2 * elmcan.c - ELM327 based CAN interface driver
3 * (tty line discipline)
5 * This file is derived from linux/drivers/net/can/slcan.c
7 * elmcan.c Author : Max Staudt <elmcan@enpas.org>
8 * slcan.c Author : Oliver Hartkopp <socketcan@hartkopp.net>
9 * slip.c Authors : Laurence Culhane <loz@holmes.demon.co.uk>
10 * Fred N. van Kempen <waltje@uwalt.nl.mugnet.org>
12 * SPDX-License-Identifier: GPL-2.0
16 #define pr_fmt(fmt) "[elmcan] " fmt
19 #include <linux/init.h>
20 #include <linux/module.h>
21 #include <linux/moduleparam.h>
23 #include <linux/atomic.h>
24 #include <linux/bitops.h>
25 #include <linux/delay.h>
26 #include <linux/errno.h>
27 #include <linux/if_ether.h>
28 #include <linux/kernel.h>
29 #include <linux/list.h>
30 #include <linux/netdevice.h>
31 #include <linux/skbuff.h>
32 #include <linux/spinlock.h>
33 #include <linux/string.h>
34 #include <linux/tty.h>
35 #include <linux/workqueue.h>
37 #include <linux/can.h>
38 #include <linux/can/dev.h>
39 #include <linux/can/error.h>
40 #include <linux/can/led.h>
43 MODULE_ALIAS_LDISC(N_ELMCAN);
44 MODULE_DESCRIPTION("ELM327 based CAN interface");
45 MODULE_LICENSE("GPL");
46 MODULE_AUTHOR("Max Staudt <max-linux@enpas.org>");
48 /* Line discipline ID number */
53 #define ELM327_CAN_CONFIG_SEND_SFF 0x8000
54 #define ELM327_CAN_CONFIG_VARIABLE_DLC 0x4000
55 #define ELM327_CAN_CONFIG_RECV_BOTH_SFF_EFF 0x2000
56 #define ELM327_CAN_CONFIG_BAUDRATE_MULT_8_7 0x1000
58 #define ELM327_MAGIC_CHAR 'y'
59 #define ELM327_MAGIC_STRING "y"
60 #define ELM327_READY_CHAR '>'
63 /* Bits in elm->cmds_todo */
65 ELM_TODO_CAN_DATA = 0,
67 ELM_TODO_CANID_29BIT_LOW,
68 ELM_TODO_CANID_29BIT_HIGH,
71 ELM_TODO_SILENT_MONITOR,
77 /* This must be the first member when using alloc_candev() */
80 /* TTY and netdev devices that we're bridging */
81 struct tty_struct *tty;
82 struct net_device *dev;
84 /* Per-channel lock */
87 /* Keep track of how many things are using this struct.
88 * Once it reaches 0, we are in the process of cleaning up,
89 * and new operations will be cancelled immediately.
90 * Use atomic_t rather than refcount_t because we deliberately
91 * decrement to 0, and refcount_dec() spills a WARN_ONCE in
97 struct work_struct tx_work; /* Flushes TTY TX buffer */
98 unsigned char txbuf[32];
99 unsigned char *txhead; /* Pointer to next TX byte */
100 int txleft; /* Bytes left to TX */
103 unsigned char rxbuf[256];
116 /* The CAN frame and config the ELM327 is sending/using,
117 * or will send/use after finishing all cmds_todo */
118 struct can_frame can_frame;
119 unsigned short can_config;
120 unsigned long can_bitrate;
121 unsigned char can_bitrate_divisor;
122 int silent_monitoring;
124 /* Things we have yet to send */
125 char **next_init_cmd;
126 unsigned long cmds_todo;
130 /* A lock for all tty->disc_data handled by this ldisc.
131 * This is to prevent a case where tty->disc_data is set to NULL,
132 * yet someone is still trying to dereference it.
133 * Without this, we cannot do a clean shutdown.
135 static DEFINE_SPINLOCK(elmcan_discdata_lock);
138 static inline void elm327_hw_failure(struct elmcan *elm);
142 /************************************************************************
143 * ELM327: Transmission *
145 * (all functions assume elm->lock taken) *
146 ************************************************************************/
148 static void elm327_send(struct elmcan *elm, const void *buf, size_t len)
152 memcpy(elm->txbuf, buf, len);
154 /* Order of next two lines is *very* important.
155 * When we are sending a little amount of data,
156 * the transfer may be completed inside the ops->write()
157 * routine, because it's running with interrupts enabled.
158 * In this case we *never* got WRITE_WAKEUP event,
159 * if we did not request it before write operation.
160 * 14 Oct 1994 Dmitry Gorodchanin.
162 set_bit(TTY_DO_WRITE_WAKEUP, &elm->tty->flags);
163 actual = elm->tty->ops->write(elm->tty, elm->txbuf, len);
165 netdev_err(elm->dev, "Failed to write to tty %s.\n", elm->tty->name);
166 elm327_hw_failure(elm);
169 elm->txleft = len - actual;
170 elm->txhead = elm->txbuf + actual;
175 * Take the ELM327 out of almost any state and back into command mode
177 * Assumes elm->lock taken.
179 static void elm327_kick_into_cmd_mode(struct elmcan *elm)
181 if (elm->state != ELM_GETMAGICCHAR && elm->state != ELM_GETPROMPT) {
182 elm327_send(elm, ELM327_MAGIC_STRING, 1);
184 elm->state = ELM_GETMAGICCHAR;
191 * Schedule a CAN frame, and any necessary config changes,
192 * to be sent down the TTY.
194 * Assumes elm->lock taken.
196 static void elm327_send_frame(struct elmcan *elm, struct can_frame *frame)
198 /* Schedule any necessary changes in ELM327's CAN configuration */
199 if (elm->can_frame.can_id != frame->can_id) {
200 /* Set the new CAN ID for transmission. */
201 if ((frame->can_id & CAN_EFF_FLAG) ^ (elm->can_frame.can_id & CAN_EFF_FLAG)) {
202 elm->can_config = (frame->can_id & CAN_EFF_FLAG ? 0 : ELM327_CAN_CONFIG_SEND_SFF)
203 | ELM327_CAN_CONFIG_VARIABLE_DLC
204 | ELM327_CAN_CONFIG_RECV_BOTH_SFF_EFF
205 | elm->can_bitrate_divisor;
207 set_bit(ELM_TODO_CAN_CONFIG, &elm->cmds_todo);
210 if (frame->can_id & CAN_EFF_FLAG) {
211 clear_bit(ELM_TODO_CANID_11BIT, &elm->cmds_todo);
212 set_bit(ELM_TODO_CANID_29BIT_LOW, &elm->cmds_todo);
213 set_bit(ELM_TODO_CANID_29BIT_HIGH, &elm->cmds_todo);
215 set_bit(ELM_TODO_CANID_11BIT, &elm->cmds_todo);
216 clear_bit(ELM_TODO_CANID_29BIT_LOW, &elm->cmds_todo);
217 clear_bit(ELM_TODO_CANID_29BIT_HIGH, &elm->cmds_todo);
221 /* Schedule the CAN frame itself. */
222 elm->can_frame = *frame;
223 set_bit(ELM_TODO_CAN_DATA, &elm->cmds_todo);
225 elm327_kick_into_cmd_mode(elm);
230 /************************************************************************
231 * ELM327: Initialization sequence *
233 * (assumes elm->lock taken) *
234 ************************************************************************/
236 static char *elm327_init_script[] = {
237 "AT WS\r", /* v1.0: Warm Start */
238 "AT PP FF OFF\r", /* v1.0: All Programmable Parameters Off */
239 "AT M0\r", /* v1.0: Memory Off */
240 "AT AL\r", /* v1.0: Allow Long messages */
241 "AT BI\r", /* v1.0: Bypass Initialization */
242 "AT CAF0\r", /* v1.0: CAN Auto Formatting Off */
243 "AT CFC0\r", /* v1.0: CAN Flow Control Off */
244 "AT CF 000\r", /* v1.0: Reset CAN ID Filter */
245 "AT CM 000\r", /* v1.0: Reset CAN ID Mask */
246 "AT E1\r", /* v1.0: Echo On */
247 "AT H1\r", /* v1.0: Headers On */
248 "AT L0\r", /* v1.0: Linefeeds Off */
249 "AT SH 7DF\r", /* v1.0: Set CAN sending ID to 0x7df */
250 "AT ST FF\r", /* v1.0: Set maximum Timeout for response after TX */
251 "AT AT0\r", /* v1.2: Adaptive Timing Off */
252 "AT D1\r", /* v1.3: Print DLC On */
253 "AT S1\r", /* v1.3: Spaces On */
254 "AT TP B\r", /* v1.0: Try Protocol B */
259 static void elm327_init(struct elmcan *elm)
261 elm->state = ELM_NOTINIT;
262 elm->can_frame.can_id = 0x7df;
264 elm->drop_next_line = 0;
266 /* We can only set the bitrate as a fraction of 500000.
267 * The bit timing constants in elmcan_bittiming_const will
268 * limit the user to the right values.
270 elm->can_bitrate_divisor = 500000 / elm->can.bittiming.bitrate;
271 elm->can_config = ELM327_CAN_CONFIG_SEND_SFF
272 | ELM327_CAN_CONFIG_VARIABLE_DLC
273 | ELM327_CAN_CONFIG_RECV_BOTH_SFF_EFF
274 | elm->can_bitrate_divisor;
276 /* Configure ELM327 and then start monitoring */
277 elm->next_init_cmd = &elm327_init_script[0];
278 set_bit(ELM_TODO_INIT, &elm->cmds_todo);
279 set_bit(ELM_TODO_SILENT_MONITOR, &elm->cmds_todo);
280 set_bit(ELM_TODO_RESPONSES, &elm->cmds_todo);
281 set_bit(ELM_TODO_CAN_CONFIG, &elm->cmds_todo);
283 elm327_kick_into_cmd_mode(elm);
288 /************************************************************************
289 * ELM327: Reception -> netdev glue *
291 * (assumes elm->lock taken) *
292 ************************************************************************/
294 static void elm327_feed_frame_to_netdev(struct elmcan *elm, const struct can_frame *frame)
296 struct can_frame *cf;
299 if (!netif_running(elm->dev)) {
303 skb = alloc_can_skb(elm->dev, &cf);
308 memcpy(cf, frame, sizeof(struct can_frame));
310 elm->dev->stats.rx_packets++;
311 elm->dev->stats.rx_bytes += frame->can_dlc;
314 can_led_event(elm->dev, CAN_LED_EVENT_RX);
319 /************************************************************************
320 * ELM327: "Panic" handler *
322 * (assumes elm->lock taken) *
323 ************************************************************************/
325 /* Called when we're out of ideas and just want it all to end. */
326 static inline void elm327_hw_failure(struct elmcan *elm)
328 struct can_frame frame = {0};
330 frame.can_id = CAN_ERR_FLAG | CAN_ERR_RESTARTED;
331 frame.can_dlc = CAN_ERR_DLC;
332 elm327_feed_frame_to_netdev(elm, &frame);
334 pr_err("ELM327 misbehaved. Re-initializing.\n");
336 elm->can.can_stats.restarts++;
342 /************************************************************************
343 * ELM327: Reception parser *
345 * (assumes elm->lock taken) *
346 ************************************************************************/
348 static void elm327_parse_error(struct elmcan *elm, int len)
350 struct can_frame frame = {0};
352 frame.can_id = CAN_ERR_FLAG;
353 frame.can_dlc = CAN_ERR_DLC;
357 if (!memcmp(elm->rxbuf, "UNABLE TO CONNECT", 17)) {
358 pr_err("The ELM327 reported UNABLE TO CONNECT. Please check your setup.\n");
362 if (!memcmp(elm->rxbuf, "BUFFER FULL", 11)) {
363 /* This case will only happen if the last data
365 * Otherwise, elm327_parse_frame() will emit the
366 * error frame instead.
368 frame.can_id |= CAN_ERR_CRTL;
369 frame.data[1] = CAN_ERR_CRTL_RX_OVERFLOW;
373 if (!memcmp(elm->rxbuf, "BUS ERROR", 9)) {
374 frame.can_id |= CAN_ERR_BUSERROR;
376 if (!memcmp(elm->rxbuf, "CAN ERROR", 9)
377 || !memcmp(elm->rxbuf, "<RX ERROR", 9)) {
378 frame.can_id |= CAN_ERR_PROT;
382 if (!memcmp(elm->rxbuf, "BUS BUSY", 8)) {
383 frame.can_id |= CAN_ERR_PROT;
384 frame.data[2] = CAN_ERR_PROT_OVERLOAD;
386 if (!memcmp(elm->rxbuf, "FB ERROR", 8)) {
387 frame.can_id |= CAN_ERR_PROT;
388 frame.data[2] = CAN_ERR_PROT_TX;
392 if (!memcmp(elm->rxbuf, "ERR", 3)) {
393 pr_err("The ELM327 reported an ERR%c%c. Please power it off and on again.\n",
394 elm->rxbuf[3], elm->rxbuf[4]);
395 frame.can_id |= CAN_ERR_CRTL;
399 /* Don't emit an error frame if we're unsure */
403 elm327_feed_frame_to_netdev(elm, &frame);
407 static int elm327_parse_frame(struct elmcan *elm, int len)
409 struct can_frame frame = {0};
414 /* Find first non-hex and non-space character:
415 * - In the simplest case, there is none.
416 * - For RTR frames, 'R' is the first non-hex character.
417 * - An error message may replace the end of the data line.
419 for (hexlen = 0; hexlen <= len; hexlen++) {
420 if (hex_to_bin(elm->rxbuf[hexlen]) < 0
421 && elm->rxbuf[hexlen] != ' ') {
426 /* Use spaces in CAN ID to distinguish 29 or 11 bit address length.
427 * No out-of-bounds access:
428 * We use the fact that we can always read from elm->rxbuf.
430 if (elm->rxbuf[2] == ' ' && elm->rxbuf[5] == ' '
431 && elm->rxbuf[8] == ' ' && elm->rxbuf[11] == ' '
432 && elm->rxbuf[13] == ' ') {
433 frame.can_id = CAN_EFF_FLAG;
435 } else if (elm->rxbuf[3] == ' ' && elm->rxbuf[5] == ' ') {
439 /* This is not a well-formatted data line.
440 * Assume it's an error message.
445 if (hexlen < datastart) {
446 /* The line is too short to be a valid frame hex dump.
447 * Something interrupted the hex dump or it is invalid.
452 /* From here on all chars up to buf[hexlen] are hex or spaces,
453 * at well-defined offsets.
456 /* Read CAN data length */
457 frame.can_dlc = (hex_to_bin(elm->rxbuf[datastart - 2]) << 0);
460 if (frame.can_id & CAN_EFF_FLAG) {
461 frame.can_id |= (hex_to_bin(elm->rxbuf[0]) << 28)
462 | (hex_to_bin(elm->rxbuf[1]) << 24)
463 | (hex_to_bin(elm->rxbuf[3]) << 20)
464 | (hex_to_bin(elm->rxbuf[4]) << 16)
465 | (hex_to_bin(elm->rxbuf[6]) << 12)
466 | (hex_to_bin(elm->rxbuf[7]) << 8)
467 | (hex_to_bin(elm->rxbuf[9]) << 4)
468 | (hex_to_bin(elm->rxbuf[10]) << 0);
470 frame.can_id |= (hex_to_bin(elm->rxbuf[0]) << 8)
471 | (hex_to_bin(elm->rxbuf[1]) << 4)
472 | (hex_to_bin(elm->rxbuf[2]) << 0);
475 /* Check for RTR frame */
476 if (elm->rxfill >= hexlen + 3
477 && elm->rxbuf[hexlen + 0] == 'R'
478 && elm->rxbuf[hexlen + 1] == 'T'
479 && elm->rxbuf[hexlen + 2] == 'R') {
480 frame.can_id |= CAN_RTR_FLAG;
483 /* Is the line long enough to hold the advertised payload? */
484 if (!(frame.can_id & CAN_RTR_FLAG) && (hexlen < frame.can_dlc * 3 + datastart)) {
485 /* Incomplete frame. */
487 /* Probably the ELM327's RS232 TX buffer was full.
488 * Emit an error frame and exit.
490 frame.can_id = CAN_ERR_FLAG | CAN_ERR_CRTL;
491 frame.can_dlc = CAN_ERR_DLC;
492 frame.data[1] = CAN_ERR_CRTL_RX_OVERFLOW;
493 elm327_feed_frame_to_netdev(elm, &frame);
495 /* Signal failure to parse.
496 * The line will be re-parsed as an error line, which will fail.
497 * However, this will correctly drop the state machine back into
503 /* Parse the data nibbles. */
504 for (i = 0; i < frame.can_dlc; i++) {
505 frame.data[i] = (hex_to_bin(elm->rxbuf[datastart+3*i]) << 4)
506 | (hex_to_bin(elm->rxbuf[datastart+3*i+1]) << 0);
509 /* Feed the frame to the network layer. */
510 elm327_feed_frame_to_netdev(elm, &frame);
516 static void elm327_parse_line(struct elmcan *elm, int len)
518 /* Skip empty lines */
523 /* Skip echo lines */
524 if (elm->drop_next_line) {
525 elm->drop_next_line = 0;
527 } else if (elm->rxbuf[0] == 'A' && elm->rxbuf[1] == 'T') {
531 /* Regular parsing */
534 if (elm327_parse_frame(elm, len)) {
535 /* Parse an error line. */
536 elm327_parse_error(elm, len);
538 /* After the error line, we expect a prompt. */
539 elm->state = ELM_GETPROMPT;
548 static void elm327_handle_prompt(struct elmcan *elm)
550 if (elm->cmds_todo) {
551 struct can_frame *frame = &elm->can_frame;
554 if (test_bit(ELM_TODO_INIT, &elm->cmds_todo)) {
555 elm327_send(elm, *elm->next_init_cmd, strlen(*elm->next_init_cmd));
556 elm->next_init_cmd++;
557 if (!(*elm->next_init_cmd)) {
558 clear_bit(ELM_TODO_INIT, &elm->cmds_todo);
559 netdev_info(elm->dev, "Initialization finished.\n");
562 /* Some chips are unreliable and need extra time after
563 * init commands, as seen with a clone.
564 * So let's do a dummy get-cmd-prompt dance.
566 elm->state = ELM_NOTINIT;
567 elm327_kick_into_cmd_mode(elm);
568 } else if (test_and_clear_bit(ELM_TODO_SILENT_MONITOR, &elm->cmds_todo)) {
569 snprintf(txbuf, sizeof(txbuf), "ATCSM%i\r", !(!(elm->can.ctrlmode & CAN_CTRLMODE_LISTENONLY)));
570 } else if (test_and_clear_bit(ELM_TODO_RESPONSES, &elm->cmds_todo)) {
571 snprintf(txbuf, sizeof(txbuf), "ATR%i\r", !(elm->can.ctrlmode & CAN_CTRLMODE_LISTENONLY));
572 } else if (test_and_clear_bit(ELM_TODO_CAN_CONFIG, &elm->cmds_todo)) {
573 snprintf(txbuf, sizeof(txbuf), "ATPB%04X\r", elm->can_config);
574 } else if (test_and_clear_bit(ELM_TODO_CANID_29BIT_HIGH, &elm->cmds_todo)) {
575 snprintf(txbuf, sizeof(txbuf), "ATCP%02X\r", (frame->can_id & CAN_EFF_MASK) >> 24);
576 } else if (test_and_clear_bit(ELM_TODO_CANID_29BIT_LOW, &elm->cmds_todo)) {
577 snprintf(txbuf, sizeof(txbuf), "ATSH%06X\r", frame->can_id & CAN_EFF_MASK & ((1 << 24) - 1));
578 } else if (test_and_clear_bit(ELM_TODO_CANID_11BIT, &elm->cmds_todo)) {
579 snprintf(txbuf, sizeof(txbuf), "ATSH%03X\r", frame->can_id & CAN_SFF_MASK);
580 } else if (test_and_clear_bit(ELM_TODO_CAN_DATA, &elm->cmds_todo)) {
581 if (frame->can_id & CAN_RTR_FLAG) {
582 snprintf(txbuf, sizeof(txbuf), "ATRTR\r");
586 for (i = 0; i < frame->can_dlc; i++) {
587 sprintf(&txbuf[2*i], "%02X", frame->data[i]);
590 sprintf(&txbuf[2*i], "\r");
593 elm->drop_next_line = 1;
594 elm->state = ELM_RECEIVING;
597 elm327_send(elm, txbuf, strlen(txbuf));
599 /* Enter CAN monitor mode */
600 elm327_send(elm, "ATMA\r", 5);
601 elm->state = ELM_RECEIVING;
606 static void elm327_drop_bytes(struct elmcan *elm, int i)
608 memmove(&elm->rxbuf[0], &elm->rxbuf[i], sizeof(elm->rxbuf) - i);
613 static void elm327_parse_rxbuf(struct elmcan *elm)
617 switch (elm->state) {
622 case ELM_GETMAGICCHAR:
624 /* Wait for 'y' or '>' */
627 for (i = 0; i < elm->rxfill; i++) {
628 if (elm->rxbuf[i] == ELM327_MAGIC_CHAR) {
629 elm327_send(elm, "\r", 1);
630 elm->state = ELM_GETPROMPT;
633 } else if (elm->rxbuf[i] == ELM327_READY_CHAR) {
634 elm327_send(elm, ELM327_MAGIC_STRING, 1);
640 elm327_drop_bytes(elm, i);
647 if (elm->rxbuf[elm->rxfill - 1] == ELM327_READY_CHAR) {
648 elm327_handle_prompt(elm);
655 /* Find <CR> delimiting feedback lines. */
657 (len < elm->rxfill) && (elm->rxbuf[len] != '\r');
662 if (len == sizeof(elm->rxbuf)) {
663 /* Line exceeds buffer. It's probably all garbage.
664 * Did we even connect at the right baud rate?
666 pr_err("RX buffer overflow. Faulty ELM327 connected?\n");
667 elm327_hw_failure(elm);
668 } else if (len == elm->rxfill) {
669 if (elm->state == ELM_RECEIVING
670 && elm->rxbuf[elm->rxfill - 1] == ELM327_READY_CHAR) {
671 /* The ELM327's AT ST response timeout ran out,
672 * so we got a prompt.
673 * Clear RX buffer and restart listening.
677 elm327_handle_prompt(elm);
680 /* We haven't received a full line yet.
681 * Wait for more data.
687 /* We have a full line to parse. */
688 elm327_parse_line(elm, len);
690 /* Remove parsed data from RX buffer. */
691 elm327_drop_bytes(elm, len+1);
693 /* More data to parse? */
695 elm327_parse_rxbuf(elm);
704 /************************************************************************
707 * (takes elm->lock) *
708 ************************************************************************/
710 /* Netdevice DOWN -> UP routine */
711 static int elmcan_netdev_open(struct net_device *dev)
713 struct elmcan *elm = netdev_priv(dev);
716 spin_lock_bh(&elm->lock);
717 if (elm->tty == NULL) {
718 spin_unlock_bh(&elm->lock);
722 /* open_candev() checks for elm->can.bittiming.bitrate != 0 */
723 err = open_candev(dev);
725 spin_unlock_bh(&elm->lock);
729 /* Initialize the ELM327 */
731 spin_unlock_bh(&elm->lock);
733 can_led_event(dev, CAN_LED_EVENT_OPEN);
734 elm->can.state = CAN_STATE_ERROR_ACTIVE;
735 netif_start_queue(dev);
740 /* Netdevice UP -> DOWN routine */
741 static int elmcan_netdev_close(struct net_device *dev)
743 struct elmcan *elm = netdev_priv(dev);
745 spin_lock_bh(&elm->lock);
747 /* TTY discipline is running. */
749 /* Interrupt whatever we're doing right now */
750 elm327_send(elm, ELM327_MAGIC_STRING, 1);
752 /* Clear the wakeup bit, as the netdev will be down and thus
753 * the wakeup handler won't clear it
755 clear_bit(TTY_DO_WRITE_WAKEUP, &elm->tty->flags);
757 spin_unlock_bh(&elm->lock);
759 flush_work(&elm->tx_work);
761 spin_unlock_bh(&elm->lock);
764 elm->can.state = CAN_STATE_STOPPED;
765 netif_stop_queue(dev);
767 can_led_event(dev, CAN_LED_EVENT_STOP);
772 /* Send a can_frame to a TTY queue. */
773 static netdev_tx_t elmcan_netdev_start_xmit(struct sk_buff *skb, struct net_device *dev)
775 struct elmcan *elm = netdev_priv(dev);
776 struct can_frame *frame = (struct can_frame *) skb->data;
778 if (skb->len != sizeof(struct can_frame))
781 if (!netif_running(dev)) {
782 netdev_warn(elm->dev, "xmit: iface is down.\n");
786 /* BHs are already disabled, so no spin_lock_bh().
787 * See Documentation/networking/netdevices.txt
789 spin_lock(&elm->lock);
791 || elm->can.ctrlmode & CAN_CTRLMODE_LISTENONLY) {
792 spin_unlock(&elm->lock);
796 netif_stop_queue(dev);
798 elm327_send_frame(elm, frame);
799 spin_unlock(&elm->lock);
801 dev->stats.tx_packets++;
802 dev->stats.tx_bytes += frame->can_dlc;
804 can_led_event(dev, CAN_LED_EVENT_TX);
811 static int elmcan_netdev_change_mtu(struct net_device *dev, int new_mtu)
816 static const struct net_device_ops elmcan_netdev_ops = {
817 .ndo_open = elmcan_netdev_open,
818 .ndo_stop = elmcan_netdev_close,
819 .ndo_start_xmit = elmcan_netdev_start_xmit,
820 .ndo_change_mtu = elmcan_netdev_change_mtu,
827 /************************************************************************
830 * (takes elm->lock) *
831 ************************************************************************/
834 * Get a reference to our struct, taking into account locks/refcounts.
835 * This is to ensure ordering in case we are shutting down, and to ensure
836 * there is a refcount at all (because tty->disc_data may be NULL).
838 static struct elmcan* get_elm(struct tty_struct *tty)
843 /* Lock all elmcan TTYs, so tty->disc_data can't become NULL
844 * the moment before we increase the reference counter.
846 spin_lock_bh(&elmcan_discdata_lock);
847 elm = (struct elmcan *) tty->disc_data;
850 spin_unlock_bh(&elmcan_discdata_lock);
854 got_ref = atomic_inc_not_zero(&elm->refcount);
855 spin_unlock_bh(&elmcan_discdata_lock);
864 static void put_elm(struct elmcan *elm)
866 atomic_dec(&elm->refcount);
872 * Handle the 'receiver data ready' interrupt.
873 * This function is called by the 'tty_io' module in the kernel when
874 * a block of ELM327 CAN data has been received, which can now be parsed
875 * and sent on to some IP layer for further processing. This will not
876 * be re-entered while running but other ldisc functions may be called
879 static void elmcan_ldisc_rx(struct tty_struct *tty,
880 const unsigned char *cp, char *fp, int count)
882 struct elmcan *elm = get_elm(tty);
887 /* Read the characters out of the buffer */
888 while (count-- && elm->rxfill < sizeof(elm->rxbuf)) {
890 pr_err("Error in received character stream. Check your wiring.");
892 spin_lock_bh(&elm->lock);
893 elm327_hw_failure(elm);
894 spin_unlock_bh(&elm->lock);
900 elm->rxbuf[elm->rxfill++] = *cp;
906 pr_err("Receive buffer overflowed. Bad chip or wiring?");
908 spin_lock_bh(&elm->lock);
909 elm327_hw_failure(elm);
910 spin_unlock_bh(&elm->lock);
916 spin_lock_bh(&elm->lock);
917 elm327_parse_rxbuf(elm);
918 spin_unlock_bh(&elm->lock);
924 * Write out remaining transmit buffer.
925 * Scheduled when TTY is writable.
927 static void elmcan_ldisc_tx_worker(struct work_struct *work)
929 /* No need to use get_elm() here, as we'll always flush workers
930 * befory destroying the elmcan object.
932 struct elmcan *elm = container_of(work, struct elmcan, tx_work);
935 spin_lock_bh(&elm->lock);
936 /* First make sure we're connected. */
937 if (!elm->tty || !netif_running(elm->dev)) {
938 spin_unlock_bh(&elm->lock);
942 if (elm->txleft <= 0) {
943 /* Our TTY write buffer is empty:
944 * We can start transmission of another packet
946 clear_bit(TTY_DO_WRITE_WAKEUP, &elm->tty->flags);
947 spin_unlock_bh(&elm->lock);
948 netif_wake_queue(elm->dev);
952 actual = elm->tty->ops->write(elm->tty, elm->txhead, elm->txleft);
954 netdev_err(elm->dev, "Failed to write to tty %s.\n", elm->tty->name);
955 elm327_hw_failure(elm);
958 elm->txleft -= actual;
959 elm->txhead += actual;
960 spin_unlock_bh(&elm->lock);
965 * Called by the driver when there's room for more data.
966 * Schedule the transmit.
968 static void elmcan_ldisc_tx_wakeup(struct tty_struct *tty)
970 struct elmcan *elm = get_elm(tty);
975 schedule_work(&elm->tx_work);
982 /* Some fake bit timings to allow bitrate setting */
983 static const struct can_bittiming_const elmcan_bittiming_const = {
996 * Open the high-level part of the elmcan channel.
997 * This function is called by the TTY module when the
998 * elmcan line discipline is called for.
1000 * Called in process context serialized from other ldisc calls.
1002 static int elmcan_ldisc_open(struct tty_struct *tty)
1004 struct net_device *dev;
1008 if (!capable(CAP_NET_ADMIN))
1011 if (!tty->ops->write)
1015 /* OK. Find a free elmcan channel to use. */
1016 dev = alloc_candev(sizeof(struct elmcan), 0);
1019 elm = netdev_priv(dev);
1021 /* Configure TTY interface */
1022 tty->receive_room = 65536; /* We don't flow control */
1023 elm->txleft = 0; /* Clear TTY TX buffer */
1024 spin_lock_init(&elm->lock);
1025 atomic_set(&elm->refcount, 1);
1026 INIT_WORK(&elm->tx_work, elmcan_ldisc_tx_worker);
1028 /* Configure CAN metadata */
1029 elm->can.state = CAN_STATE_STOPPED;
1030 elm->can.clock.freq = 1000000;
1031 elm->can.bittiming_const = &elmcan_bittiming_const;
1032 elm->can.ctrlmode_supported = CAN_CTRLMODE_LISTENONLY;
1034 /* Configure netlink interface */
1036 dev->netdev_ops = &elmcan_netdev_ops;
1038 /* Mark ldisc channel as alive */
1040 tty->disc_data = elm;
1042 devm_can_led_init(elm->dev);
1045 err = register_candev(elm->dev);
1047 free_candev(elm->dev);
1051 netdev_info(elm->dev, "elmcan on %s.\n", tty->name);
1057 * Close down an elmcan channel.
1058 * This means flushing out any pending queues, and then returning.
1059 * This call is serialized against other ldisc functions:
1060 * Once this is called, no other ldisc function of ours is entered.
1062 * We also use this function for a hangup event.
1064 static void elmcan_ldisc_close(struct tty_struct *tty)
1066 /* Use get_elm() to synchronize against other users */
1067 struct elmcan *elm = get_elm(tty);
1072 /* Tear down network side.
1073 * unregister_netdev() calls .ndo_stop() so we don't have to.
1075 unregister_candev(elm->dev);
1077 /* Decrease the refcount twice, once for our own get_elm(),
1078 * and once to remove the count of 1 that we set in _open().
1079 * Once it reaches 0, we can safely destroy it.
1084 /* Spin until refcount reaches 0 */
1085 while(atomic_read(&elm->refcount) > 0)
1088 /* At this point, all ldisc calls to us will be no-ops.
1089 * Since the refcount is 0, they are bailing immediately.
1092 /* Mark channel as dead */
1093 spin_lock_bh(&elm->lock);
1094 tty->disc_data = NULL;
1096 spin_unlock_bh(&elm->lock);
1098 /* Flush TTY side */
1099 flush_work(&elm->tx_work);
1101 netdev_info(elm->dev, "elmcan off %s.\n", tty->name);
1103 /* Free our memory */
1104 free_candev(elm->dev);
1107 static int elmcan_ldisc_hangup(struct tty_struct *tty)
1109 elmcan_ldisc_close(tty);
1113 /* Perform I/O control on an active elmcan channel. */
1114 static int elmcan_ldisc_ioctl(struct tty_struct *tty, struct file *file,
1115 unsigned int cmd, unsigned long arg)
1117 struct elmcan *elm = get_elm(tty);
1120 /* First make sure we're connected. */
1126 tmp = strlen(elm->dev->name) + 1;
1127 if (copy_to_user((void __user *)arg, elm->dev->name, tmp)) {
1141 return tty_mode_ioctl(tty, file, cmd, arg);
1145 static struct tty_ldisc_ops elmcan_ldisc = {
1146 .owner = THIS_MODULE,
1147 .magic = TTY_LDISC_MAGIC,
1149 .receive_buf = elmcan_ldisc_rx,
1150 .write_wakeup = elmcan_ldisc_tx_wakeup,
1151 .open = elmcan_ldisc_open,
1152 .close = elmcan_ldisc_close,
1153 .hangup = elmcan_ldisc_hangup,
1154 .ioctl = elmcan_ldisc_ioctl,
1161 /************************************************************************
1162 * Module init/exit *
1163 ************************************************************************/
1165 static int __init elmcan_init(void)
1169 pr_info("ELM327 based best-effort CAN interface driver\n");
1170 pr_info("This device is severely limited as a CAN interface, see documentation.\n");
1172 /* Fill in our line protocol discipline, and register it */
1173 status = tty_register_ldisc(N_ELMCAN, &elmcan_ldisc);
1175 pr_err("can't register line discipline\n");
1180 static void __exit elmcan_exit(void)
1182 /* This will only be called when all channels have been closed by
1183 * userspace - tty_ldisc.c takes care of the module's refcount.
1187 status = tty_unregister_ldisc(N_ELMCAN);
1189 pr_err("Can't unregister line discipline (error: %d)\n", status);
1193 module_init(elmcan_init);
1194 module_exit(elmcan_exit);