drivers/net/hamradio/hdlcdrv.c



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/*****************************************************************************/

/*
 *	hdlcdrv.c  -- HDLC packet radio network driver.
 *
 *	Copyright (C) 1996-2000  Thomas Sailer (sailer@ife.ee.ethz.ch)
 *
 *	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.
 *
 *	This program is distributed in the hope that it will be useful,
 *	but WITHOUT ANY WARRANTY; without even the implied warranty of
 *	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *	GNU General Public License for more details.
 *
 *	You should have received a copy of the GNU General Public License
 *	along with this program; if not, write to the Free Software
 *	Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 *
 *  Please note that the GPL allows you to use the driver, NOT the radio.
 *  In order to use the radio, you need a license from the communications
 *  authority of your country.
 *
 *  The driver was derived from Donald Beckers skeleton.c
 *	Written 1993-94 by Donald Becker.
 *
 *  History:
 *   0.1  21.09.1996  Started
 *        18.10.1996  Changed to new user space access routines 
 *                    (copy_{to,from}_user)
 *   0.2  21.11.1996  various small changes
 *   0.3  03.03.1997  fixed (hopefully) IP not working with ax.25 as a module
 *   0.4  16.04.1997  init code/data tagged
 *   0.5  30.07.1997  made HDLC buffers bigger (solves a problem with the
 *                    soundmodem driver)
 *   0.6  05.04.1998  add spinlocks
 *   0.7  03.08.1999  removed some old compatibility cruft
 *   0.8  12.02.2000  adapted to softnet driver interface
 */

/*****************************************************************************/

#include <linux/module.h>
#include <linux/types.h>
#include <linux/net.h>
#include <linux/in.h>
#include <linux/if.h>
#include <linux/slab.h>
#include <linux/errno.h>
#include <linux/init.h>
#include <linux/bitops.h>

#include <linux/netdevice.h>
#include <linux/if_arp.h>
#include <linux/skbuff.h>
#include <linux/hdlcdrv.h>
#include <linux/random.h>
#include <net/ax25.h> 
#include <asm/uaccess.h>

#include <linux/crc-ccitt.h>

/* --------------------------------------------------------------------- */

#define KISS_VERBOSE

/* --------------------------------------------------------------------- */

#define PARAM_TXDELAY   1
#define PARAM_PERSIST   2
#define PARAM_SLOTTIME  3
#define PARAM_TXTAIL    4
#define PARAM_FULLDUP   5
#define PARAM_HARDWARE  6
#define PARAM_RETURN    255

/* --------------------------------------------------------------------- */
/*
 * the CRC routines are stolen from WAMPES
 * by Dieter Deyke
 */


/*---------------------------------------------------------------------------*/

static inline void append_crc_ccitt(unsigned char *buffer, int len)
{
 	unsigned int crc = crc_ccitt(0xffff, buffer, len) ^ 0xffff;
	*buffer++ = crc;
	*buffer++ = crc >> 8;
}

/*---------------------------------------------------------------------------*/

static inline int check_crc_ccitt(const unsigned char *buf, int cnt)
{
	return (crc_ccitt(0xffff, buf, cnt) & 0xffff) == 0xf0b8;
}

/*---------------------------------------------------------------------------*/

#if 0
static int calc_crc_ccitt(const unsigned char *buf, int cnt)
{
	unsigned int crc = 0xffff;

	for (; cnt > 0; cnt--)
		crc = (crc >> 8) ^ crc_ccitt_table[(crc ^ *buf++) & 0xff];
	crc ^= 0xffff;
	return (crc & 0xffff);
}
#endif

/* ---------------------------------------------------------------------- */

#define tenms_to_2flags(s,tenms) ((tenms * s->par.bitrate) / 100 / 16)

/* ---------------------------------------------------------------------- */
/*
 * The HDLC routines
 */

static int hdlc_rx_add_bytes(struct hdlcdrv_state *s, unsigned int bits, 
			     int num)
{
	int added = 0;
	
	while (s->hdlcrx.rx_state && num >= 8) {
		if (s->hdlcrx.len >= sizeof(s->hdlcrx.buffer)) {
			s->hdlcrx.rx_state = 0;
			return 0;
		}
		*s->hdlcrx.bp++ = bits >> (32-num);
		s->hdlcrx.len++;
		num -= 8;
		added += 8;
	}
	return added;
}

static void hdlc_rx_flag(struct net_device *dev, struct hdlcdrv_state *s)
{
	struct sk_buff *skb;
	int pkt_len;
	unsigned char *cp;

	if (s->hdlcrx.len < 4) 
		return;
	if (!check_crc_ccitt(s->hdlcrx.buffer, s->hdlcrx.len)) 
		return;
	pkt_len = s->hdlcrx.len - 2 + 1; /* KISS kludge */
	if (!(skb = dev_alloc_skb(pkt_len))) {
		printk("%s: memory squeeze, dropping packet\n", dev->name);
		s->stats.rx_dropped++;
		return;
	}
	cp = skb_put(skb, pkt_len);
	*cp++ = 0; /* KISS kludge */
	memcpy(cp, s->hdlcrx.buffer, pkt_len - 1);
	skb->protocol = ax25_type_trans(skb, dev);
	netif_rx(skb);
	dev->last_rx = jiffies;
	s->stats.rx_packets++;
}

void hdlcdrv_receiver(struct net_device *dev, struct hdlcdrv_state *s)
{
	int i;
	unsigned int mask1, mask2, mask3, mask4, mask5, mask6, word;
	
	if (!s || s->magic != HDLCDRV_MAGIC) 
		return;
	if (test_and_set_bit(0, &s->hdlcrx.in_hdlc_rx))
		return;

	while (!hdlcdrv_hbuf_empty(&s->hdlcrx.hbuf)) {
		word = hdlcdrv_hbuf_get(&s->hdlcrx.hbuf);	

#ifdef HDLCDRV_DEBUG
		hdlcdrv_add_bitbuffer_word(&s->bitbuf_hdlc, word);
#endif /* HDLCDRV_DEBUG */
	       	s->hdlcrx.bitstream >>= 16;
		s->hdlcrx.bitstream |= word << 16;
		s->hdlcrx.bitbuf >>= 16;
		s->hdlcrx.bitbuf |= word << 16;
		s->hdlcrx.numbits += 16;
		for(i = 15, mask1 = 0x1fc00, mask2 = 0x1fe00, mask3 = 0x0fc00,
		    mask4 = 0x1f800, mask5 = 0xf800, mask6 = 0xffff; 
		    i >= 0; 
		    i--, mask1 <<= 1, mask2 <<= 1, mask3 <<= 1, mask4 <<= 1, 
		    mask5 <<= 1, mask6 = (mask6 << 1) | 1) {
			if ((s->hdlcrx.bitstream & mask1) == mask1)
				s->hdlcrx.rx_state = 0; /* abort received */
			else if ((s->hdlcrx.bitstream & mask2) == mask3) {
				/* flag received */
				if (s->hdlcrx.rx_state) {
					hdlc_rx_add_bytes(s, s->hdlcrx.bitbuf 
							  << (8+i),
							  s->hdlcrx.numbits
							  -8-i);
					hdlc_rx_flag(dev, s);
				}
				s->hdlcrx.len = 0;
				s->hdlcrx.bp = s->hdlcrx.buffer;
				s->hdlcrx.rx_state = 1;
				s->hdlcrx.numbits = i;
			} else if ((s->hdlcrx.bitstream & mask4) == mask5) {
				/* stuffed bit */
				s->hdlcrx.numbits--;
				s->hdlcrx.bitbuf = (s->hdlcrx.bitbuf & (~mask6)) |
					((s->hdlcrx.bitbuf & mask6) << 1);
			}
		}
		s->hdlcrx.numbits -= hdlc_rx_add_bytes(s, s->hdlcrx.bitbuf,
						       s->hdlcrx.numbits);
	}
	clear_bit(0, &s->hdlcrx.in_hdlc_rx);
}

/* ---------------------------------------------------------------------- */

static inline void do_kiss_params(struct hdlcdrv_state *s,
				  unsigned char *data, unsigned long len)
{

#ifdef KISS_VERBOSE
#define PKP(a,b) printk(KERN_INFO "hdlcdrv.c: channel params: " a "\n", b)
#else /* KISS_VERBOSE */	      
#define PKP(a,b) 
#endif /* KISS_VERBOSE */	      

	if (len < 2)
		return;
	switch(data[0]) {
	case PARAM_TXDELAY:
		s->ch_params.tx_delay = data[1];
		PKP("TX delay = %ums", 10 * s->ch_params.tx_delay);
		break;
	case PARAM_PERSIST:   
		s->ch_params.ppersist = data[1];
		PKP("p persistence = %u", s->ch_params.ppersist);
		break;
	case PARAM_SLOTTIME:  
		s->ch_params.slottime = data[1];
		PKP("slot time = %ums", s->ch_params.slottime);
		break;
	case PARAM_TXTAIL:    
		s->ch_params.tx_tail = data[1];
		PKP("TX tail = %ums", s->ch_params.tx_tail);
		break;
	case PARAM_FULLDUP:   
		s->ch_params.fulldup = !!data[1];
		PKP("%s duplex", s->ch_params.fulldup ? "full" : "half");
		break;
	default:
		break;
	}
#undef PKP
}

/* ---------------------------------------------------------------------- */

void hdlcdrv_transmitter(struct net_device *dev, struct hdlcdrv_state *s)
{
	unsigned int mask1, mask2, mask3;
	int i;
	struct sk_buff *skb;
	int pkt_len;

	if (!s || s->magic != HDLCDRV_MAGIC) 
		return;
	if (test_and_set_bit(0, &s->hdlctx.in_hdlc_tx))
		return;
	for (;;) {
		if (s->hdlctx.numbits >= 16) {
			if (hdlcdrv_hbuf_full(&s->hdlctx.hbuf)) {
				clear_bit(0, &s->hdlctx.in_hdlc_tx);
				return;
			}
			hdlcdrv_hbuf_put(&s->hdlctx.hbuf, s->hdlctx.bitbuf);
			s->hdlctx.bitbuf >>= 16;
			s->hdlctx.numbits -= 16;
		}
		switch (s->hdlctx.tx_state) {
		default:
			clear_bit(0, &s->hdlctx.in_hdlc_tx);
			return;
		case 0:
		case 1:
			if (s->hdlctx.numflags) {
				s->hdlctx.numflags--;
				s->hdlctx.bitbuf |= 
					0x7e7e << s->hdlctx.numbits;
				s->hdlctx.numbits += 16;
				break;
			}
			if (s->hdlctx.tx_state == 1) {
				clear_bit(0, &s->hdlctx.in_hdlc_tx);
				return;
			}
			if (!(skb = s->skb)) {
				int flgs = tenms_to_2flags(s, s->ch_params.tx_tail);
				if (flgs < 2)
					flgs = 2;
				s->hdlctx.tx_state = 1;
				s->hdlctx.numflags = flgs;
				break;
			}
			s->skb = NULL;
			netif_wake_queue(dev);
			pkt_len = skb->len-1; /* strip KISS byte */
			if (pkt_len >= HDLCDRV_MAXFLEN || pkt_len < 2) {
				s->hdlctx.tx_state = 0;
				s->hdlctx.numflags = 1;
				dev_kfree_skb_irq(skb);
				break;
			}
			skb_copy_from_linear_data_offset(skb, 1,
							 s->hdlctx.buffer,
							 pkt_len);
			dev_kfree_skb_irq(skb);
			s->hdlctx.bp = s->hdlctx.buffer;
			append_crc_ccitt(s->hdlctx.buffer, pkt_len);
			s->hdlctx.len = pkt_len+2; /* the appended CRC */
			s->hdlctx.tx_state = 2;
			s->hdlctx.bitstream = 0;
			s->stats.tx_packets++;
			break;
		case 2:
			if (!s->hdlctx.len) {
				s->hdlctx.tx_state = 0;
				s->hdlctx.numflags = 1;
				break;
			}
			s->hdlctx.len--;
			s->hdlctx.bitbuf |= *s->hdlctx.bp <<
				s->hdlctx.numbits;
			s->hdlctx.bitstream >>= 8;
			s->hdlctx.bitstream |= (*s->hdlctx.bp++) << 16;
			mask1 = 0x1f000;
			mask2 = 0x10000;
			mask3 = 0xffffffff >> (31-s->hdlctx.numbits);
			s->hdlctx.numbits += 8;
			for(i = 0; i < 8; i++, mask1 <<= 1, mask2 <<= 1, 
			    mask3 = (mask3 << 1) | 1) {
				if ((s->hdlctx.bitstream & mask1) != mask1) 
					continue;
				s->hdlctx.bitstream &= ~mask2;
				s->hdlctx.bitbuf = 
					(s->hdlctx.bitbuf & mask3) |