slcan.c revision 05780d9808f72dc28a5c3602e11a7c53aef972ad 
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, see http://www.gnu.org/licenses/gpl.html
22 *
23 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
24 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
25 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
26 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
27 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
28 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
29 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
30 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
31 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
32 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
33 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
34 * DAMAGE.
35 *
36 */
37
38#include <linux/module.h>
39#include <linux/moduleparam.h>
40
41#include <linux/uaccess.h>
42#include <linux/bitops.h>
43#include <linux/string.h>
44#include <linux/tty.h>
45#include <linux/errno.h>
46#include <linux/netdevice.h>
47#include <linux/skbuff.h>
48#include <linux/rtnetlink.h>
49#include <linux/if_arp.h>
50#include <linux/if_ether.h>
51#include <linux/sched.h>
52#include <linux/delay.h>
53#include <linux/init.h>
54#include <linux/kernel.h>
55#include <linux/can.h>
56#include <linux/can/skb.h>
57
58static __initconst const char banner[] =
59	KERN_INFO "slcan: serial line CAN interface driver\n";
60
61MODULE_ALIAS_LDISC(N_SLCAN);
62MODULE_DESCRIPTION("serial line CAN interface");
63MODULE_LICENSE("GPL");
64MODULE_AUTHOR("Oliver Hartkopp <socketcan@hartkopp.net>");
65
66#define SLCAN_MAGIC 0x53CA
67
68static int maxdev = 10;		/* MAX number of SLCAN channels;
69				   This can be overridden with
70				   insmod slcan.ko maxdev=nnn	*/
71module_param(maxdev, int, 0);
72MODULE_PARM_DESC(maxdev, "Maximum number of slcan interfaces");
73
74/* maximum rx buffer len: extended CAN frame with timestamp */
75#define SLC_MTU (sizeof("T1111222281122334455667788EA5F\r")+1)
76
77#define SLC_CMD_LEN 1
78#define SLC_SFF_ID_LEN 3
79#define SLC_EFF_ID_LEN 8
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, tmp;
148	u32 tmpid;
149	char *cmd = sl->rbuff;
150
151	cf.can_id = 0;
152
153	switch (*cmd) {
154	case 'r':
155		cf.can_id = CAN_RTR_FLAG;
156		/* fallthrough */
157	case 't':
158		/* store dlc ASCII value and terminate SFF CAN ID string */
159		cf.can_dlc = sl->rbuff[SLC_CMD_LEN + SLC_SFF_ID_LEN];
160		sl->rbuff[SLC_CMD_LEN + SLC_SFF_ID_LEN] = 0;
161		/* point to payload data behind the dlc */
162		cmd += SLC_CMD_LEN + SLC_SFF_ID_LEN + 1;
163		break;
164	case 'R':
165		cf.can_id = CAN_RTR_FLAG;
166		/* fallthrough */
167	case 'T':
168		cf.can_id |= CAN_EFF_FLAG;
169		/* store dlc ASCII value and terminate EFF CAN ID string */
170		cf.can_dlc = sl->rbuff[SLC_CMD_LEN + SLC_EFF_ID_LEN];
171		sl->rbuff[SLC_CMD_LEN + SLC_EFF_ID_LEN] = 0;
172		/* point to payload data behind the dlc */
173		cmd += SLC_CMD_LEN + SLC_EFF_ID_LEN + 1;
174		break;
175	default:
176		return;
177	}
178
179	if (kstrtou32(sl->rbuff + SLC_CMD_LEN, 16, &tmpid))
180		return;
181
182	cf.can_id |= tmpid;
183
184	/* get can_dlc from sanitized ASCII value */
185	if (cf.can_dlc >= '0' && cf.can_dlc < '9')
186		cf.can_dlc -= '0';
187	else
188		return;
189
190	*(u64 *) (&cf.data) = 0; /* clear payload */
191
192	/* RTR frames may have a dlc > 0 but they never have any data bytes */
193	if (!(cf.can_id & CAN_RTR_FLAG)) {
194		for (i = 0; i < cf.can_dlc; i++) {
195			tmp = hex_to_bin(*cmd++);
196			if (tmp < 0)
197				return;
198			cf.data[i] = (tmp << 4);
199			tmp = hex_to_bin(*cmd++);
200			if (tmp < 0)
201				return;
202			cf.data[i] |= tmp;
203		}
204	}
205
206	skb = dev_alloc_skb(sizeof(struct can_frame) +
207			    sizeof(struct can_skb_priv));
208	if (!skb)
209		return;
210
211	skb->dev = sl->dev;
212	skb->protocol = htons(ETH_P_CAN);
213	skb->pkt_type = PACKET_BROADCAST;
214	skb->ip_summed = CHECKSUM_UNNECESSARY;
215
216	can_skb_reserve(skb);
217	can_skb_prv(skb)->ifindex = sl->dev->ifindex;
218
219	memcpy(skb_put(skb, sizeof(struct can_frame)),
220	       &cf, sizeof(struct can_frame));
221	netif_rx_ni(skb);
222
223	sl->dev->stats.rx_packets++;
224	sl->dev->stats.rx_bytes += cf.can_dlc;
225}
226
227/* parse tty input stream */
228static void slcan_unesc(struct slcan *sl, unsigned char s)
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, i;
257	unsigned char *pos;
258	unsigned char *endpos;
259	canid_t id = cf->can_id;
260
261	pos = sl->xbuff;
262
263	if (cf->can_id & CAN_RTR_FLAG)
264		*pos = 'R'; /* becomes 'r' in standard frame format (SFF) */
265	else
266		*pos = 'T'; /* becomes 't' in standard frame format (SSF) */
267
268	/* determine number of chars for the CAN-identifier */
269	if (cf->can_id & CAN_EFF_FLAG) {
270		id &= CAN_EFF_MASK;
271		endpos = pos + SLC_EFF_ID_LEN;
272	} else {
273		*pos |= 0x20; /* convert R/T to lower case for SFF */
274		id &= CAN_SFF_MASK;
275		endpos = pos + SLC_SFF_ID_LEN;
276	}
277
278	/* build 3 (SFF) or 8 (EFF) digit CAN identifier */
279	pos++;
280	while (endpos >= pos) {
281		*endpos-- = hex_asc_upper[id & 0xf];
282		id >>= 4;
283	}
284
285	pos += (cf->can_id & CAN_EFF_FLAG) ? SLC_EFF_ID_LEN : SLC_SFF_ID_LEN;
286
287	*pos++ = cf->can_dlc + '0';
288
289	/* RTR frames may have a dlc > 0 but they never have any data bytes */
290	if (!(cf->can_id & CAN_RTR_FLAG)) {
291		for (i = 0; i < cf->can_dlc; i++)
292			pos = hex_byte_pack_upper(pos, cf->data[i]);
293	}
294
295	*pos++ = '\r';
296
297	/* Order of next two lines is *very* important.
298	 * When we are sending a little amount of data,
299	 * the transfer may be completed inside the ops->write()
300	 * routine, because it's running with interrupts enabled.
301	 * In this case we *never* got WRITE_WAKEUP event,
302	 * if we did not request it before write operation.
303	 *       14 Oct 1994  Dmitry Gorodchanin.
304	 */
305	set_bit(TTY_DO_WRITE_WAKEUP, &sl->tty->flags);
306	actual = sl->tty->ops->write(sl->tty, sl->xbuff, pos - sl->xbuff);
307	sl->xleft = (pos - sl->xbuff) - actual;
308	sl->xhead = sl->xbuff + actual;
309	sl->dev->stats.tx_bytes += cf->can_dlc;
310}
311
312/*
313 * Called by the driver when there's room for more data.  If we have
314 * more packets to send, we send them here.
315 */
316static void slcan_write_wakeup(struct tty_struct *tty)
317{
318	int actual;
319	struct slcan *sl = (struct slcan *) tty->disc_data;
320
321	/* First make sure we're connected. */
322	if (!sl || sl->magic != SLCAN_MAGIC || !netif_running(sl->dev))
323		return;
324
325	spin_lock(&sl->lock);
326	if (sl->xleft <= 0)  {
327		/* Now serial buffer is almost free & we can start
328		 * transmission of another packet */
329		sl->dev->stats.tx_packets++;
330		clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
331		spin_unlock(&sl->lock);
332		netif_wake_queue(sl->dev);
333		return;
334	}
335
336	actual = tty->ops->write(tty, sl->xhead, sl->xleft);
337	sl->xleft -= actual;
338	sl->xhead += actual;
339	spin_unlock(&sl->lock);
340}
341
342/* Send a can_frame to a TTY queue. */
343static netdev_tx_t slc_xmit(struct sk_buff *skb, struct net_device *dev)
344{
345	struct slcan *sl = netdev_priv(dev);
346
347	if (skb->len != sizeof(struct can_frame))
348		goto out;
349
350	spin_lock(&sl->lock);
351	if (!netif_running(dev))  {
352		spin_unlock(&sl->lock);
353		printk(KERN_WARNING "%s: xmit: iface is down\n", dev->name);
354		goto out;
355	}
356	if (sl->tty == NULL) {
357		spin_unlock(&sl->lock);
358		goto out;
359	}
360
361	netif_stop_queue(sl->dev);
362	slc_encaps(sl, (struct can_frame *) skb->data); /* encaps & send */
363	spin_unlock(&sl->lock);
364
365out:
366	kfree_skb(skb);
367	return NETDEV_TX_OK;
368}
369
370
371/******************************************
372 *   Routines looking at netdevice side.
373 ******************************************/
374
375/* Netdevice UP -> DOWN routine */
376static int slc_close(struct net_device *dev)
377{
378	struct slcan *sl = netdev_priv(dev);
379
380	spin_lock_bh(&sl->lock);
381	if (sl->tty) {
382		/* TTY discipline is running. */
383		clear_bit(TTY_DO_WRITE_WAKEUP, &sl->tty->flags);
384	}
385	netif_stop_queue(dev);
386	sl->rcount   = 0;
387	sl->xleft    = 0;
388	spin_unlock_bh(&sl->lock);
389
390	return 0;
391}
392
393/* Netdevice DOWN -> UP routine */
394static int slc_open(struct net_device *dev)
395{
396	struct slcan *sl = netdev_priv(dev);
397
398	if (sl->tty == NULL)
399		return -ENODEV;
400
401	sl->flags &= (1 << SLF_INUSE);
402	netif_start_queue(dev);
403	return 0;
404}
405
406/* Hook the destructor so we can free slcan devs at the right point in time */
407static void slc_free_netdev(struct net_device *dev)
408{
409	int i = dev->base_addr;
410	free_netdev(dev);
411	slcan_devs[i] = NULL;
412}
413
414static const struct net_device_ops slc_netdev_ops = {
415	.ndo_open               = slc_open,
416	.ndo_stop               = slc_close,
417	.ndo_start_xmit         = slc_xmit,
418};
419
420static void slc_setup(struct net_device *dev)
421{
422	dev->netdev_ops		= &slc_netdev_ops;
423	dev->destructor		= slc_free_netdev;
424
425	dev->hard_header_len	= 0;
426	dev->addr_len		= 0;
427	dev->tx_queue_len	= 10;
428
429	dev->mtu		= sizeof(struct can_frame);
430	dev->type		= ARPHRD_CAN;
431
432	/* New-style flags. */
433	dev->flags		= IFF_NOARP;
434	dev->features           = NETIF_F_HW_CSUM;
435}
436
437/******************************************
438  Routines looking at TTY side.
439 ******************************************/
440
441/*
442 * Handle the 'receiver data ready' interrupt.
443 * This function is called by the 'tty_io' module in the kernel when
444 * a block of SLCAN data has been received, which can now be decapsulated
445 * and sent on to some IP layer for further processing. This will not
446 * be re-entered while running but other ldisc functions may be called
447 * in parallel
448 */
449
450static void slcan_receive_buf(struct tty_struct *tty,
451			      const unsigned char *cp, char *fp, int count)
452{
453	struct slcan *sl = (struct slcan *) tty->disc_data;
454
455	if (!sl || sl->magic != SLCAN_MAGIC || !netif_running(sl->dev))
456		return;
457
458	/* Read the characters out of the buffer */
459	while (count--) {
460		if (fp && *fp++) {
461			if (!test_and_set_bit(SLF_ERROR, &sl->flags))
462				sl->dev->stats.rx_errors++;
463			cp++;
464			continue;
465		}
466		slcan_unesc(sl, *cp++);
467	}
468}
469
470/************************************
471 *  slcan_open helper routines.
472 ************************************/
473
474/* Collect hanged up channels */
475static void slc_sync(void)
476{
477	int i;
478	struct net_device *dev;
479	struct slcan	  *sl;
480
481	for (i = 0; i < maxdev; i++) {
482		dev = slcan_devs[i];
483		if (dev == NULL)
484			break;
485
486		sl = netdev_priv(dev);
487		if (sl->tty)
488			continue;
489		if (dev->flags & IFF_UP)
490			dev_close(dev);
491	}
492}
493
494/* Find a free SLCAN channel, and link in this `tty' line. */
495static struct slcan *slc_alloc(dev_t line)
496{
497	int i;
498	char name[IFNAMSIZ];
499	struct net_device *dev = NULL;
500	struct slcan       *sl;
501
502	for (i = 0; i < maxdev; i++) {
503		dev = slcan_devs[i];
504		if (dev == NULL)
505			break;
506
507	}
508
509	/* Sorry, too many, all slots in use */
510	if (i >= maxdev)
511		return NULL;
512
513	sprintf(name, "slcan%d", i);
514	dev = alloc_netdev(sizeof(*sl), name, slc_setup);
515	if (!dev)
516		return NULL;
517
518	dev->base_addr  = i;
519	sl = netdev_priv(dev);
520
521	/* Initialize channel control data */
522	sl->magic = SLCAN_MAGIC;
523	sl->dev	= dev;
524	spin_lock_init(&sl->lock);
525	slcan_devs[i] = dev;
526
527	return sl;
528}
529
530/*
531 * Open the high-level part of the SLCAN channel.
532 * This function is called by the TTY module when the
533 * SLCAN line discipline is called for.  Because we are
534 * sure the tty line exists, we only have to link it to
535 * a free SLCAN channel...
536 *
537 * Called in process context serialized from other ldisc calls.
538 */
539
540static int slcan_open(struct tty_struct *tty)
541{
542	struct slcan *sl;
543	int err;
544
545	if (!capable(CAP_NET_ADMIN))
546		return -EPERM;
547
548	if (tty->ops->write == NULL)
549		return -EOPNOTSUPP;
550
551	/* RTnetlink lock is misused here to serialize concurrent
552	   opens of slcan channels. There are better ways, but it is
553	   the simplest one.
554	 */
555	rtnl_lock();
556
557	/* Collect hanged up channels. */
558	slc_sync();
559
560	sl = tty->disc_data;
561
562	err = -EEXIST;
563	/* First make sure we're not already connected. */
564	if (sl && sl->magic == SLCAN_MAGIC)
565		goto err_exit;
566
567	/* OK.  Find a free SLCAN channel to use. */
568	err = -ENFILE;
569	sl = slc_alloc(tty_devnum(tty));
570	if (sl == NULL)
571		goto err_exit;
572
573	sl->tty = tty;
574	tty->disc_data = sl;
575
576	if (!test_bit(SLF_INUSE, &sl->flags)) {
577		/* Perform the low-level SLCAN initialization. */
578		sl->rcount   = 0;
579		sl->xleft    = 0;
580
581		set_bit(SLF_INUSE, &sl->flags);
582
583		err = register_netdevice(sl->dev);
584		if (err)
585			goto err_free_chan;
586	}
587
588	/* Done.  We have linked the TTY line to a channel. */
589	rtnl_unlock();
590	tty->receive_room = 65536;	/* We don't flow control */
591
592	/* TTY layer expects 0 on success */
593	return 0;
594
595err_free_chan:
596	sl->tty = NULL;
597	tty->disc_data = NULL;
598	clear_bit(SLF_INUSE, &sl->flags);
599
600err_exit:
601	rtnl_unlock();
602
603	/* Count references from TTY module */
604	return err;
605}
606
607/*
608 * Close down a SLCAN channel.
609 * This means flushing out any pending queues, and then returning. This
610 * call is serialized against other ldisc functions.
611 *
612 * We also use this method for a hangup event.
613 */
614
615static void slcan_close(struct tty_struct *tty)
616{
617	struct slcan *sl = (struct slcan *) tty->disc_data;
618
619	/* First make sure we're connected. */
620	if (!sl || sl->magic != SLCAN_MAGIC || sl->tty != tty)
621		return;
622
623	tty->disc_data = NULL;
624	sl->tty = NULL;
625
626	/* Flush network side */
627	unregister_netdev(sl->dev);
628	/* This will complete via sl_free_netdev */
629}
630
631static int slcan_hangup(struct tty_struct *tty)
632{
633	slcan_close(tty);
634	return 0;
635}
636
637/* Perform I/O control on an active SLCAN channel. */
638static int slcan_ioctl(struct tty_struct *tty, struct file *file,
639		       unsigned int cmd, unsigned long arg)
640{
641	struct slcan *sl = (struct slcan *) tty->disc_data;
642	unsigned int tmp;
643
644	/* First make sure we're connected. */
645	if (!sl || sl->magic != SLCAN_MAGIC)
646		return -EINVAL;
647
648	switch (cmd) {
649	case SIOCGIFNAME:
650		tmp = strlen(sl->dev->name) + 1;
651		if (copy_to_user((void __user *)arg, sl->dev->name, tmp))
652			return -EFAULT;
653		return 0;
654
655	case SIOCSIFHWADDR:
656		return -EINVAL;
657
658	default:
659		return tty_mode_ioctl(tty, file, cmd, arg);
660	}
661}
662
663static struct tty_ldisc_ops slc_ldisc = {
664	.owner		= THIS_MODULE,
665	.magic		= TTY_LDISC_MAGIC,
666	.name		= "slcan",
667	.open		= slcan_open,
668	.close		= slcan_close,
669	.hangup		= slcan_hangup,
670	.ioctl		= slcan_ioctl,
671	.receive_buf	= slcan_receive_buf,
672	.write_wakeup	= slcan_write_wakeup,
673};
674
675static int __init slcan_init(void)
676{
677	int status;
678
679	if (maxdev < 4)
680		maxdev = 4; /* Sanity */
681
682	printk(banner);
683	printk(KERN_INFO "slcan: %d dynamic interface channels.\n", maxdev);
684
685	slcan_devs = kzalloc(sizeof(struct net_device *)*maxdev, GFP_KERNEL);
686	if (!slcan_devs)
687		return -ENOMEM;
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