1 // SPDX-License-Identifier: GPL-2.0
2 /* ELM327 based CAN interface driver (tty line discipline)
3 *
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.
6 *
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>
11 */
12
13 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
14
15 #include <linux/init.h>
16 #include <linux/module.h>
17
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>
31
32 #include <uapi/linux/tty.h>
33
34 #include <linux/can.h>
35 #include <linux/can/dev.h>
36 #include <linux/can/error.h>
37 #include <linux/can/rx-offload.h>
38
39 #define CAN327_NAPI_WEIGHT 4
40
41 #define CAN327_SIZE_TXBUF 32
42 #define CAN327_SIZE_RXBUF 1024
43
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
48
49 #define CAN327_DUMMY_CHAR 'y'
50 #define CAN327_DUMMY_STRING "y"
51 #define CAN327_READY_CHAR '>'
52
53 /* Bits in elm->cmds_todo */
54 enum can327_tx_do {
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,
63 CAN327_TX_DO_INIT,
64 };
65
66 struct can327 {
67 /* This must be the first member when using alloc_candev() */
68 struct can_priv can;
69
70 struct can_rx_offload offload;
71
72 /* TTY buffers */
73 u8 txbuf[CAN327_SIZE_TXBUF];
74 u8 rxbuf[CAN327_SIZE_RXBUF];
75
76 /* Per-channel lock */
77 spinlock_t lock;
78
79 /* TTY and netdev devices that we're bridging */
80 struct tty_struct *tty;
81 struct net_device *dev;
82
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 */
88
89 /* State machine */
90 enum {
91 CAN327_STATE_NOTINIT = 0,
92 CAN327_STATE_GETDUMMYCHAR,
93 CAN327_STATE_GETPROMPT,
94 CAN327_STATE_RECEIVING,
95 } state;
96
97 /* Things we have yet to send */
98 char **next_init_cmd;
99 unsigned long cmds_todo;
100
101 /* The CAN frame and config the ELM327 is sending/using,
102 * or will send/use after finishing all cmds_todo
103 */
104 struct can_frame can_frame_to_send;
105 u16 can_config;
106 u8 can_bitrate_divisor;
107
108 /* Parser state */
109 bool drop_next_line;
110
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.
115 */
116 bool uart_side_failure;
117 };
118
119 static inline void can327_uart_side_failure(struct can327 *elm);
120
can327_send(struct can327 * elm,const void * buf,size_t len)121 static void can327_send(struct can327 *elm, const void *buf, size_t len)
122 {
123 int written;
124
125 lockdep_assert_held(&elm->lock);
126
127 if (elm->uart_side_failure)
128 return;
129
130 memcpy(elm->txbuf, buf, len);
131
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.
139 */
140 set_bit(TTY_DO_WRITE_WAKEUP, &elm->tty->flags);
141 written = elm->tty->ops->write(elm->tty, elm->txbuf, len);
142 if (written < 0) {
143 netdev_err(elm->dev, "Failed to write to tty %s.\n",
144 elm->tty->name);
145 can327_uart_side_failure(elm);
146 return;
147 }
148
149 elm->txleft = len - written;
150 elm->txhead = elm->txbuf + written;
151 }
152
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
156 * mode.
157 */
can327_kick_into_cmd_mode(struct can327 * elm)158 static void can327_kick_into_cmd_mode(struct can327 *elm)
159 {
160 lockdep_assert_held(&elm->lock);
161
162 if (elm->state != CAN327_STATE_GETDUMMYCHAR &&
163 elm->state != CAN327_STATE_GETPROMPT) {
164 can327_send(elm, CAN327_DUMMY_STRING, 1);
165
166 elm->state = CAN327_STATE_GETDUMMYCHAR;
167 }
168 }
169
170 /* Schedule a CAN frame and necessary config changes to be sent to the TTY. */
can327_send_frame(struct can327 * elm,struct can_frame * frame)171 static void can327_send_frame(struct can327 *elm, struct can_frame *frame)
172 {
173 lockdep_assert_held(&elm->lock);
174
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)
179 & CAN_EFF_FLAG) {
180 elm->can_config =
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;
185
186 set_bit(CAN327_TX_DO_CAN_CONFIG, &elm->cmds_todo);
187 }
188
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);
193 } else {
194 set_bit(CAN327_TX_DO_CANID_11BIT, &elm->cmds_todo);
195 clear_bit(CAN327_TX_DO_CANID_29BIT_LOW,
196 &elm->cmds_todo);
197 clear_bit(CAN327_TX_DO_CANID_29BIT_HIGH,
198 &elm->cmds_todo);
199 }
200 }
201
202 /* Schedule the CAN frame itself. */
203 elm->can_frame_to_send = *frame;
204 set_bit(CAN327_TX_DO_CAN_DATA, &elm->cmds_todo);
205
206 can327_kick_into_cmd_mode(elm);
207 }
208
209 /* ELM327 initialisation sequence.
210 * The line length is limited by the buffer in can327_handle_prompt().
211 */
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 */
231 NULL
232 };
233
can327_init_device(struct can327 * elm)234 static void can327_init_device(struct can327 *elm)
235 {
236 lockdep_assert_held(&elm->lock);
237
238 elm->state = CAN327_STATE_NOTINIT;
239 elm->can_frame_to_send.can_id = 0x7df; /* ELM327 HW default */
240 elm->rxfill = 0;
241 elm->drop_next_line = 0;
242
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.
246 */
247 elm->can_bitrate_divisor = 500000 / elm->can.bittiming.bitrate;
248 elm->can_config =
249 CAN327_CAN_CONFIG_SEND_SFF | CAN327_CAN_CONFIG_VARIABLE_DLC |
250 CAN327_CAN_CONFIG_RECV_BOTH_SFF_EFF | elm->can_bitrate_divisor;
251
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);
258
259 can327_kick_into_cmd_mode(elm);
260 }
261
can327_feed_frame_to_netdev(struct can327 * elm,struct sk_buff * skb)262 static void can327_feed_frame_to_netdev(struct can327 *elm, struct sk_buff *skb)
263 {
264 lockdep_assert_held(&elm->lock);
265
266 if (!netif_running(elm->dev)) {
267 kfree_skb(skb);
268 return;
269 }
270
271 /* Queue for NAPI pickup.
272 * rx-offload will update stats and LEDs for us.
273 */
274 if (can_rx_offload_queue_tail(&elm->offload, skb))
275 elm->dev->stats.rx_fifo_errors++;
276
277 /* Wake NAPI */
278 can_rx_offload_irq_finish(&elm->offload);
279 }
280
281 /* Called when we're out of ideas and just want it all to end. */
can327_uart_side_failure(struct can327 * elm)282 static inline void can327_uart_side_failure(struct can327 *elm)
283 {
284 struct can_frame *frame;
285 struct sk_buff *skb;
286
287 lockdep_assert_held(&elm->lock);
288
289 elm->uart_side_failure = true;
290
291 clear_bit(TTY_DO_WRITE_WAKEUP, &elm->tty->flags);
292
293 elm->can.can_stats.bus_off++;
294 netif_stop_queue(elm->dev);
295 elm->can.state = CAN_STATE_BUS_OFF;
296 can_bus_off(elm->dev);
297
298 netdev_err(elm->dev,
299 "ELM327 misbehaved. Blocking further communication.\n");
300
301 skb = alloc_can_err_skb(elm->dev, &frame);
302 if (!skb)
303 return;
304
305 frame->can_id |= CAN_ERR_BUSOFF;
306 can327_feed_frame_to_netdev(elm, skb);
307 }
308
309 /* Compares a byte buffer (non-NUL terminated) to the payload part of
310 * a string, and returns true iff the buffer (content *and* length) is
311 * exactly that string, without the terminating NUL byte.
312 *
313 * Example: If reference is "BUS ERROR", then this returns true iff nbytes == 9
314 * and !memcmp(buf, "BUS ERROR", 9).
315 *
316 * The reason to use strings is so we can easily include them in the C
317 * code, and to avoid hardcoding lengths.
318 */
can327_rxbuf_cmp(const u8 * buf,size_t nbytes,const char * reference)319 static inline bool can327_rxbuf_cmp(const u8 *buf, size_t nbytes,
320 const char *reference)
321 {
322 size_t ref_len = strlen(reference);
323
324 return (nbytes == ref_len) && !memcmp(buf, reference, ref_len);
325 }
326
can327_parse_error(struct can327 * elm,size_t len)327 static void can327_parse_error(struct can327 *elm, size_t len)
328 {
329 struct can_frame *frame;
330 struct sk_buff *skb;
331
332 lockdep_assert_held(&elm->lock);
333
334 skb = alloc_can_err_skb(elm->dev, &frame);
335 if (!skb)
336 /* It's okay to return here:
337 * The outer parsing loop will drop this UART buffer.
338 */
339 return;
340
341 /* Filter possible error messages based on length of RX'd line */
342 if (can327_rxbuf_cmp(elm->rxbuf, len, "UNABLE TO CONNECT")) {
343 netdev_err(elm->dev,
344 "ELM327 reported UNABLE TO CONNECT. Please check your setup.\n");
345 } else if (can327_rxbuf_cmp(elm->rxbuf, len, "BUFFER FULL")) {
346 /* This will only happen if the last data line was complete.
347 * Otherwise, can327_parse_frame() will heuristically
348 * emit this kind of error frame instead.
349 */
350 frame->can_id |= CAN_ERR_CRTL;
351 frame->data[1] = CAN_ERR_CRTL_RX_OVERFLOW;
352 } else if (can327_rxbuf_cmp(elm->rxbuf, len, "BUS ERROR")) {
353 frame->can_id |= CAN_ERR_BUSERROR;
354 } else if (can327_rxbuf_cmp(elm->rxbuf, len, "CAN ERROR")) {
355 frame->can_id |= CAN_ERR_PROT;
356 } else if (can327_rxbuf_cmp(elm->rxbuf, len, "<RX ERROR")) {
357 frame->can_id |= CAN_ERR_PROT;
358 } else if (can327_rxbuf_cmp(elm->rxbuf, len, "BUS BUSY")) {
359 frame->can_id |= CAN_ERR_PROT;
360 frame->data[2] = CAN_ERR_PROT_OVERLOAD;
361 } else if (can327_rxbuf_cmp(elm->rxbuf, len, "FB ERROR")) {
362 frame->can_id |= CAN_ERR_PROT;
363 frame->data[2] = CAN_ERR_PROT_TX;
364 } else if (len == 5 && !memcmp(elm->rxbuf, "ERR", 3)) {
365 /* ERR is followed by two digits, hence line length 5 */
366 netdev_err(elm->dev, "ELM327 reported an ERR%c%c. Please power it off and on again.\n",
367 elm->rxbuf[3], elm->rxbuf[4]);
368 frame->can_id |= CAN_ERR_CRTL;
369 } else {
370 /* Something else has happened.
371 * Maybe garbage on the UART line.
372 * Emit a generic error frame.
373 */
374 }
375
376 can327_feed_frame_to_netdev(elm, skb);
377 }
378
379 /* Parse CAN frames coming as ASCII from ELM327.
380 * They can be of various formats:
381 *
382 * 29-bit ID (EFF): 12 34 56 78 D PL PL PL PL PL PL PL PL
383 * 11-bit ID (!EFF): 123 D PL PL PL PL PL PL PL PL
384 *
385 * where D = DLC, PL = payload byte
386 *
387 * Instead of a payload, RTR indicates a remote request.
388 *
389 * We will use the spaces and line length to guess the format.
390 */
can327_parse_frame(struct can327 * elm,size_t len)391 static int can327_parse_frame(struct can327 *elm, size_t len)
392 {
393 struct can_frame *frame;
394 struct sk_buff *skb;
395 int hexlen;
396 int datastart;
397 int i;
398
399 lockdep_assert_held(&elm->lock);
400
401 skb = alloc_can_skb(elm->dev, &frame);
402 if (!skb)
403 return -ENOMEM;
404
405 /* Find first non-hex and non-space character:
406 * - In the simplest case, there is none.
407 * - For RTR frames, 'R' is the first non-hex character.
408 * - An error message may replace the end of the data line.
409 */
410 for (hexlen = 0; hexlen <= len; hexlen++) {
411 if (hex_to_bin(elm->rxbuf[hexlen]) < 0 &&
412 elm->rxbuf[hexlen] != ' ') {
413 break;
414 }
415 }
416
417 /* Sanity check whether the line is really a clean hexdump,
418 * or terminated by an error message, or contains garbage.
419 */
420 if (hexlen < len && !isdigit(elm->rxbuf[hexlen]) &&
421 !isupper(elm->rxbuf[hexlen]) && '<' != elm->rxbuf[hexlen] &&
422 ' ' != elm->rxbuf[hexlen]) {
423 /* The line is likely garbled anyway, so bail.
424 * The main code will restart listening.
425 */
426 kfree_skb(skb);
427 return -ENODATA;
428 }
429
430 /* Use spaces in CAN ID to distinguish 29 or 11 bit address length.
431 * No out-of-bounds access:
432 * We use the fact that we can always read from elm->rxbuf.
433 */
434 if (elm->rxbuf[2] == ' ' && elm->rxbuf[5] == ' ' &&
435 elm->rxbuf[8] == ' ' && elm->rxbuf[11] == ' ' &&
436 elm->rxbuf[13] == ' ') {
437 frame->can_id = CAN_EFF_FLAG;
438 datastart = 14;
439 } else if (elm->rxbuf[3] == ' ' && elm->rxbuf[5] == ' ') {
440 datastart = 6;
441 } else {
442 /* This is not a well-formatted data line.
443 * Assume it's an error message.
444 */
445 kfree_skb(skb);
446 return -ENODATA;
447 }
448
449 if (hexlen < datastart) {
450 /* The line is too short to be a valid frame hex dump.
451 * Something interrupted the hex dump or it is invalid.
452 */
453 kfree_skb(skb);
454 return -ENODATA;
455 }
456
457 /* From here on all chars up to buf[hexlen] are hex or spaces,
458 * at well-defined offsets.
459 */
460
461 /* Read CAN data length */
462 frame->len = (hex_to_bin(elm->rxbuf[datastart - 2]) << 0);
463
464 /* Read CAN ID */
465 if (frame->can_id & CAN_EFF_FLAG) {
466 frame->can_id |= (hex_to_bin(elm->rxbuf[0]) << 28) |
467 (hex_to_bin(elm->rxbuf[1]) << 24) |
468 (hex_to_bin(elm->rxbuf[3]) << 20) |
469 (hex_to_bin(elm->rxbuf[4]) << 16) |
470 (hex_to_bin(elm->rxbuf[6]) << 12) |
471 (hex_to_bin(elm->rxbuf[7]) << 8) |
472 (hex_to_bin(elm->rxbuf[9]) << 4) |
473 (hex_to_bin(elm->rxbuf[10]) << 0);
474 } else {
475 frame->can_id |= (hex_to_bin(elm->rxbuf[0]) << 8) |
476 (hex_to_bin(elm->rxbuf[1]) << 4) |
477 (hex_to_bin(elm->rxbuf[2]) << 0);
478 }
479
480 /* Check for RTR frame */
481 if (elm->rxfill >= hexlen + 3 &&
482 !memcmp(&elm->rxbuf[hexlen], "RTR", 3)) {
483 frame->can_id |= CAN_RTR_FLAG;
484 }
485
486 /* Is the line long enough to hold the advertised payload?
487 * Note: RTR frames have a DLC, but no actual payload.
488 */
489 if (!(frame->can_id & CAN_RTR_FLAG) &&
490 (hexlen < frame->len * 3 + datastart)) {
491 /* Incomplete frame.
492 * Probably the ELM327's RS232 TX buffer was full.
493 * Emit an error frame and exit.
494 */
495 frame->can_id = CAN_ERR_FLAG | CAN_ERR_CRTL;
496 frame->len = CAN_ERR_DLC;
497 frame->data[1] = CAN_ERR_CRTL_RX_OVERFLOW;
498 can327_feed_frame_to_netdev(elm, skb);
499
500 /* Signal failure to parse.
501 * The line will be re-parsed as an error line, which will fail.
502 * However, this will correctly drop the state machine back into
503 * command mode.
504 */
505 return -ENODATA;
506 }
507
508 /* Parse the data nibbles. */
509 for (i = 0; i < frame->len; i++) {
510 frame->data[i] =
511 (hex_to_bin(elm->rxbuf[datastart + 3 * i]) << 4) |
512 (hex_to_bin(elm->rxbuf[datastart + 3 * i + 1]));
513 }
514
515 /* Feed the frame to the network layer. */
516 can327_feed_frame_to_netdev(elm, skb);
517
518 return 0;
519 }
520
can327_parse_line(struct can327 * elm,size_t len)521 static void can327_parse_line(struct can327 *elm, size_t len)
522 {
523 lockdep_assert_held(&elm->lock);
524
525 /* Skip empty lines */
526 if (!len)
527 return;
528
529 /* Skip echo lines */
530 if (elm->drop_next_line) {
531 elm->drop_next_line = 0;
532 return;
533 } else if (!memcmp(elm->rxbuf, "AT", 2)) {
534 return;
535 }
536
537 /* Regular parsing */
538 if (elm->state == CAN327_STATE_RECEIVING &&
539 can327_parse_frame(elm, len)) {
540 /* Parse an error line. */
541 can327_parse_error(elm, len);
542
543 /* Start afresh. */
544 can327_kick_into_cmd_mode(elm);
545 }
546 }
547
can327_handle_prompt(struct can327 * elm)548 static void can327_handle_prompt(struct can327 *elm)
549 {
550 struct can_frame *frame = &elm->can_frame_to_send;
551 /* Size this buffer for the largest ELM327 line we may generate,
552 * which is currently an 8 byte CAN frame's payload hexdump.
553 * Items in can327_init_script must fit here, too!
554 */
555 char local_txbuf[sizeof("0102030405060708\r")];
556
557 lockdep_assert_held(&elm->lock);
558
559 if (!elm->cmds_todo) {
560 /* Enter CAN monitor mode */
561 can327_send(elm, "ATMA\r", 5);
562 elm->state = CAN327_STATE_RECEIVING;
563
564 /* We will be in the default state once this command is
565 * sent, so enable the TX packet queue.
566 */
567 netif_wake_queue(elm->dev);
568
569 return;
570 }
571
572 /* Reconfigure ELM327 step by step as indicated by elm->cmds_todo */
573 if (test_bit(CAN327_TX_DO_INIT, &elm->cmds_todo)) {
574 snprintf(local_txbuf, sizeof(local_txbuf), "%s",
575 *elm->next_init_cmd);
576
577 elm->next_init_cmd++;
578 if (!(*elm->next_init_cmd)) {
579 clear_bit(CAN327_TX_DO_INIT, &elm->cmds_todo);
580 /* Init finished. */
581 }
582
583 } else if (test_and_clear_bit(CAN327_TX_DO_SILENT_MONITOR, &elm->cmds_todo)) {
584 snprintf(local_txbuf, sizeof(local_txbuf),
585 "ATCSM%i\r",
586 !!(elm->can.ctrlmode & CAN_CTRLMODE_LISTENONLY));
587
588 } else if (test_and_clear_bit(CAN327_TX_DO_RESPONSES, &elm->cmds_todo)) {
589 snprintf(local_txbuf, sizeof(local_txbuf),
590 "ATR%i\r",
591 !(elm->can.ctrlmode & CAN_CTRLMODE_LISTENONLY));
592
593 } else if (test_and_clear_bit(CAN327_TX_DO_CAN_CONFIG, &elm->cmds_todo)) {
594 snprintf(local_txbuf, sizeof(local_txbuf),
595 "ATPC\r");
596 set_bit(CAN327_TX_DO_CAN_CONFIG_PART2, &elm->cmds_todo);
597
598 } else if (test_and_clear_bit(CAN327_TX_DO_CAN_CONFIG_PART2, &elm->cmds_todo)) {
599 snprintf(local_txbuf, sizeof(local_txbuf),
600 "ATPB%04X\r",
601 elm->can_config);
602
603 } else if (test_and_clear_bit(CAN327_TX_DO_CANID_29BIT_HIGH, &elm->cmds_todo)) {
604 snprintf(local_txbuf, sizeof(local_txbuf),
605 "ATCP%02X\r",
606 (frame->can_id & CAN_EFF_MASK) >> 24);
607
608 } else if (test_and_clear_bit(CAN327_TX_DO_CANID_29BIT_LOW, &elm->cmds_todo)) {
609 snprintf(local_txbuf, sizeof(local_txbuf),
610 "ATSH%06X\r",
611 frame->can_id & CAN_EFF_MASK & ((1 << 24) - 1));
612
613 } else if (test_and_clear_bit(CAN327_TX_DO_CANID_11BIT, &elm->cmds_todo)) {
614 snprintf(local_txbuf, sizeof(local_txbuf),
615 "ATSH%03X\r",
616 frame->can_id & CAN_SFF_MASK);
617
618 } else if (test_and_clear_bit(CAN327_TX_DO_CAN_DATA, &elm->cmds_todo)) {
619 if (frame->can_id & CAN_RTR_FLAG) {
620 /* Send an RTR frame. Their DLC is fixed.
621 * Some chips don't send them at all.
622 */
623 snprintf(local_txbuf, sizeof(local_txbuf), "ATRTR\r");
624 } else {
625 /* Send a regular CAN data frame */
626 int i;
627
628 for (i = 0; i < frame->len; i++) {
629 snprintf(&local_txbuf[2 * i],
630 sizeof(local_txbuf), "%02X",
631 frame->data[i]);
632 }
633
634 snprintf(&local_txbuf[2 * i], sizeof(local_txbuf),
635 "\r");
636 }
637
638 elm->drop_next_line = 1;
639 elm->state = CAN327_STATE_RECEIVING;
640
641 /* We will be in the default state once this command is
642 * sent, so enable the TX packet queue.
643 */
644 netif_wake_queue(elm->dev);
645 }
646
647 can327_send(elm, local_txbuf, strlen(local_txbuf));
648 }
649
can327_is_ready_char(char c)650 static bool can327_is_ready_char(char c)
651 {
652 /* Bits 0xc0 are sometimes set (randomly), hence the mask.
653 * Probably bad hardware.
654 */
655 return (c & 0x3f) == CAN327_READY_CHAR;
656 }
657
can327_drop_bytes(struct can327 * elm,size_t i)658 static void can327_drop_bytes(struct can327 *elm, size_t i)
659 {
660 lockdep_assert_held(&elm->lock);
661
662 memmove(&elm->rxbuf[0], &elm->rxbuf[i], CAN327_SIZE_RXBUF - i);
663 elm->rxfill -= i;
664 }
665
can327_parse_rxbuf(struct can327 * elm,size_t first_new_char_idx)666 static void can327_parse_rxbuf(struct can327 *elm, size_t first_new_char_idx)
667 {
668 size_t len, pos;
669
670 lockdep_assert_held(&elm->lock);
671
672 switch (elm->state) {
673 case CAN327_STATE_NOTINIT:
674 elm->rxfill = 0;
675 break;
676
677 case CAN327_STATE_GETDUMMYCHAR:
678 /* Wait for 'y' or '>' */
679 for (pos = 0; pos < elm->rxfill; pos++) {
680 if (elm->rxbuf[pos] == CAN327_DUMMY_CHAR) {
681 can327_send(elm, "\r", 1);
682 elm->state = CAN327_STATE_GETPROMPT;
683 pos++;
684 break;
685 } else if (can327_is_ready_char(elm->rxbuf[pos])) {
686 can327_send(elm, CAN327_DUMMY_STRING, 1);
687 pos++;
688 break;
689 }
690 }
691
692 can327_drop_bytes(elm, pos);
693 break;
694
695 case CAN327_STATE_GETPROMPT:
696 /* Wait for '>' */
697 if (can327_is_ready_char(elm->rxbuf[elm->rxfill - 1]))
698 can327_handle_prompt(elm);
699
700 elm->rxfill = 0;
701 break;
702
703 case CAN327_STATE_RECEIVING:
704 /* Find <CR> delimiting feedback lines. */
705 len = first_new_char_idx;
706 while (len < elm->rxfill && elm->rxbuf[len] != '\r')
707 len++;
708
709 if (len == CAN327_SIZE_RXBUF) {
710 /* Assume the buffer ran full with garbage.
711 * Did we even connect at the right baud rate?
712 */
713 netdev_err(elm->dev,
714 "RX buffer overflow. Faulty ELM327 or UART?\n");
715 can327_uart_side_failure(elm);
716 } else if (len == elm->rxfill) {
717 if (can327_is_ready_char(elm->rxbuf[elm->rxfill - 1])) {
718 /* The ELM327's AT ST response timeout ran out,
719 * so we got a prompt.
720 * Clear RX buffer and restart listening.
721 */
722 elm->rxfill = 0;
723
724 can327_handle_prompt(elm);
725 }
726
727 /* No <CR> found - we haven't received a full line yet.
728 * Wait for more data.
729 */
730 } else {
731 /* We have a full line to parse. */
732 can327_parse_line(elm, len);
733
734 /* Remove parsed data from RX buffer. */
735 can327_drop_bytes(elm, len + 1);
736
737 /* More data to parse? */
738 if (elm->rxfill)
739 can327_parse_rxbuf(elm, 0);
740 }
741 }
742 }
743
can327_netdev_open(struct net_device * dev)744 static int can327_netdev_open(struct net_device *dev)
745 {
746 struct can327 *elm = netdev_priv(dev);
747 int err;
748
749 spin_lock_bh(&elm->lock);
750
751 if (!elm->tty) {
752 spin_unlock_bh(&elm->lock);
753 return -ENODEV;
754 }
755
756 if (elm->uart_side_failure)
757 netdev_warn(elm->dev,
758 "Reopening netdev after a UART side fault has been detected.\n");
759
760 /* Clear TTY buffers */
761 elm->rxfill = 0;
762 elm->txleft = 0;
763
764 /* open_candev() checks for elm->can.bittiming.bitrate != 0 */
765 err = open_candev(dev);
766 if (err) {
767 spin_unlock_bh(&elm->lock);
768 return err;
769 }
770
771 can327_init_device(elm);
772 spin_unlock_bh(&elm->lock);
773
774 err = can_rx_offload_add_manual(dev, &elm->offload, CAN327_NAPI_WEIGHT);
775 if (err) {
776 close_candev(dev);
777 return err;
778 }
779
780 can_rx_offload_enable(&elm->offload);
781
782 elm->can.state = CAN_STATE_ERROR_ACTIVE;
783 netif_start_queue(dev);
784
785 return 0;
786 }
787
can327_netdev_close(struct net_device * dev)788 static int can327_netdev_close(struct net_device *dev)
789 {
790 struct can327 *elm = netdev_priv(dev);
791
792 /* Interrupt whatever the ELM327 is doing right now */
793 spin_lock_bh(&elm->lock);
794 can327_send(elm, CAN327_DUMMY_STRING, 1);
795 spin_unlock_bh(&elm->lock);
796
797 netif_stop_queue(dev);
798
799 /* We don't flush the UART TX queue here, as we want final stop
800 * commands (like the above dummy char) to be flushed out.
801 */
802
803 can_rx_offload_disable(&elm->offload);
804 elm->can.state = CAN_STATE_STOPPED;
805 can_rx_offload_del(&elm->offload);
806 close_candev(dev);
807
808 return 0;
809 }
810
811 /* Send a can_frame to a TTY. */
can327_netdev_start_xmit(struct sk_buff * skb,struct net_device * dev)812 static netdev_tx_t can327_netdev_start_xmit(struct sk_buff *skb,
813 struct net_device *dev)
814 {
815 struct can327 *elm = netdev_priv(dev);
816 struct can_frame *frame = (struct can_frame *)skb->data;
817
818 if (can_dev_dropped_skb(dev, skb))
819 return NETDEV_TX_OK;
820
821 /* We shouldn't get here after a hardware fault:
822 * can_bus_off() calls netif_carrier_off()
823 */
824 if (elm->uart_side_failure) {
825 WARN_ON_ONCE(elm->uart_side_failure);
826 goto out;
827 }
828
829 netif_stop_queue(dev);
830
831 /* BHs are already disabled, so no spin_lock_bh().
832 * See Documentation/networking/netdevices.rst
833 */
834 spin_lock(&elm->lock);
835 can327_send_frame(elm, frame);
836 spin_unlock(&elm->lock);
837
838 dev->stats.tx_packets++;
839 dev->stats.tx_bytes += frame->can_id & CAN_RTR_FLAG ? 0 : frame->len;
840
841 skb_tx_timestamp(skb);
842
843 out:
844 kfree_skb(skb);
845 return NETDEV_TX_OK;
846 }
847
848 static const struct net_device_ops can327_netdev_ops = {
849 .ndo_open = can327_netdev_open,
850 .ndo_stop = can327_netdev_close,
851 .ndo_start_xmit = can327_netdev_start_xmit,
852 .ndo_change_mtu = can_change_mtu,
853 };
854
855 static const struct ethtool_ops can327_ethtool_ops = {
856 .get_ts_info = ethtool_op_get_ts_info,
857 };
858
can327_is_valid_rx_char(u8 c)859 static bool can327_is_valid_rx_char(u8 c)
860 {
861 static const bool lut_char_is_valid['z'] = {
862 ['\r'] = true,
863 [' '] = true,
864 ['.'] = true,
865 ['0'] = true, true, true, true, true,
866 ['5'] = true, true, true, true, true,
867 ['<'] = true,
868 [CAN327_READY_CHAR] = true,
869 ['?'] = true,
870 ['A'] = true, true, true, true, true, true, true,
871 ['H'] = true, true, true, true, true, true, true,
872 ['O'] = true, true, true, true, true, true, true,
873 ['V'] = true, true, true, true, true,
874 ['a'] = true,
875 ['b'] = true,
876 ['v'] = true,
877 [CAN327_DUMMY_CHAR] = true,
878 };
879 BUILD_BUG_ON(CAN327_DUMMY_CHAR >= 'z');
880
881 return (c < ARRAY_SIZE(lut_char_is_valid) && lut_char_is_valid[c]);
882 }
883
884 /* Handle incoming ELM327 ASCII data.
885 * This will not be re-entered while running, but other ldisc
886 * functions may be called in parallel.
887 */
can327_ldisc_rx(struct tty_struct * tty,const u8 * cp,const u8 * fp,size_t count)888 static void can327_ldisc_rx(struct tty_struct *tty, const u8 *cp,
889 const u8 *fp, size_t count)
890 {
891 struct can327 *elm = tty->disc_data;
892 size_t first_new_char_idx;
893
894 if (elm->uart_side_failure)
895 return;
896
897 spin_lock_bh(&elm->lock);
898
899 /* Store old rxfill, so can327_parse_rxbuf() will have
900 * the option of skipping already checked characters.
901 */
902 first_new_char_idx = elm->rxfill;
903
904 while (count--) {
905 if (elm->rxfill >= CAN327_SIZE_RXBUF) {
906 netdev_err(elm->dev,
907 "Receive buffer overflowed. Bad chip or wiring? count = %zu",
908 count);
909 goto uart_failure;
910 }
911 if (fp && *fp++) {
912 netdev_err(elm->dev,
913 "Error in received character stream. Check your wiring.");
914 goto uart_failure;
915 }
916
917 /* Ignore NUL characters, which the PIC microcontroller may
918 * inadvertently insert due to a known hardware bug.
919 * See ELM327 documentation, which refers to a Microchip PIC
920 * bug description.
921 */
922 if (*cp) {
923 /* Check for stray characters on the UART line.
924 * Likely caused by bad hardware.
925 */
926 if (!can327_is_valid_rx_char(*cp)) {
927 netdev_err(elm->dev,
928 "Received illegal character %02x.\n",
929 *cp);
930 goto uart_failure;
931 }
932
933 elm->rxbuf[elm->rxfill++] = *cp;
934 }
935
936 cp++;
937 }
938
939 can327_parse_rxbuf(elm, first_new_char_idx);
940 spin_unlock_bh(&elm->lock);
941
942 return;
943 uart_failure:
944 can327_uart_side_failure(elm);
945 spin_unlock_bh(&elm->lock);
946 }
947
948 /* Write out remaining transmit buffer.
949 * Scheduled when TTY is writable.
950 */
can327_ldisc_tx_worker(struct work_struct * work)951 static void can327_ldisc_tx_worker(struct work_struct *work)
952 {
953 struct can327 *elm = container_of(work, struct can327, tx_work);
954 ssize_t written;
955
956 if (elm->uart_side_failure)
957 return;
958
959 spin_lock_bh(&elm->lock);
960
961 if (elm->txleft) {
962 written = elm->tty->ops->write(elm->tty, elm->txhead,
963 elm->txleft);
964 if (written < 0) {
965 netdev_err(elm->dev, "Failed to write to tty %s.\n",
966 elm->tty->name);
967 can327_uart_side_failure(elm);
968
969 spin_unlock_bh(&elm->lock);
970 return;
971 }
972
973 elm->txleft -= written;
974 elm->txhead += written;
975 }
976
977 if (!elm->txleft)
978 clear_bit(TTY_DO_WRITE_WAKEUP, &elm->tty->flags);
979
980 spin_unlock_bh(&elm->lock);
981 }
982
983 /* Called by the driver when there's room for more data. */
can327_ldisc_tx_wakeup(struct tty_struct * tty)984 static void can327_ldisc_tx_wakeup(struct tty_struct *tty)
985 {
986 struct can327 *elm = tty->disc_data;
987
988 schedule_work(&elm->tx_work);
989 }
990
991 /* ELM327 can only handle bitrates that are integer divisors of 500 kHz,
992 * or 7/8 of that. Divisors are 1 to 64.
993 * Currently we don't implement support for 7/8 rates.
994 */
995 static const u32 can327_bitrate_const[] = {
996 7812, 7936, 8064, 8196, 8333, 8474, 8620, 8771,
997 8928, 9090, 9259, 9433, 9615, 9803, 10000, 10204,
998 10416, 10638, 10869, 11111, 11363, 11627, 11904, 12195,
999 12500, 12820, 13157, 13513, 13888, 14285, 14705, 15151,
1000 15625, 16129, 16666, 17241, 17857, 18518, 19230, 20000,
1001 20833, 21739, 22727, 23809, 25000, 26315, 27777, 29411,
1002 31250, 33333, 35714, 38461, 41666, 45454, 50000, 55555,
1003 62500, 71428, 83333, 100000, 125000, 166666, 250000, 500000
1004 };
1005
can327_ldisc_open(struct tty_struct * tty)1006 static int can327_ldisc_open(struct tty_struct *tty)
1007 {
1008 struct net_device *dev;
1009 struct can327 *elm;
1010 int err;
1011
1012 if (!capable(CAP_NET_ADMIN))
1013 return -EPERM;
1014
1015 if (!tty->ops->write)
1016 return -EOPNOTSUPP;
1017
1018 dev = alloc_candev(sizeof(struct can327), 0);
1019 if (!dev)
1020 return -ENFILE;
1021 elm = netdev_priv(dev);
1022
1023 /* Configure TTY interface */
1024 tty->receive_room = 65536; /* We don't flow control */
1025 spin_lock_init(&elm->lock);
1026 INIT_WORK(&elm->tx_work, can327_ldisc_tx_worker);
1027
1028 /* Configure CAN metadata */
1029 elm->can.bitrate_const = can327_bitrate_const;
1030 elm->can.bitrate_const_cnt = ARRAY_SIZE(can327_bitrate_const);
1031 elm->can.ctrlmode_supported = CAN_CTRLMODE_LISTENONLY;
1032
1033 /* Configure netdev interface */
1034 elm->dev = dev;
1035 dev->netdev_ops = &can327_netdev_ops;
1036 dev->ethtool_ops = &can327_ethtool_ops;
1037
1038 /* Mark ldisc channel as alive */
1039 elm->tty = tty;
1040 tty->disc_data = elm;
1041
1042 /* Let 'er rip */
1043 err = register_candev(elm->dev);
1044 if (err) {
1045 free_candev(elm->dev);
1046 return err;
1047 }
1048
1049 netdev_info(elm->dev, "can327 on %s.\n", tty->name);
1050
1051 return 0;
1052 }
1053
1054 /* Close down a can327 channel.
1055 * This means flushing out any pending queues, and then returning.
1056 * This call is serialized against other ldisc functions:
1057 * Once this is called, no other ldisc function of ours is entered.
1058 *
1059 * We also use this function for a hangup event.
1060 */
can327_ldisc_close(struct tty_struct * tty)1061 static void can327_ldisc_close(struct tty_struct *tty)
1062 {
1063 struct can327 *elm = tty->disc_data;
1064
1065 /* unregister_netdev() calls .ndo_stop() so we don't have to. */
1066 unregister_candev(elm->dev);
1067
1068 /* Give UART one final chance to flush.
1069 * No need to clear TTY_DO_WRITE_WAKEUP since .write_wakeup() is
1070 * serialised against .close() and will not be called once we return.
1071 */
1072 flush_work(&elm->tx_work);
1073
1074 /* Mark channel as dead */
1075 spin_lock_bh(&elm->lock);
1076 tty->disc_data = NULL;
1077 elm->tty = NULL;
1078 spin_unlock_bh(&elm->lock);
1079
1080 netdev_info(elm->dev, "can327 off %s.\n", tty->name);
1081
1082 free_candev(elm->dev);
1083 }
1084
can327_ldisc_ioctl(struct tty_struct * tty,unsigned int cmd,unsigned long arg)1085 static int can327_ldisc_ioctl(struct tty_struct *tty, unsigned int cmd,
1086 unsigned long arg)
1087 {
1088 struct can327 *elm = tty->disc_data;
1089 unsigned int tmp;
1090
1091 switch (cmd) {
1092 case SIOCGIFNAME:
1093 tmp = strnlen(elm->dev->name, IFNAMSIZ - 1) + 1;
1094 if (copy_to_user((void __user *)arg, elm->dev->name, tmp))
1095 return -EFAULT;
1096 return 0;
1097
1098 case SIOCSIFHWADDR:
1099 return -EINVAL;
1100
1101 default:
1102 return tty_mode_ioctl(tty, cmd, arg);
1103 }
1104 }
1105
1106 static struct tty_ldisc_ops can327_ldisc = {
1107 .owner = THIS_MODULE,
1108 .name = KBUILD_MODNAME,
1109 .num = N_CAN327,
1110 .receive_buf = can327_ldisc_rx,
1111 .write_wakeup = can327_ldisc_tx_wakeup,
1112 .open = can327_ldisc_open,
1113 .close = can327_ldisc_close,
1114 .ioctl = can327_ldisc_ioctl,
1115 };
1116
can327_init(void)1117 static int __init can327_init(void)
1118 {
1119 int status;
1120
1121 status = tty_register_ldisc(&can327_ldisc);
1122 if (status)
1123 pr_err("Can't register line discipline\n");
1124
1125 return status;
1126 }
1127
can327_exit(void)1128 static void __exit can327_exit(void)
1129 {
1130 /* This will only be called when all channels have been closed by
1131 * userspace - tty_ldisc.c takes care of the module's refcount.
1132 */
1133 tty_unregister_ldisc(&can327_ldisc);
1134 }
1135
1136 module_init(can327_init);
1137 module_exit(can327_exit);
1138
1139 MODULE_ALIAS_LDISC(N_CAN327);
1140 MODULE_DESCRIPTION("ELM327 based CAN interface");
1141 MODULE_LICENSE("GPL");
1142 MODULE_AUTHOR("Max Staudt <max@enpas.org>");
1143