ISDN: Make isdnhdlc usable for other ISDN drivers

isdnhdlc is useful for other ISDN drivers as well.
Move the include file to a central location and the source
to the central isdn location.

Signed-off-by: Karsten Keil <keil@b1-systems.de>

1 files changed, 603 insertions, 0 deletions

diff --git a/drivers/isdn/i4l/isdnhdlc.c b/drivers/isdn/i4l/isdnhdlc.c
new file mode 100644
index 0000000..44ec741
--- /dev/null
+++ b/drivers/isdn/i4l/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 <linux/isdn/hdlc.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);