[PATCH] isdn4linux: Siemens Gigaset drivers - isochronous data handler

And: Tilman Schmidt <tilman@imap.cc>

This patch adds the payload data handler for the connection-specific module
"bas_gigaset".  It contains the code for handling isochronous data transfers,
HDLC framing and flow control.

Signed-off-by: Hansjoerg Lipp <hjlipp@web.de>
Signed-off-by: Tilman Schmidt <tilman@imap.cc>
Cc: Karsten Keil <kkeil@suse.de>
Cc: Greg KH <greg@kroah.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 1009 insertions, 0 deletions

diff --git a/drivers/isdn/gigaset/isocdata.c b/drivers/isdn/gigaset/isocdata.c
new file mode 100644
index 0000000..5744eb9
--- /dev/null
+++ b/drivers/isdn/gigaset/isocdata.c
@@ -0,0 +1,1009 @@
+/*
+ * 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.
+ * =====================================================================
+ * ToDo: ...
+ * =====================================================================
+ * Version: $Id: isocdata.c,v 1.2.2.5 2005/11/13 23:05:19 hjlipp Exp $
+ * =====================================================================
+ */
+
+#include "gigaset.h"
+#include <linux/crc-ccitt.h>
+
+/* access methods for isowbuf_t */
+/* ============================ */
+
+/* initialize buffer structure
+ */
+void gigaset_isowbuf_init(struct isowbuf_t *iwb, unsigned char idle)
+{
+	atomic_set(&iwb->read, 0);
+	atomic_set(&iwb->nextread, 0);
+	atomic_set(&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 = atomic_read(&iwb->read);
+	write = atomic_read(&iwb->write);
+	if ((freebytes = read - write) > 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;
+	}
+}
+
+/* compare two offsets within the buffer
+ * The buffer is seen as circular, with the read position as start
+ * returns -1/0/1 if position a </=/> position b without crossing 'read'
+ */
+static inline int isowbuf_poscmp(struct isowbuf_t *iwb, int a, int b)
+{
+	int read;
+	if (a == b)
+		return 0;
+	read = atomic_read(&iwb->read);
+	if (a < b) {
+		if (a < read && read <= b)
+			return +1;
+		else
+			return -1;
+	} else {
+		if (b < read && read <= a)
+			return -1;
+		else
+			return +1;
+	}
+}
+
+/* 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);
+		dbg(DEBUG_ISO,
+		    "%s: couldn't acquire iso write semaphore", __func__);
+		return 0;
+	}
+#ifdef CONFIG_GIGASET_DEBUG
+	dbg(DEBUG_ISO,
+	    "%s: acquired iso write semaphore, data[write]=%02x, nbits=%d",
+	    __func__, iwb->data[atomic_read(&iwb->write)], iwb->wbits);
+#endif
+	return 1;
+}
+
+/* finish writing
+ * release the write semaphore and update the maximum buffer fill level
+ * returns the current write position
+ */
+static inline int isowbuf_donewrite(struct isowbuf_t *iwb)
+{
+	int write = atomic_read(&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 = atomic_read(&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;
+	atomic_set(&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 = atomic_read(&iwb->write);
+	iwb->idle = iwb->data[write];
+	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 = atomic_read(&iwb->nextread);
+	write = atomic_read(&iwb->write);
+	if (likely(read == write)) {
+		//dbg(DEBUG_STREAM, "%s: send buffer empty", __func__);
+		/* return idle frame */
+		return read < BAS_OUTBUFPAD ?
+		        BAS_OUTBUFSIZE : read - BAS_OUTBUFPAD;
+	}
+
+	limit = read + size;
+	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)) {
+		err("invalid size %d", size);
+		return -EINVAL;
+	}
+	src = atomic_read(&iwb->read);
+	if (unlikely(limit > BAS_OUTBUFSIZE + BAS_OUTBUFPAD ||
+		     (read < src && limit >= src))) {
+		err("isoc write buffer frame reservation violated");
+		return -EFAULT;
+	}
+#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 */
+			if (limit >= (write = atomic_read(&iwb->write))) {
+				pbyte = iwb->data[write]; /* save partial byte */
+				limit = write + BAS_OUTBUFPAD;
+				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;
+				}
+				dbg(DEBUG_STREAM, "%s: restoring %02x at %d",
+				    __func__, pbyte, limit);
+				iwb->data[limit] = pbyte; /* restore partial byte */
+				atomic_set(&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;
+		}
+	}
+	atomic_set(&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];
+	static const char hexdigit[] = "0123456789abcdef";
+	int i = 0;
+	IFNULLRET(tag);
+	IFNULLRET(bytes);
+	while (count-- > 0) {
+		if (i > sizeof(dbgline) - 4) {
+			dbgline[i] = '\0';
+			dbg(level, "%s:%s", tag, dbgline);
+			i = 0;
+		}
+		c = *bytes++;
+		dbgline[i] = (i && !(i % 12)) ? '-' : ' ';
+		i++;
+		dbgline[i++] = hexdigit[(c >> 4) & 0x0f];
+		dbgline[i++] = hexdigit[c & 0x0f];
+	}
+	dbgline[i] = '\0';
+	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 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)) {
+		dbg(DEBUG_ISO, "%s: %d bytes free -> -EAGAIN",
+		    __func__, isowbuf_freebytes(iwb));
+		return -EAGAIN;
+	}
+
+	dump_bytes(DEBUG_STREAM, "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);
+	dump_bytes(DEBUG_STREAM_DUMP, "isowbuf", iwb->data, end + 1);
+	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 atomic_read(&iwb->write); /* better ideas? */
+
+	if (isowbuf_freebytes(iwb) < count ||
+	    !isowbuf_startwrite(iwb)) {
+		dbg(DEBUG_ISO, "can't put %d bytes", count);
+		return -EAGAIN;
+	}
+
+	dbg(DEBUG_STREAM, "put %d bytes", count);
+	write = atomic_read(&iwb->write);
+	do {
+		c = gigaset_invtab[*in++];
+		iwb->data[write++] = c;
+		write %= BAS_OUTBUFSIZE;
+	} while (--count > 0);
+	atomic_set(&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 ISDN_PROTO_L2_HDLC:
+		result = hdlc_buildframe(bcs->hw.bas->isooutbuf, in, len);
+		dbg(DEBUG_ISO, "%s: %d bytes HDLC -> %d", __func__, len, result);
+		break;
+	default:			/* assume transparent */
+		result = trans_buildframe(bcs->hw.bas->isooutbuf, in, len);
+		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->fcs = crc_ccitt_byte(bcs->fcs, c);
+	if (unlikely(bcs->skb == NULL)) {
+		/* skipping */
+		return;
+	}
+	if (unlikely(bcs->skb->len == SBUFSIZE)) {
+		warn("received oversized packet discarded");
+		bcs->hw.bas->giants++;
+		dev_kfree_skb_any(bcs->skb);
+		bcs->skb = NULL;
+		return;
+	}
+	*gigaset_skb_put_quick(bcs->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 (likely(bcs->skb != NULL))
+		skb_trim(bcs->skb, 0);
+	else if (!bcs->ignore) {
+		if ((bcs->skb = dev_alloc_skb(SBUFSIZE + HW_HDR_LEN)) != NULL)
+			skb_reserve(bcs->skb, HW_HDR_LEN);
+		else
+			err("could not allocate skb");
+	}
+
+	/* reset packet state */
+	bcs->fcs = PPP_INITFCS;
+}
+
+/* hdlc_done
+ * process completed HDLC data packet
+ */
+static inline void hdlc_done(struct bc_state *bcs)
+{
+	struct sk_buff *procskb;
+
+	if (unlikely(bcs->ignore)) {
+		bcs->ignore--;
+		hdlc_flush(bcs);
+		return;
+	}
+
+	if ((procskb = bcs->skb) == NULL) {
+		/* previous error */
+		dbg(DEBUG_ISO, "%s: skb=NULL", __func__);
+		gigaset_rcv_error(NULL, bcs->cs, bcs);
+	} else if (procskb->len < 2) {
+		notice("received short frame (%d octets)", procskb->len);
+		bcs->hw.bas->runts++;
+		gigaset_rcv_error(procskb, bcs->cs, bcs);
+	} else if (bcs->fcs != PPP_GOODFCS) {
+		notice("frame check error (0x%04x)", bcs->fcs);
+		bcs->hw.bas->fcserrs++;
+		gigaset_rcv_error(procskb, bcs->cs, bcs);
+	} else {
+		procskb->len -= 2;		/* subtract FCS */
+		procskb->tail -= 2;
+		dbg(DEBUG_ISO,
+		    "%s: good frame (%d octets)", __func__, procskb->len);
+		dump_bytes(DEBUG_STREAM,
+		           "rcv data", procskb->data, procskb->len);
+		bcs->hw.bas->goodbytes += procskb->len;
+		gigaset_rcv_skb(procskb, bcs->cs, bcs);
+	}
+
+	if ((bcs->skb = dev_alloc_skb(SBUFSIZE + HW_HDR_LEN)) != NULL)
+		skb_reserve(bcs->skb, HW_HDR_LEN);
+	else
+		err("could not allocate skb");
+	bcs->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;
+	}
+
+	notice("received partial byte (%d bits)", inbits);
+	bcs->hw.bas->alignerrs++;
+	gigaset_rcv_error(bcs->skb, bcs->cs, bcs);
+
+	if ((bcs->skb = dev_alloc_skb(SBUFSIZE + HW_HDR_LEN)) != NULL)
+		skb_reserve(bcs->skb, HW_HDR_LEN);
+	else
+		err("could not allocate skb");
+	bcs->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 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_rcv_skb
+ * notify of errors via gigaset_rcv_error
+ * 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;
+	int inputstate;
+	unsigned seqlen, inbyte, inbits;
+
+	IFNULLRET(bcs);
+	ubc = bcs->hw.bas;
+	IFNULLRET(ubc);
+
+	/* 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 */
+					inbits--;
+					/* correct the incorrectly handled cases individually */
+					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 */
+					inbits--;
+					/* correct the incorrectly handled cases individually */
+					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 */
+					switch (c) {	/* unstuff individually */
+					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_rcv_skb
+ * 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--;
+		hdlc_flush(bcs);
+		return;
+	}
+	if (unlikely((skb = bcs->skb) == NULL)) {
+		bcs->skb = skb = dev_alloc_skb(SBUFSIZE + HW_HDR_LEN);
+		if (!skb) {
+			err("could not allocate skb");
+			return;
+		}
+		skb_reserve(skb, HW_HDR_LEN);
+	}
+	bcs->hw.bas->goodbytes += skb->len;
+	dobytes = TRANSBUFSIZE - skb->len;
+	while (count > 0) {
+		dst = skb_put(skb, count < dobytes ? count : dobytes);
+		while (count > 0 && dobytes > 0) {
+			*dst++ = gigaset_invtab[*src++];
+			count--;
+			dobytes--;
+		}
+		if (dobytes == 0) {
+			gigaset_rcv_skb(skb, bcs->cs, bcs);
+			bcs->skb = skb = dev_alloc_skb(SBUFSIZE + HW_HDR_LEN);
+			if (!skb) {
+				err("could not allocate skb");
+				return;
+			}
+			skb_reserve(bcs->skb, HW_HDR_LEN);
+			dobytes = TRANSBUFSIZE;
+		}
+	}
+}
+
+void gigaset_isoc_receive(unsigned char *src, unsigned count, struct bc_state *bcs)
+{
+	switch (bcs->proto2) {
+	case ISDN_PROTO_L2_HDLC:
+		hdlc_unpack(src, count, bcs);
+		break;
+	default:		/* assume transparent */
+		trans_receive(src, count, bcs);
+	}
+}
+
+/* == data input =========================================================== */
+
+static void cmd_loop(unsigned char *src, int numbytes, struct inbuf_t *inbuf)
+{
+	struct cardstate *cs = inbuf->cs;
+	unsigned cbytes      = cs->cbytes;
+
+	while (numbytes--) {
+		/* copy next character, check for end of line */
+		switch (cs->respdata[cbytes] = *src++) {
+		case '\r':
+		case '\n':
+			/* end of line */
+			dbg(DEBUG_TRANSCMD, "%s: End of Command (%d Bytes)",
+			    __func__, cbytes);
+			cs->cbytes = cbytes;
+			gigaset_handle_modem_response(cs);
+			cbytes = 0;
+			break;
+		default:
+			/* advance in line buffer, checking for overflow */
+			if (cbytes < MAX_RESP_SIZE - 1)
+				cbytes++;
+			else
+				warn("response too large");
+		}
+	}
+
+	/* 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 = atomic_read(&inbuf->head);
+	while (head != (tail = atomic_read(&inbuf->tail))) {
+		dbg(DEBUG_INTR, "buffer state: %u -> %u", head, tail);
+		if (head > tail)
+			tail = RBUFSIZE;
+		src = inbuf->data + head;
+		numbytes = tail - head;
+		dbg(DEBUG_INTR, "processing %u bytes", numbytes);
+
+		if (atomic_read(&cs->mstate) == MS_LOCKED) {
+			gigaset_dbg_buffer(DEBUG_LOCKCMD, "received response",
+			                   numbytes, src, 0);
+			gigaset_if_receive(inbuf->cs, src, numbytes);
+		} else {
+			gigaset_dbg_buffer(DEBUG_CMD, "received response",
+			                   numbytes, src, 0);
+			cmd_loop(src, numbytes, inbuf);
+		}
+
+		head += numbytes;
+		if (head == RBUFSIZE)
+			head = 0;
+		dbg(DEBUG_INTR, "setting head to %u", head);
+		atomic_set(&inbuf->head, head);
+	}
+}
+
+
+/* == data output ========================================================== */
+
+/* gigaset_send_skb
+ * called by common.c to queue an skb for sending
+ * and start transmission if necessary
+ * parameters:
+ *	B Channel control structure
+ *	skb
+ * return value:
+ *	number of bytes accepted for sending
+ *	(skb->len if ok, 0 if out of buffer space)
+ *	or error code (< 0, eg. -EINVAL)
+ */
+int gigaset_isoc_send_skb(struct bc_state *bcs, struct sk_buff *skb)
+{
+	int len;
+
+	IFNULLRETVAL(bcs, -EFAULT);
+	IFNULLRETVAL(skb, -EFAULT);
+	len = skb->len;
+
+	skb_queue_tail(&bcs->squeue, skb);
+	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);
+
+	return len;	/* ok so far */
+}