
andrey paninandrey panin60.45%233.33%
Total1333100.00%6100.00%

EXPORT_SYMBOL(isdnhdlc_encode);

Overall Contributors

PersonTokensPropCommitsCommitProp
andrew mortonandrew morton220987.52%110.00%
karsten keilkarsten keil29211.57%440.00%
andrey paninandrey panin150.59%220.00%
oskar senftoskar senft40.16%110.00%
joe perchesjoe perches30.12%110.00%
jan engelhardtjan engelhardt10.04%110.00%
Total2524100.00%10100.00%
Directory: drivers/isdn/i4l
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