patch-2.1.92 linux/drivers/isdn/hisax/rawhdlc.c

• Lines: 540
• Date: Wed Apr 1 16:21:02 1998
• Orig file: v2.1.91/linux/drivers/isdn/hisax/rawhdlc.c
• Orig date: Wed Dec 31 16:00:00 1969

diff -u --recursive --new-file v2.1.91/linux/drivers/isdn/hisax/rawhdlc.c linux/drivers/isdn/hisax/rawhdlc.c
@@ -0,0 +1,539 @@
+/* $Id: rawhdlc.c,v 1.2 1998/02/09 10:53:51 keil Exp $
+
+ * rawhdlc.c     support routines for cards that don't support HDLC
+ *
+ * Author     Karsten Keil (keil@temic-ech.spacenet.de)
+ *            Brent Baccala <baccala@FreeSoft.org>
+ *
+ *
+ * Some passive ISDN cards, such as the Traverse NETJet and the AMD 7930,
+ * don't perform HDLC encapsulation over the B channel.  Drivers for
+ * such cards use support routines in this file to perform B channel HDLC.
+ *
+ * Bit-synchronous HDLC encapsulation is a means of encapsulating packets
+ * over a continuously transmitting serial communications link.
+ * It looks like this:
+ *
+ *      11111111101111110...........0111111011111111111
+ *      iiiiiiiiiffffffffdddddddddddffffffffiiiiiiiiiii
+ *
+ *      i = idle     f = flag     d = data
+ *
+ * When idle, the channel sends a continuous string of ones (mark
+ * idle; illustrated), or a continuous string of flag characters (flag
+ * idle).  The beginning of a data frame is marked by a flag character
+ * (01111110), then comes the actual data, followed by another flag
+ * character, after which another frame may be sent immediately (a
+ * single flag may serve as both the end of one frame and the start of
+ * the next), or the link may return to idle.  Obviously, the flag
+ * character can not appear anywhere in the data (or a false
+ * end-of-frame would occur), so the transmitter performs
+ * "bit-stuffing" - inserting a zero bit after every five one bits,
+ * irregardless of the original bit after the five ones.  Byte
+ * ordering is irrelevent at this point - the data is treated as a
+ * string of bits, not bytes.  Since no more than 5 ones may now occur
+ * in a row, the flag sequence, with its 6 ones, is unique.
+ *
+ * Upon reception, a zero bit that occur after 5 one bits is simply
+ * discarded.  A series of 6 one bits is end-of-frame, and a series of
+ * 7 one bits is an abort.  Once bit-stuffing has been corrected for,
+ * an integer number of bytes should now be present.  The last two
+ * of these bytes form the Frame Check Sequence, a CRC that is verified
+ * and then discarded.  Note that bit-stuffing is performed on the FCS
+ * just as if it were regular data.
+ *
+ *
+ *
+ * int make_raw_hdlc_data(u_char *src, u_int slen,
+ *                        u_char *dst, u_int dsize)
+ *
+ *   Used for transmission.  Copies slen bytes from src to dst, performing
+ *   HDLC encapsulation (flag bytes, bit-stuffing, CRC) in the process.
+ *   dsize is size of destination buffer, and should be at least
+ *   ((6*slen)/5)+5 bytes to ensure adequate space will be available.
+ *   Function returns length (in bytes) of valid destination buffer, or
+ *   0 upon destination overflow.
+ *
+ * void init_hdlc_state(struct hdlc_state *stateptr, int mode)
+ *
+ *   Initializes hdlc_state structure before first call to read_raw_hdlc_data
+ *
+ *   mode = 0: Sane mode
+ *   mode = 1/2: 
+ *             Insane mode; NETJet use a shared unsigned int memory block (
+ * 	       with busmaster DMA), the bit pattern of every word is 
+ *  	       <8 B1> <8 B2> <8 Mon> <2 D> <4 C/I> <MX> <MR>
+ *	       according to Siemens IOM-2 interface, so we have to handle
+ *             the src buffer as unsigned int and have to shift/mask the
+ *             B-channel bytes.
+ *             mode 1 -> B1  mode 2  -> B2 data is used
+ *
+ * int read_raw_hdlc_data(struct hdlc_state *saved_state,
+ *                        u_char *src, u_int slen,
+ *                        u_char *dst, u_int dsize)
+ *
+ *   Used for reception.  Scans source buffer bit-by-bit looking for
+ *   valid HDLC frames, which are copied to destination buffer.  HDLC
+ *   state information is stored in a structure, which allows this
+ *   function to process frames spread across several blocks of raw
+ *   HDLC data.  Part of the state information is bit offsets into
+ *   the source and destination buffers.
+ *
+ *   A return value >0 indicates the length of a valid frame, now
+ *   stored in the destination buffer.  In this case, the source
+ *   buffer might not be completely processed, so this function should
+ *   be called again with the same source buffer, possibly with a
+ *   different destination buffer.
+ *
+ *   A return value of zero indicates that the source buffer was
+ *   completely processed without finding a valid end-of-packet;
+ *   however, we might be in the middle of packet reception, so
+ *   the function should be called again with the next block of
+ *   raw HDLC data and the same destination buffer.  It is NOT
+ *   permitted to change the destination buffer in this case,
+ *   since data may already have begun to be stored there.
+ *
+ *   A return value of -1 indicates some kind of error - destination
+ *   buffer overflow, CRC check failed, frame not a multiple of 8
+ *   bits.  Destination buffer probably contains invalid data, which
+ *   should be discarded.  Call function again with same source buffer
+ *   and a new (or same) destination buffer.
+ *
+ *   Suggested calling sequence:
+ *
+ *      init_hdlc_state(...);
+ *      for (EACH_RAW_DATA_BLOCK) {
+ *         while (len = read_raw_hdlc_data(...)) {
+ *             if (len == -1) DISCARD_FRAME;
+ *             else PROCESS_FRAME;
+ *         }
+ *      }
+ *
+ *
+ * Test the code in this file as follows:
+ *    gcc -DDEBUGME -o rawhdlctest rawhdlc.c
+ *    ./rawhdlctest < rawdata
+ *
+ * The file "rawdata" can be easily generated from a HISAX B-channel
+ * hex dump (CF CF CF 02 ...) using the following perl script:
+ *
+ * while(<>) {
+ *     @hexlist = split ' ';
+ *     while ($hexstr = shift(@hexlist)) {
+ *         printf "%c", hex($hexstr);
+ *     }
+ * }
+ *
+ */
+
+#ifdef DEBUGME
+#include <stdio.h>
+#endif
+
+#include <linux/types.h>
+#include <linux/ppp_defs.h>
+#include "rawhdlc.h"
+
+/* There's actually an identical copy of this table in the PPP code
+ * (ppp_crc16_table), but I don't want this code dependant on PPP
+ */
+
+// static 
+__u16 fcstab[256] =
+{
+	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
+};
+
+#define HDLC_ZERO_SEARCH 0
+#define HDLC_FLAG_SEARCH 1
+#define HDLC_FLAG_FOUND  2
+#define HDLC_FRAME_FOUND 3
+#define HDLC_NULL 4
+#define HDLC_PART 5
+#define HDLC_FULL 6
+
+#define HDLC_FLAG_VALUE	0x7e
+
+
+#define MAKE_RAW_BYTE for (j=0; j<8; j++) { \
+			bitcnt++;\
+			out_val >>= 1;\
+			if (val & 1) {\
+				s_one++;\
+				out_val |= 0x80;\
+			} else {\
+				s_one = 0;\
+				out_val &= 0x7f;\
+			}\
+			if (bitcnt==8) {\
+				if (d_cnt == dsize) return 0;\
+				dst[d_cnt++] = out_val;\
+				bitcnt = 0;\
+			}\
+			if (s_one == 5) {\
+				out_val >>= 1;\
+				out_val &= 0x7f;\
+				bitcnt++;\
+				s_one = 0;\
+			}\
+			if (bitcnt==8) {\
+				if (d_cnt == dsize) return 0;\
+				dst[d_cnt++] = out_val;\
+				bitcnt = 0;\
+			}\
+			val >>= 1;\
+		}
+
+/* Optimization suggestion: If needed, this function could be
+ * dramatically sped up using a state machine.  Each state would
+ * correspond to having seen N one bits, and being offset M bits into
+ * the current output byte.  N ranges from 0 to 4, M from 0 to 7, so
+ * we need 5*8 = 35 states.  Each state would have a table with 256
+ * entries, one for each input character.  Each entry would contain
+ * three output characters, an output state, an a byte increment
+ * that's either 1 or 2.  All this could fit in four bytes; so we need
+ * 4 bytes * 256 characters = 1 KB for each state (35 KB total).  Zero
+ * the output buffer before you start.  For each character in your
+ * input, you look it up in the current state's table and get three
+ * bytes to be or'ed into the output at the current byte offset, and
+ * an byte increment to move your pointer forward.  A simple Perl
+ * script could generate the tables.  Given HDLC semantics, probably
+ * would be better to set output to all 1s, then use ands instead of ors.
+ * A smaller state machine could operate on nibbles instead of bytes.
+ * A state machine for 32-bit architectures could use word offsets
+ * instead of byte offsets, requiring 5*32 = 160 states; probably
+ * best to work on nibbles in such a case.
+ */
+
+
+int make_raw_hdlc_data(u_char *src, u_int slen, u_char *dst, u_int dsize)
+{
+	register u_int i,d_cnt=0;
+	register u_char j;
+	register u_char val;
+	register u_char s_one = 0;
+	register u_char out_val = 0;
+	register u_char bitcnt = 0;
+	u_int fcs;
+	
+	
+	dst[d_cnt++] = HDLC_FLAG_VALUE;
+	fcs = PPP_INITFCS;
+	for (i=0; i<slen; i++) {
+		val = src[i];
+		fcs = PPP_FCS (fcs, val);
+		MAKE_RAW_BYTE;
+	}
+	fcs ^= 0xffff;
+	val = fcs & 0xff;
+	MAKE_RAW_BYTE;
+	val = (fcs>>8) & 0xff;
+	MAKE_RAW_BYTE;
+	val = HDLC_FLAG_VALUE;
+	for (j=0; j<8; j++) { 
+		bitcnt++;
+		out_val >>= 1;
+		if (val & 1)
+			out_val |= 0x80;
+		else
+			out_val &= 0x7f;
+		if (bitcnt==8) {
+			if (d_cnt == dsize) return 0;
+			dst[d_cnt++] = out_val;
+			bitcnt = 0;
+		}
+		val >>= 1;
+	}
+	if (bitcnt) {
+		while (8>bitcnt++) {
+			out_val >>= 1;
+			out_val |= 0x80;
+		}
+		if (d_cnt == dsize) return 0;
+		dst[d_cnt++] = out_val;
+	}
+
+	return d_cnt;
+}
+
+void init_hdlc_state(struct hdlc_state *stateptr, int mode)
+{
+	stateptr->state = HDLC_ZERO_SEARCH;
+	stateptr->r_one = 0;
+	stateptr->r_val = 0;
+	stateptr->o_bitcnt = 0;
+	stateptr->i_bitcnt = 0;
+	stateptr->insane_mode = mode;
+}
+
+/* Optimization suggestion: A similar state machine could surely
+ * be developed for this function as well.
+ */
+
+int read_raw_hdlc_data(struct hdlc_state *saved_state,
+                       u_char *src, u_int slen, u_char *dst, u_int dsize)
+{
+	int retval=0;
+	register u_char val;
+	register u_char state = saved_state->state;
+	register u_char r_one = saved_state->r_one;
+	register u_char r_val = saved_state->r_val;
+	register u_int o_bitcnt = saved_state->o_bitcnt;
+	register u_int i_bitcnt = saved_state->i_bitcnt;
+	register u_int fcs    = saved_state->fcs;
+	register u_int *isrc = (u_int *) src;
+        
+	/* Use i_bitcnt (bit offset into source buffer) to reload "val"
+	 * in case we're starting up again partway through a source buffer
+	 */
+
+	if ((i_bitcnt >> 3) < slen) {
+		if (saved_state->insane_mode==1) {
+			val = isrc[(i_bitcnt >> 3)] & 0xff;
+		} else if (saved_state->insane_mode==2) {
+			val = (isrc[i_bitcnt >> 3] >>8) & 0xff;
+		} else {
+			val = src[i_bitcnt >> 3];
+		}
+		val >>= i_bitcnt & 7;
+	}
+
+	/* One bit per loop.  Keep going until we've got something to
+	 * report (retval != 0), or we exhaust the source buffer
+	 */
+
+	while ((retval == 0) && ((i_bitcnt >> 3) < slen)) {
+		if ((i_bitcnt & 7) == 0) {
+			if (saved_state->insane_mode==1) {
+				val = isrc[(i_bitcnt >> 3)] & 0xff;
+			} else if (saved_state->insane_mode==2) {
+				val = (isrc[i_bitcnt >> 3] >>8) & 0xff;
+			} else {
+				val = src[i_bitcnt >> 3];
+			}
+#ifdef DEBUGME
+			printf("Input byte %d: 0x%2x\n", i_bitcnt>>3, val);
+#endif
+			if (val == 0xff) {
+				state = HDLC_ZERO_SEARCH;
+				o_bitcnt = 0;
+				r_one = 0;
+				i_bitcnt += 8;
+				continue;
+			}
+		}
+
+#ifdef DEBUGME
+		/* printf("Data bit=%d (%d/%d)\n", val&1, i_bitcnt>>3, i_bitcnt&7);*/
+#endif
+
+		if (state == HDLC_ZERO_SEARCH) {
+			if (val & 1) {
+				r_one++;
+			} else {
+				r_one=0;
+				state= HDLC_FLAG_SEARCH;
+			}
+		} else if (state == HDLC_FLAG_SEARCH) { 
+			if (val & 1) {
+				r_one++;
+				if (r_one>6) {
+					state=HDLC_ZERO_SEARCH;
+				}
+			} else {
+				if (r_one==6) {
+					o_bitcnt=0;
+					r_val=0;
+					state=HDLC_FLAG_FOUND;
+				}
+				r_one=0;
+			}
+		} else if (state ==  HDLC_FLAG_FOUND) {
+			if (val & 1) {
+				r_one++;
+				if (r_one>6) {
+					state=HDLC_ZERO_SEARCH;
+				} else {
+					r_val >>= 1;
+					r_val |= 0x80;
+					o_bitcnt++;
+				}
+			} else {
+				if (r_one==6) {
+					o_bitcnt=0;
+					r_val=0;
+					r_one=0;
+					i_bitcnt++;
+					val >>= 1;
+					continue;
+				} else if (r_one!=5) {
+					r_val >>= 1;
+					r_val &= 0x7f;
+					o_bitcnt++;
+				}
+				r_one=0;	
+			}
+			if ((state != HDLC_ZERO_SEARCH) &&
+				!(o_bitcnt & 7)) {
+#ifdef DEBUGME
+				printf("HDLC_FRAME_FOUND at i_bitcnt:%d\n",i_bitcnt);
+#endif
+				state=HDLC_FRAME_FOUND;
+				fcs = PPP_INITFCS;
+				dst[0] = r_val;
+				fcs = PPP_FCS (fcs, r_val);
+			}
+		} else if (state ==  HDLC_FRAME_FOUND) {
+			if (val & 1) {
+				r_one++;
+				if (r_one>6) {
+					state=HDLC_ZERO_SEARCH;
+					o_bitcnt=0;
+				} else {
+					r_val >>= 1;
+					r_val |= 0x80;
+					o_bitcnt++;
+				}
+			} else {
+				if (r_one==6) {
+					r_val=0; 
+					r_one=0;
+					o_bitcnt++;
+					if (o_bitcnt & 7) {
+						/* Alignment error */
+#ifdef DEBUGME
+						printf("Alignment error\n");
+#endif
+						state=HDLC_FLAG_SEARCH;
+						retval = -1;
+					} else if (fcs==PPP_GOODFCS) {
+						/* Valid frame */
+						state=HDLC_FLAG_FOUND;
+						retval = (o_bitcnt>>3)-3;
+					} else {
+						/* CRC error */
+#ifdef DEBUGME
+						printf("CRC error; fcs was 0x%x, should have been 0x%x\n", fcs, PPP_GOODFCS);
+#endif
+						state=HDLC_FLAG_FOUND;
+						retval = -1;
+					}
+				} else if (r_one==5) {
+					r_one=0;
+					i_bitcnt++;
+					val >>= 1;
+					continue;
+				} else {
+					r_val >>= 1;
+					r_val &= 0x7f;
+					o_bitcnt++;
+				}
+				r_one=0;	
+			}
+			if ((state == HDLC_FRAME_FOUND) &&
+				!(o_bitcnt & 7)) {
+				if ((o_bitcnt>>3)>=dsize) {
+					/* Buffer overflow error */
+#ifdef DEBUGME
+					printf("Buffer overflow error\n");
+#endif
+					r_val=0; 
+					state=HDLC_FLAG_SEARCH;
+					retval = -1;
+				} else {
+					dst[(o_bitcnt>>3)-1] = r_val;
+					fcs = PPP_FCS (fcs, r_val);
+#ifdef DEBUGME
+					printf("Output byte %d: 0x%02x; FCS 0x%04x\n", (o_bitcnt>>3)-1, r_val, fcs);
+#endif
+				}
+			}
+		}
+		i_bitcnt ++;
+		val >>= 1;
+	}
+
+	/* We exhausted the source buffer before anything else happened
+	 * (retval==0).  Reset i_bitcnt in expectation of a new source
+	 * buffer.  Other, we either had an error or a valid frame, so
+	 * reset o_bitcnt in expectation of a new destination buffer.
+	 */
+
+	if (retval == 0) {
+		i_bitcnt = 0;
+	} else {
+		o_bitcnt = 0;
+	}
+
+	saved_state->state = state;
+	saved_state->r_one = r_one;
+	saved_state->r_val = r_val;
+	saved_state->fcs = fcs;
+	saved_state->o_bitcnt = o_bitcnt;
+	saved_state->i_bitcnt = i_bitcnt;
+
+	return (retval);
+}
+
+
+
+#ifdef DEBUGME
+
+char buffer[1024];
+char obuffer[1024];
+
+main()
+{
+  int buflen=0;
+  int len;
+  struct hdlc_state hdlc_state;
+
+  while((buffer[buflen] = getc(stdin)) != EOF && buflen<1024) buflen++;
+
+  printf("buflen = %d\n", buflen);
+
+  init_hdlc_state(&hdlc_state, 0);
+
+  while (len = read_raw_hdlc_data(&hdlc_state,buffer,buflen,obuffer,1024)) {
+    if (len == -1) printf("Error @ byte %d/bit %d\n",
+			  hdlc_state.i_bitcnt>>3, hdlc_state.i_bitcnt & 7);
+    else {
+      printf("Frame received: len %d\n", len);
+    }
+  }
+
+  printf("Done\n");
+}
+
+#endif