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>
17 #include <linux/moduleparam.h>
19 #include <linux/atomic.h>
20 #include <linux/bitops.h>
21 #include <linux/ctype.h>
22 #include <linux/delay.h>
23 #include <linux/errno.h>
24 #include <linux/if_ether.h>
25 #include <linux/kernel.h>
26 #include <linux/list.h>
27 #include <linux/lockdep.h>
28 #include <linux/netdevice.h>
29 #include <linux/skbuff.h>
30 #include <linux/spinlock.h>
31 #include <linux/string.h>
32 #include <linux/tty.h>
33 #include <linux/tty_ldisc.h>
34 #include <linux/version.h>
35 #include <linux/workqueue.h>
37 #include <uapi/linux/tty.h>
39 #include <linux/can.h>
40 #include <linux/can/dev.h>
41 #include <linux/can/error.h>
42 #include <linux/can/led.h>
43 #include <linux/can/rx-offload.h>
45 /* Line discipline ID number.
46 * Starting with Linux v5.18-rc1, N_DEVELOPMENT is defined as 29:
47 * https://github.com/torvalds/linux/commit/c2faf737abfb10f88f2d2612d573e9edc3c42c37
50 #define N_DEVELOPMENT 29
53 /* Compatibility for Linux < 5.11 */
54 #if LINUX_VERSION_CODE < KERNEL_VERSION(5,11,0)
58 #define ELM327_NAPI_WEIGHT 4
60 #define ELM327_SIZE_RXBUF 224
61 #define ELM327_SIZE_TXBUF 32
63 #define ELM327_CAN_CONFIG_SEND_SFF 0x8000
64 #define ELM327_CAN_CONFIG_VARIABLE_DLC 0x4000
65 #define ELM327_CAN_CONFIG_RECV_BOTH_SFF_EFF 0x2000
66 #define ELM327_CAN_CONFIG_BAUDRATE_MULT_8_7 0x1000
68 #define ELM327_DUMMY_CHAR 'y'
69 #define ELM327_DUMMY_STRING "y"
70 #define ELM327_READY_CHAR '>'
72 /* Bits in elm->cmds_todo */
74 ELM327_TX_DO_CAN_DATA = 0,
75 ELM327_TX_DO_CANID_11BIT,
76 ELM327_TX_DO_CANID_29BIT_LOW,
77 ELM327_TX_DO_CANID_29BIT_HIGH,
78 ELM327_TX_DO_CAN_CONFIG_PART2,
79 ELM327_TX_DO_CAN_CONFIG,
80 ELM327_TX_DO_RESPONSES,
81 ELM327_TX_DO_SILENT_MONITOR,
86 /* This must be the first member when using alloc_candev() */
89 struct can_rx_offload offload;
92 u8 rxbuf[ELM327_SIZE_RXBUF];
93 u8 txbuf[ELM327_SIZE_TXBUF];
95 /* Per-channel lock */
98 /* TTY and netdev devices that we're bridging */
99 struct tty_struct *tty;
100 struct net_device *dev;
102 /* TTY buffer accounting */
103 struct work_struct tx_work; /* Flushes TTY TX buffer */
104 u8 *txhead; /* Next TX byte */
105 size_t txleft; /* Bytes left to TX */
106 int rxfill; /* Bytes already RX'd in buffer */
110 ELM327_STATE_NOTINIT = 0,
111 ELM327_STATE_GETDUMMYCHAR,
112 ELM327_STATE_GETPROMPT,
113 ELM327_STATE_RECEIVING,
116 /* Things we have yet to send */
117 char **next_init_cmd;
118 unsigned long cmds_todo;
120 /* The CAN frame and config the ELM327 is sending/using,
121 * or will send/use after finishing all cmds_todo
123 struct can_frame can_frame_to_send;
125 u8 can_bitrate_divisor;
130 /* Stop the channel on UART side hardware failure, e.g. stray
131 * characters or neverending lines. This may be caused by bad
132 * UART wiring, a bad ELM327, a bad UART bridge...
133 * Once this is true, nothing will be sent to the TTY.
135 bool uart_side_failure;
138 static inline void elm327_uart_side_failure(struct can327 *elm);
140 static void elm327_send(struct can327 *elm, const void *buf, size_t len)
144 lockdep_assert_held(&elm->lock);
146 if (elm->uart_side_failure)
149 memcpy(elm->txbuf, buf, len);
151 /* Order of next two lines is *very* important.
152 * When we are sending a little amount of data,
153 * the transfer may be completed inside the ops->write()
154 * routine, because it's running with interrupts enabled.
155 * In this case we *never* got WRITE_WAKEUP event,
156 * if we did not request it before write operation.
157 * 14 Oct 1994 Dmitry Gorodchanin.
159 set_bit(TTY_DO_WRITE_WAKEUP, &elm->tty->flags);
160 written = elm->tty->ops->write(elm->tty, elm->txbuf, len);
163 "Failed to write to tty %s.\n",
165 elm327_uart_side_failure(elm);
169 elm->txleft = len - written;
170 elm->txhead = elm->txbuf + written;
173 /* Take the ELM327 out of almost any state and back into command mode.
174 * We send ELM327_DUMMY_CHAR which will either abort any running
175 * operation, or be echoed back to us in case we're already in command
178 static void elm327_kick_into_cmd_mode(struct can327 *elm)
180 lockdep_assert_held(&elm->lock);
182 if (elm->state != ELM327_STATE_GETDUMMYCHAR &&
183 elm->state != ELM327_STATE_GETPROMPT) {
184 elm327_send(elm, ELM327_DUMMY_STRING, 1);
186 elm->state = ELM327_STATE_GETDUMMYCHAR;
190 /* Schedule a CAN frame and necessary config changes to be sent to the TTY. */
191 static void elm327_send_frame(struct can327 *elm, struct can_frame *frame)
193 lockdep_assert_held(&elm->lock);
195 /* Schedule any necessary changes in ELM327's CAN configuration */
196 if (elm->can_frame_to_send.can_id != frame->can_id) {
197 /* Set the new CAN ID for transmission. */
198 if ((frame->can_id ^ elm->can_frame_to_send.can_id)
200 elm->can_config = (frame->can_id & CAN_EFF_FLAG
202 : 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(ELM327_TX_DO_CAN_CONFIG, &elm->cmds_todo);
210 if (frame->can_id & CAN_EFF_FLAG) {
211 clear_bit(ELM327_TX_DO_CANID_11BIT, &elm->cmds_todo);
212 set_bit(ELM327_TX_DO_CANID_29BIT_LOW, &elm->cmds_todo);
213 set_bit(ELM327_TX_DO_CANID_29BIT_HIGH, &elm->cmds_todo);
215 set_bit(ELM327_TX_DO_CANID_11BIT, &elm->cmds_todo);
216 clear_bit(ELM327_TX_DO_CANID_29BIT_LOW, &elm->cmds_todo);
217 clear_bit(ELM327_TX_DO_CANID_29BIT_HIGH, &elm->cmds_todo);
221 /* Schedule the CAN frame itself. */
222 elm->can_frame_to_send = *frame;
223 set_bit(ELM327_TX_DO_CAN_DATA, &elm->cmds_todo);
225 elm327_kick_into_cmd_mode(elm);
228 /* ELM327 initialisation sequence.
229 * The line length is limited by the buffer in elm327_handle_prompt().
231 static char *elm327_init_script[] = {
232 "AT WS\r", /* v1.0: Warm Start */
233 "AT PP FF OFF\r", /* v1.0: All Programmable Parameters Off */
234 "AT M0\r", /* v1.0: Memory Off */
235 "AT AL\r", /* v1.0: Allow Long messages */
236 "AT BI\r", /* v1.0: Bypass Initialisation */
237 "AT CAF0\r", /* v1.0: CAN Auto Formatting Off */
238 "AT CFC0\r", /* v1.0: CAN Flow Control Off */
239 "AT CF 000\r", /* v1.0: Reset CAN ID Filter */
240 "AT CM 000\r", /* v1.0: Reset CAN ID Mask */
241 "AT E1\r", /* v1.0: Echo On */
242 "AT H1\r", /* v1.0: Headers On */
243 "AT L0\r", /* v1.0: Linefeeds Off */
244 "AT SH 7DF\r", /* v1.0: Set CAN sending ID to 0x7df */
245 "AT ST FF\r", /* v1.0: Set maximum Timeout for response after TX */
246 "AT AT0\r", /* v1.2: Adaptive Timing Off */
247 "AT D1\r", /* v1.3: Print DLC On */
248 "AT S1\r", /* v1.3: Spaces On */
249 "AT TP B\r", /* v1.0: Try Protocol B */
253 static void elm327_init(struct can327 *elm)
255 lockdep_assert_held(&elm->lock);
257 elm->state = ELM327_STATE_NOTINIT;
258 elm->can_frame_to_send.can_id = 0x7df; /* ELM327 HW default */
260 elm->drop_next_line = 0;
262 /* We can only set the bitrate as a fraction of 500000.
263 * The bit timing constants in can327_bittiming_const will
264 * limit the user to the right values.
266 elm->can_bitrate_divisor = 500000 / elm->can.bittiming.bitrate;
267 elm->can_config = ELM327_CAN_CONFIG_SEND_SFF
268 | ELM327_CAN_CONFIG_VARIABLE_DLC
269 | ELM327_CAN_CONFIG_RECV_BOTH_SFF_EFF
270 | elm->can_bitrate_divisor;
272 /* Configure ELM327 and then start monitoring */
273 elm->next_init_cmd = &elm327_init_script[0];
274 set_bit(ELM327_TX_DO_INIT, &elm->cmds_todo);
275 set_bit(ELM327_TX_DO_SILENT_MONITOR, &elm->cmds_todo);
276 set_bit(ELM327_TX_DO_RESPONSES, &elm->cmds_todo);
277 set_bit(ELM327_TX_DO_CAN_CONFIG, &elm->cmds_todo);
279 elm327_kick_into_cmd_mode(elm);
282 static void elm327_feed_frame_to_netdev(struct can327 *elm,
285 lockdep_assert_held(&elm->lock);
287 if (!netif_running(elm->dev))
290 /* Queue for NAPI pickup.
291 * rx-offload will update stats and LEDs for us.
293 if (can_rx_offload_queue_tail(&elm->offload, skb))
294 elm->dev->stats.rx_fifo_errors++;
296 #if LINUX_VERSION_CODE >= KERNEL_VERSION(5,15,0)
298 can_rx_offload_irq_finish(&elm->offload);
302 /* Called when we're out of ideas and just want it all to end. */
303 static inline void elm327_uart_side_failure(struct can327 *elm)
305 struct can_frame *frame;
308 lockdep_assert_held(&elm->lock);
310 elm->uart_side_failure = true;
312 clear_bit(TTY_DO_WRITE_WAKEUP, &elm->tty->flags);
314 elm->can.can_stats.bus_off++;
315 netif_stop_queue(elm->dev);
316 elm->can.state = CAN_STATE_BUS_OFF;
317 can_bus_off(elm->dev);
319 netdev_err(elm->dev, "ELM327 misbehaved. Blocking further communication.\n");
321 skb = alloc_can_err_skb(elm->dev, &frame);
325 frame->can_id |= CAN_ERR_BUSOFF;
326 elm327_feed_frame_to_netdev(elm, skb);
329 /* Compares a byte buffer (non-NUL terminated) to the payload part of a string,
330 * and returns true iff the buffer (content *and* length) is exactly that
331 * string, without the terminating NUL byte.
333 * Example: If reference is "BUS ERROR", then this returns true iff nbytes == 9
334 * and !memcmp(buf, "BUS ERROR", 9).
336 * The reason to use strings is so we can easily include them in the C code,
337 * and to avoid hardcoding lengths.
339 static inline bool elm327_rxbuf_cmp(const u8 *buf, size_t nbytes, const char *reference)
341 size_t ref_len = strlen(reference);
343 return (nbytes == ref_len) && !memcmp(buf, reference, ref_len);
346 static void elm327_parse_error(struct can327 *elm, size_t len)
348 struct can_frame *frame;
351 lockdep_assert_held(&elm->lock);
353 skb = alloc_can_err_skb(elm->dev, &frame);
355 /* It's okay to return here:
356 * The outer parsing loop will drop this UART buffer.
360 /* Filter possible error messages based on length of RX'd line */
361 if (elm327_rxbuf_cmp(elm->rxbuf, len, "UNABLE TO CONNECT")) {
363 "ELM327 reported UNABLE TO CONNECT. Please check your setup.\n");
364 } else if (elm327_rxbuf_cmp(elm->rxbuf, len, "BUFFER FULL")) {
365 /* This will only happen if the last data line was complete.
366 * Otherwise, elm327_parse_frame() will heuristically
367 * emit this kind of error frame instead.
369 frame->can_id |= CAN_ERR_CRTL;
370 frame->data[1] = CAN_ERR_CRTL_RX_OVERFLOW;
371 } else if (elm327_rxbuf_cmp(elm->rxbuf, len, "BUS ERROR")) {
372 frame->can_id |= CAN_ERR_BUSERROR;
373 } else if (elm327_rxbuf_cmp(elm->rxbuf, len, "CAN ERROR")) {
374 frame->can_id |= CAN_ERR_PROT;
375 } else if (elm327_rxbuf_cmp(elm->rxbuf, len, "<RX ERROR")) {
376 frame->can_id |= CAN_ERR_PROT;
377 } else if (elm327_rxbuf_cmp(elm->rxbuf, len, "BUS BUSY")) {
378 frame->can_id |= CAN_ERR_PROT;
379 frame->data[2] = CAN_ERR_PROT_OVERLOAD;
380 } else if (elm327_rxbuf_cmp(elm->rxbuf, len, "FB ERROR")) {
381 frame->can_id |= CAN_ERR_PROT;
382 frame->data[2] = CAN_ERR_PROT_TX;
383 } else if (len == 5 && !memcmp(elm->rxbuf, "ERR", 3)) {
384 /* ERR is followed by two digits, hence line length 5 */
385 netdev_err(elm->dev, "ELM327 reported an ERR%c%c. Please power it off and on again.\n",
386 elm->rxbuf[3], elm->rxbuf[4]);
387 frame->can_id |= CAN_ERR_CRTL;
389 /* Something else has happened.
390 * Maybe garbage on the UART line.
391 * Emit a generic error frame.
395 elm327_feed_frame_to_netdev(elm, skb);
398 /* Parse CAN frames coming as ASCII from ELM327.
399 * They can be of various formats:
401 * 29-bit ID (EFF): 12 34 56 78 D PL PL PL PL PL PL PL PL
402 * 11-bit ID (!EFF): 123 D PL PL PL PL PL PL PL PL
404 * where D = DLC, PL = payload byte
406 * Instead of a payload, RTR indicates a remote request.
408 * We will use the spaces and line length to guess the format.
410 static int elm327_parse_frame(struct can327 *elm, size_t len)
412 struct can_frame *frame;
418 lockdep_assert_held(&elm->lock);
420 skb = alloc_can_skb(elm->dev, &frame);
424 /* Find first non-hex and non-space character:
425 * - In the simplest case, there is none.
426 * - For RTR frames, 'R' is the first non-hex character.
427 * - An error message may replace the end of the data line.
429 for (hexlen = 0; hexlen <= len; hexlen++) {
430 if (hex_to_bin(elm->rxbuf[hexlen]) < 0 &&
431 elm->rxbuf[hexlen] != ' ') {
436 /* Sanity check whether the line is really a clean hexdump,
437 * or terminated by an error message, or contains garbage.
440 !isdigit(elm->rxbuf[hexlen]) &&
441 !isupper(elm->rxbuf[hexlen]) &&
442 '<' != elm->rxbuf[hexlen] &&
443 ' ' != elm->rxbuf[hexlen]) {
444 /* The line is likely garbled anyway, so bail.
445 * The main code will restart listening.
450 /* Use spaces in CAN ID to distinguish 29 or 11 bit address length.
451 * No out-of-bounds access:
452 * We use the fact that we can always read from elm->rxbuf.
454 if (elm->rxbuf[2] == ' ' && elm->rxbuf[5] == ' ' &&
455 elm->rxbuf[8] == ' ' && elm->rxbuf[11] == ' ' &&
456 elm->rxbuf[13] == ' ') {
457 frame->can_id = CAN_EFF_FLAG;
459 } else if (elm->rxbuf[3] == ' ' && elm->rxbuf[5] == ' ') {
462 /* This is not a well-formatted data line.
463 * Assume it's an error message.
468 if (hexlen < datastart) {
469 /* The line is too short to be a valid frame hex dump.
470 * Something interrupted the hex dump or it is invalid.
475 /* From here on all chars up to buf[hexlen] are hex or spaces,
476 * at well-defined offsets.
479 /* Read CAN data length */
480 frame->len = (hex_to_bin(elm->rxbuf[datastart - 2]) << 0);
483 if (frame->can_id & CAN_EFF_FLAG) {
484 frame->can_id |= (hex_to_bin(elm->rxbuf[0]) << 28)
485 | (hex_to_bin(elm->rxbuf[1]) << 24)
486 | (hex_to_bin(elm->rxbuf[3]) << 20)
487 | (hex_to_bin(elm->rxbuf[4]) << 16)
488 | (hex_to_bin(elm->rxbuf[6]) << 12)
489 | (hex_to_bin(elm->rxbuf[7]) << 8)
490 | (hex_to_bin(elm->rxbuf[9]) << 4)
491 | (hex_to_bin(elm->rxbuf[10]) << 0);
493 frame->can_id |= (hex_to_bin(elm->rxbuf[0]) << 8)
494 | (hex_to_bin(elm->rxbuf[1]) << 4)
495 | (hex_to_bin(elm->rxbuf[2]) << 0);
498 /* Check for RTR frame */
499 if (elm->rxfill >= hexlen + 3 &&
500 !memcmp(&elm->rxbuf[hexlen], "RTR", 3)) {
501 frame->can_id |= CAN_RTR_FLAG;
504 /* Is the line long enough to hold the advertised payload?
505 * Note: RTR frames have a DLC, but no actual payload.
507 if (!(frame->can_id & CAN_RTR_FLAG) &&
508 (hexlen < frame->len * 3 + datastart)) {
510 * Probably the ELM327's RS232 TX buffer was full.
511 * Emit an error frame and exit.
513 frame->can_id = CAN_ERR_FLAG | CAN_ERR_CRTL;
514 frame->len = CAN_ERR_DLC;
515 frame->data[1] = CAN_ERR_CRTL_RX_OVERFLOW;
516 elm327_feed_frame_to_netdev(elm, skb);
518 /* Signal failure to parse.
519 * The line will be re-parsed as an error line, which will fail.
520 * However, this will correctly drop the state machine back into
526 /* Parse the data nibbles. */
527 for (i = 0; i < frame->len; i++) {
528 frame->data[i] = (hex_to_bin(elm->rxbuf[datastart + 3*i]) << 4)
529 | (hex_to_bin(elm->rxbuf[datastart + 3*i + 1]));
532 /* Feed the frame to the network layer. */
533 elm327_feed_frame_to_netdev(elm, skb);
538 static void elm327_parse_line(struct can327 *elm, size_t len)
540 lockdep_assert_held(&elm->lock);
542 /* Skip empty lines */
546 /* Skip echo lines */
547 if (elm->drop_next_line) {
548 elm->drop_next_line = 0;
550 } else if (!memcmp(elm->rxbuf, "AT", 2)) {
554 /* Regular parsing */
555 if (elm->state == ELM327_STATE_RECEIVING &&
556 elm327_parse_frame(elm, len)) {
557 /* Parse an error line. */
558 elm327_parse_error(elm, len);
561 elm327_kick_into_cmd_mode(elm);
565 static void elm327_handle_prompt(struct can327 *elm)
567 struct can_frame *frame = &elm->can_frame_to_send;
568 /* Size this buffer for the largest ELM327 line we may generate,
569 * which is currently an 8 byte CAN frame's payload hexdump.
570 * Items in elm327_init_script must fit here, too!
572 char local_txbuf[sizeof("0102030405060708\r")];
574 lockdep_assert_held(&elm->lock);
576 if (!elm->cmds_todo) {
577 /* Enter CAN monitor mode */
578 elm327_send(elm, "ATMA\r", 5);
579 elm->state = ELM327_STATE_RECEIVING;
581 /* We will be in the default state once this command is
582 * sent, so enable the TX packet queue.
584 netif_wake_queue(elm->dev);
589 /* Reconfigure ELM327 step by step as indicated by elm->cmds_todo */
590 if (test_bit(ELM327_TX_DO_INIT, &elm->cmds_todo)) {
591 snprintf(local_txbuf, sizeof(local_txbuf),
593 *elm->next_init_cmd);
595 elm->next_init_cmd++;
596 if (!(*elm->next_init_cmd)) {
597 clear_bit(ELM327_TX_DO_INIT, &elm->cmds_todo);
601 } else if (test_and_clear_bit(ELM327_TX_DO_SILENT_MONITOR, &elm->cmds_todo)) {
602 snprintf(local_txbuf, sizeof(local_txbuf),
604 !!(elm->can.ctrlmode & CAN_CTRLMODE_LISTENONLY));
606 } else if (test_and_clear_bit(ELM327_TX_DO_RESPONSES, &elm->cmds_todo)) {
607 snprintf(local_txbuf, sizeof(local_txbuf),
609 !(elm->can.ctrlmode & CAN_CTRLMODE_LISTENONLY));
611 } else if (test_and_clear_bit(ELM327_TX_DO_CAN_CONFIG, &elm->cmds_todo)) {
612 snprintf(local_txbuf, sizeof(local_txbuf),
614 set_bit(ELM327_TX_DO_CAN_CONFIG_PART2, &elm->cmds_todo);
616 } else if (test_and_clear_bit(ELM327_TX_DO_CAN_CONFIG_PART2, &elm->cmds_todo)) {
617 snprintf(local_txbuf, sizeof(local_txbuf),
621 } else if (test_and_clear_bit(ELM327_TX_DO_CANID_29BIT_HIGH, &elm->cmds_todo)) {
622 snprintf(local_txbuf, sizeof(local_txbuf),
624 (frame->can_id & CAN_EFF_MASK) >> 24);
626 } else if (test_and_clear_bit(ELM327_TX_DO_CANID_29BIT_LOW, &elm->cmds_todo)) {
627 snprintf(local_txbuf, sizeof(local_txbuf),
629 frame->can_id & CAN_EFF_MASK & ((1 << 24) - 1));
631 } else if (test_and_clear_bit(ELM327_TX_DO_CANID_11BIT, &elm->cmds_todo)) {
632 snprintf(local_txbuf, sizeof(local_txbuf),
634 frame->can_id & CAN_SFF_MASK);
636 } else if (test_and_clear_bit(ELM327_TX_DO_CAN_DATA, &elm->cmds_todo)) {
637 if (frame->can_id & CAN_RTR_FLAG) {
638 /* Send an RTR frame. Their DLC is fixed.
639 * Some chips don't send them at all.
641 snprintf(local_txbuf, sizeof(local_txbuf),
644 /* Send a regular CAN data frame */
647 for (i = 0; i < frame->len; i++) {
648 snprintf(&local_txbuf[2 * i], sizeof(local_txbuf),
653 snprintf(&local_txbuf[2 * i], sizeof(local_txbuf),
657 elm->drop_next_line = 1;
658 elm->state = ELM327_STATE_RECEIVING;
660 /* We will be in the default state once this command is
661 * sent, so enable the TX packet queue.
663 netif_wake_queue(elm->dev);
666 elm327_send(elm, local_txbuf, strlen(local_txbuf));
669 static bool elm327_is_ready_char(char c)
671 /* Bits 0xc0 are sometimes set (randomly), hence the mask.
672 * Probably bad hardware.
674 return (c & 0x3f) == ELM327_READY_CHAR;
677 static void elm327_drop_bytes(struct can327 *elm, size_t i)
679 lockdep_assert_held(&elm->lock);
681 memmove(&elm->rxbuf[0], &elm->rxbuf[i], ELM327_SIZE_RXBUF - i);
685 static void elm327_parse_rxbuf(struct can327 *elm)
690 lockdep_assert_held(&elm->lock);
692 switch (elm->state) {
693 case ELM327_STATE_NOTINIT:
697 case ELM327_STATE_GETDUMMYCHAR:
698 /* Wait for 'y' or '>' */
699 for (i = 0; i < elm->rxfill; i++) {
700 if (elm->rxbuf[i] == ELM327_DUMMY_CHAR) {
701 elm327_send(elm, "\r", 1);
702 elm->state = ELM327_STATE_GETPROMPT;
705 } else if (elm327_is_ready_char(elm->rxbuf[i])) {
706 elm327_send(elm, ELM327_DUMMY_STRING, 1);
712 elm327_drop_bytes(elm, i);
715 case ELM327_STATE_GETPROMPT:
717 if (elm327_is_ready_char(elm->rxbuf[elm->rxfill - 1]))
718 elm327_handle_prompt(elm);
723 case ELM327_STATE_RECEIVING:
724 /* Find <CR> delimiting feedback lines. */
726 while (len < elm->rxfill && elm->rxbuf[len] != '\r')
729 if (len == ELM327_SIZE_RXBUF) {
730 /* Assume the buffer ran full with garbage.
731 * Did we even connect at the right baud rate?
734 "RX buffer overflow. Faulty ELM327 or UART?\n");
735 elm327_uart_side_failure(elm);
736 } else if (len == elm->rxfill) {
737 if (elm327_is_ready_char(elm->rxbuf[elm->rxfill - 1])) {
738 /* The ELM327's AT ST response timeout ran out,
739 * so we got a prompt.
740 * Clear RX buffer and restart listening.
744 elm327_handle_prompt(elm);
747 /* No <CR> found - we haven't received a full line yet.
748 * Wait for more data.
751 /* We have a full line to parse. */
752 elm327_parse_line(elm, len);
754 /* Remove parsed data from RX buffer. */
755 elm327_drop_bytes(elm, len + 1);
757 /* More data to parse? */
759 elm327_parse_rxbuf(elm);
764 #if LINUX_VERSION_CODE < KERNEL_VERSION(5,10,0)
765 /* Dummy needed to use can_rx_offload */
766 static struct sk_buff *can327_mailbox_read(struct can_rx_offload *offload,
767 unsigned int n, u32 *timestamp,
770 WARN_ON_ONCE(1); /* This function is a dummy, so don't call it! */
772 return ERR_PTR(-ENOBUFS);
776 static int can327_netdev_open(struct net_device *dev)
778 struct can327 *elm = netdev_priv(dev);
781 spin_lock_bh(&elm->lock);
784 spin_unlock_bh(&elm->lock);
788 if (elm->uart_side_failure)
789 netdev_warn(elm->dev, "Reopening netdev after a UART side fault has been detected.\n");
791 /* Clear TTY buffers */
795 /* open_candev() checks for elm->can.bittiming.bitrate != 0 */
796 err = open_candev(dev);
798 spin_unlock_bh(&elm->lock);
803 spin_unlock_bh(&elm->lock);
805 #if LINUX_VERSION_CODE < KERNEL_VERSION(5,10,0)
806 elm->offload.mailbox_read = can327_mailbox_read;
807 err = can_rx_offload_add_fifo(dev, &elm->offload, ELM327_NAPI_WEIGHT);
809 err = can_rx_offload_add_manual(dev, &elm->offload, ELM327_NAPI_WEIGHT);
816 can_rx_offload_enable(&elm->offload);
818 can_led_event(dev, CAN_LED_EVENT_OPEN);
819 elm->can.state = CAN_STATE_ERROR_ACTIVE;
820 netif_start_queue(dev);
825 static int can327_netdev_close(struct net_device *dev)
827 struct can327 *elm = netdev_priv(dev);
829 /* Interrupt whatever the ELM327 is doing right now */
830 spin_lock_bh(&elm->lock);
831 elm327_send(elm, ELM327_DUMMY_STRING, 1);
832 spin_unlock_bh(&elm->lock);
834 netif_stop_queue(dev);
836 /* Give UART one final chance to flush. */
837 clear_bit(TTY_DO_WRITE_WAKEUP, &elm->tty->flags);
838 flush_work(&elm->tx_work);
840 can_rx_offload_disable(&elm->offload);
841 elm->can.state = CAN_STATE_STOPPED;
842 can_rx_offload_del(&elm->offload);
844 can_led_event(dev, CAN_LED_EVENT_STOP);
849 /* Send a can_frame to a TTY. */
850 static netdev_tx_t can327_netdev_start_xmit(struct sk_buff *skb,
851 struct net_device *dev)
853 struct can327 *elm = netdev_priv(dev);
854 struct can_frame *frame = (struct can_frame *)skb->data;
856 if (can_dropped_invalid_skb(dev, skb))
859 /* This check will be part of can_dropped_invalid_skb()
862 if (elm->can.ctrlmode & CAN_CTRLMODE_LISTENONLY)
865 /* We shouldn't get here after a hardware fault:
866 * can_bus_off() calls netif_carrier_off()
868 if (elm->uart_side_failure) {
869 WARN_ON_ONCE(elm->uart_side_failure);
873 netif_stop_queue(dev);
875 /* BHs are already disabled, so no spin_lock_bh().
876 * See Documentation/networking/netdevices.txt
878 spin_lock(&elm->lock);
879 elm327_send_frame(elm, frame);
880 spin_unlock(&elm->lock);
882 dev->stats.tx_packets++;
883 dev->stats.tx_bytes += frame->len;
885 can_led_event(dev, CAN_LED_EVENT_TX);
892 static const struct net_device_ops can327_netdev_ops = {
893 .ndo_open = can327_netdev_open,
894 .ndo_stop = can327_netdev_close,
895 .ndo_start_xmit = can327_netdev_start_xmit,
896 .ndo_change_mtu = can_change_mtu,
899 static bool can327_is_valid_rx_char(u8 c)
901 static const bool lut_char_is_valid['z'] = {
905 ['0'] = true, true, true, true, true,
906 ['5'] = true, true, true, true, true,
908 [ELM327_READY_CHAR] = true,
910 ['A'] = true, true, true, true, true, true, true,
911 ['H'] = true, true, true, true, true, true, true,
912 ['O'] = true, true, true, true, true, true, true,
913 ['V'] = true, true, true, true, true,
917 [ELM327_DUMMY_CHAR] = true,
919 BUILD_BUG_ON(ELM327_DUMMY_CHAR >= 'z');
921 return (c < ARRAY_SIZE(lut_char_is_valid) &&
922 lut_char_is_valid[c]);
925 /* Handle incoming ELM327 ASCII data.
926 * This will not be re-entered while running, but other ldisc
927 * functions may be called in parallel.
929 #if LINUX_VERSION_CODE < KERNEL_VERSION(5,14,0)
930 static void can327_ldisc_rx(struct tty_struct *tty,
931 const unsigned char *cp, char *fp, int count)
933 static void can327_ldisc_rx(struct tty_struct *tty,
934 const unsigned char *cp, const char *fp, int count)
937 struct can327 *elm = (struct can327 *)tty->disc_data;
939 if (elm->uart_side_failure)
942 spin_lock_bh(&elm->lock);
944 while (count-- && elm->rxfill < ELM327_SIZE_RXBUF) {
946 netdev_err(elm->dev, "Error in received character stream. Check your wiring.");
948 elm327_uart_side_failure(elm);
950 spin_unlock_bh(&elm->lock);
954 /* Ignore NUL characters, which the PIC microcontroller may
955 * inadvertently insert due to a known hardware bug.
956 * See ELM327 documentation, which refers to a Microchip PIC
960 /* Check for stray characters on the UART line.
961 * Likely caused by bad hardware.
963 if (!can327_is_valid_rx_char(*cp)) {
965 "Received illegal character %02x.\n",
967 elm327_uart_side_failure(elm);
969 spin_unlock_bh(&elm->lock);
973 elm->rxbuf[elm->rxfill++] = *cp;
980 netdev_err(elm->dev, "Receive buffer overflowed. Bad chip or wiring?");
982 elm327_uart_side_failure(elm);
984 spin_unlock_bh(&elm->lock);
988 elm327_parse_rxbuf(elm);
989 spin_unlock_bh(&elm->lock);
992 /* Write out remaining transmit buffer.
993 * Scheduled when TTY is writable.
995 static void can327_ldisc_tx_worker(struct work_struct *work)
997 struct can327 *elm = container_of(work, struct can327, tx_work);
1000 if (elm->uart_side_failure)
1003 spin_lock_bh(&elm->lock);
1006 written = elm->tty->ops->write(elm->tty, elm->txhead, elm->txleft);
1008 netdev_err(elm->dev,
1009 "Failed to write to tty %s.\n",
1011 elm327_uart_side_failure(elm);
1013 spin_unlock_bh(&elm->lock);
1017 elm->txleft -= written;
1018 elm->txhead += written;
1022 clear_bit(TTY_DO_WRITE_WAKEUP, &elm->tty->flags);
1024 spin_unlock_bh(&elm->lock);
1027 /* Called by the driver when there's room for more data. */
1028 static void can327_ldisc_tx_wakeup(struct tty_struct *tty)
1030 struct can327 *elm = (struct can327 *)tty->disc_data;
1032 schedule_work(&elm->tx_work);
1035 /* ELM327 can only handle bitrates that are integer divisors of 500 kHz,
1036 * or 7/8 of that. Divisors are 1 to 64.
1037 * Currently we don't implement support for 7/8 rates.
1039 static const u32 can327_bitrate_const[64] = {
1040 7812, 7936, 8064, 8196, 8333, 8474, 8620, 8771,
1041 8928, 9090, 9259, 9433, 9615, 9803, 10000, 10204,
1042 10416, 10638, 10869, 11111, 11363, 11627, 11904, 12195,
1043 12500, 12820, 13157, 13513, 13888, 14285, 14705, 15151,
1044 15625, 16129, 16666, 17241, 17857, 18518, 19230, 20000,
1045 20833, 21739, 22727, 23809, 25000, 26315, 27777, 29411,
1046 31250, 33333, 35714, 38461, 41666, 45454, 50000, 55555,
1047 62500, 71428, 83333, 100000, 125000, 166666, 250000, 500000
1050 /* Dummy needed to use bitrate_const */
1051 static int can327_do_set_bittiming(struct net_device *netdev)
1056 static int can327_ldisc_open(struct tty_struct *tty)
1058 struct net_device *dev;
1062 if (!capable(CAP_NET_ADMIN))
1065 if (!tty->ops->write)
1068 dev = alloc_candev(sizeof(struct can327), 0);
1071 elm = netdev_priv(dev);
1073 /* Configure TTY interface */
1074 tty->receive_room = 65536; /* We don't flow control */
1075 spin_lock_init(&elm->lock);
1076 INIT_WORK(&elm->tx_work, can327_ldisc_tx_worker);
1078 /* Configure CAN metadata */
1079 elm->can.bitrate_const = can327_bitrate_const;
1080 elm->can.bitrate_const_cnt = ARRAY_SIZE(can327_bitrate_const);
1081 elm->can.do_set_bittiming = can327_do_set_bittiming;
1082 elm->can.ctrlmode_supported = CAN_CTRLMODE_LISTENONLY;
1084 /* Configure netdev interface */
1086 dev->netdev_ops = &can327_netdev_ops;
1088 /* Mark ldisc channel as alive */
1090 tty->disc_data = elm;
1092 devm_can_led_init(elm->dev);
1095 err = register_candev(elm->dev);
1097 free_candev(elm->dev);
1101 netdev_info(elm->dev, "can327 on %s.\n", tty->name);
1106 /* Close down a can327 channel.
1107 * This means flushing out any pending queues, and then returning.
1108 * This call is serialized against other ldisc functions:
1109 * Once this is called, no other ldisc function of ours is entered.
1111 * We also use this function for a hangup event.
1113 static void can327_ldisc_close(struct tty_struct *tty)
1115 struct can327 *elm = (struct can327 *)tty->disc_data;
1117 /* unregister_netdev() calls .ndo_stop() so we don't have to.
1118 * Our .ndo_stop() also flushes the TTY write wakeup handler,
1119 * so we can safely set elm->tty = NULL after this.
1121 unregister_candev(elm->dev);
1123 /* Mark channel as dead */
1124 spin_lock_bh(&elm->lock);
1125 tty->disc_data = NULL;
1127 spin_unlock_bh(&elm->lock);
1129 netdev_info(elm->dev, "can327 off %s.\n", tty->name);
1131 free_candev(elm->dev);
1134 static int can327_ldisc_ioctl(struct tty_struct *tty,
1135 #if LINUX_VERSION_CODE < KERNEL_VERSION(5,17,0)
1138 unsigned int cmd, unsigned long arg)
1140 struct can327 *elm = (struct can327 *)tty->disc_data;
1145 tmp = strnlen(elm->dev->name, IFNAMSIZ - 1) + 1;
1146 if (copy_to_user((void __user *)arg, elm->dev->name, tmp))
1154 #if LINUX_VERSION_CODE < KERNEL_VERSION(5,16,0)
1155 return tty_mode_ioctl(tty, file, cmd, arg);
1157 return tty_mode_ioctl(tty, cmd, arg);
1162 static struct tty_ldisc_ops can327_ldisc = {
1163 .owner = THIS_MODULE,
1165 .num = N_DEVELOPMENT,
1166 .receive_buf = can327_ldisc_rx,
1167 .write_wakeup = can327_ldisc_tx_wakeup,
1168 .open = can327_ldisc_open,
1169 .close = can327_ldisc_close,
1170 .ioctl = can327_ldisc_ioctl,
1173 static int __init can327_init(void)
1177 #if LINUX_VERSION_CODE < KERNEL_VERSION(5,14,0)
1178 status = tty_register_ldisc(N_DEVELOPMENT, &can327_ldisc);
1180 status = tty_register_ldisc(&can327_ldisc);
1183 pr_err("Can't register line discipline\n");
1188 static void __exit can327_exit(void)
1190 /* This will only be called when all channels have been closed by
1191 * userspace - tty_ldisc.c takes care of the module's refcount.
1193 #if LINUX_VERSION_CODE < KERNEL_VERSION(5,14,0)
1196 status = tty_unregister_ldisc(N_DEVELOPMENT);
1198 pr_err("Can't unregister line discipline (error: %d)\n",
1201 tty_unregister_ldisc(&can327_ldisc);
1205 module_init(can327_init);
1206 module_exit(can327_exit);
1208 MODULE_ALIAS_LDISC(N_DEVELOPMENT);
1209 MODULE_DESCRIPTION("ELM327 based CAN interface");
1210 MODULE_LICENSE("GPL");
1211 MODULE_AUTHOR("Max Staudt <max-linux@enpas.org>");