slcan.c revision 81fc70d86527a1450560709500ca5f52e661da1f 
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	unsigned char		leased;
101	dev_t			line;
102	pid_t			pid;
103};
104
105static struct net_device **slcan_devs;
106
107 /************************************************************************
108  *			SLCAN ENCAPSULATION FORMAT			 *
109  ************************************************************************/
110
111/*
112 * A CAN frame has a can_id (11 bit standard frame format OR 29 bit extended
113 * frame format) a data length code (can_dlc) which can be from 0 to 8
114 * and up to <can_dlc> data bytes as payload.
115 * Additionally a CAN frame may become a remote transmission frame if the
116 * RTR-bit is set. This causes another ECU to send a CAN frame with the
117 * given can_id.
118 *
119 * The SLCAN ASCII representation of these different frame types is:
120 * <type> <id> <dlc> <data>*
121 *
122 * Extended frames (29 bit) are defined by capital characters in the type.
123 * RTR frames are defined as 'r' types - normal frames have 't' type:
124 * t => 11 bit data frame
125 * r => 11 bit RTR frame
126 * T => 29 bit data frame
127 * R => 29 bit RTR frame
128 *
129 * The <id> is 3 (standard) or 8 (extended) bytes in ASCII Hex (base64).
130 * The <dlc> is a one byte ASCII number ('0' - '8')
131 * The <data> section has at much ASCII Hex bytes as defined by the <dlc>
132 *
133 * Examples:
134 *
135 * t1230 : can_id 0x123, can_dlc 0, no data
136 * t4563112233 : can_id 0x456, can_dlc 3, data 0x11 0x22 0x33
137 * T12ABCDEF2AA55 : extended can_id 0x12ABCDEF, can_dlc 2, data 0xAA 0x55
138 * r1230 : can_id 0x123, can_dlc 0, no data, remote transmission request
139 *
140 */
141
142 /************************************************************************
143  *			STANDARD SLCAN DECAPSULATION			 *
144  ************************************************************************/
145
146/* Send one completely decapsulated can_frame to the network layer */
147static void slc_bump(struct slcan *sl)
148{
149	struct sk_buff *skb;
150	struct can_frame cf;
151	int i, dlc_pos, tmp;
152	unsigned long ultmp;
153	char cmd = sl->rbuff[0];
154
155	if ((cmd != 't') && (cmd != 'T') && (cmd != 'r') && (cmd != 'R'))
156		return;
157
158	if (cmd & 0x20) /* tiny chars 'r' 't' => standard frame format */
159		dlc_pos = 4; /* dlc position tiiid */
160	else
161		dlc_pos = 9; /* dlc position Tiiiiiiiid */
162
163	if (!((sl->rbuff[dlc_pos] >= '0') && (sl->rbuff[dlc_pos] < '9')))
164		return;
165
166	cf.can_dlc = sl->rbuff[dlc_pos] - '0'; /* get can_dlc from ASCII val */
167
168	sl->rbuff[dlc_pos] = 0; /* terminate can_id string */
169
170	if (strict_strtoul(sl->rbuff+1, 16, &ultmp))
171		return;
172
173	cf.can_id = ultmp;
174
175	if (!(cmd & 0x20)) /* NO tiny chars => extended frame format */
176		cf.can_id |= CAN_EFF_FLAG;
177
178	if ((cmd | 0x20) == 'r') /* RTR frame */
179		cf.can_id |= CAN_RTR_FLAG;
180
181	*(u64 *) (&cf.data) = 0; /* clear payload */
182
183	for (i = 0, dlc_pos++; i < cf.can_dlc; i++) {
184		tmp = hex_to_bin(sl->rbuff[dlc_pos++]);
185		if (tmp < 0)
186			return;
187		cf.data[i] = (tmp << 4);
188		tmp = hex_to_bin(sl->rbuff[dlc_pos++]);
189		if (tmp < 0)
190			return;
191		cf.data[i] |= tmp;
192	}
193
194	skb = dev_alloc_skb(sizeof(struct can_frame));
195	if (!skb)
196		return;
197
198	skb->dev = sl->dev;
199	skb->protocol = htons(ETH_P_CAN);
200	skb->pkt_type = PACKET_BROADCAST;
201	skb->ip_summed = CHECKSUM_UNNECESSARY;
202	memcpy(skb_put(skb, sizeof(struct can_frame)),
203	       &cf, sizeof(struct can_frame));
204	netif_rx(skb);
205
206	sl->dev->stats.rx_packets++;
207	sl->dev->stats.rx_bytes += cf.can_dlc;
208}
209
210/* parse tty input stream */
211static void slcan_unesc(struct slcan *sl, unsigned char s)
212{
213
214	if ((s == '\r') || (s == '\a')) { /* CR or BEL ends the pdu */
215		if (!test_and_clear_bit(SLF_ERROR, &sl->flags) &&
216		    (sl->rcount > 4))  {
217			slc_bump(sl);
218		}
219		sl->rcount = 0;
220	} else {
221		if (!test_bit(SLF_ERROR, &sl->flags))  {
222			if (sl->rcount < SLC_MTU)  {
223				sl->rbuff[sl->rcount++] = s;
224				return;
225			} else {
226				sl->dev->stats.rx_over_errors++;
227				set_bit(SLF_ERROR, &sl->flags);
228			}
229		}
230	}
231}
232
233 /************************************************************************
234  *			STANDARD SLCAN ENCAPSULATION			 *
235  ************************************************************************/
236
237/* Encapsulate one can_frame and stuff into a TTY queue. */
238static void slc_encaps(struct slcan *sl, struct can_frame *cf)
239{
240	int actual, idx, i;
241	char cmd;
242
243	if (cf->can_id & CAN_RTR_FLAG)
244		cmd = 'R'; /* becomes 'r' in standard frame format */
245	else
246		cmd = 'T'; /* becomes 't' in standard frame format */
247
248	if (cf->can_id & CAN_EFF_FLAG)
249		sprintf(sl->xbuff, "%c%08X%d", cmd,
250			cf->can_id & CAN_EFF_MASK, cf->can_dlc);
251	else
252		sprintf(sl->xbuff, "%c%03X%d", cmd | 0x20,
253			cf->can_id & CAN_SFF_MASK, cf->can_dlc);
254
255	idx = strlen(sl->xbuff);
256
257	for (i = 0; i < cf->can_dlc; i++)
258		sprintf(&sl->xbuff[idx + 2*i], "%02X", cf->data[i]);
259
260	strcat(sl->xbuff, "\r"); /* add terminating character */
261
262	/* Order of next two lines is *very* important.
263	 * When we are sending a little amount of data,
264	 * the transfer may be completed inside the ops->write()
265	 * routine, because it's running with interrupts enabled.
266	 * In this case we *never* got WRITE_WAKEUP event,
267	 * if we did not request it before write operation.
268	 *       14 Oct 1994  Dmitry Gorodchanin.
269	 */
270	set_bit(TTY_DO_WRITE_WAKEUP, &sl->tty->flags);
271	actual = sl->tty->ops->write(sl->tty, sl->xbuff, strlen(sl->xbuff));
272	sl->xleft = strlen(sl->xbuff) - actual;
273	sl->xhead = sl->xbuff + actual;
274	sl->dev->stats.tx_bytes += cf->can_dlc;
275}
276
277/*
278 * Called by the driver when there's room for more data.  If we have
279 * more packets to send, we send them here.
280 */
281static void slcan_write_wakeup(struct tty_struct *tty)
282{
283	int actual;
284	struct slcan *sl = (struct slcan *) tty->disc_data;
285
286	/* First make sure we're connected. */
287	if (!sl || sl->magic != SLCAN_MAGIC || !netif_running(sl->dev))
288		return;
289
290	if (sl->xleft <= 0)  {
291		/* Now serial buffer is almost free & we can start
292		 * transmission of another packet */
293		sl->dev->stats.tx_packets++;
294		clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
295		netif_wake_queue(sl->dev);
296		return;
297	}
298
299	actual = tty->ops->write(tty, sl->xhead, sl->xleft);
300	sl->xleft -= actual;
301	sl->xhead += actual;
302}
303
304/* Send a can_frame to a TTY queue. */
305static netdev_tx_t slc_xmit(struct sk_buff *skb, struct net_device *dev)
306{
307	struct slcan *sl = netdev_priv(dev);
308
309	if (skb->len != sizeof(struct can_frame))
310		goto out;
311
312	spin_lock(&sl->lock);
313	if (!netif_running(dev))  {
314		spin_unlock(&sl->lock);
315		printk(KERN_WARNING "%s: xmit: iface is down\n", dev->name);
316		goto out;
317	}
318	if (sl->tty == NULL) {
319		spin_unlock(&sl->lock);
320		goto out;
321	}
322
323	netif_stop_queue(sl->dev);
324	slc_encaps(sl, (struct can_frame *) skb->data); /* encaps & send */
325	spin_unlock(&sl->lock);
326
327out:
328	kfree_skb(skb);
329	return NETDEV_TX_OK;
330}
331
332
333/******************************************
334 *   Routines looking at netdevice side.
335 ******************************************/
336
337/* Netdevice UP -> DOWN routine */
338static int slc_close(struct net_device *dev)
339{
340	struct slcan *sl = netdev_priv(dev);
341
342	spin_lock_bh(&sl->lock);
343	if (sl->tty) {
344		/* TTY discipline is running. */
345		clear_bit(TTY_DO_WRITE_WAKEUP, &sl->tty->flags);
346	}
347	netif_stop_queue(dev);
348	sl->rcount   = 0;
349	sl->xleft    = 0;
350	spin_unlock_bh(&sl->lock);
351
352	return 0;
353}
354
355/* Netdevice DOWN -> UP routine */
356static int slc_open(struct net_device *dev)
357{
358	struct slcan *sl = netdev_priv(dev);
359
360	if (sl->tty == NULL)
361		return -ENODEV;
362
363	sl->flags &= (1 << SLF_INUSE);
364	netif_start_queue(dev);
365	return 0;
366}
367
368/* Hook the destructor so we can free slcan devs at the right point in time */
369static void slc_free_netdev(struct net_device *dev)
370{
371	int i = dev->base_addr;
372	free_netdev(dev);
373	slcan_devs[i] = NULL;
374}
375
376static const struct net_device_ops slc_netdev_ops = {
377	.ndo_open               = slc_open,
378	.ndo_stop               = slc_close,
379	.ndo_start_xmit         = slc_xmit,
380};
381
382static void slc_setup(struct net_device *dev)
383{
384	dev->netdev_ops		= &slc_netdev_ops;
385	dev->destructor		= slc_free_netdev;
386
387	dev->hard_header_len	= 0;
388	dev->addr_len		= 0;
389	dev->tx_queue_len	= 10;
390
391	dev->mtu		= sizeof(struct can_frame);
392	dev->type		= ARPHRD_CAN;
393
394	/* New-style flags. */
395	dev->flags		= IFF_NOARP;
396	dev->features           = NETIF_F_NO_CSUM;
397}
398
399/******************************************
400  Routines looking at TTY side.
401 ******************************************/
402
403/*
404 * Handle the 'receiver data ready' interrupt.
405 * This function is called by the 'tty_io' module in the kernel when
406 * a block of SLCAN data has been received, which can now be decapsulated
407 * and sent on to some IP layer for further processing. This will not
408 * be re-entered while running but other ldisc functions may be called
409 * in parallel
410 */
411
412static void slcan_receive_buf(struct tty_struct *tty,
413			      const unsigned char *cp, char *fp, int count)
414{
415	struct slcan *sl = (struct slcan *) tty->disc_data;
416
417	if (!sl || sl->magic != SLCAN_MAGIC || !netif_running(sl->dev))
418		return;
419
420	/* Read the characters out of the buffer */
421	while (count--) {
422		if (fp && *fp++) {
423			if (!test_and_set_bit(SLF_ERROR, &sl->flags))
424				sl->dev->stats.rx_errors++;
425			cp++;
426			continue;
427		}
428		slcan_unesc(sl, *cp++);
429	}
430}
431
432/************************************
433 *  slcan_open helper routines.
434 ************************************/
435
436/* Collect hanged up channels */
437static void slc_sync(void)
438{
439	int i;
440	struct net_device *dev;
441	struct slcan	  *sl;
442
443	for (i = 0; i < maxdev; i++) {
444		dev = slcan_devs[i];
445		if (dev == NULL)
446			break;
447
448		sl = netdev_priv(dev);
449		if (sl->tty || sl->leased)
450			continue;
451		if (dev->flags & IFF_UP)
452			dev_close(dev);
453	}
454}
455
456/* Find a free SLCAN channel, and link in this `tty' line. */
457static struct slcan *slc_alloc(dev_t line)
458{
459	int i;
460	char name[IFNAMSIZ];
461	struct net_device *dev = NULL;
462	struct slcan       *sl;
463
464	for (i = 0; i < maxdev; i++) {
465		dev = slcan_devs[i];
466		if (dev == NULL)
467			break;
468
469	}
470
471	/* Sorry, too many, all slots in use */
472	if (i >= maxdev)
473		return NULL;
474
475	sprintf(name, "slcan%d", i);
476	dev = alloc_netdev(sizeof(*sl), name, slc_setup);
477	if (!dev)
478		return NULL;
479
480	dev->base_addr  = i;
481	sl = netdev_priv(dev);
482
483	/* Initialize channel control data */
484	sl->magic = SLCAN_MAGIC;
485	sl->dev	= dev;
486	spin_lock_init(&sl->lock);
487	slcan_devs[i] = dev;
488
489	return sl;
490}
491
492/*
493 * Open the high-level part of the SLCAN channel.
494 * This function is called by the TTY module when the
495 * SLCAN line discipline is called for.  Because we are
496 * sure the tty line exists, we only have to link it to
497 * a free SLCAN channel...
498 *
499 * Called in process context serialized from other ldisc calls.
500 */
501
502static int slcan_open(struct tty_struct *tty)
503{
504	struct slcan *sl;
505	int err;
506
507	if (!capable(CAP_NET_ADMIN))
508		return -EPERM;
509
510	if (tty->ops->write == NULL)
511		return -EOPNOTSUPP;
512
513	/* RTnetlink lock is misused here to serialize concurrent
514	   opens of slcan channels. There are better ways, but it is
515	   the simplest one.
516	 */
517	rtnl_lock();
518
519	/* Collect hanged up channels. */
520	slc_sync();
521
522	sl = tty->disc_data;
523
524	err = -EEXIST;
525	/* First make sure we're not already connected. */
526	if (sl && sl->magic == SLCAN_MAGIC)
527		goto err_exit;
528
529	/* OK.  Find a free SLCAN channel to use. */
530	err = -ENFILE;
531	sl = slc_alloc(tty_devnum(tty));
532	if (sl == NULL)
533		goto err_exit;
534
535	sl->tty = tty;
536	tty->disc_data = sl;
537	sl->line = tty_devnum(tty);
538	sl->pid = current->pid;
539
540	if (!test_bit(SLF_INUSE, &sl->flags)) {
541		/* Perform the low-level SLCAN initialization. */
542		sl->rcount   = 0;
543		sl->xleft    = 0;
544
545		set_bit(SLF_INUSE, &sl->flags);
546
547		err = register_netdevice(sl->dev);
548		if (err)
549			goto err_free_chan;
550	}
551
552	/* Done.  We have linked the TTY line to a channel. */
553	rtnl_unlock();
554	tty->receive_room = 65536;	/* We don't flow control */
555
556	/* TTY layer expects 0 on success */
557	return 0;
558
559err_free_chan:
560	sl->tty = NULL;
561	tty->disc_data = NULL;
562	clear_bit(SLF_INUSE, &sl->flags);
563
564err_exit:
565	rtnl_unlock();
566
567	/* Count references from TTY module */
568	return err;
569}
570
571/*
572 * Close down a SLCAN channel.
573 * This means flushing out any pending queues, and then returning. This
574 * call is serialized against other ldisc functions.
575 *
576 * We also use this method for a hangup event.
577 */
578
579static void slcan_close(struct tty_struct *tty)
580{
581	struct slcan *sl = (struct slcan *) tty->disc_data;
582
583	/* First make sure we're connected. */
584	if (!sl || sl->magic != SLCAN_MAGIC || sl->tty != tty)
585		return;
586
587	tty->disc_data = NULL;
588	sl->tty = NULL;
589	if (!sl->leased)
590		sl->line = 0;
591
592	/* Flush network side */
593	unregister_netdev(sl->dev);
594	/* This will complete via sl_free_netdev */
595}
596
597static int slcan_hangup(struct tty_struct *tty)
598{
599	slcan_close(tty);
600	return 0;
601}
602
603/* Perform I/O control on an active SLCAN channel. */
604static int slcan_ioctl(struct tty_struct *tty, struct file *file,
605		       unsigned int cmd, unsigned long arg)
606{
607	struct slcan *sl = (struct slcan *) tty->disc_data;
608	unsigned int tmp;
609
610	/* First make sure we're connected. */
611	if (!sl || sl->magic != SLCAN_MAGIC)
612		return -EINVAL;
613
614	switch (cmd) {
615	case SIOCGIFNAME:
616		tmp = strlen(sl->dev->name) + 1;
617		if (copy_to_user((void __user *)arg, sl->dev->name, tmp))
618			return -EFAULT;
619		return 0;
620
621	case SIOCSIFHWADDR:
622		return -EINVAL;
623
624	default:
625		return tty_mode_ioctl(tty, file, cmd, arg);
626	}
627}
628
629static struct tty_ldisc_ops slc_ldisc = {
630	.owner		= THIS_MODULE,
631	.magic		= TTY_LDISC_MAGIC,
632	.name		= "slcan",
633	.open		= slcan_open,
634	.close		= slcan_close,
635	.hangup		= slcan_hangup,
636	.ioctl		= slcan_ioctl,
637	.receive_buf	= slcan_receive_buf,
638	.write_wakeup	= slcan_write_wakeup,
639};
640
641static int __init slcan_init(void)
642{
643	int status;
644
645	if (maxdev < 4)
646		maxdev = 4; /* Sanity */
647
648	printk(banner);
649	printk(KERN_INFO "slcan: %d dynamic interface channels.\n", maxdev);
650
651	slcan_devs = kzalloc(sizeof(struct net_device *)*maxdev, GFP_KERNEL);
652	if (!slcan_devs) {
653		printk(KERN_ERR "slcan: can't allocate slcan device array!\n");
654		return -ENOMEM;
655	}
656
657	/* Fill in our line protocol discipline, and register it */
658	status = tty_register_ldisc(N_SLCAN, &slc_ldisc);
659	if (status)  {
660		printk(KERN_ERR "slcan: can't register line discipline\n");
661		kfree(slcan_devs);
662	}
663	return status;
664}
665
666static void __exit slcan_exit(void)
667{
668	int i;
669	struct net_device *dev;
670	struct slcan *sl;
671	unsigned long timeout = jiffies + HZ;
672	int busy = 0;
673
674	if (slcan_devs == NULL)
675		return;
676
677	/* First of all: check for active disciplines and hangup them.
678	 */
679	do {
680		if (busy)
681			msleep_interruptible(100);
682
683		busy = 0;
684		for (i = 0; i < maxdev; i++) {
685			dev = slcan_devs[i];
686			if (!dev)
687				continue;
688			sl = netdev_priv(dev);
689			spin_lock_bh(&sl->lock);
690			if (sl->tty) {
691				busy++;
692				tty_hangup(sl->tty);
693			}
694			spin_unlock_bh(&sl->lock);
695		}
696	} while (busy && time_before(jiffies, timeout));
697
698	/* FIXME: hangup is async so we should wait when doing this second
699	   phase */
700
701	for (i = 0; i < maxdev; i++) {
702		dev = slcan_devs[i];
703		if (!dev)
704			continue;
705		slcan_devs[i] = NULL;
706
707		sl = netdev_priv(dev);
708		if (sl->tty) {
709			printk(KERN_ERR "%s: tty discipline still running\n",
710			       dev->name);
711			/* Intentionally leak the control block. */
712			dev->destructor = NULL;
713		}
714
715		unregister_netdev(dev);
716	}
717
718	kfree(slcan_devs);
719	slcan_devs = NULL;
720
721	i = tty_unregister_ldisc(N_SLCAN);
722	if (i)
723		printk(KERN_ERR "slcan: can't unregister ldisc (err %d)\n", i);
724}
725
726module_init(slcan_init);
727module_exit(slcan_exit);
728