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   * (all functions assume elm->lock taken)                      *
 129   ************************************************************************/
 130
 131 static void elm327_send(struct elmcan *elm, const void *buf, size_t len)
 132 {
 133         int actual;
 134
 135         memcpy(elm->txbuf, buf, len);
 136
 137         /* Order of next two lines is *very* important.
 138          * When we are sending a little amount of data,
 139          * the transfer may be completed inside the ops->write()
 140          * routine, because it's running with interrupts enabled.
 141          * In this case we *never* got WRITE_WAKEUP event,
 142          * if we did not request it before write operation.
 143          *       14 Oct 1994  Dmitry Gorodchanin.
 144          */
 145         set_bit(TTY_DO_WRITE_WAKEUP, &elm->tty->flags);
 146         actual = elm->tty->ops->write(elm->tty, elm->txbuf, len);
 147         elm->txleft = len - actual;
 148         elm->txhead = elm->txbuf + actual;
 149 }
 150
 151
 152 /*
 153  * Take the ELM327 out of almost any state and back into command mode
 154  *
 155  * Assumes elm->lock taken.
 156  */
 157 static void elm327_kick_into_cmd_mode(struct elmcan *elm)
 158 {
 159         if (elm->state != ELM_GETMAGICCHAR && elm->state != ELM_GETPROMPT) {
 160                 elm327_send(elm, ELM327_MAGIC_STRING, 1);
 161
 162                 elm->state = ELM_GETMAGICCHAR;
 163                 elm->rxfill = 0;
 164         }
 165 }
 166
 167
 168 /*
 169  * Schedule a CAN frame, and any necessary config changes,
 170  * to be sent down the TTY.
 171  *
 172  * Assumes elm->lock taken.
 173  */
 174 static void elm327_send_frame(struct elmcan *elm, struct can_frame *frame)
 175 {
 176         /* Schedule any necessary changes in ELM327's CAN configuration */
 177         if (elm->can_frame.can_id != frame->can_id) {
 178                 /* Set the new CAN ID for transmission. */
 179                 if ((frame->can_id & CAN_EFF_FLAG) ^ (elm->can_frame.can_id & CAN_EFF_FLAG)) {
 180                         elm->can_config = (frame->can_id & CAN_EFF_FLAG ? 0 : ELM327_CAN_CONFIG_SEND_SFF)
 181                                         | ELM327_CAN_CONFIG_VARIABLE_DLC
 182                                         | ELM327_CAN_CONFIG_RECV_BOTH_SFF_EFF
 183                                         | elm->can_bitrate_divisor;
 184
 185                         set_bit(ELM_TODO_CAN_CONFIG, &elm->cmds_todo);
 186                 }
 187
 188                 if (frame->can_id & CAN_EFF_FLAG) {
 189                         clear_bit(ELM_TODO_CANID_11BIT, &elm->cmds_todo);
 190                         set_bit(ELM_TODO_CANID_29BIT_LOW, &elm->cmds_todo);
 191                         set_bit(ELM_TODO_CANID_29BIT_HIGH, &elm->cmds_todo);
 192                 } else {
 193                         set_bit(ELM_TODO_CANID_11BIT, &elm->cmds_todo);
 194                         clear_bit(ELM_TODO_CANID_29BIT_LOW, &elm->cmds_todo);
 195                         clear_bit(ELM_TODO_CANID_29BIT_HIGH, &elm->cmds_todo);
 196                 }
 197         }
 198
 199         /* Schedule the CAN frame itself. */
 200         elm->can_frame = *frame;
 201         set_bit(ELM_TODO_CAN_DATA, &elm->cmds_todo);
 202
 203         elm327_kick_into_cmd_mode(elm);
 204 }
 205
 206
 207
 208  /************************************************************************
 209   *             ELM327: Initialization sequence                 *
 210   *                                                             *
 211   * (assumes elm->lock taken)                                   *
 212   ************************************************************************/
 213
 214 static char *elm327_init_script[] = {
 215         "AT WS\r",        /* v1.0: Warm Start */
 216         "AT PP FF OFF\r", /* v1.0: All Programmable Parameters Off */
 217         "AT M0\r",        /* v1.0: Memory Off */
 218         "AT AL\r",        /* v1.0: Allow Long messages */
 219         "AT BI\r",        /* v1.0: Bypass Initialization */
 220         "AT CAF0\r",      /* v1.0: CAN Auto Formatting Off */
 221         "AT CFC0\r",      /* v1.0: CAN Flow Control Off */
 222         "AT CF 000\r",    /* v1.0: Reset CAN ID Filter */
 223         "AT CM 000\r",    /* v1.0: Reset CAN ID Mask */
 224         "AT E1\r",        /* v1.0: Echo On */
 225         "AT H1\r",        /* v1.0: Headers On */
 226         "AT L0\r",        /* v1.0: Linefeeds Off */
 227         "AT SH 7DF\r",    /* v1.0: Set CAN sending ID to 0x7df */
 228         "AT ST FF\r",     /* v1.0: Set maximum Timeout for response after TX */
 229         "AT AT0\r",       /* v1.2: Adaptive Timing Off */
 230         "AT D1\r",        /* v1.3: Print DLC On */
 231         "AT S1\r",        /* v1.3: Spaces On */
 232         "AT TP B\r",      /* v1.0: Try Protocol B */
 233         NULL
 234 };
 235
 236
 237 static void elm327_init(struct elmcan *elm)
 238 {
 239         elm->state = ELM_NOTINIT;
 240         elm->can_frame.can_id = 0x7df;
 241         elm->rxfill = 0;
 242         elm->drop_next_line = 0;
 243
 244         /* We can only set the bitrate as a fraction of 500000.
 245          * The bit timing constants in elmcan_bittiming_const will
 246          * limit the user to the right values.
 247          */
 248         elm->can_bitrate_divisor = 500000 / elm->can.bittiming.bitrate;
 249         elm->can_config = ELM327_CAN_CONFIG_SEND_SFF
 250                         | ELM327_CAN_CONFIG_VARIABLE_DLC
 251                         | ELM327_CAN_CONFIG_RECV_BOTH_SFF_EFF
 252                         | elm->can_bitrate_divisor;
 253
 254         /* Configure ELM327 and then start monitoring */
 255         elm->next_init_cmd = &elm327_init_script[0];
 256         set_bit(ELM_TODO_INIT, &elm->cmds_todo);
 257         set_bit(ELM_TODO_SILENT_MONITOR, &elm->cmds_todo);
 258         set_bit(ELM_TODO_RESPONSES, &elm->cmds_todo);
 259         set_bit(ELM_TODO_CAN_CONFIG, &elm->cmds_todo);
 260
 261         elm327_kick_into_cmd_mode(elm);
 262 }
 263
 264
 265
 266  /************************************************************************
 267   *             ELM327: Reception -> netdev glue                *
 268   *                                                             *
 269   * (assumes elm->lock taken)                                   *
 270   ************************************************************************/
 271
 272 static void elm327_feed_frame_to_netdev(struct elmcan *elm, const struct can_frame *frame)
 273 {
 274         struct can_frame *cf;
 275         struct sk_buff *skb;
 276
 277         if (!netif_running(elm->dev)) {
 278                 return;
 279         }
 280
 281         skb = alloc_can_skb(elm->dev, &cf);
 282
 283         if (!skb)
 284                 return;
 285
 286         memcpy(cf, frame, sizeof(struct can_frame));
 287
 288         elm->dev->stats.rx_packets++;
 289         elm->dev->stats.rx_bytes += frame->can_dlc;
 290         netif_rx_ni(skb);
 291
 292         can_led_event(elm->dev, CAN_LED_EVENT_RX);
 293 }
 294
 295
 296
 297  /************************************************************************
 298   *             ELM327: Panic handler                           *
 299   *                                                             *
 300   * (assumes elm->lock taken)                                   *
 301   ************************************************************************/
 302
 303 static inline void elm327_panic(struct elmcan *elm)
 304 {
 305         struct can_frame frame = {0};
 306
 307         frame.can_id = CAN_ERR_FLAG | CAN_ERR_RESTARTED;
 308         frame.can_dlc = CAN_ERR_DLC;
 309         elm327_feed_frame_to_netdev(elm, &frame);
 310
 311         pr_err("ELM327 misbehaved. Re-initializing.\n");
 312
 313         elm->can.can_stats.restarts++;
 314         elm327_init(elm);
 315 }
 316
 317
 318
 319  /************************************************************************
 320   *             ELM327: Reception parser                        *
 321   *                                                             *
 322   * (assumes elm->lock taken)                                   *
 323   ************************************************************************/
 324
 325 static void elm327_parse_error(struct elmcan *elm, int len)
 326 {
 327         struct can_frame frame = {0};
 328
 329         frame.can_id = CAN_ERR_FLAG;
 330         frame.can_dlc = CAN_ERR_DLC;
 331
 332         switch(len) {
 333                 case 17:
 334                         if (!memcmp(elm->rxbuf, "UNABLE TO CONNECT", 17)) {
 335                                 pr_err("The ELM327 reported UNABLE TO CONNECT. Please check your setup.\n");
 336                         }
 337                         break;
 338                 case 11:
 339                         if (!memcmp(elm->rxbuf, "BUFFER FULL", 11)) {
 340                                 /* This case will only happen if the last data
 341                                  * line was complete.
 342                                  * Otherwise, elm327_parse_frame() will emit the
 343                                  * error frame instead.
 344                                  */
 345                                 frame.can_id |= CAN_ERR_CRTL;
 346                                 frame.data[1] = CAN_ERR_CRTL_RX_OVERFLOW;
 347                         }
 348                         break;
 349                 case 9:
 350                         if (!memcmp(elm->rxbuf, "BUS ERROR", 9)) {
 351                                 frame.can_id |= CAN_ERR_BUSERROR;
 352                         }
 353                         if (!memcmp(elm->rxbuf, "CAN ERROR", 9)
 354                                 || !memcmp(elm->rxbuf, "<RX ERROR", 9)) {
 355                                 frame.can_id |= CAN_ERR_PROT;
 356                         }
 357                         break;
 358                 case 8:
 359                         if (!memcmp(elm->rxbuf, "BUS BUSY", 8)) {
 360                                 frame.can_id |= CAN_ERR_PROT;
 361                                 frame.data[2] = CAN_ERR_PROT_OVERLOAD;
 362                         }
 363                         if (!memcmp(elm->rxbuf, "FB ERROR", 8)) {
 364                                 frame.can_id |= CAN_ERR_PROT;
 365                                 frame.data[2] = CAN_ERR_PROT_TX;
 366                         }
 367                         break;
 368                 case 5:
 369                         if (!memcmp(elm->rxbuf, "ERR", 3)) {
 370                                 pr_err("The ELM327 reported an ERR%c%c. Please power it off and on again.\n",
 371                                         elm->rxbuf[3], elm->rxbuf[4]);
 372                                 frame.can_id |= CAN_ERR_CRTL;
 373                         }
 374                         break;
 375                 default:
 376                         /* Don't emit an error frame if we're unsure */
 377                         return;
 378         }
 379
 380         elm327_feed_frame_to_netdev(elm, &frame);
 381 }
 382
 383
 384 static int elm327_parse_frame(struct elmcan *elm, int len)
 385 {
 386         struct can_frame frame = {0};
 387         int hexlen;
 388         int datastart;
 389         int i;
 390
 391         /* Find first non-hex and non-space character:
 392          *  - In the simplest case, there is none.
 393          *  - For RTR frames, 'R' is the first non-hex character.
 394          *  - An error message may replace the end of the data line.
 395          */
 396         for (hexlen = 0; hexlen <= len; hexlen++) {
 397                 if (hex_to_bin(elm->rxbuf[hexlen]) < 0
 398                     && elm->rxbuf[hexlen] != ' ') {
 399                         break;
 400                 }
 401         }
 402
 403         /* Use spaces in CAN ID to distinguish 29 or 11 bit address length.
 404          * No out-of-bounds access:
 405          * We use the fact that we can always read from elm->rxbuf.
 406          */
 407         if (elm->rxbuf[2] == ' ' && elm->rxbuf[5] == ' '
 408                 && elm->rxbuf[8] == ' ' && elm->rxbuf[11] == ' '
 409                 && elm->rxbuf[13] == ' ') {
 410                 frame.can_id = CAN_EFF_FLAG;
 411                 datastart = 14;
 412         } else if (elm->rxbuf[3] == ' ' && elm->rxbuf[5] == ' ') {
 413                 frame.can_id = 0;
 414                 datastart = 6;
 415         } else {
 416                 /* This is not a well-formatted data line.
 417                  * Assume it's an error message.
 418                  */
 419                 return 1;
 420         }
 421
 422         if (hexlen < datastart) {
 423                 /* The line is too short to be a valid frame hex dump.
 424                  * Something interrupted the hex dump or it is invalid.
 425                  */
 426                 return 1;
 427         }
 428
 429         /* From here on all chars up to buf[hexlen] are hex or spaces,
 430          * at well-defined offsets.
 431          */
 432
 433         /* Read CAN data length */
 434         frame.can_dlc = (hex_to_bin(elm->rxbuf[datastart - 2]) << 0);
 435
 436         /* Read CAN ID */
 437         if (frame.can_id & CAN_EFF_FLAG) {
 438                 frame.can_id |= (hex_to_bin(elm->rxbuf[0]) << 28)
 439                               | (hex_to_bin(elm->rxbuf[1]) << 24)
 440                               | (hex_to_bin(elm->rxbuf[3]) << 20)
 441                               | (hex_to_bin(elm->rxbuf[4]) << 16)
 442                               | (hex_to_bin(elm->rxbuf[6]) << 12)
 443                               | (hex_to_bin(elm->rxbuf[7]) << 8)
 444                               | (hex_to_bin(elm->rxbuf[9]) << 4)
 445                               | (hex_to_bin(elm->rxbuf[10]) << 0);
 446         } else {
 447                 frame.can_id |= (hex_to_bin(elm->rxbuf[0]) << 8)
 448                               | (hex_to_bin(elm->rxbuf[1]) << 4)
 449                               | (hex_to_bin(elm->rxbuf[2]) << 0);
 450         }
 451
 452         /* Check for RTR frame */
 453         if (elm->rxfill >= hexlen + 3
 454             && elm->rxbuf[hexlen + 0] == 'R'
 455             && elm->rxbuf[hexlen + 1] == 'T'
 456             && elm->rxbuf[hexlen + 2] == 'R') {
 457                 frame.can_id |= CAN_RTR_FLAG;
 458         }
 459
 460         /* Is the line long enough to hold the advertised payload? */
 461         if (!(frame.can_id & CAN_RTR_FLAG) && (hexlen < frame.can_dlc * 3 + datastart)) {
 462                 /* Incomplete frame. */
 463
 464                 /* Probably the ELM327's RS232 TX buffer was full.
 465                  * Emit an error frame and exit.
 466                  */
 467                 frame.can_id = CAN_ERR_FLAG | CAN_ERR_CRTL;
 468                 frame.can_dlc = CAN_ERR_DLC;
 469                 frame.data[1] = CAN_ERR_CRTL_RX_OVERFLOW;
 470                 elm327_feed_frame_to_netdev(elm, &frame);
 471
 472                 /* Signal failure to parse.
 473                  * The line will be re-parsed as an error line, which will fail.
 474                  * However, this will correctly drop the state machine back into
 475                  * command mode.
 476                  */
 477                 return 2;
 478         }
 479
 480         /* Parse the data nibbles. */
 481         for (i = 0; i < frame.can_dlc; i++) {
 482                 frame.data[i] = (hex_to_bin(elm->rxbuf[datastart+3*i]) << 4)
 483                                 | (hex_to_bin(elm->rxbuf[datastart+3*i+1]) << 0);
 484         }
 485
 486         /* Feed the frame to the network layer. */
 487         elm327_feed_frame_to_netdev(elm, &frame);
 488
 489         return 0;
 490 }
 491
 492
 493 static void elm327_parse_line(struct elmcan *elm, int len)
 494 {
 495         /* Skip empty lines */
 496         if (!len) {
 497                 return;
 498         }
 499
 500         /* Skip echo lines */
 501         if (elm->drop_next_line) {
 502                 elm->drop_next_line = 0;
 503                 return;
 504         } else if (elm->rxbuf[0] == 'A' && elm->rxbuf[1] == 'T') {
 505                 return;
 506         }
 507
 508         /* Regular parsing */
 509         switch(elm->state) {
 510                 case ELM_RECEIVING:
 511                         if (elm327_parse_frame(elm, len)) {
 512                                 /* Parse an error line. */
 513                                 elm327_parse_error(elm, len);
 514
 515                                 /* After the error line, we expect a prompt. */
 516                                 elm->state = ELM_GETPROMPT;
 517                         }
 518                         break;
 519                 default:
 520                         break;
 521         }
 522 }
 523
 524
 525 static void elm327_handle_prompt(struct elmcan *elm)
 526 {
 527         if (elm->cmds_todo) {
 528                 struct can_frame *frame = &elm->can_frame;
 529                 char txbuf[20];
 530
 531                 if (test_bit(ELM_TODO_INIT, &elm->cmds_todo)) {
 532                         elm327_send(elm, *elm->next_init_cmd, strlen(*elm->next_init_cmd));
 533                         elm->next_init_cmd++;
 534                         if (!(*elm->next_init_cmd)) {
 535                                 clear_bit(ELM_TODO_INIT, &elm->cmds_todo);
 536                                 pr_info("%s: Initialization finished.\n", elm->dev->name);
 537                         }
 538
 539                         /* Some chips are unreliable and need extra time after
 540                          * init commands, as seen with a clone.
 541                          * So let's do a dummy get-cmd-prompt dance.
 542                          */
 543                         elm->state = ELM_NOTINIT;
 544                         elm327_kick_into_cmd_mode(elm);
 545                 } else if (test_and_clear_bit(ELM_TODO_SILENT_MONITOR, &elm->cmds_todo)) {
 546                         snprintf(txbuf, sizeof(txbuf), "ATCSM%i\r", !(!(elm->can.ctrlmode & CAN_CTRLMODE_LISTENONLY)));
 547                 } else if (test_and_clear_bit(ELM_TODO_RESPONSES, &elm->cmds_todo)) {
 548                         snprintf(txbuf, sizeof(txbuf), "ATR%i\r", !(elm->can.ctrlmode & CAN_CTRLMODE_LISTENONLY));
 549                 } else if (test_and_clear_bit(ELM_TODO_CAN_CONFIG, &elm->cmds_todo)) {
 550                         snprintf(txbuf, sizeof(txbuf), "ATPB%04X\r", elm->can_config);
 551                 } else if (test_and_clear_bit(ELM_TODO_CANID_29BIT_HIGH, &elm->cmds_todo)) {
 552                         snprintf(txbuf, sizeof(txbuf), "ATCP%02X\r", (frame->can_id & CAN_EFF_MASK) >> 24);
 553                 } else if (test_and_clear_bit(ELM_TODO_CANID_29BIT_LOW, &elm->cmds_todo)) {
 554                         snprintf(txbuf, sizeof(txbuf), "ATSH%06X\r", frame->can_id & CAN_EFF_MASK & ((1 << 24) - 1));
 555                 } else if (test_and_clear_bit(ELM_TODO_CANID_11BIT, &elm->cmds_todo)) {
 556                         snprintf(txbuf, sizeof(txbuf), "ATSH%03X\r", frame->can_id & CAN_SFF_MASK);
 557                 } else if (test_and_clear_bit(ELM_TODO_CAN_DATA, &elm->cmds_todo)) {
 558                         if (frame->can_id & CAN_RTR_FLAG) {
 559                                 snprintf(txbuf, sizeof(txbuf), "ATRTR\r");
 560                         } else {
 561                                 int i;
 562
 563                                 for (i = 0; i < frame->can_dlc; i++) {
 564                                         sprintf(&txbuf[2*i], "%02X", frame->data[i]);
 565                                 }
 566
 567                                 sprintf(&txbuf[2*i], "\r");
 568                         }
 569
 570                         elm->drop_next_line = 1;
 571                         elm->state = ELM_RECEIVING;
 572                 }
 573
 574                 elm327_send(elm, txbuf, strlen(txbuf));
 575         } else {
 576                 /* Enter CAN monitor mode */
 577                 elm327_send(elm, "ATMA\r", 5);
 578                 elm->state = ELM_RECEIVING;
 579         }
 580 }
 581
 582
 583 static void elm327_drop_bytes(struct elmcan *elm, int i)
 584 {
 585         memmove(&elm->rxbuf[0], &elm->rxbuf[i], sizeof(elm->rxbuf) - i);
 586         elm->rxfill -= i;
 587 }
 588
 589
 590 static void elm327_parse_rxbuf(struct elmcan *elm)
 591 {
 592         int len;
 593
 594         switch (elm->state) {
 595         case ELM_NOTINIT:
 596                 elm->rxfill = 0;
 597                 return;
 598
 599         case ELM_GETMAGICCHAR:
 600         {
 601                 /* Wait for 'y' or '>' */
 602                 int i;
 603
 604                 for (i = 0; i < elm->rxfill; i++) {
 605                         if (elm->rxbuf[i] == ELM327_MAGIC_CHAR) {
 606                                 elm327_send(elm, "\r", 1);
 607                                 elm->state = ELM_GETPROMPT;
 608                                 i++;
 609                                 break;
 610                         } else if (elm->rxbuf[i] == '>') {
 611                                 elm327_send(elm, ELM327_MAGIC_STRING, 1);
 612                                 i++;
 613                                 break;
 614                         }
 615                 }
 616
 617                 elm327_drop_bytes(elm, i);
 618
 619                 return;
 620         }
 621
 622         case ELM_GETPROMPT:
 623                 /* Wait for '>' */
 624                 if (elm->rxbuf[elm->rxfill - 1] == '>') {
 625                         elm327_handle_prompt(elm);
 626                 }
 627
 628                 elm->rxfill = 0;
 629                 return;
 630
 631         case ELM_RECEIVING:
 632                 /* Find <CR> delimiting feedback lines. */
 633                 for (len = 0;
 634                      (len < elm->rxfill) && (elm->rxbuf[len] != '\r');
 635                      len++) {
 636                         /* empty loop */
 637                 }
 638
 639                 if (len == sizeof(elm->rxbuf)) {
 640                         /* Line exceeds buffer. It's probably all garbage.
 641                          * Did we even connect at the right baud rate?
 642                          */
 643                         pr_err("RX buffer overflow. Faulty ELM327 connected?\n");
 644                         elm327_panic(elm);
 645                 } else if (len == elm->rxfill) {
 646                         if (elm->state == ELM_RECEIVING
 647                                 && elm->rxbuf[elm->rxfill - 1] == '>') {
 648                                 /* The ELM327's AT ST response timeout ran out,
 649                                  * so we got a prompt.
 650                                  * Clear RX buffer and restart listening.
 651                                  */
 652                                 elm->rxfill = 0;
 653
 654                                 elm327_handle_prompt(elm);
 655                                 return;
 656                         } else {
 657                                 /* We haven't received a full line yet.
 658                                  * Wait for more data.
 659                                  */
 660                                 return;
 661                         }
 662                 }
 663
 664                 /* We have a full line to parse. */
 665                 elm327_parse_line(elm, len);
 666
 667                 /* Remove parsed data from RX buffer. */
 668                 elm327_drop_bytes(elm, len+1);
 669
 670                 /* More data to parse? */
 671                 if (elm->rxfill) {
 672                         elm327_parse_rxbuf(elm);
 673                 }
 674         }
 675 }
 676
 677
 678
 679
 680
 681  /************************************************************************
 682   *             netdev                                          *
 683   *                                                             *
 684   * (takes elm->lock)                                           *
 685   ************************************************************************/
 686
 687 /* Netdevice DOWN -> UP routine */
 688 static int elmcan_netdev_open(struct net_device *dev)
 689 {
 690         struct elmcan *elm = netdev_priv(dev);
 691         int err;
 692
 693         spin_lock_bh(&elm->lock);
 694         if (elm->tty == NULL) {
 695                 spin_unlock_bh(&elm->lock);
 696                 return -ENODEV;
 697         }
 698
 699         /* open_candev() checks for elm->can.bittiming.bitrate != 0 */
 700         err = open_candev(dev);
 701         if (err) {
 702                 spin_unlock_bh(&elm->lock);
 703                 return err;
 704         }
 705
 706         /* Initialize the ELM327 */
 707         elm327_init(elm);
 708         spin_unlock_bh(&elm->lock);
 709
 710         can_led_event(dev, CAN_LED_EVENT_OPEN);
 711         elm->can.state = CAN_STATE_ERROR_ACTIVE;
 712         netif_start_queue(dev);
 713
 714         return 0;
 715 }
 716
 717 /* Netdevice UP -> DOWN routine */
 718 static int elmcan_netdev_close(struct net_device *dev)
 719 {
 720         struct elmcan *elm = netdev_priv(dev);
 721
 722         spin_lock_bh(&elm->lock);
 723         if (elm->tty) {
 724                 /* TTY discipline is running. */
 725
 726                 /* Interrupt whatever we're doing right now */
 727                 elm327_send(elm, ELM327_MAGIC_STRING, 1);
 728
 729                 /* Clear the wakeup bit, as the netdev will be down and thus
 730                  * the wakeup handler won't clear it
 731                  */
 732                 clear_bit(TTY_DO_WRITE_WAKEUP, &elm->tty->flags);
 733
 734                 spin_unlock_bh(&elm->lock);
 735
 736                 flush_work(&elm->tx_work);
 737         } else {
 738                 spin_unlock_bh(&elm->lock);
 739         }
 740
 741         elm->can.state = CAN_STATE_STOPPED;
 742         netif_stop_queue(dev);
 743         close_candev(dev);
 744         can_led_event(dev, CAN_LED_EVENT_STOP);
 745
 746         return 0;
 747 }
 748
 749 /* Send a can_frame to a TTY queue. */
 750 static netdev_tx_t elmcan_netdev_start_xmit(struct sk_buff *skb, struct net_device *dev)
 751 {
 752         struct elmcan *elm = netdev_priv(dev);
 753         struct can_frame *frame = (struct can_frame *) skb->data;
 754
 755         if (skb->len != sizeof(struct can_frame))
 756                 goto out;
 757
 758         if (!netif_running(dev))  {
 759                 pr_warn("%s: xmit: iface is down\n", dev->name);
 760                 goto out;
 761         }
 762
 763         /* BHs are already disabled, so no spin_lock_bh().
 764          * See Documentation/networking/netdevices.txt
 765          */
 766         spin_lock(&elm->lock);
 767         if (elm->tty == NULL
 768                 || elm->can.ctrlmode & CAN_CTRLMODE_LISTENONLY) {
 769                 spin_unlock(&elm->lock);
 770                 goto out;
 771         }
 772
 773         netif_stop_queue(dev);
 774
 775         elm327_send_frame(elm, frame);
 776         spin_unlock(&elm->lock);
 777
 778         dev->stats.tx_packets++;
 779         dev->stats.tx_bytes += frame->can_dlc;
 780
 781         can_led_event(dev, CAN_LED_EVENT_TX);
 782
 783 out:
 784         kfree_skb(skb);
 785         return NETDEV_TX_OK;
 786 }
 787
 788 static int elmcan_netdev_change_mtu(struct net_device *dev, int new_mtu)
 789 {
 790         return -EINVAL;
 791 }
 792
 793 static const struct net_device_ops elmcan_netdev_ops = {
 794         .ndo_open       = elmcan_netdev_open,
 795         .ndo_stop       = elmcan_netdev_close,
 796         .ndo_start_xmit = elmcan_netdev_start_xmit,
 797         .ndo_change_mtu = elmcan_netdev_change_mtu,
 798 };
 799
 800
 801
 802
 803
 804  /************************************************************************
 805   *             Line discipline                                 *
 806   *                                                             *
 807   * (takes elm->lock)                                           *
 808   ************************************************************************/
 809
 810 /*
 811  * Handle the 'receiver data ready' interrupt.
 812  * This function is called by the 'tty_io' module in the kernel when
 813  * a block of ELM327 CAN data has been received, which can now be parsed
 814  * and sent on to some IP layer for further processing. This will not
 815  * be re-entered while running but other ldisc functions may be called
 816  * in parallel
 817  */
 818 static void elmcan_ldisc_rx(struct tty_struct *tty,
 819                         const unsigned char *cp, char *fp, int count)
 820 {
 821         struct elmcan *elm = (struct elmcan *) tty->disc_data;
 822
 823         if (!elm)
 824                 return;
 825
 826         /* Read the characters out of the buffer */
 827         while (count-- && elm->rxfill < sizeof(elm->rxbuf)) {
 828                 if (fp && *fp++) {
 829                         pr_err("Error in received character stream. Check your wiring.");
 830
 831                         spin_lock_bh(&elm->lock);
 832                         elm327_panic(elm);
 833                         spin_unlock_bh(&elm->lock);
 834                         return;
 835                 }
 836                 if (*cp != 0) {
 837                         elm->rxbuf[elm->rxfill++] = *cp;
 838                 }
 839                 cp++;
 840         }
 841
 842         if (count >= 0) {
 843                 pr_err("Receive buffer overflowed. Bad chip or wiring?");
 844
 845                 spin_lock_bh(&elm->lock);
 846                 elm327_panic(elm);
 847                 spin_unlock_bh(&elm->lock);
 848                 return;
 849         }
 850
 851         spin_lock_bh(&elm->lock);
 852         elm327_parse_rxbuf(elm);
 853         spin_unlock_bh(&elm->lock);
 854 }
 855
 856 /*
 857  * Write out remaining transmit buffer.
 858  * Scheduled when TTY is writable.
 859  */
 860 static void elmcan_ldisc_tx_worker(struct work_struct *work)
 861 {
 862         struct elmcan *elm = container_of(work, struct elmcan, tx_work);
 863         ssize_t actual;
 864
 865         spin_lock_bh(&elm->lock);
 866         /* First make sure we're connected. */
 867         if (!elm->tty || !netif_running(elm->dev)) {
 868                 spin_unlock_bh(&elm->lock);
 869                 return;
 870         }
 871
 872         if (elm->txleft <= 0)  {
 873                 /* Our TTY write buffer is empty:
 874                  * We can start transmission of another packet
 875                  */
 876                 clear_bit(TTY_DO_WRITE_WAKEUP, &elm->tty->flags);
 877                 spin_unlock_bh(&elm->lock);
 878                 netif_wake_queue(elm->dev);
 879                 return;
 880         }
 881
 882         actual = elm->tty->ops->write(elm->tty, elm->txhead, elm->txleft);
 883         if (actual < 0) {
 884                 pr_err("Failed to write to tty for %s.\n", elm->dev->name);
 885                 elm327_panic(elm);
 886         }
 887
 888         elm->txleft -= actual;
 889         elm->txhead += actual;
 890         spin_unlock_bh(&elm->lock);
 891 }
 892
 893
 894 /*
 895  * Called by the driver when there's room for more data.
 896  * Schedule the transmit.
 897  */
 898 static void elmcan_ldisc_tx_wakeup(struct tty_struct *tty)
 899 {
 900         struct elmcan *elm = tty->disc_data;
 901
 902         schedule_work(&elm->tx_work);
 903 }
 904
 905
 906
 907 /* Some fake bit timings to allow bitrate setting */
 908 static const struct can_bittiming_const elmcan_bittiming_const = {
 909         .name = "elmcan",
 910         .tseg1_min = 1,
 911         .tseg1_max = 1,
 912         .tseg2_min = 0,
 913         .tseg2_max = 0,
 914         .sjw_max = 1,
 915         .brp_min = 1,
 916         .brp_max = 500,
 917         .brp_inc = 1,
 918 };
 919
 920 /*
 921  * Open the high-level part of the elmcan channel.
 922  * This function is called by the TTY module when the
 923  * elmcan line discipline is called for.
 924  *
 925  * Called in process context serialized from other ldisc calls.
 926  */
 927 static int elmcan_ldisc_open(struct tty_struct *tty)
 928 {
 929         struct net_device *dev;
 930         struct elmcan *elm;
 931         int err;
 932
 933         if (!capable(CAP_NET_ADMIN))
 934                 return -EPERM;
 935
 936         if (!tty->ops->write)
 937                 return -EOPNOTSUPP;
 938
 939         elm = tty->disc_data;
 940
 941         /* First make sure we're not already connected.
 942          * Also, protect against simlutaneous open calls. */
 943         spin_lock_bh(&elmcan_open_lock);
 944         if (elm) {
 945                 spin_unlock_bh(&elmcan_open_lock);
 946                 return -EEXIST;
 947         }
 948         spin_unlock_bh(&elmcan_open_lock);
 949
 950         /* OK.  Find a free elmcan channel to use. */
 951         dev = alloc_candev(sizeof(struct elmcan), 0);
 952         if (!dev)
 953                 return -ENFILE;
 954         elm = netdev_priv(dev);
 955
 956         /* Configure TTY interface */
 957         tty->receive_room = 65536; /* We don't flow control */
 958         elm->txleft = 0; /* Clear TTY TX buffer */
 959         spin_lock_init(&elm->lock);
 960         INIT_WORK(&elm->tx_work, elmcan_ldisc_tx_worker);
 961
 962         /* Configure CAN metadata */
 963         elm->can.state = CAN_STATE_STOPPED;
 964         elm->can.clock.freq = 1000000;
 965         elm->can.bittiming_const = &elmcan_bittiming_const;
 966         elm->can.ctrlmode_supported = CAN_CTRLMODE_LISTENONLY;
 967
 968         /* Configure netlink interface */
 969         elm->dev = dev;
 970         dev->netdev_ops = &elmcan_netdev_ops;
 971
 972         /* Mark ldisc channel as alive */
 973         elm->tty = tty;
 974         tty->disc_data = elm;
 975
 976         devm_can_led_init(elm->dev);
 977
 978         /* Let 'er rip */
 979         err = register_candev(elm->dev);
 980         if (err) {
 981                 free_candev(elm->dev);
 982                 return err;
 983         }
 984
 985         return 0;
 986 }
 987
 988 /*
 989  * Close down an elmcan channel.
 990  * This means flushing out any pending queues, and then returning.
 991  * This call is serialized against other ldisc functions:
 992  * Once this is called, no other ldisc function of ours is entered.
 993  *
 994  * We also use this function for a hangup event.
 995  */
 996 static void elmcan_ldisc_close(struct tty_struct *tty)
 997 {
 998         struct elmcan *elm = (struct elmcan *) tty->disc_data;
 999
1000         /* First make sure we're connected. */
1001         if (!elm)
1002                 return;
1003
1004         /* Flush network side */
1005         unregister_candev(elm->dev);
1006
1007         /* Mark channel as dead */
1008         spin_lock_bh(&elm->lock);
1009         tty->disc_data = NULL;
1010         elm->tty = NULL;
1011         spin_unlock_bh(&elm->lock);
1012
1013         /* Flush TTY side */
1014         flush_work(&elm->tx_work);
1015
1016         /* Free our memory */
1017         free_candev(elm->dev);
1018 }
1019
1020 static int elmcan_ldisc_hangup(struct tty_struct *tty)
1021 {
1022         elmcan_ldisc_close(tty);
1023         return 0;
1024 }
1025
1026 /* Perform I/O control on an active elmcan channel. */
1027 static int elmcan_ldisc_ioctl(struct tty_struct *tty, struct file *file,
1028                         unsigned int cmd, unsigned long arg)
1029 {
1030         struct elmcan *elm = (struct elmcan *) tty->disc_data;
1031         unsigned int tmp;
1032
1033         /* First make sure we're connected. */
1034         if (!elm)
1035                 return -EINVAL;
1036
1037         switch (cmd) {
1038         case SIOCGIFNAME:
1039                 tmp = strlen(elm->dev->name) + 1;
1040                 if (copy_to_user((void __user *)arg, elm->dev->name, tmp))
1041                         return -EFAULT;
1042                 return 0;
1043
1044         case SIOCSIFHWADDR:
1045                 return -EINVAL;
1046
1047         default:
1048                 return tty_mode_ioctl(tty, file, cmd, arg);
1049         }
1050 }
1051
1052 static struct tty_ldisc_ops elmcan_ldisc = {
1053         .owner          = THIS_MODULE,
1054         .magic          = TTY_LDISC_MAGIC,
1055         .name           = "elmcan",
1056         .receive_buf    = elmcan_ldisc_rx,
1057         .write_wakeup   = elmcan_ldisc_tx_wakeup,
1058         .open           = elmcan_ldisc_open,
1059         .close          = elmcan_ldisc_close,
1060         .hangup         = elmcan_ldisc_hangup,
1061         .ioctl          = elmcan_ldisc_ioctl,
1062 };
1063
1064
1065
1066
1067
1068  /************************************************************************
1069   *             Module init/exit                                *
1070   ************************************************************************/
1071
1072 static int __init elmcan_init(void)
1073 {
1074         int status;
1075
1076         pr_info("ELM327 based best-effort CAN interface driver\n");
1077         pr_info("This device is severely limited as a CAN interface, see documentation.\n");
1078
1079         /* Fill in our line protocol discipline, and register it */
1080         status = tty_register_ldisc(N_ELMCAN, &elmcan_ldisc);
1081         if (status) {
1082                 pr_err("can't register line discipline\n");
1083         }
1084         return status;
1085 }
1086
1087 static void __exit elmcan_exit(void)
1088 {
1089         /* This will only be called when all channels have been closed by
1090          * userspace - tty_ldisc.c takes care of the module's refcount.
1091          */
1092         int status;
1093
1094         status = tty_unregister_ldisc(N_ELMCAN);
1095         if (status) {
1096                 pr_err("Can't unregister line discipline (error: %d)\n", status);
1097         }
1098 }
1099
1100 module_init(elmcan_init);
1101 module_exit(elmcan_exit);