openpilot_comma/board/safety/safety_elm327.h

static void elm327_rx_hook(CAN_FIFOMailBox_TypeDef *to_push) {}

static int elm327_tx_hook(CAN_FIFOMailBox_TypeDef *to_send) {
  //All ELM traffic must appear on CAN0
  if(((to_send->RDTR >> 4) & 0xf) != 0) return 0;
  //All ISO 15765-4 messages must be 8 bytes long
  if((to_send->RDTR & 0xf) != 8) return 0;

  if(to_send->RIR & 4){
    uint32_t addr = to_send->RIR >> 3;
    //Check valid 29 bit send addresses for ISO 15765-4
    if(!(addr == 0x18DB33F1 || (addr & 0x1FFF00FF) == 0x18DA00F1)) return 0;
  } else {
    uint32_t addr = to_send->RIR >> 21;
    //Check valid 11 bit send addresses for ISO 15765-4
    if(!(addr == 0x7DF || (addr & 0x7F8) == 0x7E0)) return 0;
  }

  return true;
}

static int elm327_tx_lin_hook(int lin_num, uint8_t *data, int len) {
  if(lin_num != 0) return false; //Only operate on LIN 0, aka serial 2
  if(len < 5 || len > 11) return false; //Valid KWP size
  if(!((data[0] & 0xF8) == 0xC0 && (data[0] & 0x07) > 0 &&
       data[1] == 0x33 && data[2] == 0xF1)) return false; //Bad msg
  return true;
}

static void elm327_init(int16_t param) {
  controls_allowed = 1;
}

static int elm327_ign_hook() {
  return -1;
}

static int elm327_fwd_hook(int bus_num, CAN_FIFOMailBox_TypeDef *to_fwd) {
  return -1;
}

const safety_hooks elm327_hooks = {
  .init = elm327_init,
  .rx = elm327_rx_hook,
  .tx = elm327_tx_hook,
  .tx_lin = elm327_tx_lin_hook,
  .ignition = elm327_ign_hook,
  .fwd = elm327_fwd_hook,
};