S132 v4.0.2 - How to disable DLE or force LL_UNKNOWN_RSP?

Question

Using S132 v4.0.2, is it possible to disable DLE (i.e. make it NOT set the LE Data Packet Length Extension used bit in the LL_FEATURE_RSP)? 
 Alternatively, is there a way to force S132 v4.0.2 to respond to LL_LENGTH_REQ with LL_UNKNOWN_RSP instead of LL_LENGTH_RSP? 
 If either of the above "disable DLE" methods are possible, please let me know how I should modify experimental_ble_app_multiperipheral_pca10040_s132 to achieve this. Thanks!

endnode · Accepted Answer

Isn't default PDU size 27 after enabling S132 V4? Unless you change it you should see that SD rejects any attempt for LL_LENGTH_REQ from the peer (and it shouldn't matter if it responds with L_LENGTH_RSP or LL_UNKNOWN_RSP, PDU length will remain unchanged after it). Also according to this flow chart if LL_LENGTH_REQ is coming from the peer the SD will send event BLE_GAP_EVT_DATA_LENGTH_UPDATE_REQUEST to the APP and it can handle it as needed. Have you tried this to invoke desired LL response over the radio? There are various examples in the SDK which should do it, e.g. this one: 
 #if (NRF_SD_BLE_API_VERSION >= 3)
 case BLE_GAP_EVT_DATA_LENGTH_UPDATE_REQUEST: {
 ble_gap_data_length_params_t const dlp;

 // Clearing the struct will effectively set members to @ref BLE_GAP_DATA_LENGTH_AUTO
 memset(&dlp, 0, sizeof(ble_gap_data_length_params_t));

 // Set struct to default values.
 dlp = {
 .max_rx_octets = 27,
 .max_tx_octets = 27,
 };

 err_code = sd_ble_gap_data_length_update(p_ble_evt->evt.gatts_evt.conn_handle, &dlp, NULL);
 APP_ERROR_CHECK(err_code);
 } break; // BLE_GAP_EVT_DATA_LENGTH_UPDATE_REQUEST
#endif // NRF_SD_BLE_API_VERSION