example of service request with reset attempt for zephyrproject-rtos/zephyr pr #21090

fragment.c

int err;
struct k_poll_signal sig;
struct onoff_client cli;

/* Blocking start using signal */
struct k_poll_event evts[] = {
  K_POLL_EVENT_INITIALIZER(K_POLL_TYPE_SIGNAL,
                           K_POLL_MODE_NOTIFY_ONLY,
                           &sig),
};
while (true) {
  /* Request the service. */
  k_poll_signal_reset(&sig);
  onoff_client_init_signal(&cli, &sig);
  err = onoff_request(srv, cli);
  if ((err < 0) && (err != -EIO)) {
    /* All errors other than -EIO are unrecoverable (except -EAGAIN
     * which is only theoretical and could warrant trying again),
     * probably due to being in an unsupported context or some other
     * error. */
    break;
  }

  /* Wait for result unless service is in error state, in which case
   * we proceed directly to attempting a reset. */
  if (err != -EIO) {
    unsigned int signaled;
    int result;

    err = k_poll(evts, ARRAY_SIZE(evts), K_FOREVER);
    if (err != 0) { /* k_poll failed */
      break;
    }

    k_poll_signal_check(&sig, &signaled, &err);
    /* Assume no need to checked signaled */

    if (err == -EWOULDBLOCK) {
      /* Loop back and try again hoping this time the operation will
       * be invoked from a supported context. */
      continue;
    }

    if (err >= 0) {
      /* Success, service is on.  Note: Services may indicate success
       * with a positive value. */
      break;
    }

    /* Asynchronous operation failed.  Service is probably in an error
     * state, but may be recoverable.  Continue into reset code. */
  }

  /* Service may be in an error state.  Try to reset it. */
  k_poll_signal_reset(&sig);
  onoff__init_signal(&cli, &sig);
  err = onoff_service_reset(srv, cli);

  if ((err == 0) || (err == -EALREADY)) {
    /* Service is not in error state. Try the request again. */
    continue;
  }

  if (err < 0) {
    /* Service cannot be reset */
    break;
  }

  /* Wait for the reset result */
  err = k_poll(evts, ARRAY_SIZE(evts), K_FOREVER);
  if (err != 0) { /* k_poll failed */
    break;
  }

  k_poll_signal_check(&sig, &signaled, &err);
  /* Assume no need to checked signaled */

  if (err < 0) {
    /* Failure to reset cannot be recovered from here. */
    break;
  }
  /* Reset succeeded, try again */
}

/* Check err: service is on if value is non-negative. */