xref: /openbmc/linux/drivers/net/hamradio/6pack.c (revision 236bdb88)
1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * 6pack.c	This module implements the 6pack protocol for kernel-based
4  *		devices like TTY. It interfaces between a raw TTY and the
5  *		kernel's AX.25 protocol layers.
6  *
7  * Authors:	Andreas Könsgen <ajk@comnets.uni-bremen.de>
8  *              Ralf Baechle DL5RB <ralf@linux-mips.org>
9  *
10  * Quite a lot of stuff "stolen" by Joerg Reuter from slip.c, written by
11  *
12  *		Laurence Culhane, <loz@holmes.demon.co.uk>
13  *		Fred N. van Kempen, <waltje@uwalt.nl.mugnet.org>
14  */
15 
16 #include <linux/module.h>
17 #include <linux/uaccess.h>
18 #include <linux/bitops.h>
19 #include <linux/string.h>
20 #include <linux/mm.h>
21 #include <linux/interrupt.h>
22 #include <linux/in.h>
23 #include <linux/tty.h>
24 #include <linux/errno.h>
25 #include <linux/netdevice.h>
26 #include <linux/timer.h>
27 #include <linux/slab.h>
28 #include <net/ax25.h>
29 #include <linux/etherdevice.h>
30 #include <linux/skbuff.h>
31 #include <linux/rtnetlink.h>
32 #include <linux/spinlock.h>
33 #include <linux/if_arp.h>
34 #include <linux/init.h>
35 #include <linux/ip.h>
36 #include <linux/tcp.h>
37 #include <linux/semaphore.h>
38 #include <linux/refcount.h>
39 
40 #define SIXPACK_VERSION    "Revision: 0.3.0"
41 
42 /* sixpack priority commands */
43 #define SIXP_SEOF		0x40	/* start and end of a 6pack frame */
44 #define SIXP_TX_URUN		0x48	/* transmit overrun */
45 #define SIXP_RX_ORUN		0x50	/* receive overrun */
46 #define SIXP_RX_BUF_OVL		0x58	/* receive buffer overflow */
47 
48 #define SIXP_CHKSUM		0xFF	/* valid checksum of a 6pack frame */
49 
50 /* masks to get certain bits out of the status bytes sent by the TNC */
51 
52 #define SIXP_CMD_MASK		0xC0
53 #define SIXP_CHN_MASK		0x07
54 #define SIXP_PRIO_CMD_MASK	0x80
55 #define SIXP_STD_CMD_MASK	0x40
56 #define SIXP_PRIO_DATA_MASK	0x38
57 #define SIXP_TX_MASK		0x20
58 #define SIXP_RX_MASK		0x10
59 #define SIXP_RX_DCD_MASK	0x18
60 #define SIXP_LEDS_ON		0x78
61 #define SIXP_LEDS_OFF		0x60
62 #define SIXP_CON		0x08
63 #define SIXP_STA		0x10
64 
65 #define SIXP_FOUND_TNC		0xe9
66 #define SIXP_CON_ON		0x68
67 #define SIXP_DCD_MASK		0x08
68 #define SIXP_DAMA_OFF		0
69 
70 /* default level 2 parameters */
71 #define SIXP_TXDELAY			25	/* 250 ms */
72 #define SIXP_PERSIST			50	/* in 256ths */
73 #define SIXP_SLOTTIME			10	/* 100 ms */
74 #define SIXP_INIT_RESYNC_TIMEOUT	(3*HZ/2) /* in 1 s */
75 #define SIXP_RESYNC_TIMEOUT		5*HZ	/* in 1 s */
76 
77 /* 6pack configuration. */
78 #define SIXP_NRUNIT			31      /* MAX number of 6pack channels */
79 #define SIXP_MTU			256	/* Default MTU */
80 
81 enum sixpack_flags {
82 	SIXPF_ERROR,	/* Parity, etc. error	*/
83 };
84 
85 struct sixpack {
86 	/* Various fields. */
87 	struct tty_struct	*tty;		/* ptr to TTY structure	*/
88 	struct net_device	*dev;		/* easy for intr handling  */
89 
90 	/* These are pointers to the malloc()ed frame buffers. */
91 	unsigned char		*rbuff;		/* receiver buffer	*/
92 	int			rcount;         /* received chars counter  */
93 	unsigned char		*xbuff;		/* transmitter buffer	*/
94 	unsigned char		*xhead;         /* next byte to XMIT */
95 	int			xleft;          /* bytes left in XMIT queue  */
96 
97 	unsigned char		raw_buf[4];
98 	unsigned char		cooked_buf[400];
99 
100 	unsigned int		rx_count;
101 	unsigned int		rx_count_cooked;
102 	spinlock_t		rxlock;
103 
104 	int			mtu;		/* Our mtu (to spot changes!) */
105 	int			buffsize;       /* Max buffers sizes */
106 
107 	unsigned long		flags;		/* Flag values/ mode etc */
108 	unsigned char		mode;		/* 6pack mode */
109 
110 	/* 6pack stuff */
111 	unsigned char		tx_delay;
112 	unsigned char		persistence;
113 	unsigned char		slottime;
114 	unsigned char		duplex;
115 	unsigned char		led_state;
116 	unsigned char		status;
117 	unsigned char		status1;
118 	unsigned char		status2;
119 	unsigned char		tx_enable;
120 	unsigned char		tnc_state;
121 
122 	struct timer_list	tx_t;
123 	struct timer_list	resync_t;
124 	refcount_t		refcnt;
125 	struct completion	dead;
126 	spinlock_t		lock;
127 };
128 
129 #define AX25_6PACK_HEADER_LEN 0
130 
131 static void sixpack_decode(struct sixpack *, const unsigned char[], int);
132 static int encode_sixpack(unsigned char *, unsigned char *, int, unsigned char);
133 
134 /*
135  * Perform the persistence/slottime algorithm for CSMA access. If the
136  * persistence check was successful, write the data to the serial driver.
137  * Note that in case of DAMA operation, the data is not sent here.
138  */
139 
140 static void sp_xmit_on_air(struct timer_list *t)
141 {
142 	struct sixpack *sp = from_timer(sp, t, tx_t);
143 	int actual, when = sp->slottime;
144 	static unsigned char random;
145 
146 	random = random * 17 + 41;
147 
148 	if (((sp->status1 & SIXP_DCD_MASK) == 0) && (random < sp->persistence)) {
149 		sp->led_state = 0x70;
150 		sp->tty->ops->write(sp->tty, &sp->led_state, 1);
151 		sp->tx_enable = 1;
152 		actual = sp->tty->ops->write(sp->tty, sp->xbuff, sp->status2);
153 		sp->xleft -= actual;
154 		sp->xhead += actual;
155 		sp->led_state = 0x60;
156 		sp->tty->ops->write(sp->tty, &sp->led_state, 1);
157 		sp->status2 = 0;
158 	} else
159 		mod_timer(&sp->tx_t, jiffies + ((when + 1) * HZ) / 100);
160 }
161 
162 /* ----> 6pack timer interrupt handler and friends. <---- */
163 
164 /* Encapsulate one AX.25 frame and stuff into a TTY queue. */
165 static void sp_encaps(struct sixpack *sp, unsigned char *icp, int len)
166 {
167 	unsigned char *msg, *p = icp;
168 	int actual, count;
169 
170 	if (len > sp->mtu) {	/* sp->mtu = AX25_MTU = max. PACLEN = 256 */
171 		msg = "oversized transmit packet!";
172 		goto out_drop;
173 	}
174 
175 	if (p[0] > 5) {
176 		msg = "invalid KISS command";
177 		goto out_drop;
178 	}
179 
180 	if ((p[0] != 0) && (len > 2)) {
181 		msg = "KISS control packet too long";
182 		goto out_drop;
183 	}
184 
185 	if ((p[0] == 0) && (len < 15)) {
186 		msg = "bad AX.25 packet to transmit";
187 		goto out_drop;
188 	}
189 
190 	count = encode_sixpack(p, sp->xbuff, len, sp->tx_delay);
191 	set_bit(TTY_DO_WRITE_WAKEUP, &sp->tty->flags);
192 
193 	switch (p[0]) {
194 	case 1:	sp->tx_delay = p[1];
195 		return;
196 	case 2:	sp->persistence = p[1];
197 		return;
198 	case 3:	sp->slottime = p[1];
199 		return;
200 	case 4:	/* ignored */
201 		return;
202 	case 5:	sp->duplex = p[1];
203 		return;
204 	}
205 
206 	if (p[0] != 0)
207 		return;
208 
209 	/*
210 	 * In case of fullduplex or DAMA operation, we don't take care about the
211 	 * state of the DCD or of any timers, as the determination of the
212 	 * correct time to send is the job of the AX.25 layer. We send
213 	 * immediately after data has arrived.
214 	 */
215 	if (sp->duplex == 1) {
216 		sp->led_state = 0x70;
217 		sp->tty->ops->write(sp->tty, &sp->led_state, 1);
218 		sp->tx_enable = 1;
219 		actual = sp->tty->ops->write(sp->tty, sp->xbuff, count);
220 		sp->xleft = count - actual;
221 		sp->xhead = sp->xbuff + actual;
222 		sp->led_state = 0x60;
223 		sp->tty->ops->write(sp->tty, &sp->led_state, 1);
224 	} else {
225 		sp->xleft = count;
226 		sp->xhead = sp->xbuff;
227 		sp->status2 = count;
228 		sp_xmit_on_air(&sp->tx_t);
229 	}
230 
231 	return;
232 
233 out_drop:
234 	sp->dev->stats.tx_dropped++;
235 	netif_start_queue(sp->dev);
236 	if (net_ratelimit())
237 		printk(KERN_DEBUG "%s: %s - dropped.\n", sp->dev->name, msg);
238 }
239 
240 /* Encapsulate an IP datagram and kick it into a TTY queue. */
241 
242 static netdev_tx_t sp_xmit(struct sk_buff *skb, struct net_device *dev)
243 {
244 	struct sixpack *sp = netdev_priv(dev);
245 
246 	if (skb->protocol == htons(ETH_P_IP))
247 		return ax25_ip_xmit(skb);
248 
249 	spin_lock_bh(&sp->lock);
250 	/* We were not busy, so we are now... :-) */
251 	netif_stop_queue(dev);
252 	dev->stats.tx_bytes += skb->len;
253 	sp_encaps(sp, skb->data, skb->len);
254 	spin_unlock_bh(&sp->lock);
255 
256 	dev_kfree_skb(skb);
257 
258 	return NETDEV_TX_OK;
259 }
260 
261 static int sp_open_dev(struct net_device *dev)
262 {
263 	struct sixpack *sp = netdev_priv(dev);
264 
265 	if (sp->tty == NULL)
266 		return -ENODEV;
267 	return 0;
268 }
269 
270 /* Close the low-level part of the 6pack channel. */
271 static int sp_close(struct net_device *dev)
272 {
273 	struct sixpack *sp = netdev_priv(dev);
274 
275 	spin_lock_bh(&sp->lock);
276 	if (sp->tty) {
277 		/* TTY discipline is running. */
278 		clear_bit(TTY_DO_WRITE_WAKEUP, &sp->tty->flags);
279 	}
280 	netif_stop_queue(dev);
281 	spin_unlock_bh(&sp->lock);
282 
283 	return 0;
284 }
285 
286 static int sp_set_mac_address(struct net_device *dev, void *addr)
287 {
288 	struct sockaddr_ax25 *sa = addr;
289 
290 	netif_tx_lock_bh(dev);
291 	netif_addr_lock(dev);
292 	__dev_addr_set(dev, &sa->sax25_call, AX25_ADDR_LEN);
293 	netif_addr_unlock(dev);
294 	netif_tx_unlock_bh(dev);
295 
296 	return 0;
297 }
298 
299 static const struct net_device_ops sp_netdev_ops = {
300 	.ndo_open		= sp_open_dev,
301 	.ndo_stop		= sp_close,
302 	.ndo_start_xmit		= sp_xmit,
303 	.ndo_set_mac_address    = sp_set_mac_address,
304 };
305 
306 static void sp_setup(struct net_device *dev)
307 {
308 	/* Finish setting up the DEVICE info. */
309 	dev->netdev_ops		= &sp_netdev_ops;
310 	dev->mtu		= SIXP_MTU;
311 	dev->hard_header_len	= AX25_MAX_HEADER_LEN;
312 	dev->header_ops 	= &ax25_header_ops;
313 
314 	dev->addr_len		= AX25_ADDR_LEN;
315 	dev->type		= ARPHRD_AX25;
316 	dev->tx_queue_len	= 10;
317 
318 	/* Only activated in AX.25 mode */
319 	memcpy(dev->broadcast, &ax25_bcast, AX25_ADDR_LEN);
320 	dev_addr_set(dev, (u8 *)&ax25_defaddr);
321 
322 	dev->flags		= 0;
323 }
324 
325 /* Send one completely decapsulated IP datagram to the IP layer. */
326 
327 /*
328  * This is the routine that sends the received data to the kernel AX.25.
329  * 'cmd' is the KISS command. For AX.25 data, it is zero.
330  */
331 
332 static void sp_bump(struct sixpack *sp, char cmd)
333 {
334 	struct sk_buff *skb;
335 	int count;
336 	unsigned char *ptr;
337 
338 	count = sp->rcount + 1;
339 
340 	sp->dev->stats.rx_bytes += count;
341 
342 	if ((skb = dev_alloc_skb(count + 1)) == NULL)
343 		goto out_mem;
344 
345 	ptr = skb_put(skb, count + 1);
346 	*ptr++ = cmd;	/* KISS command */
347 
348 	memcpy(ptr, sp->cooked_buf + 1, count);
349 	skb->protocol = ax25_type_trans(skb, sp->dev);
350 	netif_rx(skb);
351 	sp->dev->stats.rx_packets++;
352 
353 	return;
354 
355 out_mem:
356 	sp->dev->stats.rx_dropped++;
357 }
358 
359 
360 /* ----------------------------------------------------------------------- */
361 
362 /*
363  * We have a potential race on dereferencing tty->disc_data, because the tty
364  * layer provides no locking at all - thus one cpu could be running
365  * sixpack_receive_buf while another calls sixpack_close, which zeroes
366  * tty->disc_data and frees the memory that sixpack_receive_buf is using.  The
367  * best way to fix this is to use a rwlock in the tty struct, but for now we
368  * use a single global rwlock for all ttys in ppp line discipline.
369  */
370 static DEFINE_RWLOCK(disc_data_lock);
371 
372 static struct sixpack *sp_get(struct tty_struct *tty)
373 {
374 	struct sixpack *sp;
375 
376 	read_lock(&disc_data_lock);
377 	sp = tty->disc_data;
378 	if (sp)
379 		refcount_inc(&sp->refcnt);
380 	read_unlock(&disc_data_lock);
381 
382 	return sp;
383 }
384 
385 static void sp_put(struct sixpack *sp)
386 {
387 	if (refcount_dec_and_test(&sp->refcnt))
388 		complete(&sp->dead);
389 }
390 
391 /*
392  * Called by the TTY driver when there's room for more data.  If we have
393  * more packets to send, we send them here.
394  */
395 static void sixpack_write_wakeup(struct tty_struct *tty)
396 {
397 	struct sixpack *sp = sp_get(tty);
398 	int actual;
399 
400 	if (!sp)
401 		return;
402 	if (sp->xleft <= 0)  {
403 		/* Now serial buffer is almost free & we can start
404 		 * transmission of another packet */
405 		sp->dev->stats.tx_packets++;
406 		clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
407 		sp->tx_enable = 0;
408 		netif_wake_queue(sp->dev);
409 		goto out;
410 	}
411 
412 	if (sp->tx_enable) {
413 		actual = tty->ops->write(tty, sp->xhead, sp->xleft);
414 		sp->xleft -= actual;
415 		sp->xhead += actual;
416 	}
417 
418 out:
419 	sp_put(sp);
420 }
421 
422 /* ----------------------------------------------------------------------- */
423 
424 /*
425  * Handle the 'receiver data ready' interrupt.
426  * This function is called by the tty module in the kernel when
427  * a block of 6pack data has been received, which can now be decapsulated
428  * and sent on to some IP layer for further processing.
429  */
430 static void sixpack_receive_buf(struct tty_struct *tty,
431 	const unsigned char *cp, const char *fp, int count)
432 {
433 	struct sixpack *sp;
434 	int count1;
435 
436 	if (!count)
437 		return;
438 
439 	sp = sp_get(tty);
440 	if (!sp)
441 		return;
442 
443 	/* Read the characters out of the buffer */
444 	count1 = count;
445 	while (count) {
446 		count--;
447 		if (fp && *fp++) {
448 			if (!test_and_set_bit(SIXPF_ERROR, &sp->flags))
449 				sp->dev->stats.rx_errors++;
450 			continue;
451 		}
452 	}
453 	sixpack_decode(sp, cp, count1);
454 
455 	sp_put(sp);
456 	tty_unthrottle(tty);
457 }
458 
459 /*
460  * Try to resync the TNC. Called by the resync timer defined in
461  * decode_prio_command
462  */
463 
464 #define TNC_UNINITIALIZED	0
465 #define TNC_UNSYNC_STARTUP	1
466 #define TNC_UNSYNCED		2
467 #define TNC_IN_SYNC		3
468 
469 static void __tnc_set_sync_state(struct sixpack *sp, int new_tnc_state)
470 {
471 	char *msg;
472 
473 	switch (new_tnc_state) {
474 	default:			/* gcc oh piece-o-crap ... */
475 	case TNC_UNSYNC_STARTUP:
476 		msg = "Synchronizing with TNC";
477 		break;
478 	case TNC_UNSYNCED:
479 		msg = "Lost synchronization with TNC\n";
480 		break;
481 	case TNC_IN_SYNC:
482 		msg = "Found TNC";
483 		break;
484 	}
485 
486 	sp->tnc_state = new_tnc_state;
487 	printk(KERN_INFO "%s: %s\n", sp->dev->name, msg);
488 }
489 
490 static inline void tnc_set_sync_state(struct sixpack *sp, int new_tnc_state)
491 {
492 	int old_tnc_state = sp->tnc_state;
493 
494 	if (old_tnc_state != new_tnc_state)
495 		__tnc_set_sync_state(sp, new_tnc_state);
496 }
497 
498 static void resync_tnc(struct timer_list *t)
499 {
500 	struct sixpack *sp = from_timer(sp, t, resync_t);
501 	static char resync_cmd = 0xe8;
502 
503 	/* clear any data that might have been received */
504 
505 	sp->rx_count = 0;
506 	sp->rx_count_cooked = 0;
507 
508 	/* reset state machine */
509 
510 	sp->status = 1;
511 	sp->status1 = 1;
512 	sp->status2 = 0;
513 
514 	/* resync the TNC */
515 
516 	sp->led_state = 0x60;
517 	sp->tty->ops->write(sp->tty, &sp->led_state, 1);
518 	sp->tty->ops->write(sp->tty, &resync_cmd, 1);
519 
520 
521 	/* Start resync timer again -- the TNC might be still absent */
522 	mod_timer(&sp->resync_t, jiffies + SIXP_RESYNC_TIMEOUT);
523 }
524 
525 static inline int tnc_init(struct sixpack *sp)
526 {
527 	unsigned char inbyte = 0xe8;
528 
529 	tnc_set_sync_state(sp, TNC_UNSYNC_STARTUP);
530 
531 	sp->tty->ops->write(sp->tty, &inbyte, 1);
532 
533 	mod_timer(&sp->resync_t, jiffies + SIXP_RESYNC_TIMEOUT);
534 
535 	return 0;
536 }
537 
538 /*
539  * Open the high-level part of the 6pack channel.
540  * This function is called by the TTY module when the
541  * 6pack line discipline is called for.  Because we are
542  * sure the tty line exists, we only have to link it to
543  * a free 6pcack channel...
544  */
545 static int sixpack_open(struct tty_struct *tty)
546 {
547 	char *rbuff = NULL, *xbuff = NULL;
548 	struct net_device *dev;
549 	struct sixpack *sp;
550 	unsigned long len;
551 	int err = 0;
552 
553 	if (!capable(CAP_NET_ADMIN))
554 		return -EPERM;
555 	if (tty->ops->write == NULL)
556 		return -EOPNOTSUPP;
557 
558 	dev = alloc_netdev(sizeof(struct sixpack), "sp%d", NET_NAME_UNKNOWN,
559 			   sp_setup);
560 	if (!dev) {
561 		err = -ENOMEM;
562 		goto out;
563 	}
564 
565 	sp = netdev_priv(dev);
566 	sp->dev = dev;
567 
568 	spin_lock_init(&sp->lock);
569 	spin_lock_init(&sp->rxlock);
570 	refcount_set(&sp->refcnt, 1);
571 	init_completion(&sp->dead);
572 
573 	/* !!! length of the buffers. MTU is IP MTU, not PACLEN!  */
574 
575 	len = dev->mtu * 2;
576 
577 	rbuff = kmalloc(len + 4, GFP_KERNEL);
578 	xbuff = kmalloc(len + 4, GFP_KERNEL);
579 
580 	if (rbuff == NULL || xbuff == NULL) {
581 		err = -ENOBUFS;
582 		goto out_free;
583 	}
584 
585 	spin_lock_bh(&sp->lock);
586 
587 	sp->tty = tty;
588 
589 	sp->rbuff	= rbuff;
590 	sp->xbuff	= xbuff;
591 
592 	sp->mtu		= AX25_MTU + 73;
593 	sp->buffsize	= len;
594 	sp->rcount	= 0;
595 	sp->rx_count	= 0;
596 	sp->rx_count_cooked = 0;
597 	sp->xleft	= 0;
598 
599 	sp->flags	= 0;		/* Clear ESCAPE & ERROR flags */
600 
601 	sp->duplex	= 0;
602 	sp->tx_delay    = SIXP_TXDELAY;
603 	sp->persistence = SIXP_PERSIST;
604 	sp->slottime    = SIXP_SLOTTIME;
605 	sp->led_state   = 0x60;
606 	sp->status      = 1;
607 	sp->status1     = 1;
608 	sp->status2     = 0;
609 	sp->tx_enable   = 0;
610 
611 	netif_start_queue(dev);
612 
613 	timer_setup(&sp->tx_t, sp_xmit_on_air, 0);
614 
615 	timer_setup(&sp->resync_t, resync_tnc, 0);
616 
617 	spin_unlock_bh(&sp->lock);
618 
619 	/* Done.  We have linked the TTY line to a channel. */
620 	tty->disc_data = sp;
621 	tty->receive_room = 65536;
622 
623 	/* Now we're ready to register. */
624 	err = register_netdev(dev);
625 	if (err)
626 		goto out_free;
627 
628 	tnc_init(sp);
629 
630 	return 0;
631 
632 out_free:
633 	kfree(xbuff);
634 	kfree(rbuff);
635 
636 	free_netdev(dev);
637 
638 out:
639 	return err;
640 }
641 
642 
643 /*
644  * Close down a 6pack channel.
645  * This means flushing out any pending queues, and then restoring the
646  * TTY line discipline to what it was before it got hooked to 6pack
647  * (which usually is TTY again).
648  */
649 static void sixpack_close(struct tty_struct *tty)
650 {
651 	struct sixpack *sp;
652 
653 	write_lock_irq(&disc_data_lock);
654 	sp = tty->disc_data;
655 	tty->disc_data = NULL;
656 	write_unlock_irq(&disc_data_lock);
657 	if (!sp)
658 		return;
659 
660 	/*
661 	 * We have now ensured that nobody can start using ap from now on, but
662 	 * we have to wait for all existing users to finish.
663 	 */
664 	if (!refcount_dec_and_test(&sp->refcnt))
665 		wait_for_completion(&sp->dead);
666 
667 	/* We must stop the queue to avoid potentially scribbling
668 	 * on the free buffers. The sp->dead completion is not sufficient
669 	 * to protect us from sp->xbuff access.
670 	 */
671 	netif_stop_queue(sp->dev);
672 
673 	unregister_netdev(sp->dev);
674 
675 	del_timer_sync(&sp->tx_t);
676 	del_timer_sync(&sp->resync_t);
677 
678 	/* Free all 6pack frame buffers after unreg. */
679 	kfree(sp->rbuff);
680 	kfree(sp->xbuff);
681 
682 	free_netdev(sp->dev);
683 }
684 
685 /* Perform I/O control on an active 6pack channel. */
686 static int sixpack_ioctl(struct tty_struct *tty, unsigned int cmd,
687 		unsigned long arg)
688 {
689 	struct sixpack *sp = sp_get(tty);
690 	struct net_device *dev;
691 	unsigned int tmp, err;
692 
693 	if (!sp)
694 		return -ENXIO;
695 	dev = sp->dev;
696 
697 	switch(cmd) {
698 	case SIOCGIFNAME:
699 		err = copy_to_user((void __user *) arg, dev->name,
700 		                   strlen(dev->name) + 1) ? -EFAULT : 0;
701 		break;
702 
703 	case SIOCGIFENCAP:
704 		err = put_user(0, (int __user *) arg);
705 		break;
706 
707 	case SIOCSIFENCAP:
708 		if (get_user(tmp, (int __user *) arg)) {
709 			err = -EFAULT;
710 			break;
711 		}
712 
713 		sp->mode = tmp;
714 		dev->addr_len        = AX25_ADDR_LEN;
715 		dev->hard_header_len = AX25_KISS_HEADER_LEN +
716 		                       AX25_MAX_HEADER_LEN + 3;
717 		dev->type            = ARPHRD_AX25;
718 
719 		err = 0;
720 		break;
721 
722 	case SIOCSIFHWADDR: {
723 			char addr[AX25_ADDR_LEN];
724 
725 			if (copy_from_user(&addr,
726 					   (void __user *)arg, AX25_ADDR_LEN)) {
727 				err = -EFAULT;
728 				break;
729 			}
730 
731 			netif_tx_lock_bh(dev);
732 			__dev_addr_set(dev, &addr, AX25_ADDR_LEN);
733 			netif_tx_unlock_bh(dev);
734 			err = 0;
735 			break;
736 		}
737 	default:
738 		err = tty_mode_ioctl(tty, cmd, arg);
739 	}
740 
741 	sp_put(sp);
742 
743 	return err;
744 }
745 
746 static struct tty_ldisc_ops sp_ldisc = {
747 	.owner		= THIS_MODULE,
748 	.num		= N_6PACK,
749 	.name		= "6pack",
750 	.open		= sixpack_open,
751 	.close		= sixpack_close,
752 	.ioctl		= sixpack_ioctl,
753 	.receive_buf	= sixpack_receive_buf,
754 	.write_wakeup	= sixpack_write_wakeup,
755 };
756 
757 /* Initialize 6pack control device -- register 6pack line discipline */
758 
759 static const char msg_banner[]  __initconst = KERN_INFO \
760 	"AX.25: 6pack driver, " SIXPACK_VERSION "\n";
761 static const char msg_regfail[] __initconst = KERN_ERR  \
762 	"6pack: can't register line discipline (err = %d)\n";
763 
764 static int __init sixpack_init_driver(void)
765 {
766 	int status;
767 
768 	printk(msg_banner);
769 
770 	/* Register the provided line protocol discipline */
771 	status = tty_register_ldisc(&sp_ldisc);
772 	if (status)
773 		printk(msg_regfail, status);
774 
775 	return status;
776 }
777 
778 static void __exit sixpack_exit_driver(void)
779 {
780 	tty_unregister_ldisc(&sp_ldisc);
781 }
782 
783 /* encode an AX.25 packet into 6pack */
784 
785 static int encode_sixpack(unsigned char *tx_buf, unsigned char *tx_buf_raw,
786 	int length, unsigned char tx_delay)
787 {
788 	int count = 0;
789 	unsigned char checksum = 0, buf[400];
790 	int raw_count = 0;
791 
792 	tx_buf_raw[raw_count++] = SIXP_PRIO_CMD_MASK | SIXP_TX_MASK;
793 	tx_buf_raw[raw_count++] = SIXP_SEOF;
794 
795 	buf[0] = tx_delay;
796 	for (count = 1; count < length; count++)
797 		buf[count] = tx_buf[count];
798 
799 	for (count = 0; count < length; count++)
800 		checksum += buf[count];
801 	buf[length] = (unsigned char) 0xff - checksum;
802 
803 	for (count = 0; count <= length; count++) {
804 		if ((count % 3) == 0) {
805 			tx_buf_raw[raw_count++] = (buf[count] & 0x3f);
806 			tx_buf_raw[raw_count] = ((buf[count] >> 2) & 0x30);
807 		} else if ((count % 3) == 1) {
808 			tx_buf_raw[raw_count++] |= (buf[count] & 0x0f);
809 			tx_buf_raw[raw_count] =	((buf[count] >> 2) & 0x3c);
810 		} else {
811 			tx_buf_raw[raw_count++] |= (buf[count] & 0x03);
812 			tx_buf_raw[raw_count++] = (buf[count] >> 2);
813 		}
814 	}
815 	if ((length % 3) != 2)
816 		raw_count++;
817 	tx_buf_raw[raw_count++] = SIXP_SEOF;
818 	return raw_count;
819 }
820 
821 /* decode 4 sixpack-encoded bytes into 3 data bytes */
822 
823 static void decode_data(struct sixpack *sp, unsigned char inbyte)
824 {
825 	unsigned char *buf;
826 
827 	if (sp->rx_count != 3) {
828 		sp->raw_buf[sp->rx_count++] = inbyte;
829 
830 		return;
831 	}
832 
833 	if (sp->rx_count_cooked + 2 >= sizeof(sp->cooked_buf)) {
834 		pr_err("6pack: cooked buffer overrun, data loss\n");
835 		sp->rx_count = 0;
836 		return;
837 	}
838 
839 	buf = sp->raw_buf;
840 	sp->cooked_buf[sp->rx_count_cooked++] =
841 		buf[0] | ((buf[1] << 2) & 0xc0);
842 	sp->cooked_buf[sp->rx_count_cooked++] =
843 		(buf[1] & 0x0f) | ((buf[2] << 2) & 0xf0);
844 	sp->cooked_buf[sp->rx_count_cooked++] =
845 		(buf[2] & 0x03) | (inbyte << 2);
846 	sp->rx_count = 0;
847 }
848 
849 /* identify and execute a 6pack priority command byte */
850 
851 static void decode_prio_command(struct sixpack *sp, unsigned char cmd)
852 {
853 	int actual;
854 
855 	if ((cmd & SIXP_PRIO_DATA_MASK) != 0) {     /* idle ? */
856 
857 	/* RX and DCD flags can only be set in the same prio command,
858 	   if the DCD flag has been set without the RX flag in the previous
859 	   prio command. If DCD has not been set before, something in the
860 	   transmission has gone wrong. In this case, RX and DCD are
861 	   cleared in order to prevent the decode_data routine from
862 	   reading further data that might be corrupt. */
863 
864 		if (((sp->status & SIXP_DCD_MASK) == 0) &&
865 			((cmd & SIXP_RX_DCD_MASK) == SIXP_RX_DCD_MASK)) {
866 				if (sp->status != 1)
867 					printk(KERN_DEBUG "6pack: protocol violation\n");
868 				else
869 					sp->status = 0;
870 				cmd &= ~SIXP_RX_DCD_MASK;
871 		}
872 		sp->status = cmd & SIXP_PRIO_DATA_MASK;
873 	} else { /* output watchdog char if idle */
874 		if ((sp->status2 != 0) && (sp->duplex == 1)) {
875 			sp->led_state = 0x70;
876 			sp->tty->ops->write(sp->tty, &sp->led_state, 1);
877 			sp->tx_enable = 1;
878 			actual = sp->tty->ops->write(sp->tty, sp->xbuff, sp->status2);
879 			sp->xleft -= actual;
880 			sp->xhead += actual;
881 			sp->led_state = 0x60;
882 			sp->status2 = 0;
883 
884 		}
885 	}
886 
887 	/* needed to trigger the TNC watchdog */
888 	sp->tty->ops->write(sp->tty, &sp->led_state, 1);
889 
890         /* if the state byte has been received, the TNC is present,
891            so the resync timer can be reset. */
892 
893 	if (sp->tnc_state == TNC_IN_SYNC)
894 		mod_timer(&sp->resync_t, jiffies + SIXP_INIT_RESYNC_TIMEOUT);
895 
896 	sp->status1 = cmd & SIXP_PRIO_DATA_MASK;
897 }
898 
899 /* identify and execute a standard 6pack command byte */
900 
901 static void decode_std_command(struct sixpack *sp, unsigned char cmd)
902 {
903 	unsigned char checksum = 0, rest = 0;
904 	short i;
905 
906 	switch (cmd & SIXP_CMD_MASK) {     /* normal command */
907 	case SIXP_SEOF:
908 		if ((sp->rx_count == 0) && (sp->rx_count_cooked == 0)) {
909 			if ((sp->status & SIXP_RX_DCD_MASK) ==
910 				SIXP_RX_DCD_MASK) {
911 				sp->led_state = 0x68;
912 				sp->tty->ops->write(sp->tty, &sp->led_state, 1);
913 			}
914 		} else {
915 			sp->led_state = 0x60;
916 			/* fill trailing bytes with zeroes */
917 			sp->tty->ops->write(sp->tty, &sp->led_state, 1);
918 			spin_lock_bh(&sp->rxlock);
919 			rest = sp->rx_count;
920 			if (rest != 0)
921 				 for (i = rest; i <= 3; i++)
922 					decode_data(sp, 0);
923 			if (rest == 2)
924 				sp->rx_count_cooked -= 2;
925 			else if (rest == 3)
926 				sp->rx_count_cooked -= 1;
927 			for (i = 0; i < sp->rx_count_cooked; i++)
928 				checksum += sp->cooked_buf[i];
929 			if (checksum != SIXP_CHKSUM) {
930 				printk(KERN_DEBUG "6pack: bad checksum %2.2x\n", checksum);
931 			} else {
932 				sp->rcount = sp->rx_count_cooked-2;
933 				sp_bump(sp, 0);
934 			}
935 			sp->rx_count_cooked = 0;
936 			spin_unlock_bh(&sp->rxlock);
937 		}
938 		break;
939 	case SIXP_TX_URUN: printk(KERN_DEBUG "6pack: TX underrun\n");
940 		break;
941 	case SIXP_RX_ORUN: printk(KERN_DEBUG "6pack: RX overrun\n");
942 		break;
943 	case SIXP_RX_BUF_OVL:
944 		printk(KERN_DEBUG "6pack: RX buffer overflow\n");
945 	}
946 }
947 
948 /* decode a 6pack packet */
949 
950 static void
951 sixpack_decode(struct sixpack *sp, const unsigned char *pre_rbuff, int count)
952 {
953 	unsigned char inbyte;
954 	int count1;
955 
956 	for (count1 = 0; count1 < count; count1++) {
957 		inbyte = pre_rbuff[count1];
958 		if (inbyte == SIXP_FOUND_TNC) {
959 			tnc_set_sync_state(sp, TNC_IN_SYNC);
960 			del_timer(&sp->resync_t);
961 		}
962 		if ((inbyte & SIXP_PRIO_CMD_MASK) != 0)
963 			decode_prio_command(sp, inbyte);
964 		else if ((inbyte & SIXP_STD_CMD_MASK) != 0)
965 			decode_std_command(sp, inbyte);
966 		else if ((sp->status & SIXP_RX_DCD_MASK) == SIXP_RX_DCD_MASK) {
967 			spin_lock_bh(&sp->rxlock);
968 			decode_data(sp, inbyte);
969 			spin_unlock_bh(&sp->rxlock);
970 		}
971 	}
972 }
973 
974 MODULE_AUTHOR("Ralf Baechle DO1GRB <ralf@linux-mips.org>");
975 MODULE_DESCRIPTION("6pack driver for AX.25");
976 MODULE_LICENSE("GPL");
977 MODULE_ALIAS_LDISC(N_6PACK);
978 
979 module_init(sixpack_init_driver);
980 module_exit(sixpack_exit_driver);
981