isocdata.c

来自「LINUX 2.6.17.4的源码」· C语言 代码 · 共 1,011 行 · 第 1/3 页

/*
 * Common data handling layer for bas_gigaset
 *
 * Copyright (c) 2005 by Tilman Schmidt <[e-mail]>,
 *                       Hansjoerg Lipp <[e-mail]>.
 *
 * =====================================================================
 *	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>

/* 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);
		gig_dbg(DEBUG_ISO, "%s: couldn't acquire iso write semaphore",
			__func__);
		return 0;
	}
#ifdef CONFIG_GIGASET_DEBUG
	gig_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];
	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 = atomic_read(&iwb->nextread);
	write = atomic_read(&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)) {
		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;
				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 */
				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;
	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++] = hexdigit[(c >> 4) & 0x0f];
		dbgline[i++] = hexdigit[c & 0x0f];
	}
	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 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,