/*
   * Common data handling layer for bas_gigaset
   *
   * Copyright (c) 2005 by Tilman Schmidt <tilman@imap.cc>,
   *                       Hansjoerg Lipp <hjlipp@web.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.
   * =====================================================================

   */
  
  #include "gigaset.h"
  #include <linux/crc-ccitt.h>

  #include <linux/bitrev.h>

  
  /* access methods for isowbuf_t */
  /* ============================ */
  
  /* initialize buffer structure
   */
  void gigaset_isowbuf_init(struct isowbuf_t *iwb, unsigned char idle)
  {

  	iwb->read = 0;
  	iwb->nextread = 0;
  	iwb->write = 0;

  	atomic_set(&iwb->writesem, 1);
  	iwb->wbits = 0;
  	iwb->idle = idle;
  	memset(iwb->data + BAS_OUTBUFSIZE, idle, BAS_OUTBUFPAD);
  }
  
  /* compute number of bytes which can be appended to buffer
   * so that there is still room to append a maximum frame of flags
   */
  static inline int isowbuf_freebytes(struct isowbuf_t *iwb)
  {
  	int read, write, freebytes;

  	read = iwb->read;
  	write = iwb->write;

  	freebytes = read - write;
  	if (freebytes > 0) {

  		/* no wraparound: need padding space within regular area */
  		return freebytes - BAS_OUTBUFPAD;
  	} else if (read < BAS_OUTBUFPAD) {
  		/* wraparound: can use space up to end of regular area */
  		return BAS_OUTBUFSIZE - write;
  	} else {
  		/* following the wraparound yields more space */
  		return freebytes + BAS_OUTBUFSIZE - BAS_OUTBUFPAD;
  	}
  }

  /* start writing
   * acquire the write semaphore
   * return true if acquired, false if busy
   */
  static inline int isowbuf_startwrite(struct isowbuf_t *iwb)
  {
  	if (!atomic_dec_and_test(&iwb->writesem)) {
  		atomic_inc(&iwb->writesem);

  		gig_dbg(DEBUG_ISO, "%s: couldn't acquire iso write semaphore",
  			__func__);

  		return 0;
  	}

  	gig_dbg(DEBUG_ISO,
  		"%s: acquired iso write semaphore, data[write]=%02x, nbits=%d",

  		__func__, iwb->data[iwb->write], iwb->wbits);

  	return 1;
  }
  
  /* finish writing

   * release the write semaphore

   * returns the current write position
   */
  static inline int isowbuf_donewrite(struct isowbuf_t *iwb)
  {

  	int write = iwb->write;

  	atomic_inc(&iwb->writesem);
  	return write;
  }
  
  /* append bits to buffer without any checks
   * - data contains bits to append, starting at LSB
   * - nbits is number of bits to append (0..24)
   * must be called with the write semaphore held
   * If more than nbits bits are set in data, the extraneous bits are set in the
   * buffer too, but the write position is only advanced by nbits.
   */
  static inline void isowbuf_putbits(struct isowbuf_t *iwb, u32 data, int nbits)
  {

  	int write = iwb->write;

  	data <<= iwb->wbits;
  	data |= iwb->data[write];
  	nbits += iwb->wbits;
  	while (nbits >= 8) {
  		iwb->data[write++] = data & 0xff;
  		write %= BAS_OUTBUFSIZE;
  		data >>= 8;
  		nbits -= 8;
  	}
  	iwb->wbits = nbits;
  	iwb->data[write] = data & 0xff;

  	iwb->write = write;

  }
  
  /* put final flag on HDLC bitstream
   * also sets the idle fill byte to the correspondingly shifted flag pattern
   * must be called with the write semaphore held
   */
  static inline void isowbuf_putflag(struct isowbuf_t *iwb)
  {
  	int write;
  
  	/* add two flags, thus reliably covering one byte */
  	isowbuf_putbits(iwb, 0x7e7e, 8);
  	/* recover the idle flag byte */

  	write = iwb->write;

  	iwb->idle = iwb->data[write];

  	gig_dbg(DEBUG_ISO, "idle fill byte %02x", iwb->idle);

  	/* mask extraneous bits in buffer */
  	iwb->data[write] &= (1 << iwb->wbits) - 1;
  }
  
  /* retrieve a block of bytes for sending
   * The requested number of bytes is provided as a contiguous block.
   * If necessary, the frame is filled to the requested number of bytes
   * with the idle value.
   * returns offset to frame, < 0 on busy or error
   */
  int gigaset_isowbuf_getbytes(struct isowbuf_t *iwb, int size)
  {
  	int read, write, limit, src, dst;
  	unsigned char pbyte;

  	read = iwb->nextread;
  	write = iwb->write;

  	if (likely(read == write)) {

  		/* return idle frame */
  		return read < BAS_OUTBUFPAD ?

  			BAS_OUTBUFSIZE : read - BAS_OUTBUFPAD;

  	}
  
  	limit = read + size;

  	gig_dbg(DEBUG_STREAM, "%s: read=%d write=%d limit=%d",
  		__func__, read, write, limit);

  #ifdef CONFIG_GIGASET_DEBUG
  	if (unlikely(size < 0 || size > BAS_OUTBUFPAD)) {

  		pr_err("invalid size %d
  ", size);

  		return -EINVAL;
  	}

  #endif
  
  	if (read < write) {
  		/* no wraparound in valid data */
  		if (limit >= write) {
  			/* append idle frame */
  			if (!isowbuf_startwrite(iwb))
  				return -EBUSY;
  			/* write position could have changed */

  			write = iwb->write;
  			if (limit >= write) {

  				pbyte = iwb->data[write]; /* save
  							     partial byte */

  				limit = write + BAS_OUTBUFPAD;

  				gig_dbg(DEBUG_STREAM,
  					"%s: filling %d->%d with %02x",
  					__func__, write, limit, iwb->idle);

  				if (write + BAS_OUTBUFPAD < BAS_OUTBUFSIZE)
  					memset(iwb->data + write, iwb->idle,
  					       BAS_OUTBUFPAD);
  				else {
  					/* wraparound, fill entire pad area */
  					memset(iwb->data + write, iwb->idle,
  					       BAS_OUTBUFSIZE + BAS_OUTBUFPAD
  					       - write);
  					limit = 0;
  				}

  				gig_dbg(DEBUG_STREAM,
  					"%s: restoring %02x at %d",
  					__func__, pbyte, limit);

  				iwb->data[limit] = pbyte; /* restore
  							     partial byte */

  				iwb->write = limit;

  			}
  			isowbuf_donewrite(iwb);
  		}
  	} else {
  		/* valid data wraparound */
  		if (limit >= BAS_OUTBUFSIZE) {
  			/* copy wrapped part into pad area */
  			src = 0;
  			dst = BAS_OUTBUFSIZE;
  			while (dst < limit && src < write)
  				iwb->data[dst++] = iwb->data[src++];
  			if (dst <= limit) {
  				/* fill pad area with idle byte */
  				memset(iwb->data + dst, iwb->idle,
  				       BAS_OUTBUFSIZE + BAS_OUTBUFPAD - dst);
  			}
  			limit = src;
  		}
  	}

  	iwb->nextread = limit;

  	return read;
  }
  
  /* dump_bytes
   * write hex bytes to syslog for debugging
   */
  static inline void dump_bytes(enum debuglevel level, const char *tag,

  			      unsigned char *bytes, int count)

  {
  #ifdef CONFIG_GIGASET_DEBUG
  	unsigned char c;
  	static char dbgline[3 * 32 + 1];

  	int i = 0;

  
  	if (!(gigaset_debuglevel & level))
  		return;

  	while (count-- > 0) {
  		if (i > sizeof(dbgline) - 4) {
  			dbgline[i] = '\0';

  			gig_dbg(level, "%s:%s", tag, dbgline);

  			i = 0;
  		}
  		c = *bytes++;
  		dbgline[i] = (i && !(i % 12)) ? '-' : ' ';
  		i++;

  		dbgline[i++] = hex_asc_hi(c);
  		dbgline[i++] = hex_asc_lo(c);

  	}
  	dbgline[i] = '\0';

  	gig_dbg(level, "%s:%s", tag, dbgline);

  #endif
  }
  
  /*============================================================================*/
  
  /* bytewise HDLC bitstuffing via table lookup
   * lookup table: 5 subtables for 0..4 preceding consecutive '1' bits
   * index: 256*(number of preceding '1' bits) + (next byte to stuff)
   * value: bit  9.. 0 = result bits
   *        bit 12..10 = number of trailing '1' bits in result
   *        bit 14..13 = number of bits added by stuffing
   */

  static const u16 stufftab[5 * 256] = {

  /* previous 1s = 0: */

   0x0000, 0x0001, 0x0002, 0x0003, 0x0004, 0x0005, 0x0006, 0x0007, 0x0008, 0x0009, 0x000a, 0x000b, 0x000c, 0x000d, 0x000e, 0x000f,
   0x0010, 0x0011, 0x0012, 0x0013, 0x0014, 0x0015, 0x0016, 0x0017, 0x0018, 0x0019, 0x001a, 0x001b, 0x001c, 0x001d, 0x001e, 0x201f,
   0x0020, 0x0021, 0x0022, 0x0023, 0x0024, 0x0025, 0x0026, 0x0027, 0x0028, 0x0029, 0x002a, 0x002b, 0x002c, 0x002d, 0x002e, 0x002f,
   0x0030, 0x0031, 0x0032, 0x0033, 0x0034, 0x0035, 0x0036, 0x0037, 0x0038, 0x0039, 0x003a, 0x003b, 0x003c, 0x003d, 0x203e, 0x205f,
   0x0040, 0x0041, 0x0042, 0x0043, 0x0044, 0x0045, 0x0046, 0x0047, 0x0048, 0x0049, 0x004a, 0x004b, 0x004c, 0x004d, 0x004e, 0x004f,
   0x0050, 0x0051, 0x0052, 0x0053, 0x0054, 0x0055, 0x0056, 0x0057, 0x0058, 0x0059, 0x005a, 0x005b, 0x005c, 0x005d, 0x005e, 0x209f,
   0x0060, 0x0061, 0x0062, 0x0063, 0x0064, 0x0065, 0x0066, 0x0067, 0x0068, 0x0069, 0x006a, 0x006b, 0x006c, 0x006d, 0x006e, 0x006f,
   0x0070, 0x0071, 0x0072, 0x0073, 0x0074, 0x0075, 0x0076, 0x0077, 0x0078, 0x0079, 0x007a, 0x007b, 0x207c, 0x207d, 0x20be, 0x20df,
   0x0480, 0x0481, 0x0482, 0x0483, 0x0484, 0x0485, 0x0486, 0x0487, 0x0488, 0x0489, 0x048a, 0x048b, 0x048c, 0x048d, 0x048e, 0x048f,
   0x0490, 0x0491, 0x0492, 0x0493, 0x0494, 0x0495, 0x0496, 0x0497, 0x0498, 0x0499, 0x049a, 0x049b, 0x049c, 0x049d, 0x049e, 0x251f,
   0x04a0, 0x04a1, 0x04a2, 0x04a3, 0x04a4, 0x04a5, 0x04a6, 0x04a7, 0x04a8, 0x04a9, 0x04aa, 0x04ab, 0x04ac, 0x04ad, 0x04ae, 0x04af,
   0x04b0, 0x04b1, 0x04b2, 0x04b3, 0x04b4, 0x04b5, 0x04b6, 0x04b7, 0x04b8, 0x04b9, 0x04ba, 0x04bb, 0x04bc, 0x04bd, 0x253e, 0x255f,
   0x08c0, 0x08c1, 0x08c2, 0x08c3, 0x08c4, 0x08c5, 0x08c6, 0x08c7, 0x08c8, 0x08c9, 0x08ca, 0x08cb, 0x08cc, 0x08cd, 0x08ce, 0x08cf,
   0x08d0, 0x08d1, 0x08d2, 0x08d3, 0x08d4, 0x08d5, 0x08d6, 0x08d7, 0x08d8, 0x08d9, 0x08da, 0x08db, 0x08dc, 0x08dd, 0x08de, 0x299f,
   0x0ce0, 0x0ce1, 0x0ce2, 0x0ce3, 0x0ce4, 0x0ce5, 0x0ce6, 0x0ce7, 0x0ce8, 0x0ce9, 0x0cea, 0x0ceb, 0x0cec, 0x0ced, 0x0cee, 0x0cef,
   0x10f0, 0x10f1, 0x10f2, 0x10f3, 0x10f4, 0x10f5, 0x10f6, 0x10f7, 0x20f8, 0x20f9, 0x20fa, 0x20fb, 0x257c, 0x257d, 0x29be, 0x2ddf,

  /* previous 1s = 1: */

   0x0000, 0x0001, 0x0002, 0x0003, 0x0004, 0x0005, 0x0006, 0x0007, 0x0008, 0x0009, 0x000a, 0x000b, 0x000c, 0x000d, 0x000e, 0x200f,
   0x0010, 0x0011, 0x0012, 0x0013, 0x0014, 0x0015, 0x0016, 0x0017, 0x0018, 0x0019, 0x001a, 0x001b, 0x001c, 0x001d, 0x001e, 0x202f,
   0x0020, 0x0021, 0x0022, 0x0023, 0x0024, 0x0025, 0x0026, 0x0027, 0x0028, 0x0029, 0x002a, 0x002b, 0x002c, 0x002d, 0x002e, 0x204f,
   0x0030, 0x0031, 0x0032, 0x0033, 0x0034, 0x0035, 0x0036, 0x0037, 0x0038, 0x0039, 0x003a, 0x003b, 0x003c, 0x003d, 0x203e, 0x206f,
   0x0040, 0x0041, 0x0042, 0x0043, 0x0044, 0x0045, 0x0046, 0x0047, 0x0048, 0x0049, 0x004a, 0x004b, 0x004c, 0x004d, 0x004e, 0x208f,
   0x0050, 0x0051, 0x0052, 0x0053, 0x0054, 0x0055, 0x0056, 0x0057, 0x0058, 0x0059, 0x005a, 0x005b, 0x005c, 0x005d, 0x005e, 0x20af,
   0x0060, 0x0061, 0x0062, 0x0063, 0x0064, 0x0065, 0x0066, 0x0067, 0x0068, 0x0069, 0x006a, 0x006b, 0x006c, 0x006d, 0x006e, 0x20cf,
   0x0070, 0x0071, 0x0072, 0x0073, 0x0074, 0x0075, 0x0076, 0x0077, 0x0078, 0x0079, 0x007a, 0x007b, 0x207c, 0x207d, 0x20be, 0x20ef,
   0x0480, 0x0481, 0x0482, 0x0483, 0x0484, 0x0485, 0x0486, 0x0487, 0x0488, 0x0489, 0x048a, 0x048b, 0x048c, 0x048d, 0x048e, 0x250f,
   0x0490, 0x0491, 0x0492, 0x0493, 0x0494, 0x0495, 0x0496, 0x0497, 0x0498, 0x0499, 0x049a, 0x049b, 0x049c, 0x049d, 0x049e, 0x252f,
   0x04a0, 0x04a1, 0x04a2, 0x04a3, 0x04a4, 0x04a5, 0x04a6, 0x04a7, 0x04a8, 0x04a9, 0x04aa, 0x04ab, 0x04ac, 0x04ad, 0x04ae, 0x254f,
   0x04b0, 0x04b1, 0x04b2, 0x04b3, 0x04b4, 0x04b5, 0x04b6, 0x04b7, 0x04b8, 0x04b9, 0x04ba, 0x04bb, 0x04bc, 0x04bd, 0x253e, 0x256f,
   0x08c0, 0x08c1, 0x08c2, 0x08c3, 0x08c4, 0x08c5, 0x08c6, 0x08c7, 0x08c8, 0x08c9, 0x08ca, 0x08cb, 0x08cc, 0x08cd, 0x08ce, 0x298f,
   0x08d0, 0x08d1, 0x08d2, 0x08d3, 0x08d4, 0x08d5, 0x08d6, 0x08d7, 0x08d8, 0x08d9, 0x08da, 0x08db, 0x08dc, 0x08dd, 0x08de, 0x29af,
   0x0ce0, 0x0ce1, 0x0ce2, 0x0ce3, 0x0ce4, 0x0ce5, 0x0ce6, 0x0ce7, 0x0ce8, 0x0ce9, 0x0cea, 0x0ceb, 0x0cec, 0x0ced, 0x0cee, 0x2dcf,
   0x10f0, 0x10f1, 0x10f2, 0x10f3, 0x10f4, 0x10f5, 0x10f6, 0x10f7, 0x20f8, 0x20f9, 0x20fa, 0x20fb, 0x257c, 0x257d, 0x29be, 0x31ef,

  /* previous 1s = 2: */

   0x0000, 0x0001, 0x0002, 0x0003, 0x0004, 0x0005, 0x0006, 0x2007, 0x0008, 0x0009, 0x000a, 0x000b, 0x000c, 0x000d, 0x000e, 0x2017,
   0x0010, 0x0011, 0x0012, 0x0013, 0x0014, 0x0015, 0x0016, 0x2027, 0x0018, 0x0019, 0x001a, 0x001b, 0x001c, 0x001d, 0x001e, 0x2037,
   0x0020, 0x0021, 0x0022, 0x0023, 0x0024, 0x0025, 0x0026, 0x2047, 0x0028, 0x0029, 0x002a, 0x002b, 0x002c, 0x002d, 0x002e, 0x2057,
   0x0030, 0x0031, 0x0032, 0x0033, 0x0034, 0x0035, 0x0036, 0x2067, 0x0038, 0x0039, 0x003a, 0x003b, 0x003c, 0x003d, 0x203e, 0x2077,
   0x0040, 0x0041, 0x0042, 0x0043, 0x0044, 0x0045, 0x0046, 0x2087, 0x0048, 0x0049, 0x004a, 0x004b, 0x004c, 0x004d, 0x004e, 0x2097,
   0x0050, 0x0051, 0x0052, 0x0053, 0x0054, 0x0055, 0x0056, 0x20a7, 0x0058, 0x0059, 0x005a, 0x005b, 0x005c, 0x005d, 0x005e, 0x20b7,
   0x0060, 0x0061, 0x0062, 0x0063, 0x0064, 0x0065, 0x0066, 0x20c7, 0x0068, 0x0069, 0x006a, 0x006b, 0x006c, 0x006d, 0x006e, 0x20d7,
   0x0070, 0x0071, 0x0072, 0x0073, 0x0074, 0x0075, 0x0076, 0x20e7, 0x0078, 0x0079, 0x007a, 0x007b, 0x207c, 0x207d, 0x20be, 0x20f7,
   0x0480, 0x0481, 0x0482, 0x0483, 0x0484, 0x0485, 0x0486, 0x2507, 0x0488, 0x0489, 0x048a, 0x048b, 0x048c, 0x048d, 0x048e, 0x2517,
   0x0490, 0x0491, 0x0492, 0x0493, 0x0494, 0x0495, 0x0496, 0x2527, 0x0498, 0x0499, 0x049a, 0x049b, 0x049c, 0x049d, 0x049e, 0x2537,
   0x04a0, 0x04a1, 0x04a2, 0x04a3, 0x04a4, 0x04a5, 0x04a6, 0x2547, 0x04a8, 0x04a9, 0x04aa, 0x04ab, 0x04ac, 0x04ad, 0x04ae, 0x2557,
   0x04b0, 0x04b1, 0x04b2, 0x04b3, 0x04b4, 0x04b5, 0x04b6, 0x2567, 0x04b8, 0x04b9, 0x04ba, 0x04bb, 0x04bc, 0x04bd, 0x253e, 0x2577,
   0x08c0, 0x08c1, 0x08c2, 0x08c3, 0x08c4, 0x08c5, 0x08c6, 0x2987, 0x08c8, 0x08c9, 0x08ca, 0x08cb, 0x08cc, 0x08cd, 0x08ce, 0x2997,
   0x08d0, 0x08d1, 0x08d2, 0x08d3, 0x08d4, 0x08d5, 0x08d6, 0x29a7, 0x08d8, 0x08d9, 0x08da, 0x08db, 0x08dc, 0x08dd, 0x08de, 0x29b7,
   0x0ce0, 0x0ce1, 0x0ce2, 0x0ce3, 0x0ce4, 0x0ce5, 0x0ce6, 0x2dc7, 0x0ce8, 0x0ce9, 0x0cea, 0x0ceb, 0x0cec, 0x0ced, 0x0cee, 0x2dd7,
   0x10f0, 0x10f1, 0x10f2, 0x10f3, 0x10f4, 0x10f5, 0x10f6, 0x31e7, 0x20f8, 0x20f9, 0x20fa, 0x20fb, 0x257c, 0x257d, 0x29be, 0x41f7,

  /* previous 1s = 3: */

   0x0000, 0x0001, 0x0002, 0x2003, 0x0004, 0x0005, 0x0006, 0x200b, 0x0008, 0x0009, 0x000a, 0x2013, 0x000c, 0x000d, 0x000e, 0x201b,
   0x0010, 0x0011, 0x0012, 0x2023, 0x0014, 0x0015, 0x0016, 0x202b, 0x0018, 0x0019, 0x001a, 0x2033, 0x001c, 0x001d, 0x001e, 0x203b,
   0x0020, 0x0021, 0x0022, 0x2043, 0x0024, 0x0025, 0x0026, 0x204b, 0x0028, 0x0029, 0x002a, 0x2053, 0x002c, 0x002d, 0x002e, 0x205b,
   0x0030, 0x0031, 0x0032, 0x2063, 0x0034, 0x0035, 0x0036, 0x206b, 0x0038, 0x0039, 0x003a, 0x2073, 0x003c, 0x003d, 0x203e, 0x207b,
   0x0040, 0x0041, 0x0042, 0x2083, 0x0044, 0x0045, 0x0046, 0x208b, 0x0048, 0x0049, 0x004a, 0x2093, 0x004c, 0x004d, 0x004e, 0x209b,
   0x0050, 0x0051, 0x0052, 0x20a3, 0x0054, 0x0055, 0x0056, 0x20ab, 0x0058, 0x0059, 0x005a, 0x20b3, 0x005c, 0x005d, 0x005e, 0x20bb,
   0x0060, 0x0061, 0x0062, 0x20c3, 0x0064, 0x0065, 0x0066, 0x20cb, 0x0068, 0x0069, 0x006a, 0x20d3, 0x006c, 0x006d, 0x006e, 0x20db,
   0x0070, 0x0071, 0x0072, 0x20e3, 0x0074, 0x0075, 0x0076, 0x20eb, 0x0078, 0x0079, 0x007a, 0x20f3, 0x207c, 0x207d, 0x20be, 0x40fb,
   0x0480, 0x0481, 0x0482, 0x2503, 0x0484, 0x0485, 0x0486, 0x250b, 0x0488, 0x0489, 0x048a, 0x2513, 0x048c, 0x048d, 0x048e, 0x251b,
   0x0490, 0x0491, 0x0492, 0x2523, 0x0494, 0x0495, 0x0496, 0x252b, 0x0498, 0x0499, 0x049a, 0x2533, 0x049c, 0x049d, 0x049e, 0x253b,
   0x04a0, 0x04a1, 0x04a2, 0x2543, 0x04a4, 0x04a5, 0x04a6, 0x254b, 0x04a8, 0x04a9, 0x04aa, 0x2553, 0x04ac, 0x04ad, 0x04ae, 0x255b,
   0x04b0, 0x04b1, 0x04b2, 0x2563, 0x04b4, 0x04b5, 0x04b6, 0x256b, 0x04b8, 0x04b9, 0x04ba, 0x2573, 0x04bc, 0x04bd, 0x253e, 0x257b,
   0x08c0, 0x08c1, 0x08c2, 0x2983, 0x08c4, 0x08c5, 0x08c6, 0x298b, 0x08c8, 0x08c9, 0x08ca, 0x2993, 0x08cc, 0x08cd, 0x08ce, 0x299b,
   0x08d0, 0x08d1, 0x08d2, 0x29a3, 0x08d4, 0x08d5, 0x08d6, 0x29ab, 0x08d8, 0x08d9, 0x08da, 0x29b3, 0x08dc, 0x08dd, 0x08de, 0x29bb,
   0x0ce0, 0x0ce1, 0x0ce2, 0x2dc3, 0x0ce4, 0x0ce5, 0x0ce6, 0x2dcb, 0x0ce8, 0x0ce9, 0x0cea, 0x2dd3, 0x0cec, 0x0ced, 0x0cee, 0x2ddb,
   0x10f0, 0x10f1, 0x10f2, 0x31e3, 0x10f4, 0x10f5, 0x10f6, 0x31eb, 0x20f8, 0x20f9, 0x20fa, 0x41f3, 0x257c, 0x257d, 0x29be, 0x46fb,

  /* previous 1s = 4: */

   0x0000, 0x2001, 0x0002, 0x2005, 0x0004, 0x2009, 0x0006, 0x200d, 0x0008, 0x2011, 0x000a, 0x2015, 0x000c, 0x2019, 0x000e, 0x201d,
   0x0010, 0x2021, 0x0012, 0x2025, 0x0014, 0x2029, 0x0016, 0x202d, 0x0018, 0x2031, 0x001a, 0x2035, 0x001c, 0x2039, 0x001e, 0x203d,
   0x0020, 0x2041, 0x0022, 0x2045, 0x0024, 0x2049, 0x0026, 0x204d, 0x0028, 0x2051, 0x002a, 0x2055, 0x002c, 0x2059, 0x002e, 0x205d,
   0x0030, 0x2061, 0x0032, 0x2065, 0x0034, 0x2069, 0x0036, 0x206d, 0x0038, 0x2071, 0x003a, 0x2075, 0x003c, 0x2079, 0x203e, 0x407d,
   0x0040, 0x2081, 0x0042, 0x2085, 0x0044, 0x2089, 0x0046, 0x208d, 0x0048, 0x2091, 0x004a, 0x2095, 0x004c, 0x2099, 0x004e, 0x209d,
   0x0050, 0x20a1, 0x0052, 0x20a5, 0x0054, 0x20a9, 0x0056, 0x20ad, 0x0058, 0x20b1, 0x005a, 0x20b5, 0x005c, 0x20b9, 0x005e, 0x20bd,
   0x0060, 0x20c1, 0x0062, 0x20c5, 0x0064, 0x20c9, 0x0066, 0x20cd, 0x0068, 0x20d1, 0x006a, 0x20d5, 0x006c, 0x20d9, 0x006e, 0x20dd,
   0x0070, 0x20e1, 0x0072, 0x20e5, 0x0074, 0x20e9, 0x0076, 0x20ed, 0x0078, 0x20f1, 0x007a, 0x20f5, 0x207c, 0x40f9, 0x20be, 0x417d,
   0x0480, 0x2501, 0x0482, 0x2505, 0x0484, 0x2509, 0x0486, 0x250d, 0x0488, 0x2511, 0x048a, 0x2515, 0x048c, 0x2519, 0x048e, 0x251d,
   0x0490, 0x2521, 0x0492, 0x2525, 0x0494, 0x2529, 0x0496, 0x252d, 0x0498, 0x2531, 0x049a, 0x2535, 0x049c, 0x2539, 0x049e, 0x253d,
   0x04a0, 0x2541, 0x04a2, 0x2545, 0x04a4, 0x2549, 0x04a6, 0x254d, 0x04a8, 0x2551, 0x04aa, 0x2555, 0x04ac, 0x2559, 0x04ae, 0x255d,
   0x04b0, 0x2561, 0x04b2, 0x2565, 0x04b4, 0x2569, 0x04b6, 0x256d, 0x04b8, 0x2571, 0x04ba, 0x2575, 0x04bc, 0x2579, 0x253e, 0x467d,
   0x08c0, 0x2981, 0x08c2, 0x2985, 0x08c4, 0x2989, 0x08c6, 0x298d, 0x08c8, 0x2991, 0x08ca, 0x2995, 0x08cc, 0x2999, 0x08ce, 0x299d,
   0x08d0, 0x29a1, 0x08d2, 0x29a5, 0x08d4, 0x29a9, 0x08d6, 0x29ad, 0x08d8, 0x29b1, 0x08da, 0x29b5, 0x08dc, 0x29b9, 0x08de, 0x29bd,
   0x0ce0, 0x2dc1, 0x0ce2, 0x2dc5, 0x0ce4, 0x2dc9, 0x0ce6, 0x2dcd, 0x0ce8, 0x2dd1, 0x0cea, 0x2dd5, 0x0cec, 0x2dd9, 0x0cee, 0x2ddd,
   0x10f0, 0x31e1, 0x10f2, 0x31e5, 0x10f4, 0x31e9, 0x10f6, 0x31ed, 0x20f8, 0x41f1, 0x20fa, 0x41f5, 0x257c, 0x46f9, 0x29be, 0x4b7d
  };
  
  /* hdlc_bitstuff_byte
   * perform HDLC bitstuffing for one input byte (8 bits, LSB first)
   * parameters:
   *	cin	input byte
   *	ones	number of trailing '1' bits in result before this step

   *	iwb	pointer to output buffer structure
   *		(write semaphore must be held)

   * return value:
   *	number of trailing '1' bits in result after this step
   */
  
  static inline int hdlc_bitstuff_byte(struct isowbuf_t *iwb, unsigned char cin,

  				     int ones)

  {
  	u16 stuff;
  	int shiftinc, newones;
  
  	/* get stuffing information for input byte
  	 * value: bit  9.. 0 = result bits
  	 *        bit 12..10 = number of trailing '1' bits in result
  	 *        bit 14..13 = number of bits added by stuffing
  	 */
  	stuff = stufftab[256 * ones + cin];
  	shiftinc = (stuff >> 13) & 3;
  	newones = (stuff >> 10) & 7;
  	stuff &= 0x3ff;
  
  	/* append stuffed byte to output stream */
  	isowbuf_putbits(iwb, stuff, 8 + shiftinc);
  	return newones;
  }
  
  /* hdlc_buildframe
   * Perform HDLC framing with bitstuffing on a byte buffer
   * The input buffer is regarded as a sequence of bits, starting with the least
   * significant bit of the first byte and ending with the most significant bit
   * of the last byte. A 16 bit FCS is appended as defined by RFC 1662.
   * Whenever five consecutive '1' bits appear in the resulting bit sequence, a
   * '0' bit is inserted after them.
   * The resulting bit string and a closing flag pattern (PPP_FLAG, '01111110')
   * are appended to the output buffer starting at the given bit position, which
   * is assumed to already contain a leading flag.
   * The output buffer must have sufficient length; count + count/5 + 6 bytes
   * starting at *out are safe and are verified to be present.
   * parameters:
   *	in	input buffer
   *	count	number of bytes in input buffer

   *	iwb	pointer to output buffer structure
   *		(write semaphore must be held)

   * return value:
   *	position of end of packet in output buffer on success,
   *	-EAGAIN if write semaphore busy or buffer full
   */
  
  static inline int hdlc_buildframe(struct isowbuf_t *iwb,

  				  unsigned char *in, int count)

  {
  	int ones;
  	u16 fcs;
  	int end;
  	unsigned char c;
  
  	if (isowbuf_freebytes(iwb) < count + count / 5 + 6 ||
  	    !isowbuf_startwrite(iwb)) {

  		gig_dbg(DEBUG_ISO, "%s: %d bytes free -> -EAGAIN",
  			__func__, isowbuf_freebytes(iwb));

  		return -EAGAIN;
  	}

  	dump_bytes(DEBUG_STREAM_DUMP, "snd data", in, count);

  
  	/* bitstuff and checksum input data */
  	fcs = PPP_INITFCS;
  	ones = 0;
  	while (count-- > 0) {
  		c = *in++;
  		ones = hdlc_bitstuff_byte(iwb, c, ones);
  		fcs = crc_ccitt_byte(fcs, c);
  	}

  	/* bitstuff and append FCS
  	 * (complemented, least significant byte first) */

  	fcs ^= 0xffff;
  	ones = hdlc_bitstuff_byte(iwb, fcs & 0x00ff, ones);
  	ones = hdlc_bitstuff_byte(iwb, (fcs >> 8) & 0x00ff, ones);
  
  	/* put closing flag and repeat byte for flag idle */
  	isowbuf_putflag(iwb);
  	end = isowbuf_donewrite(iwb);

  	return end;
  }
  
  /* trans_buildframe
   * Append a block of 'transparent' data to the output buffer,
   * inverting the bytes.
   * The output buffer must have sufficient length; count bytes
   * starting at *out are safe and are verified to be present.
   * parameters:
   *	in	input buffer
   *	count	number of bytes in input buffer

   *	iwb	pointer to output buffer structure
   *		(write semaphore must be held)

   * return value:
   *	position of end of packet in output buffer on success,
   *	-EAGAIN if write semaphore busy or buffer full
   */
  
  static inline int trans_buildframe(struct isowbuf_t *iwb,
  				   unsigned char *in, int count)
  {
  	int write;
  	unsigned char c;
  
  	if (unlikely(count <= 0))

  		return iwb->write;

  
  	if (isowbuf_freebytes(iwb) < count ||
  	    !isowbuf_startwrite(iwb)) {

  		gig_dbg(DEBUG_ISO, "can't put %d bytes", count);

  		return -EAGAIN;
  	}

  	gig_dbg(DEBUG_STREAM, "put %d bytes", count);

  	dump_bytes(DEBUG_STREAM_DUMP, "snd data", in, count);

  	write = iwb->write;

  	do {

  		c = bitrev8(*in++);

  		iwb->data[write++] = c;
  		write %= BAS_OUTBUFSIZE;
  	} while (--count > 0);

  	iwb->write = write;

  	iwb->idle = c;
  
  	return isowbuf_donewrite(iwb);
  }
  
  int gigaset_isoc_buildframe(struct bc_state *bcs, unsigned char *in, int len)
  {
  	int result;
  
  	switch (bcs->proto2) {

  	case L2_HDLC:

  		result = hdlc_buildframe(bcs->hw.bas->isooutbuf, in, len);

  		gig_dbg(DEBUG_ISO, "%s: %d bytes HDLC -> %d",
  			__func__, len, result);

  		break;
  	default:			/* assume transparent */
  		result = trans_buildframe(bcs->hw.bas->isooutbuf, in, len);

  		gig_dbg(DEBUG_ISO, "%s: %d bytes trans -> %d",
  			__func__, len, result);

  	}
  	return result;
  }
  
  /* hdlc_putbyte
   * append byte c to current skb of B channel structure *bcs, updating fcs
   */
  static inline void hdlc_putbyte(unsigned char c, struct bc_state *bcs)
  {

  	bcs->rx_fcs = crc_ccitt_byte(bcs->rx_fcs, c);
  	if (bcs->rx_skb == NULL)

  		/* skipping */
  		return;

  	if (bcs->rx_skb->len >= bcs->rx_bufsize) {

  		dev_warn(bcs->cs->dev, "received oversized packet discarded
  ");

  		bcs->hw.bas->giants++;

  		dev_kfree_skb_any(bcs->rx_skb);
  		bcs->rx_skb = NULL;

  		return;
  	}

  	*__skb_put(bcs->rx_skb, 1) = c;

  }
  
  /* hdlc_flush
   * drop partial HDLC data packet
   */
  static inline void hdlc_flush(struct bc_state *bcs)
  {
  	/* clear skb or allocate new if not skipping */

  	if (bcs->rx_skb != NULL)
  		skb_trim(bcs->rx_skb, 0);
  	else
  		gigaset_new_rx_skb(bcs);

  
  	/* reset packet state */

  	bcs->rx_fcs = PPP_INITFCS;

  }
  
  /* hdlc_done
   * process completed HDLC data packet
   */
  static inline void hdlc_done(struct bc_state *bcs)
  {

  	struct cardstate *cs = bcs->cs;

  	struct sk_buff *procskb;

  	unsigned int len;

  
  	if (unlikely(bcs->ignore)) {
  		bcs->ignore--;
  		hdlc_flush(bcs);
  		return;
  	}

  	procskb = bcs->rx_skb;

  	if (procskb == NULL) {

  		/* previous error */

  		gig_dbg(DEBUG_ISO, "%s: skb=NULL", __func__);

  		gigaset_isdn_rcv_err(bcs);

  	} else if (procskb->len < 2) {

  		dev_notice(cs->dev, "received short frame (%d octets)
  ",

  			   procskb->len);

  		bcs->hw.bas->runts++;

  		dev_kfree_skb_any(procskb);

  		gigaset_isdn_rcv_err(bcs);

  	} else if (bcs->rx_fcs != PPP_GOODFCS) {
  		dev_notice(cs->dev, "frame check error
  ");

  		bcs->hw.bas->fcserrs++;

  		dev_kfree_skb_any(procskb);

  		gigaset_isdn_rcv_err(bcs);

  	} else {

  		len = procskb->len;
  		__skb_trim(procskb, len -= 2);	/* subtract FCS */
  		gig_dbg(DEBUG_ISO, "%s: good frame (%d octets)", __func__, len);

  		dump_bytes(DEBUG_STREAM_DUMP,

  			   "rcv data", procskb->data, len);
  		bcs->hw.bas->goodbytes += len;
  		gigaset_skb_rcvd(bcs, procskb);

  	}

  	gigaset_new_rx_skb(bcs);
  	bcs->rx_fcs = PPP_INITFCS;

  }
  
  /* hdlc_frag
   * drop HDLC data packet with non-integral last byte
   */
  static inline void hdlc_frag(struct bc_state *bcs, unsigned inbits)
  {
  	if (unlikely(bcs->ignore)) {
  		bcs->ignore--;
  		hdlc_flush(bcs);
  		return;
  	}

  	dev_notice(bcs->cs->dev, "received partial byte (%d bits)
  ", inbits);

  	bcs->hw.bas->alignerrs++;

  	gigaset_isdn_rcv_err(bcs);

  	__skb_trim(bcs->rx_skb, 0);
  	bcs->rx_fcs = PPP_INITFCS;

  }
  
  /* bit counts lookup table for HDLC bit unstuffing
   * index: input byte
   * value: bit 0..3 = number of consecutive '1' bits starting from LSB
   *        bit 4..6 = number of consecutive '1' bits starting from MSB
   *		     (replacing 8 by 7 to make it fit; the algorithm won't care)
   *        bit 7 set if there are 5 or more "interior" consecutive '1' bits
   */

  static const unsigned char bitcounts[256] = {

    0x00, 0x01, 0x00, 0x02, 0x00, 0x01, 0x00, 0x03, 0x00, 0x01, 0x00, 0x02, 0x00, 0x01, 0x00, 0x04,
    0x00, 0x01, 0x00, 0x02, 0x00, 0x01, 0x00, 0x03, 0x00, 0x01, 0x00, 0x02, 0x00, 0x01, 0x00, 0x05,
    0x00, 0x01, 0x00, 0x02, 0x00, 0x01, 0x00, 0x03, 0x00, 0x01, 0x00, 0x02, 0x00, 0x01, 0x00, 0x04,
    0x00, 0x01, 0x00, 0x02, 0x00, 0x01, 0x00, 0x03, 0x00, 0x01, 0x00, 0x02, 0x00, 0x01, 0x80, 0x06,
    0x00, 0x01, 0x00, 0x02, 0x00, 0x01, 0x00, 0x03, 0x00, 0x01, 0x00, 0x02, 0x00, 0x01, 0x00, 0x04,
    0x00, 0x01, 0x00, 0x02, 0x00, 0x01, 0x00, 0x03, 0x00, 0x01, 0x00, 0x02, 0x00, 0x01, 0x00, 0x05,
    0x00, 0x01, 0x00, 0x02, 0x00, 0x01, 0x00, 0x03, 0x00, 0x01, 0x00, 0x02, 0x00, 0x01, 0x00, 0x04,
    0x00, 0x01, 0x00, 0x02, 0x00, 0x01, 0x00, 0x03, 0x00, 0x01, 0x00, 0x02, 0x80, 0x81, 0x80, 0x07,
    0x10, 0x11, 0x10, 0x12, 0x10, 0x11, 0x10, 0x13, 0x10, 0x11, 0x10, 0x12, 0x10, 0x11, 0x10, 0x14,
    0x10, 0x11, 0x10, 0x12, 0x10, 0x11, 0x10, 0x13, 0x10, 0x11, 0x10, 0x12, 0x10, 0x11, 0x10, 0x15,
    0x10, 0x11, 0x10, 0x12, 0x10, 0x11, 0x10, 0x13, 0x10, 0x11, 0x10, 0x12, 0x10, 0x11, 0x10, 0x14,
    0x10, 0x11, 0x10, 0x12, 0x10, 0x11, 0x10, 0x13, 0x10, 0x11, 0x10, 0x12, 0x10, 0x11, 0x90, 0x16,
    0x20, 0x21, 0x20, 0x22, 0x20, 0x21, 0x20, 0x23, 0x20, 0x21, 0x20, 0x22, 0x20, 0x21, 0x20, 0x24,
    0x20, 0x21, 0x20, 0x22, 0x20, 0x21, 0x20, 0x23, 0x20, 0x21, 0x20, 0x22, 0x20, 0x21, 0x20, 0x25,
    0x30, 0x31, 0x30, 0x32, 0x30, 0x31, 0x30, 0x33, 0x30, 0x31, 0x30, 0x32, 0x30, 0x31, 0x30, 0x34,
    0x40, 0x41, 0x40, 0x42, 0x40, 0x41, 0x40, 0x43, 0x50, 0x51, 0x50, 0x52, 0x60, 0x61, 0x70, 0x78
  };
  
  /* hdlc_unpack

   * perform HDLC frame processing (bit unstuffing, flag detection, FCS
   * calculation) on a sequence of received data bytes (8 bits each, LSB first)

   * pass on successfully received, complete frames as SKBs via gigaset_skb_rcvd
   * notify of errors via gigaset_isdn_rcv_err

   * tally frames, errors etc. in BC structure counters
   * parameters:
   *	src	received data
   *	count	number of received bytes
   *	bcs	receiving B channel structure
   */
  static inline void hdlc_unpack(unsigned char *src, unsigned count,

  			       struct bc_state *bcs)

  {

  	struct bas_bc_state *ubc = bcs->hw.bas;

  	int inputstate;
  	unsigned seqlen, inbyte, inbits;

  	/* load previous state:
  	 * inputstate = set of flag bits:

  	 * - INS_flag_hunt: no complete opening flag received since connection
  	 *                  setup or last abort
  	 * - INS_have_data: at least one complete data byte received since last
  	 *                  flag
  	 * seqlen = number of consecutive '1' bits in last 7 input stream bits
  	 *          (0..7)

  	 * inbyte = accumulated partial data byte (if !INS_flag_hunt)
  	 * inbits = number of valid bits in inbyte, starting at LSB (0..6)
  	 */
  	inputstate = bcs->inputstate;
  	seqlen = ubc->seqlen;
  	inbyte = ubc->inbyte;
  	inbits = ubc->inbits;
  
  	/* bit unstuffing a byte a time
  	 * Take your time to understand this; it's straightforward but tedious.
  	 * The "bitcounts" lookup table is used to speed up the counting of
  	 * leading and trailing '1' bits.
  	 */
  	while (count--) {
  		unsigned char c = *src++;
  		unsigned char tabentry = bitcounts[c];
  		unsigned lead1 = tabentry & 0x0f;
  		unsigned trail1 = (tabentry >> 4) & 0x0f;
  
  		seqlen += lead1;
  
  		if (unlikely(inputstate & INS_flag_hunt)) {
  			if (c == PPP_FLAG) {
  				/* flag-in-one */
  				inputstate &= ~(INS_flag_hunt | INS_have_data);
  				inbyte = 0;
  				inbits = 0;
  			} else if (seqlen == 6 && trail1 != 7) {
  				/* flag completed & not followed by abort */
  				inputstate &= ~(INS_flag_hunt | INS_have_data);
  				inbyte = c >> (lead1 + 1);
  				inbits = 7 - lead1;
  				if (trail1 >= 8) {

  					/* interior stuffing:
  					 * omitting the MSB handles most cases,
  					 * correct the incorrectly handled
  					 * cases individually */

  					inbits--;

  					switch (c) {
  					case 0xbe:
  						inbyte = 0x3f;
  						break;
  					}
  				}
  			}
  			/* else: continue flag-hunting */
  		} else if (likely(seqlen < 5 && trail1 < 7)) {
  			/* streamlined case: 8 data bits, no stuffing */
  			inbyte |= c << inbits;
  			hdlc_putbyte(inbyte & 0xff, bcs);
  			inputstate |= INS_have_data;
  			inbyte >>= 8;
  			/* inbits unchanged */
  		} else if (likely(seqlen == 6 && inbits == 7 - lead1 &&
  				  trail1 + 1 == inbits &&
  				  !(inputstate & INS_have_data))) {
  			/* streamlined case: flag idle - state unchanged */
  		} else if (unlikely(seqlen > 6)) {
  			/* abort sequence */
  			ubc->aborts++;
  			hdlc_flush(bcs);
  			inputstate |= INS_flag_hunt;
  		} else if (seqlen == 6) {

  			/* closing flag, including (6 - lead1) '1's
  			 * and one '0' from inbits */

  			if (inbits > 7 - lead1) {
  				hdlc_frag(bcs, inbits + lead1 - 7);
  				inputstate &= ~INS_have_data;
  			} else {
  				if (inbits < 7 - lead1)

  					ubc->stolen0s++;

  				if (inputstate & INS_have_data) {
  					hdlc_done(bcs);
  					inputstate &= ~INS_have_data;
  				}
  			}
  
  			if (c == PPP_FLAG) {
  				/* complete flag, LSB overlaps preceding flag */

  				ubc->shared0s++;

  				inbits = 0;
  				inbyte = 0;
  			} else if (trail1 != 7) {
  				/* remaining bits */
  				inbyte = c >> (lead1 + 1);
  				inbits = 7 - lead1;
  				if (trail1 >= 8) {

  					/* interior stuffing:
  					 * omitting the MSB handles most cases,
  					 * correct the incorrectly handled
  					 * cases individually */

  					inbits--;

  					switch (c) {
  					case 0xbe:
  						inbyte = 0x3f;
  						break;
  					}
  				}
  			} else {

  				/* abort sequence follows,
  				 * skb already empty anyway */

  				ubc->aborts++;
  				inputstate |= INS_flag_hunt;
  			}
  		} else { /* (seqlen < 6) && (seqlen == 5 || trail1 >= 7) */
  
  			if (c == PPP_FLAG) {
  				/* complete flag */
  				if (seqlen == 5)
  					ubc->stolen0s++;
  				if (inbits) {
  					hdlc_frag(bcs, inbits);
  					inbits = 0;
  					inbyte = 0;
  				} else if (inputstate & INS_have_data)
  					hdlc_done(bcs);
  				inputstate &= ~INS_have_data;
  			} else if (trail1 == 7) {
  				/* abort sequence */
  				ubc->aborts++;
  				hdlc_flush(bcs);
  				inputstate |= INS_flag_hunt;
  			} else {
  				/* stuffed data */
  				if (trail1 < 7) { /* => seqlen == 5 */

  					/* stuff bit at position lead1,
  					 * no interior stuffing */

  					unsigned char mask = (1 << lead1) - 1;
  					c = (c & mask) | ((c & ~mask) >> 1);
  					inbyte |= c << inbits;
  					inbits += 7;
  				} else if (seqlen < 5) { /* trail1 >= 8 */

  					/* interior stuffing:
  					 * omitting the MSB handles most cases,
  					 * correct the incorrectly handled
  					 * cases individually */

  					switch (c) {
  					case 0xbe:
  						c = 0x7e;
  						break;
  					}
  					inbyte |= c << inbits;
  					inbits += 7;
  				} else { /* seqlen == 5 && trail1 >= 8 */

  					/* stuff bit at lead1 *and* interior
  					 * stuffing -- unstuff individually */
  					switch (c) {

  					case 0x7d:
  						c = 0x3f;
  						break;
  					case 0xbe:
  						c = 0x3f;
  						break;
  					case 0x3e:
  						c = 0x1f;
  						break;
  					case 0x7c:
  						c = 0x3e;
  						break;
  					}
  					inbyte |= c << inbits;
  					inbits += 6;
  				}
  				if (inbits >= 8) {
  					inbits -= 8;
  					hdlc_putbyte(inbyte & 0xff, bcs);
  					inputstate |= INS_have_data;
  					inbyte >>= 8;
  				}
  			}
  		}
  		seqlen = trail1 & 7;
  	}
  
  	/* save new state */
  	bcs->inputstate = inputstate;
  	ubc->seqlen = seqlen;
  	ubc->inbyte = inbyte;
  	ubc->inbits = inbits;
  }
  
  /* trans_receive

   * pass on received USB frame transparently as SKB via gigaset_skb_rcvd

   * invert bytes
   * tally frames, errors etc. in BC structure counters
   * parameters:
   *	src	received data
   *	count	number of received bytes
   *	bcs	receiving B channel structure
   */
  static inline void trans_receive(unsigned char *src, unsigned count,

  				 struct bc_state *bcs)

  {
  	struct sk_buff *skb;
  	int dobytes;
  	unsigned char *dst;
  
  	if (unlikely(bcs->ignore)) {
  		bcs->ignore--;

  		return;
  	}

  	skb = bcs->rx_skb;

  	if (skb == NULL) {

  		skb = gigaset_new_rx_skb(bcs);

  		if (skb == NULL)
  			return;
  	}

  	dobytes = bcs->rx_bufsize - skb->len;

  	while (count > 0) {
  		dst = skb_put(skb, count < dobytes ? count : dobytes);
  		while (count > 0 && dobytes > 0) {

  			*dst++ = bitrev8(*src++);

  			count--;
  			dobytes--;
  		}
  		if (dobytes == 0) {

  			dump_bytes(DEBUG_STREAM_DUMP,
  				   "rcv data", skb->data, skb->len);

  			bcs->hw.bas->goodbytes += skb->len;

  			gigaset_skb_rcvd(bcs, skb);

  			skb = gigaset_new_rx_skb(bcs);
  			if (skb == NULL)

  				return;

  			dobytes = bcs->rx_bufsize;

  		}
  	}
  }

  void gigaset_isoc_receive(unsigned char *src, unsigned count,
  			  struct bc_state *bcs)

  {
  	switch (bcs->proto2) {

  	case L2_HDLC:

  		hdlc_unpack(src, count, bcs);
  		break;
  	default:		/* assume transparent */
  		trans_receive(src, count, bcs);
  	}
  }
  
  /* == data input =========================================================== */

  /* process a block of received bytes in command mode (mstate != MS_LOCKED)
   * Append received bytes to the command response buffer and forward them
   * line by line to the response handler.
   * Note: Received lines may be terminated by CR, LF, or CR LF, which will be
   * removed before passing the line to the response handler.
   */

  static void cmd_loop(unsigned char *src, int numbytes, struct inbuf_t *inbuf)
  {
  	struct cardstate *cs = inbuf->cs;
  	unsigned cbytes      = cs->cbytes;

  	unsigned char c;

  
  	while (numbytes--) {

  		c = *src++;
  		switch (c) {

  		case '
  ':

  			if (cbytes == 0 && cs->respdata[0] == '\r') {
  				/* collapse LF with preceding CR */
  				cs->respdata[0] = 0;
  				break;
  			}
  			/* --v-- fall through --v-- */
  		case '\r':
  			/* end of message line, pass to response handler */
  			if (cbytes >= MAX_RESP_SIZE) {
  				dev_warn(cs->dev, "response too large (%d)
  ",
  					 cbytes);
  				cbytes = MAX_RESP_SIZE;
  			}

  			cs->cbytes = cbytes;

  			gigaset_dbg_buffer(DEBUG_TRANSCMD, "received response",
  					   cbytes, cs->respdata);

  			gigaset_handle_modem_response(cs);
  			cbytes = 0;

  
  			/* store EOL byte for CRLF collapsing */
  			cs->respdata[0] = c;

  			break;
  		default:

  			/* append to line buffer if possible */
  			if (cbytes < MAX_RESP_SIZE)
  				cs->respdata[cbytes] = c;
  			cbytes++;

  		}
  	}
  
  	/* save state */
  	cs->cbytes = cbytes;
  }
  
  
  /* process a block of data received through the control channel
   */
  void gigaset_isoc_input(struct inbuf_t *inbuf)
  {
  	struct cardstate *cs = inbuf->cs;
  	unsigned tail, head, numbytes;
  	unsigned char *src;

  	head = inbuf->head;
  	while (head != (tail = inbuf->tail)) {

  		gig_dbg(DEBUG_INTR, "buffer state: %u -> %u", head, tail);

  		if (head > tail)
  			tail = RBUFSIZE;
  		src = inbuf->data + head;
  		numbytes = tail - head;

  		gig_dbg(DEBUG_INTR, "processing %u bytes", numbytes);

  		if (cs->mstate == MS_LOCKED) {

  			gigaset_dbg_buffer(DEBUG_LOCKCMD, "received response",

  					   numbytes, src);

  			gigaset_if_receive(inbuf->cs, src, numbytes);
  		} else {

  			cmd_loop(src, numbytes, inbuf);
  		}
  
  		head += numbytes;
  		if (head == RBUFSIZE)
  			head = 0;

  		gig_dbg(DEBUG_INTR, "setting head to %u", head);

  		inbuf->head = head;

  	}
  }
  
  
  /* == data output ========================================================== */

  /**
   * gigaset_isoc_send_skb() - queue an skb for sending
   * @bcs:	B channel descriptor structure.
   * @skb:	data to send.
   *

   * Called by LL to queue an skb for sending, and start transmission if

   * necessary.

   * Once the payload data has been transmitted completely, gigaset_skb_sent()

   * will be called with the skb's link layer header preserved.

   *
   * Return value:
   *	number of bytes accepted for sending (skb->len) if ok,
   *	error code < 0 (eg. -ENODEV) on error

   */
  int gigaset_isoc_send_skb(struct bc_state *bcs, struct sk_buff *skb)
  {

  	int len = skb->len;

  	unsigned long flags;

  	spin_lock_irqsave(&bcs->cs->lock, flags);
  	if (!bcs->cs->connected) {
  		spin_unlock_irqrestore(&bcs->cs->lock, flags);
  		return -ENODEV;
  	}

  	skb_queue_tail(&bcs->squeue, skb);

  	gig_dbg(DEBUG_ISO, "%s: skb queued, qlen=%d",
  		__func__, skb_queue_len(&bcs->squeue));

  
  	/* tasklet submits URB if necessary */

  	tasklet_schedule(&bcs->hw.bas->sent_tasklet);

  	spin_unlock_irqrestore(&bcs->cs->lock, flags);

  
  	return len;	/* ok so far */
  }