st5481_hdlc.c

内核linux2.4.20,可跟rtlinux3.2打补丁 组成实时linux系统,编译内核

/*
 * Driver for ST5481 USB ISDN modem
 *
 * Author       Frode Isaksen
 * Copyright    2001 by Frode Isaksen      <[e-mail]>
 *              2001 by Kai Germaschewski  <[e-mail]>
 * 
 * This software may be used and distributed according to the terms
 * of the GNU General Public License, incorporated herein by reference.
 *
 */

#include "st5481_hdlc.h"

static const unsigned short int crc16_tab[] = {
	0x0000,0x1189,0x2312,0x329b,0x4624,0x57ad,0x6536,0x74bf,
	0x8c48,0x9dc1,0xaf5a,0xbed3,0xca6c,0xdbe5,0xe97e,0xf8f7,
	0x1081,0x0108,0x3393,0x221a,0x56a5,0x472c,0x75b7,0x643e,
	0x9cc9,0x8d40,0xbfdb,0xae52,0xdaed,0xcb64,0xf9ff,0xe876,
	0x2102,0x308b,0x0210,0x1399,0x6726,0x76af,0x4434,0x55bd,
	0xad4a,0xbcc3,0x8e58,0x9fd1,0xeb6e,0xfae7,0xc87c,0xd9f5,
	0x3183,0x200a,0x1291,0x0318,0x77a7,0x662e,0x54b5,0x453c,
	0xbdcb,0xac42,0x9ed9,0x8f50,0xfbef,0xea66,0xd8fd,0xc974,
	0x4204,0x538d,0x6116,0x709f,0x0420,0x15a9,0x2732,0x36bb,
	0xce4c,0xdfc5,0xed5e,0xfcd7,0x8868,0x99e1,0xab7a,0xbaf3,
	0x5285,0x430c,0x7197,0x601e,0x14a1,0x0528,0x37b3,0x263a,
	0xdecd,0xcf44,0xfddf,0xec56,0x98e9,0x8960,0xbbfb,0xaa72,
	0x6306,0x728f,0x4014,0x519d,0x2522,0x34ab,0x0630,0x17b9,
	0xef4e,0xfec7,0xcc5c,0xddd5,0xa96a,0xb8e3,0x8a78,0x9bf1,
	0x7387,0x620e,0x5095,0x411c,0x35a3,0x242a,0x16b1,0x0738,
	0xffcf,0xee46,0xdcdd,0xcd54,0xb9eb,0xa862,0x9af9,0x8b70,
	0x8408,0x9581,0xa71a,0xb693,0xc22c,0xd3a5,0xe13e,0xf0b7,
	0x0840,0x19c9,0x2b52,0x3adb,0x4e64,0x5fed,0x6d76,0x7cff,
	0x9489,0x8500,0xb79b,0xa612,0xd2ad,0xc324,0xf1bf,0xe036,
	0x18c1,0x0948,0x3bd3,0x2a5a,0x5ee5,0x4f6c,0x7df7,0x6c7e,
	0xa50a,0xb483,0x8618,0x9791,0xe32e,0xf2a7,0xc03c,0xd1b5,
	0x2942,0x38cb,0x0a50,0x1bd9,0x6f66,0x7eef,0x4c74,0x5dfd,
	0xb58b,0xa402,0x9699,0x8710,0xf3af,0xe226,0xd0bd,0xc134,
	0x39c3,0x284a,0x1ad1,0x0b58,0x7fe7,0x6e6e,0x5cf5,0x4d7c,
	0xc60c,0xd785,0xe51e,0xf497,0x8028,0x91a1,0xa33a,0xb2b3,
	0x4a44,0x5bcd,0x6956,0x78df,0x0c60,0x1de9,0x2f72,0x3efb,
	0xd68d,0xc704,0xf59f,0xe416,0x90a9,0x8120,0xb3bb,0xa232,
	0x5ac5,0x4b4c,0x79d7,0x685e,0x1ce1,0x0d68,0x3ff3,0x2e7a,
	0xe70e,0xf687,0xc41c,0xd595,0xa12a,0xb0a3,0x8238,0x93b1,
	0x6b46,0x7acf,0x4854,0x59dd,0x2d62,0x3ceb,0x0e70,0x1ff9,
	0xf78f,0xe606,0xd49d,0xc514,0xb1ab,0xa022,0x92b9,0x8330,
	0x7bc7,0x6a4e,0x58d5,0x495c,0x3de3,0x2c6a,0x1ef1,0x0f78
};



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 
hdlc_rcv_init(struct hdlc_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 
hdlc_out_init(struct hdlc_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;
}

/*
  hdlc_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 hdlc_decode(struct hdlc_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){
				unsigned cval;
				
				hdlc->data_bits = 0;
				hdlc->data_received = 1;
				cval = (hdlc->crc^hdlc->shift_reg) & 0xff;
				hdlc->crc = (hdlc->crc>>8)^crc16_tab[cval];
				// good byte received
				if (dsize--) {
					dst[hdlc->dstpos++] = hdlc->shift_reg;
				} else {
					// frame too long
					status = -HDLC_LENGTH_ERROR;
					hdlc->dstpos = 0;
				}