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.
7 * can327.c Author : Max Staudt <max-linux@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>
13 #define pr_fmt(fmt) "can327: " fmt
15 #include <linux/init.h>
16 #include <linux/module.h>
18 #include <linux/bitops.h>
19 #include <linux/ctype.h>
20 #include <linux/errno.h>
21 #include <linux/kernel.h>
22 #include <linux/list.h>
23 #include <linux/lockdep.h>
24 #include <linux/netdevice.h>
25 #include <linux/skbuff.h>
26 #include <linux/spinlock.h>
27 #include <linux/string.h>
28 #include <linux/tty.h>
29 #include <linux/tty_ldisc.h>
30 #include <linux/version.h>
31 #include <linux/workqueue.h>
33 #include <uapi/linux/tty.h>
35 #include <linux/can.h>
36 #include <linux/can/dev.h>
37 #include <linux/can/error.h>
38 #include <linux/can/rx-offload.h>
40 /* Line discipline ID number.
41 * Starting with Linux v5.18-rc1, N_DEVELOPMENT is defined as 29:
42 * https://github.com/torvalds/linux/commit/c2faf737abfb10f88f2d2612d573e9edc3c42c37
45 #define N_DEVELOPMENT 29
48 /* Compatibility for Linux < 5.11 */
49 #if LINUX_VERSION_CODE < KERNEL_VERSION(5,11,0)
53 #define CAN327_NAPI_WEIGHT 4
55 #define CAN327_SIZE_TXBUF 32
56 #define CAN327_SIZE_RXBUF 1024
58 #define CAN327_CAN_CONFIG_SEND_SFF 0x8000
59 #define CAN327_CAN_CONFIG_VARIABLE_DLC 0x4000
60 #define CAN327_CAN_CONFIG_RECV_BOTH_SFF_EFF 0x2000
61 #define CAN327_CAN_CONFIG_BAUDRATE_MULT_8_7 0x1000
63 #define CAN327_DUMMY_CHAR 'y'
64 #define CAN327_DUMMY_STRING "y"
65 #define CAN327_READY_CHAR '>'
67 /* Bits in elm->cmds_todo */
69 CAN327_TX_DO_CAN_DATA = 0,
70 CAN327_TX_DO_CANID_11BIT,
71 CAN327_TX_DO_CANID_29BIT_LOW,
72 CAN327_TX_DO_CANID_29BIT_HIGH,
73 CAN327_TX_DO_CAN_CONFIG_PART2,
74 CAN327_TX_DO_CAN_CONFIG,
75 CAN327_TX_DO_RESPONSES,
76 CAN327_TX_DO_SILENT_MONITOR,
81 /* This must be the first member when using alloc_candev() */
84 struct can_rx_offload offload;
87 u8 txbuf[CAN327_SIZE_TXBUF];
88 u8 rxbuf[CAN327_SIZE_RXBUF];
90 /* Per-channel lock */
93 /* TTY and netdev devices that we're bridging */
94 struct tty_struct *tty;
95 struct net_device *dev;
97 /* TTY buffer accounting */
98 struct work_struct tx_work; /* Flushes TTY TX buffer */
99 u8 *txhead; /* Next TX byte */
100 size_t txleft; /* Bytes left to TX */
101 int rxfill; /* Bytes already RX'd in buffer */
105 CAN327_STATE_NOTINIT = 0,
106 CAN327_STATE_GETDUMMYCHAR,
107 CAN327_STATE_GETPROMPT,
108 CAN327_STATE_RECEIVING,
111 /* Things we have yet to send */
112 char **next_init_cmd;
113 unsigned long cmds_todo;
115 /* The CAN frame and config the ELM327 is sending/using,
116 * or will send/use after finishing all cmds_todo
118 struct can_frame can_frame_to_send;
120 u8 can_bitrate_divisor;
125 /* Stop the channel on UART side hardware failure, e.g. stray
126 * characters or neverending lines. This may be caused by bad
127 * UART wiring, a bad ELM327, a bad UART bridge...
128 * Once this is true, nothing will be sent to the TTY.
130 bool uart_side_failure;
133 static inline void can327_uart_side_failure(struct can327 *elm);
135 static void can327_send(struct can327 *elm, const void *buf, size_t len)
139 lockdep_assert_held(&elm->lock);
141 if (elm->uart_side_failure)
144 memcpy(elm->txbuf, buf, len);
146 /* Order of next two lines is *very* important.
147 * When we are sending a little amount of data,
148 * the transfer may be completed inside the ops->write()
149 * routine, because it's running with interrupts enabled.
150 * In this case we *never* got WRITE_WAKEUP event,
151 * if we did not request it before write operation.
152 * 14 Oct 1994 Dmitry Gorodchanin.
154 set_bit(TTY_DO_WRITE_WAKEUP, &elm->tty->flags);
155 written = elm->tty->ops->write(elm->tty, elm->txbuf, len);
158 "Failed to write to tty %s.\n",
160 can327_uart_side_failure(elm);
164 elm->txleft = len - written;
165 elm->txhead = elm->txbuf + written;
168 /* Take the ELM327 out of almost any state and back into command mode.
169 * We send CAN327_DUMMY_CHAR which will either abort any running
170 * operation, or be echoed back to us in case we're already in command
173 static void can327_kick_into_cmd_mode(struct can327 *elm)
175 lockdep_assert_held(&elm->lock);
177 if (elm->state != CAN327_STATE_GETDUMMYCHAR &&
178 elm->state != CAN327_STATE_GETPROMPT) {
179 can327_send(elm, CAN327_DUMMY_STRING, 1);
181 elm->state = CAN327_STATE_GETDUMMYCHAR;
185 /* Schedule a CAN frame and necessary config changes to be sent to the TTY. */
186 static void can327_send_frame(struct can327 *elm, struct can_frame *frame)
188 lockdep_assert_held(&elm->lock);
190 /* Schedule any necessary changes in ELM327's CAN configuration */
191 if (elm->can_frame_to_send.can_id != frame->can_id) {
192 /* Set the new CAN ID for transmission. */
193 if ((frame->can_id ^ elm->can_frame_to_send.can_id)
195 elm->can_config = (frame->can_id & CAN_EFF_FLAG
197 : CAN327_CAN_CONFIG_SEND_SFF)
198 | CAN327_CAN_CONFIG_VARIABLE_DLC
199 | CAN327_CAN_CONFIG_RECV_BOTH_SFF_EFF
200 | elm->can_bitrate_divisor;
202 set_bit(CAN327_TX_DO_CAN_CONFIG, &elm->cmds_todo);
205 if (frame->can_id & CAN_EFF_FLAG) {
206 clear_bit(CAN327_TX_DO_CANID_11BIT, &elm->cmds_todo);
207 set_bit(CAN327_TX_DO_CANID_29BIT_LOW, &elm->cmds_todo);
208 set_bit(CAN327_TX_DO_CANID_29BIT_HIGH, &elm->cmds_todo);
210 set_bit(CAN327_TX_DO_CANID_11BIT, &elm->cmds_todo);
211 clear_bit(CAN327_TX_DO_CANID_29BIT_LOW, &elm->cmds_todo);
212 clear_bit(CAN327_TX_DO_CANID_29BIT_HIGH, &elm->cmds_todo);
216 /* Schedule the CAN frame itself. */
217 elm->can_frame_to_send = *frame;
218 set_bit(CAN327_TX_DO_CAN_DATA, &elm->cmds_todo);
220 can327_kick_into_cmd_mode(elm);
223 /* ELM327 initialisation sequence.
224 * The line length is limited by the buffer in can327_handle_prompt().
226 static char *can327_init_script[] = {
227 "AT WS\r", /* v1.0: Warm Start */
228 "AT PP FF OFF\r", /* v1.0: All Programmable Parameters Off */
229 "AT M0\r", /* v1.0: Memory Off */
230 "AT AL\r", /* v1.0: Allow Long messages */
231 "AT BI\r", /* v1.0: Bypass Initialisation */
232 "AT CAF0\r", /* v1.0: CAN Auto Formatting Off */
233 "AT CFC0\r", /* v1.0: CAN Flow Control Off */
234 "AT CF 000\r", /* v1.0: Reset CAN ID Filter */
235 "AT CM 000\r", /* v1.0: Reset CAN ID Mask */
236 "AT E1\r", /* v1.0: Echo On */
237 "AT H1\r", /* v1.0: Headers On */
238 "AT L0\r", /* v1.0: Linefeeds Off */
239 "AT SH 7DF\r", /* v1.0: Set CAN sending ID to 0x7df */
240 "AT ST FF\r", /* v1.0: Set maximum Timeout for response after TX */
241 "AT AT0\r", /* v1.2: Adaptive Timing Off */
242 "AT D1\r", /* v1.3: Print DLC On */
243 "AT S1\r", /* v1.3: Spaces On */
244 "AT TP B\r", /* v1.0: Try Protocol B */
248 static void can327_init_device(struct can327 *elm)
250 lockdep_assert_held(&elm->lock);
252 elm->state = CAN327_STATE_NOTINIT;
253 elm->can_frame_to_send.can_id = 0x7df; /* ELM327 HW default */
255 elm->drop_next_line = 0;
257 /* We can only set the bitrate as a fraction of 500000.
258 * The bitrates listed in can327_bitrate_const will
259 * limit the user to the right values.
261 elm->can_bitrate_divisor = 500000 / elm->can.bittiming.bitrate;
262 elm->can_config = CAN327_CAN_CONFIG_SEND_SFF
263 | CAN327_CAN_CONFIG_VARIABLE_DLC
264 | CAN327_CAN_CONFIG_RECV_BOTH_SFF_EFF
265 | elm->can_bitrate_divisor;
267 /* Configure ELM327 and then start monitoring */
268 elm->next_init_cmd = &can327_init_script[0];
269 set_bit(CAN327_TX_DO_INIT, &elm->cmds_todo);
270 set_bit(CAN327_TX_DO_SILENT_MONITOR, &elm->cmds_todo);
271 set_bit(CAN327_TX_DO_RESPONSES, &elm->cmds_todo);
272 set_bit(CAN327_TX_DO_CAN_CONFIG, &elm->cmds_todo);
274 can327_kick_into_cmd_mode(elm);
277 static void can327_feed_frame_to_netdev(struct can327 *elm,
280 lockdep_assert_held(&elm->lock);
282 if (!netif_running(elm->dev))
285 /* Queue for NAPI pickup.
286 * rx-offload will update stats and LEDs for us.
288 if (can_rx_offload_queue_tail(&elm->offload, skb))
289 elm->dev->stats.rx_fifo_errors++;
291 #if LINUX_VERSION_CODE >= KERNEL_VERSION(5,15,0)
293 can_rx_offload_irq_finish(&elm->offload);
297 /* Called when we're out of ideas and just want it all to end. */
298 static inline void can327_uart_side_failure(struct can327 *elm)
300 struct can_frame *frame;
303 lockdep_assert_held(&elm->lock);
305 elm->uart_side_failure = true;
307 clear_bit(TTY_DO_WRITE_WAKEUP, &elm->tty->flags);
309 elm->can.can_stats.bus_off++;
310 netif_stop_queue(elm->dev);
311 elm->can.state = CAN_STATE_BUS_OFF;
312 can_bus_off(elm->dev);
314 netdev_err(elm->dev, "ELM327 misbehaved. Blocking further communication.\n");
316 skb = alloc_can_err_skb(elm->dev, &frame);
320 frame->can_id |= CAN_ERR_BUSOFF;
321 can327_feed_frame_to_netdev(elm, skb);
324 /* Compares a byte buffer (non-NUL terminated) to the payload part of a string,
325 * and returns true iff the buffer (content *and* length) is exactly that
326 * string, without the terminating NUL byte.
328 * Example: If reference is "BUS ERROR", then this returns true iff nbytes == 9
329 * and !memcmp(buf, "BUS ERROR", 9).
331 * The reason to use strings is so we can easily include them in the C code,
332 * and to avoid hardcoding lengths.
334 static inline bool can327_rxbuf_cmp(const u8 *buf, size_t nbytes, const char *reference)
336 size_t ref_len = strlen(reference);
338 return (nbytes == ref_len) && !memcmp(buf, reference, ref_len);
341 static void can327_parse_error(struct can327 *elm, size_t len)
343 struct can_frame *frame;
346 lockdep_assert_held(&elm->lock);
348 skb = alloc_can_err_skb(elm->dev, &frame);
350 /* It's okay to return here:
351 * The outer parsing loop will drop this UART buffer.
355 /* Filter possible error messages based on length of RX'd line */
356 if (can327_rxbuf_cmp(elm->rxbuf, len, "UNABLE TO CONNECT")) {
358 "ELM327 reported UNABLE TO CONNECT. Please check your setup.\n");
359 } else if (can327_rxbuf_cmp(elm->rxbuf, len, "BUFFER FULL")) {
360 /* This will only happen if the last data line was complete.
361 * Otherwise, can327_parse_frame() will heuristically
362 * emit this kind of error frame instead.
364 frame->can_id |= CAN_ERR_CRTL;
365 frame->data[1] = CAN_ERR_CRTL_RX_OVERFLOW;
366 } else if (can327_rxbuf_cmp(elm->rxbuf, len, "BUS ERROR")) {
367 frame->can_id |= CAN_ERR_BUSERROR;
368 } else if (can327_rxbuf_cmp(elm->rxbuf, len, "CAN ERROR")) {
369 frame->can_id |= CAN_ERR_PROT;
370 } else if (can327_rxbuf_cmp(elm->rxbuf, len, "<RX ERROR")) {
371 frame->can_id |= CAN_ERR_PROT;
372 } else if (can327_rxbuf_cmp(elm->rxbuf, len, "BUS BUSY")) {
373 frame->can_id |= CAN_ERR_PROT;
374 frame->data[2] = CAN_ERR_PROT_OVERLOAD;
375 } else if (can327_rxbuf_cmp(elm->rxbuf, len, "FB ERROR")) {
376 frame->can_id |= CAN_ERR_PROT;
377 frame->data[2] = CAN_ERR_PROT_TX;
378 } else if (len == 5 && !memcmp(elm->rxbuf, "ERR", 3)) {
379 /* ERR is followed by two digits, hence line length 5 */
380 netdev_err(elm->dev, "ELM327 reported an ERR%c%c. Please power it off and on again.\n",
381 elm->rxbuf[3], elm->rxbuf[4]);
382 frame->can_id |= CAN_ERR_CRTL;
384 /* Something else has happened.
385 * Maybe garbage on the UART line.
386 * Emit a generic error frame.
390 can327_feed_frame_to_netdev(elm, skb);
393 /* Parse CAN frames coming as ASCII from ELM327.
394 * They can be of various formats:
396 * 29-bit ID (EFF): 12 34 56 78 D PL PL PL PL PL PL PL PL
397 * 11-bit ID (!EFF): 123 D PL PL PL PL PL PL PL PL
399 * where D = DLC, PL = payload byte
401 * Instead of a payload, RTR indicates a remote request.
403 * We will use the spaces and line length to guess the format.
405 static int can327_parse_frame(struct can327 *elm, size_t len)
407 struct can_frame *frame;
413 lockdep_assert_held(&elm->lock);
415 skb = alloc_can_skb(elm->dev, &frame);
419 /* Find first non-hex and non-space character:
420 * - In the simplest case, there is none.
421 * - For RTR frames, 'R' is the first non-hex character.
422 * - An error message may replace the end of the data line.
424 for (hexlen = 0; hexlen <= len; hexlen++) {
425 if (hex_to_bin(elm->rxbuf[hexlen]) < 0 &&
426 elm->rxbuf[hexlen] != ' ') {
431 /* Sanity check whether the line is really a clean hexdump,
432 * or terminated by an error message, or contains garbage.
435 !isdigit(elm->rxbuf[hexlen]) &&
436 !isupper(elm->rxbuf[hexlen]) &&
437 '<' != elm->rxbuf[hexlen] &&
438 ' ' != elm->rxbuf[hexlen]) {
439 /* The line is likely garbled anyway, so bail.
440 * The main code will restart listening.
446 /* Use spaces in CAN ID to distinguish 29 or 11 bit address length.
447 * No out-of-bounds access:
448 * We use the fact that we can always read from elm->rxbuf.
450 if (elm->rxbuf[2] == ' ' && elm->rxbuf[5] == ' ' &&
451 elm->rxbuf[8] == ' ' && elm->rxbuf[11] == ' ' &&
452 elm->rxbuf[13] == ' ') {
453 frame->can_id = CAN_EFF_FLAG;
455 } else if (elm->rxbuf[3] == ' ' && elm->rxbuf[5] == ' ') {
458 /* This is not a well-formatted data line.
459 * Assume it's an error message.
465 if (hexlen < datastart) {
466 /* The line is too short to be a valid frame hex dump.
467 * Something interrupted the hex dump or it is invalid.
473 /* From here on all chars up to buf[hexlen] are hex or spaces,
474 * at well-defined offsets.
477 /* Read CAN data length */
478 frame->len = (hex_to_bin(elm->rxbuf[datastart - 2]) << 0);
481 if (frame->can_id & CAN_EFF_FLAG) {
482 frame->can_id |= (hex_to_bin(elm->rxbuf[0]) << 28)
483 | (hex_to_bin(elm->rxbuf[1]) << 24)
484 | (hex_to_bin(elm->rxbuf[3]) << 20)
485 | (hex_to_bin(elm->rxbuf[4]) << 16)
486 | (hex_to_bin(elm->rxbuf[6]) << 12)
487 | (hex_to_bin(elm->rxbuf[7]) << 8)
488 | (hex_to_bin(elm->rxbuf[9]) << 4)
489 | (hex_to_bin(elm->rxbuf[10]) << 0);
491 frame->can_id |= (hex_to_bin(elm->rxbuf[0]) << 8)
492 | (hex_to_bin(elm->rxbuf[1]) << 4)
493 | (hex_to_bin(elm->rxbuf[2]) << 0);
496 /* Check for RTR frame */
497 if (elm->rxfill >= hexlen + 3 &&
498 !memcmp(&elm->rxbuf[hexlen], "RTR", 3)) {
499 frame->can_id |= CAN_RTR_FLAG;
502 /* Is the line long enough to hold the advertised payload?
503 * Note: RTR frames have a DLC, but no actual payload.
505 if (!(frame->can_id & CAN_RTR_FLAG) &&
506 (hexlen < frame->len * 3 + datastart)) {
508 * Probably the ELM327's RS232 TX buffer was full.
509 * Emit an error frame and exit.
511 frame->can_id = CAN_ERR_FLAG | CAN_ERR_CRTL;
512 frame->len = CAN_ERR_DLC;
513 frame->data[1] = CAN_ERR_CRTL_RX_OVERFLOW;
514 can327_feed_frame_to_netdev(elm, skb);
516 /* Signal failure to parse.
517 * The line will be re-parsed as an error line, which will fail.
518 * However, this will correctly drop the state machine back into
524 /* Parse the data nibbles. */
525 for (i = 0; i < frame->len; i++) {
526 frame->data[i] = (hex_to_bin(elm->rxbuf[datastart + 3*i]) << 4)
527 | (hex_to_bin(elm->rxbuf[datastart + 3*i + 1]));
530 /* Feed the frame to the network layer. */
531 can327_feed_frame_to_netdev(elm, skb);
536 static void can327_parse_line(struct can327 *elm, size_t len)
538 lockdep_assert_held(&elm->lock);
540 /* Skip empty lines */
544 /* Skip echo lines */
545 if (elm->drop_next_line) {
546 elm->drop_next_line = 0;
548 } else if (!memcmp(elm->rxbuf, "AT", 2)) {
552 /* Regular parsing */
553 if (elm->state == CAN327_STATE_RECEIVING &&
554 can327_parse_frame(elm, len)) {
555 /* Parse an error line. */
556 can327_parse_error(elm, len);
559 can327_kick_into_cmd_mode(elm);
563 static void can327_handle_prompt(struct can327 *elm)
565 struct can_frame *frame = &elm->can_frame_to_send;
566 /* Size this buffer for the largest ELM327 line we may generate,
567 * which is currently an 8 byte CAN frame's payload hexdump.
568 * Items in can327_init_script must fit here, too!
570 char local_txbuf[sizeof("0102030405060708\r")];
572 lockdep_assert_held(&elm->lock);
574 if (!elm->cmds_todo) {
575 /* Enter CAN monitor mode */
576 can327_send(elm, "ATMA\r", 5);
577 elm->state = CAN327_STATE_RECEIVING;
579 /* We will be in the default state once this command is
580 * sent, so enable the TX packet queue.
582 netif_wake_queue(elm->dev);
587 /* Reconfigure ELM327 step by step as indicated by elm->cmds_todo */
588 if (test_bit(CAN327_TX_DO_INIT, &elm->cmds_todo)) {
589 snprintf(local_txbuf, sizeof(local_txbuf),
591 *elm->next_init_cmd);
593 elm->next_init_cmd++;
594 if (!(*elm->next_init_cmd)) {
595 clear_bit(CAN327_TX_DO_INIT, &elm->cmds_todo);
599 } else if (test_and_clear_bit(CAN327_TX_DO_SILENT_MONITOR, &elm->cmds_todo)) {
600 snprintf(local_txbuf, sizeof(local_txbuf),
602 !!(elm->can.ctrlmode & CAN_CTRLMODE_LISTENONLY));
604 } else if (test_and_clear_bit(CAN327_TX_DO_RESPONSES, &elm->cmds_todo)) {
605 snprintf(local_txbuf, sizeof(local_txbuf),
607 !(elm->can.ctrlmode & CAN_CTRLMODE_LISTENONLY));
609 } else if (test_and_clear_bit(CAN327_TX_DO_CAN_CONFIG, &elm->cmds_todo)) {
610 snprintf(local_txbuf, sizeof(local_txbuf),
612 set_bit(CAN327_TX_DO_CAN_CONFIG_PART2, &elm->cmds_todo);
614 } else if (test_and_clear_bit(CAN327_TX_DO_CAN_CONFIG_PART2, &elm->cmds_todo)) {
615 snprintf(local_txbuf, sizeof(local_txbuf),
619 } else if (test_and_clear_bit(CAN327_TX_DO_CANID_29BIT_HIGH, &elm->cmds_todo)) {
620 snprintf(local_txbuf, sizeof(local_txbuf),
622 (frame->can_id & CAN_EFF_MASK) >> 24);
624 } else if (test_and_clear_bit(CAN327_TX_DO_CANID_29BIT_LOW, &elm->cmds_todo)) {
625 snprintf(local_txbuf, sizeof(local_txbuf),
627 frame->can_id & CAN_EFF_MASK & ((1 << 24) - 1));
629 } else if (test_and_clear_bit(CAN327_TX_DO_CANID_11BIT, &elm->cmds_todo)) {
630 snprintf(local_txbuf, sizeof(local_txbuf),
632 frame->can_id & CAN_SFF_MASK);
634 } else if (test_and_clear_bit(CAN327_TX_DO_CAN_DATA, &elm->cmds_todo)) {
635 if (frame->can_id & CAN_RTR_FLAG) {
636 /* Send an RTR frame. Their DLC is fixed.
637 * Some chips don't send them at all.
639 snprintf(local_txbuf, sizeof(local_txbuf),
642 /* Send a regular CAN data frame */
645 for (i = 0; i < frame->len; i++) {
646 snprintf(&local_txbuf[2 * i], sizeof(local_txbuf),
651 snprintf(&local_txbuf[2 * i], sizeof(local_txbuf),
655 elm->drop_next_line = 1;
656 elm->state = CAN327_STATE_RECEIVING;
658 /* We will be in the default state once this command is
659 * sent, so enable the TX packet queue.
661 netif_wake_queue(elm->dev);
664 can327_send(elm, local_txbuf, strlen(local_txbuf));
667 static bool can327_is_ready_char(char c)
669 /* Bits 0xc0 are sometimes set (randomly), hence the mask.
670 * Probably bad hardware.
672 return (c & 0x3f) == CAN327_READY_CHAR;
675 static void can327_drop_bytes(struct can327 *elm, size_t i)
677 lockdep_assert_held(&elm->lock);
679 memmove(&elm->rxbuf[0], &elm->rxbuf[i], CAN327_SIZE_RXBUF - i);
683 static void can327_parse_rxbuf(struct can327 *elm, size_t first_new_char_idx)
687 lockdep_assert_held(&elm->lock);
689 switch (elm->state) {
690 case CAN327_STATE_NOTINIT:
694 case CAN327_STATE_GETDUMMYCHAR:
695 /* Wait for 'y' or '>' */
696 for (pos = 0; pos < elm->rxfill; pos++) {
697 if (elm->rxbuf[pos] == CAN327_DUMMY_CHAR) {
698 can327_send(elm, "\r", 1);
699 elm->state = CAN327_STATE_GETPROMPT;
702 } else if (can327_is_ready_char(elm->rxbuf[pos])) {
703 can327_send(elm, CAN327_DUMMY_STRING, 1);
709 can327_drop_bytes(elm, pos);
712 case CAN327_STATE_GETPROMPT:
714 if (can327_is_ready_char(elm->rxbuf[elm->rxfill - 1]))
715 can327_handle_prompt(elm);
720 case CAN327_STATE_RECEIVING:
721 /* Find <CR> delimiting feedback lines. */
722 len = first_new_char_idx;
723 while (len < elm->rxfill && elm->rxbuf[len] != '\r')
726 if (len == CAN327_SIZE_RXBUF) {
727 /* Assume the buffer ran full with garbage.
728 * Did we even connect at the right baud rate?
731 "RX buffer overflow. Faulty ELM327 or UART?\n");
732 can327_uart_side_failure(elm);
733 } else if (len == elm->rxfill) {
734 if (can327_is_ready_char(elm->rxbuf[elm->rxfill - 1])) {
735 /* The ELM327's AT ST response timeout ran out,
736 * so we got a prompt.
737 * Clear RX buffer and restart listening.
741 can327_handle_prompt(elm);
744 /* No <CR> found - we haven't received a full line yet.
745 * Wait for more data.
748 /* We have a full line to parse. */
749 can327_parse_line(elm, len);
751 /* Remove parsed data from RX buffer. */
752 can327_drop_bytes(elm, len + 1);
754 /* More data to parse? */
756 can327_parse_rxbuf(elm, 0);
761 #if LINUX_VERSION_CODE < KERNEL_VERSION(5,10,0)
762 /* Dummy needed to use can_rx_offload */
763 #if LINUX_VERSION_CODE < KERNEL_VERSION(5,5,0)
764 static unsigned int *can327_mailbox_read(struct can_rx_offload *offload,
765 struct can_frame *cf,
766 u32 *timestamp, unsigned int n)
768 WARN_ON_ONCE(1); /* This function is a dummy, so don't call it! */
772 #else /* Since 4e9c9484b085 (included in v5.5) */
773 static struct sk_buff *can327_mailbox_read(struct can_rx_offload *offload,
774 unsigned int n, u32 *timestamp,
777 WARN_ON_ONCE(1); /* This function is a dummy, so don't call it! */
779 return ERR_PTR(-ENOBUFS);
784 static int can327_netdev_open(struct net_device *dev)
786 struct can327 *elm = netdev_priv(dev);
789 spin_lock_bh(&elm->lock);
792 spin_unlock_bh(&elm->lock);
796 if (elm->uart_side_failure)
797 netdev_warn(elm->dev, "Reopening netdev after a UART side fault has been detected.\n");
799 /* Clear TTY buffers */
803 /* open_candev() checks for elm->can.bittiming.bitrate != 0 */
804 err = open_candev(dev);
806 spin_unlock_bh(&elm->lock);
810 can327_init_device(elm);
811 spin_unlock_bh(&elm->lock);
813 #if LINUX_VERSION_CODE < KERNEL_VERSION(5,10,0)
814 elm->offload.mailbox_read = can327_mailbox_read;
815 err = can_rx_offload_add_fifo(dev, &elm->offload, CAN327_NAPI_WEIGHT);
817 err = can_rx_offload_add_manual(dev, &elm->offload, CAN327_NAPI_WEIGHT);
824 can_rx_offload_enable(&elm->offload);
826 elm->can.state = CAN_STATE_ERROR_ACTIVE;
827 netif_start_queue(dev);
832 static int can327_netdev_close(struct net_device *dev)
834 struct can327 *elm = netdev_priv(dev);
836 /* Interrupt whatever the ELM327 is doing right now */
837 spin_lock_bh(&elm->lock);
838 can327_send(elm, CAN327_DUMMY_STRING, 1);
839 spin_unlock_bh(&elm->lock);
841 netif_stop_queue(dev);
843 /* Give UART one final chance to flush. */
844 clear_bit(TTY_DO_WRITE_WAKEUP, &elm->tty->flags);
845 flush_work(&elm->tx_work);
847 can_rx_offload_disable(&elm->offload);
848 elm->can.state = CAN_STATE_STOPPED;
849 can_rx_offload_del(&elm->offload);
855 /* Send a can_frame to a TTY. */
856 static netdev_tx_t can327_netdev_start_xmit(struct sk_buff *skb,
857 struct net_device *dev)
859 struct can327 *elm = netdev_priv(dev);
860 struct can_frame *frame = (struct can_frame *)skb->data;
862 if (can_dropped_invalid_skb(dev, skb))
865 /* This check will be part of can_dropped_invalid_skb()
868 if (elm->can.ctrlmode & CAN_CTRLMODE_LISTENONLY)
871 /* We shouldn't get here after a hardware fault:
872 * can_bus_off() calls netif_carrier_off()
874 if (elm->uart_side_failure) {
875 WARN_ON_ONCE(elm->uart_side_failure);
879 netif_stop_queue(dev);
881 /* BHs are already disabled, so no spin_lock_bh().
882 * See Documentation/networking/netdevices.txt
884 spin_lock(&elm->lock);
885 can327_send_frame(elm, frame);
886 spin_unlock(&elm->lock);
888 dev->stats.tx_packets++;
889 dev->stats.tx_bytes += frame->can_id & CAN_RTR_FLAG ? 0 : frame->len;
896 static const struct net_device_ops can327_netdev_ops = {
897 .ndo_open = can327_netdev_open,
898 .ndo_stop = can327_netdev_close,
899 .ndo_start_xmit = can327_netdev_start_xmit,
900 .ndo_change_mtu = can_change_mtu,
903 static bool can327_is_valid_rx_char(u8 c)
905 static const bool lut_char_is_valid['z'] = {
909 ['0'] = true, true, true, true, true,
910 ['5'] = true, true, true, true, true,
912 [CAN327_READY_CHAR] = true,
914 ['A'] = true, true, true, true, true, true, true,
915 ['H'] = true, true, true, true, true, true, true,
916 ['O'] = true, true, true, true, true, true, true,
917 ['V'] = true, true, true, true, true,
921 [CAN327_DUMMY_CHAR] = true,
923 BUILD_BUG_ON(CAN327_DUMMY_CHAR >= 'z');
925 return (c < ARRAY_SIZE(lut_char_is_valid) &&
926 lut_char_is_valid[c]);
929 /* Handle incoming ELM327 ASCII data.
930 * This will not be re-entered while running, but other ldisc
931 * functions may be called in parallel.
933 #if LINUX_VERSION_CODE < KERNEL_VERSION(5,14,0)
934 static void can327_ldisc_rx(struct tty_struct *tty,
935 const unsigned char *cp, char *fp, int count)
937 static void can327_ldisc_rx(struct tty_struct *tty,
938 const unsigned char *cp, const char *fp, int count)
941 struct can327 *elm = (struct can327 *)tty->disc_data;
942 size_t first_new_char_idx;
944 if (elm->uart_side_failure)
947 spin_lock_bh(&elm->lock);
949 /* Store old rxfill, so can327_parse_rxbuf() will have
950 * the option of skipping already checked characters.
952 first_new_char_idx = elm->rxfill;
954 while (count-- && elm->rxfill < CAN327_SIZE_RXBUF) {
956 netdev_err(elm->dev, "Error in received character stream. Check your wiring.");
958 can327_uart_side_failure(elm);
960 spin_unlock_bh(&elm->lock);
964 /* Ignore NUL characters, which the PIC microcontroller may
965 * inadvertently insert due to a known hardware bug.
966 * See ELM327 documentation, which refers to a Microchip PIC
970 /* Check for stray characters on the UART line.
971 * Likely caused by bad hardware.
973 if (!can327_is_valid_rx_char(*cp)) {
975 "Received illegal character %02x.\n",
977 can327_uart_side_failure(elm);
979 spin_unlock_bh(&elm->lock);
983 elm->rxbuf[elm->rxfill++] = *cp;
990 netdev_err(elm->dev, "Receive buffer overflowed. Bad chip or wiring? count = %i", count);
992 can327_uart_side_failure(elm);
994 spin_unlock_bh(&elm->lock);
998 can327_parse_rxbuf(elm, first_new_char_idx);
999 spin_unlock_bh(&elm->lock);
1002 /* Write out remaining transmit buffer.
1003 * Scheduled when TTY is writable.
1005 static void can327_ldisc_tx_worker(struct work_struct *work)
1007 struct can327 *elm = container_of(work, struct can327, tx_work);
1010 if (elm->uart_side_failure)
1013 spin_lock_bh(&elm->lock);
1016 written = elm->tty->ops->write(elm->tty, elm->txhead, elm->txleft);
1018 netdev_err(elm->dev,
1019 "Failed to write to tty %s.\n",
1021 can327_uart_side_failure(elm);
1023 spin_unlock_bh(&elm->lock);
1027 elm->txleft -= written;
1028 elm->txhead += written;
1032 clear_bit(TTY_DO_WRITE_WAKEUP, &elm->tty->flags);
1034 spin_unlock_bh(&elm->lock);
1037 /* Called by the driver when there's room for more data. */
1038 static void can327_ldisc_tx_wakeup(struct tty_struct *tty)
1040 struct can327 *elm = (struct can327 *)tty->disc_data;
1042 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 can327_bitrate_const[] = {
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 needed to use bitrate_const */
1061 static int can327_do_set_bittiming(struct net_device *netdev)
1066 static int can327_ldisc_open(struct tty_struct *tty)
1068 struct net_device *dev;
1072 if (!capable(CAP_NET_ADMIN))
1075 if (!tty->ops->write)
1078 dev = alloc_candev(sizeof(struct can327), 0);
1081 elm = netdev_priv(dev);
1083 /* Configure TTY interface */
1084 tty->receive_room = 65536; /* We don't flow control */
1085 spin_lock_init(&elm->lock);
1086 INIT_WORK(&elm->tx_work, can327_ldisc_tx_worker);
1088 /* Configure CAN metadata */
1089 elm->can.bitrate_const = can327_bitrate_const;
1090 elm->can.bitrate_const_cnt = ARRAY_SIZE(can327_bitrate_const);
1091 elm->can.do_set_bittiming = can327_do_set_bittiming;
1092 elm->can.ctrlmode_supported = CAN_CTRLMODE_LISTENONLY;
1094 /* Configure netdev interface */
1096 dev->netdev_ops = &can327_netdev_ops;
1098 /* Mark ldisc channel as alive */
1100 tty->disc_data = elm;
1103 err = register_candev(elm->dev);
1105 free_candev(elm->dev);
1109 netdev_info(elm->dev, "can327 on %s.\n", tty->name);
1114 /* Close down a can327 channel.
1115 * This means flushing out any pending queues, and then returning.
1116 * This call is serialized against other ldisc functions:
1117 * Once this is called, no other ldisc function of ours is entered.
1119 * We also use this function for a hangup event.
1121 static void can327_ldisc_close(struct tty_struct *tty)
1123 struct can327 *elm = (struct can327 *)tty->disc_data;
1125 /* unregister_netdev() calls .ndo_stop() so we don't have to.
1126 * Our .ndo_stop() also flushes the TTY write wakeup handler,
1127 * so we can safely set elm->tty = NULL after this.
1129 unregister_candev(elm->dev);
1131 /* Mark channel as dead */
1132 spin_lock_bh(&elm->lock);
1133 tty->disc_data = NULL;
1135 spin_unlock_bh(&elm->lock);
1137 netdev_info(elm->dev, "can327 off %s.\n", tty->name);
1139 free_candev(elm->dev);
1142 static int can327_ldisc_ioctl(struct tty_struct *tty,
1143 #if LINUX_VERSION_CODE < KERNEL_VERSION(5,17,0)
1146 unsigned int cmd, unsigned long arg)
1148 struct can327 *elm = (struct can327 *)tty->disc_data;
1153 tmp = strnlen(elm->dev->name, IFNAMSIZ - 1) + 1;
1154 if (copy_to_user((void __user *)arg, elm->dev->name, tmp))
1162 #if LINUX_VERSION_CODE < KERNEL_VERSION(5,16,0)
1163 return tty_mode_ioctl(tty, file, cmd, arg);
1165 return tty_mode_ioctl(tty, cmd, arg);
1170 static struct tty_ldisc_ops can327_ldisc = {
1171 .owner = THIS_MODULE,
1173 .num = N_DEVELOPMENT,
1174 .receive_buf = can327_ldisc_rx,
1175 .write_wakeup = can327_ldisc_tx_wakeup,
1176 .open = can327_ldisc_open,
1177 .close = can327_ldisc_close,
1178 .ioctl = can327_ldisc_ioctl,
1181 static int __init can327_init(void)
1185 #if LINUX_VERSION_CODE < KERNEL_VERSION(5,14,0)
1186 status = tty_register_ldisc(N_DEVELOPMENT, &can327_ldisc);
1188 status = tty_register_ldisc(&can327_ldisc);
1191 pr_err("Can't register line discipline\n");
1196 static void __exit can327_exit(void)
1198 /* This will only be called when all channels have been closed by
1199 * userspace - tty_ldisc.c takes care of the module's refcount.
1201 #if LINUX_VERSION_CODE < KERNEL_VERSION(5,14,0)
1204 status = tty_unregister_ldisc(N_DEVELOPMENT);
1206 pr_err("Can't unregister line discipline (error: %d)\n",
1209 tty_unregister_ldisc(&can327_ldisc);
1213 module_init(can327_init);
1214 module_exit(can327_exit);
1216 MODULE_ALIAS_LDISC(N_DEVELOPMENT);
1217 MODULE_DESCRIPTION("ELM327 based CAN interface");
1218 MODULE_LICENSE("GPL");
1219 MODULE_AUTHOR("Max Staudt <max-linux@enpas.org>");