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,
69 ELM_TODO_CAN_CONFIG_PART2,
72 ELM_TODO_SILENT_MONITOR,
78 /* This must be the first member when using alloc_candev() */
81 /* TTY and netdev devices that we're bridging */
82 struct tty_struct *tty;
83 struct net_device *dev;
85 /* Per-channel lock */
88 /* Keep track of how many things are using this struct.
89 * Once it reaches 0, we are in the process of cleaning up,
90 * and new operations will be cancelled immediately.
91 * Use atomic_t rather than refcount_t because we deliberately
92 * decrement to 0, and refcount_dec() spills a WARN_ONCE in
97 /* Stop the channel on hardware failure.
98 * Once this is true, nothing will be sent to the TTY.
103 struct work_struct tx_work; /* Flushes TTY TX buffer */
104 unsigned char txbuf[32];
105 unsigned char *txhead; /* Pointer to next TX byte */
106 int txleft; /* Bytes left to TX */
109 unsigned char rxbuf[256];
122 /* The CAN frame and config the ELM327 is sending/using,
123 * or will send/use after finishing all cmds_todo */
124 struct can_frame can_frame;
125 unsigned short can_config;
126 unsigned long can_bitrate;
127 unsigned char can_bitrate_divisor;
128 int silent_monitoring;
130 /* Things we have yet to send */
131 char **next_init_cmd;
132 unsigned long cmds_todo;
136 /* A lock for all tty->disc_data handled by this ldisc.
137 * This is to prevent a case where tty->disc_data is set to NULL,
138 * yet someone is still trying to dereference it.
139 * Without this, we cannot do a clean shutdown.
141 static DEFINE_SPINLOCK(elmcan_discdata_lock);
144 static inline void elm327_hw_failure(struct elmcan *elm);
148 /************************************************************************
149 * ELM327: Transmission *
151 * (all functions assume elm->lock taken) *
152 ************************************************************************/
154 static void elm327_send(struct elmcan *elm, const void *buf, size_t len)
158 if (elm->hw_failure) {
162 memcpy(elm->txbuf, buf, len);
164 /* Order of next two lines is *very* important.
165 * When we are sending a little amount of data,
166 * the transfer may be completed inside the ops->write()
167 * routine, because it's running with interrupts enabled.
168 * In this case we *never* got WRITE_WAKEUP event,
169 * if we did not request it before write operation.
170 * 14 Oct 1994 Dmitry Gorodchanin.
172 set_bit(TTY_DO_WRITE_WAKEUP, &elm->tty->flags);
173 actual = elm->tty->ops->write(elm->tty, elm->txbuf, len);
175 netdev_err(elm->dev, "Failed to write to tty %s.\n", elm->tty->name);
176 elm327_hw_failure(elm);
180 elm->txleft = len - actual;
181 elm->txhead = elm->txbuf + actual;
186 * Take the ELM327 out of almost any state and back into command mode
188 * Assumes elm->lock taken.
190 static void elm327_kick_into_cmd_mode(struct elmcan *elm)
192 if (elm->state != ELM_GETMAGICCHAR && elm->state != ELM_GETPROMPT) {
193 elm327_send(elm, ELM327_MAGIC_STRING, 1);
195 elm->state = ELM_GETMAGICCHAR;
202 * Schedule a CAN frame, and any necessary config changes,
203 * to be sent down the TTY.
205 * Assumes elm->lock taken.
207 static void elm327_send_frame(struct elmcan *elm, struct can_frame *frame)
209 /* Schedule any necessary changes in ELM327's CAN configuration */
210 if (elm->can_frame.can_id != frame->can_id) {
211 /* Set the new CAN ID for transmission. */
212 if ((frame->can_id & CAN_EFF_FLAG) ^ (elm->can_frame.can_id & CAN_EFF_FLAG)) {
213 elm->can_config = (frame->can_id & CAN_EFF_FLAG ? 0 : ELM327_CAN_CONFIG_SEND_SFF)
214 | ELM327_CAN_CONFIG_VARIABLE_DLC
215 | ELM327_CAN_CONFIG_RECV_BOTH_SFF_EFF
216 | elm->can_bitrate_divisor;
218 set_bit(ELM_TODO_CAN_CONFIG, &elm->cmds_todo);
221 if (frame->can_id & CAN_EFF_FLAG) {
222 clear_bit(ELM_TODO_CANID_11BIT, &elm->cmds_todo);
223 set_bit(ELM_TODO_CANID_29BIT_LOW, &elm->cmds_todo);
224 set_bit(ELM_TODO_CANID_29BIT_HIGH, &elm->cmds_todo);
226 set_bit(ELM_TODO_CANID_11BIT, &elm->cmds_todo);
227 clear_bit(ELM_TODO_CANID_29BIT_LOW, &elm->cmds_todo);
228 clear_bit(ELM_TODO_CANID_29BIT_HIGH, &elm->cmds_todo);
232 /* Schedule the CAN frame itself. */
233 elm->can_frame = *frame;
234 set_bit(ELM_TODO_CAN_DATA, &elm->cmds_todo);
236 elm327_kick_into_cmd_mode(elm);
241 /************************************************************************
242 * ELM327: Initialization sequence *
244 * (assumes elm->lock taken) *
245 ************************************************************************/
247 static char *elm327_init_script[] = {
248 "AT WS\r", /* v1.0: Warm Start */
249 "AT PP FF OFF\r", /* v1.0: All Programmable Parameters Off */
250 "AT M0\r", /* v1.0: Memory Off */
251 "AT AL\r", /* v1.0: Allow Long messages */
252 "AT BI\r", /* v1.0: Bypass Initialization */
253 "AT CAF0\r", /* v1.0: CAN Auto Formatting Off */
254 "AT CFC0\r", /* v1.0: CAN Flow Control Off */
255 "AT CF 000\r", /* v1.0: Reset CAN ID Filter */
256 "AT CM 000\r", /* v1.0: Reset CAN ID Mask */
257 "AT E1\r", /* v1.0: Echo On */
258 "AT H1\r", /* v1.0: Headers On */
259 "AT L0\r", /* v1.0: Linefeeds Off */
260 "AT SH 7DF\r", /* v1.0: Set CAN sending ID to 0x7df */
261 "AT ST FF\r", /* v1.0: Set maximum Timeout for response after TX */
262 "AT AT0\r", /* v1.2: Adaptive Timing Off */
263 "AT D1\r", /* v1.3: Print DLC On */
264 "AT S1\r", /* v1.3: Spaces On */
265 "AT TP B\r", /* v1.0: Try Protocol B */
270 static void elm327_init(struct elmcan *elm)
272 elm->state = ELM_NOTINIT;
273 elm->can_frame.can_id = 0x7df;
275 elm->drop_next_line = 0;
277 /* We can only set the bitrate as a fraction of 500000.
278 * The bit timing constants in elmcan_bittiming_const will
279 * limit the user to the right values.
281 elm->can_bitrate_divisor = 500000 / elm->can.bittiming.bitrate;
282 elm->can_config = ELM327_CAN_CONFIG_SEND_SFF
283 | ELM327_CAN_CONFIG_VARIABLE_DLC
284 | ELM327_CAN_CONFIG_RECV_BOTH_SFF_EFF
285 | elm->can_bitrate_divisor;
287 /* Configure ELM327 and then start monitoring */
288 elm->next_init_cmd = &elm327_init_script[0];
289 set_bit(ELM_TODO_INIT, &elm->cmds_todo);
290 set_bit(ELM_TODO_SILENT_MONITOR, &elm->cmds_todo);
291 set_bit(ELM_TODO_RESPONSES, &elm->cmds_todo);
292 set_bit(ELM_TODO_CAN_CONFIG, &elm->cmds_todo);
294 elm327_kick_into_cmd_mode(elm);
299 /************************************************************************
300 * ELM327: Reception -> netdev glue *
302 * (assumes elm->lock taken) *
303 ************************************************************************/
305 static void elm327_feed_frame_to_netdev(struct elmcan *elm, const struct can_frame *frame)
307 struct can_frame *cf;
310 if (!netif_running(elm->dev)) {
314 skb = alloc_can_skb(elm->dev, &cf);
319 memcpy(cf, frame, sizeof(struct can_frame));
321 elm->dev->stats.rx_packets++;
322 elm->dev->stats.rx_bytes += frame->can_dlc;
325 can_led_event(elm->dev, CAN_LED_EVENT_RX);
330 /************************************************************************
331 * ELM327: "Panic" handler *
333 * (assumes elm->lock taken) *
334 ************************************************************************/
336 /* Called when we're out of ideas and just want it all to end. */
337 static inline void elm327_hw_failure(struct elmcan *elm)
339 struct can_frame frame;
341 memset(&frame, 0, sizeof(frame));
342 frame.can_id = CAN_ERR_FLAG;
343 frame.can_dlc = CAN_ERR_DLC;
347 elm327_feed_frame_to_netdev(elm, &frame);
349 netdev_err(elm->dev, "ELM327 misbehaved. "
350 "Blocking further communication.\n");
352 elm->hw_failure = true;
353 can_bus_off(elm->dev);
358 /************************************************************************
359 * ELM327: Reception parser *
361 * (assumes elm->lock taken) *
362 ************************************************************************/
364 static void elm327_parse_error(struct elmcan *elm, int len)
366 struct can_frame frame;
368 memset(&frame, 0, sizeof(frame));
369 frame.can_id = CAN_ERR_FLAG;
370 frame.can_dlc = CAN_ERR_DLC;
374 if (!memcmp(elm->rxbuf, "UNABLE TO CONNECT", 17)) {
375 netdev_err(elm->dev, "The ELM327 reported UNABLE TO CONNECT. Please check your setup.\n");
379 if (!memcmp(elm->rxbuf, "BUFFER FULL", 11)) {
380 /* This case will only happen if the last data
382 * Otherwise, elm327_parse_frame() will emit the
383 * error frame instead.
385 frame.can_id |= CAN_ERR_CRTL;
386 frame.data[1] = CAN_ERR_CRTL_RX_OVERFLOW;
390 if (!memcmp(elm->rxbuf, "BUS ERROR", 9)) {
391 frame.can_id |= CAN_ERR_BUSERROR;
393 if (!memcmp(elm->rxbuf, "CAN ERROR", 9)
394 || !memcmp(elm->rxbuf, "<RX ERROR", 9)) {
395 frame.can_id |= CAN_ERR_PROT;
399 if (!memcmp(elm->rxbuf, "BUS BUSY", 8)) {
400 frame.can_id |= CAN_ERR_PROT;
401 frame.data[2] = CAN_ERR_PROT_OVERLOAD;
403 if (!memcmp(elm->rxbuf, "FB ERROR", 8)) {
404 frame.can_id |= CAN_ERR_PROT;
405 frame.data[2] = CAN_ERR_PROT_TX;
409 if (!memcmp(elm->rxbuf, "ERR", 3)) {
410 netdev_err(elm->dev, "The ELM327 reported an ERR%c%c. Please power it off and on again.\n",
411 elm->rxbuf[3], elm->rxbuf[4]);
412 frame.can_id |= CAN_ERR_CRTL;
416 /* Don't emit an error frame if we're unsure */
420 elm327_feed_frame_to_netdev(elm, &frame);
424 static int elm327_parse_frame(struct elmcan *elm, int len)
426 struct can_frame frame;
431 memset(&frame, 0, sizeof(frame));
433 /* Find first non-hex and non-space character:
434 * - In the simplest case, there is none.
435 * - For RTR frames, 'R' is the first non-hex character.
436 * - An error message may replace the end of the data line.
438 for (hexlen = 0; hexlen <= len; hexlen++) {
439 if (hex_to_bin(elm->rxbuf[hexlen]) < 0
440 && elm->rxbuf[hexlen] != ' ') {
445 /* Use spaces in CAN ID to distinguish 29 or 11 bit address length.
446 * No out-of-bounds access:
447 * We use the fact that we can always read from elm->rxbuf.
449 if (elm->rxbuf[2] == ' ' && elm->rxbuf[5] == ' '
450 && elm->rxbuf[8] == ' ' && elm->rxbuf[11] == ' '
451 && elm->rxbuf[13] == ' ') {
452 frame.can_id = CAN_EFF_FLAG;
454 } else if (elm->rxbuf[3] == ' ' && elm->rxbuf[5] == ' ') {
458 /* This is not a well-formatted data line.
459 * Assume it's an error message.
464 if (hexlen < datastart) {
465 /* The line is too short to be a valid frame hex dump.
466 * Something interrupted the hex dump or it is invalid.
471 /* From here on all chars up to buf[hexlen] are hex or spaces,
472 * at well-defined offsets.
475 /* Read CAN data length */
476 frame.can_dlc = (hex_to_bin(elm->rxbuf[datastart - 2]) << 0);
479 if (frame.can_id & CAN_EFF_FLAG) {
480 frame.can_id |= (hex_to_bin(elm->rxbuf[0]) << 28)
481 | (hex_to_bin(elm->rxbuf[1]) << 24)
482 | (hex_to_bin(elm->rxbuf[3]) << 20)
483 | (hex_to_bin(elm->rxbuf[4]) << 16)
484 | (hex_to_bin(elm->rxbuf[6]) << 12)
485 | (hex_to_bin(elm->rxbuf[7]) << 8)
486 | (hex_to_bin(elm->rxbuf[9]) << 4)
487 | (hex_to_bin(elm->rxbuf[10]) << 0);
489 frame.can_id |= (hex_to_bin(elm->rxbuf[0]) << 8)
490 | (hex_to_bin(elm->rxbuf[1]) << 4)
491 | (hex_to_bin(elm->rxbuf[2]) << 0);
494 /* Check for RTR frame */
495 if (elm->rxfill >= hexlen + 3
496 && elm->rxbuf[hexlen + 0] == 'R'
497 && elm->rxbuf[hexlen + 1] == 'T'
498 && elm->rxbuf[hexlen + 2] == 'R') {
499 frame.can_id |= CAN_RTR_FLAG;
502 /* Is the line long enough to hold the advertised payload? */
503 if (!(frame.can_id & CAN_RTR_FLAG) && (hexlen < frame.can_dlc * 3 + datastart)) {
504 /* Incomplete frame. */
506 /* Probably the ELM327's RS232 TX buffer was full.
507 * Emit an error frame and exit.
509 frame.can_id = CAN_ERR_FLAG | CAN_ERR_CRTL;
510 frame.can_dlc = CAN_ERR_DLC;
511 frame.data[1] = CAN_ERR_CRTL_RX_OVERFLOW;
512 elm327_feed_frame_to_netdev(elm, &frame);
514 /* Signal failure to parse.
515 * The line will be re-parsed as an error line, which will fail.
516 * However, this will correctly drop the state machine back into
522 /* Parse the data nibbles. */
523 for (i = 0; i < frame.can_dlc; i++) {
524 frame.data[i] = (hex_to_bin(elm->rxbuf[datastart+3*i]) << 4)
525 | (hex_to_bin(elm->rxbuf[datastart+3*i+1]) << 0);
528 /* Feed the frame to the network layer. */
529 elm327_feed_frame_to_netdev(elm, &frame);
535 static void elm327_parse_line(struct elmcan *elm, int len)
537 /* Skip empty lines */
542 /* Skip echo lines */
543 if (elm->drop_next_line) {
544 elm->drop_next_line = 0;
546 } else if (elm->rxbuf[0] == 'A' && elm->rxbuf[1] == 'T') {
550 /* Regular parsing */
553 if (elm327_parse_frame(elm, len)) {
554 /* Parse an error line. */
555 elm327_parse_error(elm, len);
557 /* After the error line, we expect a prompt. */
558 elm->state = ELM_GETPROMPT;
567 static void elm327_handle_prompt(struct elmcan *elm)
569 if (elm->cmds_todo) {
570 struct can_frame *frame = &elm->can_frame;
571 char local_txbuf[20];
573 if (test_bit(ELM_TODO_INIT, &elm->cmds_todo)) {
574 elm327_send(elm, *elm->next_init_cmd, strlen(*elm->next_init_cmd));
575 elm->next_init_cmd++;
576 if (!(*elm->next_init_cmd)) {
577 clear_bit(ELM_TODO_INIT, &elm->cmds_todo);
578 netdev_info(elm->dev, "Initialization finished.\n");
581 /* Some chips are unreliable and need extra time after
582 * init commands, as seen with a clone.
583 * So let's do a dummy get-cmd-prompt dance.
585 elm->state = ELM_NOTINIT;
586 elm327_kick_into_cmd_mode(elm);
590 } else if (test_and_clear_bit(ELM_TODO_SILENT_MONITOR, &elm->cmds_todo)) {
591 sprintf(local_txbuf, "ATCSM%i\r",
592 !(!(elm->can.ctrlmode & CAN_CTRLMODE_LISTENONLY)));
594 } else if (test_and_clear_bit(ELM_TODO_RESPONSES, &elm->cmds_todo)) {
595 sprintf(local_txbuf, "ATR%i\r",
596 !(elm->can.ctrlmode & CAN_CTRLMODE_LISTENONLY));
598 } else if (test_and_clear_bit(ELM_TODO_CAN_CONFIG, &elm->cmds_todo)) {
599 sprintf(local_txbuf, "ATPC\r");
600 set_bit(ELM_TODO_CAN_CONFIG_PART2, &elm->cmds_todo);
602 } else if (test_and_clear_bit(ELM_TODO_CAN_CONFIG_PART2, &elm->cmds_todo)) {
603 sprintf(local_txbuf, "ATPB%04X\r",
606 } else if (test_and_clear_bit(ELM_TODO_CANID_29BIT_HIGH, &elm->cmds_todo)) {
607 sprintf(local_txbuf, "ATCP%02X\r",
608 (frame->can_id & CAN_EFF_MASK) >> 24);
610 } else if (test_and_clear_bit(ELM_TODO_CANID_29BIT_LOW, &elm->cmds_todo)) {
611 sprintf(local_txbuf, "ATSH%06X\r",
612 frame->can_id & CAN_EFF_MASK & ((1 << 24) - 1));
614 } else if (test_and_clear_bit(ELM_TODO_CANID_11BIT, &elm->cmds_todo)) {
615 sprintf(local_txbuf, "ATSH%03X\r",
616 frame->can_id & CAN_SFF_MASK);
618 } else if (test_and_clear_bit(ELM_TODO_CAN_DATA, &elm->cmds_todo)) {
619 if (frame->can_id & CAN_RTR_FLAG) {
620 /* Send an RTR frame. Their DLC is fixed.
621 * Some chips don't send them at all.
623 sprintf(local_txbuf, "ATRTR\r");
625 /* Send a regular CAN data frame */
628 for (i = 0; i < frame->can_dlc; i++) {
629 sprintf(&local_txbuf[2*i], "%02X",
633 sprintf(&local_txbuf[2*i], "\r");
636 elm->drop_next_line = 1;
637 elm->state = ELM_RECEIVING;
640 elm327_send(elm, local_txbuf, strlen(local_txbuf));
642 /* Enter CAN monitor mode */
643 elm327_send(elm, "ATMA\r", 5);
644 elm->state = ELM_RECEIVING;
649 static void elm327_drop_bytes(struct elmcan *elm, int i)
651 memmove(&elm->rxbuf[0], &elm->rxbuf[i], sizeof(elm->rxbuf) - i);
656 static void elm327_parse_rxbuf(struct elmcan *elm)
660 switch (elm->state) {
665 case ELM_GETMAGICCHAR:
667 /* Wait for 'y' or '>' */
670 for (i = 0; i < elm->rxfill; i++) {
671 if (elm->rxbuf[i] == ELM327_MAGIC_CHAR) {
672 elm327_send(elm, "\r", 1);
673 elm->state = ELM_GETPROMPT;
676 } else if (elm->rxbuf[i] == ELM327_READY_CHAR) {
677 elm327_send(elm, ELM327_MAGIC_STRING, 1);
683 elm327_drop_bytes(elm, i);
690 if (elm->rxbuf[elm->rxfill - 1] == ELM327_READY_CHAR) {
691 elm327_handle_prompt(elm);
698 /* Find <CR> delimiting feedback lines. */
700 (len < elm->rxfill) && (elm->rxbuf[len] != '\r');
705 if (len == sizeof(elm->rxbuf)) {
706 /* Line exceeds buffer. It's probably all garbage.
707 * Did we even connect at the right baud rate?
709 netdev_err(elm->dev, "RX buffer overflow. Faulty ELM327 connected?\n");
710 elm327_hw_failure(elm);
712 } else if (len == elm->rxfill) {
713 if (elm->state == ELM_RECEIVING
714 && elm->rxbuf[elm->rxfill - 1] == ELM327_READY_CHAR) {
715 /* The ELM327's AT ST response timeout ran out,
716 * so we got a prompt.
717 * Clear RX buffer and restart listening.
721 elm327_handle_prompt(elm);
724 /* We haven't received a full line yet.
725 * Wait for more data.
731 /* We have a full line to parse. */
732 elm327_parse_line(elm, len);
734 /* Remove parsed data from RX buffer. */
735 elm327_drop_bytes(elm, len+1);
737 /* More data to parse? */
739 elm327_parse_rxbuf(elm);
748 /************************************************************************
751 * (takes elm->lock) *
752 ************************************************************************/
754 /* Netdevice DOWN -> UP routine */
755 static int elmcan_netdev_open(struct net_device *dev)
757 struct elmcan *elm = netdev_priv(dev);
760 spin_lock_bh(&elm->lock);
761 if (elm->hw_failure) {
762 netdev_err(elm->dev, "Refusing to open interface after "
763 "a hardware fault has been detected.\n");
764 spin_unlock_bh(&elm->lock);
768 if (elm->tty == NULL) {
769 spin_unlock_bh(&elm->lock);
773 /* open_candev() checks for elm->can.bittiming.bitrate != 0 */
774 err = open_candev(dev);
776 spin_unlock_bh(&elm->lock);
780 /* Initialize the ELM327 */
782 spin_unlock_bh(&elm->lock);
784 can_led_event(dev, CAN_LED_EVENT_OPEN);
785 elm->can.state = CAN_STATE_ERROR_ACTIVE;
786 netif_start_queue(dev);
791 /* Netdevice UP -> DOWN routine */
792 static int elmcan_netdev_close(struct net_device *dev)
794 struct elmcan *elm = netdev_priv(dev);
796 spin_lock_bh(&elm->lock);
798 /* TTY discipline is running. */
800 /* Interrupt whatever we're doing right now */
801 elm327_send(elm, ELM327_MAGIC_STRING, 1);
803 /* Clear the wakeup bit, as the netdev will be down and thus
804 * the wakeup handler won't clear it
806 clear_bit(TTY_DO_WRITE_WAKEUP, &elm->tty->flags);
808 spin_unlock_bh(&elm->lock);
810 flush_work(&elm->tx_work);
812 spin_unlock_bh(&elm->lock);
815 elm->can.state = CAN_STATE_STOPPED;
816 netif_stop_queue(dev);
818 can_led_event(dev, CAN_LED_EVENT_STOP);
823 /* Send a can_frame to a TTY queue. */
824 static netdev_tx_t elmcan_netdev_start_xmit(struct sk_buff *skb, struct net_device *dev)
826 struct elmcan *elm = netdev_priv(dev);
827 struct can_frame *frame = (struct can_frame *) skb->data;
829 if (skb->len != sizeof(struct can_frame))
832 if (!netif_running(dev)) {
833 netdev_warn(elm->dev, "xmit: iface is down.\n");
837 /* BHs are already disabled, so no spin_lock_bh().
838 * See Documentation/networking/netdevices.txt
840 spin_lock(&elm->lock);
842 /* We shouldn't get here after a hardware fault:
843 * can_bus_off() calls netif_carrier_off()
845 BUG_ON(elm->hw_failure);
848 || elm->can.ctrlmode & CAN_CTRLMODE_LISTENONLY) {
849 spin_unlock(&elm->lock);
853 netif_stop_queue(dev);
855 elm327_send_frame(elm, frame);
856 spin_unlock(&elm->lock);
858 dev->stats.tx_packets++;
859 dev->stats.tx_bytes += frame->can_dlc;
861 can_led_event(dev, CAN_LED_EVENT_TX);
868 static int elmcan_netdev_change_mtu(struct net_device *dev, int new_mtu)
873 static const struct net_device_ops elmcan_netdev_ops = {
874 .ndo_open = elmcan_netdev_open,
875 .ndo_stop = elmcan_netdev_close,
876 .ndo_start_xmit = elmcan_netdev_start_xmit,
877 .ndo_change_mtu = elmcan_netdev_change_mtu,
884 /************************************************************************
887 * (takes elm->lock) *
888 ************************************************************************/
891 * Get a reference to our struct, taking into account locks/refcounts.
892 * This is to ensure ordering in case we are shutting down, and to ensure
893 * there is a refcount at all (because tty->disc_data may be NULL).
895 static struct elmcan* get_elm(struct tty_struct *tty)
900 /* Lock all elmcan TTYs, so tty->disc_data can't become NULL
901 * the moment before we increase the reference counter.
903 spin_lock_bh(&elmcan_discdata_lock);
904 elm = (struct elmcan *) tty->disc_data;
907 spin_unlock_bh(&elmcan_discdata_lock);
911 got_ref = atomic_inc_not_zero(&elm->refcount);
912 spin_unlock_bh(&elmcan_discdata_lock);
921 static void put_elm(struct elmcan *elm)
923 atomic_dec(&elm->refcount);
929 * Handle the 'receiver data ready' interrupt.
930 * This function is called by the 'tty_io' module in the kernel when
931 * a block of ELM327 CAN data has been received, which can now be parsed
932 * and sent on to some IP layer for further processing. This will not
933 * be re-entered while running but other ldisc functions may be called
936 static void elmcan_ldisc_rx(struct tty_struct *tty,
937 const unsigned char *cp, char *fp, int count)
939 struct elmcan *elm = get_elm(tty);
944 /* Read the characters out of the buffer */
945 while (count-- && elm->rxfill < sizeof(elm->rxbuf)) {
947 netdev_err(elm->dev, "Error in received character stream. Check your wiring.");
949 spin_lock_bh(&elm->lock);
950 elm327_hw_failure(elm);
951 spin_unlock_bh(&elm->lock);
957 elm->rxbuf[elm->rxfill++] = *cp;
963 netdev_err(elm->dev, "Receive buffer overflowed. Bad chip or wiring?");
965 spin_lock_bh(&elm->lock);
966 elm327_hw_failure(elm);
967 spin_unlock_bh(&elm->lock);
973 spin_lock_bh(&elm->lock);
974 elm327_parse_rxbuf(elm);
975 spin_unlock_bh(&elm->lock);
981 * Write out remaining transmit buffer.
982 * Scheduled when TTY is writable.
984 static void elmcan_ldisc_tx_worker(struct work_struct *work)
986 /* No need to use get_elm() here, as we'll always flush workers
987 * befory destroying the elmcan object.
989 struct elmcan *elm = container_of(work, struct elmcan, tx_work);
992 spin_lock_bh(&elm->lock);
993 if (elm->hw_failure) {
994 spin_unlock_bh(&elm->lock);
998 if (!elm->tty || !netif_running(elm->dev)) {
999 spin_unlock_bh(&elm->lock);
1003 if (elm->txleft <= 0) {
1004 /* Our TTY write buffer is empty:
1005 * We can start transmission of another packet
1007 clear_bit(TTY_DO_WRITE_WAKEUP, &elm->tty->flags);
1008 spin_unlock_bh(&elm->lock);
1009 netif_wake_queue(elm->dev);
1013 actual = elm->tty->ops->write(elm->tty, elm->txhead, elm->txleft);
1015 netdev_err(elm->dev, "Failed to write to tty %s.\n", elm->tty->name);
1016 elm327_hw_failure(elm);
1017 spin_unlock_bh(&elm->lock);
1021 elm->txleft -= actual;
1022 elm->txhead += actual;
1023 spin_unlock_bh(&elm->lock);
1028 * Called by the driver when there's room for more data.
1029 * Schedule the transmit.
1031 static void elmcan_ldisc_tx_wakeup(struct tty_struct *tty)
1033 struct elmcan *elm = get_elm(tty);
1038 schedule_work(&elm->tx_work);
1045 /* ELM327 can only handle bitrates that are integer divisors of 500 kHz,
1046 * or 7/8 of that. Divisors are 1 to 64.
1047 * Currently we don't implement support for 7/8 rates.
1049 static const u32 elmcan_bitrate_const[64] = {
1050 7812, 7936, 8064, 8196, 8333, 8474, 8620, 8771,
1051 8928, 9090, 9259, 9433, 9615, 9803, 10000, 10204,
1052 10416, 10638, 10869, 11111, 11363, 11627, 11904, 12195,
1053 12500, 12820, 13157, 13513, 13888, 14285, 14705, 15151,
1054 15625, 16129, 16666, 17241, 17857, 18518, 19230, 20000,
1055 20833, 21739, 22727, 23809, 25000, 26315, 27777, 29411,
1056 31250, 33333, 35714, 38461, 41666, 45454, 50000, 55555,
1057 62500, 71428, 83333, 100000, 125000, 166666, 250000, 500000
1060 /* Dummy function to claim we're changing the bitrate.
1061 * We actually do this when opening the net device.
1063 static int elmcan_do_set_bittiming(struct net_device *netdev)
1070 * Open the high-level part of the elmcan channel.
1071 * This function is called by the TTY module when the
1072 * elmcan line discipline is called for.
1074 * Called in process context serialized from other ldisc calls.
1076 static int elmcan_ldisc_open(struct tty_struct *tty)
1078 struct net_device *dev;
1082 if (!capable(CAP_NET_ADMIN))
1085 if (!tty->ops->write)
1089 /* OK. Find a free elmcan channel to use. */
1090 dev = alloc_candev(sizeof(struct elmcan), 0);
1093 elm = netdev_priv(dev);
1095 /* Configure TTY interface */
1096 tty->receive_room = 65536; /* We don't flow control */
1097 elm->txleft = 0; /* Clear TTY TX buffer */
1098 spin_lock_init(&elm->lock);
1099 atomic_set(&elm->refcount, 1);
1100 INIT_WORK(&elm->tx_work, elmcan_ldisc_tx_worker);
1102 /* Configure CAN metadata */
1103 elm->can.state = CAN_STATE_STOPPED;
1104 elm->can.bitrate_const = elmcan_bitrate_const;
1105 elm->can.bitrate_const_cnt = ARRAY_SIZE(elmcan_bitrate_const);
1106 elm->can.do_set_bittiming = elmcan_do_set_bittiming;
1107 elm->can.ctrlmode_supported = CAN_CTRLMODE_LISTENONLY;
1109 /* Configure netlink interface */
1111 dev->netdev_ops = &elmcan_netdev_ops;
1113 /* Mark ldisc channel as alive */
1115 tty->disc_data = elm;
1117 devm_can_led_init(elm->dev);
1120 err = register_candev(elm->dev);
1122 free_candev(elm->dev);
1126 netdev_info(elm->dev, "elmcan on %s.\n", tty->name);
1132 * Close down an elmcan channel.
1133 * This means flushing out any pending queues, and then returning.
1134 * This call is serialized against other ldisc functions:
1135 * Once this is called, no other ldisc function of ours is entered.
1137 * We also use this function for a hangup event.
1139 static void elmcan_ldisc_close(struct tty_struct *tty)
1141 /* Use get_elm() to synchronize against other users */
1142 struct elmcan *elm = get_elm(tty);
1147 /* Tear down network side.
1148 * unregister_netdev() calls .ndo_stop() so we don't have to.
1150 unregister_candev(elm->dev);
1152 /* Decrease the refcount twice, once for our own get_elm(),
1153 * and once to remove the count of 1 that we set in _open().
1154 * Once it reaches 0, we can safely destroy it.
1159 /* Spin until refcount reaches 0 */
1160 while(atomic_read(&elm->refcount) > 0)
1163 /* At this point, all ldisc calls to us will be no-ops.
1164 * Since the refcount is 0, they are bailing immediately.
1167 /* Mark channel as dead */
1168 spin_lock_bh(&elm->lock);
1169 tty->disc_data = NULL;
1171 spin_unlock_bh(&elm->lock);
1173 /* Flush TTY side */
1174 flush_work(&elm->tx_work);
1176 netdev_info(elm->dev, "elmcan off %s.\n", tty->name);
1178 /* Free our memory */
1179 free_candev(elm->dev);
1182 static int elmcan_ldisc_hangup(struct tty_struct *tty)
1184 elmcan_ldisc_close(tty);
1188 /* Perform I/O control on an active elmcan channel. */
1189 static int elmcan_ldisc_ioctl(struct tty_struct *tty, struct file *file,
1190 unsigned int cmd, unsigned long arg)
1192 struct elmcan *elm = get_elm(tty);
1200 tmp = strlen(elm->dev->name) + 1;
1201 if (copy_to_user((void __user *)arg, elm->dev->name, tmp)) {
1215 return tty_mode_ioctl(tty, file, cmd, arg);
1219 static struct tty_ldisc_ops elmcan_ldisc = {
1220 .owner = THIS_MODULE,
1221 .magic = TTY_LDISC_MAGIC,
1223 .receive_buf = elmcan_ldisc_rx,
1224 .write_wakeup = elmcan_ldisc_tx_wakeup,
1225 .open = elmcan_ldisc_open,
1226 .close = elmcan_ldisc_close,
1227 .hangup = elmcan_ldisc_hangup,
1228 .ioctl = elmcan_ldisc_ioctl,
1235 /************************************************************************
1236 * Module init/exit *
1237 ************************************************************************/
1239 static int __init elmcan_init(void)
1243 pr_info("ELM327 based best-effort CAN interface driver\n");
1244 pr_info("This device is severely limited as a CAN interface, see documentation.\n");
1246 /* Fill in our line protocol discipline, and register it */
1247 status = tty_register_ldisc(N_ELMCAN, &elmcan_ldisc);
1249 pr_err("can't register line discipline\n");
1254 static void __exit elmcan_exit(void)
1256 /* This will only be called when all channels have been closed by
1257 * userspace - tty_ldisc.c takes care of the module's refcount.
1261 status = tty_unregister_ldisc(N_ELMCAN);
1263 pr_err("Can't unregister line discipline (error: %d)\n", status);
1267 module_init(elmcan_init);
1268 module_exit(elmcan_exit);