aboutsummaryrefslogtreecommitdiff
path: root/drivers/net/can/slcan.c
blob: 25377e547f9b01f49167caa13f510c51fb2bd1c7 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
/*
 * slcan.c - serial line CAN interface driver (using tty line discipline)
 *
 * This file is derived from linux/drivers/net/slip/slip.c
 *
 * slip.c Authors  : Laurence Culhane <loz@holmes.demon.co.uk>
 *                   Fred N. van Kempen <waltje@uwalt.nl.mugnet.org>
 * slcan.c Author  : Oliver Hartkopp <socketcan@hartkopp.net>
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the
 * Free Software Foundation; either version 2 of the License, or (at your
 * option) any later version.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 59 Temple Place, Suite 330, Boston, MA 02111-1307. You can also get it
 * at http://www.gnu.org/licenses/gpl.html
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
 * DAMAGE.
 *
 */

#include <linux/module.h>
#include <linux/moduleparam.h>

#include <linux/uaccess.h>
#include <linux/bitops.h>
#include <linux/string.h>
#include <linux/tty.h>
#include <linux/errno.h>
#include <linux/netdevice.h>
#include <linux/skbuff.h>
#include <linux/rtnetlink.h>
#include <linux/if_arp.h>
#include <linux/if_ether.h>
#include <linux/sched.h>
#include <linux/delay.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/can.h>
#include <linux/can/skb.h>

static __initconst const char banner[] =
	KERN_INFO "slcan: serial line CAN interface driver\n";

MODULE_ALIAS_LDISC(N_SLCAN);
MODULE_DESCRIPTION("serial line CAN interface");
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Oliver Hartkopp <socketcan@hartkopp.net>");

#define SLCAN_MAGIC 0x53CA

static int maxdev = 10;		/* MAX number of SLCAN channels;
				   This can be overridden with
				   insmod slcan.ko maxdev=nnn	*/
module_param(maxdev, int, 0);
MODULE_PARM_DESC(maxdev, "Maximum number of slcan interfaces");

/* maximum rx buffer len: extended CAN frame with timestamp */
#define SLC_MTU (sizeof("T1111222281122334455667788EA5F\r")+1)

#define SLC_CMD_LEN 1
#define SLC_SFF_ID_LEN 3
#define SLC_EFF_ID_LEN 8

struct slcan {
	int			magic;

	/* Various fields. */
	struct tty_struct	*tty;		/* ptr to TTY structure	     */
	struct net_device	*dev;		/* easy for intr handling    */
	spinlock_t		lock;

	/* These are pointers to the malloc()ed frame buffers. */
	unsigned char		rbuff[SLC_MTU];	/* receiver buffer	     */
	int			rcount;         /* received chars counter    */
	unsigned char		xbuff[SLC_MTU];	/* transmitter buffer	     */
	unsigned char		*xhead;         /* pointer to next XMIT byte */
	int			xleft;          /* bytes left in XMIT queue  */

	unsigned long		flags;		/* Flag values/ mode etc     */
#define SLF_INUSE		0		/* Channel in use            */
#define SLF_ERROR		1               /* Parity, etc. error        */
};

static struct net_device **slcan_devs;

 /************************************************************************
  *			SLCAN ENCAPSULATION FORMAT			 *
  ************************************************************************/

/*
 * A CAN frame has a can_id (11 bit standard frame format OR 29 bit extended
 * frame format) a data length code (can_dlc) which can be from 0 to 8
 * and up to <can_dlc> data bytes as payload.
 * Additionally a CAN frame may become a remote transmission frame if the
 * RTR-bit is set. This causes another ECU to send a CAN frame with the
 * given can_id.
 *
 * The SLCAN ASCII representation of these different frame types is:
 * <type> <id> <dlc> <data>*
 *
 * Extended frames (29 bit) are defined by capital characters in the type.
 * RTR frames are defined as 'r' types - normal frames have 't' type:
 * t => 11 bit data frame
 * r => 11 bit RTR frame
 * T => 29 bit data frame
 * R => 29 bit RTR frame
 *
 * The <id> is 3 (standard) or 8 (extended) bytes in ASCII Hex (base64).
 * The <dlc> is a one byte ASCII number ('0' - '8')
 * The <data> section has at much ASCII Hex bytes as defined by the <dlc>
 *
 * Examples:
 *
 * t1230 : can_id 0x123, can_dlc 0, no data
 * t4563112233 : can_id 0x456, can_dlc 3, data 0x11 0x22 0x33
 * T12ABCDEF2AA55 : extended can_id 0x12ABCDEF, can_dlc 2, data 0xAA 0x55
 * r1230 : can_id 0x123, can_dlc 0, no data, remote transmission request
 *
 */

 /************************************************************************
  *			STANDARD SLCAN DECAPSULATION			 *
  ************************************************************************/

/* Send one completely decapsulated can_frame to the network layer */
static void slc_bump(struct slcan *sl)
{
	struct sk_buff *skb;
	struct can_frame cf;
	int i, tmp;
	u32 tmpid;
	char *cmd = sl->rbuff;

	cf.can_id = 0;

	switch (*cmd) {
	case 'r':
		cf.can_id = CAN_RTR_FLAG;
		/* fallthrough */
	case 't':
		/* store dlc ASCII value and terminate SFF CAN ID string */
		cf.can_dlc = sl->rbuff[SLC_CMD_LEN + SLC_SFF_ID_LEN];
		sl->rbuff[SLC_CMD_LEN + SLC_SFF_ID_LEN] = 0;
		/* point to payload data behind the dlc */
		cmd += SLC_CMD_LEN + SLC_SFF_ID_LEN + 1;
		break;
	case 'R':
		cf.can_id = CAN_RTR_FLAG;
		/* fallthrough */
	case 'T':
		cf.can_id |= CAN_EFF_FLAG;
		/* store dlc ASCII value and terminate EFF CAN ID string */
		cf.can_dlc = sl->rbuff[SLC_CMD_LEN + SLC_EFF_ID_LEN];
		sl->rbuff[SLC_CMD_LEN + SLC_EFF_ID_LEN] = 0;
		/* point to payload data behind the dlc */
		cmd += SLC_CMD_LEN + SLC_EFF_ID_LEN + 1;
		break;
	default:
		return;
	}

	if (kstrtou32(sl->rbuff + SLC_CMD_LEN, 16, &tmpid))
		return;

	cf.can_id |= tmpid;

	/* get can_dlc from sanitized ASCII value */
	if (cf.can_dlc >= '0' && cf.can_dlc < '9')
		cf.can_dlc -= '0';
	else
		return;

	*(u64 *) (&cf.data) = 0; /* clear payload */

	/* RTR frames may have a dlc > 0 but they never have any data bytes */
	if (!(cf.can_id & CAN_RTR_FLAG)) {
		for (i = 0; i < cf.can_dlc; i++) {
			tmp = hex_to_bin(*cmd++);
			if (tmp < 0)
				return;
			cf.data[i] = (tmp << 4);
			tmp = hex_to_bin(*cmd++);
			if (tmp < 0)
				return;
			cf.data[i] |= tmp;
		}
	}

	skb = dev_alloc_skb(sizeof(struct can_frame) +
			    sizeof(struct can_skb_priv));
	if (!skb)
		return;

	skb->dev = sl->dev;
	skb->protocol = htons(ETH_P_CAN);
	skb->pkt_type = PACKET_BROADCAST;
	skb->ip_summed = CHECKSUM_UNNECESSARY;

	can_skb_reserve(skb);
	can_skb_prv(skb)->ifindex = sl->dev->ifindex;

	memcpy(skb_put(skb, sizeof(struct can_frame)),
	       &cf, sizeof(struct can_frame));
	netif_rx_ni(skb);

	sl->dev->stats.rx_packets++;
	sl->dev->stats.rx_bytes += cf.can_dlc;
}

/* parse tty input stream */
static void slcan_unesc(struct slcan *sl, unsigned char s)
{
	if ((s == '\r') || (s == '\a')) { /* CR or BEL ends the pdu */
		if (!test_and_clear_bit(SLF_ERROR, &sl->flags) &&
		    (sl->rcount > 4))  {
			slc_bump(sl);
		}
		sl->rcount = 0;
	} else {
		if (!test_bit(SLF_ERROR, &sl->flags))  {
			if (sl->rcount < SLC_MTU)  {
				sl->rbuff[sl->rcount++] = s;
				return;
			} else {
				sl->dev->stats.rx_over_errors++;
				set_bit(SLF_ERROR, &sl->flags);
			}
		}
	}
}

 /************************************************************************
  *			STANDARD SLCAN ENCAPSULATION			 *
  ************************************************************************/

/* Encapsulate one can_frame and stuff into a TTY queue. */
static void slc_encaps(struct slcan *sl, struct can_frame *cf)
{
	int actual, i;
	unsigned char *pos;
	unsigned char *endpos;
	canid_t id = cf->can_id;

	pos = sl->xbuff;

	if (cf->can_id & CAN_RTR_FLAG)
		*pos = 'R'; /* becomes 'r' in standard frame format (SFF) */
	else
		*pos = 'T'; /* becomes 't' in standard frame format (SSF) */

	/* determine number of chars for the CAN-identifier */
	if (cf->can_id & CAN_EFF_FLAG) {
		id &= CAN_EFF_MASK;
		endpos = pos + SLC_EFF_ID_LEN;
	} else {
		*pos |= 0x20; /* convert R/T to lower case for SFF */
		id &= CAN_SFF_MASK;
		endpos = pos + SLC_SFF_ID_LEN;
	}

	/* build 3 (SFF) or 8 (EFF) digit CAN identifier */
	pos++;
	while (endpos >= pos) {
		*endpos-- = hex_asc_upper[id & 0xf];
		id >>= 4;
	}

	pos += (cf->can_id & CAN_EFF_FLAG) ? SLC_EFF_ID_LEN : SLC_SFF_ID_LEN;

	*pos++ = cf->can_dlc + '0';

	/* RTR frames may have a dlc > 0 but they never have any data bytes */
	if (!(cf->can_id & CAN_RTR_FLAG)) {
		for (i = 0; i < cf->can_dlc; i++)
			pos = hex_byte_pack_upper(pos, cf->data[i]);
	}

	*pos++ = '\r';

	/* Order of next two lines is *very* important.
	 * When we are sending a little amount of data,
	 * the transfer may be completed inside the ops->write()
	 * routine, because it's running with interrupts enabled.
	 * In this case we *never* got WRITE_WAKEUP event,
	 * if we did not request it before write operation.
	 *       14 Oct 1994  Dmitry Gorodchanin.
	 */
	set_bit(TTY_DO_WRITE_WAKEUP, &sl->tty->flags);
	actual = sl->tty->ops->write(sl->tty, sl->xbuff, pos - sl->xbuff);
	sl->xleft = (pos - sl->xbuff) - actual;
	sl->xhead = sl->xbuff + actual;
	sl->dev->stats.tx_bytes += cf->can_dlc;
}

/*
 * Called by the driver when there's room for more data.  If we have
 * more packets to send, we send them here.
 */
static void slcan_write_wakeup(struct tty_struct *tty)
{
	int actual;
	struct slcan *sl = (struct slcan *) tty->disc_data;

	/* First make sure we're connected. */
	if (!sl || sl->magic != SLCAN_MAGIC || !netif_running(sl->dev))
		return;

	spin_lock(&sl->lock);
	if (sl->xleft <= 0)  {
		/* Now serial buffer is almost free & we can start
		 * transmission of another packet */
		sl->dev->stats.tx_packets++;
		clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
		spin_unlock(&sl->lock);
		netif_wake_queue(sl->dev);
		return;
	}

	actual = tty->ops->write(tty, sl->xhead, sl->xleft);
	sl->xleft -= actual;
	sl->xhead += actual;
	spin_unlock(&sl->lock);
}

/* Send a can_frame to a TTY queue. */
static netdev_tx_t slc_xmit(struct sk_buff *skb, struct net_device *dev)
{
	struct slcan *sl = netdev_priv(dev);

	if (skb->len != sizeof(struct can_frame))
		goto out;

	spin_lock(&sl->lock);
	if (!netif_running(dev))  {
		spin_unlock(&sl->lock);
		printk(KERN_WARNING "%s: xmit: iface is down\n", dev->name);
		goto out;
	}
	if (sl->tty == NULL) {
		spin_unlock(&sl->lock);
		goto out;
	}

	netif_stop_queue(sl->dev);
	slc_encaps(sl, (struct can_frame *) skb->data); /* encaps & send */
	spin_unlock(&sl->lock);

out:
	kfree_skb(skb);
	return NETDEV_TX_OK;
}


/******************************************
 *   Routines looking at netdevice side.
 ******************************************/

/* Netdevice UP -> DOWN routine */
static int slc_close(struct net_device *dev)
{
	struct slcan *sl = netdev_priv(dev);

	spin_lock_bh(&sl->lock);
	if (sl->tty) {
		/* TTY discipline is running. */
		clear_bit(TTY_DO_WRITE_WAKEUP, &sl->tty->flags);
	}
	netif_stop_queue(dev);
	sl->rcount   = 0;
	sl->xleft    = 0;
	spin_unlock_bh(&sl->lock);

	return 0;
}

/* Netdevice DOWN -> UP routine */
static int slc_open(struct net_device *dev)
{
	struct slcan *sl = netdev_priv(dev);

	if (sl->tty == NULL)
		return -ENODEV;

	sl->flags &= (1 << SLF_INUSE);
	netif_start_queue(dev);
	return 0;
}

/* Hook the destructor so we can free slcan devs at the right point in time */
static void slc_free_netdev(struct net_device *dev)
{
	int i = dev->base_addr;
	free_netdev(dev);
	slcan_devs[i] = NULL;
}

static const struct net_device_ops slc_netdev_ops = {
	.ndo_open               = slc_open,
	.ndo_stop               = slc_close,
	.ndo_start_xmit         = slc_xmit,
};

static void slc_setup(struct net_device *dev)
{
	dev->netdev_ops		= &slc_netdev_ops;
	dev->destructor		= slc_free_netdev;

	dev->hard_header_len	= 0;
	dev->addr_len		= 0;
	dev->tx_queue_len	= 10;

	dev->mtu		= sizeof(struct can_frame);
	dev->type		= ARPHRD_CAN;

	/* New-style flags. */
	dev->flags		= IFF_NOARP;
	dev->features           = NETIF_F_HW_CSUM;
}

/******************************************
  Routines looking at TTY side.
 ******************************************/

/*
 * Handle the 'receiver data ready' interrupt.
 * This function is called by the 'tty_io' module in the kernel when
 * a block of SLCAN data has been received, which can now be decapsulated
 * and sent on to some IP layer for further processing. This will not
 * be re-entered while running but other ldisc functions may be called
 * in parallel
 */

static void slcan_receive_buf(struct tty_struct *tty,
			      const unsigned char *cp, char *fp, int count)
{
	struct slcan *sl = (struct slcan *) tty->disc_data;

	if (!sl || sl->magic != SLCAN_MAGIC || !netif_running(sl->dev))
		return;

	/* Read the characters out of the buffer */
	while (count--) {
		if (fp && *fp++) {
			if (!test_and_set_bit(SLF_ERROR, &sl->flags))
				sl->dev->stats.rx_errors++;
			cp++;
			continue;
		}
		slcan_unesc(sl, *cp++);
	}
}

/************************************
 *  slcan_open helper routines.
 ************************************/

/* Collect hanged up channels */
static void slc_sync(void)
{
	int i;
	struct net_device *dev;
	struct slcan	  *sl;

	for (i = 0; i < maxdev; i++) {
		dev = slcan_devs[i];
		if (dev == NULL)
			break;

		sl = netdev_priv(dev);
		if (sl->tty)
			continue;
		if (dev->flags & IFF_UP)
			dev_close(dev);
	}
}

/* Find a free SLCAN channel, and link in this `tty' line. */
static struct slcan *slc_alloc(dev_t line)
{
	int i;
	char name[IFNAMSIZ];
	struct net_device *dev = NULL;
	struct slcan       *sl;

	for (i = 0; i < maxdev; i++) {
		dev = slcan_devs[i];
		if (dev == NULL)
			break;

	}

	/* Sorry, too many, all slots in use */
	if (i >= maxdev)
		return NULL;

	sprintf(name, "slcan%d", i);
	dev = alloc_netdev(sizeof(*sl), name, slc_setup);
	if (!dev)
		return NULL;

	dev->base_addr  = i;
	sl = netdev_priv(dev);

	/* Initialize channel control data */
	sl->magic = SLCAN_MAGIC;
	sl->dev	= dev;
	spin_lock_init(&sl->lock);
	slcan_devs[i] = dev;

	return sl;
}

/*
 * Open the high-level part of the SLCAN channel.
 * This function is called by the TTY module when the
 * SLCAN line discipline is called for.  Because we are
 * sure the tty line exists, we only have to link it to
 * a free SLCAN channel...
 *
 * Called in process context serialized from other ldisc calls.
 */

static int slcan_open(struct tty_struct *tty)
{
	struct slcan *sl;
	int err;

	if (!capable(CAP_NET_ADMIN))
		return -EPERM;

	if (tty->ops->write == NULL)
		return -EOPNOTSUPP;

	/* RTnetlink lock is misused here to serialize concurrent
	   opens of slcan channels. There are better ways, but it is
	   the simplest one.
	 */
	rtnl_lock();

	/* Collect hanged up channels. */
	slc_sync();

	sl = tty->disc_data;

	err = -EEXIST;
	/* First make sure we're not already connected. */
	if (sl && sl->magic == SLCAN_MAGIC)
		goto err_exit;

	/* OK.  Find a free SLCAN channel to use. */
	err = -ENFILE;
	sl = slc_alloc(tty_devnum(tty));
	if (sl == NULL)
		goto err_exit;

	sl->tty = tty;
	tty->disc_data = sl;

	if (!test_bit(SLF_INUSE, &sl->flags)) {
		/* Perform the low-level SLCAN initialization. */
		sl->rcount   = 0;
		sl->xleft    = 0;

		set_bit(SLF_INUSE, &sl->flags);

		err = register_netdevice(sl->dev);
		if (err)
			goto err_free_chan;
	}

	/* Done.  We have linked the TTY line to a channel. */
	rtnl_unlock();
	tty->receive_room = 65536;	/* We don't flow control */

	/* TTY layer expects 0 on success */
	return 0;

err_free_chan:
	sl->tty = NULL;
	tty->disc_data = NULL;
	clear_bit(SLF_INUSE, &sl->flags);

err_exit:
	rtnl_unlock();

	/* Count references from TTY module */
	return err;
}

/*
 * Close down a SLCAN channel.
 * This means flushing out any pending queues, and then returning. This
 * call is serialized against other ldisc functions.
 *
 * We also use this method for a hangup event.
 */

static void slcan_close(struct tty_struct *tty)
{
	struct slcan *sl = (struct slcan *) tty->disc_data;

	/* First make sure we're connected. */
	if (!sl || sl->magic != SLCAN_MAGIC || sl->tty != tty)
		return;

	tty->disc_data = NULL;
	sl->tty = NULL;

	/* Flush network side */
	unregister_netdev(sl->dev);
	/* This will complete via sl_free_netdev */
}

static int slcan_hangup(struct tty_struct *tty)
{
	slcan_close(tty);
	return 0;
}

/* Perform I/O control on an active SLCAN channel. */
static int slcan_ioctl(struct tty_struct *tty, struct file *file,
		       unsigned int cmd, unsigned long arg)
{
	struct slcan *sl = (struct slcan *) tty->disc_data;
	unsigned int tmp;

	/* First make sure we're connected. */
	if (!sl || sl->magic != SLCAN_MAGIC)
		return -EINVAL;

	switch (cmd) {
	case SIOCGIFNAME:
		tmp = strlen(sl->dev->name) + 1;
		if (copy_to_user((void __user *)arg, sl->dev->name, tmp))
			return -EFAULT;
		return 0;

	case SIOCSIFHWADDR:
		return -EINVAL;

	default:
		return tty_mode_ioctl(tty, file, cmd, arg);
	}
}

static struct tty_ldisc_ops slc_ldisc = {
	.owner		= THIS_MODULE,
	.magic		= TTY_LDISC_MAGIC,
	.name		= "slcan",
	.open		= slcan_open,
	.close		= slcan_close,
	.hangup		= slcan_hangup,
	.ioctl		= slcan_ioctl,
	.receive_buf	= slcan_receive_buf,
	.write_wakeup	= slcan_write_wakeup,
};

static int __init slcan_init(void)
{
	int status;

	if (maxdev < 4)
		maxdev = 4; /* Sanity */

	printk(banner);
	printk(KERN_INFO "slcan: %d dynamic interface channels.\n", maxdev);

	slcan_devs = kzalloc(sizeof(struct net_device *)*maxdev, GFP_KERNEL);
	if (!slcan_devs)
		return -ENOMEM;

	/* Fill in our line protocol discipline, and register it */
	status = tty_register_ldisc(N_SLCAN, &slc_ldisc);
	if (status)  {
		printk(KERN_ERR "slcan: can't register line discipline\n");
		kfree(slcan_devs);
	}
	return status;
}

static void __exit slcan_exit(void)
{
	int i;
	struct net_device *dev;
	struct slcan *sl;
	unsigned long timeout = jiffies + HZ;
	int busy = 0;

	if (slcan_devs == NULL)
		return;

	/* First of all: check for active disciplines and hangup them.
	 */
	do {
		if (busy)
			msleep_interruptible(100);

		busy = 0;
		for (i = 0; i < maxdev; i++) {
			dev = slcan_devs[i];
			if (!dev)
				continue;
			sl = netdev_priv(dev);
			spin_lock_bh(&sl->lock);
			if (sl->tty) {
				busy++;
				tty_hangup(sl->tty);
			}
			spin_unlock_bh(&sl->lock);
		}
	} while (busy && time_before(jiffies, timeout));

	/* FIXME: hangup is async so we should wait when doing this second
	   phase */

	for (i = 0; i < maxdev; i++) {
		dev = slcan_devs[i];
		if (!dev)
			continue;
		slcan_devs[i] = NULL;

		sl = netdev_priv(dev);
		if (sl->tty) {
			printk(KERN_ERR "%s: tty discipline still running\n",
			       dev->name);
			/* Intentionally leak the control block. */
			dev->destructor = NULL;
		}

		unregister_netdev(dev);
	}

	kfree(slcan_devs);
	slcan_devs = NULL;

	i = tty_unregister_ldisc(N_SLCAN);
	if (i)
		printk(KERN_ERR "slcan: can't unregister ldisc (err %d)\n", i);
}

module_init(slcan_init);
module_exit(slcan_exit);