蓝牙打开从app层到协议栈的跨度太大，仅仅看代码很容易迷失方向，先从log看起。
01-18 18:25:31.570 D/BluetoothAdapterService(21885): onCreate() // adapterservice启动 01-18 18:25:31.570 I/BluetoothVendorJni(21885): classInitNative: succeeds 01-18 18:25:31.570 D/BluetoothAdapterState(21885): make() - Creating AdapterState 01-18 18:25:31.580 I/BluetoothAdapterState(21885): Entering OffState 01-18 18:25:31.580 I/bt_btif (21885): init 然后调用到init方法 01-18 18:25:31.580 D/bt_osi_allocation_tracker(21885): canary initialized 01-18 18:25:31.590 I/bt_osi_thread(21885): run_thread: thread id 21915, thread name stack_manager started
在AdapterService文件里面会先调用classInitNative方法，这个方法的定义在JNI文件中，定义如下：
static void classInitNative(JNIEnv* env, jclass clazz) { int err; hw_module_t* module; jclass jniCallbackClass = env->FindClass("com/android/bluetooth/btservice/JniCallbacks"); sJniCallbacksField = env->GetFieldID(clazz, "mJniCallbacks", "Lcom/android/bluetooth/btservice/JniCallbacks;"); method_stateChangeCallback = env->GetMethodID(jniCallbackClass, "stateChangeCallback", "(I)V"); method_adapterPropertyChangedCallback = env->GetMethodID(jniCallbackClass, "adapterPropertyChangedCallback", "([I[[B)V"); method_discoveryStateChangeCallback = env->GetMethodID(jniCallbackClass, "discoveryStateChangeCallback", "(I)V"); method_devicePropertyChangedCallback = env->GetMethodID(jniCallbackClass, "devicePropertyChangedCallback", "([B[I[[B)V"); method_deviceFoundCallback = env->GetMethodID(jniCallbackClass, "deviceFoundCallback", "([B)V"); method_pinRequestCallback = env->GetMethodID(jniCallbackClass, "pinRequestCallback", "([B[BIZ)V"); method_sspRequestCallback = env->GetMethodID(jniCallbackClass, "sspRequestCallback", "([B[BIII)V"); method_bondStateChangeCallback = env->GetMethodID(jniCallbackClass, "bondStateChangeCallback", "(I[BI)V"); method_aclStateChangeCallback = env->GetMethodID(jniCallbackClass, "aclStateChangeCallback", "(I[BI)V"); method_setWakeAlarm = env->GetMethodID(clazz, "setWakeAlarm", "(JZ)Z"); method_acquireWakeLock = env->GetMethodID(clazz, "acquireWakeLock", "(Ljava/lang/String;)Z"); method_releaseWakeLock = env->GetMethodID(clazz, "releaseWakeLock", "(Ljava/lang/String;)Z"); method_energyInfo = env->GetMethodID(clazz, "energyInfoCallback", "(IIJJJJ)V"); char value[PROPERTY_VALUE_MAX]; property_get("bluetooth.mock_stack", value, ""); const char *id = (strcmp(value, "1")? BT_STACK_MODULE_ID : BT_STACK_TEST_MODULE_ID); err = hw_get_module(id, (hw_module_t const**)&module); if (err == 0) { hw_device_t* abstraction; err = module->methods->open(module, id, &abstraction); if (err == 0) { bluetooth_module_t* btStack = (bluetooth_module_t *)abstraction; sBluetoothInterface = btStack->get_bluetooth_interface(); } else { ALOGE("Error while opening Bluetooth library"); } } else { ALOGE("No Bluetooth Library found"); }该方法中会定义一些回调函数，并且初始化sBluetoothInterface接口, get_bluetooth_interface方法返回协议栈里面定义的方法的接口，协议栈中的方法如下所示：
static const bt_interface_t bluetoothInterface = { sizeof(bluetoothInterface), init, enable, disable, cleanup, get_adapter_properties, get_adapter_property, set_adapter_property, get_remote_device_properties, get_remote_device_property, set_remote_device_property, get_remote_service_record, get_remote_services, start_discovery, cancel_discovery, create_bond, remove_bond, cancel_bond, get_connection_state, pin_reply, ssp_reply, get_profile_interface, dut_mode_configure, dut_mode_send, #if BLE_INCLUDED == TRUE le_test_mode, #else NULL, #endif config_hci_snoop_log, set_os_callouts, read_energy_info, dump, config_clear };将会调用到协议里面的init方法。
static int init(bt_callbacks_t *callbacks) { LOG_INFO("%s", __func__); if (interface_ready()) return BT_STATUS_DONE; #ifdef BLUEDROID_DEBUG allocation_tracker_init(); #endif bt_hal_cbacks = callbacks; stack_manager_get_interface()->init_stack(); btif_debug_init(); return BT_STATUS_SUCCESS; }在init里面会创建stack_manager线程，然后使用thread_post方法给stack_manager线程传递处理函数event_init_stack，这个函数主要用来初始化协议栈，在函数里面会调用btif_init_bluetooth, btif_init_bluetooth函数里面创建JNI线程，给这个线程传递的处理函数是run_message_loop。
至此，蓝牙协议栈初始化完成，下面进入enable过程。
01-18 18:25:31.760 I/bt_btif (21885): enable: start restricted = 0 01-18 18:25:31.760 I/bt_stack_manager(21885): event_start_up_stack is bringing up the stack
enable方法中会给stack_manager线程传递处理函数event_start_up_stack,在event_start_up_stack函数中会创建 bt_workqueue线程，该线程中的处理方法是：btu_task_start_up
01-18 18:25:31.870 I/bt_osi_thread(21885): run_thread: thread id 21934, thread name bt_workqueue started
在btu_task_start_up方法中，会初始化BTU,BTM,L2CAP,SDP. 创建btu message_loop线程，给该线程传入的处理函数是
btu_message_loop_run函数, 这个函数向JNI线程发送初始化完成的消息。
