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    Subject[PATCH 8/9] isdn4linux: Siemens Gigaset drivers - isochronous data handler
    From: Tilman Schmidt <tilman@imap.cc>, Hansjoerg Lipp <hjlipp@web.de>

    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>
    ---

    drivers/isdn/gigaset/isocdata.c | 1009 ++++++++++++++++++++++++++++++++++++++++
    1 files changed, 1009 insertions(+)

    --- linux-2.6.16-rc2/drivers/isdn/gigaset/isocdata.c 1970-01-01 01:00:00.000000000 +0100
    +++ linux-2.6.16-rc2-gig/drivers/isdn/gigaset/isocdata.c 2006-01-21 17:33:33.000000000 +0100
    @@ -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 */
    +}
    -
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