1 // SPDX-License-Identifier: GPL-2.0
2 /* ELM327 based CAN interface driver (tty line discipline)
4 * This driver started as a derivative of linux/drivers/net/can/slcan.c
5 * and my thanks go to the original authors for their inspiration, even
6 * after almost none of their code is left.
9 #define pr_fmt(fmt) "[elmcan] " fmt
11 #include <linux/init.h>
12 #include <linux/module.h>
13 #include <linux/moduleparam.h>
15 #include <linux/atomic.h>
16 #include <linux/bitops.h>
17 #include <linux/ctype.h>
18 #include <linux/delay.h>
19 #include <linux/errno.h>
20 #include <linux/if_ether.h>
21 #include <linux/kernel.h>
22 #include <linux/list.h>
23 #include <linux/netdevice.h>
24 #include <linux/skbuff.h>
25 #include <linux/spinlock.h>
26 #include <linux/string.h>
27 #include <linux/tty.h>
28 #include <linux/tty_ldisc.h>
29 #include <linux/version.h>
30 #include <linux/workqueue.h>
32 #include <uapi/linux/tty.h>
34 #include <linux/can.h>
35 #include <linux/can/dev.h>
36 #include <linux/can/error.h>
37 #include <linux/can/led.h>
38 #include <linux/can/rx-offload.h>
40 MODULE_ALIAS_LDISC(N_DEVELOPMENT);
41 MODULE_DESCRIPTION("ELM327 based CAN interface");
42 MODULE_LICENSE("GPL");
43 MODULE_AUTHOR("Max Staudt <max-linux@enpas.org>");
45 /* Line discipline ID number.
46 * N_DEVELOPMENT will likely be defined from Linux 5.18 onwards:
47 * https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty.git/commit/?h=tty-next&id=c2faf737abfb10f88f2d2612d573e9edc3c42c37
50 #define N_DEVELOPMENT 29
53 #define ELM327_NAPI_WEIGHT 4
55 #define ELM327_SIZE_RXBUF 256
56 #define ELM327_SIZE_TXBUF 32
58 #define ELM327_CAN_CONFIG_SEND_SFF 0x8000
59 #define ELM327_CAN_CONFIG_VARIABLE_DLC 0x4000
60 #define ELM327_CAN_CONFIG_RECV_BOTH_SFF_EFF 0x2000
61 #define ELM327_CAN_CONFIG_BAUDRATE_MULT_8_7 0x1000
63 #define ELM327_MAGIC_CHAR 'y'
64 #define ELM327_MAGIC_STRING "y"
65 #define ELM327_READY_CHAR '>'
67 /* Bits in elm->cmds_todo */
72 TODO_CANID_29BIT_HIGH,
73 TODO_CAN_CONFIG_PART2,
81 /* This must be the first member when using alloc_candev() */
84 struct can_rx_offload offload;
86 /* TTY and netdev devices that we're bridging */
87 struct tty_struct *tty;
88 struct net_device *dev;
90 /* Per-channel lock */
93 /* Keep track of how many things are using this struct.
94 * Once it reaches 0, we are in the process of cleaning up,
95 * and new operations will be cancelled immediately.
96 * Use atomic_t rather than refcount_t because we deliberately
97 * decrement to 0, and refcount_dec() spills a WARN_ONCE in
102 /* Stop the channel on hardware failure.
103 * Once this is true, nothing will be sent to the TTY.
108 struct work_struct tx_work; /* Flushes TTY TX buffer */
109 unsigned char *txbuf;
110 unsigned char *txhead; /* Pointer to next TX byte */
111 int txleft; /* Bytes left to TX */
114 unsigned char rxbuf[ELM327_SIZE_RXBUF];
127 /* The CAN frame and config the ELM327 is sending/using,
128 * or will send/use after finishing all cmds_todo
130 struct can_frame can_frame;
131 unsigned short can_config;
132 unsigned long can_bitrate;
133 unsigned char can_bitrate_divisor;
134 int silent_monitoring;
136 /* Things we have yet to send */
137 char **next_init_cmd;
138 unsigned long cmds_todo;
141 /* A lock for all tty->disc_data handled by this ldisc.
142 * This is to prevent a case where tty->disc_data is set to NULL,
143 * yet someone is still trying to dereference it.
144 * Without this, we cannot do a clean shutdown.
146 static DEFINE_SPINLOCK(elmcan_discdata_lock);
148 static inline void elm327_hw_failure(struct elmcan *elm);
150 /* Assumes elm->lock taken. */
151 static void elm327_send(struct elmcan *elm, const void *buf, size_t len)
158 memcpy(elm->txbuf, buf, len);
160 /* Order of next two lines is *very* important.
161 * When we are sending a little amount of data,
162 * the transfer may be completed inside the ops->write()
163 * routine, because it's running with interrupts enabled.
164 * In this case we *never* got WRITE_WAKEUP event,
165 * if we did not request it before write operation.
166 * 14 Oct 1994 Dmitry Gorodchanin.
168 set_bit(TTY_DO_WRITE_WAKEUP, &elm->tty->flags);
169 actual = elm->tty->ops->write(elm->tty, elm->txbuf, len);
172 "Failed to write to tty %s.\n",
174 elm327_hw_failure(elm);
178 elm->txleft = len - actual;
179 elm->txhead = elm->txbuf + actual;
182 /* Take the ELM327 out of almost any state and back into command mode.
183 * We send ELM327_MAGIC_CHAR which will either abort any running
184 * operation, or be echoed back to us in case we're already in command
187 * Assumes elm->lock taken.
189 static void elm327_kick_into_cmd_mode(struct elmcan *elm)
191 if (elm->state != ELM_GETMAGICCHAR && elm->state != ELM_GETPROMPT) {
192 elm327_send(elm, ELM327_MAGIC_STRING, 1);
194 elm->state = ELM_GETMAGICCHAR;
198 /* Schedule a CAN frame and necessary config changes to be sent to the TTY.
200 * Assumes elm->lock taken.
202 static void elm327_send_frame(struct elmcan *elm, struct can_frame *frame)
204 /* Schedule any necessary changes in ELM327's CAN configuration */
205 if (elm->can_frame.can_id != frame->can_id) {
206 /* Set the new CAN ID for transmission. */
207 if ((frame->can_id & CAN_EFF_FLAG)
208 ^ (elm->can_frame.can_id & CAN_EFF_FLAG)) {
209 elm->can_config = (frame->can_id & CAN_EFF_FLAG
211 : ELM327_CAN_CONFIG_SEND_SFF)
212 | ELM327_CAN_CONFIG_VARIABLE_DLC
213 | ELM327_CAN_CONFIG_RECV_BOTH_SFF_EFF
214 | elm->can_bitrate_divisor;
216 set_bit(TODO_CAN_CONFIG, &elm->cmds_todo);
219 if (frame->can_id & CAN_EFF_FLAG) {
220 clear_bit(TODO_CANID_11BIT, &elm->cmds_todo);
221 set_bit(TODO_CANID_29BIT_LOW, &elm->cmds_todo);
222 set_bit(TODO_CANID_29BIT_HIGH, &elm->cmds_todo);
224 set_bit(TODO_CANID_11BIT, &elm->cmds_todo);
225 clear_bit(TODO_CANID_29BIT_LOW, &elm->cmds_todo);
226 clear_bit(TODO_CANID_29BIT_HIGH, &elm->cmds_todo);
230 /* Schedule the CAN frame itself. */
231 elm->can_frame = *frame;
232 set_bit(TODO_CAN_DATA, &elm->cmds_todo);
234 elm327_kick_into_cmd_mode(elm);
237 /* ELM327 initialization sequence.
239 * Assumes elm->lock taken.
241 static char *elm327_init_script[] = {
242 "AT WS\r", /* v1.0: Warm Start */
243 "AT PP FF OFF\r", /* v1.0: All Programmable Parameters Off */
244 "AT M0\r", /* v1.0: Memory Off */
245 "AT AL\r", /* v1.0: Allow Long messages */
246 "AT BI\r", /* v1.0: Bypass Initialization */
247 "AT CAF0\r", /* v1.0: CAN Auto Formatting Off */
248 "AT CFC0\r", /* v1.0: CAN Flow Control Off */
249 "AT CF 000\r", /* v1.0: Reset CAN ID Filter */
250 "AT CM 000\r", /* v1.0: Reset CAN ID Mask */
251 "AT E1\r", /* v1.0: Echo On */
252 "AT H1\r", /* v1.0: Headers On */
253 "AT L0\r", /* v1.0: Linefeeds Off */
254 "AT SH 7DF\r", /* v1.0: Set CAN sending ID to 0x7df */
255 "AT ST FF\r", /* v1.0: Set maximum Timeout for response after TX */
256 "AT AT0\r", /* v1.2: Adaptive Timing Off */
257 "AT D1\r", /* v1.3: Print DLC On */
258 "AT S1\r", /* v1.3: Spaces On */
259 "AT TP B\r", /* v1.0: Try Protocol B */
263 static void elm327_init(struct elmcan *elm)
265 elm->state = ELM_NOTINIT;
266 elm->can_frame.can_id = 0x7df;
268 elm->drop_next_line = 0;
270 /* We can only set the bitrate as a fraction of 500000.
271 * The bit timing constants in elmcan_bittiming_const will
272 * limit the user to the right values.
274 elm->can_bitrate_divisor = 500000 / elm->can.bittiming.bitrate;
275 elm->can_config = ELM327_CAN_CONFIG_SEND_SFF
276 | ELM327_CAN_CONFIG_VARIABLE_DLC
277 | ELM327_CAN_CONFIG_RECV_BOTH_SFF_EFF
278 | elm->can_bitrate_divisor;
280 /* Configure ELM327 and then start monitoring */
281 elm->next_init_cmd = &elm327_init_script[0];
282 set_bit(TODO_INIT, &elm->cmds_todo);
283 set_bit(TODO_SILENT_MONITOR, &elm->cmds_todo);
284 set_bit(TODO_RESPONSES, &elm->cmds_todo);
285 set_bit(TODO_CAN_CONFIG, &elm->cmds_todo);
287 elm327_kick_into_cmd_mode(elm);
290 /* Assumes elm->lock taken. */
291 static void elm327_feed_frame_to_netdev(struct elmcan *elm,
292 const struct can_frame *frame)
294 struct can_frame *cf;
297 if (!netif_running(elm->dev))
300 skb = alloc_can_skb(elm->dev, &cf);
305 memcpy(cf, frame, sizeof(struct can_frame));
307 /* Queue for NAPI pickup.
308 * rx-offload will update stats and LEDs for us.
310 if (can_rx_offload_queue_tail(&elm->offload, skb))
311 elm->dev->stats.rx_fifo_errors++;
313 #if LINUX_VERSION_CODE >= KERNEL_VERSION(5,15,0)
315 can_rx_offload_irq_finish(&elm->offload);
319 /* Called when we're out of ideas and just want it all to end.
320 * Assumes elm->lock taken.
322 static inline void elm327_hw_failure(struct elmcan *elm)
324 struct can_frame frame;
326 memset(&frame, 0, sizeof(frame));
327 frame.can_id = CAN_ERR_FLAG;
328 frame.can_dlc = CAN_ERR_DLC;
332 elm327_feed_frame_to_netdev(elm, &frame);
334 netdev_err(elm->dev, "ELM327 misbehaved. Blocking further communication.\n");
336 elm->hw_failure = true;
337 can_bus_off(elm->dev);
340 /* Compare a buffer to a fixed string */
341 static int _memstrcmp(const u8 *mem, const char *str)
343 return memcmp(mem, str, strlen(str));
346 /* Assumes elm->lock taken. */
347 static void elm327_parse_error(struct elmcan *elm, int len)
349 struct can_frame frame;
351 memset(&frame, 0, sizeof(frame));
352 frame.can_id = CAN_ERR_FLAG;
353 frame.can_dlc = CAN_ERR_DLC;
355 /* Filter possible error messages based on length of RX'd line */
358 if (!_memstrcmp(elm->rxbuf, "UNABLE TO CONNECT")) {
360 "ELM327 reported UNABLE TO CONNECT. Please check your setup.\n");
364 if (!_memstrcmp(elm->rxbuf, "BUFFER FULL")) {
365 /* This case will only happen if the last data
367 * Otherwise, elm327_parse_frame() will heuristically
368 * emit this error frame instead.
370 frame.can_id |= CAN_ERR_CRTL;
371 frame.data[1] = CAN_ERR_CRTL_RX_OVERFLOW;
375 if (!_memstrcmp(elm->rxbuf, "BUS ERROR"))
376 frame.can_id |= CAN_ERR_BUSERROR;
377 if (!_memstrcmp(elm->rxbuf, "CAN ERROR"))
378 frame.can_id |= CAN_ERR_PROT;
379 if (!_memstrcmp(elm->rxbuf, "<RX ERROR"))
380 frame.can_id |= CAN_ERR_PROT;
383 if (!_memstrcmp(elm->rxbuf, "BUS BUSY")) {
384 frame.can_id |= CAN_ERR_PROT;
385 frame.data[2] = CAN_ERR_PROT_OVERLOAD;
387 if (!_memstrcmp(elm->rxbuf, "FB ERROR")) {
388 frame.can_id |= CAN_ERR_PROT;
389 frame.data[2] = CAN_ERR_PROT_TX;
392 case 5: /* ERR is followed by two digits, hence line length 5 */
393 if (!_memstrcmp(elm->rxbuf, "ERR")) {
394 netdev_err(elm->dev, "ELM327 reported an ERR%c%c. Please power it off and on again.\n",
395 elm->rxbuf[3], elm->rxbuf[4]);
396 frame.can_id |= CAN_ERR_CRTL;
400 /* Something else has happened.
401 * Maybe garbage on the UART line.
402 * Emit a generic error frame.
407 elm327_feed_frame_to_netdev(elm, &frame);
410 /* Parse CAN frames coming as ASCII from ELM327.
411 * They can be of various formats:
413 * 29-bit ID (EFF): 12 34 56 78 D PL PL PL PL PL PL PL PL
414 * 11-bit ID (!EFF): 123 D PL PL PL PL PL PL PL PL
416 * where D = DLC, PL = payload byte
418 * Instead of a payload, RTR indicates a remote request.
420 * We will use the spaces and line length to guess the format.
422 * Assumes elm->lock taken.
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 /* Sanity check whether the line is really a clean hexdump,
446 * or terminated by an error message, or contains garbage.
449 !isdigit(elm->rxbuf[hexlen]) &&
450 !isupper(elm->rxbuf[hexlen]) &&
451 '<' != elm->rxbuf[hexlen] &&
452 ' ' != elm->rxbuf[hexlen]) {
453 /* The line is likely garbled anyway, so bail.
454 * The main code will restart listening.
459 /* Use spaces in CAN ID to distinguish 29 or 11 bit address length.
460 * No out-of-bounds access:
461 * We use the fact that we can always read from elm->rxbuf.
463 if (elm->rxbuf[2] == ' ' && elm->rxbuf[5] == ' ' &&
464 elm->rxbuf[8] == ' ' && elm->rxbuf[11] == ' ' &&
465 elm->rxbuf[13] == ' ') {
466 frame.can_id = CAN_EFF_FLAG;
468 } else if (elm->rxbuf[3] == ' ' && elm->rxbuf[5] == ' ') {
472 /* This is not a well-formatted data line.
473 * Assume it's an error message.
478 if (hexlen < datastart) {
479 /* The line is too short to be a valid frame hex dump.
480 * Something interrupted the hex dump or it is invalid.
485 /* From here on all chars up to buf[hexlen] are hex or spaces,
486 * at well-defined offsets.
489 /* Read CAN data length */
490 frame.can_dlc = (hex_to_bin(elm->rxbuf[datastart - 2]) << 0);
493 if (frame.can_id & CAN_EFF_FLAG) {
494 frame.can_id |= (hex_to_bin(elm->rxbuf[0]) << 28)
495 | (hex_to_bin(elm->rxbuf[1]) << 24)
496 | (hex_to_bin(elm->rxbuf[3]) << 20)
497 | (hex_to_bin(elm->rxbuf[4]) << 16)
498 | (hex_to_bin(elm->rxbuf[6]) << 12)
499 | (hex_to_bin(elm->rxbuf[7]) << 8)
500 | (hex_to_bin(elm->rxbuf[9]) << 4)
501 | (hex_to_bin(elm->rxbuf[10]) << 0);
503 frame.can_id |= (hex_to_bin(elm->rxbuf[0]) << 8)
504 | (hex_to_bin(elm->rxbuf[1]) << 4)
505 | (hex_to_bin(elm->rxbuf[2]) << 0);
508 /* Check for RTR frame */
509 if (elm->rxfill >= hexlen + 3 &&
510 !_memstrcmp(&elm->rxbuf[hexlen], "RTR")) {
511 frame.can_id |= CAN_RTR_FLAG;
514 /* Is the line long enough to hold the advertised payload?
515 * Note: RTR frames have a DLC, but no actual payload.
517 if (!(frame.can_id & CAN_RTR_FLAG) &&
518 (hexlen < frame.can_dlc * 3 + datastart)) {
519 /* Incomplete frame. */
521 /* Probably the ELM327's RS232 TX buffer was full.
522 * Emit an error frame and exit.
524 frame.can_id = CAN_ERR_FLAG | CAN_ERR_CRTL;
525 frame.can_dlc = CAN_ERR_DLC;
526 frame.data[1] = CAN_ERR_CRTL_RX_OVERFLOW;
527 elm327_feed_frame_to_netdev(elm, &frame);
529 /* Signal failure to parse.
530 * The line will be re-parsed as an error line, which will fail.
531 * However, this will correctly drop the state machine back into
537 /* Parse the data nibbles. */
538 for (i = 0; i < frame.can_dlc; i++) {
539 frame.data[i] = (hex_to_bin(elm->rxbuf[datastart + 3*i]) << 4)
540 | (hex_to_bin(elm->rxbuf[datastart + 3*i + 1]));
543 /* Feed the frame to the network layer. */
544 elm327_feed_frame_to_netdev(elm, &frame);
549 /* Assumes elm->lock taken. */
550 static void elm327_parse_line(struct elmcan *elm, int len)
552 /* Skip empty lines */
556 /* Skip echo lines */
557 if (elm->drop_next_line) {
558 elm->drop_next_line = 0;
560 } else if (!_memstrcmp(elm->rxbuf, "AT")) {
564 /* Regular parsing */
565 switch (elm->state) {
567 if (elm327_parse_frame(elm, len)) {
568 /* Parse an error line. */
569 elm327_parse_error(elm, len);
572 elm327_kick_into_cmd_mode(elm);
580 /* Assumes elm->lock taken. */
581 static void elm327_handle_prompt(struct elmcan *elm)
583 struct can_frame *frame = &elm->can_frame;
584 char local_txbuf[20];
586 if (!elm->cmds_todo) {
587 /* Enter CAN monitor mode */
588 elm327_send(elm, "ATMA\r", 5);
589 elm->state = ELM_RECEIVING;
594 /* Reconfigure ELM327 step by step as indicated by elm->cmds_todo */
595 if (test_bit(TODO_INIT, &elm->cmds_todo)) {
596 strcpy(local_txbuf, *elm->next_init_cmd);
598 elm->next_init_cmd++;
599 if (!(*elm->next_init_cmd)) {
600 clear_bit(TODO_INIT, &elm->cmds_todo);
601 netdev_info(elm->dev, "Initialization finished.\n");
604 } else if (test_and_clear_bit(TODO_SILENT_MONITOR, &elm->cmds_todo)) {
605 sprintf(local_txbuf, "ATCSM%i\r",
606 !(!(elm->can.ctrlmode & CAN_CTRLMODE_LISTENONLY)));
608 } else if (test_and_clear_bit(TODO_RESPONSES, &elm->cmds_todo)) {
609 sprintf(local_txbuf, "ATR%i\r",
610 !(elm->can.ctrlmode & CAN_CTRLMODE_LISTENONLY));
612 } else if (test_and_clear_bit(TODO_CAN_CONFIG, &elm->cmds_todo)) {
613 sprintf(local_txbuf, "ATPC\r");
614 set_bit(TODO_CAN_CONFIG_PART2, &elm->cmds_todo);
616 } else if (test_and_clear_bit(TODO_CAN_CONFIG_PART2, &elm->cmds_todo)) {
617 sprintf(local_txbuf, "ATPB%04X\r",
620 } else if (test_and_clear_bit(TODO_CANID_29BIT_HIGH, &elm->cmds_todo)) {
621 sprintf(local_txbuf, "ATCP%02X\r",
622 (frame->can_id & CAN_EFF_MASK) >> 24);
624 } else if (test_and_clear_bit(TODO_CANID_29BIT_LOW, &elm->cmds_todo)) {
625 sprintf(local_txbuf, "ATSH%06X\r",
626 frame->can_id & CAN_EFF_MASK & ((1 << 24) - 1));
628 } else if (test_and_clear_bit(TODO_CANID_11BIT, &elm->cmds_todo)) {
629 sprintf(local_txbuf, "ATSH%03X\r",
630 frame->can_id & CAN_SFF_MASK);
632 } else if (test_and_clear_bit(TODO_CAN_DATA, &elm->cmds_todo)) {
633 if (frame->can_id & CAN_RTR_FLAG) {
634 /* Send an RTR frame. Their DLC is fixed.
635 * Some chips don't send them at all.
637 sprintf(local_txbuf, "ATRTR\r");
639 /* Send a regular CAN data frame */
642 for (i = 0; i < frame->can_dlc; i++) {
643 sprintf(&local_txbuf[2 * i], "%02X",
647 sprintf(&local_txbuf[2 * i], "\r");
650 elm->drop_next_line = 1;
651 elm->state = ELM_RECEIVING;
654 elm327_send(elm, local_txbuf, strlen(local_txbuf));
657 static bool elm327_is_ready_char(char c)
659 /* Bits 0xc0 are sometimes set (randomly), hence the mask.
660 * Probably bad hardware.
662 return (c & 0x3f) == ELM327_READY_CHAR;
665 /* Assumes elm->lock taken. */
666 static void elm327_drop_bytes(struct elmcan *elm, int i)
668 memmove(&elm->rxbuf[0], &elm->rxbuf[i], ELM327_SIZE_RXBUF - i);
672 /* Assumes elm->lock taken. */
673 static void elm327_parse_rxbuf(struct elmcan *elm)
677 switch (elm->state) {
682 case ELM_GETMAGICCHAR:
684 /* Wait for 'y' or '>' */
687 for (i = 0; i < elm->rxfill; i++) {
688 if (elm->rxbuf[i] == ELM327_MAGIC_CHAR) {
689 elm327_send(elm, "\r", 1);
690 elm->state = ELM_GETPROMPT;
693 } else if (elm327_is_ready_char(elm->rxbuf[i])) {
694 elm327_send(elm, ELM327_MAGIC_STRING, 1);
700 elm327_drop_bytes(elm, i);
707 if (elm327_is_ready_char(elm->rxbuf[elm->rxfill - 1]))
708 elm327_handle_prompt(elm);
714 /* Find <CR> delimiting feedback lines. */
716 (len < elm->rxfill) && (elm->rxbuf[len] != '\r');
721 if (len == ELM327_SIZE_RXBUF) {
722 /* Line exceeds buffer. It's probably all garbage.
723 * Did we even connect at the right baud rate?
726 "RX buffer overflow. Faulty ELM327 or UART?\n");
727 elm327_hw_failure(elm);
729 } else if (len == elm->rxfill) {
730 if (elm327_is_ready_char(elm->rxbuf[elm->rxfill - 1])) {
731 /* The ELM327's AT ST response timeout ran out,
732 * so we got a prompt.
733 * Clear RX buffer and restart listening.
737 elm327_handle_prompt(elm);
741 /* No <CR> found - we haven't received a full line yet.
742 * Wait for more data.
747 /* We have a full line to parse. */
748 elm327_parse_line(elm, len);
750 /* Remove parsed data from RX buffer. */
751 elm327_drop_bytes(elm, len + 1);
753 /* More data to parse? */
755 elm327_parse_rxbuf(elm);
759 /* Dummy needed to use can_rx_offload */
760 static struct sk_buff *elmcan_mailbox_read(struct can_rx_offload *offload,
761 unsigned int n, u32 *timestamp,
764 WARN_ON_ONCE(1); /* This function is a dummy, so don't call it! */
766 return ERR_PTR(-ENOBUFS);
769 static int elmcan_netdev_open(struct net_device *dev)
771 struct elmcan *elm = netdev_priv(dev);
774 spin_lock_bh(&elm->lock);
775 if (elm->hw_failure) {
776 netdev_err(elm->dev, "Refusing to open interface after a hardware fault has been detected.\n");
777 spin_unlock_bh(&elm->lock);
782 spin_unlock_bh(&elm->lock);
786 /* open_candev() checks for elm->can.bittiming.bitrate != 0 */
787 err = open_candev(dev);
789 spin_unlock_bh(&elm->lock);
794 spin_unlock_bh(&elm->lock);
796 elm->offload.mailbox_read = elmcan_mailbox_read;
797 err = can_rx_offload_add_fifo(dev, &elm->offload, ELM327_NAPI_WEIGHT);
803 can_rx_offload_enable(&elm->offload);
805 can_led_event(dev, CAN_LED_EVENT_OPEN);
806 elm->can.state = CAN_STATE_ERROR_ACTIVE;
807 netif_start_queue(dev);
812 static int elmcan_netdev_close(struct net_device *dev)
814 struct elmcan *elm = netdev_priv(dev);
816 netif_stop_queue(dev);
818 spin_lock_bh(&elm->lock);
820 /* Interrupt whatever we're doing right now */
821 elm327_send(elm, ELM327_MAGIC_STRING, 1);
823 /* Clear the wakeup bit, as the netdev will be down and thus
824 * the wakeup handler won't clear it
826 clear_bit(TTY_DO_WRITE_WAKEUP, &elm->tty->flags);
828 spin_unlock_bh(&elm->lock);
830 flush_work(&elm->tx_work);
832 spin_unlock_bh(&elm->lock);
835 can_rx_offload_disable(&elm->offload);
836 elm->can.state = CAN_STATE_STOPPED;
837 can_rx_offload_del(&elm->offload);
839 can_led_event(dev, CAN_LED_EVENT_STOP);
844 /* Send a can_frame to a TTY. */
845 static netdev_tx_t elmcan_netdev_start_xmit(struct sk_buff *skb,
846 struct net_device *dev)
848 struct elmcan *elm = netdev_priv(dev);
849 struct can_frame *frame = (struct can_frame *)skb->data;
851 if (skb->len != sizeof(struct can_frame))
854 if (!netif_running(dev)) {
855 netdev_warn(elm->dev, "xmit: iface is down.\n");
859 /* BHs are already disabled, so no spin_lock_bh().
860 * See Documentation/networking/netdevices.txt
862 spin_lock(&elm->lock);
864 /* We shouldn't get here after a hardware fault:
865 * can_bus_off() calls netif_carrier_off()
867 WARN_ON_ONCE(elm->hw_failure);
871 elm->can.ctrlmode & CAN_CTRLMODE_LISTENONLY) {
872 spin_unlock(&elm->lock);
876 netif_stop_queue(dev);
878 elm327_send_frame(elm, frame);
879 spin_unlock(&elm->lock);
881 dev->stats.tx_packets++;
882 dev->stats.tx_bytes += frame->can_dlc;
884 can_led_event(dev, CAN_LED_EVENT_TX);
891 static const struct net_device_ops elmcan_netdev_ops = {
892 .ndo_open = elmcan_netdev_open,
893 .ndo_stop = elmcan_netdev_close,
894 .ndo_start_xmit = elmcan_netdev_start_xmit,
895 .ndo_change_mtu = can_change_mtu,
898 /* Get a reference to our struct, taking into account locks/refcounts.
899 * This is to ensure ordering in case we are shutting down, and to ensure
900 * there is a refcount at all (otherwise tty->disc_data may be freed and
901 * before we increment the refcount).
902 * Use this for anything that can race against elmcan_ldisc_close().
904 static struct elmcan *get_elm(struct tty_struct *tty)
909 spin_lock_bh(&elmcan_discdata_lock);
910 elm = (struct elmcan *)tty->disc_data;
913 spin_unlock_bh(&elmcan_discdata_lock);
917 got_ref = atomic_inc_not_zero(&elm->refcount);
918 spin_unlock_bh(&elmcan_discdata_lock);
926 static void put_elm(struct elmcan *elm)
928 atomic_dec(&elm->refcount);
931 static bool elmcan_is_valid_rx_char(char c)
933 return (isdigit(c) ||
935 c == ELM327_MAGIC_CHAR ||
936 c == ELM327_READY_CHAR ||
947 /* Handle incoming ELM327 ASCII data.
948 * This will not be re-entered while running, but other ldisc
949 * functions may be called in parallel.
951 #if LINUX_VERSION_CODE < KERNEL_VERSION(5,14,0)
952 static void elmcan_ldisc_rx(struct tty_struct *tty,
953 const unsigned char *cp, char *fp, int count)
955 static void elmcan_ldisc_rx(struct tty_struct *tty,
956 const unsigned char *cp, const char *fp, int count)
959 struct elmcan *elm = get_elm(tty);
964 spin_lock_bh(&elm->lock);
969 while (count-- && elm->rxfill < ELM327_SIZE_RXBUF) {
971 netdev_err(elm->dev, "Error in received character stream. Check your wiring.");
973 elm327_hw_failure(elm);
978 /* Ignore NUL characters, which the PIC microcontroller may
979 * inadvertently insert due to a known hardware bug.
980 * See ELM327 documentation, which refers to a Microchip PIC
984 /* Check for stray characters on the UART line.
985 * Likely caused by bad hardware.
987 if (!elmcan_is_valid_rx_char(*cp)) {
989 "Received illegal character %02x.\n",
991 elm327_hw_failure(elm);
996 elm->rxbuf[elm->rxfill++] = *cp;
1003 netdev_err(elm->dev, "Receive buffer overflowed. Bad chip or wiring?");
1005 elm327_hw_failure(elm);
1010 elm327_parse_rxbuf(elm);
1013 spin_unlock_bh(&elm->lock);
1017 /* Write out remaining transmit buffer.
1018 * Scheduled when TTY is writable.
1020 static void elmcan_ldisc_tx_worker(struct work_struct *work)
1022 /* No need to use get_elm() here, as we'll always flush workers
1023 * before destroying the elmcan object.
1025 struct elmcan *elm = container_of(work, struct elmcan, tx_work);
1028 spin_lock_bh(&elm->lock);
1029 if (elm->hw_failure) {
1030 spin_unlock_bh(&elm->lock);
1034 if (!elm->tty || !netif_running(elm->dev)) {
1035 spin_unlock_bh(&elm->lock);
1039 if (elm->txleft <= 0) {
1040 /* Our TTY write buffer is empty:
1041 * Allow netdev to hand us another packet
1043 clear_bit(TTY_DO_WRITE_WAKEUP, &elm->tty->flags);
1044 spin_unlock_bh(&elm->lock);
1045 netif_wake_queue(elm->dev);
1049 actual = elm->tty->ops->write(elm->tty, elm->txhead, elm->txleft);
1051 netdev_err(elm->dev,
1052 "Failed to write to tty %s.\n",
1054 elm327_hw_failure(elm);
1055 spin_unlock_bh(&elm->lock);
1059 elm->txleft -= actual;
1060 elm->txhead += actual;
1061 spin_unlock_bh(&elm->lock);
1064 /* Called by the driver when there's room for more data. */
1065 static void elmcan_ldisc_tx_wakeup(struct tty_struct *tty)
1067 struct elmcan *elm = get_elm(tty);
1072 schedule_work(&elm->tx_work);
1077 /* ELM327 can only handle bitrates that are integer divisors of 500 kHz,
1078 * or 7/8 of that. Divisors are 1 to 64.
1079 * Currently we don't implement support for 7/8 rates.
1081 static const u32 elmcan_bitrate_const[64] = {
1082 7812, 7936, 8064, 8196, 8333, 8474, 8620, 8771,
1083 8928, 9090, 9259, 9433, 9615, 9803, 10000, 10204,
1084 10416, 10638, 10869, 11111, 11363, 11627, 11904, 12195,
1085 12500, 12820, 13157, 13513, 13888, 14285, 14705, 15151,
1086 15625, 16129, 16666, 17241, 17857, 18518, 19230, 20000,
1087 20833, 21739, 22727, 23809, 25000, 26315, 27777, 29411,
1088 31250, 33333, 35714, 38461, 41666, 45454, 50000, 55555,
1089 62500, 71428, 83333, 100000, 125000, 166666, 250000, 500000
1092 /* Dummy needed to use bitrate_const */
1093 static int elmcan_do_set_bittiming(struct net_device *netdev)
1098 static int elmcan_ldisc_open(struct tty_struct *tty)
1100 struct net_device *dev;
1104 if (!capable(CAP_NET_ADMIN))
1107 if (!tty->ops->write)
1110 dev = alloc_candev(sizeof(struct elmcan), 0);
1113 elm = netdev_priv(dev);
1115 elm->txbuf = kmalloc(ELM327_SIZE_TXBUF, GFP_KERNEL);
1121 /* Configure TTY interface */
1122 tty->receive_room = 65536; /* We don't flow control */
1123 elm->txleft = 0; /* Clear TTY TX buffer */
1124 spin_lock_init(&elm->lock);
1125 atomic_set(&elm->refcount, 1);
1126 INIT_WORK(&elm->tx_work, elmcan_ldisc_tx_worker);
1128 /* Configure CAN metadata */
1129 elm->can.state = CAN_STATE_STOPPED;
1130 elm->can.bitrate_const = elmcan_bitrate_const;
1131 elm->can.bitrate_const_cnt = ARRAY_SIZE(elmcan_bitrate_const);
1132 elm->can.do_set_bittiming = elmcan_do_set_bittiming;
1133 elm->can.ctrlmode_supported = CAN_CTRLMODE_LISTENONLY;
1135 /* Configure netdev interface */
1137 dev->netdev_ops = &elmcan_netdev_ops;
1139 /* Mark ldisc channel as alive */
1141 tty->disc_data = elm;
1143 devm_can_led_init(elm->dev);
1146 err = register_candev(elm->dev);
1150 netdev_info(elm->dev, "elmcan on %s.\n", tty->name);
1156 free_candev(elm->dev);
1160 /* Close down an elmcan channel.
1161 * This means flushing out any pending queues, and then returning.
1162 * This call is serialized against other ldisc functions:
1163 * Once this is called, no other ldisc function of ours is entered.
1165 * We also use this function for a hangup event.
1167 static void elmcan_ldisc_close(struct tty_struct *tty)
1169 struct elmcan *elm = get_elm(tty);
1174 /* unregister_netdev() calls .ndo_stop() so we don't have to. */
1175 unregister_candev(elm->dev);
1177 /* Decrease the refcount twice, once for our own get_elm(),
1178 * and once to remove the count of 1 that we set in _open().
1179 * Once it reaches 0, we can safely destroy it.
1184 while (atomic_read(&elm->refcount) > 0)
1185 msleep_interruptible(10);
1187 /* At this point, all ldisc calls to us have become no-ops. */
1189 flush_work(&elm->tx_work);
1191 /* Mark channel as dead */
1192 spin_lock_bh(&elm->lock);
1193 tty->disc_data = NULL;
1195 spin_unlock_bh(&elm->lock);
1197 netdev_info(elm->dev, "elmcan off %s.\n", tty->name);
1200 free_candev(elm->dev);
1203 #if LINUX_VERSION_CODE < KERNEL_VERSION(5,16,0)
1204 static int elmcan_ldisc_hangup(struct tty_struct *tty)
1206 static void elmcan_ldisc_hangup(struct tty_struct *tty)
1209 elmcan_ldisc_close(tty);
1210 #if LINUX_VERSION_CODE < KERNEL_VERSION(5,16,0)
1215 static int elmcan_ldisc_ioctl(struct tty_struct *tty,
1216 #if LINUX_VERSION_CODE < KERNEL_VERSION(5,17,0)
1219 unsigned int cmd, unsigned long arg)
1221 struct elmcan *elm = get_elm(tty);
1229 tmp = strnlen(elm->dev->name, IFNAMSIZ - 1) + 1;
1230 if (copy_to_user((void __user *)arg, elm->dev->name, tmp)) {
1244 #if LINUX_VERSION_CODE < KERNEL_VERSION(5,16,0)
1245 return tty_mode_ioctl(tty, file, cmd, arg);
1247 return tty_mode_ioctl(tty, cmd, arg);
1252 static struct tty_ldisc_ops elmcan_ldisc = {
1253 .owner = THIS_MODULE,
1255 .num = N_DEVELOPMENT,
1256 .receive_buf = elmcan_ldisc_rx,
1257 .write_wakeup = elmcan_ldisc_tx_wakeup,
1258 .open = elmcan_ldisc_open,
1259 .close = elmcan_ldisc_close,
1260 .hangup = elmcan_ldisc_hangup,
1261 .ioctl = elmcan_ldisc_ioctl,
1264 static int __init elmcan_init(void)
1268 #if LINUX_VERSION_CODE < KERNEL_VERSION(5,14,0)
1269 status = tty_register_ldisc(N_DEVELOPMENT, &elmcan_ldisc);
1271 status = tty_register_ldisc(&elmcan_ldisc);
1274 pr_err("Can't register line discipline\n");
1279 static void __exit elmcan_exit(void)
1281 /* This will only be called when all channels have been closed by
1282 * userspace - tty_ldisc.c takes care of the module's refcount.
1284 #if LINUX_VERSION_CODE < KERNEL_VERSION(5,14,0)
1287 status = tty_unregister_ldisc(N_DEVELOPMENT);
1289 pr_err("Can't unregister line discipline (error: %d)\n",
1292 tty_unregister_ldisc(&elmcan_ldisc);
1296 module_init(elmcan_init);
1297 module_exit(elmcan_exit);