A configuration structure for the CSMA transmit algorithm.

One of RAIL's schemes for polite spectrum access is an implementation of a Carrier-Sense Multiple Access (CSMA) algorithm based on IEEE 802.15.4 (unslotted).
In pseudo-code it works like this, showing relevant event notifications:

// Return true to transmit packet, false to not transmit packet.
bool perform_csma(const sl_rail_csma_config_t *csma_config)
{
  extern int idle_to_rx_us;
  bool is_fixed_backoff = ((csma_config->csma_min_bo_exp == 0)
                           && (csma_config->csma_max_bo_exp == 0));
  int backoff_exp = csma_config->csma_min_bo_exp; // Initial backoff exponent
  int backoff_multiplier = 1; // Assume fixed backoff
  int try;

  // Special-case tries == 0 to transmit immediately without backoff+CCA
  if (csma_config->csma_tries == 0) {
    return true;
  }

  // Start overall timeout if specified:
  if (csma_config->csma_timeout_us > 0) {
    start_abort_timer(csma_config->csma_timeout_us, SL_RAIL_EVENT_TX_CHANNEL_BUSY);
    // If timeout occurs, abort and signal the indicated event.
  }

  for (try = 0; try < csma_config->csma_tries; try++) {
    if (try > 0) {
      signal_event(SL_RAIL_EVENT_TX_CCA_RETRY);
    }
    // Determine the backoff multipler for this try:
    if (is_fixed_backoff) {
      // backoff_multiplier already set to 1 for fixed backoff
    } else {
      // Start with the backoff exponent for this try:
      if (try > 0) {
        backoff_exp++;
        if (backoff_exp > csma_config->csma_max_bo_exp) {
          backoff_exp = csma_config->csma_max_bo_exp;
        }
      }
      // Pick random multiplier between 0 and 2^backoff_exp - 1 inclusive:
      backoff_multiplier = pick_random_integer(0, (1 << backoff_exp) - 1);
    }
    // Perform the backoff:
    if (backoff_multiplier > 0) {
      delay_microseconds((backoff_multiplier * csma_config->cca_backoff_us)
                         - idle_to_rx_us);
    }
    enable_radio_receive();
    signal_event(SL_RAIL_EVENT_TX_START_CCA);
    delay_microseconds(idle_to_rx_us);
    // Perform the Clear-Channel Assessment (CCA):
    // Channel is considered busy if radio is actively receiving or
    // transmitting, or the energy detected during the duration period
    // is above the threshold.
    signal_event(SL_RAIL_EVENT_TX_CCA_ACTIVATED);
    if (perform_cca(csma_config->cca_duration_us, csma_config->cca_threshold_dbm)) {
      // CCA (and CSMA) success: Transmit after RX-to-TX turnaround
      stop_abort_timer();
      signal_event(SL_RAIL_EVENT_TX_CHANNEL_CLEAR);
      return true;
    } else {
      // CCA failed: loop to try again, or exit if out of tries
    }
  }
  // Overall CSMA failure: Don't transmit
  stop_abort_timer();
  signal_event(SL_RAIL_EVENT_TX_CHANNEL_BUSY);
  return false;
}