瞭解初始化，方便從頭捋順整個流程，做到心有框架。
1. java層初始化，引起jni和協議棧部分初始化
(1) AdapterService.java的static塊會在AdapterService整個類初始化的時候調用，static塊裡調用的是classInitNative。
(2) com_android_bluetooth_btservice_AdapterService.cpp的classInitNative接口關鍵部分是：
[1] 拿到java層類接口的回調，以便將來有通知好回調
......
474 method_discoveryStateChangeCallback = env->GetMethodID(jniCallbackClass,
475 "discoveryStateChangeCallback", "(I)V");
476
477 method_devicePropertyChangedCallback = env->GetMethodID(jniCallbackClass,
478 "devicePropertyChangedCallback",
479 "([B[I[[B)V");
480 method_deviceFoundCallback = env->GetMethodID(jniCallbackClass, "deviceFoundCallback", "([B)V");
481 method_pinRequestCallback = env->GetMethodID(jniCallbackClass, "pinRequestCallback",
482 "([B[BI)V");
483 method_sspRequestCallback = env->GetMethodID(jniCallbackClass, "sspRequestCallback",
484 "([B[BIII)V");
......
[2] 加載stack庫，後去stack接口
494 const char *id = (strcmp(value, "1")? BT_STACK_MODULE_ID : BT_STACK_TEST_MODULE_ID);
495
496 err = hw_get_module(id, (hw_module_t const**)&module);
497
498 if (err == 0) {
499 hw_device_t* abstraction;
500 err = module->methods->open(module, id, &abstraction);
501 if (err == 0) {
502 bluetooth_module_t* btStack = (bluetooth_module_t *)abstraction;
503 sBluetoothInterface = btStack->get_bluetooth_interface();
(3) AdapterService這個服務初始化的時候，onCreate被調用，onCreate調用了initNative，initNative也是com_android_bluetooth_btservice_AdapterService.cpp的接口：
[1] 根據(2)裡拿到的interface，初始化interface，傳遞了jni層給interface層的回調，也就是interface層有通知會回調這些接口:
517 if (sBluetoothInterface) {
518 int ret = sBluetoothInterface->init(&sBluetoothCallbacks);
519 if (ret != BT_STATUS_SUCCESS) {
520 ALOGE("Error while setting the callbacks \n");
521 sBluetoothInterface = NULL;
522 return JNI_FALSE;
523 }
[2] 通過bt interface獲取socket interface，這個socket interface是上層使用rfcom通信的關鍵對象。
524 if ( (sBluetoothSocketInterface = (btsock_interface_t *)
525 sBluetoothInterface->get_profile_interface(BT_PROFILE_SOCKETS_ID)) == NULL) {
526 ALOGE("Error getting socket interface");
527 }
(4) (3).[1]調用了，bt interface的init接口，正是bluetooth.c文件中，bluetoothInterface結構的init成員：
346 static const bt_interface_t bluetoothInterface = {
347 sizeof(bt_interface_t),
348 init,
349 enable,
350 disable,
351 cleanup,
這個接口定義在bluetooth.c中，分別：
[1] 保存jni層傳遞下來的回調
bt_hal_cbacks = callbacks;
[2] 調用btif_init_bluetooth();初始化bt interface層；簡單初始化bte, 這個簡單初始化bte實際上有個關鍵的部分：獲取hc接口，下面enable的時候要用到; 獲取本地藍芽地址；創建了一個task，用於bt interface層。
455 btif_config_init();
456 bte_main_boot_entry();會調用bt_hc_if = (bt_hc_interface_t *) bt_hc_get_interface()
457
458 /* As part of the init, fetch the local BD ADDR */
459 memset(&btif_local_bd_addr, 0, sizeof(bt_bdaddr_t));
460 btif_fetch_local_bdaddr(&btif_local_bd_addr);
461
462 /* start btif task */
463 status = GKI_create_task(btif_task, BTIF_TASK, BTIF_TASK_STR,
464 (UINT16 *) ((UINT8 *)btif_task_stack + BTIF_TASK_STACK_SIZE),
465 sizeof(btif_task_stack));
經過以上步驟，java層帶動jni層初始化了協議棧bt interface接口層，創建了一個任務btif_task。java層有jni層的interface，jni層有java層的回調。jni層有協議棧bt interface，協議棧有jni層的回調。
2. bt使能引起的初始化
(1) bt使能調用過程
bt使能由java層發起，自然要發生在1中的java層和jni層初始化之後。
路線是：BluetoothAdapter.getDefaultAdapter().enable (BluetoothAdapter.java)
-> enable (AdapterService.java)
-> mAdapterStateMachine.obtainMessage(AdapterState.USER_TURN_ON); (AdapterService.java)
-> mAdapterService.processStart(); (AdapterState.java)
-> mAdapterStateMachine.sendMessage(mAdapterStateMachine.obtainMessage(AdapterState.STARTED)); (AdapterService.java)
-> boolean ret = mAdapterService.enableNative(); (AdapterState.java)
-> enableNative (AdapterService.java)
-> enableNative (android_bluetooth_btservice_AdapterService.cpp)
-> bluetoothInterface->enable (bluetooth.c)
346 static const bt_interface_t bluetoothInterface = {
347 sizeof(bt_interface_t),
348 init,
349 enable,
bt interface的enable接口，被java經過jni調用下來。
(2) bluetoothInterface的enable接口
調用btif_enable_bluetooth -> bte_main_enable比較關鍵：
166 /* Initialize BTE control block */
167 BTE_Init();
168
169 lpm_enabled = FALSE;
170
171 if (bt_hc_if)
172 {
173 int result = bt_hc_if->init(&hc_callbacks, local_addr); 初始化hc interface，也會同時初始化libbt-vendor.so，也就是hci是libbt-vendor.so相關的。
174 APPL_TRACE_EVENT1("libbt-hci init returns %d", result);
175
176 assert(result == BT_HC_STATUS_SUCCESS);
177
178 if (hci_logging_enabled == TRUE)
179 bt_hc_if->logging(BT_HC_LOGGING_ON, hci_logfile);
180
181 #if (defined (BT_CLEAN_TURN_ON_DISABLED) && BT_CLEAN_TURN_ON_DISABLED == TRUE)
182 APPL_TRACE_DEBUG1("%s Not Turninig Off the BT before Turninig ON", __FUNCTION__);
183
184 /* Do not power off the chip before powering on if BT_CLEAN_TURN_ON_DISABLED flag
185 is defined and set to TRUE to avoid below mentioned issue.
186
187 Wingray kernel driver maintains a combined counter to keep track of
188 BT-Wifi state. Invoking set_power(BT_HC_CHIP_PWR_OFF) when the BT is already
189 in OFF state causes this counter to be incorrectly decremented and results in undesired
190 behavior of the chip.
191
192 This is only a workaround and when the issue is fixed in the kernel this work around
193 should be removed. */
194 #else
195 /* toggle chip power to ensure we will reset chip in case
196 a previous stack shutdown wasn't completed gracefully */
197 bt_hc_if->set_power(BT_HC_CHIP_PWR_OFF);
198 #endif
199 bt_hc_if->set_power(BT_HC_CHIP_PWR_ON);此處比較關鍵，chip已經上電了！
200
201 bt_hc_if->preload(NULL);
202 }
203
204 GKI_create_task((TASKPTR)btu_task, BTU_TASK, BTE_BTU_TASK_STR,
205 (UINT16 *) ((UINT8 *)bte_btu_stack + BTE_BTU_STACK_SIZE),
206 sizeof(bte_btu_stack));
此處又創建了一個任務，btu_task，負責處理bte btu的事件等任務。
(3) btu_task任務初始化部分
170 #if (defined(HCISU_H4_INCLUDED) && HCISU_H4_INCLUDED == TRUE)
171 /* wait an event that HCISU is ready */
172 GKI_wait(0xFFFF, 0);
173 #endif
174 /* Initialize the mandatory core stack control blocks
175 (BTU, BTM, L2CAP, and SDP)
176 */
177 btu_init_core(); 核心協議棧初始化 -> btm_init,l2c_init,sdp_init
178
179 /* Initialize any optional stack components */
180 BTE_InitStack(); 擴展協議初始化RFCOMM_Init,SPP_Init
181
182 #if (defined(BTU_BTA_INCLUDED) && BTU_BTA_INCLUDED == TRUE)
183 bta_sys_init(); bta sys初始化，這裡比較關鍵的是bta_sys_cb.task_id = GKI_get_taskid(),我們會看到bta sys這裡保存的是btu_task這個任務的id，也就是將來bta_sys_sendmsg發送的都是發到btu_task裡的！
184 #endif
185
186 /* Initialise platform trace levels at this point as BTE_InitStack() and bta_sys_init()
187 * reset the control blocks and preset the trace level with XXX_INITIAL_TRACE_LEVEL
188 */
189 #if ( BT_USE_TRACES==TRUE )
190 BTE_InitTraceLevels();
191 #endif
192
193 /* Send a startup evt message to BTIF_TASK to kickstart the init procedure */
194 GKI_send_event(BTIF_TASK, BT_EVT_TRIGGER_STACK_INIT);給bt interface task發事件BT_EVT_TRIGGER_STACK_INIT，告訴bt interface task協議棧已初始化
195
196 raise_priority_a2dp(TASK_HIGH_BTU);
(4) 真正的協議棧使能操作'
bt interface task也就是btif_task處理BT_EVT_TRIGGER_STACK_INIT事件:
btif_task -> BTA_EnableBluetooth接口, 這個接口主要工作是：
84 p_msg->hdr.event = BTA_DM_API_ENABLE_EVT;
85 p_msg->p_sec_cback = p_cback;
86 bta_sys_sendmsg(p_msg);
向btu_task發送BTA_DM_API_ENABLE_EVT事件！
btu_task用下面的代碼：
517 if (event & TASK_MBOX_2_EVT_MASK)
518 {
519 while ((p_msg = (BT_HDR *) GKI_read_mbox(TASK_MBOX_2)) != NULL)
520 {
521 bta_sys_event(p_msg);
522 }
523 }
調用bta_sys_event來處理,bta_sys_event中：
490 BTA_API void bta_sys_event(BT_HDR *p_msg)
491 {
492 UINT8 id;
493 BOOLEAN freebuf = TRUE;
494
495 APPL_TRACE_EVENT1("BTA got event 0x%x", p_msg->event);
496
497 /* get subsystem id from event */
498 id = (UINT8) (p_msg->event >> 8);
499
500 /* verify id and call subsystem event handler */
501 if ((id < BTA_ID_MAX) && (bta_sys_cb.reg[id] != NULL))
502 {
503 freebuf = (*bta_sys_cb.reg[id]->evt_hdlr)(p_msg);
實際就是，先取得事件對應的子系統id，之後回調對應子系統的回調，而子系統是用類似:
bta_sys_register( BTA_ID_SYS, &bta_sys_hw_reg);這樣的接口註冊的！
#define BT_EVT_TRIGGER_STACK_INIT EVENT_MASK(APPL_EVT_0)
#define APPL_EVT_0 8
#define EVENT_MASK(evt) ((UINT16)(0x0001 << (evt)))
那BT_EVT_TRIGGER_STACK_INIT事件對應的子系統就是1，也就是#define BTA_ID_DM 1
搜索BTA_ID_DM是在BTA_EnableBluetooth接口中，bta_sys_register (BTA_ID_DM, &bta_dm_reg );註冊的。也就是：
bta_dm_reg -> bta_dm_sm_execute -> bta_dm_action[0] -> bta_dm_enable:
bta_sys_hw_register( BTA_SYS_HW_BLUETOOTH, bta_dm_sys_hw_cback ); 註冊回調
sys_enable_event->hdr.event = BTA_SYS_API_ENABLE_EVT;發送給btu_task任務事件，經過上邊分析，我們知道這個事件會被註冊的bta_sys_register( BTA_ID_SYS, &bta_sys_hw_reg);的bta_sys_hw_reg->bta_sys_sm_execute處理，
bta_sys_sm_execute -> bta_sys_action -> bta_sys_hw_api_enable -> bta_sys_hw_co_enable -> bta_sys_hw_ci_enabled( module );這個接口又發送 p_msg->hdr.event = BTA_SYS_EVT_ENABLED_EVT;事件。
bta_sys_sm_execute -> bta_sys_action -> bta_sys_hw_evt_enabled -> BTM_DeviceReset( NULL ); -> btm_dev_reset (); -> btsnd_hcic_reset (LOCAL_BR_EDR_CONTROLLER_ID); -> btu_hcif_send_cmd (local_controller_id, p); -> HCI_CMD_TO_LOWER(p_buf); -> bte_main_hci_send -> bt_hc_if->transmit_buf(( -> 被bt_hc_worker_thread線程調用p_hci_if->send(sending_msg_que[i]);調用hci_h4_send_msg -> bytes_sent = userial_write(event,(uint8_t *) p,bytes_to_send); 最終寫到了uart上了！
事情實際上還沒有完，chip雖然reset了，但是上邊還是需要處理reset的狀態！
不過初始化部分就算結束了！
