module/elmcan.c

   1 /*
   2  * elmcan.c - ELM327 based CAN interface driver
   3  *            (tty line discipline)
   4  *
   5  * This file is derived from linux/drivers/net/can/slcan.c
   6  *
   7  * elmcan.c Author : Max Staudt <elmcan@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  * SPDX-License-Identifier: GPL-2.0
  13  *
  14  */
  15
  16 #define pr_fmt(fmt) "[elmcan] " fmt
  17
  18
  19 #include <linux/init.h>
  20 #include <linux/module.h>
  21 #include <linux/moduleparam.h>
  22
  23 #include <linux/bitops.h>
  24 #include <linux/errno.h>
  25 #include <linux/if_ether.h>
  26 #include <linux/kernel.h>
  27 #include <linux/list.h>
  28 #include <linux/netdevice.h>
  29 #include <linux/skbuff.h>
  30 #include <linux/spinlock.h>
  31 #include <linux/string.h>
  32 #include <linux/tty.h>
  33 #include <linux/workqueue.h>
  34
  35 #include <linux/can.h>
  36 #include <linux/can/dev.h>
  37 #include <linux/can/error.h>
  38 #include <linux/can/led.h>
  39
  40
  41 MODULE_ALIAS_LDISC(N_ELMCAN);
  42 MODULE_DESCRIPTION("ELM327 based CAN interface");
  43 MODULE_LICENSE("GPL");
  44 MODULE_AUTHOR("Max Staudt <max-linux@enpas.org>");
  45
  46 /* Line discipline ID number */
  47 #ifndef N_ELMCAN
  48 #define N_ELMCAN 26
  49 #endif
  50
  51 #define ELM327_CAN_CONFIG_SEND_SFF           0x8000
  52 #define ELM327_CAN_CONFIG_VARIABLE_DLC       0x4000
  53 #define ELM327_CAN_CONFIG_RECV_BOTH_SFF_EFF  0x2000
  54 #define ELM327_CAN_CONFIG_BAUDRATE_MULT_8_7  0x1000
  55
  56 #define ELM327_MAGIC_CHAR 'y'
  57 #define ELM327_MAGIC_STRING "y"
  58
  59
  60 /* Bits in elm->cmds_todo */
  61 enum ELM_TODO {
  62         ELM_TODO_CAN_DATA = 0,
  63         ELM_TODO_CANID_11BIT,
  64         ELM_TODO_CANID_29BIT_LOW,
  65         ELM_TODO_CANID_29BIT_HIGH,
  66         ELM_TODO_CAN_CONFIG,
  67         ELM_TODO_RESPONSES,
  68         ELM_TODO_SILENT_MONITOR,
  69         ELM_TODO_INIT
  70 };
  71
  72
  73 struct elmcan {
  74         /* This must be the first member when using alloc_candev() */
  75         struct can_priv can;
  76
  77         /* TTY and netdev devices that we're bridging */
  78         struct tty_struct       *tty;
  79         struct net_device       *dev;
  80
  81         int                     magic;
  82
  83         /* Per-channel lock */
  84         spinlock_t              lock;
  85
  86         /* TTY TX helpers */
  87         struct work_struct      tx_work;        /* Flushes TTY TX buffer   */
  88         unsigned char           txbuf[32];
  89         unsigned char           *txhead;        /* Pointer to next TX byte */
  90         int                     txleft;         /* Bytes left to TX */
  91
  92         /* TTY RX helpers */
  93         unsigned char rxbuf[256];
  94         int rxfill;
  95
  96         /* State machine */
  97         enum {
  98                 ELM_NOTINIT = 0,
  99                 ELM_GETMAGICCHAR,
 100                 ELM_GETPROMPT,
 101                 ELM_RECEIVING,
 102         } state;
 103
 104         int drop_next_line;
 105
 106         /* The CAN frame and config the ELM327 is sending/using,
 107          * or will send/use after finishing all cmds_todo */
 108         struct can_frame can_frame;
 109         unsigned short can_config;
 110         unsigned long can_bitrate;
 111         unsigned char can_bitrate_divisor;
 112         int silent_monitoring;
 113
 114         /* Things we have yet to send */
 115         char **next_init_cmd;
 116         unsigned long cmds_todo;
 117 };
 118
 119
 120 static DEFINE_SPINLOCK(elmcan_open_lock);
 121
 122
 123
 124
 125  /************************************************************************
 126   *                     ELM327: Transmission                             *
 127   ************************************************************************/
 128
 129 static void elm327_send(struct elmcan *elm, const void *buf, size_t len)
 130 {
 131         int actual;
 132
 133         memcpy(elm->txbuf, buf, len);
 134
 135         /* Order of next two lines is *very* important.
 136          * When we are sending a little amount of data,
 137          * the transfer may be completed inside the ops->write()
 138          * routine, because it's running with interrupts enabled.
 139          * In this case we *never* got WRITE_WAKEUP event,
 140          * if we did not request it before write operation.
 141          *       14 Oct 1994  Dmitry Gorodchanin.
 142          */
 143         set_bit(TTY_DO_WRITE_WAKEUP, &elm->tty->flags);
 144         actual = elm->tty->ops->write(elm->tty, elm->txbuf, len);
 145         elm->txleft = len - actual;
 146         elm->txhead = elm->txbuf + actual;
 147 }
 148
 149
 150 static void elm327_kick_into_cmd_mode(struct elmcan *elm)
 151 {
 152         if (elm->state != ELM_GETMAGICCHAR && elm->state != ELM_GETPROMPT) {
 153                 elm327_send(elm, ELM327_MAGIC_STRING, 1);
 154
 155                 elm->state = ELM_GETMAGICCHAR;
 156                 elm->rxfill = 0;
 157         }
 158 }
 159
 160
 161 static void elm327_send_frame(struct elmcan *elm, struct can_frame *frame)
 162 {
 163         if (elm->can_frame.can_id != frame->can_id) {
 164                 /* Set the new CAN ID for transmission. */
 165                 if ((frame->can_id & CAN_EFF_FLAG) ^ (elm->can_frame.can_id & CAN_EFF_FLAG)) {
 166                         elm->can_config = (frame->can_id & CAN_EFF_FLAG ? 0 : ELM327_CAN_CONFIG_SEND_SFF)
 167                                         | ELM327_CAN_CONFIG_VARIABLE_DLC
 168                                         | ELM327_CAN_CONFIG_RECV_BOTH_SFF_EFF
 169                                         | elm->can_bitrate_divisor;
 170
 171                         set_bit(ELM_TODO_CAN_CONFIG, &elm->cmds_todo);
 172                 }
 173
 174                 if (frame->can_id & CAN_EFF_FLAG) {
 175                         clear_bit(ELM_TODO_CANID_11BIT, &elm->cmds_todo);
 176                         set_bit(ELM_TODO_CANID_29BIT_LOW, &elm->cmds_todo);
 177                         set_bit(ELM_TODO_CANID_29BIT_HIGH, &elm->cmds_todo);
 178                 } else {
 179                         set_bit(ELM_TODO_CANID_11BIT, &elm->cmds_todo);
 180                         clear_bit(ELM_TODO_CANID_29BIT_LOW, &elm->cmds_todo);
 181                         clear_bit(ELM_TODO_CANID_29BIT_HIGH, &elm->cmds_todo);
 182                 }
 183         }
 184
 185         elm->can_frame = *frame;
 186         set_bit(ELM_TODO_CAN_DATA, &elm->cmds_todo);
 187
 188         elm327_kick_into_cmd_mode(elm);
 189 }
 190
 191
 192
 193  /************************************************************************
 194   *                     ELM327: Initialization sequence                  *
 195   ************************************************************************/
 196
 197 static char *elm327_init_script[] = {
 198         "AT WS\r",        /* v1.0: Warm Start */
 199         "AT PP FF OFF\r", /* v1.0: All Programmable Parameters Off */
 200         "AT M0\r",        /* v1.0: Memory Off */
 201         "AT AL\r",        /* v1.0: Allow Long messages */
 202         "AT BI\r",        /* v1.0: Bypass Initialization */
 203         "AT CAF0\r",      /* v1.0: CAN Auto Formatting Off */
 204         "AT CFC0\r",      /* v1.0: CAN Flow Control Off */
 205         "AT CF 000\r",    /* v1.0: Reset CAN ID Filter */
 206         "AT CM 000\r",    /* v1.0: Reset CAN ID Mask */
 207         "AT E1\r",        /* v1.0: Echo On */
 208         "AT H1\r",        /* v1.0: Headers On */
 209         "AT L0\r",        /* v1.0: Linefeeds Off */
 210         "AT SH 7DF\r",    /* v1.0: Set CAN sending ID to 0x7df */
 211         "AT ST FF\r",     /* v1.0: Set maximum Timeout for response after TX */
 212         "AT AT0\r",       /* v1.2: Adaptive Timing Off */
 213         "AT D1\r",        /* v1.3: Print DLC On */
 214         "AT S1\r",        /* v1.3: Spaces On */
 215         "AT TP B\r",      /* v1.0: Try Protocol B */
 216         NULL
 217 };
 218
 219
 220 static void elm327_init(struct elmcan *elm)
 221 {
 222         elm->state = ELM_NOTINIT;
 223         elm->can_frame.can_id = 0x7df;
 224         elm->rxfill = 0;
 225         elm->drop_next_line = 0;
 226
 227         /* We can only set the bitrate as a fraction of 500000.
 228          * The bit timing constants in elmcan_bittiming_const will
 229          * limit the user to the right values.
 230          */
 231         elm->can_bitrate_divisor = 500000 / elm->can.bittiming.bitrate;
 232         elm->can_config = ELM327_CAN_CONFIG_SEND_SFF
 233                         | ELM327_CAN_CONFIG_VARIABLE_DLC
 234                         | ELM327_CAN_CONFIG_RECV_BOTH_SFF_EFF
 235                         | elm->can_bitrate_divisor;
 236
 237         /* Configure ELM327 and then start monitoring */
 238         elm->next_init_cmd = &elm327_init_script[0];
 239         set_bit(ELM_TODO_INIT, &elm->cmds_todo);
 240         set_bit(ELM_TODO_SILENT_MONITOR, &elm->cmds_todo);
 241         set_bit(ELM_TODO_RESPONSES, &elm->cmds_todo);
 242         set_bit(ELM_TODO_CAN_CONFIG, &elm->cmds_todo);
 243
 244         elm327_kick_into_cmd_mode(elm);
 245 }
 246
 247
 248
 249  /************************************************************************
 250   *                     ELM327: Reception -> netdev glue                 *
 251   ************************************************************************/
 252
 253 static void elm327_feed_frame_to_netdev(struct elmcan *elm, const struct can_frame *frame)
 254 {
 255         struct can_frame *cf;
 256         struct sk_buff *skb;
 257
 258         if (!netif_running(elm->dev)) {
 259                 return;
 260         }
 261
 262         skb = alloc_can_skb(elm->dev, &cf);
 263
 264         if (!skb)
 265                 return;
 266
 267         memcpy(cf, frame, sizeof(struct can_frame));
 268
 269         elm->dev->stats.rx_packets++;
 270         elm->dev->stats.rx_bytes += frame->can_dlc;
 271         netif_rx_ni(skb);
 272
 273         can_led_event(elm->dev, CAN_LED_EVENT_RX);
 274 }
 275
 276
 277
 278  /************************************************************************
 279   *                     ELM327: Panic handler                            *
 280   ************************************************************************/
 281
 282 static inline void elm327_panic(struct elmcan *elm)
 283 {
 284         struct can_frame frame = {0};
 285
 286         frame.can_id = CAN_ERR_FLAG | CAN_ERR_RESTARTED;
 287         frame.can_dlc = CAN_ERR_DLC;
 288         elm327_feed_frame_to_netdev(elm, &frame);
 289
 290         pr_err("ELM327 misbehaved. Re-initializing.\n");
 291
 292         elm->can.can_stats.restarts++;
 293         elm327_init(elm);
 294 }
 295
 296
 297
 298  /************************************************************************
 299   *                     ELM327: Reception parser                         *
 300   ************************************************************************/
 301
 302 static void elm327_parse_error(struct elmcan *elm, int len)
 303 {
 304         struct can_frame frame = {0};
 305
 306         frame.can_id = CAN_ERR_FLAG;
 307         frame.can_dlc = CAN_ERR_DLC;
 308
 309         switch(len) {
 310                 case 17:
 311                         if (!memcmp(elm->rxbuf, "UNABLE TO CONNECT", 17)) {
 312                                 pr_err("The ELM327 reported UNABLE TO CONNECT. Please check your setup.\n");
 313                         }
 314                         break;
 315                 case 11:
 316                         if (!memcmp(elm->rxbuf, "BUFFER FULL", 11)) {
 317                                 /* This case will only happen if the last data
 318                                  * line was complete.
 319                                  * Otherwise, elm327_parse_frame() will emit the
 320                                  * error frame instead.
 321                                  */
 322                                 frame.can_id |= CAN_ERR_CRTL;
 323                                 frame.data[1] = CAN_ERR_CRTL_RX_OVERFLOW;
 324                         }
 325                         break;
 326                 case 9:
 327                         if (!memcmp(elm->rxbuf, "BUS ERROR", 9)) {
 328                                 frame.can_id |= CAN_ERR_BUSERROR;
 329                         }
 330                         if (!memcmp(elm->rxbuf, "CAN ERROR", 9)
 331                                 || !memcmp(elm->rxbuf, "<RX ERROR", 9)) {
 332                                 frame.can_id |= CAN_ERR_PROT;
 333                         }
 334                         break;
 335                 case 8:
 336                         if (!memcmp(elm->rxbuf, "BUS BUSY", 8)) {
 337                                 frame.can_id |= CAN_ERR_PROT;
 338                                 frame.data[2] = CAN_ERR_PROT_OVERLOAD;
 339                         }
 340                         if (!memcmp(elm->rxbuf, "FB ERROR", 8)) {
 341                                 frame.can_id |= CAN_ERR_PROT;
 342                                 frame.data[2] = CAN_ERR_PROT_TX;
 343                         }
 344                         break;
 345                 case 5:
 346                         if (!memcmp(elm->rxbuf, "ERR", 3)) {
 347                                 pr_err("The ELM327 reported an ERR%c%c. Please power it off and on again.\n",
 348                                         elm->rxbuf[3], elm->rxbuf[4]);
 349                                 frame.can_id |= CAN_ERR_CRTL;
 350                         }
 351                         break;
 352                 default:
 353                         /* Don't emit an error frame if we're unsure */
 354                         return;
 355         }
 356
 357         elm327_feed_frame_to_netdev(elm, &frame);
 358 }
 359
 360
 361 static int elm327_parse_frame(struct elmcan *elm, int len)
 362 {
 363         struct can_frame frame = {0};
 364         int hexlen;
 365         int datastart;
 366         int i;
 367
 368         /* Find first non-hex and non-space character:
 369          *  - In the simplest case, there is none.
 370          *  - For RTR frames, 'R' is the first non-hex character.
 371          *  - An error message may replace the end of the data line.
 372          */
 373         for (hexlen = 0; hexlen <= len; hexlen++) {
 374                 if (hex_to_bin(elm->rxbuf[hexlen]) < 0
 375                     && elm->rxbuf[hexlen] != ' ') {
 376                         break;
 377                 }
 378         }
 379
 380         /* Use spaces in CAN ID to distinguish 29 or 11 bit address length.
 381          * No out-of-bounds access:
 382          * We use the fact that we can always read from elm->rxbuf. */
 383         if (elm->rxbuf[2] == ' ' && elm->rxbuf[5] == ' '
 384                 && elm->rxbuf[8] == ' ' && elm->rxbuf[11] == ' '
 385                 && elm->rxbuf[13] == ' ') {
 386                 frame.can_id = CAN_EFF_FLAG;
 387                 datastart = 14;
 388         } else if (elm->rxbuf[3] == ' ' && elm->rxbuf[5] == ' ') {
 389                 frame.can_id = 0;
 390                 datastart = 6;
 391         } else {
 392                 /* This is not a well-formatted data line.
 393                  * Assume it's an error message. */
 394                 return 1;
 395         }
 396
 397         if (hexlen < datastart) {
 398                 /* The line is too short to be a valid frame hex dump.
 399                  * Something interrupted the hex dump or it is invalid. */
 400                 return 1;
 401         }
 402
 403         /* From here on all chars up to buf[hexlen] are hex or spaces,
 404          * at well-defined offsets. */
 405
 406         /* Read CAN data length */
 407         frame.can_dlc = (hex_to_bin(elm->rxbuf[datastart - 2]) << 0);
 408
 409         /* Read CAN ID */
 410         if (frame.can_id & CAN_EFF_FLAG) {
 411                 frame.can_id |= (hex_to_bin(elm->rxbuf[0]) << 28)
 412                               | (hex_to_bin(elm->rxbuf[1]) << 24)
 413                               | (hex_to_bin(elm->rxbuf[3]) << 20)
 414                               | (hex_to_bin(elm->rxbuf[4]) << 16)
 415                               | (hex_to_bin(elm->rxbuf[6]) << 12)
 416                               | (hex_to_bin(elm->rxbuf[7]) << 8)
 417                               | (hex_to_bin(elm->rxbuf[9]) << 4)
 418                               | (hex_to_bin(elm->rxbuf[10]) << 0);
 419         } else {
 420                 frame.can_id |= (hex_to_bin(elm->rxbuf[0]) << 8)
 421                               | (hex_to_bin(elm->rxbuf[1]) << 4)
 422                               | (hex_to_bin(elm->rxbuf[2]) << 0);
 423         }
 424
 425         /* Check for RTR frame */
 426         if (elm->rxfill >= hexlen + 3
 427             && elm->rxbuf[hexlen + 0] == 'R'
 428             && elm->rxbuf[hexlen + 1] == 'T'
 429             && elm->rxbuf[hexlen + 2] == 'R') {
 430                 frame.can_id |= CAN_RTR_FLAG;
 431         }
 432
 433         /* Is the line long enough to hold the advertised payload? */
 434         if (!(frame.can_id & CAN_RTR_FLAG) && (hexlen < frame.can_dlc * 3 + datastart)) {
 435                 /* Incomplete frame. */
 436
 437                 /* Probably the ELM327's RS232 TX buffer was full.
 438                  * Emit an error frame and exit. */
 439                 frame.can_id = CAN_ERR_FLAG | CAN_ERR_CRTL;
 440                 frame.can_dlc = CAN_ERR_DLC;
 441                 frame.data[1] = CAN_ERR_CRTL_RX_OVERFLOW;
 442                 elm327_feed_frame_to_netdev(elm, &frame);
 443
 444                 /* Signal failure to parse.
 445                  * The line will be re-parsed as an error line, which will fail.
 446                  * However, this will correctly drop the state machine back into
 447                  * command mode.
 448                  */
 449                 return 2;
 450         }
 451
 452         /* Parse the data nibbles. */
 453         for (i = 0; i < frame.can_dlc; i++) {
 454                 frame.data[i] = (hex_to_bin(elm->rxbuf[datastart+3*i]) << 4)
 455                                 | (hex_to_bin(elm->rxbuf[datastart+3*i+1]) << 0);
 456         }
 457
 458         /* Feed the frame to the network layer. */
 459         elm327_feed_frame_to_netdev(elm, &frame);
 460
 461         return 0;
 462 }
 463
 464
 465 static void elm327_parse_line(struct elmcan *elm, int len)
 466 {
 467         /* Skip empty lines */
 468         if (!len) {
 469                 return;
 470         }
 471
 472         /* Skip echo lines */
 473         if (elm->drop_next_line) {
 474                 elm->drop_next_line = 0;
 475                 return;
 476         } else if (elm->rxbuf[0] == 'A' && elm->rxbuf[1] == 'T') {
 477                 return;
 478         }
 479
 480         /* Regular parsing */
 481         switch(elm->state) {
 482                 case ELM_RECEIVING:
 483                         if (elm327_parse_frame(elm, len)) {
 484                                 /* Parse an error line. */
 485                                 elm327_parse_error(elm, len);
 486
 487                                 /* After the error line, we expect a prompt. */
 488                                 elm->state = ELM_GETPROMPT;
 489                         }
 490                         break;
 491                 default:
 492                         break;
 493         }
 494 }
 495
 496
 497 static void elm327_handle_prompt(struct elmcan *elm)
 498 {
 499         if (elm->cmds_todo) {
 500                 struct can_frame *frame = &elm->can_frame;
 501                 char txbuf[20];
 502
 503                 if (test_bit(ELM_TODO_INIT, &elm->cmds_todo)) {
 504                         elm327_send(elm, *elm->next_init_cmd, strlen(*elm->next_init_cmd));
 505                         elm->next_init_cmd++;
 506                         if (!(*elm->next_init_cmd)) {
 507                                 clear_bit(ELM_TODO_INIT, &elm->cmds_todo);
 508                                 pr_info("%s: Initialization finished.\n", elm->dev->name);
 509                         }
 510
 511                         /* Some chips are unreliable and need extra time after
 512                          * init commands, as seen with a clone.
 513                          * So let's do a dummy get-cmd-prompt dance. */
 514                         elm->state = ELM_NOTINIT;
 515                         elm327_kick_into_cmd_mode(elm);
 516                 } else if (test_and_clear_bit(ELM_TODO_SILENT_MONITOR, &elm->cmds_todo)) {
 517                         snprintf(txbuf, sizeof(txbuf), "ATCSM%i\r", !(!(elm->can.ctrlmode & CAN_CTRLMODE_LISTENONLY)));
 518                 } else if (test_and_clear_bit(ELM_TODO_RESPONSES, &elm->cmds_todo)) {
 519                         snprintf(txbuf, sizeof(txbuf), "ATR%i\r", !(elm->can.ctrlmode & CAN_CTRLMODE_LISTENONLY));
 520                 } else if (test_and_clear_bit(ELM_TODO_CAN_CONFIG, &elm->cmds_todo)) {
 521                         snprintf(txbuf, sizeof(txbuf), "ATPB%04X\r", elm->can_config);
 522                 } else if (test_and_clear_bit(ELM_TODO_CANID_29BIT_HIGH, &elm->cmds_todo)) {
 523                         snprintf(txbuf, sizeof(txbuf), "ATCP%02X\r", (frame->can_id & CAN_EFF_MASK) >> 24);
 524                 } else if (test_and_clear_bit(ELM_TODO_CANID_29BIT_LOW, &elm->cmds_todo)) {
 525                         snprintf(txbuf, sizeof(txbuf), "ATSH%06X\r", frame->can_id & CAN_EFF_MASK & ((1 << 24) - 1));
 526                 } else if (test_and_clear_bit(ELM_TODO_CANID_11BIT, &elm->cmds_todo)) {
 527                         snprintf(txbuf, sizeof(txbuf), "ATSH%03X\r", frame->can_id & CAN_SFF_MASK);
 528                 } else if (test_and_clear_bit(ELM_TODO_CAN_DATA, &elm->cmds_todo)) {
 529                         if (frame->can_id & CAN_RTR_FLAG) {
 530                                 snprintf(txbuf, sizeof(txbuf), "ATRTR\r");
 531                         } else {
 532                                 int i;
 533
 534                                 for (i = 0; i < frame->can_dlc; i++) {
 535                                         sprintf(&txbuf[2*i], "%02X", frame->data[i]);
 536                                 }
 537
 538                                 sprintf(&txbuf[2*i], "\r");
 539                         }
 540
 541                         elm->drop_next_line = 1;
 542                         elm->state = ELM_RECEIVING;
 543                 }
 544
 545                 elm327_send(elm, txbuf, strlen(txbuf));
 546         } else {
 547                 /* Enter CAN monitor mode */
 548                 elm327_send(elm, "ATMA\r", 5);
 549                 elm->state = ELM_RECEIVING;
 550         }
 551 }
 552
 553
 554 static void elm327_drop_bytes(struct elmcan *elm, int i)
 555 {
 556         memmove(&elm->rxbuf[0], &elm->rxbuf[i], sizeof(elm->rxbuf) - i);
 557         elm->rxfill -= i;
 558 }
 559
 560
 561 static void elm327_parse_rxbuf(struct elmcan *elm)
 562 {
 563         int len;
 564
 565         switch (elm->state) {
 566         case ELM_NOTINIT:
 567                 elm->rxfill = 0;
 568                 return;
 569
 570         case ELM_GETMAGICCHAR:
 571         {
 572                 /* Wait for 'y' or '>' */
 573                 int i;
 574
 575                 for (i = 0; i < elm->rxfill; i++) {
 576                         if (elm->rxbuf[i] == ELM327_MAGIC_CHAR) {
 577                                 elm327_send(elm, "\r", 1);
 578                                 elm->state = ELM_GETPROMPT;
 579                                 i++;
 580                                 break;
 581                         } else if (elm->rxbuf[i] == '>') {
 582                                 elm327_send(elm, ELM327_MAGIC_STRING, 1);
 583                                 i++;
 584                                 break;
 585                         }
 586                 }
 587
 588                 elm327_drop_bytes(elm, i);
 589
 590                 return;
 591         }
 592
 593         case ELM_GETPROMPT:
 594                 /* Wait for '>' */
 595                 if (elm->rxbuf[elm->rxfill - 1] == '>') {
 596                         elm327_handle_prompt(elm);
 597                 }
 598
 599                 elm->rxfill = 0;
 600                 return;
 601
 602         case ELM_RECEIVING:
 603                 /* Find <CR> delimiting feedback lines. */
 604                 for (len = 0;
 605                      (len < elm->rxfill) && (elm->rxbuf[len] != '\r');
 606                      len++) {
 607                         /* empty loop */
 608                 }
 609
 610                 if (len == sizeof(elm->rxbuf)) {
 611                         /* Line exceeds buffer. It's probably all garbage.
 612                          * Did we even connect at the right baud rate? */
 613                         pr_err("RX buffer overflow. Faulty ELM327 connected?\n");
 614                         elm327_panic(elm);
 615                 } else if (len == elm->rxfill) {
 616                         if (elm->state == ELM_RECEIVING
 617                                 && elm->rxbuf[elm->rxfill - 1] == '>') {
 618                                 /* The ELM327's AT ST response timeout ran out,
 619                                  * so we got a prompt.
 620                                  * Clear RX buffer and restart listening. */
 621                                 elm->rxfill = 0;
 622
 623                                 elm327_handle_prompt(elm);
 624                                 return;
 625                         } else {
 626                                 /* We haven't received a full line yet. Wait for more data. */
 627                                 return;
 628                         }
 629                 }
 630
 631                 /* We have a full line to parse. */
 632                 elm327_parse_line(elm, len);
 633
 634                 /* Remove parsed data from RX buffer. */
 635                 elm327_drop_bytes(elm, len+1);
 636
 637                 /* More data to parse? */
 638                 if (elm->rxfill) {
 639                         elm327_parse_rxbuf(elm);
 640                 }
 641         }
 642 }
 643
 644
 645
 646
 647
 648  /************************************************************************
 649   *                             netdev                                   *
 650   ************************************************************************/
 651
 652 /* Netdevice DOWN -> UP routine */
 653 static int elmcan_netdev_open(struct net_device *dev)
 654 {
 655         struct elmcan *elm = netdev_priv(dev);
 656         int err;
 657
 658         spin_lock_bh(&elm->lock);
 659         if (elm->tty == NULL) {
 660                 spin_unlock_bh(&elm->lock);
 661                 return -ENODEV;
 662         }
 663
 664         /* open_candev() checks for elm->can.bittiming.bitrate != 0 */
 665         err = open_candev(dev);
 666         if (err) {
 667                 spin_unlock_bh(&elm->lock);
 668                 return err;
 669         }
 670
 671         /* Initialize the ELM327 */
 672         elm327_init(elm);
 673         spin_unlock_bh(&elm->lock);
 674
 675         can_led_event(dev, CAN_LED_EVENT_OPEN);
 676         elm->can.state = CAN_STATE_ERROR_ACTIVE;
 677         netif_start_queue(dev);
 678
 679         return 0;
 680 }
 681
 682 /* Netdevice UP -> DOWN routine */
 683 static int elmcan_netdev_close(struct net_device *dev)
 684 {
 685         struct elmcan *elm = netdev_priv(dev);
 686
 687         spin_lock_bh(&elm->lock);
 688         if (elm->tty) {
 689                 /* TTY discipline is running. */
 690
 691                 /* Interrupt whatever we're doing right now */
 692                 elm327_send(elm, ELM327_MAGIC_STRING, 1);
 693
 694                 /* Clear the wakeup bit, as the netdev will be down and thus
 695                  * the wakeup handler won't clear it
 696                  */
 697                 clear_bit(TTY_DO_WRITE_WAKEUP, &elm->tty->flags);
 698
 699                 spin_unlock_bh(&elm->lock);
 700
 701                 flush_work(&elm->tx_work);
 702         } else {
 703                 spin_unlock_bh(&elm->lock);
 704         }
 705
 706         elm->can.state = CAN_STATE_STOPPED;
 707         netif_stop_queue(dev);
 708         close_candev(dev);
 709         can_led_event(dev, CAN_LED_EVENT_STOP);
 710
 711         return 0;
 712 }
 713
 714 /* Send a can_frame to a TTY queue. */
 715 static netdev_tx_t elmcan_netdev_start_xmit(struct sk_buff *skb, struct net_device *dev)
 716 {
 717         struct elmcan *elm = netdev_priv(dev);
 718         struct can_frame *frame = (struct can_frame *) skb->data;
 719
 720         if (skb->len != sizeof(struct can_frame))
 721                 goto out;
 722
 723         if (!netif_running(dev))  {
 724                 pr_warn("%s: xmit: iface is down\n", dev->name);
 725                 goto out;
 726         }
 727
 728         /* BHs are already disabled, so no spin_lock_bh().
 729          * See Documentation/networking/netdevices.txt
 730          */
 731         spin_lock(&elm->lock);
 732         if (elm->tty == NULL
 733                 || elm->can.ctrlmode & CAN_CTRLMODE_LISTENONLY) {
 734                 spin_unlock(&elm->lock);
 735                 goto out;
 736         }
 737
 738         netif_stop_queue(dev);
 739
 740         elm327_send_frame(elm, frame);
 741         spin_unlock(&elm->lock);
 742
 743         dev->stats.tx_packets++;
 744         dev->stats.tx_bytes += frame->can_dlc;
 745
 746         can_led_event(dev, CAN_LED_EVENT_TX);
 747
 748 out:
 749         kfree_skb(skb);
 750         return NETDEV_TX_OK;
 751 }
 752
 753 static int elmcan_netdev_change_mtu(struct net_device *dev, int new_mtu)
 754 {
 755         return -EINVAL;
 756 }
 757
 758 static const struct net_device_ops elmcan_netdev_ops = {
 759         .ndo_open       = elmcan_netdev_open,
 760         .ndo_stop       = elmcan_netdev_close,
 761         .ndo_start_xmit = elmcan_netdev_start_xmit,
 762         .ndo_change_mtu = elmcan_netdev_change_mtu,
 763 };
 764
 765
 766
 767
 768
 769  /************************************************************************
 770   *                     Line discipline                                  *
 771   ************************************************************************/
 772
 773 /*
 774  * Handle the 'receiver data ready' interrupt.
 775  * This function is called by the 'tty_io' module in the kernel when
 776  * a block of ELM327 CAN data has been received, which can now be parsed
 777  * and sent on to some IP layer for further processing. This will not
 778  * be re-entered while running but other ldisc functions may be called
 779  * in parallel
 780  */
 781 static void elmcan_ldisc_rx(struct tty_struct *tty,
 782                         const unsigned char *cp, char *fp, int count)
 783 {
 784         struct elmcan *elm = (struct elmcan *) tty->disc_data;
 785
 786         if (!elm)
 787                 return;
 788
 789         /* Read the characters out of the buffer */
 790         while (count-- && elm->rxfill < sizeof(elm->rxbuf)) {
 791                 if (fp && *fp++) {
 792                         pr_err("Error in received character stream. Check your wiring.");
 793
 794                         spin_lock_bh(&elm->lock);
 795                         elm327_panic(elm);
 796                         spin_unlock_bh(&elm->lock);
 797                         return;
 798                 }
 799                 if (*cp != 0) {
 800                         elm->rxbuf[elm->rxfill++] = *cp;
 801                 }
 802                 cp++;
 803         }
 804
 805         if (count >= 0) {
 806                 pr_err("Receive buffer overflowed. Bad chip or wiring?");
 807
 808                 spin_lock_bh(&elm->lock);
 809                 elm327_panic(elm);
 810                 spin_unlock_bh(&elm->lock);
 811                 return;
 812         }
 813
 814         spin_lock_bh(&elm->lock);
 815         elm327_parse_rxbuf(elm);
 816         spin_unlock_bh(&elm->lock);
 817 }
 818
 819 /* Write out remaining transmit buffer.
 820  * Scheduled when TTY is writable.
 821  */
 822 static void elmcan_ldisc_tx_worker(struct work_struct *work)
 823 {
 824         struct elmcan *elm = container_of(work, struct elmcan, tx_work);
 825         ssize_t actual;
 826
 827         spin_lock_bh(&elm->lock);
 828         /* First make sure we're connected. */
 829         if (!elm->tty || !netif_running(elm->dev)) {
 830                 spin_unlock_bh(&elm->lock);
 831                 return;
 832         }
 833
 834         if (elm->txleft <= 0)  {
 835                 /* Our TTY write buffer is empty:
 836                  * We can start transmission of another packet
 837                  */
 838                 clear_bit(TTY_DO_WRITE_WAKEUP, &elm->tty->flags);
 839                 spin_unlock_bh(&elm->lock);
 840                 netif_wake_queue(elm->dev);
 841                 return;
 842         }
 843
 844         actual = elm->tty->ops->write(elm->tty, elm->txhead, elm->txleft);
 845         if (actual < 0) {
 846                 pr_err("Failed to write to tty for %s.\n", elm->dev->name);
 847                 elm327_panic(elm);
 848         }
 849
 850         elm->txleft -= actual;
 851         elm->txhead += actual;
 852         spin_unlock_bh(&elm->lock);
 853 }
 854
 855
 856 /*
 857  * Called by the driver when there's room for more data.
 858  * Schedule the transmit.
 859  */
 860 static void elmcan_ldisc_tx_wakeup(struct tty_struct *tty)
 861 {
 862         struct elmcan *elm = tty->disc_data;
 863
 864         schedule_work(&elm->tx_work);
 865 }
 866
 867
 868
 869 /* Some fake bit timings to allow bitrate setting */
 870 static const struct can_bittiming_const elmcan_bittiming_const = {
 871         .name = "elmcan",
 872         .tseg1_min = 1,
 873         .tseg1_max = 1,
 874         .tseg2_min = 0,
 875         .tseg2_max = 0,
 876         .sjw_max = 1,
 877         .brp_min = 1,
 878         .brp_max = 500,
 879         .brp_inc = 1,
 880 };
 881
 882 /*
 883  * Open the high-level part of the elmcan channel.
 884  * This function is called by the TTY module when the
 885  * elmcan line discipline is called for.
 886  *
 887  * Called in process context serialized from other ldisc calls.
 888  */
 889 static int elmcan_ldisc_open(struct tty_struct *tty)
 890 {
 891         struct net_device *dev;
 892         struct elmcan *elm;
 893         int err;
 894
 895         if (!capable(CAP_NET_ADMIN))
 896                 return -EPERM;
 897
 898         if (!tty->ops->write)
 899                 return -EOPNOTSUPP;
 900
 901         elm = tty->disc_data;
 902
 903         /* First make sure we're not already connected.
 904          * Also, protect against simlutaneous open calls. */
 905         spin_lock_bh(&elmcan_open_lock);
 906         if (elm) {
 907                 spin_unlock_bh(&elmcan_open_lock);
 908                 return -EEXIST;
 909         }
 910         spin_unlock_bh(&elmcan_open_lock);
 911
 912         /* OK.  Find a free elmcan channel to use. */
 913         dev = alloc_candev(sizeof(struct elmcan), 0);
 914         if (!dev)
 915                 return -ENFILE;
 916         elm = netdev_priv(dev);
 917
 918         /* Configure TTY interface */
 919         tty->receive_room = 65536; /* We don't flow control */
 920         elm->txleft = 0; /* Clear TTY TX buffer */
 921         spin_lock_init(&elm->lock);
 922         INIT_WORK(&elm->tx_work, elmcan_ldisc_tx_worker);
 923
 924         /* Configure CAN metadata */
 925         elm->can.state = CAN_STATE_STOPPED;
 926         elm->can.clock.freq = 1000000;
 927         elm->can.bittiming_const = &elmcan_bittiming_const;
 928         elm->can.ctrlmode_supported = CAN_CTRLMODE_LISTENONLY;
 929
 930         /* Configure netlink interface */
 931         elm->dev = dev;
 932         dev->netdev_ops = &elmcan_netdev_ops;
 933
 934         /* Mark ldisc channel as alive */
 935         elm->tty = tty;
 936         tty->disc_data = elm;
 937
 938         devm_can_led_init(elm->dev);
 939
 940         /* Let 'er rip */
 941         err = register_candev(elm->dev);
 942         if (err) {
 943                 free_candev(elm->dev);
 944                 return err;
 945         }
 946
 947         return 0;
 948 }
 949
 950 /*
 951  * Close down an elmcan channel.
 952  * This means flushing out any pending queues, and then returning. This
 953  * call is serialized against other ldisc functions.
 954  *
 955  * We also use this method for a hangup event.
 956  */
 957 static void elmcan_ldisc_close(struct tty_struct *tty)
 958 {
 959         struct elmcan *elm = (struct elmcan *) tty->disc_data;
 960
 961         /* First make sure we're connected. */
 962         if (!elm)
 963                 return;
 964
 965         /* Flush network side */
 966         unregister_candev(elm->dev);
 967
 968         /* Mark channel as dead */
 969         spin_lock_bh(&elm->lock);
 970         tty->disc_data = NULL;
 971         elm->tty = NULL;
 972         spin_unlock_bh(&elm->lock);
 973
 974         /* Flush TTY side */
 975         flush_work(&elm->tx_work);
 976
 977         /* Free our memory */
 978         free_candev(elm->dev);
 979 }
 980
 981 static int elmcan_ldisc_hangup(struct tty_struct *tty)
 982 {
 983         elmcan_ldisc_close(tty);
 984         return 0;
 985 }
 986
 987 /* Perform I/O control on an active elmcan channel. */
 988 static int elmcan_ldisc_ioctl(struct tty_struct *tty, struct file *file,
 989                         unsigned int cmd, unsigned long arg)
 990 {
 991         struct elmcan *elm = (struct elmcan *) tty->disc_data;
 992         unsigned int tmp;
 993
 994         /* First make sure we're connected. */
 995         if (!elm)
 996                 return -EINVAL;
 997
 998         switch (cmd) {
 999         case SIOCGIFNAME:
1000                 tmp = strlen(elm->dev->name) + 1;
1001                 if (copy_to_user((void __user *)arg, elm->dev->name, tmp))
1002                         return -EFAULT;
1003                 return 0;
1004
1005         case SIOCSIFHWADDR:
1006                 return -EINVAL;
1007
1008         default:
1009                 return tty_mode_ioctl(tty, file, cmd, arg);
1010         }
1011 }
1012
1013 static struct tty_ldisc_ops elmcan_ldisc = {
1014         .owner          = THIS_MODULE,
1015         .magic          = TTY_LDISC_MAGIC,
1016         .name           = "elmcan",
1017         .receive_buf    = elmcan_ldisc_rx,
1018         .write_wakeup   = elmcan_ldisc_tx_wakeup,
1019         .open           = elmcan_ldisc_open,
1020         .close          = elmcan_ldisc_close,
1021         .hangup         = elmcan_ldisc_hangup,
1022         .ioctl          = elmcan_ldisc_ioctl,
1023 };
1024
1025
1026
1027
1028
1029  /************************************************************************
1030   *                     Module init/exit                                 *
1031   ************************************************************************/
1032
1033 static int __init elmcan_init(void)
1034 {
1035         int status;
1036
1037         pr_info("ELM327 based best-effort CAN interface driver\n");
1038         pr_info("This device is severely limited as a CAN interface, see documentation.\n");
1039
1040         /* Fill in our line protocol discipline, and register it */
1041         status = tty_register_ldisc(N_ELMCAN, &elmcan_ldisc);
1042         if (status) {
1043                 pr_err("can't register line discipline\n");
1044         }
1045         return status;
1046 }
1047
1048 static void __exit elmcan_exit(void)
1049 {
1050         /* This will only be called when all channels have been closed by
1051          * userspace - tty_ldisc.c takes care of the module's refcount.
1052          */
1053         int status;
1054
1055         status = tty_unregister_ldisc(N_ELMCAN);
1056         if (status) {
1057                 pr_err("Can't unregister line discipline (error: %d)\n", status);
1058         }
1059 }
1060
1061 module_init(elmcan_init);
1062 module_exit(elmcan_exit);