slcan-core.c

  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 and got
  5 * inspiration from linux/drivers/net/can/can327.c for the rework made
  6 * on the line discipline code.
  7 *
  8 * slip.c Authors  : Laurence Culhane <loz@holmes.demon.co.uk>
  9 *                   Fred N. van Kempen <waltje@uwalt.nl.mugnet.org>
 10 * slcan.c Author  : Oliver Hartkopp <socketcan@hartkopp.net>
 11 * can327.c Author : Max Staudt <max-linux@enpas.org>
 12 *
 13 * This program is free software; you can redistribute it and/or modify it
 14 * under the terms of the GNU General Public License as published by the
 15 * Free Software Foundation; either version 2 of the License, or (at your
 16 * option) any later version.
 17 *
 18 * This program is distributed in the hope that it will be useful, but
 19 * WITHOUT ANY WARRANTY; without even the implied warranty of
 20 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 21 * General Public License for more details.
 22 *
 23 * You should have received a copy of the GNU General Public License along
 24 * with this program; if not, see http://www.gnu.org/licenses/gpl.html
 25 *
 26 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 27 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 28 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 29 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 30 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 31 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 32 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 33 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 34 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 35 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 36 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
 37 * DAMAGE.
 38 *
 39 */
 40
 41#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
 42
 43#include <linux/module.h>
 44
 45#include <linux/uaccess.h>
 46#include <linux/bitops.h>
 47#include <linux/string.h>
 48#include <linux/tty.h>
 49#include <linux/errno.h>
 50#include <linux/netdevice.h>
 51#include <linux/skbuff.h>
 52#include <linux/rtnetlink.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/dev.h>
 58#include <linux/can/skb.h>
 59
 60#include "slcan.h"
 61
 62MODULE_ALIAS_LDISC(N_SLCAN);
 63MODULE_DESCRIPTION("serial line CAN interface");
 64MODULE_LICENSE("GPL");
 65MODULE_AUTHOR("Oliver Hartkopp <socketcan@hartkopp.net>");
 66MODULE_AUTHOR("Dario Binacchi <dario.binacchi@amarulasolutions.com>");
 67
 68/* maximum rx buffer len: extended CAN frame with timestamp */
 69#define SLCAN_MTU (sizeof("T1111222281122334455667788EA5F\r") + 1)
 70
 71#define SLCAN_CMD_LEN 1
 72#define SLCAN_SFF_ID_LEN 3
 73#define SLCAN_EFF_ID_LEN 8
 74#define SLCAN_DATA_LENGTH_LEN 1
 75#define SLCAN_ERROR_LEN 1
 76#define SLCAN_STATE_LEN 1
 77#define SLCAN_STATE_BE_RXCNT_LEN 3
 78#define SLCAN_STATE_BE_TXCNT_LEN 3
 79#define SLCAN_STATE_MSG_LEN     (SLCAN_CMD_LEN +		\
 80                                 SLCAN_STATE_LEN +		\
 81                                 SLCAN_STATE_BE_RXCNT_LEN +	\
 82                                 SLCAN_STATE_BE_TXCNT_LEN)
 83#define SLCAN_ERROR_MSG_LEN_MIN (SLCAN_CMD_LEN +	\
 84                                 SLCAN_ERROR_LEN +	\
 85                                 SLCAN_DATA_LENGTH_LEN)
 86#define SLCAN_FRAME_MSG_LEN_MIN (SLCAN_CMD_LEN +	\
 87                                 SLCAN_SFF_ID_LEN +	\
 88                                 SLCAN_DATA_LENGTH_LEN)
 89struct slcan {
 90	struct can_priv         can;
 91
 92	/* Various fields. */
 93	struct tty_struct	*tty;		/* ptr to TTY structure	     */
 94	struct net_device	*dev;		/* easy for intr handling    */
 95	spinlock_t		lock;
 96	struct work_struct	tx_work;	/* Flushes transmit buffer   */
 97
 98	/* These are pointers to the malloc()ed frame buffers. */
 99	unsigned char		rbuff[SLCAN_MTU];	/* receiver buffer   */
100	int			rcount;         /* received chars counter    */
101	unsigned char		xbuff[SLCAN_MTU];	/* transmitter buffer*/
102	unsigned char		*xhead;         /* pointer to next XMIT byte */
103	int			xleft;          /* bytes left in XMIT queue  */
104
105	unsigned long		flags;		/* Flag values/ mode etc     */
106#define SLF_ERROR		0               /* Parity, etc. error        */
107#define SLF_XCMD		1               /* Command transmission      */
108	unsigned long           cmd_flags;      /* Command flags             */
109#define CF_ERR_RST		0               /* Reset errors on open      */
110	wait_queue_head_t       xcmd_wait;      /* Wait queue for commands   */
111						/* transmission              */
112};
113
114static const u32 slcan_bitrate_const[] = {
115	10000, 20000, 50000, 100000, 125000,
116	250000, 500000, 800000, 1000000
117};
118
119bool slcan_err_rst_on_open(struct net_device *ndev)
120{
121	struct slcan *sl = netdev_priv(ndev);
122
123	return !!test_bit(CF_ERR_RST, &sl->cmd_flags);
124}
125
126int slcan_enable_err_rst_on_open(struct net_device *ndev, bool on)
127{
128	struct slcan *sl = netdev_priv(ndev);
129
130	if (netif_running(ndev))
131		return -EBUSY;
132
133	if (on)
134		set_bit(CF_ERR_RST, &sl->cmd_flags);
135	else
136		clear_bit(CF_ERR_RST, &sl->cmd_flags);
137
138	return 0;
139}
140
141/*************************************************************************
142 *			SLCAN ENCAPSULATION FORMAT			 *
143 *************************************************************************/
144
145/* A CAN frame has a can_id (11 bit standard frame format OR 29 bit extended
146 * frame format) a data length code (len) which can be from 0 to 8
147 * and up to <len> data bytes as payload.
148 * Additionally a CAN frame may become a remote transmission frame if the
149 * RTR-bit is set. This causes another ECU to send a CAN frame with the
150 * given can_id.
151 *
152 * The SLCAN ASCII representation of these different frame types is:
153 * <type> <id> <dlc> <data>*
154 *
155 * Extended frames (29 bit) are defined by capital characters in the type.
156 * RTR frames are defined as 'r' types - normal frames have 't' type:
157 * t => 11 bit data frame
158 * r => 11 bit RTR frame
159 * T => 29 bit data frame
160 * R => 29 bit RTR frame
161 *
162 * The <id> is 3 (standard) or 8 (extended) bytes in ASCII Hex (base64).
163 * The <dlc> is a one byte ASCII number ('0' - '8')
164 * The <data> section has at much ASCII Hex bytes as defined by the <dlc>
165 *
166 * Examples:
167 *
168 * t1230 : can_id 0x123, len 0, no data
169 * t4563112233 : can_id 0x456, len 3, data 0x11 0x22 0x33
170 * T12ABCDEF2AA55 : extended can_id 0x12ABCDEF, len 2, data 0xAA 0x55
171 * r1230 : can_id 0x123, len 0, no data, remote transmission request
172 *
173 */
174
175/*************************************************************************
176 *			STANDARD SLCAN DECAPSULATION			 *
177 *************************************************************************/
178
179/* Send one completely decapsulated can_frame to the network layer */
180static void slcan_bump_frame(struct slcan *sl)
181{
182	struct sk_buff *skb;
183	struct can_frame *cf;
184	int i, tmp;
185	u32 tmpid;
186	char *cmd = sl->rbuff;
187
188	if (sl->rcount < SLCAN_FRAME_MSG_LEN_MIN)
189		return;
190
191	skb = alloc_can_skb(sl->dev, &cf);
192	if (unlikely(!skb)) {
193		sl->dev->stats.rx_dropped++;
194		return;
195	}
196
197	switch (*cmd) {
198	case 'r':
199		cf->can_id = CAN_RTR_FLAG;
200		fallthrough;
201	case 't':
202		/* store dlc ASCII value and terminate SFF CAN ID string */
203		cf->len = sl->rbuff[SLCAN_CMD_LEN + SLCAN_SFF_ID_LEN];
204		sl->rbuff[SLCAN_CMD_LEN + SLCAN_SFF_ID_LEN] = 0;
205		/* point to payload data behind the dlc */
206		cmd += SLCAN_CMD_LEN + SLCAN_SFF_ID_LEN + 1;
207		break;
208	case 'R':
209		cf->can_id = CAN_RTR_FLAG;
210		fallthrough;
211	case 'T':
212		cf->can_id |= CAN_EFF_FLAG;
213		/* store dlc ASCII value and terminate EFF CAN ID string */
214		cf->len = sl->rbuff[SLCAN_CMD_LEN + SLCAN_EFF_ID_LEN];
215		sl->rbuff[SLCAN_CMD_LEN + SLCAN_EFF_ID_LEN] = 0;
216		/* point to payload data behind the dlc */
217		cmd += SLCAN_CMD_LEN + SLCAN_EFF_ID_LEN + 1;
218		break;
219	default:
220		goto decode_failed;
221	}
222
223	if (kstrtou32(sl->rbuff + SLCAN_CMD_LEN, 16, &tmpid))
224		goto decode_failed;
225
226	cf->can_id |= tmpid;
227
228	/* get len from sanitized ASCII value */
229	if (cf->len >= '0' && cf->len < '9')
230		cf->len -= '0';
231	else
232		goto decode_failed;
233
234	/* RTR frames may have a dlc > 0 but they never have any data bytes */
235	if (!(cf->can_id & CAN_RTR_FLAG)) {
236		for (i = 0; i < cf->len; i++) {
237			tmp = hex_to_bin(*cmd++);
238			if (tmp < 0)
239				goto decode_failed;
240
241			cf->data[i] = (tmp << 4);
242			tmp = hex_to_bin(*cmd++);
243			if (tmp < 0)
244				goto decode_failed;
245
246			cf->data[i] |= tmp;
247		}
248	}
249
250	sl->dev->stats.rx_packets++;
251	if (!(cf->can_id & CAN_RTR_FLAG))
252		sl->dev->stats.rx_bytes += cf->len;
253
254	netif_rx(skb);
255	return;
256
257decode_failed:
258	sl->dev->stats.rx_errors++;
259	dev_kfree_skb(skb);
260}
261
262/* A change state frame must contain state info and receive and transmit
263 * error counters.
264 *
265 * Examples:
266 *
267 * sb256256 : state bus-off: rx counter 256, tx counter 256
268 * sa057033 : state active, rx counter 57, tx counter 33
269 */
270static void slcan_bump_state(struct slcan *sl)
271{
272	struct net_device *dev = sl->dev;
273	struct sk_buff *skb;
274	struct can_frame *cf;
275	char *cmd = sl->rbuff;
276	u32 rxerr, txerr;
277	enum can_state state, rx_state, tx_state;
278
279	switch (cmd[1]) {
280	case 'a':
281		state = CAN_STATE_ERROR_ACTIVE;
282		break;
283	case 'w':
284		state = CAN_STATE_ERROR_WARNING;
285		break;
286	case 'p':
287		state = CAN_STATE_ERROR_PASSIVE;
288		break;
289	case 'b':
290		state = CAN_STATE_BUS_OFF;
291		break;
292	default:
293		return;
294	}
295
296	if (state == sl->can.state || sl->rcount != SLCAN_STATE_MSG_LEN)
297		return;
298
299	cmd += SLCAN_STATE_BE_RXCNT_LEN + SLCAN_CMD_LEN + 1;
300	cmd[SLCAN_STATE_BE_TXCNT_LEN] = 0;
301	if (kstrtou32(cmd, 10, &txerr))
302		return;
303
304	*cmd = 0;
305	cmd -= SLCAN_STATE_BE_RXCNT_LEN;
306	if (kstrtou32(cmd, 10, &rxerr))
307		return;
308
309	skb = alloc_can_err_skb(dev, &cf);
310
311	tx_state = txerr >= rxerr ? state : 0;
312	rx_state = txerr <= rxerr ? state : 0;
313	can_change_state(dev, cf, tx_state, rx_state);
314
315	if (state == CAN_STATE_BUS_OFF) {
316		can_bus_off(dev);
317	} else if (skb) {
318		cf->can_id |= CAN_ERR_CNT;
319		cf->data[6] = txerr;
320		cf->data[7] = rxerr;
321	}
322
323	if (skb)
324		netif_rx(skb);
325}
326
327/* An error frame can contain more than one type of error.
328 *
329 * Examples:
330 *
331 * e1a : len 1, errors: ACK error
332 * e3bcO: len 3, errors: Bit0 error, CRC error, Tx overrun error
333 */
334static void slcan_bump_err(struct slcan *sl)
335{
336	struct net_device *dev = sl->dev;
337	struct sk_buff *skb;
338	struct can_frame *cf;
339	char *cmd = sl->rbuff;
340	bool rx_errors = false, tx_errors = false, rx_over_errors = false;
341	int i, len;
342
343	if (sl->rcount < SLCAN_ERROR_MSG_LEN_MIN)
344		return;
345
346	/* get len from sanitized ASCII value */
347	len = cmd[1];
348	if (len >= '0' && len < '9')
349		len -= '0';
350	else
351		return;
352
353	if ((len + SLCAN_CMD_LEN + 1) > sl->rcount)
354		return;
355
356	skb = alloc_can_err_skb(dev, &cf);
357
358	if (skb)
359		cf->can_id |= CAN_ERR_PROT | CAN_ERR_BUSERROR;
360
361	cmd += SLCAN_CMD_LEN + 1;
362	for (i = 0; i < len; i++, cmd++) {
363		switch (*cmd) {
364		case 'a':
365			netdev_dbg(dev, "ACK error\n");
366			tx_errors = true;
367			if (skb) {
368				cf->can_id |= CAN_ERR_ACK;
369				cf->data[3] = CAN_ERR_PROT_LOC_ACK;
370			}
371
372			break;
373		case 'b':
374			netdev_dbg(dev, "Bit0 error\n");
375			tx_errors = true;
376			if (skb)
377				cf->data[2] |= CAN_ERR_PROT_BIT0;
378
379			break;
380		case 'B':
381			netdev_dbg(dev, "Bit1 error\n");
382			tx_errors = true;
383			if (skb)
384				cf->data[2] |= CAN_ERR_PROT_BIT1;
385
386			break;
387		case 'c':
388			netdev_dbg(dev, "CRC error\n");
389			rx_errors = true;
390			if (skb) {
391				cf->data[2] |= CAN_ERR_PROT_BIT;
392				cf->data[3] = CAN_ERR_PROT_LOC_CRC_SEQ;
393			}
394
395			break;
396		case 'f':
397			netdev_dbg(dev, "Form Error\n");
398			rx_errors = true;
399			if (skb)
400				cf->data[2] |= CAN_ERR_PROT_FORM;
401
402			break;
403		case 'o':
404			netdev_dbg(dev, "Rx overrun error\n");
405			rx_over_errors = true;
406			rx_errors = true;
407			if (skb) {
408				cf->can_id |= CAN_ERR_CRTL;
409				cf->data[1] = CAN_ERR_CRTL_RX_OVERFLOW;
410			}
411
412			break;
413		case 'O':
414			netdev_dbg(dev, "Tx overrun error\n");
415			tx_errors = true;
416			if (skb) {
417				cf->can_id |= CAN_ERR_CRTL;
418				cf->data[1] = CAN_ERR_CRTL_TX_OVERFLOW;
419			}
420
421			break;
422		case 's':
423			netdev_dbg(dev, "Stuff error\n");
424			rx_errors = true;
425			if (skb)
426				cf->data[2] |= CAN_ERR_PROT_STUFF;
427
428			break;
429		default:
430			if (skb)
431				dev_kfree_skb(skb);
432
433			return;
434		}
435	}
436
437	if (rx_errors)
438		dev->stats.rx_errors++;
439
440	if (rx_over_errors)
441		dev->stats.rx_over_errors++;
442
443	if (tx_errors)
444		dev->stats.tx_errors++;
445
446	if (skb)
447		netif_rx(skb);
448}
449
450static void slcan_bump(struct slcan *sl)
451{
452	switch (sl->rbuff[0]) {
453	case 'r':
454		fallthrough;
455	case 't':
456		fallthrough;
457	case 'R':
458		fallthrough;
459	case 'T':
460		return slcan_bump_frame(sl);
461	case 'e':
462		return slcan_bump_err(sl);
463	case 's':
464		return slcan_bump_state(sl);
465	default:
466		return;
467	}
468}
469
470/* parse tty input stream */
471static void slcan_unesc(struct slcan *sl, unsigned char s)
472{
473	if ((s == '\r') || (s == '\a')) { /* CR or BEL ends the pdu */
474		if (!test_and_clear_bit(SLF_ERROR, &sl->flags))
475			slcan_bump(sl);
476
477		sl->rcount = 0;
478	} else {
479		if (!test_bit(SLF_ERROR, &sl->flags))  {
480			if (sl->rcount < SLCAN_MTU)  {
481				sl->rbuff[sl->rcount++] = s;
482				return;
483			}
484
485			sl->dev->stats.rx_over_errors++;
486			set_bit(SLF_ERROR, &sl->flags);
487		}
488	}
489}
490
491/*************************************************************************
492 *			STANDARD SLCAN ENCAPSULATION			 *
493 *************************************************************************/
494
495/* Encapsulate one can_frame and stuff into a TTY queue. */
496static void slcan_encaps(struct slcan *sl, struct can_frame *cf)
497{
498	int actual, i;
499	unsigned char *pos;
500	unsigned char *endpos;
501	canid_t id = cf->can_id;
502
503	pos = sl->xbuff;
504
505	if (cf->can_id & CAN_RTR_FLAG)
506		*pos = 'R'; /* becomes 'r' in standard frame format (SFF) */
507	else
508		*pos = 'T'; /* becomes 't' in standard frame format (SSF) */
509
510	/* determine number of chars for the CAN-identifier */
511	if (cf->can_id & CAN_EFF_FLAG) {
512		id &= CAN_EFF_MASK;
513		endpos = pos + SLCAN_EFF_ID_LEN;
514	} else {
515		*pos |= 0x20; /* convert R/T to lower case for SFF */
516		id &= CAN_SFF_MASK;
517		endpos = pos + SLCAN_SFF_ID_LEN;
518	}
519
520	/* build 3 (SFF) or 8 (EFF) digit CAN identifier */
521	pos++;
522	while (endpos >= pos) {
523		*endpos-- = hex_asc_upper[id & 0xf];
524		id >>= 4;
525	}
526
527	pos += (cf->can_id & CAN_EFF_FLAG) ?
528		SLCAN_EFF_ID_LEN : SLCAN_SFF_ID_LEN;
529
530	*pos++ = cf->len + '0';
531
532	/* RTR frames may have a dlc > 0 but they never have any data bytes */
533	if (!(cf->can_id & CAN_RTR_FLAG)) {
534		for (i = 0; i < cf->len; i++)
535			pos = hex_byte_pack_upper(pos, cf->data[i]);
536
537		sl->dev->stats.tx_bytes += cf->len;
538	}
539
540	*pos++ = '\r';
541
542	/* Order of next two lines is *very* important.
543	 * When we are sending a little amount of data,
544	 * the transfer may be completed inside the ops->write()
545	 * routine, because it's running with interrupts enabled.
546	 * In this case we *never* got WRITE_WAKEUP event,
547	 * if we did not request it before write operation.
548	 *       14 Oct 1994  Dmitry Gorodchanin.
549	 */
550	set_bit(TTY_DO_WRITE_WAKEUP, &sl->tty->flags);
551	actual = sl->tty->ops->write(sl->tty, sl->xbuff, pos - sl->xbuff);
552	sl->xleft = (pos - sl->xbuff) - actual;
553	sl->xhead = sl->xbuff + actual;
554}
555
556/* Write out any remaining transmit buffer. Scheduled when tty is writable */
557static void slcan_transmit(struct work_struct *work)
558{
559	struct slcan *sl = container_of(work, struct slcan, tx_work);
560	int actual;
561
562	spin_lock_bh(&sl->lock);
563	/* First make sure we're connected. */
564	if (unlikely(!netif_running(sl->dev)) &&
565	    likely(!test_bit(SLF_XCMD, &sl->flags))) {
566		spin_unlock_bh(&sl->lock);
567		return;
568	}
569
570	if (sl->xleft <= 0)  {
571		if (unlikely(test_bit(SLF_XCMD, &sl->flags))) {
572			clear_bit(SLF_XCMD, &sl->flags);
573			clear_bit(TTY_DO_WRITE_WAKEUP, &sl->tty->flags);
574			spin_unlock_bh(&sl->lock);
575			wake_up(&sl->xcmd_wait);
576			return;
577		}
578
579		/* Now serial buffer is almost free & we can start
580		 * transmission of another packet
581		 */
582		sl->dev->stats.tx_packets++;
583		clear_bit(TTY_DO_WRITE_WAKEUP, &sl->tty->flags);
584		spin_unlock_bh(&sl->lock);
585		netif_wake_queue(sl->dev);
586		return;
587	}
588
589	actual = sl->tty->ops->write(sl->tty, sl->xhead, sl->xleft);
590	sl->xleft -= actual;
591	sl->xhead += actual;
592	spin_unlock_bh(&sl->lock);
593}
594
595/* Called by the driver when there's room for more data.
596 * Schedule the transmit.
597 */
598static void slcan_write_wakeup(struct tty_struct *tty)
599{
600	struct slcan *sl = tty->disc_data;
601
602	schedule_work(&sl->tx_work);
603}
604
605/* Send a can_frame to a TTY queue. */
606static netdev_tx_t slcan_netdev_xmit(struct sk_buff *skb,
607				     struct net_device *dev)
608{
609	struct slcan *sl = netdev_priv(dev);
610
611	if (can_dev_dropped_skb(dev, skb))
612		return NETDEV_TX_OK;
613
614	spin_lock(&sl->lock);
615	if (!netif_running(dev))  {
616		spin_unlock(&sl->lock);
617		netdev_warn(dev, "xmit: iface is down\n");
618		goto out;
619	}
620	if (!sl->tty) {
621		spin_unlock(&sl->lock);
622		goto out;
623	}
624
625	netif_stop_queue(sl->dev);
626	slcan_encaps(sl, (struct can_frame *)skb->data); /* encaps & send */
627	spin_unlock(&sl->lock);
628
629	skb_tx_timestamp(skb);
630
631out:
632	kfree_skb(skb);
633	return NETDEV_TX_OK;
634}
635
636/******************************************
637 *   Routines looking at netdevice side.
638 ******************************************/
639
640static int slcan_transmit_cmd(struct slcan *sl, const unsigned char *cmd)
641{
642	int ret, actual, n;
643
644	spin_lock(&sl->lock);
645	if (!sl->tty) {
646		spin_unlock(&sl->lock);
647		return -ENODEV;
648	}
649
650	n = scnprintf(sl->xbuff, sizeof(sl->xbuff), "%s", cmd);
651	set_bit(TTY_DO_WRITE_WAKEUP, &sl->tty->flags);
652	actual = sl->tty->ops->write(sl->tty, sl->xbuff, n);
653	sl->xleft = n - actual;
654	sl->xhead = sl->xbuff + actual;
655	set_bit(SLF_XCMD, &sl->flags);
656	spin_unlock(&sl->lock);
657	ret = wait_event_interruptible_timeout(sl->xcmd_wait,
658					       !test_bit(SLF_XCMD, &sl->flags),
659					       HZ);
660	clear_bit(SLF_XCMD, &sl->flags);
661	if (ret == -ERESTARTSYS)
662		return ret;
663
664	if (ret == 0)
665		return -ETIMEDOUT;
666
667	return 0;
668}
669
670/* Netdevice UP -> DOWN routine */
671static int slcan_netdev_close(struct net_device *dev)
672{
673	struct slcan *sl = netdev_priv(dev);
674	int err;
675
676	if (sl->can.bittiming.bitrate &&
677	    sl->can.bittiming.bitrate != CAN_BITRATE_UNKNOWN) {
678		err = slcan_transmit_cmd(sl, "C\r");
679		if (err)
680			netdev_warn(dev,
681				    "failed to send close command 'C\\r'\n");
682	}
683
684	/* TTY discipline is running. */
685	clear_bit(TTY_DO_WRITE_WAKEUP, &sl->tty->flags);
686	flush_work(&sl->tx_work);
687
688	netif_stop_queue(dev);
689	sl->rcount   = 0;
690	sl->xleft    = 0;
691	close_candev(dev);
692	sl->can.state = CAN_STATE_STOPPED;
693	if (sl->can.bittiming.bitrate == CAN_BITRATE_UNKNOWN)
694		sl->can.bittiming.bitrate = CAN_BITRATE_UNSET;
695
696	return 0;
697}
698
699/* Netdevice DOWN -> UP routine */
700static int slcan_netdev_open(struct net_device *dev)
701{
702	struct slcan *sl = netdev_priv(dev);
703	unsigned char cmd[SLCAN_MTU];
704	int err, s;
705
706	/* The baud rate is not set with the command
707	 * `ip link set <iface> type can bitrate <baud>' and therefore
708	 * can.bittiming.bitrate is CAN_BITRATE_UNSET (0), causing
709	 * open_candev() to fail. So let's set to a fake value.
710	 */
711	if (sl->can.bittiming.bitrate == CAN_BITRATE_UNSET)
712		sl->can.bittiming.bitrate = CAN_BITRATE_UNKNOWN;
713
714	err = open_candev(dev);
715	if (err) {
716		netdev_err(dev, "failed to open can device\n");
717		return err;
718	}
719
720	if (sl->can.bittiming.bitrate != CAN_BITRATE_UNKNOWN) {
721		for (s = 0; s < ARRAY_SIZE(slcan_bitrate_const); s++) {
722			if (sl->can.bittiming.bitrate == slcan_bitrate_const[s])
723				break;
724		}
725
726		/* The CAN framework has already validate the bitrate value,
727		 * so we can avoid to check if `s' has been properly set.
728		 */
729		snprintf(cmd, sizeof(cmd), "C\rS%d\r", s);
730		err = slcan_transmit_cmd(sl, cmd);
731		if (err) {
732			netdev_err(dev,
733				   "failed to send bitrate command 'C\\rS%d\\r'\n",
734				   s);
735			goto cmd_transmit_failed;
736		}
737
738		if (test_bit(CF_ERR_RST, &sl->cmd_flags)) {
739			err = slcan_transmit_cmd(sl, "F\r");
740			if (err) {
741				netdev_err(dev,
742					   "failed to send error command 'F\\r'\n");
743				goto cmd_transmit_failed;
744			}
745		}
746
747		if (sl->can.ctrlmode & CAN_CTRLMODE_LISTENONLY) {
748			err = slcan_transmit_cmd(sl, "L\r");
749			if (err) {
750				netdev_err(dev,
751					   "failed to send listen-only command 'L\\r'\n");
752				goto cmd_transmit_failed;
753			}
754		} else {
755			err = slcan_transmit_cmd(sl, "O\r");
756			if (err) {
757				netdev_err(dev,
758					   "failed to send open command 'O\\r'\n");
759				goto cmd_transmit_failed;
760			}
761		}
762	}
763
764	sl->can.state = CAN_STATE_ERROR_ACTIVE;
765	netif_start_queue(dev);
766	return 0;
767
768cmd_transmit_failed:
769	close_candev(dev);
770	return err;
771}
772
773static const struct net_device_ops slcan_netdev_ops = {
774	.ndo_open               = slcan_netdev_open,
775	.ndo_stop               = slcan_netdev_close,
776	.ndo_start_xmit         = slcan_netdev_xmit,
777};
778
779/******************************************
780 *  Routines looking at TTY side.
781 ******************************************/
782
783/* Handle the 'receiver data ready' interrupt.
784 * This function is called by the 'tty_io' module in the kernel when
785 * a block of SLCAN data has been received, which can now be decapsulated
786 * and sent on to some IP layer for further processing. This will not
787 * be re-entered while running but other ldisc functions may be called
788 * in parallel
789 */
790static void slcan_receive_buf(struct tty_struct *tty, const u8 *cp,
791			      const u8 *fp, size_t count)
792{
793	struct slcan *sl = tty->disc_data;
794
795	if (!netif_running(sl->dev))
796		return;
797
798	/* Read the characters out of the buffer */
799	while (count--) {
800		if (fp && *fp++) {
801			if (!test_and_set_bit(SLF_ERROR, &sl->flags))
802				sl->dev->stats.rx_errors++;
803			cp++;
804			continue;
805		}
806		slcan_unesc(sl, *cp++);
807	}
808}
809
810/* Open the high-level part of the SLCAN channel.
811 * This function is called by the TTY module when the
812 * SLCAN line discipline is called for.
813 *
814 * Called in process context serialized from other ldisc calls.
815 */
816static int slcan_open(struct tty_struct *tty)
817{
818	struct net_device *dev;
819	struct slcan *sl;
820	int err;
821
822	if (!capable(CAP_NET_ADMIN))
823		return -EPERM;
824
825	if (!tty->ops->write)
826		return -EOPNOTSUPP;
827
828	dev = alloc_candev(sizeof(*sl), 1);
829	if (!dev)
830		return -ENFILE;
831
832	sl = netdev_priv(dev);
833
834	/* Configure TTY interface */
835	tty->receive_room = 65536; /* We don't flow control */
836	sl->rcount = 0;
837	sl->xleft = 0;
838	spin_lock_init(&sl->lock);
839	INIT_WORK(&sl->tx_work, slcan_transmit);
840	init_waitqueue_head(&sl->xcmd_wait);
841
842	/* Configure CAN metadata */
843	sl->can.bitrate_const = slcan_bitrate_const;
844	sl->can.bitrate_const_cnt = ARRAY_SIZE(slcan_bitrate_const);
845	sl->can.ctrlmode_supported = CAN_CTRLMODE_LISTENONLY;
846
847	/* Configure netdev interface */
848	sl->dev	= dev;
849	dev->netdev_ops = &slcan_netdev_ops;
850	dev->ethtool_ops = &slcan_ethtool_ops;
851
852	/* Mark ldisc channel as alive */
853	sl->tty = tty;
854	tty->disc_data = sl;
855
856	err = register_candev(dev);
857	if (err) {
858		free_candev(dev);
859		pr_err("can't register candev\n");
860		return err;
861	}
862
863	netdev_info(dev, "slcan on %s.\n", tty->name);
864	/* TTY layer expects 0 on success */
865	return 0;
866}
867
868/* Close down a SLCAN channel.
869 * This means flushing out any pending queues, and then returning. This
870 * call is serialized against other ldisc functions.
871 * Once this is called, no other ldisc function of ours is entered.
872 *
873 * We also use this method for a hangup event.
874 */
875static void slcan_close(struct tty_struct *tty)
876{
877	struct slcan *sl = tty->disc_data;
878
879	unregister_candev(sl->dev);
880
881	/*
882	 * The netdev needn't be UP (so .ndo_stop() is not called). Hence make
883	 * sure this is not running before freeing it up.
884	 */
885	flush_work(&sl->tx_work);
886
887	/* Mark channel as dead */
888	spin_lock_bh(&sl->lock);
889	tty->disc_data = NULL;
890	sl->tty = NULL;
891	spin_unlock_bh(&sl->lock);
892
893	netdev_info(sl->dev, "slcan off %s.\n", tty->name);
894	free_candev(sl->dev);
895}
896
897/* Perform I/O control on an active SLCAN channel. */
898static int slcan_ioctl(struct tty_struct *tty, unsigned int cmd,
899		       unsigned long arg)
900{
901	struct slcan *sl = tty->disc_data;
902	unsigned int tmp;
903
904	switch (cmd) {
905	case SIOCGIFNAME:
906		tmp = strlen(sl->dev->name) + 1;
907		if (copy_to_user((void __user *)arg, sl->dev->name, tmp))
908			return -EFAULT;
909		return 0;
910
911	case SIOCSIFHWADDR:
912		return -EINVAL;
913
914	default:
915		return tty_mode_ioctl(tty, cmd, arg);
916	}
917}
918
919static struct tty_ldisc_ops slcan_ldisc = {
920	.owner		= THIS_MODULE,
921	.num		= N_SLCAN,
922	.name		= KBUILD_MODNAME,
923	.open		= slcan_open,
924	.close		= slcan_close,
925	.ioctl		= slcan_ioctl,
926	.receive_buf	= slcan_receive_buf,
927	.write_wakeup	= slcan_write_wakeup,
928};
929
930static int __init slcan_init(void)
931{
932	int status;
933
934	pr_info("serial line CAN interface driver\n");
935
936	/* Fill in our line protocol discipline, and register it */
937	status = tty_register_ldisc(&slcan_ldisc);
938	if (status)
939		pr_err("can't register line discipline\n");
940
941	return status;
942}
943
944static void __exit slcan_exit(void)
945{
946	/* This will only be called when all channels have been closed by
947	 * userspace - tty_ldisc.c takes care of the module's refcount.
948	 */
949	tty_unregister_ldisc(&slcan_ldisc);
950}
951
952module_init(slcan_init);
953module_exit(slcan_exit);