Function OpenAndCheckGpioChip

wiringPi/wiringPi.c:1730–1770

int OpenAndCheckGpioChip(int GPIONo, const char* label, const unsigned int lines) {
  char szGPIOChip[30];

  sprintf(szGPIOChip, "/dev/gpiochip%d", GPIONo);
  int Fd = open(szGPIOChip, O_RDWR);
  if (Fd < 0) {
    fprintf(stderr, "wiringPi: ERROR: %s open ret=%d\n", szGPIOChip, Fd);
    return Fd;
  } else {
    if (wiringPiDebug) {
      printf("wiringPi: Open chip %s succeded, fd=%d\n", szGPIOChip, Fd) ;
    }
    struct gpiochip_info chipinfo;
    ZeroMemory(&chipinfo, sizeof(chipinfo));
    int ret = ioctl(Fd, GPIO_GET_CHIPINFO_IOCTL, &chipinfo);
    if (0==ret) {
      if (wiringPiDebug) {
        printf("%s: name=%s, label=%s, lines=%u\n", szGPIOChip, chipinfo.name, chipinfo.label, chipinfo.lines) ;
      }
      int chipOK = 1;
      if (label[0]!='\0' && NULL==strstr(chipinfo.label, label)) {
        chipOK = 0;
      }
      if (lines>0 && chipinfo.lines!=lines) {
        chipOK = 0;
      }
      if (chipOK) {
        if (wiringPiDebug) {
          printf("%s: valid, fd=%d\n", szGPIOChip, Fd);
        }
      } else {
        if (wiringPiDebug) {
          printf("%s: invalid, search for '%s' with %u lines!\n", szGPIOChip, label, lines) ;
        }
        close(Fd);
        return -1; // invalid chip
      }
    }
  }
  return Fd;
}

int wiringPiGpioDeviceGetFd() {
  if (chipFd<0) {