slcan.c revision 3396c7823efb3a5b8630388c464e1034ea031ced 
1/*
2 * slcan.c - serial line CAN interface driver (using tty line discipline)
3 *
4 * This file is derived from linux/drivers/net/slip/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 */
39
40#include <linux/module.h>
41#include <linux/moduleparam.h>
42
43#include <asm/system.h>
44#include <linux/uaccess.h>
45#include <linux/bitops.h>
46#include <linux/string.h>
47#include <linux/tty.h>
48#include <linux/errno.h>
49#include <linux/netdevice.h>
50#include <linux/skbuff.h>
51#include <linux/rtnetlink.h>
52#include <linux/if_arp.h>
53#include <linux/if_ether.h>
54#include <linux/sched.h>
55#include <linux/delay.h>
56#include <linux/init.h>
57#include <linux/kernel.h>
58#include <linux/can.h>
59
60static __initdata const char banner[] =
61	KERN_INFO "slcan: serial line CAN interface driver\n";
62
63MODULE_ALIAS_LDISC(N_SLCAN);
64MODULE_DESCRIPTION("serial line CAN interface");
65MODULE_LICENSE("GPL");
66MODULE_AUTHOR("Oliver Hartkopp <socketcan@hartkopp.net>");
67
68#define SLCAN_MAGIC 0x53CA
69
70static int maxdev = 10;		/* MAX number of SLCAN channels;
71				   This can be overridden with
72				   insmod slcan.ko maxdev=nnn	*/
73module_param(maxdev, int, 0);
74MODULE_PARM_DESC(maxdev, "Maximum number of slcan interfaces");
75
76/* maximum rx buffer len: extended CAN frame with timestamp */
77#define SLC_MTU (sizeof("T1111222281122334455667788EA5F\r")+1)
78
79struct slcan {
80	int			magic;
81
82	/* Various fields. */
83	struct tty_struct	*tty;		/* ptr to TTY structure	     */
84	struct net_device	*dev;		/* easy for intr handling    */
85	spinlock_t		lock;
86
87	/* These are pointers to the malloc()ed frame buffers. */
88	unsigned char		rbuff[SLC_MTU];	/* receiver buffer	     */
89	int			rcount;         /* received chars counter    */
90	unsigned char		xbuff[SLC_MTU];	/* transmitter buffer	     */
91	unsigned char		*xhead;         /* pointer to next XMIT byte */
92	int			xleft;          /* bytes left in XMIT queue  */
93
94	unsigned long		flags;		/* Flag values/ mode etc     */
95#define SLF_INUSE		0		/* Channel in use            */
96#define SLF_ERROR		1               /* Parity, etc. error        */
97};
98
99static struct net_device **slcan_devs;
100
101 /************************************************************************
102  *			SLCAN ENCAPSULATION FORMAT			 *
103  ************************************************************************/
104
105/*
106 * A CAN frame has a can_id (11 bit standard frame format OR 29 bit extended
107 * frame format) a data length code (can_dlc) which can be from 0 to 8
108 * and up to <can_dlc> data bytes as payload.
109 * Additionally a CAN frame may become a remote transmission frame if the
110 * RTR-bit is set. This causes another ECU to send a CAN frame with the
111 * given can_id.
112 *
113 * The SLCAN ASCII representation of these different frame types is:
114 * <type> <id> <dlc> <data>*
115 *
116 * Extended frames (29 bit) are defined by capital characters in the type.
117 * RTR frames are defined as 'r' types - normal frames have 't' type:
118 * t => 11 bit data frame
119 * r => 11 bit RTR frame
120 * T => 29 bit data frame
121 * R => 29 bit RTR frame
122 *
123 * The <id> is 3 (standard) or 8 (extended) bytes in ASCII Hex (base64).
124 * The <dlc> is a one byte ASCII number ('0' - '8')
125 * The <data> section has at much ASCII Hex bytes as defined by the <dlc>
126 *
127 * Examples:
128 *
129 * t1230 : can_id 0x123, can_dlc 0, no data
130 * t4563112233 : can_id 0x456, can_dlc 3, data 0x11 0x22 0x33
131 * T12ABCDEF2AA55 : extended can_id 0x12ABCDEF, can_dlc 2, data 0xAA 0x55
132 * r1230 : can_id 0x123, can_dlc 0, no data, remote transmission request
133 *
134 */
135
136 /************************************************************************
137  *			STANDARD SLCAN DECAPSULATION			 *
138  ************************************************************************/
139
140/* Send one completely decapsulated can_frame to the network layer */
141static void slc_bump(struct slcan *sl)
142{
143	struct sk_buff *skb;
144	struct can_frame cf;
145	int i, dlc_pos, tmp;
146	unsigned long ultmp;
147	char cmd = sl->rbuff[0];
148
149	if ((cmd != 't') && (cmd != 'T') && (cmd != 'r') && (cmd != 'R'))
150		return;
151
152	if (cmd & 0x20) /* tiny chars 'r' 't' => standard frame format */
153		dlc_pos = 4; /* dlc position tiiid */
154	else
155		dlc_pos = 9; /* dlc position Tiiiiiiiid */
156
157	if (!((sl->rbuff[dlc_pos] >= '0') && (sl->rbuff[dlc_pos] < '9')))
158		return;
159
160	cf.can_dlc = sl->rbuff[dlc_pos] - '0'; /* get can_dlc from ASCII val */
161
162	sl->rbuff[dlc_pos] = 0; /* terminate can_id string */
163
164	if (strict_strtoul(sl->rbuff+1, 16, &ultmp))
165		return;
166
167	cf.can_id = ultmp;
168
169	if (!(cmd & 0x20)) /* NO tiny chars => extended frame format */
170		cf.can_id |= CAN_EFF_FLAG;
171
172	if ((cmd | 0x20) == 'r') /* RTR frame */
173		cf.can_id |= CAN_RTR_FLAG;
174
175	*(u64 *) (&cf.data) = 0; /* clear payload */
176
177	for (i = 0, dlc_pos++; i < cf.can_dlc; i++) {
178		tmp = hex_to_bin(sl->rbuff[dlc_pos++]);
179		if (tmp < 0)
180			return;
181		cf.data[i] = (tmp << 4);
182		tmp = hex_to_bin(sl->rbuff[dlc_pos++]);
183		if (tmp < 0)
184			return;
185		cf.data[i] |= tmp;
186	}
187
188	skb = dev_alloc_skb(sizeof(struct can_frame));
189	if (!skb)
190		return;
191
192	skb->dev = sl->dev;
193	skb->protocol = htons(ETH_P_CAN);
194	skb->pkt_type = PACKET_BROADCAST;
195	skb->ip_summed = CHECKSUM_UNNECESSARY;
196	memcpy(skb_put(skb, sizeof(struct can_frame)),
197	       &cf, sizeof(struct can_frame));
198	netif_rx_ni(skb);
199
200	sl->dev->stats.rx_packets++;
201	sl->dev->stats.rx_bytes += cf.can_dlc;
202}
203
204/* parse tty input stream */
205static void slcan_unesc(struct slcan *sl, unsigned char s)
206{
207
208	if ((s == '\r') || (s == '\a')) { /* CR or BEL ends the pdu */
209		if (!test_and_clear_bit(SLF_ERROR, &sl->flags) &&
210		    (sl->rcount > 4))  {
211			slc_bump(sl);
212		}
213		sl->rcount = 0;
214	} else {
215		if (!test_bit(SLF_ERROR, &sl->flags))  {
216			if (sl->rcount < SLC_MTU)  {
217				sl->rbuff[sl->rcount++] = s;
218				return;
219			} else {
220				sl->dev->stats.rx_over_errors++;
221				set_bit(SLF_ERROR, &sl->flags);
222			}
223		}
224	}
225}
226
227 /************************************************************************
228  *			STANDARD SLCAN ENCAPSULATION			 *
229  ************************************************************************/
230
231/* Encapsulate one can_frame and stuff into a TTY queue. */
232static void slc_encaps(struct slcan *sl, struct can_frame *cf)
233{
234	int actual, idx, i;
235	char cmd;
236
237	if (cf->can_id & CAN_RTR_FLAG)
238		cmd = 'R'; /* becomes 'r' in standard frame format */
239	else
240		cmd = 'T'; /* becomes 't' in standard frame format */
241
242	if (cf->can_id & CAN_EFF_FLAG)
243		sprintf(sl->xbuff, "%c%08X%d", cmd,
244			cf->can_id & CAN_EFF_MASK, cf->can_dlc);
245	else
246		sprintf(sl->xbuff, "%c%03X%d", cmd | 0x20,
247			cf->can_id & CAN_SFF_MASK, cf->can_dlc);
248
249	idx = strlen(sl->xbuff);
250
251	for (i = 0; i < cf->can_dlc; i++)
252		sprintf(&sl->xbuff[idx + 2*i], "%02X", cf->data[i]);
253
254	strcat(sl->xbuff, "\r"); /* add terminating character */
255
256	/* Order of next two lines is *very* important.
257	 * When we are sending a little amount of data,
258	 * the transfer may be completed inside the ops->write()
259	 * routine, because it's running with interrupts enabled.
260	 * In this case we *never* got WRITE_WAKEUP event,
261	 * if we did not request it before write operation.
262	 *       14 Oct 1994  Dmitry Gorodchanin.
263	 */
264	set_bit(TTY_DO_WRITE_WAKEUP, &sl->tty->flags);
265	actual = sl->tty->ops->write(sl->tty, sl->xbuff, strlen(sl->xbuff));
266	sl->xleft = strlen(sl->xbuff) - actual;
267	sl->xhead = sl->xbuff + actual;
268	sl->dev->stats.tx_bytes += cf->can_dlc;
269}
270
271/*
272 * Called by the driver when there's room for more data.  If we have
273 * more packets to send, we send them here.
274 */
275static void slcan_write_wakeup(struct tty_struct *tty)
276{
277	int actual;
278	struct slcan *sl = (struct slcan *) tty->disc_data;
279
280	/* First make sure we're connected. */
281	if (!sl || sl->magic != SLCAN_MAGIC || !netif_running(sl->dev))
282		return;
283
284	if (sl->xleft <= 0)  {
285		/* Now serial buffer is almost free & we can start
286		 * transmission of another packet */
287		sl->dev->stats.tx_packets++;
288		clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
289		netif_wake_queue(sl->dev);
290		return;
291	}
292
293	actual = tty->ops->write(tty, sl->xhead, sl->xleft);
294	sl->xleft -= actual;
295	sl->xhead += actual;
296}
297
298/* Send a can_frame to a TTY queue. */
299static netdev_tx_t slc_xmit(struct sk_buff *skb, struct net_device *dev)
300{
301	struct slcan *sl = netdev_priv(dev);
302
303	if (skb->len != sizeof(struct can_frame))
304		goto out;
305
306	spin_lock(&sl->lock);
307	if (!netif_running(dev))  {
308		spin_unlock(&sl->lock);
309		printk(KERN_WARNING "%s: xmit: iface is down\n", dev->name);
310		goto out;
311	}
312	if (sl->tty == NULL) {
313		spin_unlock(&sl->lock);
314		goto out;
315	}
316
317	netif_stop_queue(sl->dev);
318	slc_encaps(sl, (struct can_frame *) skb->data); /* encaps & send */
319	spin_unlock(&sl->lock);
320
321out:
322	kfree_skb(skb);
323	return NETDEV_TX_OK;
324}
325
326
327/******************************************
328 *   Routines looking at netdevice side.
329 ******************************************/
330
331/* Netdevice UP -> DOWN routine */
332static int slc_close(struct net_device *dev)
333{
334	struct slcan *sl = netdev_priv(dev);
335
336	spin_lock_bh(&sl->lock);
337	if (sl->tty) {
338		/* TTY discipline is running. */
339		clear_bit(TTY_DO_WRITE_WAKEUP, &sl->tty->flags);
340	}
341	netif_stop_queue(dev);
342	sl->rcount   = 0;
343	sl->xleft    = 0;
344	spin_unlock_bh(&sl->lock);
345
346	return 0;
347}
348
349/* Netdevice DOWN -> UP routine */
350static int slc_open(struct net_device *dev)
351{
352	struct slcan *sl = netdev_priv(dev);
353
354	if (sl->tty == NULL)
355		return -ENODEV;
356
357	sl->flags &= (1 << SLF_INUSE);
358	netif_start_queue(dev);
359	return 0;
360}
361
362/* Hook the destructor so we can free slcan devs at the right point in time */
363static void slc_free_netdev(struct net_device *dev)
364{
365	int i = dev->base_addr;
366	free_netdev(dev);
367	slcan_devs[i] = NULL;
368}
369
370static const struct net_device_ops slc_netdev_ops = {
371	.ndo_open               = slc_open,
372	.ndo_stop               = slc_close,
373	.ndo_start_xmit         = slc_xmit,
374};
375
376static void slc_setup(struct net_device *dev)
377{
378	dev->netdev_ops		= &slc_netdev_ops;
379	dev->destructor		= slc_free_netdev;
380
381	dev->hard_header_len	= 0;
382	dev->addr_len		= 0;
383	dev->tx_queue_len	= 10;
384
385	dev->mtu		= sizeof(struct can_frame);
386	dev->type		= ARPHRD_CAN;
387
388	/* New-style flags. */
389	dev->flags		= IFF_NOARP;
390	dev->features           = NETIF_F_HW_CSUM;
391}
392
393/******************************************
394  Routines looking at TTY side.
395 ******************************************/
396
397/*
398 * Handle the 'receiver data ready' interrupt.
399 * This function is called by the 'tty_io' module in the kernel when
400 * a block of SLCAN data has been received, which can now be decapsulated
401 * and sent on to some IP layer for further processing. This will not
402 * be re-entered while running but other ldisc functions may be called
403 * in parallel
404 */
405
406static void slcan_receive_buf(struct tty_struct *tty,
407			      const unsigned char *cp, char *fp, int count)
408{
409	struct slcan *sl = (struct slcan *) tty->disc_data;
410
411	if (!sl || sl->magic != SLCAN_MAGIC || !netif_running(sl->dev))
412		return;
413
414	/* Read the characters out of the buffer */
415	while (count--) {
416		if (fp && *fp++) {
417			if (!test_and_set_bit(SLF_ERROR, &sl->flags))
418				sl->dev->stats.rx_errors++;
419			cp++;
420			continue;
421		}
422		slcan_unesc(sl, *cp++);
423	}
424}
425
426/************************************
427 *  slcan_open helper routines.
428 ************************************/
429
430/* Collect hanged up channels */
431static void slc_sync(void)
432{
433	int i;
434	struct net_device *dev;
435	struct slcan	  *sl;
436
437	for (i = 0; i < maxdev; i++) {
438		dev = slcan_devs[i];
439		if (dev == NULL)
440			break;
441
442		sl = netdev_priv(dev);
443		if (sl->tty)
444			continue;
445		if (dev->flags & IFF_UP)
446			dev_close(dev);
447	}
448}
449
450/* Find a free SLCAN channel, and link in this `tty' line. */
451static struct slcan *slc_alloc(dev_t line)
452{
453	int i;
454	char name[IFNAMSIZ];
455	struct net_device *dev = NULL;
456	struct slcan       *sl;
457
458	for (i = 0; i < maxdev; i++) {
459		dev = slcan_devs[i];
460		if (dev == NULL)
461			break;
462
463	}
464
465	/* Sorry, too many, all slots in use */
466	if (i >= maxdev)
467		return NULL;
468
469	sprintf(name, "slcan%d", i);
470	dev = alloc_netdev(sizeof(*sl), name, slc_setup);
471	if (!dev)
472		return NULL;
473
474	dev->base_addr  = i;
475	sl = netdev_priv(dev);
476
477	/* Initialize channel control data */
478	sl->magic = SLCAN_MAGIC;
479	sl->dev	= dev;
480	spin_lock_init(&sl->lock);
481	slcan_devs[i] = dev;
482
483	return sl;
484}
485
486/*
487 * Open the high-level part of the SLCAN channel.
488 * This function is called by the TTY module when the
489 * SLCAN line discipline is called for.  Because we are
490 * sure the tty line exists, we only have to link it to
491 * a free SLCAN channel...
492 *
493 * Called in process context serialized from other ldisc calls.
494 */
495
496static int slcan_open(struct tty_struct *tty)
497{
498	struct slcan *sl;
499	int err;
500
501	if (!capable(CAP_NET_ADMIN))
502		return -EPERM;
503
504	if (tty->ops->write == NULL)
505		return -EOPNOTSUPP;
506
507	/* RTnetlink lock is misused here to serialize concurrent
508	   opens of slcan channels. There are better ways, but it is
509	   the simplest one.
510	 */
511	rtnl_lock();
512
513	/* Collect hanged up channels. */
514	slc_sync();
515
516	sl = tty->disc_data;
517
518	err = -EEXIST;
519	/* First make sure we're not already connected. */
520	if (sl && sl->magic == SLCAN_MAGIC)
521		goto err_exit;
522
523	/* OK.  Find a free SLCAN channel to use. */
524	err = -ENFILE;
525	sl = slc_alloc(tty_devnum(tty));
526	if (sl == NULL)
527		goto err_exit;
528
529	sl->tty = tty;
530	tty->disc_data = sl;
531
532	if (!test_bit(SLF_INUSE, &sl->flags)) {
533		/* Perform the low-level SLCAN initialization. */
534		sl->rcount   = 0;
535		sl->xleft    = 0;
536
537		set_bit(SLF_INUSE, &sl->flags);
538
539		err = register_netdevice(sl->dev);
540		if (err)
541			goto err_free_chan;
542	}
543
544	/* Done.  We have linked the TTY line to a channel. */
545	rtnl_unlock();
546	tty->receive_room = 65536;	/* We don't flow control */
547
548	/* TTY layer expects 0 on success */
549	return 0;
550
551err_free_chan:
552	sl->tty = NULL;
553	tty->disc_data = NULL;
554	clear_bit(SLF_INUSE, &sl->flags);
555
556err_exit:
557	rtnl_unlock();
558
559	/* Count references from TTY module */
560	return err;
561}
562
563/*
564 * Close down a SLCAN channel.
565 * This means flushing out any pending queues, and then returning. This
566 * call is serialized against other ldisc functions.
567 *
568 * We also use this method for a hangup event.
569 */
570
571static void slcan_close(struct tty_struct *tty)
572{
573	struct slcan *sl = (struct slcan *) tty->disc_data;
574
575	/* First make sure we're connected. */
576	if (!sl || sl->magic != SLCAN_MAGIC || sl->tty != tty)
577		return;
578
579	tty->disc_data = NULL;
580	sl->tty = NULL;
581
582	/* Flush network side */
583	unregister_netdev(sl->dev);
584	/* This will complete via sl_free_netdev */
585}
586
587static int slcan_hangup(struct tty_struct *tty)
588{
589	slcan_close(tty);
590	return 0;
591}
592
593/* Perform I/O control on an active SLCAN channel. */
594static int slcan_ioctl(struct tty_struct *tty, struct file *file,
595		       unsigned int cmd, unsigned long arg)
596{
597	struct slcan *sl = (struct slcan *) tty->disc_data;
598	unsigned int tmp;
599
600	/* First make sure we're connected. */
601	if (!sl || sl->magic != SLCAN_MAGIC)
602		return -EINVAL;
603
604	switch (cmd) {
605	case SIOCGIFNAME:
606		tmp = strlen(sl->dev->name) + 1;
607		if (copy_to_user((void __user *)arg, sl->dev->name, tmp))
608			return -EFAULT;
609		return 0;
610
611	case SIOCSIFHWADDR:
612		return -EINVAL;
613
614	default:
615		return tty_mode_ioctl(tty, file, cmd, arg);
616	}
617}
618
619static struct tty_ldisc_ops slc_ldisc = {
620	.owner		= THIS_MODULE,
621	.magic		= TTY_LDISC_MAGIC,
622	.name		= "slcan",
623	.open		= slcan_open,
624	.close		= slcan_close,
625	.hangup		= slcan_hangup,
626	.ioctl		= slcan_ioctl,
627	.receive_buf	= slcan_receive_buf,
628	.write_wakeup	= slcan_write_wakeup,
629};
630
631static int __init slcan_init(void)
632{
633	int status;
634
635	if (maxdev < 4)
636		maxdev = 4; /* Sanity */
637
638	printk(banner);
639	printk(KERN_INFO "slcan: %d dynamic interface channels.\n", maxdev);
640
641	slcan_devs = kzalloc(sizeof(struct net_device *)*maxdev, GFP_KERNEL);
642	if (!slcan_devs) {
643		printk(KERN_ERR "slcan: can't allocate slcan device array!\n");
644		return -ENOMEM;
645	}
646
647	/* Fill in our line protocol discipline, and register it */
648	status = tty_register_ldisc(N_SLCAN, &slc_ldisc);
649	if (status)  {
650		printk(KERN_ERR "slcan: can't register line discipline\n");
651		kfree(slcan_devs);
652	}
653	return status;
654}
655
656static void __exit slcan_exit(void)
657{
658	int i;
659	struct net_device *dev;
660	struct slcan *sl;
661	unsigned long timeout = jiffies + HZ;
662	int busy = 0;
663
664	if (slcan_devs == NULL)
665		return;
666
667	/* First of all: check for active disciplines and hangup them.
668	 */
669	do {
670		if (busy)
671			msleep_interruptible(100);
672
673		busy = 0;
674		for (i = 0; i < maxdev; i++) {
675			dev = slcan_devs[i];
676			if (!dev)
677				continue;
678			sl = netdev_priv(dev);
679			spin_lock_bh(&sl->lock);
680			if (sl->tty) {
681				busy++;
682				tty_hangup(sl->tty);
683			}
684			spin_unlock_bh(&sl->lock);
685		}
686	} while (busy && time_before(jiffies, timeout));
687
688	/* FIXME: hangup is async so we should wait when doing this second
689	   phase */
690
691	for (i = 0; i < maxdev; i++) {
692		dev = slcan_devs[i];
693		if (!dev)
694			continue;
695		slcan_devs[i] = NULL;
696
697		sl = netdev_priv(dev);
698		if (sl->tty) {
699			printk(KERN_ERR "%s: tty discipline still running\n",
700			       dev->name);
701			/* Intentionally leak the control block. */
702			dev->destructor = NULL;
703		}
704
705		unregister_netdev(dev);
706	}
707
708	kfree(slcan_devs);
709	slcan_devs = NULL;
710
711	i = tty_unregister_ldisc(N_SLCAN);
712	if (i)
713		printk(KERN_ERR "slcan: can't unregister ldisc (err %d)\n", i);
714}
715
716module_init(slcan_init);
717module_exit(slcan_exit);
718