refactor(split): allow central to define connection parameters

Fixes zmkfirmware#1614

Author: xudongzheng

app/src/split/bluetooth/Kconfig

@@ -33,6 +33,18 @@ config ZMK_SPLIT_BLE_CENTRAL_SPLIT_RUN_QUEUE_SIZE
     int "Max number of behavior run events to queue to send to the peripheral(s)"
     default 5
 
+config ZMK_SPLIT_BLE_PREF_INT
+    int "Connection interval to use for split central/peripheral connection"
+    default 6
+
+config ZMK_SPLIT_BLE_PREF_LATENCY
+    int "Latency to use for split central/peripheral connection"
+    default 30
+
+config ZMK_SPLIT_BLE_PREF_TIMEOUT
+    int "Supervision timeout to use for split central/peripheral connection"
+    default 400
+
 endif # ZMK_SPLIT_ROLE_CENTRAL
 
 if !ZMK_SPLIT_ROLE_CENTRAL
@@ -58,8 +70,9 @@ config BT_MAX_PAIRED
 config BT_MAX_CONN
     default 1
 
-config BT_PERIPHERAL_PREF_MAX_INT
-    default 6
+# Allow central to specify connection parameters.
+config BT_GAP_AUTO_UPDATE_CONN_PARAMS
+    default n
 
 #!ZMK_SPLIT_ROLE_CENTRAL
 endif

app/src/split/bluetooth/central.c

@@ -383,7 +383,9 @@ static bool split_central_eir_found(const bt_addr_le_t *addr) {
     struct peripheral_slot *slot = &peripherals[slot_idx];
 
     LOG_DBG("Initiating new connnection");
-    struct bt_le_conn_param *param = BT_LE_CONN_PARAM(0x0006, 0x0006, 30, 400);
+    struct bt_le_conn_param *param =
+        BT_LE_CONN_PARAM(CONFIG_ZMK_SPLIT_BLE_PREF_INT, CONFIG_ZMK_SPLIT_BLE_PREF_INT,
+                         CONFIG_ZMK_SPLIT_BLE_PREF_LATENCY, CONFIG_ZMK_SPLIT_BLE_PREF_TIMEOUT);
     err = bt_conn_le_create(addr, BT_CONN_LE_CREATE_CONN, param, &slot->conn);
     if (err < 0) {
         LOG_ERR("Create conn failed (err %d) (create conn? 0x%04x)", err, BT_HCI_OP_LE_CREATE_CONN);