nimble/ll: Add option to control initial DLE update

New option allows to select if controller should initiate DLE update
automatically for connection. By default it is enabled to not change
existing controller behavior.

nimble/controller/include/controller/ble_ll_conn.h

@@ -129,7 +129,9 @@ union ble_ll_conn_sm_flags {
         uint32_t aux_conn_req: 1;
         uint32_t rxd_features:1;
         uint32_t pending_hci_rd_features:1;
+#if MYNEWT_VAL(BLE_LL_CONN_INIT_AUTO_DLE)
         uint32_t pending_initiate_dle:1;
+#endif
         uint32_t subrate_trans:1;
         uint32_t subrate_ind_txd:1;
         uint32_t subrate_host_req:1;

nimble/controller/src/ble_ll_ctrl.c

@@ -2137,7 +2137,10 @@ ble_ll_ctrl_update_features(struct ble_ll_conn_sm *connsm, uint8_t *feat)
         }
 #endif
 
+#if MYNEWT_VAL(BLE_LL_CONN_INIT_AUTO_DLE)
         connsm->csmflags.cfbit.pending_initiate_dle = 1;
+#endif
+
         connsm->csmflags.cfbit.rxd_features = 1;
     }
 }
@@ -3050,10 +3053,12 @@ ll_ctrl_send_rsp:
 #endif
     }
 
+#if MYNEWT_VAL(BLE_LL_CONN_INIT_AUTO_DLE)
     if (connsm->csmflags.cfbit.pending_initiate_dle) {
         connsm->csmflags.cfbit.pending_initiate_dle = 0;
         ble_ll_ctrl_initiate_dle(connsm, true);
     }
+#endif
 
     return rc;
 }

nimble/controller/syscfg.yml

@@ -140,11 +140,15 @@ syscfg.defs:
     BLE_LL_CONN_INIT_MAX_TX_BYTES:
         description: >
             Used to set the initial maximum transmit PDU size in a
-            connection. If this is set to a value greater than 27,
-            the controller will automatically attempt to do the
-            data length update procedure. The host can always tell
-            the controller to update this value.
+            connection. The host can always tell the controller to update this
+            value.
         value: '27'
+    BLE_LL_CONN_INIT_AUTO_DLE:
+        description: >
+            If BLE_LL_CONN_INIT_MAX_TX_BYTES is set to value greater than 27
+            controller will automatically attempt to do the data length update
+            procedure.
+        value: 1
 
     # The number of slots that will be allocated to each connection
     BLE_LL_CONN_INIT_SLOTS:

porting/npl/riot/include/syscfg/syscfg.h

@@ -1046,6 +1046,10 @@
 #define MYNEWT_VAL_BLE_LL_CONN_EVENT_END_MARGIN (0)
 #endif
 
+#ifndef MYNEWT_VAL_BLE_LL_CONN_INIT_AUTO_DLE
+#define MYNEWT_VAL_BLE_LL_CONN_INIT_AUTO_DLE (1)
+#endif
+
 /* Overridden by @apache-mynewt-nimble/porting/targets/riot (defined by @apache-mynewt-nimble/nimble/controller) */
 #ifndef MYNEWT_VAL_BLE_LL_CONN_INIT_MAX_TX_BYTES
 #define MYNEWT_VAL_BLE_LL_CONN_INIT_MAX_TX_BYTES (MYNEWT_VAL_BLE_LL_MAX_PKT_SIZE)