slcan.c revision b1c43f82c5aa265442f82dba31ce985ebb7aa71c 
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/can.h>
60
61static __initdata const char banner[] =
62	KERN_INFO "slcan: serial line CAN interface driver\n";
63
64MODULE_ALIAS_LDISC(N_SLCAN);
65MODULE_DESCRIPTION("serial line CAN interface");
66MODULE_LICENSE("GPL");
67MODULE_AUTHOR("Oliver Hartkopp <socketcan@hartkopp.net>");
68
69#define SLCAN_MAGIC 0x53CA
70
71static int maxdev = 10;		/* MAX number of SLCAN channels;
72				   This can be overridden with
73				   insmod slcan.ko maxdev=nnn	*/
74module_param(maxdev, int, 0);
75MODULE_PARM_DESC(maxdev, "Maximum number of slcan interfaces");
76
77/* maximum rx buffer len: extended CAN frame with timestamp */
78#define SLC_MTU (sizeof("T1111222281122334455667788EA5F\r")+1)
79
80struct slcan {
81	int			magic;
82
83	/* Various fields. */
84	struct tty_struct	*tty;		/* ptr to TTY structure	     */
85	struct net_device	*dev;		/* easy for intr handling    */
86	spinlock_t		lock;
87
88	/* These are pointers to the malloc()ed frame buffers. */
89	unsigned char		rbuff[SLC_MTU];	/* receiver buffer	     */
90	int			rcount;         /* received chars counter    */
91	unsigned char		xbuff[SLC_MTU];	/* transmitter buffer	     */
92	unsigned char		*xhead;         /* pointer to next XMIT byte */
93	int			xleft;          /* bytes left in XMIT queue  */
94
95	unsigned long		flags;		/* Flag values/ mode etc     */
96#define SLF_INUSE		0		/* Channel in use            */
97#define SLF_ERROR		1               /* Parity, etc. error        */
98
99	unsigned char		leased;
100	dev_t			line;
101	pid_t			pid;
102};
103
104static struct net_device **slcan_devs;
105
106 /************************************************************************
107  *			SLCAN ENCAPSULATION FORMAT			 *
108  ************************************************************************/
109
110/*
111 * A CAN frame has a can_id (11 bit standard frame format OR 29 bit extended
112 * frame format) a data length code (can_dlc) which can be from 0 to 8
113 * and up to <can_dlc> data bytes as payload.
114 * Additionally a CAN frame may become a remote transmission frame if the
115 * RTR-bit is set. This causes another ECU to send a CAN frame with the
116 * given can_id.
117 *
118 * The SLCAN ASCII representation of these different frame types is:
119 * <type> <id> <dlc> <data>*
120 *
121 * Extended frames (29 bit) are defined by capital characters in the type.
122 * RTR frames are defined as 'r' types - normal frames have 't' type:
123 * t => 11 bit data frame
124 * r => 11 bit RTR frame
125 * T => 29 bit data frame
126 * R => 29 bit RTR frame
127 *
128 * The <id> is 3 (standard) or 8 (extended) bytes in ASCII Hex (base64).
129 * The <dlc> is a one byte ASCII number ('0' - '8')
130 * The <data> section has at much ASCII Hex bytes as defined by the <dlc>
131 *
132 * Examples:
133 *
134 * t1230 : can_id 0x123, can_dlc 0, no data
135 * t4563112233 : can_id 0x456, can_dlc 3, data 0x11 0x22 0x33
136 * T12ABCDEF2AA55 : extended can_id 0x12ABCDEF, can_dlc 2, data 0xAA 0x55
137 * r1230 : can_id 0x123, can_dlc 0, no data, remote transmission request
138 *
139 */
140
141 /************************************************************************
142  *			STANDARD SLCAN DECAPSULATION			 *
143  ************************************************************************/
144
145static int asc2nibble(char c)
146{
147
148	if ((c >= '0') && (c <= '9'))
149		return c - '0';
150
151	if ((c >= 'A') && (c <= 'F'))
152		return c - 'A' + 10;
153
154	if ((c >= 'a') && (c <= 'f'))
155		return c - 'a' + 10;
156
157	return 16; /* error */
158}
159
160/* Send one completely decapsulated can_frame to the network layer */
161static void slc_bump(struct slcan *sl)
162{
163	struct sk_buff *skb;
164	struct can_frame cf;
165	int i, dlc_pos, tmp;
166	unsigned long ultmp;
167	char cmd = sl->rbuff[0];
168
169	if ((cmd != 't') && (cmd != 'T') && (cmd != 'r') && (cmd != 'R'))
170		return;
171
172	if (cmd & 0x20) /* tiny chars 'r' 't' => standard frame format */
173		dlc_pos = 4; /* dlc position tiiid */
174	else
175		dlc_pos = 9; /* dlc position Tiiiiiiiid */
176
177	if (!((sl->rbuff[dlc_pos] >= '0') && (sl->rbuff[dlc_pos] < '9')))
178		return;
179
180	cf.can_dlc = sl->rbuff[dlc_pos] - '0'; /* get can_dlc from ASCII val */
181
182	sl->rbuff[dlc_pos] = 0; /* terminate can_id string */
183
184	if (strict_strtoul(sl->rbuff+1, 16, &ultmp))
185		return;
186
187	cf.can_id = ultmp;
188
189	if (!(cmd & 0x20)) /* NO tiny chars => extended frame format */
190		cf.can_id |= CAN_EFF_FLAG;
191
192	if ((cmd | 0x20) == 'r') /* RTR frame */
193		cf.can_id |= CAN_RTR_FLAG;
194
195	*(u64 *) (&cf.data) = 0; /* clear payload */
196
197	for (i = 0, dlc_pos++; i < cf.can_dlc; i++) {
198
199		tmp = asc2nibble(sl->rbuff[dlc_pos++]);
200		if (tmp > 0x0F)
201			return;
202		cf.data[i] = (tmp << 4);
203		tmp = asc2nibble(sl->rbuff[dlc_pos++]);
204		if (tmp > 0x0F)
205			return;
206		cf.data[i] |= tmp;
207	}
208
209
210	skb = dev_alloc_skb(sizeof(struct can_frame));
211	if (!skb)
212		return;
213
214	skb->dev = sl->dev;
215	skb->protocol = htons(ETH_P_CAN);
216	skb->pkt_type = PACKET_BROADCAST;
217	skb->ip_summed = CHECKSUM_UNNECESSARY;
218	memcpy(skb_put(skb, sizeof(struct can_frame)),
219	       &cf, sizeof(struct can_frame));
220	netif_rx(skb);
221
222	sl->dev->stats.rx_packets++;
223	sl->dev->stats.rx_bytes += cf.can_dlc;
224}
225
226/* parse tty input stream */
227static void slcan_unesc(struct slcan *sl, unsigned char s)
228{
229
230	if ((s == '\r') || (s == '\a')) { /* CR or BEL ends the pdu */
231		if (!test_and_clear_bit(SLF_ERROR, &sl->flags) &&
232		    (sl->rcount > 4))  {
233			slc_bump(sl);
234		}
235		sl->rcount = 0;
236	} else {
237		if (!test_bit(SLF_ERROR, &sl->flags))  {
238			if (sl->rcount < SLC_MTU)  {
239				sl->rbuff[sl->rcount++] = s;
240				return;
241			} else {
242				sl->dev->stats.rx_over_errors++;
243				set_bit(SLF_ERROR, &sl->flags);
244			}
245		}
246	}
247}
248
249 /************************************************************************
250  *			STANDARD SLCAN ENCAPSULATION			 *
251  ************************************************************************/
252
253/* Encapsulate one can_frame and stuff into a TTY queue. */
254static void slc_encaps(struct slcan *sl, struct can_frame *cf)
255{
256	int actual, idx, i;
257	char cmd;
258
259	if (cf->can_id & CAN_RTR_FLAG)
260		cmd = 'R'; /* becomes 'r' in standard frame format */
261	else
262		cmd = 'T'; /* becomes 't' in standard frame format */
263
264	if (cf->can_id & CAN_EFF_FLAG)
265		sprintf(sl->xbuff, "%c%08X%d", cmd,
266			cf->can_id & CAN_EFF_MASK, cf->can_dlc);
267	else
268		sprintf(sl->xbuff, "%c%03X%d", cmd | 0x20,
269			cf->can_id & CAN_SFF_MASK, cf->can_dlc);
270
271	idx = strlen(sl->xbuff);
272
273	for (i = 0; i < cf->can_dlc; i++)
274		sprintf(&sl->xbuff[idx + 2*i], "%02X", cf->data[i]);
275
276	strcat(sl->xbuff, "\r"); /* add terminating character */
277
278	/* Order of next two lines is *very* important.
279	 * When we are sending a little amount of data,
280	 * the transfer may be completed inside the ops->write()
281	 * routine, because it's running with interrupts enabled.
282	 * In this case we *never* got WRITE_WAKEUP event,
283	 * if we did not request it before write operation.
284	 *       14 Oct 1994  Dmitry Gorodchanin.
285	 */
286	set_bit(TTY_DO_WRITE_WAKEUP, &sl->tty->flags);
287	actual = sl->tty->ops->write(sl->tty, sl->xbuff, strlen(sl->xbuff));
288	sl->xleft = strlen(sl->xbuff) - actual;
289	sl->xhead = sl->xbuff + actual;
290	sl->dev->stats.tx_bytes += cf->can_dlc;
291}
292
293/*
294 * Called by the driver when there's room for more data.  If we have
295 * more packets to send, we send them here.
296 */
297static void slcan_write_wakeup(struct tty_struct *tty)
298{
299	int actual;
300	struct slcan *sl = (struct slcan *) tty->disc_data;
301
302	/* First make sure we're connected. */
303	if (!sl || sl->magic != SLCAN_MAGIC || !netif_running(sl->dev))
304		return;
305
306	if (sl->xleft <= 0)  {
307		/* Now serial buffer is almost free & we can start
308		 * transmission of another packet */
309		sl->dev->stats.tx_packets++;
310		clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
311		netif_wake_queue(sl->dev);
312		return;
313	}
314
315	actual = tty->ops->write(tty, sl->xhead, sl->xleft);
316	sl->xleft -= actual;
317	sl->xhead += actual;
318}
319
320/* Send a can_frame to a TTY queue. */
321static netdev_tx_t slc_xmit(struct sk_buff *skb, struct net_device *dev)
322{
323	struct slcan *sl = netdev_priv(dev);
324
325	if (skb->len != sizeof(struct can_frame))
326		goto out;
327
328	spin_lock(&sl->lock);
329	if (!netif_running(dev))  {
330		spin_unlock(&sl->lock);
331		printk(KERN_WARNING "%s: xmit: iface is down\n", dev->name);
332		goto out;
333	}
334	if (sl->tty == NULL) {
335		spin_unlock(&sl->lock);
336		goto out;
337	}
338
339	netif_stop_queue(sl->dev);
340	slc_encaps(sl, (struct can_frame *) skb->data); /* encaps & send */
341	spin_unlock(&sl->lock);
342
343out:
344	kfree_skb(skb);
345	return NETDEV_TX_OK;
346}
347
348
349/******************************************
350 *   Routines looking at netdevice side.
351 ******************************************/
352
353/* Netdevice UP -> DOWN routine */
354static int slc_close(struct net_device *dev)
355{
356	struct slcan *sl = netdev_priv(dev);
357
358	spin_lock_bh(&sl->lock);
359	if (sl->tty) {
360		/* TTY discipline is running. */
361		clear_bit(TTY_DO_WRITE_WAKEUP, &sl->tty->flags);
362	}
363	netif_stop_queue(dev);
364	sl->rcount   = 0;
365	sl->xleft    = 0;
366	spin_unlock_bh(&sl->lock);
367
368	return 0;
369}
370
371/* Netdevice DOWN -> UP routine */
372static int slc_open(struct net_device *dev)
373{
374	struct slcan *sl = netdev_priv(dev);
375
376	if (sl->tty == NULL)
377		return -ENODEV;
378
379	sl->flags &= (1 << SLF_INUSE);
380	netif_start_queue(dev);
381	return 0;
382}
383
384/* Hook the destructor so we can free slcan devs at the right point in time */
385static void slc_free_netdev(struct net_device *dev)
386{
387	int i = dev->base_addr;
388	free_netdev(dev);
389	slcan_devs[i] = NULL;
390}
391
392static const struct net_device_ops slc_netdev_ops = {
393	.ndo_open               = slc_open,
394	.ndo_stop               = slc_close,
395	.ndo_start_xmit         = slc_xmit,
396};
397
398static void slc_setup(struct net_device *dev)
399{
400	dev->netdev_ops		= &slc_netdev_ops;
401	dev->destructor		= slc_free_netdev;
402
403	dev->hard_header_len	= 0;
404	dev->addr_len		= 0;
405	dev->tx_queue_len	= 10;
406
407	dev->mtu		= sizeof(struct can_frame);
408	dev->type		= ARPHRD_CAN;
409
410	/* New-style flags. */
411	dev->flags		= IFF_NOARP;
412	dev->features           = NETIF_F_NO_CSUM;
413}
414
415/******************************************
416  Routines looking at TTY side.
417 ******************************************/
418
419/*
420 * Handle the 'receiver data ready' interrupt.
421 * This function is called by the 'tty_io' module in the kernel when
422 * a block of SLCAN data has been received, which can now be decapsulated
423 * and sent on to some IP layer for further processing. This will not
424 * be re-entered while running but other ldisc functions may be called
425 * in parallel
426 */
427
428static unsigned int slcan_receive_buf(struct tty_struct *tty,
429			      const unsigned char *cp, char *fp, int count)
430{
431	struct slcan *sl = (struct slcan *) tty->disc_data;
432	int bytes = count;
433
434	if (!sl || sl->magic != SLCAN_MAGIC || !netif_running(sl->dev))
435		return -ENODEV;
436
437	/* Read the characters out of the buffer */
438	while (bytes--) {
439		if (fp && *fp++) {
440			if (!test_and_set_bit(SLF_ERROR, &sl->flags))
441				sl->dev->stats.rx_errors++;
442			cp++;
443			continue;
444		}
445		slcan_unesc(sl, *cp++);
446	}
447
448	return count;
449}
450
451/************************************
452 *  slcan_open helper routines.
453 ************************************/
454
455/* Collect hanged up channels */
456static void slc_sync(void)
457{
458	int i;
459	struct net_device *dev;
460	struct slcan	  *sl;
461
462	for (i = 0; i < maxdev; i++) {
463		dev = slcan_devs[i];
464		if (dev == NULL)
465			break;
466
467		sl = netdev_priv(dev);
468		if (sl->tty || sl->leased)
469			continue;
470		if (dev->flags & IFF_UP)
471			dev_close(dev);
472	}
473}
474
475/* Find a free SLCAN channel, and link in this `tty' line. */
476static struct slcan *slc_alloc(dev_t line)
477{
478	int i;
479	struct net_device *dev = NULL;
480	struct slcan       *sl;
481
482	if (slcan_devs == NULL)
483		return NULL;	/* Master array missing ! */
484
485	for (i = 0; i < maxdev; i++) {
486		dev = slcan_devs[i];
487		if (dev == NULL)
488			break;
489
490	}
491
492	/* Sorry, too many, all slots in use */
493	if (i >= maxdev)
494		return NULL;
495
496	if (dev) {
497		sl = netdev_priv(dev);
498		if (test_bit(SLF_INUSE, &sl->flags)) {
499			unregister_netdevice(dev);
500			dev = NULL;
501			slcan_devs[i] = NULL;
502		}
503	}
504
505	if (!dev) {
506		char name[IFNAMSIZ];
507		sprintf(name, "slcan%d", i);
508
509		dev = alloc_netdev(sizeof(*sl), name, slc_setup);
510		if (!dev)
511			return NULL;
512		dev->base_addr  = i;
513	}
514
515	sl = netdev_priv(dev);
516
517	/* Initialize channel control data */
518	sl->magic = SLCAN_MAGIC;
519	sl->dev	= dev;
520	spin_lock_init(&sl->lock);
521	slcan_devs[i] = dev;
522
523	return sl;
524}
525
526/*
527 * Open the high-level part of the SLCAN channel.
528 * This function is called by the TTY module when the
529 * SLCAN line discipline is called for.  Because we are
530 * sure the tty line exists, we only have to link it to
531 * a free SLCAN channel...
532 *
533 * Called in process context serialized from other ldisc calls.
534 */
535
536static int slcan_open(struct tty_struct *tty)
537{
538	struct slcan *sl;
539	int err;
540
541	if (!capable(CAP_NET_ADMIN))
542		return -EPERM;
543
544	if (tty->ops->write == NULL)
545		return -EOPNOTSUPP;
546
547	/* RTnetlink lock is misused here to serialize concurrent
548	   opens of slcan channels. There are better ways, but it is
549	   the simplest one.
550	 */
551	rtnl_lock();
552
553	/* Collect hanged up channels. */
554	slc_sync();
555
556	sl = tty->disc_data;
557
558	err = -EEXIST;
559	/* First make sure we're not already connected. */
560	if (sl && sl->magic == SLCAN_MAGIC)
561		goto err_exit;
562
563	/* OK.  Find a free SLCAN channel to use. */
564	err = -ENFILE;
565	sl = slc_alloc(tty_devnum(tty));
566	if (sl == NULL)
567		goto err_exit;
568
569	sl->tty = tty;
570	tty->disc_data = sl;
571	sl->line = tty_devnum(tty);
572	sl->pid = current->pid;
573
574	if (!test_bit(SLF_INUSE, &sl->flags)) {
575		/* Perform the low-level SLCAN initialization. */
576		sl->rcount   = 0;
577		sl->xleft    = 0;
578
579		set_bit(SLF_INUSE, &sl->flags);
580
581		err = register_netdevice(sl->dev);
582		if (err)
583			goto err_free_chan;
584	}
585
586	/* Done.  We have linked the TTY line to a channel. */
587	rtnl_unlock();
588	tty->receive_room = 65536;	/* We don't flow control */
589	return sl->dev->base_addr;
590
591err_free_chan:
592	sl->tty = NULL;
593	tty->disc_data = NULL;
594	clear_bit(SLF_INUSE, &sl->flags);
595
596err_exit:
597	rtnl_unlock();
598
599	/* Count references from TTY module */
600	return err;
601}
602
603/*
604 * Close down a SLCAN channel.
605 * This means flushing out any pending queues, and then returning. This
606 * call is serialized against other ldisc functions.
607 *
608 * We also use this method for a hangup event.
609 */
610
611static void slcan_close(struct tty_struct *tty)
612{
613	struct slcan *sl = (struct slcan *) tty->disc_data;
614
615	/* First make sure we're connected. */
616	if (!sl || sl->magic != SLCAN_MAGIC || sl->tty != tty)
617		return;
618
619	tty->disc_data = NULL;
620	sl->tty = NULL;
621	if (!sl->leased)
622		sl->line = 0;
623
624	/* Flush network side */
625	unregister_netdev(sl->dev);
626	/* This will complete via sl_free_netdev */
627}
628
629static int slcan_hangup(struct tty_struct *tty)
630{
631	slcan_close(tty);
632	return 0;
633}
634
635/* Perform I/O control on an active SLCAN channel. */
636static int slcan_ioctl(struct tty_struct *tty, struct file *file,
637		       unsigned int cmd, unsigned long arg)
638{
639	struct slcan *sl = (struct slcan *) tty->disc_data;
640	unsigned int tmp;
641
642	/* First make sure we're connected. */
643	if (!sl || sl->magic != SLCAN_MAGIC)
644		return -EINVAL;
645
646	switch (cmd) {
647	case SIOCGIFNAME:
648		tmp = strlen(sl->dev->name) + 1;
649		if (copy_to_user((void __user *)arg, sl->dev->name, tmp))
650			return -EFAULT;
651		return 0;
652
653	case SIOCSIFHWADDR:
654		return -EINVAL;
655
656	default:
657		return tty_mode_ioctl(tty, file, cmd, arg);
658	}
659}
660
661static struct tty_ldisc_ops slc_ldisc = {
662	.owner		= THIS_MODULE,
663	.magic		= TTY_LDISC_MAGIC,
664	.name		= "slcan",
665	.open		= slcan_open,
666	.close		= slcan_close,
667	.hangup		= slcan_hangup,
668	.ioctl		= slcan_ioctl,
669	.receive_buf	= slcan_receive_buf,
670	.write_wakeup	= slcan_write_wakeup,
671};
672
673static int __init slcan_init(void)
674{
675	int status;
676
677	if (maxdev < 4)
678		maxdev = 4; /* Sanity */
679
680	printk(banner);
681	printk(KERN_INFO "slcan: %d dynamic interface channels.\n", maxdev);
682
683	slcan_devs = kzalloc(sizeof(struct net_device *)*maxdev, GFP_KERNEL);
684	if (!slcan_devs) {
685		printk(KERN_ERR "slcan: can't allocate slcan device array!\n");
686		return -ENOMEM;
687	}
688
689	/* Fill in our line protocol discipline, and register it */
690	status = tty_register_ldisc(N_SLCAN, &slc_ldisc);
691	if (status)  {
692		printk(KERN_ERR "slcan: can't register line discipline\n");
693		kfree(slcan_devs);
694	}
695	return status;
696}
697
698static void __exit slcan_exit(void)
699{
700	int i;
701	struct net_device *dev;
702	struct slcan *sl;
703	unsigned long timeout = jiffies + HZ;
704	int busy = 0;
705
706	if (slcan_devs == NULL)
707		return;
708
709	/* First of all: check for active disciplines and hangup them.
710	 */
711	do {
712		if (busy)
713			msleep_interruptible(100);
714
715		busy = 0;
716		for (i = 0; i < maxdev; i++) {
717			dev = slcan_devs[i];
718			if (!dev)
719				continue;
720			sl = netdev_priv(dev);
721			spin_lock_bh(&sl->lock);
722			if (sl->tty) {
723				busy++;
724				tty_hangup(sl->tty);
725			}
726			spin_unlock_bh(&sl->lock);
727		}
728	} while (busy && time_before(jiffies, timeout));
729
730	/* FIXME: hangup is async so we should wait when doing this second
731	   phase */
732
733	for (i = 0; i < maxdev; i++) {
734		dev = slcan_devs[i];
735		if (!dev)
736			continue;
737		slcan_devs[i] = NULL;
738
739		sl = netdev_priv(dev);
740		if (sl->tty) {
741			printk(KERN_ERR "%s: tty discipline still running\n",
742			       dev->name);
743			/* Intentionally leak the control block. */
744			dev->destructor = NULL;
745		}
746
747		unregister_netdev(dev);
748	}
749
750	kfree(slcan_devs);
751	slcan_devs = NULL;
752
753	i = tty_unregister_ldisc(N_SLCAN);
754	if (i)
755		printk(KERN_ERR "slcan: can't unregister ldisc (err %d)\n", i);
756}
757
758module_init(slcan_init);
759module_exit(slcan_exit);
760