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); 120 121 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 */ 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. */ 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 }; 233 234 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 } 261 262 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 return; 268 269 /* Queue for NAPI pickup. 270 * rx-offload will update stats and LEDs for us. 271 */ 272 if (can_rx_offload_queue_tail(&elm->offload, skb)) 273 elm->dev->stats.rx_fifo_errors++; 274 275 /* Wake NAPI */ 276 can_rx_offload_irq_finish(&elm->offload); 277 } 278 279 /* 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) 281 { 282 struct can_frame *frame; 283 struct sk_buff *skb; 284 285 lockdep_assert_held(&elm->lock); 286 287 elm->uart_side_failure = true; 288 289 clear_bit(TTY_DO_WRITE_WAKEUP, &elm->tty->flags); 290 291 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); 295 296 netdev_err(elm->dev, 297 "ELM327 misbehaved. Blocking further communication.\n"); 298 299 skb = alloc_can_err_skb(elm->dev, &frame); 300 if (!skb) 301 return; 302 303 frame->can_id |= CAN_ERR_BUSOFF; 304 can327_feed_frame_to_netdev(elm, skb); 305 } 306 307 /* 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. 310 * 311 * Example: If reference is "BUS ERROR", then this returns true iff nbytes == 9 312 * and !memcmp(buf, "BUS ERROR", 9). 313 * 314 * The reason to use strings is so we can easily include them in the C 315 * code, and to avoid hardcoding lengths. 316 */ 317 static inline bool can327_rxbuf_cmp(const u8 *buf, size_t nbytes, 318 const char *reference) 319 { 320 size_t ref_len = strlen(reference); 321 322 return (nbytes == ref_len) && !memcmp(buf, reference, ref_len); 323 } 324 325 static void can327_parse_error(struct can327 *elm, size_t len) 326 { 327 struct can_frame *frame; 328 struct sk_buff *skb; 329 330 lockdep_assert_held(&elm->lock); 331 332 skb = alloc_can_err_skb(elm->dev, &frame); 333 if (!skb) 334 /* It's okay to return here: 335 * The outer parsing loop will drop this UART buffer. 336 */ 337 return; 338 339 /* Filter possible error messages based on length of RX'd line */ 340 if (can327_rxbuf_cmp(elm->rxbuf, len, "UNABLE TO CONNECT")) { 341 netdev_err(elm->dev, 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. 347 */ 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; 367 } else { 368 /* Something else has happened. 369 * Maybe garbage on the UART line. 370 * Emit a generic error frame. 371 */ 372 } 373 374 can327_feed_frame_to_netdev(elm, skb); 375 } 376 377 /* Parse CAN frames coming as ASCII from ELM327. 378 * They can be of various formats: 379 * 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 382 * 383 * where D = DLC, PL = payload byte 384 * 385 * Instead of a payload, RTR indicates a remote request. 386 * 387 * We will use the spaces and line length to guess the format. 388 */ 389 static int can327_parse_frame(struct can327 *elm, size_t len) 390 { 391 struct can_frame *frame; 392 struct sk_buff *skb; 393 int hexlen; 394 int datastart; 395 int i; 396 397 lockdep_assert_held(&elm->lock); 398 399 skb = alloc_can_skb(elm->dev, &frame); 400 if (!skb) 401 return -ENOMEM; 402 403 /* 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. 407 */ 408 for (hexlen = 0; hexlen <= len; hexlen++) { 409 if (hex_to_bin(elm->rxbuf[hexlen]) < 0 && 410 elm->rxbuf[hexlen] != ' ') { 411 break; 412 } 413 } 414 415 /* Sanity check whether the line is really a clean hexdump, 416 * or terminated by an error message, or contains garbage. 417 */ 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. 423 */ 424 kfree_skb(skb); 425 return -ENODATA; 426 } 427 428 /* 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. 431 */ 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; 436 datastart = 14; 437 } else if (elm->rxbuf[3] == ' ' && elm->rxbuf[5] == ' ') { 438 datastart = 6; 439 } else { 440 /* This is not a well-formatted data line. 441 * Assume it's an error message. 442 */ 443 kfree_skb(skb); 444 return -ENODATA; 445 } 446 447 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. 450 */ 451 kfree_skb(skb); 452 return -ENODATA; 453 } 454 455 /* From here on all chars up to buf[hexlen] are hex or spaces, 456 * at well-defined offsets. 457 */ 458 459 /* Read CAN data length */ 460 frame->len = (hex_to_bin(elm->rxbuf[datastart - 2]) << 0); 461 462 /* Read CAN ID */ 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); 472 } else { 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); 476 } 477 478 /* Check for RTR frame */ 479 if (elm->rxfill >= hexlen + 3 && 480 !memcmp(&elm->rxbuf[hexlen], "RTR", 3)) { 481 frame->can_id |= CAN_RTR_FLAG; 482 } 483 484 /* Is the line long enough to hold the advertised payload? 485 * Note: RTR frames have a DLC, but no actual payload. 486 */ 487 if (!(frame->can_id & CAN_RTR_FLAG) && 488 (hexlen < frame->len * 3 + datastart)) { 489 /* Incomplete frame. 490 * Probably the ELM327's RS232 TX buffer was full. 491 * Emit an error frame and exit. 492 */ 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); 497 498 /* 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 501 * command mode. 502 */ 503 return -ENODATA; 504 } 505 506 /* Parse the data nibbles. */ 507 for (i = 0; i < frame->len; i++) { 508 frame->data[i] = 509 (hex_to_bin(elm->rxbuf[datastart + 3 * i]) << 4) | 510 (hex_to_bin(elm->rxbuf[datastart + 3 * i + 1])); 511 } 512 513 /* Feed the frame to the network layer. */ 514 can327_feed_frame_to_netdev(elm, skb); 515 516 return 0; 517 } 518 519 static void can327_parse_line(struct can327 *elm, size_t len) 520 { 521 lockdep_assert_held(&elm->lock); 522 523 /* Skip empty lines */ 524 if (!len) 525 return; 526 527 /* Skip echo lines */ 528 if (elm->drop_next_line) { 529 elm->drop_next_line = 0; 530 return; 531 } else if (!memcmp(elm->rxbuf, "AT", 2)) { 532 return; 533 } 534 535 /* 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); 540 541 /* Start afresh. */ 542 can327_kick_into_cmd_mode(elm); 543 } 544 } 545 546 static void can327_handle_prompt(struct can327 *elm) 547 { 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! 552 */ 553 char local_txbuf[sizeof("0102030405060708\r")]; 554 555 lockdep_assert_held(&elm->lock); 556 557 if (!elm->cmds_todo) { 558 /* Enter CAN monitor mode */ 559 can327_send(elm, "ATMA\r", 5); 560 elm->state = CAN327_STATE_RECEIVING; 561 562 /* We will be in the default state once this command is 563 * sent, so enable the TX packet queue. 564 */ 565 netif_wake_queue(elm->dev); 566 567 return; 568 } 569 570 /* 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); 574 575 elm->next_init_cmd++; 576 if (!(*elm->next_init_cmd)) { 577 clear_bit(CAN327_TX_DO_INIT, &elm->cmds_todo); 578 /* Init finished. */ 579 } 580 581 } else if (test_and_clear_bit(CAN327_TX_DO_SILENT_MONITOR, &elm->cmds_todo)) { 582 snprintf(local_txbuf, sizeof(local_txbuf), 583 "ATCSM%i\r", 584 !!(elm->can.ctrlmode & CAN_CTRLMODE_LISTENONLY)); 585 586 } else if (test_and_clear_bit(CAN327_TX_DO_RESPONSES, &elm->cmds_todo)) { 587 snprintf(local_txbuf, sizeof(local_txbuf), 588 "ATR%i\r", 589 !(elm->can.ctrlmode & CAN_CTRLMODE_LISTENONLY)); 590 591 } else if (test_and_clear_bit(CAN327_TX_DO_CAN_CONFIG, &elm->cmds_todo)) { 592 snprintf(local_txbuf, sizeof(local_txbuf), 593 "ATPC\r"); 594 set_bit(CAN327_TX_DO_CAN_CONFIG_PART2, &elm->cmds_todo); 595 596 } else if (test_and_clear_bit(CAN327_TX_DO_CAN_CONFIG_PART2, &elm->cmds_todo)) { 597 snprintf(local_txbuf, sizeof(local_txbuf), 598 "ATPB%04X\r", 599 elm->can_config); 600 601 } else if (test_and_clear_bit(CAN327_TX_DO_CANID_29BIT_HIGH, &elm->cmds_todo)) { 602 snprintf(local_txbuf, sizeof(local_txbuf), 603 "ATCP%02X\r", 604 (frame->can_id & CAN_EFF_MASK) >> 24); 605 606 } else if (test_and_clear_bit(CAN327_TX_DO_CANID_29BIT_LOW, &elm->cmds_todo)) { 607 snprintf(local_txbuf, sizeof(local_txbuf), 608 "ATSH%06X\r", 609 frame->can_id & CAN_EFF_MASK & ((1 << 24) - 1)); 610 611 } else if (test_and_clear_bit(CAN327_TX_DO_CANID_11BIT, &elm->cmds_todo)) { 612 snprintf(local_txbuf, sizeof(local_txbuf), 613 "ATSH%03X\r", 614 frame->can_id & CAN_SFF_MASK); 615 616 } 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. 620 */ 621 snprintf(local_txbuf, sizeof(local_txbuf), "ATRTR\r"); 622 } else { 623 /* Send a regular CAN data frame */ 624 int i; 625 626 for (i = 0; i < frame->len; i++) { 627 snprintf(&local_txbuf[2 * i], 628 sizeof(local_txbuf), "%02X", 629 frame->data[i]); 630 } 631 632 snprintf(&local_txbuf[2 * i], sizeof(local_txbuf), 633 "\r"); 634 } 635 636 elm->drop_next_line = 1; 637 elm->state = CAN327_STATE_RECEIVING; 638 639 /* We will be in the default state once this command is 640 * sent, so enable the TX packet queue. 641 */ 642 netif_wake_queue(elm->dev); 643 } 644 645 can327_send(elm, local_txbuf, strlen(local_txbuf)); 646 } 647 648 static bool can327_is_ready_char(char c) 649 { 650 /* Bits 0xc0 are sometimes set (randomly), hence the mask. 651 * Probably bad hardware. 652 */ 653 return (c & 0x3f) == CAN327_READY_CHAR; 654 } 655 656 static void can327_drop_bytes(struct can327 *elm, size_t i) 657 { 658 lockdep_assert_held(&elm->lock); 659 660 memmove(&elm->rxbuf[0], &elm->rxbuf[i], CAN327_SIZE_RXBUF - i); 661 elm->rxfill -= i; 662 } 663 664 static void can327_parse_rxbuf(struct can327 *elm, size_t first_new_char_idx) 665 { 666 size_t len, pos; 667 668 lockdep_assert_held(&elm->lock); 669 670 switch (elm->state) { 671 case CAN327_STATE_NOTINIT: 672 elm->rxfill = 0; 673 break; 674 675 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; 681 pos++; 682 break; 683 } else if (can327_is_ready_char(elm->rxbuf[pos])) { 684 can327_send(elm, CAN327_DUMMY_STRING, 1); 685 pos++; 686 break; 687 } 688 } 689 690 can327_drop_bytes(elm, pos); 691 break; 692 693 case CAN327_STATE_GETPROMPT: 694 /* Wait for '>' */ 695 if (can327_is_ready_char(elm->rxbuf[elm->rxfill - 1])) 696 can327_handle_prompt(elm); 697 698 elm->rxfill = 0; 699 break; 700 701 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') 705 len++; 706 707 if (len == CAN327_SIZE_RXBUF) { 708 /* Assume the buffer ran full with garbage. 709 * Did we even connect at the right baud rate? 710 */ 711 netdev_err(elm->dev, 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. 719 */ 720 elm->rxfill = 0; 721 722 can327_handle_prompt(elm); 723 } 724 725 /* No <CR> found - we haven't received a full line yet. 726 * Wait for more data. 727 */ 728 } else { 729 /* We have a full line to parse. */ 730 can327_parse_line(elm, len); 731 732 /* Remove parsed data from RX buffer. */ 733 can327_drop_bytes(elm, len + 1); 734 735 /* More data to parse? */ 736 if (elm->rxfill) 737 can327_parse_rxbuf(elm, 0); 738 } 739 } 740 } 741 742 static int can327_netdev_open(struct net_device *dev) 743 { 744 struct can327 *elm = netdev_priv(dev); 745 int err; 746 747 spin_lock_bh(&elm->lock); 748 749 if (!elm->tty) { 750 spin_unlock_bh(&elm->lock); 751 return -ENODEV; 752 } 753 754 if (elm->uart_side_failure) 755 netdev_warn(elm->dev, 756 "Reopening netdev after a UART side fault has been detected.\n"); 757 758 /* Clear TTY buffers */ 759 elm->rxfill = 0; 760 elm->txleft = 0; 761 762 /* open_candev() checks for elm->can.bittiming.bitrate != 0 */ 763 err = open_candev(dev); 764 if (err) { 765 spin_unlock_bh(&elm->lock); 766 return err; 767 } 768 769 can327_init_device(elm); 770 spin_unlock_bh(&elm->lock); 771 772 err = can_rx_offload_add_manual(dev, &elm->offload, CAN327_NAPI_WEIGHT); 773 if (err) { 774 close_candev(dev); 775 return err; 776 } 777 778 can_rx_offload_enable(&elm->offload); 779 780 elm->can.state = CAN_STATE_ERROR_ACTIVE; 781 netif_start_queue(dev); 782 783 return 0; 784 } 785 786 static int can327_netdev_close(struct net_device *dev) 787 { 788 struct can327 *elm = netdev_priv(dev); 789 790 /* 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); 794 795 netif_stop_queue(dev); 796 797 /* Give UART one final chance to flush. */ 798 clear_bit(TTY_DO_WRITE_WAKEUP, &elm->tty->flags); 799 flush_work(&elm->tx_work); 800 801 can_rx_offload_disable(&elm->offload); 802 elm->can.state = CAN_STATE_STOPPED; 803 can_rx_offload_del(&elm->offload); 804 close_candev(dev); 805 806 return 0; 807 } 808 809 /* 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) 812 { 813 struct can327 *elm = netdev_priv(dev); 814 struct can_frame *frame = (struct can_frame *)skb->data; 815 816 if (can_dropped_invalid_skb(dev, skb)) 817 return NETDEV_TX_OK; 818 819 /* We shouldn't get here after a hardware fault: 820 * can_bus_off() calls netif_carrier_off() 821 */ 822 if (elm->uart_side_failure) { 823 WARN_ON_ONCE(elm->uart_side_failure); 824 goto out; 825 } 826 827 netif_stop_queue(dev); 828 829 /* BHs are already disabled, so no spin_lock_bh(). 830 * See Documentation/networking/netdevices.rst 831 */ 832 spin_lock(&elm->lock); 833 can327_send_frame(elm, frame); 834 spin_unlock(&elm->lock); 835 836 dev->stats.tx_packets++; 837 dev->stats.tx_bytes += frame->can_id & CAN_RTR_FLAG ? 0 : frame->len; 838 839 skb_tx_timestamp(skb); 840 841 out: 842 kfree_skb(skb); 843 return NETDEV_TX_OK; 844 } 845 846 static const struct net_device_ops can327_netdev_ops = { 847 .ndo_open = can327_netdev_open, 848 .ndo_stop = can327_netdev_close, 849 .ndo_start_xmit = can327_netdev_start_xmit, 850 .ndo_change_mtu = can_change_mtu, 851 }; 852 853 static const struct ethtool_ops can327_ethtool_ops = { 854 .get_ts_info = ethtool_op_get_ts_info, 855 }; 856 857 static bool can327_is_valid_rx_char(u8 c) 858 { 859 static const bool lut_char_is_valid['z'] = { 860 ['\r'] = true, 861 [' '] = true, 862 ['.'] = true, 863 ['0'] = true, true, true, true, true, 864 ['5'] = true, true, true, true, true, 865 ['<'] = true, 866 [CAN327_READY_CHAR] = true, 867 ['?'] = true, 868 ['A'] = true, true, true, true, true, true, true, 869 ['H'] = true, true, true, true, true, true, true, 870 ['O'] = true, true, true, true, true, true, true, 871 ['V'] = true, true, true, true, true, 872 ['a'] = true, 873 ['b'] = true, 874 ['v'] = true, 875 [CAN327_DUMMY_CHAR] = true, 876 }; 877 BUILD_BUG_ON(CAN327_DUMMY_CHAR >= 'z'); 878 879 return (c < ARRAY_SIZE(lut_char_is_valid) && lut_char_is_valid[c]); 880 } 881 882 /* Handle incoming ELM327 ASCII data. 883 * This will not be re-entered while running, but other ldisc 884 * functions may be called in parallel. 885 */ 886 static void can327_ldisc_rx(struct tty_struct *tty, const unsigned char *cp, 887 const char *fp, int count) 888 { 889 struct can327 *elm = (struct can327 *)tty->disc_data; 890 size_t first_new_char_idx; 891 892 if (elm->uart_side_failure) 893 return; 894 895 spin_lock_bh(&elm->lock); 896 897 /* Store old rxfill, so can327_parse_rxbuf() will have 898 * the option of skipping already checked characters. 899 */ 900 first_new_char_idx = elm->rxfill; 901 902 while (count-- && elm->rxfill < CAN327_SIZE_RXBUF) { 903 if (fp && *fp++) { 904 netdev_err(elm->dev, 905 "Error in received character stream. Check your wiring."); 906 907 can327_uart_side_failure(elm); 908 909 spin_unlock_bh(&elm->lock); 910 return; 911 } 912 913 /* Ignore NUL characters, which the PIC microcontroller may 914 * inadvertently insert due to a known hardware bug. 915 * See ELM327 documentation, which refers to a Microchip PIC 916 * bug description. 917 */ 918 if (*cp) { 919 /* Check for stray characters on the UART line. 920 * Likely caused by bad hardware. 921 */ 922 if (!can327_is_valid_rx_char(*cp)) { 923 netdev_err(elm->dev, 924 "Received illegal character %02x.\n", 925 *cp); 926 can327_uart_side_failure(elm); 927 928 spin_unlock_bh(&elm->lock); 929 return; 930 } 931 932 elm->rxbuf[elm->rxfill++] = *cp; 933 } 934 935 cp++; 936 } 937 938 if (count >= 0) { 939 netdev_err(elm->dev, 940 "Receive buffer overflowed. Bad chip or wiring? count = %i", 941 count); 942 943 can327_uart_side_failure(elm); 944 945 spin_unlock_bh(&elm->lock); 946 return; 947 } 948 949 can327_parse_rxbuf(elm, first_new_char_idx); 950 spin_unlock_bh(&elm->lock); 951 } 952 953 /* Write out remaining transmit buffer. 954 * Scheduled when TTY is writable. 955 */ 956 static void can327_ldisc_tx_worker(struct work_struct *work) 957 { 958 struct can327 *elm = container_of(work, struct can327, tx_work); 959 ssize_t written; 960 961 if (elm->uart_side_failure) 962 return; 963 964 spin_lock_bh(&elm->lock); 965 966 if (elm->txleft) { 967 written = elm->tty->ops->write(elm->tty, elm->txhead, 968 elm->txleft); 969 if (written < 0) { 970 netdev_err(elm->dev, "Failed to write to tty %s.\n", 971 elm->tty->name); 972 can327_uart_side_failure(elm); 973 974 spin_unlock_bh(&elm->lock); 975 return; 976 } 977 978 elm->txleft -= written; 979 elm->txhead += written; 980 } 981 982 if (!elm->txleft) 983 clear_bit(TTY_DO_WRITE_WAKEUP, &elm->tty->flags); 984 985 spin_unlock_bh(&elm->lock); 986 } 987 988 /* Called by the driver when there's room for more data. */ 989 static void can327_ldisc_tx_wakeup(struct tty_struct *tty) 990 { 991 struct can327 *elm = (struct can327 *)tty->disc_data; 992 993 schedule_work(&elm->tx_work); 994 } 995 996 /* ELM327 can only handle bitrates that are integer divisors of 500 kHz, 997 * or 7/8 of that. Divisors are 1 to 64. 998 * Currently we don't implement support for 7/8 rates. 999 */ 1000 static const u32 can327_bitrate_const[] = { 1001 7812, 7936, 8064, 8196, 8333, 8474, 8620, 8771, 1002 8928, 9090, 9259, 9433, 9615, 9803, 10000, 10204, 1003 10416, 10638, 10869, 11111, 11363, 11627, 11904, 12195, 1004 12500, 12820, 13157, 13513, 13888, 14285, 14705, 15151, 1005 15625, 16129, 16666, 17241, 17857, 18518, 19230, 20000, 1006 20833, 21739, 22727, 23809, 25000, 26315, 27777, 29411, 1007 31250, 33333, 35714, 38461, 41666, 45454, 50000, 55555, 1008 62500, 71428, 83333, 100000, 125000, 166666, 250000, 500000 1009 }; 1010 1011 static int can327_ldisc_open(struct tty_struct *tty) 1012 { 1013 struct net_device *dev; 1014 struct can327 *elm; 1015 int err; 1016 1017 if (!capable(CAP_NET_ADMIN)) 1018 return -EPERM; 1019 1020 if (!tty->ops->write) 1021 return -EOPNOTSUPP; 1022 1023 dev = alloc_candev(sizeof(struct can327), 0); 1024 if (!dev) 1025 return -ENFILE; 1026 elm = netdev_priv(dev); 1027 1028 /* Configure TTY interface */ 1029 tty->receive_room = 65536; /* We don't flow control */ 1030 spin_lock_init(&elm->lock); 1031 INIT_WORK(&elm->tx_work, can327_ldisc_tx_worker); 1032 1033 /* Configure CAN metadata */ 1034 elm->can.bitrate_const = can327_bitrate_const; 1035 elm->can.bitrate_const_cnt = ARRAY_SIZE(can327_bitrate_const); 1036 elm->can.ctrlmode_supported = CAN_CTRLMODE_LISTENONLY; 1037 1038 /* Configure netdev interface */ 1039 elm->dev = dev; 1040 dev->netdev_ops = &can327_netdev_ops; 1041 dev->ethtool_ops = &can327_ethtool_ops; 1042 1043 /* Mark ldisc channel as alive */ 1044 elm->tty = tty; 1045 tty->disc_data = elm; 1046 1047 /* Let 'er rip */ 1048 err = register_candev(elm->dev); 1049 if (err) { 1050 free_candev(elm->dev); 1051 return err; 1052 } 1053 1054 netdev_info(elm->dev, "can327 on %s.\n", tty->name); 1055 1056 return 0; 1057 } 1058 1059 /* Close down a can327 channel. 1060 * This means flushing out any pending queues, and then returning. 1061 * This call is serialized against other ldisc functions: 1062 * Once this is called, no other ldisc function of ours is entered. 1063 * 1064 * We also use this function for a hangup event. 1065 */ 1066 static void can327_ldisc_close(struct tty_struct *tty) 1067 { 1068 struct can327 *elm = (struct can327 *)tty->disc_data; 1069 1070 /* unregister_netdev() calls .ndo_stop() so we don't have to. 1071 * Our .ndo_stop() also flushes the TTY write wakeup handler, 1072 * so we can safely set elm->tty = NULL after this. 1073 */ 1074 unregister_candev(elm->dev); 1075 1076 /* Mark channel as dead */ 1077 spin_lock_bh(&elm->lock); 1078 tty->disc_data = NULL; 1079 elm->tty = NULL; 1080 spin_unlock_bh(&elm->lock); 1081 1082 netdev_info(elm->dev, "can327 off %s.\n", tty->name); 1083 1084 free_candev(elm->dev); 1085 } 1086 1087 static int can327_ldisc_ioctl(struct tty_struct *tty, unsigned int cmd, 1088 unsigned long arg) 1089 { 1090 struct can327 *elm = (struct can327 *)tty->disc_data; 1091 unsigned int tmp; 1092 1093 switch (cmd) { 1094 case SIOCGIFNAME: 1095 tmp = strnlen(elm->dev->name, IFNAMSIZ - 1) + 1; 1096 if (copy_to_user((void __user *)arg, elm->dev->name, tmp)) 1097 return -EFAULT; 1098 return 0; 1099 1100 case SIOCSIFHWADDR: 1101 return -EINVAL; 1102 1103 default: 1104 return tty_mode_ioctl(tty, cmd, arg); 1105 } 1106 } 1107 1108 static struct tty_ldisc_ops can327_ldisc = { 1109 .owner = THIS_MODULE, 1110 .name = KBUILD_MODNAME, 1111 .num = N_CAN327, 1112 .receive_buf = can327_ldisc_rx, 1113 .write_wakeup = can327_ldisc_tx_wakeup, 1114 .open = can327_ldisc_open, 1115 .close = can327_ldisc_close, 1116 .ioctl = can327_ldisc_ioctl, 1117 }; 1118 1119 static int __init can327_init(void) 1120 { 1121 int status; 1122 1123 status = tty_register_ldisc(&can327_ldisc); 1124 if (status) 1125 pr_err("Can't register line discipline\n"); 1126 1127 return status; 1128 } 1129 1130 static void __exit can327_exit(void) 1131 { 1132 /* This will only be called when all channels have been closed by 1133 * userspace - tty_ldisc.c takes care of the module's refcount. 1134 */ 1135 tty_unregister_ldisc(&can327_ldisc); 1136 } 1137 1138 module_init(can327_init); 1139 module_exit(can327_exit); 1140 1141 MODULE_ALIAS_LDISC(N_CAN327); 1142 MODULE_DESCRIPTION("ELM327 based CAN interface"); 1143 MODULE_LICENSE("GPL"); 1144 MODULE_AUTHOR("Max Staudt <max@enpas.org>"); 1145