diff --git a/src/isdnhdlc.c b/src/isdnhdlc.c
new file mode 100644
index 0000000..027d1c5
--- /dev/null
+++ b/src/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);