Move loading of RU transport to ru_thread

Harmonize the call to openair0_transport_load(), by putting it in a
single place instead of multiple calls

Further, delay the call to ru_thread, for two reasons:

1) it is somewhat "symmetric" with local RF, which is done there as well

2) for the xran library, we need to read some parameters such as PRACH,
   frame format, etc. At the RU, the corresponding FAPI config request
   parameter structure is copied from the gNB to RU at the beginning of
   the ru_thread, so we have to wait for that to happen.

executables/nr-ru.c

@@ -1168,6 +1168,24 @@ void *ru_thread( void *param ) {
 
     // Start IF device if any
     if (ru->nr_start_if) {
+      LOG_I(PHY, "starting transport\n");
+      ret = openair0_transport_load(&ru->ifdevice, &ru->openair0_cfg, &ru->eth_params);
+      AssertFatal(ret == 0, "RU %u: openair0_transport_init() ret %d: cannot initialize transport protocol\n", ru->idx, ret);
+
+      if (ru->ifdevice.get_internal_parameter != NULL) {
+        /* it seems the device can "overwrite" (request?) to set the callbacks
+         * for fh_south_in()/fh_south_out() differently */
+        void *t = ru->ifdevice.get_internal_parameter("fh_if4p5_south_in");
+        if (t != NULL)
+          ru->fh_south_in = t;
+        t = ru->ifdevice.get_internal_parameter("fh_if4p5_south_out");
+        if (t != NULL)
+          ru->fh_south_out = t;
+      } else {
+
+        malloc_IF4p5_buffer(ru);
+      }
+
       LOG_I(PHY,"Starting IF interface for RU %d, nb_rx %d\n",ru->idx,ru->nb_rx);
       AssertFatal(ru->nr_start_if(ru,NULL) == 0, "Could not start the IF device\n");
 
@@ -1631,8 +1649,6 @@ void init_precoding_weights(PHY_VARS_gNB *gNB) {
 }*/
 
 void set_function_spec_param(RU_t *ru) {
-  int ret;
-
   switch (ru->if_south) {
     case LOCAL_RF:   // this is an RU with integrated RF (RRU, gNB)
       reset_meas(&ru->rx_fhaul);
@@ -1653,13 +1669,6 @@ void set_function_spec_param(RU_t *ru) {
         reset_meas(&ru->tx_fhaul);
         reset_meas(&ru->compression);
         reset_meas(&ru->transport);
-        ret = openair0_transport_load(&ru->ifdevice,&ru->openair0_cfg,&ru->eth_params);
-        printf("openair0_transport_init returns %d for ru_id %u\n", ret, ru->idx);
-
-        if (ret<0) {
-          printf("Exiting, cannot initialize transport protocol\n");
-          exit(-1);
-        }
       } else if (ru->function == NGFI_RRU_IF4p5) {
         ru->do_prach              = 1;                        // do part of prach processing in RU
         ru->fh_north_in           = NULL;                     // no synchronous incoming fronthaul from north
@@ -1676,15 +1685,6 @@ void set_function_spec_param(RU_t *ru) {
         reset_meas(&ru->tx_fhaul);
         reset_meas(&ru->compression);
         reset_meas(&ru->transport);
-        ret = openair0_transport_load(&ru->ifdevice,&ru->openair0_cfg,&ru->eth_params);
-        printf("openair0_transport_init returns %d for ru_id %u\n", ret, ru->idx);
-
-        if (ret<0) {
-          printf("Exiting, cannot initialize transport protocol\n");
-          exit(-1);
-        }
-
-        malloc_IF4p5_buffer(ru);
       } else if (ru->function == gNodeB_3GPP) {
         ru->do_prach             = 0;                       // no prach processing in RU
         ru->feprx                = nr_fep_tp;     // this is frequency-shift + DFTs
@@ -1733,15 +1733,6 @@ void set_function_spec_param(RU_t *ru) {
       ru->ifdevice.eth_params    = &ru->eth_params;
       ru->ifdevice.configure_rru = configure_ru;
 
-      printf("starting transport : rx_num_antennas %d, tx_num_antennas %d\n",ru->openair0_cfg.rx_num_channels,ru->openair0_cfg.tx_num_channels); 
-      ret = openair0_transport_load(&ru->ifdevice,&ru->openair0_cfg,&ru->eth_params);
-      printf("openair0_transport_init returns %d for ru_id %u\n", ret, ru->idx);
-
-      if (ret<0) {
-        printf("Exiting, cannot initialize transport protocol\n");
-        exit(-1);
-      }
-
       break;
 
     case REMOTE_IF4p5:
@@ -1761,27 +1752,6 @@ void set_function_spec_param(RU_t *ru) {
       ru->ifdevice.host_type     = RAU_HOST;
       ru->ifdevice.eth_params    = &ru->eth_params;
       ru->ifdevice.configure_rru = configure_ru;
-      ret = openair0_transport_load(&ru->ifdevice, &ru->openair0_cfg, &ru->eth_params);
-      printf("openair0_transport_init returns %d for ru_id %u\n", ret, ru->idx);
-
-      if (ret<0) {
-        printf("Exiting, cannot initialize transport protocol\n");
-        exit(-1);
-      }
-
-      if (ru->ifdevice.get_internal_parameter != NULL) {
-        void *t = ru->ifdevice.get_internal_parameter("fh_if4p5_south_in");
-
-        if (t != NULL)
-          ru->fh_south_in = t;
-
-        t = ru->ifdevice.get_internal_parameter("fh_if4p5_south_out");
-
-        if (t != NULL)
-          ru->fh_south_out = t;
-      }
-
-      malloc_IF4p5_buffer(ru);
       break;
 
     default: