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/workqueue.h>
56#include <linux/can.h>
57#include <linux/can/skb.h>
58
59MODULE_ALIAS_LDISC(N_SLCAN);
60MODULE_DESCRIPTION("serial line CAN interface");
61MODULE_LICENSE("GPL");
62MODULE_AUTHOR("Oliver Hartkopp <socketcan@hartkopp.net>");
63
64#define SLCAN_MAGIC 0x53CA
65
66static int maxdev = 10;		/* MAX number of SLCAN channels;
67				   This can be overridden with
68				   insmod slcan.ko maxdev=nnn	*/
69module_param(maxdev, int, 0);
70MODULE_PARM_DESC(maxdev, "Maximum number of slcan interfaces");
71
72/* maximum rx buffer len: extended CAN frame with timestamp */
73#define SLC_MTU (sizeof("T1111222281122334455667788EA5F\r")+1)
74
75#define SLC_CMD_LEN 1
76#define SLC_SFF_ID_LEN 3
77#define SLC_EFF_ID_LEN 8
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	struct work_struct	tx_work;	/* Flushes transmit buffer   */
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
100static struct net_device **slcan_devs;
101
102 /************************************************************************
103  *			SLCAN ENCAPSULATION FORMAT			 *
104  ************************************************************************/
105
106/*
107 * A CAN frame has a can_id (11 bit standard frame format OR 29 bit extended
108 * frame format) a data length code (can_dlc) which can be from 0 to 8
109 * and up to <can_dlc> data bytes as payload.
110 * Additionally a CAN frame may become a remote transmission frame if the
111 * RTR-bit is set. This causes another ECU to send a CAN frame with the
112 * given can_id.
113 *
114 * The SLCAN ASCII representation of these different frame types is:
115 * <type> <id> <dlc> <data>*
116 *
117 * Extended frames (29 bit) are defined by capital characters in the type.
118 * RTR frames are defined as 'r' types - normal frames have 't' type:
119 * t => 11 bit data frame
120 * r => 11 bit RTR frame
121 * T => 29 bit data frame
122 * R => 29 bit RTR frame
123 *
124 * The <id> is 3 (standard) or 8 (extended) bytes in ASCII Hex (base64).
125 * The <dlc> is a one byte ASCII number ('0' - '8')
126 * The <data> section has at much ASCII Hex bytes as defined by the <dlc>
127 *
128 * Examples:
129 *
130 * t1230 : can_id 0x123, can_dlc 0, no data
131 * t4563112233 : can_id 0x456, can_dlc 3, data 0x11 0x22 0x33
132 * T12ABCDEF2AA55 : extended can_id 0x12ABCDEF, can_dlc 2, data 0xAA 0x55
133 * r1230 : can_id 0x123, can_dlc 0, no data, remote transmission request
134 *
135 */
136
137 /************************************************************************
138  *			STANDARD SLCAN DECAPSULATION			 *
139  ************************************************************************/
140
141/* Send one completely decapsulated can_frame to the network layer */
142static void slc_bump(struct slcan *sl)
143{
144	struct sk_buff *skb;
145	struct can_frame cf;
146	int i, tmp;
147	u32 tmpid;
148	char *cmd = sl->rbuff;
149
150	cf.can_id = 0;
151
152	switch (*cmd) {
153	case 'r':
154		cf.can_id = CAN_RTR_FLAG;
155		/* fallthrough */
156	case 't':
157		/* store dlc ASCII value and terminate SFF CAN ID string */
158		cf.can_dlc = sl->rbuff[SLC_CMD_LEN + SLC_SFF_ID_LEN];
159		sl->rbuff[SLC_CMD_LEN + SLC_SFF_ID_LEN] = 0;
160		/* point to payload data behind the dlc */
161		cmd += SLC_CMD_LEN + SLC_SFF_ID_LEN + 1;
162		break;
163	case 'R':
164		cf.can_id = CAN_RTR_FLAG;
165		/* fallthrough */
166	case 'T':
167		cf.can_id |= CAN_EFF_FLAG;
168		/* store dlc ASCII value and terminate EFF CAN ID string */
169		cf.can_dlc = sl->rbuff[SLC_CMD_LEN + SLC_EFF_ID_LEN];
170		sl->rbuff[SLC_CMD_LEN + SLC_EFF_ID_LEN] = 0;
171		/* point to payload data behind the dlc */
172		cmd += SLC_CMD_LEN + SLC_EFF_ID_LEN + 1;
173		break;
174	default:
175		return;
176	}
177
178	if (kstrtou32(sl->rbuff + SLC_CMD_LEN, 16, &tmpid))
179		return;
180
181	cf.can_id |= tmpid;
182
183	/* get can_dlc from sanitized ASCII value */
184	if (cf.can_dlc >= '0' && cf.can_dlc < '9')
185		cf.can_dlc -= '0';
186	else
187		return;
188
189	*(u64 *) (&cf.data) = 0; /* clear payload */
190
191	/* RTR frames may have a dlc > 0 but they never have any data bytes */
192	if (!(cf.can_id & CAN_RTR_FLAG)) {
193		for (i = 0; i < cf.can_dlc; i++) {
194			tmp = hex_to_bin(*cmd++);
195			if (tmp < 0)
196				return;
197			cf.data[i] = (tmp << 4);
198			tmp = hex_to_bin(*cmd++);
199			if (tmp < 0)
200				return;
201			cf.data[i] |= tmp;
202		}
203	}
204
205	skb = dev_alloc_skb(sizeof(struct can_frame) +
206			    sizeof(struct can_skb_priv));
207	if (!skb)
208		return;
209
210	skb->dev = sl->dev;
211	skb->protocol = htons(ETH_P_CAN);
212	skb->pkt_type = PACKET_BROADCAST;
213	skb->ip_summed = CHECKSUM_UNNECESSARY;
214
215	can_skb_reserve(skb);
216	can_skb_prv(skb)->ifindex = sl->dev->ifindex;
217	can_skb_prv(skb)->skbcnt = 0;
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/* Write out any remaining transmit buffer. Scheduled when tty is writable */
313static void slcan_transmit(struct work_struct *work)
314{
315	struct slcan *sl = container_of(work, struct slcan, tx_work);
316	int actual;
317
318	spin_lock_bh(&sl->lock);
319	/* First make sure we're connected. */
320	if (!sl->tty || sl->magic != SLCAN_MAGIC || !netif_running(sl->dev)) {
321		spin_unlock_bh(&sl->lock);
322		return;
323	}
324
325	if (sl->xleft <= 0)  {
326		/* Now serial buffer is almost free & we can start
327		 * transmission of another packet */
328		sl->dev->stats.tx_packets++;
329		clear_bit(TTY_DO_WRITE_WAKEUP, &sl->tty->flags);
330		spin_unlock_bh(&sl->lock);
331		netif_wake_queue(sl->dev);
332		return;
333	}
334
335	actual = sl->tty->ops->write(sl->tty, sl->xhead, sl->xleft);
336	sl->xleft -= actual;
337	sl->xhead += actual;
338	spin_unlock_bh(&sl->lock);
339}
340
341/*
342 * Called by the driver when there's room for more data.
343 * Schedule the transmit.
344 */
345static void slcan_write_wakeup(struct tty_struct *tty)
346{
347	struct slcan *sl = tty->disc_data;
348
349	schedule_work(&sl->tx_work);
350}
351
352/* Send a can_frame to a TTY queue. */
353static netdev_tx_t slc_xmit(struct sk_buff *skb, struct net_device *dev)
354{
355	struct slcan *sl = netdev_priv(dev);
356
357	if (skb->len != sizeof(struct can_frame))
358		goto out;
359
360	spin_lock(&sl->lock);
361	if (!netif_running(dev))  {
362		spin_unlock(&sl->lock);
363		printk(KERN_WARNING "%s: xmit: iface is down\n", dev->name);
364		goto out;
365	}
366	if (sl->tty == NULL) {
367		spin_unlock(&sl->lock);
368		goto out;
369	}
370
371	netif_stop_queue(sl->dev);
372	slc_encaps(sl, (struct can_frame *) skb->data); /* encaps & send */
373	spin_unlock(&sl->lock);
374
375out:
376	kfree_skb(skb);
377	return NETDEV_TX_OK;
378}
379
380
381/******************************************
382 *   Routines looking at netdevice side.
383 ******************************************/
384
385/* Netdevice UP -> DOWN routine */
386static int slc_close(struct net_device *dev)
387{
388	struct slcan *sl = netdev_priv(dev);
389
390	spin_lock_bh(&sl->lock);
391	if (sl->tty) {
392		/* TTY discipline is running. */
393		clear_bit(TTY_DO_WRITE_WAKEUP, &sl->tty->flags);
394	}
395	netif_stop_queue(dev);
396	sl->rcount   = 0;
397	sl->xleft    = 0;
398	spin_unlock_bh(&sl->lock);
399
400	return 0;
401}
402
403/* Netdevice DOWN -> UP routine */
404static int slc_open(struct net_device *dev)
405{
406	struct slcan *sl = netdev_priv(dev);
407
408	if (sl->tty == NULL)
409		return -ENODEV;
410
411	sl->flags &= (1 << SLF_INUSE);
412	netif_start_queue(dev);
413	return 0;
414}
415
416/* Hook the destructor so we can free slcan devs at the right point in time */
417static void slc_free_netdev(struct net_device *dev)
418{
419	int i = dev->base_addr;
420	free_netdev(dev);
421	slcan_devs[i] = NULL;
422}
423
424static int slcan_change_mtu(struct net_device *dev, int new_mtu)
425{
426	return -EINVAL;
427}
428
429static const struct net_device_ops slc_netdev_ops = {
430	.ndo_open               = slc_open,
431	.ndo_stop               = slc_close,
432	.ndo_start_xmit         = slc_xmit,
433	.ndo_change_mtu         = slcan_change_mtu,
434};
435
436static void slc_setup(struct net_device *dev)
437{
438	dev->netdev_ops		= &slc_netdev_ops;
439	dev->destructor		= slc_free_netdev;
440
441	dev->hard_header_len	= 0;
442	dev->addr_len		= 0;
443	dev->tx_queue_len	= 10;
444
445	dev->mtu		= sizeof(struct can_frame);
446	dev->type		= ARPHRD_CAN;
447
448	/* New-style flags. */
449	dev->flags		= IFF_NOARP;
450	dev->features           = NETIF_F_HW_CSUM;
451}
452
453/******************************************
454  Routines looking at TTY side.
455 ******************************************/
456
457/*
458 * Handle the 'receiver data ready' interrupt.
459 * This function is called by the 'tty_io' module in the kernel when
460 * a block of SLCAN data has been received, which can now be decapsulated
461 * and sent on to some IP layer for further processing. This will not
462 * be re-entered while running but other ldisc functions may be called
463 * in parallel
464 */
465
466static void slcan_receive_buf(struct tty_struct *tty,
467			      const unsigned char *cp, char *fp, int count)
468{
469	struct slcan *sl = (struct slcan *) tty->disc_data;
470
471	if (!sl || sl->magic != SLCAN_MAGIC || !netif_running(sl->dev))
472		return;
473
474	/* Read the characters out of the buffer */
475	while (count--) {
476		if (fp && *fp++) {
477			if (!test_and_set_bit(SLF_ERROR, &sl->flags))
478				sl->dev->stats.rx_errors++;
479			cp++;
480			continue;
481		}
482		slcan_unesc(sl, *cp++);
483	}
484}
485
486/************************************
487 *  slcan_open helper routines.
488 ************************************/
489
490/* Collect hanged up channels */
491static void slc_sync(void)
492{
493	int i;
494	struct net_device *dev;
495	struct slcan	  *sl;
496
497	for (i = 0; i < maxdev; i++) {
498		dev = slcan_devs[i];
499		if (dev == NULL)
500			break;
501
502		sl = netdev_priv(dev);
503		if (sl->tty)
504			continue;
505		if (dev->flags & IFF_UP)
506			dev_close(dev);
507	}
508}
509
510/* Find a free SLCAN channel, and link in this `tty' line. */
511static struct slcan *slc_alloc(dev_t line)
512{
513	int i;
514	char name[IFNAMSIZ];
515	struct net_device *dev = NULL;
516	struct slcan       *sl;
517
518	for (i = 0; i < maxdev; i++) {
519		dev = slcan_devs[i];
520		if (dev == NULL)
521			break;
522
523	}
524
525	/* Sorry, too many, all slots in use */
526	if (i >= maxdev)
527		return NULL;
528
529	sprintf(name, "slcan%d", i);
530	dev = alloc_netdev(sizeof(*sl), name, NET_NAME_UNKNOWN, slc_setup);
531	if (!dev)
532		return NULL;
533
534	dev->base_addr  = i;
535	sl = netdev_priv(dev);
536
537	/* Initialize channel control data */
538	sl->magic = SLCAN_MAGIC;
539	sl->dev	= dev;
540	spin_lock_init(&sl->lock);
541	INIT_WORK(&sl->tx_work, slcan_transmit);
542	slcan_devs[i] = dev;
543
544	return sl;
545}
546
547/*
548 * Open the high-level part of the SLCAN channel.
549 * This function is called by the TTY module when the
550 * SLCAN line discipline is called for.  Because we are
551 * sure the tty line exists, we only have to link it to
552 * a free SLCAN channel...
553 *
554 * Called in process context serialized from other ldisc calls.
555 */
556
557static int slcan_open(struct tty_struct *tty)
558{
559	struct slcan *sl;
560	int err;
561
562	if (!capable(CAP_NET_ADMIN))
563		return -EPERM;
564
565	if (tty->ops->write == NULL)
566		return -EOPNOTSUPP;
567
568	/* RTnetlink lock is misused here to serialize concurrent
569	   opens of slcan channels. There are better ways, but it is
570	   the simplest one.
571	 */
572	rtnl_lock();
573
574	/* Collect hanged up channels. */
575	slc_sync();
576
577	sl = tty->disc_data;
578
579	err = -EEXIST;
580	/* First make sure we're not already connected. */
581	if (sl && sl->magic == SLCAN_MAGIC)
582		goto err_exit;
583
584	/* OK.  Find a free SLCAN channel to use. */
585	err = -ENFILE;
586	sl = slc_alloc(tty_devnum(tty));
587	if (sl == NULL)
588		goto err_exit;
589
590	sl->tty = tty;
591	tty->disc_data = sl;
592
593	if (!test_bit(SLF_INUSE, &sl->flags)) {
594		/* Perform the low-level SLCAN initialization. */
595		sl->rcount   = 0;
596		sl->xleft    = 0;
597
598		set_bit(SLF_INUSE, &sl->flags);
599
600		err = register_netdevice(sl->dev);
601		if (err)
602			goto err_free_chan;
603	}
604
605	/* Done.  We have linked the TTY line to a channel. */
606	rtnl_unlock();
607	tty->receive_room = 65536;	/* We don't flow control */
608
609	/* TTY layer expects 0 on success */
610	return 0;
611
612err_free_chan:
613	sl->tty = NULL;
614	tty->disc_data = NULL;
615	clear_bit(SLF_INUSE, &sl->flags);
616
617err_exit:
618	rtnl_unlock();
619
620	/* Count references from TTY module */
621	return err;
622}
623
624/*
625 * Close down a SLCAN channel.
626 * This means flushing out any pending queues, and then returning. This
627 * call is serialized against other ldisc functions.
628 *
629 * We also use this method for a hangup event.
630 */
631
632static void slcan_close(struct tty_struct *tty)
633{
634	struct slcan *sl = (struct slcan *) tty->disc_data;
635
636	/* First make sure we're connected. */
637	if (!sl || sl->magic != SLCAN_MAGIC || sl->tty != tty)
638		return;
639
640	spin_lock_bh(&sl->lock);
641	tty->disc_data = NULL;
642	sl->tty = NULL;
643	spin_unlock_bh(&sl->lock);
644
645	flush_work(&sl->tx_work);
646
647	/* Flush network side */
648	unregister_netdev(sl->dev);
649	/* This will complete via sl_free_netdev */
650}
651
652static int slcan_hangup(struct tty_struct *tty)
653{
654	slcan_close(tty);
655	return 0;
656}
657
658/* Perform I/O control on an active SLCAN channel. */
659static int slcan_ioctl(struct tty_struct *tty, struct file *file,
660		       unsigned int cmd, unsigned long arg)
661{
662	struct slcan *sl = (struct slcan *) tty->disc_data;
663	unsigned int tmp;
664
665	/* First make sure we're connected. */
666	if (!sl || sl->magic != SLCAN_MAGIC)
667		return -EINVAL;
668
669	switch (cmd) {
670	case SIOCGIFNAME:
671		tmp = strlen(sl->dev->name) + 1;
672		if (copy_to_user((void __user *)arg, sl->dev->name, tmp))
673			return -EFAULT;
674		return 0;
675
676	case SIOCSIFHWADDR:
677		return -EINVAL;
678
679	default:
680		return tty_mode_ioctl(tty, file, cmd, arg);
681	}
682}
683
684static struct tty_ldisc_ops slc_ldisc = {
685	.owner		= THIS_MODULE,
686	.magic		= TTY_LDISC_MAGIC,
687	.name		= "slcan",
688	.open		= slcan_open,
689	.close		= slcan_close,
690	.hangup		= slcan_hangup,
691	.ioctl		= slcan_ioctl,
692	.receive_buf	= slcan_receive_buf,
693	.write_wakeup	= slcan_write_wakeup,
694};
695
696static int __init slcan_init(void)
697{
698	int status;
699
700	if (maxdev < 4)
701		maxdev = 4; /* Sanity */
702
703	pr_info("slcan: serial line CAN interface driver\n");
704	pr_info("slcan: %d dynamic interface channels.\n", maxdev);
705
706	slcan_devs = kzalloc(sizeof(struct net_device *)*maxdev, GFP_KERNEL);
707	if (!slcan_devs)
708		return -ENOMEM;
709
710	/* Fill in our line protocol discipline, and register it */
711	status = tty_register_ldisc(N_SLCAN, &slc_ldisc);
712	if (status)  {
713		printk(KERN_ERR "slcan: can't register line discipline\n");
714		kfree(slcan_devs);
715	}
716	return status;
717}
718
719static void __exit slcan_exit(void)
720{
721	int i;
722	struct net_device *dev;
723	struct slcan *sl;
724	unsigned long timeout = jiffies + HZ;
725	int busy = 0;
726
727	if (slcan_devs == NULL)
728		return;
729
730	/* First of all: check for active disciplines and hangup them.
731	 */
732	do {
733		if (busy)
734			msleep_interruptible(100);
735
736		busy = 0;
737		for (i = 0; i < maxdev; i++) {
738			dev = slcan_devs[i];
739			if (!dev)
740				continue;
741			sl = netdev_priv(dev);
742			spin_lock_bh(&sl->lock);
743			if (sl->tty) {
744				busy++;
745				tty_hangup(sl->tty);
746			}
747			spin_unlock_bh(&sl->lock);
748		}
749	} while (busy && time_before(jiffies, timeout));
750
751	/* FIXME: hangup is async so we should wait when doing this second
752	   phase */
753
754	for (i = 0; i < maxdev; i++) {
755		dev = slcan_devs[i];
756		if (!dev)
757			continue;
758		slcan_devs[i] = NULL;
759
760		sl = netdev_priv(dev);
761		if (sl->tty) {
762			printk(KERN_ERR "%s: tty discipline still running\n",
763			       dev->name);
764			/* Intentionally leak the control block. */
765			dev->destructor = NULL;
766		}
767
768		unregister_netdev(dev);
769	}
770
771	kfree(slcan_devs);
772	slcan_devs = NULL;
773
774	i = tty_unregister_ldisc(N_SLCAN);
775	if (i)
776		printk(KERN_ERR "slcan: can't unregister ldisc (err %d)\n", i);
777}
778
779module_init(slcan_init);
780module_exit(slcan_exit);
781