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) KBUILD_MODNAME ": " 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/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/rx-offload.h>
39 #define CAN327_NAPI_WEIGHT 4
41 #define CAN327_SIZE_TXBUF 32
42 #define CAN327_SIZE_RXBUF 1024
44 #define CAN327_CAN_CONFIG_SEND_SFF 0x8000
45 #define CAN327_CAN_CONFIG_VARIABLE_DLC 0x4000
46 #define CAN327_CAN_CONFIG_RECV_BOTH_SFF_EFF 0x2000
47 #define CAN327_CAN_CONFIG_BAUDRATE_MULT_8_7 0x1000
49 #define CAN327_DUMMY_CHAR 'y'
50 #define CAN327_DUMMY_STRING "y"
51 #define CAN327_READY_CHAR '>'
53 /* Bits in elm->cmds_todo */
55 CAN327_TX_DO_CAN_DATA = 0,
56 CAN327_TX_DO_CANID_11BIT,
57 CAN327_TX_DO_CANID_29BIT_LOW,
58 CAN327_TX_DO_CANID_29BIT_HIGH,
59 CAN327_TX_DO_CAN_CONFIG_PART2,
60 CAN327_TX_DO_CAN_CONFIG,
61 CAN327_TX_DO_RESPONSES,
62 CAN327_TX_DO_SILENT_MONITOR,
67 /* This must be the first member when using alloc_candev() */
70 struct can_rx_offload offload;
73 u8 txbuf[CAN327_SIZE_TXBUF];
74 u8 rxbuf[CAN327_SIZE_RXBUF];
76 /* Per-channel lock */
79 /* TTY and netdev devices that we're bridging */
80 struct tty_struct *tty;
81 struct net_device *dev;
83 /* TTY buffer accounting */
84 struct work_struct tx_work; /* Flushes TTY TX buffer */
85 u8 *txhead; /* Next TX byte */
86 size_t txleft; /* Bytes left to TX */
87 int rxfill; /* Bytes already RX'd in buffer */
91 CAN327_STATE_NOTINIT = 0,
92 CAN327_STATE_GETDUMMYCHAR,
93 CAN327_STATE_GETPROMPT,
94 CAN327_STATE_RECEIVING,
97 /* Things we have yet to send */
99 unsigned long cmds_todo;
101 /* The CAN frame and config the ELM327 is sending/using,
102 * or will send/use after finishing all cmds_todo
104 struct can_frame can_frame_to_send;
106 u8 can_bitrate_divisor;
111 /* Stop the channel on UART side hardware failure, e.g. stray
112 * characters or neverending lines. This may be caused by bad
113 * UART wiring, a bad ELM327, a bad UART bridge...
114 * Once this is true, nothing will be sent to the TTY.
116 bool uart_side_failure;
119 static inline void can327_uart_side_failure(struct can327 *elm);
121 static void can327_send(struct can327 *elm, const void *buf, size_t len)
125 lockdep_assert_held(&elm->lock);
127 if (elm->uart_side_failure)
130 memcpy(elm->txbuf, buf, len);
132 /* Order of next two lines is *very* important.
133 * When we are sending a little amount of data,
134 * the transfer may be completed inside the ops->write()
135 * routine, because it's running with interrupts enabled.
136 * In this case we *never* got WRITE_WAKEUP event,
137 * if we did not request it before write operation.
138 * 14 Oct 1994 Dmitry Gorodchanin.
140 set_bit(TTY_DO_WRITE_WAKEUP, &elm->tty->flags);
141 written = elm->tty->ops->write(elm->tty, elm->txbuf, len);
143 netdev_err(elm->dev, "Failed to write to tty %s.\n",
145 can327_uart_side_failure(elm);
149 elm->txleft = len - written;
150 elm->txhead = elm->txbuf + written;
153 /* Take the ELM327 out of almost any state and back into command mode.
154 * We send CAN327_DUMMY_CHAR which will either abort any running
155 * operation, or be echoed back to us in case we're already in command
158 static void can327_kick_into_cmd_mode(struct can327 *elm)
160 lockdep_assert_held(&elm->lock);
162 if (elm->state != CAN327_STATE_GETDUMMYCHAR &&
163 elm->state != CAN327_STATE_GETPROMPT) {
164 can327_send(elm, CAN327_DUMMY_STRING, 1);
166 elm->state = CAN327_STATE_GETDUMMYCHAR;
170 /* Schedule a CAN frame and necessary config changes to be sent to the TTY. */
171 static void can327_send_frame(struct can327 *elm, struct can_frame *frame)
173 lockdep_assert_held(&elm->lock);
175 /* Schedule any necessary changes in ELM327's CAN configuration */
176 if (elm->can_frame_to_send.can_id != frame->can_id) {
177 /* Set the new CAN ID for transmission. */
178 if ((frame->can_id ^ elm->can_frame_to_send.can_id)
181 (frame->can_id & CAN_EFF_FLAG ? 0 : CAN327_CAN_CONFIG_SEND_SFF) |
182 CAN327_CAN_CONFIG_VARIABLE_DLC |
183 CAN327_CAN_CONFIG_RECV_BOTH_SFF_EFF |
184 elm->can_bitrate_divisor;
186 set_bit(CAN327_TX_DO_CAN_CONFIG, &elm->cmds_todo);
189 if (frame->can_id & CAN_EFF_FLAG) {
190 clear_bit(CAN327_TX_DO_CANID_11BIT, &elm->cmds_todo);
191 set_bit(CAN327_TX_DO_CANID_29BIT_LOW, &elm->cmds_todo);
192 set_bit(CAN327_TX_DO_CANID_29BIT_HIGH, &elm->cmds_todo);
194 set_bit(CAN327_TX_DO_CANID_11BIT, &elm->cmds_todo);
195 clear_bit(CAN327_TX_DO_CANID_29BIT_LOW,
197 clear_bit(CAN327_TX_DO_CANID_29BIT_HIGH,
202 /* Schedule the CAN frame itself. */
203 elm->can_frame_to_send = *frame;
204 set_bit(CAN327_TX_DO_CAN_DATA, &elm->cmds_todo);
206 can327_kick_into_cmd_mode(elm);
209 /* ELM327 initialisation sequence.
210 * The line length is limited by the buffer in can327_handle_prompt().
212 static char *can327_init_script[] = {
213 "AT WS\r", /* v1.0: Warm Start */
214 "AT PP FF OFF\r", /* v1.0: All Programmable Parameters Off */
215 "AT M0\r", /* v1.0: Memory Off */
216 "AT AL\r", /* v1.0: Allow Long messages */
217 "AT BI\r", /* v1.0: Bypass Initialisation */
218 "AT CAF0\r", /* v1.0: CAN Auto Formatting Off */
219 "AT CFC0\r", /* v1.0: CAN Flow Control Off */
220 "AT CF 000\r", /* v1.0: Reset CAN ID Filter */
221 "AT CM 000\r", /* v1.0: Reset CAN ID Mask */
222 "AT E1\r", /* v1.0: Echo On */
223 "AT H1\r", /* v1.0: Headers On */
224 "AT L0\r", /* v1.0: Linefeeds Off */
225 "AT SH 7DF\r", /* v1.0: Set CAN sending ID to 0x7df */
226 "AT ST FF\r", /* v1.0: Set maximum Timeout for response after TX */
227 "AT AT0\r", /* v1.2: Adaptive Timing Off */
228 "AT D1\r", /* v1.3: Print DLC On */
229 "AT S1\r", /* v1.3: Spaces On */
230 "AT TP B\r", /* v1.0: Try Protocol B */
234 static void can327_init_device(struct can327 *elm)
236 lockdep_assert_held(&elm->lock);
238 elm->state = CAN327_STATE_NOTINIT;
239 elm->can_frame_to_send.can_id = 0x7df; /* ELM327 HW default */
241 elm->drop_next_line = 0;
243 /* We can only set the bitrate as a fraction of 500000.
244 * The bitrates listed in can327_bitrate_const will
245 * limit the user to the right values.
247 elm->can_bitrate_divisor = 500000 / elm->can.bittiming.bitrate;
249 CAN327_CAN_CONFIG_SEND_SFF | CAN327_CAN_CONFIG_VARIABLE_DLC |
250 CAN327_CAN_CONFIG_RECV_BOTH_SFF_EFF | elm->can_bitrate_divisor;
252 /* Configure ELM327 and then start monitoring */
253 elm->next_init_cmd = &can327_init_script[0];
254 set_bit(CAN327_TX_DO_INIT, &elm->cmds_todo);
255 set_bit(CAN327_TX_DO_SILENT_MONITOR, &elm->cmds_todo);
256 set_bit(CAN327_TX_DO_RESPONSES, &elm->cmds_todo);
257 set_bit(CAN327_TX_DO_CAN_CONFIG, &elm->cmds_todo);
259 can327_kick_into_cmd_mode(elm);
262 static void can327_feed_frame_to_netdev(struct can327 *elm, struct sk_buff *skb)
264 lockdep_assert_held(&elm->lock);
266 if (!netif_running(elm->dev))
269 /* Queue for NAPI pickup.
270 * rx-offload will update stats and LEDs for us.
272 if (can_rx_offload_queue_tail(&elm->offload, skb))
273 elm->dev->stats.rx_fifo_errors++;
276 can_rx_offload_irq_finish(&elm->offload);
279 /* Called when we're out of ideas and just want it all to end. */
280 static inline void can327_uart_side_failure(struct can327 *elm)
282 struct can_frame *frame;
285 lockdep_assert_held(&elm->lock);
287 elm->uart_side_failure = true;
289 clear_bit(TTY_DO_WRITE_WAKEUP, &elm->tty->flags);
291 elm->can.can_stats.bus_off++;
292 netif_stop_queue(elm->dev);
293 elm->can.state = CAN_STATE_BUS_OFF;
294 can_bus_off(elm->dev);
297 "ELM327 misbehaved. Blocking further communication.\n");
299 skb = alloc_can_err_skb(elm->dev, &frame);
303 frame->can_id |= CAN_ERR_BUSOFF;
304 can327_feed_frame_to_netdev(elm, skb);
307 /* Compares a byte buffer (non-NUL terminated) to the payload part of
308 * a string, and returns true iff the buffer (content *and* length) is
309 * exactly that string, without the terminating NUL byte.
311 * Example: If reference is "BUS ERROR", then this returns true iff nbytes == 9
312 * and !memcmp(buf, "BUS ERROR", 9).
314 * The reason to use strings is so we can easily include them in the C
315 * code, and to avoid hardcoding lengths.
317 static inline bool can327_rxbuf_cmp(const u8 *buf, size_t nbytes,
318 const char *reference)
320 size_t ref_len = strlen(reference);
322 return (nbytes == ref_len) && !memcmp(buf, reference, ref_len);
325 static void can327_parse_error(struct can327 *elm, size_t len)
327 struct can_frame *frame;
330 lockdep_assert_held(&elm->lock);
332 skb = alloc_can_err_skb(elm->dev, &frame);
334 /* It's okay to return here:
335 * The outer parsing loop will drop this UART buffer.
339 /* Filter possible error messages based on length of RX'd line */
340 if (can327_rxbuf_cmp(elm->rxbuf, len, "UNABLE TO CONNECT")) {
342 "ELM327 reported UNABLE TO CONNECT. Please check your setup.\n");
343 } else if (can327_rxbuf_cmp(elm->rxbuf, len, "BUFFER FULL")) {
344 /* This will only happen if the last data line was complete.
345 * Otherwise, can327_parse_frame() will heuristically
346 * emit this kind of error frame instead.
348 frame->can_id |= CAN_ERR_CRTL;
349 frame->data[1] = CAN_ERR_CRTL_RX_OVERFLOW;
350 } else if (can327_rxbuf_cmp(elm->rxbuf, len, "BUS ERROR")) {
351 frame->can_id |= CAN_ERR_BUSERROR;
352 } else if (can327_rxbuf_cmp(elm->rxbuf, len, "CAN ERROR")) {
353 frame->can_id |= CAN_ERR_PROT;
354 } else if (can327_rxbuf_cmp(elm->rxbuf, len, "<RX ERROR")) {
355 frame->can_id |= CAN_ERR_PROT;
356 } else if (can327_rxbuf_cmp(elm->rxbuf, len, "BUS BUSY")) {
357 frame->can_id |= CAN_ERR_PROT;
358 frame->data[2] = CAN_ERR_PROT_OVERLOAD;
359 } else if (can327_rxbuf_cmp(elm->rxbuf, len, "FB ERROR")) {
360 frame->can_id |= CAN_ERR_PROT;
361 frame->data[2] = CAN_ERR_PROT_TX;
362 } else if (len == 5 && !memcmp(elm->rxbuf, "ERR", 3)) {
363 /* ERR is followed by two digits, hence line length 5 */
364 netdev_err(elm->dev, "ELM327 reported an ERR%c%c. Please power it off and on again.\n",
365 elm->rxbuf[3], elm->rxbuf[4]);
366 frame->can_id |= CAN_ERR_CRTL;
368 /* Something else has happened.
369 * Maybe garbage on the UART line.
370 * Emit a generic error frame.
374 can327_feed_frame_to_netdev(elm, skb);
377 /* Parse CAN frames coming as ASCII from ELM327.
378 * They can be of various formats:
380 * 29-bit ID (EFF): 12 34 56 78 D PL PL PL PL PL PL PL PL
381 * 11-bit ID (!EFF): 123 D PL PL PL PL PL PL PL PL
383 * where D = DLC, PL = payload byte
385 * Instead of a payload, RTR indicates a remote request.
387 * We will use the spaces and line length to guess the format.
389 static int can327_parse_frame(struct can327 *elm, size_t len)
391 struct can_frame *frame;
397 lockdep_assert_held(&elm->lock);
399 skb = alloc_can_skb(elm->dev, &frame);
403 /* Find first non-hex and non-space character:
404 * - In the simplest case, there is none.
405 * - For RTR frames, 'R' is the first non-hex character.
406 * - An error message may replace the end of the data line.
408 for (hexlen = 0; hexlen <= len; hexlen++) {
409 if (hex_to_bin(elm->rxbuf[hexlen]) < 0 &&
410 elm->rxbuf[hexlen] != ' ') {
415 /* Sanity check whether the line is really a clean hexdump,
416 * or terminated by an error message, or contains garbage.
418 if (hexlen < len && !isdigit(elm->rxbuf[hexlen]) &&
419 !isupper(elm->rxbuf[hexlen]) && '<' != elm->rxbuf[hexlen] &&
420 ' ' != elm->rxbuf[hexlen]) {
421 /* The line is likely garbled anyway, so bail.
422 * The main code will restart listening.
428 /* Use spaces in CAN ID to distinguish 29 or 11 bit address length.
429 * No out-of-bounds access:
430 * We use the fact that we can always read from elm->rxbuf.
432 if (elm->rxbuf[2] == ' ' && elm->rxbuf[5] == ' ' &&
433 elm->rxbuf[8] == ' ' && elm->rxbuf[11] == ' ' &&
434 elm->rxbuf[13] == ' ') {
435 frame->can_id = CAN_EFF_FLAG;
437 } else if (elm->rxbuf[3] == ' ' && elm->rxbuf[5] == ' ') {
440 /* This is not a well-formatted data line.
441 * Assume it's an error message.
447 if (hexlen < datastart) {
448 /* The line is too short to be a valid frame hex dump.
449 * Something interrupted the hex dump or it is invalid.
455 /* From here on all chars up to buf[hexlen] are hex or spaces,
456 * at well-defined offsets.
459 /* Read CAN data length */
460 frame->len = (hex_to_bin(elm->rxbuf[datastart - 2]) << 0);
463 if (frame->can_id & CAN_EFF_FLAG) {
464 frame->can_id |= (hex_to_bin(elm->rxbuf[0]) << 28) |
465 (hex_to_bin(elm->rxbuf[1]) << 24) |
466 (hex_to_bin(elm->rxbuf[3]) << 20) |
467 (hex_to_bin(elm->rxbuf[4]) << 16) |
468 (hex_to_bin(elm->rxbuf[6]) << 12) |
469 (hex_to_bin(elm->rxbuf[7]) << 8) |
470 (hex_to_bin(elm->rxbuf[9]) << 4) |
471 (hex_to_bin(elm->rxbuf[10]) << 0);
473 frame->can_id |= (hex_to_bin(elm->rxbuf[0]) << 8) |
474 (hex_to_bin(elm->rxbuf[1]) << 4) |
475 (hex_to_bin(elm->rxbuf[2]) << 0);
478 /* Check for RTR frame */
479 if (elm->rxfill >= hexlen + 3 &&
480 !memcmp(&elm->rxbuf[hexlen], "RTR", 3)) {
481 frame->can_id |= CAN_RTR_FLAG;
484 /* Is the line long enough to hold the advertised payload?
485 * Note: RTR frames have a DLC, but no actual payload.
487 if (!(frame->can_id & CAN_RTR_FLAG) &&
488 (hexlen < frame->len * 3 + datastart)) {
490 * Probably the ELM327's RS232 TX buffer was full.
491 * Emit an error frame and exit.
493 frame->can_id = CAN_ERR_FLAG | CAN_ERR_CRTL;
494 frame->len = CAN_ERR_DLC;
495 frame->data[1] = CAN_ERR_CRTL_RX_OVERFLOW;
496 can327_feed_frame_to_netdev(elm, skb);
498 /* Signal failure to parse.
499 * The line will be re-parsed as an error line, which will fail.
500 * However, this will correctly drop the state machine back into
506 /* Parse the data nibbles. */
507 for (i = 0; i < frame->len; i++) {
509 (hex_to_bin(elm->rxbuf[datastart + 3 * i]) << 4) |
510 (hex_to_bin(elm->rxbuf[datastart + 3 * i + 1]));
513 /* Feed the frame to the network layer. */
514 can327_feed_frame_to_netdev(elm, skb);
519 static void can327_parse_line(struct can327 *elm, size_t len)
521 lockdep_assert_held(&elm->lock);
523 /* Skip empty lines */
527 /* Skip echo lines */
528 if (elm->drop_next_line) {
529 elm->drop_next_line = 0;
531 } else if (!memcmp(elm->rxbuf, "AT", 2)) {
535 /* Regular parsing */
536 if (elm->state == CAN327_STATE_RECEIVING &&
537 can327_parse_frame(elm, len)) {
538 /* Parse an error line. */
539 can327_parse_error(elm, len);
542 can327_kick_into_cmd_mode(elm);
546 static void can327_handle_prompt(struct can327 *elm)
548 struct can_frame *frame = &elm->can_frame_to_send;
549 /* Size this buffer for the largest ELM327 line we may generate,
550 * which is currently an 8 byte CAN frame's payload hexdump.
551 * Items in can327_init_script must fit here, too!
553 char local_txbuf[sizeof("0102030405060708\r")];
555 lockdep_assert_held(&elm->lock);
557 if (!elm->cmds_todo) {
558 /* Enter CAN monitor mode */
559 can327_send(elm, "ATMA\r", 5);
560 elm->state = CAN327_STATE_RECEIVING;
562 /* We will be in the default state once this command is
563 * sent, so enable the TX packet queue.
565 netif_wake_queue(elm->dev);
570 /* Reconfigure ELM327 step by step as indicated by elm->cmds_todo */
571 if (test_bit(CAN327_TX_DO_INIT, &elm->cmds_todo)) {
572 snprintf(local_txbuf, sizeof(local_txbuf), "%s",
573 *elm->next_init_cmd);
575 elm->next_init_cmd++;
576 if (!(*elm->next_init_cmd)) {
577 clear_bit(CAN327_TX_DO_INIT, &elm->cmds_todo);
581 } else if (test_and_clear_bit(CAN327_TX_DO_SILENT_MONITOR, &elm->cmds_todo)) {
582 snprintf(local_txbuf, sizeof(local_txbuf),
584 !!(elm->can.ctrlmode & CAN_CTRLMODE_LISTENONLY));
586 } else if (test_and_clear_bit(CAN327_TX_DO_RESPONSES, &elm->cmds_todo)) {
587 snprintf(local_txbuf, sizeof(local_txbuf),
589 !(elm->can.ctrlmode & CAN_CTRLMODE_LISTENONLY));
591 } else if (test_and_clear_bit(CAN327_TX_DO_CAN_CONFIG, &elm->cmds_todo)) {
592 snprintf(local_txbuf, sizeof(local_txbuf),
594 set_bit(CAN327_TX_DO_CAN_CONFIG_PART2, &elm->cmds_todo);
596 } else if (test_and_clear_bit(CAN327_TX_DO_CAN_CONFIG_PART2, &elm->cmds_todo)) {
597 snprintf(local_txbuf, sizeof(local_txbuf),
601 } else if (test_and_clear_bit(CAN327_TX_DO_CANID_29BIT_HIGH, &elm->cmds_todo)) {
602 snprintf(local_txbuf, sizeof(local_txbuf),
604 (frame->can_id & CAN_EFF_MASK) >> 24);
606 } else if (test_and_clear_bit(CAN327_TX_DO_CANID_29BIT_LOW, &elm->cmds_todo)) {
607 snprintf(local_txbuf, sizeof(local_txbuf),
609 frame->can_id & CAN_EFF_MASK & ((1 << 24) - 1));
611 } else if (test_and_clear_bit(CAN327_TX_DO_CANID_11BIT, &elm->cmds_todo)) {
612 snprintf(local_txbuf, sizeof(local_txbuf),
614 frame->can_id & CAN_SFF_MASK);
616 } else if (test_and_clear_bit(CAN327_TX_DO_CAN_DATA, &elm->cmds_todo)) {
617 if (frame->can_id & CAN_RTR_FLAG) {
618 /* Send an RTR frame. Their DLC is fixed.
619 * Some chips don't send them at all.
621 snprintf(local_txbuf, sizeof(local_txbuf), "ATRTR\r");
623 /* Send a regular CAN data frame */
626 for (i = 0; i < frame->len; i++) {
627 snprintf(&local_txbuf[2 * i],
628 sizeof(local_txbuf), "%02X",
632 snprintf(&local_txbuf[2 * i], sizeof(local_txbuf),
636 elm->drop_next_line = 1;
637 elm->state = CAN327_STATE_RECEIVING;
639 /* We will be in the default state once this command is
640 * sent, so enable the TX packet queue.
642 netif_wake_queue(elm->dev);
645 can327_send(elm, local_txbuf, strlen(local_txbuf));
648 static bool can327_is_ready_char(char c)
650 /* Bits 0xc0 are sometimes set (randomly), hence the mask.
651 * Probably bad hardware.
653 return (c & 0x3f) == CAN327_READY_CHAR;
656 static void can327_drop_bytes(struct can327 *elm, size_t i)
658 lockdep_assert_held(&elm->lock);
660 memmove(&elm->rxbuf[0], &elm->rxbuf[i], CAN327_SIZE_RXBUF - i);
664 static void can327_parse_rxbuf(struct can327 *elm, size_t first_new_char_idx)
668 lockdep_assert_held(&elm->lock);
670 switch (elm->state) {
671 case CAN327_STATE_NOTINIT:
675 case CAN327_STATE_GETDUMMYCHAR:
676 /* Wait for 'y' or '>' */
677 for (pos = 0; pos < elm->rxfill; pos++) {
678 if (elm->rxbuf[pos] == CAN327_DUMMY_CHAR) {
679 can327_send(elm, "\r", 1);
680 elm->state = CAN327_STATE_GETPROMPT;
683 } else if (can327_is_ready_char(elm->rxbuf[pos])) {
684 can327_send(elm, CAN327_DUMMY_STRING, 1);
690 can327_drop_bytes(elm, pos);
693 case CAN327_STATE_GETPROMPT:
695 if (can327_is_ready_char(elm->rxbuf[elm->rxfill - 1]))
696 can327_handle_prompt(elm);
701 case CAN327_STATE_RECEIVING:
702 /* Find <CR> delimiting feedback lines. */
703 len = first_new_char_idx;
704 while (len < elm->rxfill && elm->rxbuf[len] != '\r')
707 if (len == CAN327_SIZE_RXBUF) {
708 /* Assume the buffer ran full with garbage.
709 * Did we even connect at the right baud rate?
712 "RX buffer overflow. Faulty ELM327 or UART?\n");
713 can327_uart_side_failure(elm);
714 } else if (len == elm->rxfill) {
715 if (can327_is_ready_char(elm->rxbuf[elm->rxfill - 1])) {
716 /* The ELM327's AT ST response timeout ran out,
717 * so we got a prompt.
718 * Clear RX buffer and restart listening.
722 can327_handle_prompt(elm);
725 /* No <CR> found - we haven't received a full line yet.
726 * Wait for more data.
729 /* We have a full line to parse. */
730 can327_parse_line(elm, len);
732 /* Remove parsed data from RX buffer. */
733 can327_drop_bytes(elm, len + 1);
735 /* More data to parse? */
737 can327_parse_rxbuf(elm, 0);
742 static int can327_netdev_open(struct net_device *dev)
744 struct can327 *elm = netdev_priv(dev);
747 spin_lock_bh(&elm->lock);
750 spin_unlock_bh(&elm->lock);
754 if (elm->uart_side_failure)
755 netdev_warn(elm->dev,
756 "Reopening netdev after a UART side fault has been detected.\n");
758 /* Clear TTY buffers */
762 /* open_candev() checks for elm->can.bittiming.bitrate != 0 */
763 err = open_candev(dev);
765 spin_unlock_bh(&elm->lock);
769 can327_init_device(elm);
770 spin_unlock_bh(&elm->lock);
772 err = can_rx_offload_add_manual(dev, &elm->offload, CAN327_NAPI_WEIGHT);
778 can_rx_offload_enable(&elm->offload);
780 elm->can.state = CAN_STATE_ERROR_ACTIVE;
781 netif_start_queue(dev);
786 static int can327_netdev_close(struct net_device *dev)
788 struct can327 *elm = netdev_priv(dev);
790 /* Interrupt whatever the ELM327 is doing right now */
791 spin_lock_bh(&elm->lock);
792 can327_send(elm, CAN327_DUMMY_STRING, 1);
793 spin_unlock_bh(&elm->lock);
795 netif_stop_queue(dev);
797 /* Give UART one final chance to flush. */
798 clear_bit(TTY_DO_WRITE_WAKEUP, &elm->tty->flags);
799 flush_work(&elm->tx_work);
801 can_rx_offload_disable(&elm->offload);
802 elm->can.state = CAN_STATE_STOPPED;
803 can_rx_offload_del(&elm->offload);
809 /* Send a can_frame to a TTY. */
810 static netdev_tx_t can327_netdev_start_xmit(struct sk_buff *skb,
811 struct net_device *dev)
813 struct can327 *elm = netdev_priv(dev);
814 struct can_frame *frame = (struct can_frame *)skb->data;
816 if (can_dropped_invalid_skb(dev, skb))
819 /* We shouldn't get here after a hardware fault:
820 * can_bus_off() calls netif_carrier_off()
822 if (elm->uart_side_failure) {
823 WARN_ON_ONCE(elm->uart_side_failure);
827 netif_stop_queue(dev);
829 /* BHs are already disabled, so no spin_lock_bh().
830 * See Documentation/networking/netdevices.txt
832 spin_lock(&elm->lock);
833 can327_send_frame(elm, frame);
834 spin_unlock(&elm->lock);
836 dev->stats.tx_packets++;
837 dev->stats.tx_bytes += frame->can_id & CAN_RTR_FLAG ? 0 : frame->len;
844 static const struct net_device_ops can327_netdev_ops = {
845 .ndo_open = can327_netdev_open,
846 .ndo_stop = can327_netdev_close,
847 .ndo_start_xmit = can327_netdev_start_xmit,
848 .ndo_change_mtu = can_change_mtu,
851 static bool can327_is_valid_rx_char(u8 c)
853 static const bool lut_char_is_valid['z'] = {
857 ['0'] = true, true, true, true, true,
858 ['5'] = true, true, true, true, true,
860 [CAN327_READY_CHAR] = true,
862 ['A'] = true, true, true, true, true, true, true,
863 ['H'] = true, true, true, true, true, true, true,
864 ['O'] = true, true, true, true, true, true, true,
865 ['V'] = true, true, true, true, true,
869 [CAN327_DUMMY_CHAR] = true,
871 BUILD_BUG_ON(CAN327_DUMMY_CHAR >= 'z');
873 return (c < ARRAY_SIZE(lut_char_is_valid) && lut_char_is_valid[c]);
876 /* Handle incoming ELM327 ASCII data.
877 * This will not be re-entered while running, but other ldisc
878 * functions may be called in parallel.
880 static void can327_ldisc_rx(struct tty_struct *tty, const unsigned char *cp,
881 const char *fp, int count)
883 struct can327 *elm = (struct can327 *)tty->disc_data;
884 size_t first_new_char_idx;
886 if (elm->uart_side_failure)
889 spin_lock_bh(&elm->lock);
891 /* Store old rxfill, so can327_parse_rxbuf() will have
892 * the option of skipping already checked characters.
894 first_new_char_idx = elm->rxfill;
896 while (count-- && elm->rxfill < CAN327_SIZE_RXBUF) {
899 "Error in received character stream. Check your wiring.");
901 can327_uart_side_failure(elm);
903 spin_unlock_bh(&elm->lock);
907 /* Ignore NUL characters, which the PIC microcontroller may
908 * inadvertently insert due to a known hardware bug.
909 * See ELM327 documentation, which refers to a Microchip PIC
913 /* Check for stray characters on the UART line.
914 * Likely caused by bad hardware.
916 if (!can327_is_valid_rx_char(*cp)) {
918 "Received illegal character %02x.\n",
920 can327_uart_side_failure(elm);
922 spin_unlock_bh(&elm->lock);
926 elm->rxbuf[elm->rxfill++] = *cp;
934 "Receive buffer overflowed. Bad chip or wiring? count = %i",
937 can327_uart_side_failure(elm);
939 spin_unlock_bh(&elm->lock);
943 can327_parse_rxbuf(elm, first_new_char_idx);
944 spin_unlock_bh(&elm->lock);
947 /* Write out remaining transmit buffer.
948 * Scheduled when TTY is writable.
950 static void can327_ldisc_tx_worker(struct work_struct *work)
952 struct can327 *elm = container_of(work, struct can327, tx_work);
955 if (elm->uart_side_failure)
958 spin_lock_bh(&elm->lock);
961 written = elm->tty->ops->write(elm->tty, elm->txhead,
964 netdev_err(elm->dev, "Failed to write to tty %s.\n",
966 can327_uart_side_failure(elm);
968 spin_unlock_bh(&elm->lock);
972 elm->txleft -= written;
973 elm->txhead += written;
977 clear_bit(TTY_DO_WRITE_WAKEUP, &elm->tty->flags);
979 spin_unlock_bh(&elm->lock);
982 /* Called by the driver when there's room for more data. */
983 static void can327_ldisc_tx_wakeup(struct tty_struct *tty)
985 struct can327 *elm = (struct can327 *)tty->disc_data;
987 schedule_work(&elm->tx_work);
990 /* ELM327 can only handle bitrates that are integer divisors of 500 kHz,
991 * or 7/8 of that. Divisors are 1 to 64.
992 * Currently we don't implement support for 7/8 rates.
994 static const u32 can327_bitrate_const[] = {
995 7812, 7936, 8064, 8196, 8333, 8474, 8620, 8771,
996 8928, 9090, 9259, 9433, 9615, 9803, 10000, 10204,
997 10416, 10638, 10869, 11111, 11363, 11627, 11904, 12195,
998 12500, 12820, 13157, 13513, 13888, 14285, 14705, 15151,
999 15625, 16129, 16666, 17241, 17857, 18518, 19230, 20000,
1000 20833, 21739, 22727, 23809, 25000, 26315, 27777, 29411,
1001 31250, 33333, 35714, 38461, 41666, 45454, 50000, 55555,
1002 62500, 71428, 83333, 100000, 125000, 166666, 250000, 500000
1005 static int can327_ldisc_open(struct tty_struct *tty)
1007 struct net_device *dev;
1011 if (!capable(CAP_NET_ADMIN))
1014 if (!tty->ops->write)
1017 dev = alloc_candev(sizeof(struct can327), 0);
1020 elm = netdev_priv(dev);
1022 /* Configure TTY interface */
1023 tty->receive_room = 65536; /* We don't flow control */
1024 spin_lock_init(&elm->lock);
1025 INIT_WORK(&elm->tx_work, can327_ldisc_tx_worker);
1027 /* Configure CAN metadata */
1028 elm->can.bitrate_const = can327_bitrate_const;
1029 elm->can.bitrate_const_cnt = ARRAY_SIZE(can327_bitrate_const);
1030 elm->can.ctrlmode_supported = CAN_CTRLMODE_LISTENONLY;
1032 /* Configure netdev interface */
1034 dev->netdev_ops = &can327_netdev_ops;
1036 /* Mark ldisc channel as alive */
1038 tty->disc_data = elm;
1041 err = register_candev(elm->dev);
1043 free_candev(elm->dev);
1047 netdev_info(elm->dev, "can327 on %s.\n", tty->name);
1052 /* Close down a can327 channel.
1053 * This means flushing out any pending queues, and then returning.
1054 * This call is serialized against other ldisc functions:
1055 * Once this is called, no other ldisc function of ours is entered.
1057 * We also use this function for a hangup event.
1059 static void can327_ldisc_close(struct tty_struct *tty)
1061 struct can327 *elm = (struct can327 *)tty->disc_data;
1063 /* unregister_netdev() calls .ndo_stop() so we don't have to.
1064 * Our .ndo_stop() also flushes the TTY write wakeup handler,
1065 * so we can safely set elm->tty = NULL after this.
1067 unregister_candev(elm->dev);
1069 /* Mark channel as dead */
1070 spin_lock_bh(&elm->lock);
1071 tty->disc_data = NULL;
1073 spin_unlock_bh(&elm->lock);
1075 netdev_info(elm->dev, "can327 off %s.\n", tty->name);
1077 free_candev(elm->dev);
1080 static int can327_ldisc_ioctl(struct tty_struct *tty, unsigned int cmd,
1083 struct can327 *elm = (struct can327 *)tty->disc_data;
1088 tmp = strnlen(elm->dev->name, IFNAMSIZ - 1) + 1;
1089 if (copy_to_user((void __user *)arg, elm->dev->name, tmp))
1097 return tty_mode_ioctl(tty, cmd, arg);
1101 static struct tty_ldisc_ops can327_ldisc = {
1102 .owner = THIS_MODULE,
1103 .name = KBUILD_MODNAME,
1105 .receive_buf = can327_ldisc_rx,
1106 .write_wakeup = can327_ldisc_tx_wakeup,
1107 .open = can327_ldisc_open,
1108 .close = can327_ldisc_close,
1109 .ioctl = can327_ldisc_ioctl,
1112 static int __init can327_init(void)
1116 status = tty_register_ldisc(&can327_ldisc);
1118 pr_err("Can't register line discipline\n");
1123 static void __exit can327_exit(void)
1125 /* This will only be called when all channels have been closed by
1126 * userspace - tty_ldisc.c takes care of the module's refcount.
1128 tty_unregister_ldisc(&can327_ldisc);
1131 module_init(can327_init);
1132 module_exit(can327_exit);
1134 MODULE_ALIAS_LDISC(N_CAN327);
1135 MODULE_DESCRIPTION("ELM327 based CAN interface");
1136 MODULE_LICENSE("GPL");
1137 MODULE_AUTHOR("Max Staudt <max@enpas.org>");