slcan.c revision 7ad711b49e661a0979ed1a84bed16bc9fa7f872b 
1/*
2 * slcan.c - serial line CAN interface driver (using tty line discipline)
3 *
4 * This file is derived from linux/drivers/net/slip.c
5 *
6 * slip.c Authors  : Laurence Culhane <loz@holmes.demon.co.uk>
7 *                   Fred N. van Kempen <waltje@uwalt.nl.mugnet.org>
8 * slcan.c Author  : Oliver Hartkopp <socketcan@hartkopp.net>
9 *
10 * This program is free software; you can redistribute it and/or modify it
11 * under the terms of the GNU General Public License as published by the
12 * Free Software Foundation; either version 2 of the License, or (at your
13 * option) any later version.
14 *
15 * This program is distributed in the hope that it will be useful, but
16 * WITHOUT ANY WARRANTY; without even the implied warranty of
17 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
18 * General Public License for more details.
19 *
20 * You should have received a copy of the GNU General Public License along
21 * with this program; if not, write to the Free Software Foundation, Inc.,
22 * 59 Temple Place, Suite 330, Boston, MA 02111-1307. You can also get it
23 * at http://www.gnu.org/licenses/gpl.html
24 *
25 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
26 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
27 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
28 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
29 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
30 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
31 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
32 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
33 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
34 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
35 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
36 * DAMAGE.
37 *
38 * Send feedback to <socketcan-users@lists.berlios.de>
39 *
40 */
41
42#include <linux/module.h>
43#include <linux/moduleparam.h>
44
45#include <asm/system.h>
46#include <linux/uaccess.h>
47#include <linux/bitops.h>
48#include <linux/string.h>
49#include <linux/tty.h>
50#include <linux/errno.h>
51#include <linux/netdevice.h>
52#include <linux/skbuff.h>
53#include <linux/rtnetlink.h>
54#include <linux/if_arp.h>
55#include <linux/if_ether.h>
56#include <linux/sched.h>
57#include <linux/delay.h>
58#include <linux/init.h>
59#include <linux/kernel.h>
60#include <linux/can.h>
61
62static __initdata const char banner[] =
63	KERN_INFO "slcan: serial line CAN interface driver\n";
64
65MODULE_ALIAS_LDISC(N_SLCAN);
66MODULE_DESCRIPTION("serial line CAN interface");
67MODULE_LICENSE("GPL");
68MODULE_AUTHOR("Oliver Hartkopp <socketcan@hartkopp.net>");
69
70#define SLCAN_MAGIC 0x53CA
71
72static int maxdev = 10;		/* MAX number of SLCAN channels;
73				   This can be overridden with
74				   insmod slcan.ko maxdev=nnn	*/
75module_param(maxdev, int, 0);
76MODULE_PARM_DESC(maxdev, "Maximum number of slcan interfaces");
77
78/* maximum rx buffer len: extended CAN frame with timestamp */
79#define SLC_MTU (sizeof("T1111222281122334455667788EA5F\r")+1)
80
81struct slcan {
82	int			magic;
83
84	/* Various fields. */
85	struct tty_struct	*tty;		/* ptr to TTY structure	     */
86	struct net_device	*dev;		/* easy for intr handling    */
87	spinlock_t		lock;
88
89	/* These are pointers to the malloc()ed frame buffers. */
90	unsigned char		rbuff[SLC_MTU];	/* receiver buffer	     */
91	int			rcount;         /* received chars counter    */
92	unsigned char		xbuff[SLC_MTU];	/* transmitter buffer	     */
93	unsigned char		*xhead;         /* pointer to next XMIT byte */
94	int			xleft;          /* bytes left in XMIT queue  */
95
96	unsigned long		flags;		/* Flag values/ mode etc     */
97#define SLF_INUSE		0		/* Channel in use            */
98#define SLF_ERROR		1               /* Parity, etc. error        */
99};
100
101static struct net_device **slcan_devs;
102
103 /************************************************************************
104  *			SLCAN ENCAPSULATION FORMAT			 *
105  ************************************************************************/
106
107/*
108 * A CAN frame has a can_id (11 bit standard frame format OR 29 bit extended
109 * frame format) a data length code (can_dlc) which can be from 0 to 8
110 * and up to <can_dlc> data bytes as payload.
111 * Additionally a CAN frame may become a remote transmission frame if the
112 * RTR-bit is set. This causes another ECU to send a CAN frame with the
113 * given can_id.
114 *
115 * The SLCAN ASCII representation of these different frame types is:
116 * <type> <id> <dlc> <data>*
117 *
118 * Extended frames (29 bit) are defined by capital characters in the type.
119 * RTR frames are defined as 'r' types - normal frames have 't' type:
120 * t => 11 bit data frame
121 * r => 11 bit RTR frame
122 * T => 29 bit data frame
123 * R => 29 bit RTR frame
124 *
125 * The <id> is 3 (standard) or 8 (extended) bytes in ASCII Hex (base64).
126 * The <dlc> is a one byte ASCII number ('0' - '8')
127 * The <data> section has at much ASCII Hex bytes as defined by the <dlc>
128 *
129 * Examples:
130 *
131 * t1230 : can_id 0x123, can_dlc 0, no data
132 * t4563112233 : can_id 0x456, can_dlc 3, data 0x11 0x22 0x33
133 * T12ABCDEF2AA55 : extended can_id 0x12ABCDEF, can_dlc 2, data 0xAA 0x55
134 * r1230 : can_id 0x123, can_dlc 0, no data, remote transmission request
135 *
136 */
137
138 /************************************************************************
139  *			STANDARD SLCAN DECAPSULATION			 *
140  ************************************************************************/
141
142/* Send one completely decapsulated can_frame to the network layer */
143static void slc_bump(struct slcan *sl)
144{
145	struct sk_buff *skb;
146	struct can_frame cf;
147	int i, dlc_pos, tmp;
148	unsigned long ultmp;
149	char cmd = sl->rbuff[0];
150
151	if ((cmd != 't') && (cmd != 'T') && (cmd != 'r') && (cmd != 'R'))
152		return;
153
154	if (cmd & 0x20) /* tiny chars 'r' 't' => standard frame format */
155		dlc_pos = 4; /* dlc position tiiid */
156	else
157		dlc_pos = 9; /* dlc position Tiiiiiiiid */
158
159	if (!((sl->rbuff[dlc_pos] >= '0') && (sl->rbuff[dlc_pos] < '9')))
160		return;
161
162	cf.can_dlc = sl->rbuff[dlc_pos] - '0'; /* get can_dlc from ASCII val */
163
164	sl->rbuff[dlc_pos] = 0; /* terminate can_id string */
165
166	if (strict_strtoul(sl->rbuff+1, 16, &ultmp))
167		return;
168
169	cf.can_id = ultmp;
170
171	if (!(cmd & 0x20)) /* NO tiny chars => extended frame format */
172		cf.can_id |= CAN_EFF_FLAG;
173
174	if ((cmd | 0x20) == 'r') /* RTR frame */
175		cf.can_id |= CAN_RTR_FLAG;
176
177	*(u64 *) (&cf.data) = 0; /* clear payload */
178
179	for (i = 0, dlc_pos++; i < cf.can_dlc; i++) {
180		tmp = hex_to_bin(sl->rbuff[dlc_pos++]);
181		if (tmp < 0)
182			return;
183		cf.data[i] = (tmp << 4);
184		tmp = hex_to_bin(sl->rbuff[dlc_pos++]);
185		if (tmp < 0)
186			return;
187		cf.data[i] |= tmp;
188	}
189
190	skb = dev_alloc_skb(sizeof(struct can_frame));
191	if (!skb)
192		return;
193
194	skb->dev = sl->dev;
195	skb->protocol = htons(ETH_P_CAN);
196	skb->pkt_type = PACKET_BROADCAST;
197	skb->ip_summed = CHECKSUM_UNNECESSARY;
198	memcpy(skb_put(skb, sizeof(struct can_frame)),
199	       &cf, sizeof(struct can_frame));
200	netif_rx(skb);
201
202	sl->dev->stats.rx_packets++;
203	sl->dev->stats.rx_bytes += cf.can_dlc;
204}
205
206/* parse tty input stream */
207static void slcan_unesc(struct slcan *sl, unsigned char s)
208{
209
210	if ((s == '\r') || (s == '\a')) { /* CR or BEL ends the pdu */
211		if (!test_and_clear_bit(SLF_ERROR, &sl->flags) &&
212		    (sl->rcount > 4))  {
213			slc_bump(sl);
214		}
215		sl->rcount = 0;
216	} else {
217		if (!test_bit(SLF_ERROR, &sl->flags))  {
218			if (sl->rcount < SLC_MTU)  {
219				sl->rbuff[sl->rcount++] = s;
220				return;
221			} else {
222				sl->dev->stats.rx_over_errors++;
223				set_bit(SLF_ERROR, &sl->flags);
224			}
225		}
226	}
227}
228
229 /************************************************************************
230  *			STANDARD SLCAN ENCAPSULATION			 *
231  ************************************************************************/
232
233/* Encapsulate one can_frame and stuff into a TTY queue. */
234static void slc_encaps(struct slcan *sl, struct can_frame *cf)
235{
236	int actual, idx, i;
237	char cmd;
238
239	if (cf->can_id & CAN_RTR_FLAG)
240		cmd = 'R'; /* becomes 'r' in standard frame format */
241	else
242		cmd = 'T'; /* becomes 't' in standard frame format */
243
244	if (cf->can_id & CAN_EFF_FLAG)
245		sprintf(sl->xbuff, "%c%08X%d", cmd,
246			cf->can_id & CAN_EFF_MASK, cf->can_dlc);
247	else
248		sprintf(sl->xbuff, "%c%03X%d", cmd | 0x20,
249			cf->can_id & CAN_SFF_MASK, cf->can_dlc);
250
251	idx = strlen(sl->xbuff);
252
253	for (i = 0; i < cf->can_dlc; i++)
254		sprintf(&sl->xbuff[idx + 2*i], "%02X", cf->data[i]);
255
256	strcat(sl->xbuff, "\r"); /* add terminating character */
257
258	/* Order of next two lines is *very* important.
259	 * When we are sending a little amount of data,
260	 * the transfer may be completed inside the ops->write()
261	 * routine, because it's running with interrupts enabled.
262	 * In this case we *never* got WRITE_WAKEUP event,
263	 * if we did not request it before write operation.
264	 *       14 Oct 1994  Dmitry Gorodchanin.
265	 */
266	set_bit(TTY_DO_WRITE_WAKEUP, &sl->tty->flags);
267	actual = sl->tty->ops->write(sl->tty, sl->xbuff, strlen(sl->xbuff));
268	sl->xleft = strlen(sl->xbuff) - actual;
269	sl->xhead = sl->xbuff + actual;
270	sl->dev->stats.tx_bytes += cf->can_dlc;
271}
272
273/*
274 * Called by the driver when there's room for more data.  If we have
275 * more packets to send, we send them here.
276 */
277static void slcan_write_wakeup(struct tty_struct *tty)
278{
279	int actual;
280	struct slcan *sl = (struct slcan *) tty->disc_data;
281
282	/* First make sure we're connected. */
283	if (!sl || sl->magic != SLCAN_MAGIC || !netif_running(sl->dev))
284		return;
285
286	if (sl->xleft <= 0)  {
287		/* Now serial buffer is almost free & we can start
288		 * transmission of another packet */
289		sl->dev->stats.tx_packets++;
290		clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
291		netif_wake_queue(sl->dev);
292		return;
293	}
294
295	actual = tty->ops->write(tty, sl->xhead, sl->xleft);
296	sl->xleft -= actual;
297	sl->xhead += actual;
298}
299
300/* Send a can_frame to a TTY queue. */
301static netdev_tx_t slc_xmit(struct sk_buff *skb, struct net_device *dev)
302{
303	struct slcan *sl = netdev_priv(dev);
304
305	if (skb->len != sizeof(struct can_frame))
306		goto out;
307
308	spin_lock(&sl->lock);
309	if (!netif_running(dev))  {
310		spin_unlock(&sl->lock);
311		printk(KERN_WARNING "%s: xmit: iface is down\n", dev->name);
312		goto out;
313	}
314	if (sl->tty == NULL) {
315		spin_unlock(&sl->lock);
316		goto out;
317	}
318
319	netif_stop_queue(sl->dev);
320	slc_encaps(sl, (struct can_frame *) skb->data); /* encaps & send */
321	spin_unlock(&sl->lock);
322
323out:
324	kfree_skb(skb);
325	return NETDEV_TX_OK;
326}
327
328
329/******************************************
330 *   Routines looking at netdevice side.
331 ******************************************/
332
333/* Netdevice UP -> DOWN routine */
334static int slc_close(struct net_device *dev)
335{
336	struct slcan *sl = netdev_priv(dev);
337
338	spin_lock_bh(&sl->lock);
339	if (sl->tty) {
340		/* TTY discipline is running. */
341		clear_bit(TTY_DO_WRITE_WAKEUP, &sl->tty->flags);
342	}
343	netif_stop_queue(dev);
344	sl->rcount   = 0;
345	sl->xleft    = 0;
346	spin_unlock_bh(&sl->lock);
347
348	return 0;
349}
350
351/* Netdevice DOWN -> UP routine */
352static int slc_open(struct net_device *dev)
353{
354	struct slcan *sl = netdev_priv(dev);
355
356	if (sl->tty == NULL)
357		return -ENODEV;
358
359	sl->flags &= (1 << SLF_INUSE);
360	netif_start_queue(dev);
361	return 0;
362}
363
364/* Hook the destructor so we can free slcan devs at the right point in time */
365static void slc_free_netdev(struct net_device *dev)
366{
367	int i = dev->base_addr;
368	free_netdev(dev);
369	slcan_devs[i] = NULL;
370}
371
372static const struct net_device_ops slc_netdev_ops = {
373	.ndo_open               = slc_open,
374	.ndo_stop               = slc_close,
375	.ndo_start_xmit         = slc_xmit,
376};
377
378static void slc_setup(struct net_device *dev)
379{
380	dev->netdev_ops		= &slc_netdev_ops;
381	dev->destructor		= slc_free_netdev;
382
383	dev->hard_header_len	= 0;
384	dev->addr_len		= 0;
385	dev->tx_queue_len	= 10;
386
387	dev->mtu		= sizeof(struct can_frame);
388	dev->type		= ARPHRD_CAN;
389
390	/* New-style flags. */
391	dev->flags		= IFF_NOARP;
392	dev->features           = NETIF_F_NO_CSUM;
393}
394
395/******************************************
396  Routines looking at TTY side.
397 ******************************************/
398
399/*
400 * Handle the 'receiver data ready' interrupt.
401 * This function is called by the 'tty_io' module in the kernel when
402 * a block of SLCAN data has been received, which can now be decapsulated
403 * and sent on to some IP layer for further processing. This will not
404 * be re-entered while running but other ldisc functions may be called
405 * in parallel
406 */
407
408static void slcan_receive_buf(struct tty_struct *tty,
409			      const unsigned char *cp, char *fp, int count)
410{
411	struct slcan *sl = (struct slcan *) tty->disc_data;
412
413	if (!sl || sl->magic != SLCAN_MAGIC || !netif_running(sl->dev))
414		return;
415
416	/* Read the characters out of the buffer */
417	while (count--) {
418		if (fp && *fp++) {
419			if (!test_and_set_bit(SLF_ERROR, &sl->flags))
420				sl->dev->stats.rx_errors++;
421			cp++;
422			continue;
423		}
424		slcan_unesc(sl, *cp++);
425	}
426}
427
428/************************************
429 *  slcan_open helper routines.
430 ************************************/
431
432/* Collect hanged up channels */
433static void slc_sync(void)
434{
435	int i;
436	struct net_device *dev;
437	struct slcan	  *sl;
438
439	for (i = 0; i < maxdev; i++) {
440		dev = slcan_devs[i];
441		if (dev == NULL)
442			break;
443
444		sl = netdev_priv(dev);
445		if (sl->tty)
446			continue;
447		if (dev->flags & IFF_UP)
448			dev_close(dev);
449	}
450}
451
452/* Find a free SLCAN channel, and link in this `tty' line. */
453static struct slcan *slc_alloc(dev_t line)
454{
455	int i;
456	char name[IFNAMSIZ];
457	struct net_device *dev = NULL;
458	struct slcan       *sl;
459
460	for (i = 0; i < maxdev; i++) {
461		dev = slcan_devs[i];
462		if (dev == NULL)
463			break;
464
465	}
466
467	/* Sorry, too many, all slots in use */
468	if (i >= maxdev)
469		return NULL;
470
471	sprintf(name, "slcan%d", i);
472	dev = alloc_netdev(sizeof(*sl), name, slc_setup);
473	if (!dev)
474		return NULL;
475
476	dev->base_addr  = i;
477	sl = netdev_priv(dev);
478
479	/* Initialize channel control data */
480	sl->magic = SLCAN_MAGIC;
481	sl->dev	= dev;
482	spin_lock_init(&sl->lock);
483	slcan_devs[i] = dev;
484
485	return sl;
486}
487
488/*
489 * Open the high-level part of the SLCAN channel.
490 * This function is called by the TTY module when the
491 * SLCAN line discipline is called for.  Because we are
492 * sure the tty line exists, we only have to link it to
493 * a free SLCAN channel...
494 *
495 * Called in process context serialized from other ldisc calls.
496 */
497
498static int slcan_open(struct tty_struct *tty)
499{
500	struct slcan *sl;
501	int err;
502
503	if (!capable(CAP_NET_ADMIN))
504		return -EPERM;
505
506	if (tty->ops->write == NULL)
507		return -EOPNOTSUPP;
508
509	/* RTnetlink lock is misused here to serialize concurrent
510	   opens of slcan channels. There are better ways, but it is
511	   the simplest one.
512	 */
513	rtnl_lock();
514
515	/* Collect hanged up channels. */
516	slc_sync();
517
518	sl = tty->disc_data;
519
520	err = -EEXIST;
521	/* First make sure we're not already connected. */
522	if (sl && sl->magic == SLCAN_MAGIC)
523		goto err_exit;
524
525	/* OK.  Find a free SLCAN channel to use. */
526	err = -ENFILE;
527	sl = slc_alloc(tty_devnum(tty));
528	if (sl == NULL)
529		goto err_exit;
530
531	sl->tty = tty;
532	tty->disc_data = sl;
533
534	if (!test_bit(SLF_INUSE, &sl->flags)) {
535		/* Perform the low-level SLCAN initialization. */
536		sl->rcount   = 0;
537		sl->xleft    = 0;
538
539		set_bit(SLF_INUSE, &sl->flags);
540
541		err = register_netdevice(sl->dev);
542		if (err)
543			goto err_free_chan;
544	}
545
546	/* Done.  We have linked the TTY line to a channel. */
547	rtnl_unlock();
548	tty->receive_room = 65536;	/* We don't flow control */
549
550	/* TTY layer expects 0 on success */
551	return 0;
552
553err_free_chan:
554	sl->tty = NULL;
555	tty->disc_data = NULL;
556	clear_bit(SLF_INUSE, &sl->flags);
557
558err_exit:
559	rtnl_unlock();
560
561	/* Count references from TTY module */
562	return err;
563}
564
565/*
566 * Close down a SLCAN channel.
567 * This means flushing out any pending queues, and then returning. This
568 * call is serialized against other ldisc functions.
569 *
570 * We also use this method for a hangup event.
571 */
572
573static void slcan_close(struct tty_struct *tty)
574{
575	struct slcan *sl = (struct slcan *) tty->disc_data;
576
577	/* First make sure we're connected. */
578	if (!sl || sl->magic != SLCAN_MAGIC || sl->tty != tty)
579		return;
580
581	tty->disc_data = NULL;
582	sl->tty = NULL;
583
584	/* Flush network side */
585	unregister_netdev(sl->dev);
586	/* This will complete via sl_free_netdev */
587}
588
589static int slcan_hangup(struct tty_struct *tty)
590{
591	slcan_close(tty);
592	return 0;
593}
594
595/* Perform I/O control on an active SLCAN channel. */
596static int slcan_ioctl(struct tty_struct *tty, struct file *file,
597		       unsigned int cmd, unsigned long arg)
598{
599	struct slcan *sl = (struct slcan *) tty->disc_data;
600	unsigned int tmp;
601
602	/* First make sure we're connected. */
603	if (!sl || sl->magic != SLCAN_MAGIC)
604		return -EINVAL;
605
606	switch (cmd) {
607	case SIOCGIFNAME:
608		tmp = strlen(sl->dev->name) + 1;
609		if (copy_to_user((void __user *)arg, sl->dev->name, tmp))
610			return -EFAULT;
611		return 0;
612
613	case SIOCSIFHWADDR:
614		return -EINVAL;
615
616	default:
617		return tty_mode_ioctl(tty, file, cmd, arg);
618	}
619}
620
621static struct tty_ldisc_ops slc_ldisc = {
622	.owner		= THIS_MODULE,
623	.magic		= TTY_LDISC_MAGIC,
624	.name		= "slcan",
625	.open		= slcan_open,
626	.close		= slcan_close,
627	.hangup		= slcan_hangup,
628	.ioctl		= slcan_ioctl,
629	.receive_buf	= slcan_receive_buf,
630	.write_wakeup	= slcan_write_wakeup,
631};
632
633static int __init slcan_init(void)
634{
635	int status;
636
637	if (maxdev < 4)
638		maxdev = 4; /* Sanity */
639
640	printk(banner);
641	printk(KERN_INFO "slcan: %d dynamic interface channels.\n", maxdev);
642
643	slcan_devs = kzalloc(sizeof(struct net_device *)*maxdev, GFP_KERNEL);
644	if (!slcan_devs) {
645		printk(KERN_ERR "slcan: can't allocate slcan device array!\n");
646		return -ENOMEM;
647	}
648
649	/* Fill in our line protocol discipline, and register it */
650	status = tty_register_ldisc(N_SLCAN, &slc_ldisc);
651	if (status)  {
652		printk(KERN_ERR "slcan: can't register line discipline\n");
653		kfree(slcan_devs);
654	}
655	return status;
656}
657
658static void __exit slcan_exit(void)
659{
660	int i;
661	struct net_device *dev;
662	struct slcan *sl;
663	unsigned long timeout = jiffies + HZ;
664	int busy = 0;
665
666	if (slcan_devs == NULL)
667		return;
668
669	/* First of all: check for active disciplines and hangup them.
670	 */
671	do {
672		if (busy)
673			msleep_interruptible(100);
674
675		busy = 0;
676		for (i = 0; i < maxdev; i++) {
677			dev = slcan_devs[i];
678			if (!dev)
679				continue;
680			sl = netdev_priv(dev);
681			spin_lock_bh(&sl->lock);
682			if (sl->tty) {
683				busy++;
684				tty_hangup(sl->tty);
685			}
686			spin_unlock_bh(&sl->lock);
687		}
688	} while (busy && time_before(jiffies, timeout));
689
690	/* FIXME: hangup is async so we should wait when doing this second
691	   phase */
692
693	for (i = 0; i < maxdev; i++) {
694		dev = slcan_devs[i];
695		if (!dev)
696			continue;
697		slcan_devs[i] = NULL;
698
699		sl = netdev_priv(dev);
700		if (sl->tty) {
701			printk(KERN_ERR "%s: tty discipline still running\n",
702			       dev->name);
703			/* Intentionally leak the control block. */
704			dev->destructor = NULL;
705		}
706
707		unregister_netdev(dev);
708	}
709
710	kfree(slcan_devs);
711	slcan_devs = NULL;
712
713	i = tty_unregister_ldisc(N_SLCAN);
714	if (i)
715		printk(KERN_ERR "slcan: can't unregister ldisc (err %d)\n", i);
716}
717
718module_init(slcan_init);
719module_exit(slcan_exit);
720