A2dp初始化流程源码分析
蓝牙启动的时候，会涉及到各个profile 的启动。这篇文章分析一下，蓝牙中a2dp profile的初始化流程。
我们从AdapterState.java中对于USER_TURN_ON 消息的处理说起：
switch(msg.what) {
case USER_TURN_ON:
notifyAdapterStateChange(BluetoothAdapter.STATE_TURNING_ON);
mPendingCommandState.setTurningOn(true);
transitionTo(mPendingCommandState);
sendMessageDelayed(BREDR_START_TIMEOUT, BREDR_START_TIMEOUT_DELAY);
adapterService.startCoreServices();//开始启动核心的服务，就是各种profile
break;
继续看：
void startCoreServices()
{
debugLog("startCoreServices()");
Class[] supportedProfileServices = Config.getSupportedProfiles(); //Start profile services
if (!mProfilesStarted && supportedProfileServices.length >) {
//Startup all profile services
setProfileServiceState(supportedProfileServices,BluetoothAdapter.STATE_ON);//start all profile
}
...
}
看看setProfileServiceState的实现，他就是实现一个for 循环，在里面启动所有的profile：
private void setProfileServiceState(Class[] services, int state) {
if (state != BluetoothAdapter.STATE_ON && state != BluetoothAdapter.STATE_OFF) {
debugLog("setProfileServiceState() - Invalid state, leaving...");
return;
}
int expectedCurrentState= BluetoothAdapter.STATE_OFF;
int pendingState = BluetoothAdapter.STATE_TURNING_ON;
if (state == BluetoothAdapter.STATE_OFF) {
expectedCurrentState= BluetoothAdapter.STATE_ON;
pendingState = BluetoothAdapter.STATE_TURNING_OFF;
}
for (int i=; i <services.length;i++) {
String serviceName = services[i].getName();
String simpleName = services[i].getSimpleName();
if (simpleName.equals("GattService")) continue;
Integer serviceState = mProfileServicesState.get(serviceName);
if(serviceState != null && serviceState != expectedCurrentState) {
debugLog("setProfileServiceState() - Unable to "
+ (state == BluetoothAdapter.STATE_OFF ? "start" : "stop" )
+ " service " + serviceName
+ ". Invalid state: " + serviceState);
continue;
}
debugLog("setProfileServiceState() - "
+ (state == BluetoothAdapter.STATE_OFF ? "Stopping" : "Starting")
+ " service " + serviceName);
mProfileServicesState.put(serviceName,pendingState);
Intent intent = new Intent(this,services[i]);
intent.putExtra(EXTRA_ACTION,ACTION_SERVICE_STATE_CHANGED);
intent.putExtra(BluetoothAdapter.EXTRA_STATE,state);
startService(intent);//启动服务
}
}
startSerice 启动服务，我们这里只分析a2dp的情况，其他的profile的启动情况类似。a2dp 对应的service 文件是a2dpService.java，下面看看service的启动：
public void onCreate() {
if (DBG) log("onCreate");
super.onCreate();
mAdapter = BluetoothAdapter.getDefaultAdapter();
mBinder = initBinder();//生成一个Binder
mAdapterService = AdapterService.getAdapterService();
if (mAdapterService != null) {
mAdapterService.addProfile(this);
} else {
Log.w(TAG, "onCreate, null mAdapterService");
}
}
我们看看a2dpService是如何实现这个mBInder的：
protected IProfileServiceBinder initBinder() {
return new BluetoothA2dpBinder(this);//传入一个 this 指针，那么也就是说a2dpService 这个类本身就是这个service
}
看看这个BluetoothA2dpBinder 是一个什么样的接口？其实他就是对原本的服务的一个封装，包含了原来的服务
//Binder object: Must be static class or memory leak may occur
private static class BluetoothA2dpBinder extends IBluetoothA2dp.Stub
implements IProfileServiceBinder {
private A2dpService mService; private A2dpService getService() {
if (!Utils.checkCaller()) {
Log.w(TAG,"A2dp call not allowed for non-active user");
return null;
} if (mService != null && mService.isAvailable()) {
return mService;
}
return null;
} BluetoothA2dpBinder(A2dpService svc) {
mService = svc;//构造函数传入的this 参数
} public boolean cleanup() {
mService = null;
return true;
} public boolean connect(BluetoothDevice device) {
A2dpService service = getService();
if (service == null) return false;
return service.connect(device);
} public boolean disconnect(BluetoothDevice device) {
A2dpService service = getService();
if (service == null) return false;
return service.disconnect(device);
} public List<BluetoothDevice> getConnectedDevices() {
A2dpService service = getService();
if (service == null) return new ArrayList<BluetoothDevice>(0);
return service.getConnectedDevices();
} public List<BluetoothDevice> getDevicesMatchingConnectionStates(int[] states) {
A2dpService service = getService();
if (service == null) return new ArrayList<BluetoothDevice>(0);
return service.getDevicesMatchingConnectionStates(states);
} public int getConnectionState(BluetoothDevice device) {
A2dpService service = getService();
if (service == null) return BluetoothProfile.STATE_DISCONNECTED;
return service.getConnectionState(device);
} public boolean setPriority(BluetoothDevice device, int priority) {
A2dpService service = getService();
if (service == null) return false;
return service.setPriority(device, priority);
} public int getPriority(BluetoothDevice device) {
A2dpService service = getService();
if (service == null) return BluetoothProfile.PRIORITY_UNDEFINED;
return service.getPriority(device);
} public boolean isAvrcpAbsoluteVolumeSupported() {
A2dpService service = getService();
if (service == null) return false;
return service.isAvrcpAbsoluteVolumeSupported();
} public void adjustAvrcpAbsoluteVolume(int direction) {
A2dpService service = getService();
if (service == null) return;
service.adjustAvrcpAbsoluteVolume(direction);
} public void setAvrcpAbsoluteVolume(int volume) {
A2dpService service = getService();
if (service == null) return;
service.setAvrcpAbsoluteVolume(volume);
} public boolean isA2dpPlaying(BluetoothDevice device) {
A2dpService service = getService();
if (service == null) return false;
return service.isA2dpPlaying(device);
}
}
这个mBinder 会在别的应用程序绑定的时候，返回给对方。所以其就是对原本服务的一个封装。
接着我们看onStartCommand：
public int onStartCommand(Intent intent, int flags, int startId) {
...
String action = intent.getStringExtra(AdapterService.EXTRA_ACTION);
if (AdapterService.ACTION_SERVICE_STATE_CHANGED.equals(action)) {
int state= intent.getIntExtra(BluetoothAdapter.EXTRA_STATE, BluetoothAdapter.ERROR);
if(state==BluetoothAdapter.STATE_OFF) {
Log.d(mName, "Received stop request...Stopping profile...");
doStop(intent);
} else if (state == BluetoothAdapter.STATE_ON) {
Log.d(mName, "Received start request. Starting profile...");
doStart(intent);//启动
}
}
return PROFILE_SERVICE_MODE;
}
继续看：
private void doStart(Intent intent) {
//Start service
if (mAdapter == null) {
Log.e(mName, "Error starting profile. BluetoothAdapter is null");
} else {
if (DBG) log("start()");
mStartError = !start();//这个是虚函数，看看a2dpService 具体如何实现的
if (!mStartError) {
notifyProfileServiceStateChanged(BluetoothAdapter.STATE_ON);上报状态
} else {
Log.e(mName, "Error starting profile. BluetoothAdapter is null");
}
}
}
上报的状态的部分就不分析了，我们直接看 start的部分：
avrcp的部分暂时略过，
protected boolean start() {
mAvrcp = Avrcp.make(this);
mStateMachine = A2dpStateMachine.make(this, this);//启动状态机
setA2dpService(this);//设置a2dpService服务为本身sAd2dpService = this
return true;
}
看看状态机make 函数到底干嘛？猜想应该是初始化状态机：
static A2dpStateMachine make(A2dpService svc, Context context) {
A2dpStateMachine a2dpSm = new A2dpStateMachine(svc, context);//新建一个状态机
a2dpSm.start();//start
return a2dpSm;
}
这里的start就是让状态机转起来，和a2dp 的关系不大，这里不分析 了，我们这里的重头戏是new A2dpStateMachine，这里涉及到一些 变量、状态的初始化，以及协议栈中关于a2dp的初始化。
private A2dpStateMachine(A2dpService svc, Context context) {
super("A2dpStateMachine");
mService = svc;//a2dpService
mContext = context;//a2dpService
mAdapter = BluetoothAdapter.getDefaultAdapter();
initNative();//native 函数
mDisconnected = new Disconnected();//新建各种状态，类中类
mPending = new Pending();
mConnected = new Connected();
addState(mDisconnected);//往状态机中添加状态
addState(mPending);
addState(mConnected);
setInitialState(mDisconnected);//设置初始状态
PowerManager pm = (PowerManager)context.getSystemService(Context.POWER_SERVICE);
mWakeLock = pm.newWakeLock(PowerManager.PARTIAL_WAKE_LOCK, "BluetoothA2dpService");
mIntentBroadcastHandler = new IntentBroadcastHandler();
mAudioManager = (AudioManager) context.getSystemService(Context.AUDIO_SERVICE);
}
如果我们不往JNI 层以下分析的话，那么应用层的Service的初始化的流程已经完成了。
这里调用initNative其实就是 对JNI 层以及协议栈进行a2dp 的初始化，我们这里也分析一下：
static void initNative(JNIEnv *env, jobject object) {
const bt_interface_t* btInf;
bt_status_t status;
...
if ( (sBluetoothA2dpInterface = (btav_interface_t *)
btInf->get_profile_interface(BT_PROFILE_ADVANCED_AUDIO_ID)) == NULL) {//获取a2dp的接口
ALOGE("Failed to get Bluetooth A2DP Interface");
return;
}
if ( (status = sBluetoothA2dpInterface->init(&sBluetoothA2dpCallbacks)) != BT_STATUS_SUCCESS) {//对接口进行初始化
ALOGE("Failed to initialize Bluetooth A2DP, status: %d", status);
sBluetoothA2dpInterface = NULL;
return;
}
mCallbacksObj = env->NewGlobalRef(object);
}
我们先看一下 这个接口实现在那里，其实现在btif_av.c中，从这里开始就是C代码实现的了。
static const btav_interface_t bt_av_src_interface = {
.size = sizeof(btav_interface_t),
.init = init_src,
.connect = src_connect_sink,
.disconnect = disconnect,
.cleanup = cleanup_src,
};
那我们继续看 其init的实现：
/*******************************************************************************
**
** Function init_src
**
** Description Initializes the AV interface for source mode
**
** Returns bt_status_t
**
*******************************************************************************/ static bt_status_t init_src(btav_callbacks_t* callbacks)
{
bt_status_t status = btif_av_init();
if (status == BT_STATUS_SUCCESS)
bt_av_src_callbacks = callbacks;//保存JNI层的callback
上面的callback 是JNI 层 注册下来的，猜想，应该都是一些状态上报的callback，我们看看 都有哪些函数：
static btav_callbacks_t sBluetoothA2dpCallbacks = {
sizeof(sBluetoothA2dpCallbacks),
bta2dp_connection_state_callback,//连接状态上报
bta2dp_audio_state_callback//audio的状态上报
};
下面我们关注一下btif_av_init的实现：
/*******************************************************************************
**
** Function btif_av_init
**
** Description Initializes btif AV if not already done
**
** Returns bt_status_t
**
*******************************************************************************/ bt_status_t btif_av_init()
{
if (btif_av_cb.sm_handle == NULL)
{
if (!btif_a2dp_start_media_task())//开启media 的线程
return BT_STATUS_FAIL; /* Also initialize the AV state machine */
btif_av_cb.sm_handle =
btif_sm_init((const btif_sm_handler_t*)btif_av_state_handlers, BTIF_AV_STATE_IDLE);//初始化协议栈层面的btif里的状态机 btif_enable_service(BTA_A2DP_SOURCE_SERVICE_ID);//enable source service #if (BTA_AV_SINK_INCLUDED == TRUE)
btif_enable_service(BTA_A2DP_SINK_SERVICE_ID);
btif_a2dp_on_init();//啥也没干
} return BT_STATUS_SUCCESS;
}
这里还涉及到sink的部分，暂时不讲。
上面的代码流程分为两个部分：
- 开启media task的流程
- btif_sm 的初始化
- btif_enable_service(BTA_A2DP_SOURCE_SERVICE_ID)
我们先看第一部分：
开启media task的流程
bool btif_a2dp_start_media_task(void)
{
...
btif_media_cmd_msg_queue = fixed_queue_new(SIZE_MAX);//新建一个队列用于处理media 相关的cmd /* start a2dp media task */
worker_thread = thread_new("media_worker");//新建一个media_worker 县城 fixed_queue_register_dequeue(btif_media_cmd_msg_queue,
thread_get_reactor(worker_thread),
btif_media_thread_handle_cmd,
NULL);将队列和thread绑定 thread_post(worker_thread, btif_media_thread_init, NULL);//post 到media 线程中继续media 线程的init 行为 APPL_TRACE_EVENT("## A2DP MEDIA THREAD STARTED ##");
return true;
}
这里我们看看，会有哪些cmd 会塞到这个队列里面去处理：
/* BTIF media cmd event definition : BTIF_MEDIA_TASK_CMD */
enum
{
BTIF_MEDIA_START_AA_TX = ,
BTIF_MEDIA_STOP_AA_TX,
BTIF_MEDIA_AA_RX_RDY,
BTIF_MEDIA_UIPC_RX_RDY,
BTIF_MEDIA_SBC_ENC_INIT,
BTIF_MEDIA_SBC_ENC_UPDATE,
BTIF_MEDIA_SBC_DEC_INIT,
BTIF_MEDIA_VIDEO_DEC_INIT,
BTIF_MEDIA_FLUSH_AA_TX,
BTIF_MEDIA_FLUSH_AA_RX,
BTIF_MEDIA_AUDIO_FEEDING_INIT,
BTIF_MEDIA_AUDIO_RECEIVING_INIT,
BTIF_MEDIA_AUDIO_SINK_CFG_UPDATE,
BTIF_MEDIA_AUDIO_SINK_CLEAR_TRACK
}
下面我们分析下 btif_media_thread_init都做了哪些事情：
static void btif_media_thread_init(UNUSED_ATTR void *context) {
memset(&btif_media_cb, , sizeof(btif_media_cb));
UIPC_Init(NULL);
#if (BTA_AV_INCLUDED == TRUE)
UIPC_Open(UIPC_CH_ID_AV_CTRL , btif_a2dp_ctrl_cb);//打开了audio的控制通道
#endif
raise_priority_a2dp(TASK_HIGH_MEDIA);//提升优先级
media_task_running = MEDIA_TASK_STATE_ON;//标志线程状态
}
我们现在看看
btif_sm 的初始化
/*****************************************************************************
**
** Function btif_sm_init
**
** Description Initializes the state machine with the state handlers
** The caller should ensure that the table and the corresponding
** states match. The location that 'p_handlers' points to shall
** be available until the btif_sm_shutdown API is invoked.
**
** Returns Returns a pointer to the initialized state machine handle.
**
******************************************************************************/ btif_sm_handle_t btif_sm_init(const btif_sm_handler_t *p_handlers, btif_sm_state_t initial_state)
{
btif_sm_cb_t *p_cb; if (p_handlers == NULL)
{
BTIF_TRACE_ERROR("%s : p_handlers is NULL", __FUNCTION__);
return NULL;
} p_cb = (btif_sm_cb_t *)osi_malloc(sizeof(btif_sm_cb_t));
p_cb->state = initial_state;//初始状态
p_cb->p_handlers = (btif_sm_handler_t*)p_handlers;一组函数指针 /* Send BTIF_SM_ENTER_EVT to the initial state */
p_cb->p_handlers[initial_state](BTIF_SM_ENTER_EVT, NULL);//进入到初始状态 return (btif_sm_handle_t)p_cb;
}
这个函数 是要返回一个btif_sm_handle_t 结构给btif_av_cb.sm_handle，这个结构，里面包含一个state以及函数指针 ，如下：
typedef struct {
btif_sm_state_t state;
btif_sm_handler_t *p_handlers;
} btif_sm_cb_t;
我们现在看看，这个函数进行初始化的时候传入的函数指针 有哪些：
static const btif_sm_handler_t btif_av_state_handlers[] =
{
btif_av_state_idle_handler,
btif_av_state_opening_handler,
btif_av_state_opened_handler,
btif_av_state_started_handler,
btif_av_state_closing_handler
};
我们发现是 不同状态下的处理句柄。最后我们看看（BTIF_SM_ENTER_EVT）进入初始状态，有执行什么操作：
static BOOLEAN btif_av_state_idle_handler(btif_sm_event_t event, void *p_data)
{
BTIF_TRACE_DEBUG("%s event:%s flags %x", __FUNCTION__,
dump_av_sm_event_name(event), btif_av_cb.flags); switch (event)
{
case BTIF_SM_ENTER_EVT:
/* clear the peer_bda */
memset(&btif_av_cb.peer_bda, , sizeof(bt_bdaddr_t));
btif_av_cb.flags = ;
btif_av_cb.edr = ;
btif_a2dp_on_idle();//btif_media_cb 设置为idle，reset audio_codec_config
break;
下面我们看看
btif_enable_service(BTA_A2DP_SOURCE_SERVICE_ID);
/*******************************************************************************
**
** Function btif_enable_service
**
** Description Enables the service 'service_ID' to the service_mask.
** Upon BT enable, BTIF core shall invoke the BTA APIs to
** enable the profiles
**
** Returns bt_status_t
**
*******************************************************************************/
bt_status_t btif_enable_service(tBTA_SERVICE_ID service_id)
{
tBTA_SERVICE_ID *p_id = &service_id; /* If BT is enabled, we need to switch to BTIF context and trigger the
* enable for that profile
*
* Otherwise, we just set the flag. On BT_Enable, the DM will trigger
* enable for the profiles that have been enabled */ btif_enabled_services |= ( << service_id);//更新此全局变量 if (btif_is_enabled())
{
btif_transfer_context(btif_dm_execute_service_request,
BTIF_DM_ENABLE_SERVICE,
(char*)p_id, sizeof(tBTA_SERVICE_ID), NULL);
} return BT_STATUS_SUCCESS;
}
我们继续看btif_dm_execute_service_request：
void btif_dm_execute_service_request(UINT16 event, char *p_param)
{
BOOLEAN b_enable = FALSE;
bt_status_t status;
if (event == BTIF_DM_ENABLE_SERVICE)
{
b_enable = TRUE;
}
status = btif_in_execute_service_request(*((tBTA_SERVICE_ID*)p_param), b_enable);
if (status == BT_STATUS_SUCCESS)
{
bt_property_t property;
bt_uuid_t local_uuids[BT_MAX_NUM_UUIDS]; /* Now send the UUID_PROPERTY_CHANGED event to the upper layer */
BTIF_STORAGE_FILL_PROPERTY(&property, BT_PROPERTY_UUIDS,
sizeof(local_uuids), local_uuids);
btif_storage_get_adapter_property(&property);
HAL_CBACK(bt_hal_cbacks, adapter_properties_cb,
BT_STATUS_SUCCESS, , &property);//注意这里调用的是adapter_properties_cb，代表local的属性，不是remote devices的
}
return;
}
我们继续看btif_in_execute_service_request的实现：
bt_status_t btif_in_execute_service_request(tBTA_SERVICE_ID service_id,
BOOLEAN b_enable)
{
BTIF_TRACE_DEBUG("%s service_id: %d", __FUNCTION__, service_id);
/* Check the service_ID and invoke the profile's BT state changed API */
switch (service_id)
{
case BTA_HFP_SERVICE_ID:
case BTA_HSP_SERVICE_ID:
{
btif_hf_execute_service(b_enable);
}break;
case BTA_A2DP_SOURCE_SERVICE_ID:
{
btif_av_execute_service(b_enable);
}break;
我们继续看btif_av_execute_service：
/*******************************************************************************
**
** Function btif_av_execute_service
**
** Description Initializes/Shuts down the service
**
** Returns BT_STATUS_SUCCESS on success, BT_STATUS_FAIL otherwise
**
*******************************************************************************/
bt_status_t btif_av_execute_service(BOOLEAN b_enable)
{
if (b_enable)
{
/* TODO: Removed BTA_SEC_AUTHORIZE since the Java/App does not
* handle this request in order to allow incoming connections to succeed.
* We need to put this back once support for this is added */ /* Added BTA_AV_FEAT_NO_SCO_SSPD - this ensures that the BTA does not
* auto-suspend av streaming on AG events(SCO or Call). The suspend shall
* be initiated by the app/audioflinger layers */ BTA_AvEnable(BTA_SEC_AUTHENTICATE, BTA_AV_FEAT_RCTG|BTA_AV_FEAT_METADATA|BTA_AV_FEAT_VENDOR|BTA_AV_FEAT_NO_SCO_SSPD|BTA_AV_FEAT_RCCT|BTA_AV_FEAT_ADV_CTRL,bte_av_callback);//enable BTA_AvRegister(BTA_AV_CHNL_AUDIO, BTIF_AV_SERVICE_NAME, , bte_av_media_callback);//register
}
else {
BTA_AvDeregister(btif_av_cb.bta_handle);
BTA_AvDisable();
}
return BT_STATUS_SUCCESS;
}
上面的流程又可以分为两个部分：
- BTA_AvEnable
- BTA_AvRegister
我们下面分别来分析这两个部分：
BTA_AvEnable
void BTA_AvEnable(tBTA_SEC sec_mask, tBTA_AV_FEAT features, tBTA_AV_CBACK *p_cback)
{
tBTA_AV_API_ENABLE *p_buf; /* register with BTA system manager */
bta_sys_register(BTA_ID_AV, &bta_av_reg);//注册了BTA_ID_AV模块 if ((p_buf = (tBTA_AV_API_ENABLE *) GKI_getbuf(sizeof(tBTA_AV_API_ENABLE))) != NULL)
{
p_buf->hdr.event = BTA_AV_API_ENABLE_EVT;
p_buf->p_cback = p_cback;
p_buf->features = features;
p_buf->sec_mask = sec_mask;
bta_sys_sendmsg(p_buf);
}
}
这里依然是熟悉的 线程间通信，这里发出的第一个event 是BTA_AV_API_ENABLE_EVT，
AV nsm event=0x122b(API_ENABLE)
处理这个状态机的函数是bta_av_hdl_event，就是上面 刚刚注册到sys里面的：
看看其实现：
/*******************************************************************************
**
** Function bta_av_hdl_event
**
** Description Advanced audio/video main event handling function.
**
**
** Returns BOOLEAN
**
*******************************************************************************/
BOOLEAN bta_av_hdl_event(BT_HDR *p_msg)
{
UINT16 event = p_msg->event;
UINT16 first_event = BTA_AV_FIRST_NSM_EVT; if (event > BTA_AV_LAST_EVT)
{
return TRUE; /* to free p_msg */
} if(event >= first_event)//BTA_AV_FIRST_NSM_EVT,这里不会在状态机中处理
{
/* non state machine events */
(*bta_av_nsm_act[event - BTA_AV_FIRST_NSM_EVT]) ((tBTA_AV_DATA *) p_msg);
}
else if (event >= BTA_AV_FIRST_SM_EVT && event <= BTA_AV_LAST_SM_EVT)//handled by the AV main state machine
{
/* state machine events */
bta_av_sm_execute(&bta_av_cb, p_msg->event, (tBTA_AV_DATA *) p_msg);
}
else //这里处理by AV stream state machine
{
/* stream state machine events */
bta_av_ssm_execute( bta_av_hndl_to_scb(p_msg->layer_specific),
p_msg->event, (tBTA_AV_DATA *) p_msg);
}
return TRUE;
}
分析上面的bta_av_hdl_event 处理，发现其把event 分成了三类，
- 一种是在AV main state machine里面处理的，即调用bta_av_sm_execute 来处理
- 第二种是stream state machine 里面处理的，即调用bta_av_ssm_execute
- 第三种是不在状态机里面处理，即调用bta_av_nsm_act 里面的函数来处理
下面我们是各种情况对应的event：
bta_av_sm_execute处理如下的event：
/* these events are handled by the AV main state machine */
BTA_AV_API_DISABLE_EVT = BTA_SYS_EVT_START(BTA_ID_AV),//0x1200
BTA_AV_API_REMOTE_CMD_EVT,
BTA_AV_API_VENDOR_CMD_EVT,
BTA_AV_API_VENDOR_RSP_EVT,
BTA_AV_API_META_RSP_EVT,
BTA_AV_API_RC_CLOSE_EVT,
BTA_AV_AVRC_OPEN_EVT,
BTA_AV_AVRC_MSG_EVT,
BTA_AV_AVRC_NONE_EVT,//0x1208
bta_av_ssm_execute 处理如下的event：
/* these events are handled by the AV stream state machine */
BTA_AV_API_OPEN_EVT,//0x1209
BTA_AV_API_CLOSE_EVT,
BTA_AV_AP_START_EVT, //0x120b /* the following 2 events must be in the same order as the *API_*EVT */
BTA_AV_AP_STOP_EVT, /*其含义就是从API的相关的状态直接跳转到相应的状态机中执行*/
BTA_AV_API_RECONFIG_EVT,
BTA_AV_API_PROTECT_REQ_EVT,
BTA_AV_API_PROTECT_RSP_EVT,
BTA_AV_API_RC_OPEN_EVT,
BTA_AV_SRC_DATA_READY_EVT,
BTA_AV_CI_SETCONFIG_OK_EVT,
BTA_AV_CI_SETCONFIG_FAIL_EVT,
BTA_AV_SDP_DISC_OK_EVT,
BTA_AV_SDP_DISC_FAIL_EVT,
BTA_AV_STR_DISC_OK_EVT,
BTA_AV_STR_DISC_FAIL_EVT,
BTA_AV_STR_GETCAP_OK_EVT,
BTA_AV_STR_GETCAP_FAIL_EVT,
BTA_AV_STR_OPEN_OK_EVT,
BTA_AV_STR_OPEN_FAIL_EVT,
BTA_AV_STR_START_OK_EVT,
BTA_AV_STR_START_FAIL_EVT,
BTA_AV_STR_CLOSE_EVT,
BTA_AV_STR_CONFIG_IND_EVT,
BTA_AV_STR_SECURITY_IND_EVT,
BTA_AV_STR_SECURITY_CFM_EVT,
BTA_AV_STR_WRITE_CFM_EVT,
BTA_AV_STR_SUSPEND_CFM_EVT,
BTA_AV_STR_RECONFIG_CFM_EVT,
BTA_AV_AVRC_TIMER_EVT,
BTA_AV_AVDT_CONNECT_EVT,
BTA_AV_AVDT_DISCONNECT_EVT,
BTA_AV_ROLE_CHANGE_EVT,
BTA_AV_AVDT_DELAY_RPT_EVT,
BTA_AV_ACP_CONNECT_EVT,
bta_av_nsm_act 处理如下的event：
/* these events are handled outside of the state machine */
BTA_AV_API_ENABLE_EVT,
BTA_AV_API_REGISTER_EVT,
BTA_AV_API_DEREGISTER_EVT,
BTA_AV_API_DISCONNECT_EVT,
BTA_AV_CI_SRC_DATA_READY_EVT,
BTA_AV_SIG_CHG_EVT,
BTA_AV_SIG_TIMER_EVT,
BTA_AV_SDP_AVRC_DISC_EVT,
BTA_AV_AVRC_CLOSE_EVT,
BTA_AV_CONN_CHG_EVT,
BTA_AV_DEREG_COMP_EVT,
#if (BTA_AV_SINK_INCLUDED == TRUE)
BTA_AV_API_SINK_ENABLE_EVT,
#endif
#if (AVDT_REPORTING == TRUE)
BTA_AV_AVDT_RPT_CONN_EVT,
#endif
BTA_AV_API_START_EVT, //0x1238
下面我们继续看BTA_AV_API_ENABLE_EVT的处理情况：
/*******************************************************************************
**
** Function bta_av_api_enable
**
** Description Handle an API enable event.
**
**
** Returns void
**
*******************************************************************************/
static void bta_av_api_enable(tBTA_AV_DATA *p_data)
{
int i;
tBTA_AV_ENABLE enable; /* initialize control block */
memset(&bta_av_cb, , sizeof(tBTA_AV_CB));//bta_av_cb的生命线从此刻开始 for(i=; i<BTA_AV_NUM_RCB; i++)
bta_av_cb.rcb[i].handle = BTA_AV_RC_HANDLE_NONE;//rcb avrcp control block bta_av_cb.rc_acp_handle = BTA_AV_RC_HANDLE_NONE; /* store parameters */
bta_av_cb.p_cback = p_data->api_enable.p_cback;//bte_av_callback
bta_av_cb.features = p_data->api_enable.features;
bta_av_cb.sec_mask = p_data->api_enable.sec_mask; enable.features = bta_av_cb.features; /* Register for SCO change event */
if (!(bta_av_cb.features & BTA_AV_FEAT_NO_SCO_SSPD))
{
bta_sys_sco_register(bta_av_sco_chg_cback);
} /* call callback with enable event */
(*bta_av_cb.p_cback)(BTA_AV_ENABLE_EVT, (tBTA_AV *)&enable);//调用回调，预示av enable 完成
}
回调函数处理的流程是 找对对应状态的handler 来处理event，当前的btif_av状态是idle对于BTA_AV_ENABLE_EVT 没有处理，这里就不分析了。
下面我们看看
BTA_AvRegister
/*******************************************************************************
**
** Function BTA_AvRegister
**
** Description Register the audio or video service to stack. When the
** operation is complete the callback function will be
** called with a BTA_AV_REGISTER_EVT. This function must
** be called before AVDT stream is open.
**
**
** Returns void
**
*******************************************************************************/
void BTA_AvRegister(tBTA_AV_CHNL chnl, const char *p_service_name, UINT8 app_id, tBTA_AV_DATA_CBACK *p_data_cback)
{
tBTA_AV_API_REG *p_buf; if ((p_buf = (tBTA_AV_API_REG *) GKI_getbuf(sizeof(tBTA_AV_API_REG))) != NULL)
{
p_buf->hdr.layer_specific = chnl;
p_buf->hdr.event = BTA_AV_API_REGISTER_EVT;
if(p_service_name)
{
BCM_STRNCPY_S(p_buf->p_service_name, sizeof(p_buf->p_service_name), p_service_name, BTA_SERVICE_NAME_LEN);
p_buf->p_service_name[BTA_SERVICE_NAME_LEN-] = ;//保存名字
}
else
{
p_buf->p_service_name[] = ;
}
p_buf->app_id = app_id;
p_buf->p_app_data_cback = p_data_cback;//保存callback
bta_sys_sendmsg(p_buf);
}
}
这里还是熟悉的线程间通信，由上面的分析得知，这个事件是由bta_av_nsm_act 来处理：
我们看看具体的实现，这个函数非常的长，里面主要涉及 结构的初始化，以及将结构注册到AVDTP,
/*******************************************************************************
**
** Function bta_av_api_register
**
** Description allocate stream control block,
** register the service to stack
** create SDP record
**
** Returns void
**
*******************************************************************************/
static void bta_av_api_register(tBTA_AV_DATA *p_data)
{
tBTA_AV_REGISTER registr;
tBTA_AV_SCB *p_scb; /* stream control block */
tAVDT_REG reg;
tAVDT_CS cs;
char *p_service_name;
tBTA_AV_CODEC codec_type;
tBTA_UTL_COD cod;
UINT8 index = ;
char p_avk_service_name[BTA_SERVICE_NAME_LEN+];
BCM_STRNCPY_S(p_avk_service_name, sizeof(p_avk_service_name), BTIF_AVK_SERVICE_NAME, BTA_SERVICE_NAME_LEN);//sink service name memset(&cs,,sizeof(tAVDT_CS));//初始化cs，该项最终拷贝到p_scb->cfg，并且AVDT_CreateStream 会使用到 registr.status = BTA_AV_FAIL_RESOURCES;//register 记录注册的信息，回调的时候会上报
registr.app_id = p_data->api_reg.app_id;//
registr.chnl = (tBTA_AV_CHNL)p_data->hdr.layer_specific;//audio 0x40
do //do...while(0)结构
{
p_scb = bta_av_alloc_scb(registr.chnl);//分配了一个 stream control block ：bta_av_cb.p_scb[xx] = p_scb registr.hndl = p_scb->hndl;//0x41 or 0x42 --- hndl = (tBTA_AV_HNDL)((xx + 1) | chnl);
p_scb->app_id = registr.app_id;// /* initialize the stream control block */
p_scb->timer.p_cback = (TIMER_CBACK*)&bta_av_timer_cback;
registr.status = BTA_AV_SUCCESS; if((bta_av_cb.reg_audio + bta_av_cb.reg_video) == )//开始没有注册等于0
{
/* the first channel registered. register to AVDTP */
reg.ctrl_mtu = p_bta_av_cfg->sig_mtu;
reg.ret_tout = BTA_AV_RET_TOUT;
reg.sig_tout = BTA_AV_SIG_TOUT;
reg.idle_tout = BTA_AV_IDLE_TOUT;
reg.sec_mask = bta_av_cb.sec_mask;
#if( defined BTA_AR_INCLUDED ) && (BTA_AR_INCLUDED == TRUE)
bta_ar_reg_avdt(®, bta_av_conn_cback, BTA_ID_AV);//AR module registration to AVDT.
#endif
bta_sys_role_chg_register(&bta_av_sys_rs_cback); /* create remote control TG service if required */
if (bta_av_cb.features & (BTA_AV_FEAT_RCTG))
{
/* register with no authorization; let AVDTP use authorization instead */
#if( defined BTA_AR_INCLUDED ) && (BTA_AR_INCLUDED == TRUE)
bta_ar_reg_avct(p_bta_av_cfg->avrc_mtu, p_bta_av_cfg->avrc_br_mtu,
(UINT8)(bta_av_cb.sec_mask & (~BTA_SEC_AUTHORIZE)), BTA_ID_AV);//注册到AVCT
#endif bta_ar_reg_avrc(UUID_SERVCLASS_AV_REM_CTRL_TARGET, "AV Remote Control Target", NULL,
p_bta_av_cfg->avrc_tg_cat, BTA_ID_AV);//给AVRCP注册一个sdp record
#endif
} /* Set the Capturing service class bit */ cod.service = BTM_COD_SERVICE_CAPTURING;
utl_set_device_class(&cod, BTA_UTL_SET_COD_SERVICE_CLASS);
} /* if 1st channel */ /* get stream configuration and create stream */
/* memset(&cs.cfg,0,sizeof(tAVDT_CFG)); */
cs.cfg.num_codec = ;
cs.tsep = AVDT_TSEP_SRC;//src端 /*
* memset of cs takes care setting call back pointers to null.
cs.p_data_cback = NULL;
cs.p_report_cback = NULL;
*/
cs.nsc_mask = AVDT_NSC_RECONFIG |
((bta_av_cb.features & BTA_AV_FEAT_PROTECT) ? : AVDT_NSC_SECURITY);
APPL_TRACE_DEBUG("nsc_mask: 0x%x", cs.nsc_mask); p_service_name = p_data->api_reg.p_service_name; p_scb->suspend_sup = TRUE;
p_scb->recfg_sup = TRUE; cs.p_ctrl_cback = bta_av_dt_cback[p_scb->hdi];//根据不同的index 会调用不同bta_av_streamX_cback
if(registr.chnl == BTA_AV_CHNL_AUDIO)
{
/* set up the audio stream control block */
p_scb->p_act_tbl = (const tBTA_AV_ACT *)bta_av_a2d_action;//保存action table
p_scb->p_cos = &bta_av_a2d_cos;
p_scb->media_type= AVDT_MEDIA_AUDIO;
cs.cfg.psc_mask = AVDT_PSC_TRANS;
cs.media_type = AVDT_MEDIA_AUDIO;
cs.mtu = p_bta_av_cfg->audio_mtu;
cs.flush_to = L2CAP_DEFAULT_FLUSH_TO; ...
/* keep the configuration in the stream control block */
memcpy(&p_scb->cfg, &cs.cfg, sizeof(tAVDT_CFG));
while(index < BTA_AV_MAX_SEPS &&
(*bta_av_a2d_cos.init)(&codec_type, cs.cfg.codec_info,
&cs.cfg.num_protect, cs.cfg.protect_info, index) == TRUE)//bta_av_co_audio_init to to initialize audio paths
{ if(AVDT_CreateStream(&p_scb->seps[index].av_handle, &cs) == AVDT_SUCCESS)//Create a stream endpoint.
{
p_scb->seps[index].codec_type = codec_type;
index++;
}
} if(!bta_av_cb.reg_audio)//为profile 创建相关的sdp record
{
/* create the SDP records on the 1st audio channel */
bta_av_cb.sdp_a2d_handle = SDP_CreateRecord();
A2D_AddRecord(UUID_SERVCLASS_AUDIO_SOURCE, p_service_name, NULL,
A2D_SUPF_PLAYER, bta_av_cb.sdp_a2d_handle);
bta_sys_add_uuid(UUID_SERVCLASS_AUDIO_SOURCE); /* start listening when A2DP is registered */
if (bta_av_cb.features & BTA_AV_FEAT_RCTG)
bta_av_rc_create(&bta_av_cb, AVCT_ACP, , BTA_AV_NUM_LINKS + ); /* if the AV and AVK are both supported, it cannot support the CT role */
if (bta_av_cb.features & (BTA_AV_FEAT_RCCT))
{
...
#if( defined BTA_AR_INCLUDED ) && (BTA_AR_INCLUDED == TRUE)
/* create an SDP record as AVRC CT. */
bta_ar_reg_avrc(UUID_SERVCLASS_AV_REMOTE_CONTROL, NULL, NULL,
p_bta_av_cfg->avrc_ct_cat, BTA_ID_AV);
#endif
}
}
bta_av_cb.reg_audio |= BTA_AV_HNDL_TO_MSK(p_scb->hdi);
APPL_TRACE_DEBUG("reg_audio: 0x%x",bta_av_cb.reg_audio);
}
else
{
/*vedio*/
}
} while (); /* call callback with register event */
(*bta_av_cb.p_cback)(BTA_AV_REGISTER_EVT, (tBTA_AV *)®istr);//btif_av_cb.bta_handle = ((tBTA_AV*)p_data)->registr.hndl
}
上面代码的大部分已经 谢了注解，这里解释一下两点：
- bta_av_a2d_cos.init
- AVDT_CreateStream
- 关于AVDTP的注册bta_ar_reg_avdt(®, bta_av_conn_cback, BTA_ID_AV) （其实这个应该算第一点，因为只是一些注册性的内容，所以最后讲）
我们先看一下bta_av_a2d_cos.init的实现：
/*******************************************************************************
**
** Function bta_av_co_audio_init
**
** Description This callout function is executed by AV when it is
** started by calling BTA_AvRegister(). This function can be
** used by the phone to initialize audio paths or for other
** initialization purposes.
**
**
** Returns Stream codec and content protection capabilities info.
**
*******************************************************************************/
BOOLEAN bta_av_co_audio_init(UINT8 *p_codec_type, UINT8 *p_codec_info, UINT8 *p_num_protect,
UINT8 *p_protect_info, UINT8 index)
{
FUNC_TRACE(); APPL_TRACE_DEBUG("bta_av_co_audio_init: %d", index); /* By default - no content protection info */
*p_num_protect = ;
*p_protect_info = ; /* reset remote preference through setconfig */
bta_av_co_cb.codec_cfg_setconfig.id = BTIF_AV_CODEC_NONE; switch (index)
{
case BTIF_SV_AV_AA_SBC_INDEX: /* Set up for SBC codec for SRC*/
*p_codec_type = BTA_AV_CODEC_SBC; /* This should not fail because we are using constants for parameters */
A2D_BldSbcInfo(AVDT_MEDIA_AUDIO, (tA2D_SBC_CIE *) &bta_av_co_sbc_caps, p_codec_info);//初始化和audio相关的参数 /* Codec is valid */
return TRUE;
...
default:
/* Not valid */
return FALSE;
}
}
我们再看一下AVDT_CreateStream 的行为：
/*******************************************************************************
**
** Function AVDT_CreateStream
**
** Description Create a stream endpoint. After a stream endpoint is
** created an application can initiate a connection between
** this endpoint and an endpoint on a peer device. In
** addition, a peer device can discover, get the capabilities,
** and connect to this endpoint.
**
**
** Returns AVDT_SUCCESS if successful, otherwise error.
**
*******************************************************************************/
UINT16 AVDT_CreateStream(UINT8 *p_handle, tAVDT_CS *p_cs)
{
UINT16 result = AVDT_SUCCESS;
tAVDT_SCB *p_scb; /* Verify parameters; if invalid, return failure */
if (((p_cs->cfg.psc_mask & (~AVDT_PSC)) != ) || (p_cs->p_ctrl_cback == NULL))
{
result = AVDT_BAD_PARAMS;
}
/* Allocate scb; if no scbs, return failure */
else if ((p_scb = avdt_scb_alloc(p_cs)) == NULL)//分配avdt_cb.scb里面的节点
{
result = AVDT_NO_RESOURCES;
}
else
{
*p_handle = avdt_scb_to_hdl(p_scb);//分配的节点在avdt_cb.scb里面的位置+1 是handle的值-->p_scb->seps[index].av_handle
}
return result;
}
发现这个AVDT_CreateStream，本质上就是在AVDTP层创建stream control block 节点，并把这个节点用一个handle和bta_av_cb.p_scb 里面的节点 相关联。
最后我们来简单看一下
关于AVDTP的注册bta_ar_reg_avdt(®, bta_av_conn_cback, BTA_ID_AV)
这里无非就是一些注册性质的行为，我们简单分析一下：
/*******************************************************************************
**
** Function bta_ar_reg_avdt
**
** Description AR module registration to AVDT.
**
** Returns void
**
*******************************************************************************/
void bta_ar_reg_avdt(tAVDT_REG *p_reg, tAVDT_CTRL_CBACK *p_cback, tBTA_SYS_ID sys_id)
{
UINT8 mask = ; if (sys_id == BTA_ID_AV)
{
bta_ar_cb.p_av_conn_cback = p_cback;//保存回调bta_av_conn_cback，其作用暂时不管
mask = BTA_AR_AV_MASK;
}
else if (sys_id == BTA_ID_AVK)
{
bta_ar_cb.p_avk_conn_cback = p_cback;
mask = BTA_AR_AVK_MASK;
} if (mask)
{
if (bta_ar_cb.avdt_registered == )
{
AVDT_Register(p_reg, bta_ar_avdt_cback);//注册AVDTP
}
bta_ar_cb.avdt_registered |= mask;
}
}
我们继续分析 AVDTP_Register，
/*******************************************************************************
**
** Function AVDT_Register
**
** Description This is the system level registration function for the
** AVDTP protocol. This function initializes AVDTP and
** prepares the protocol stack for its use. This function
** must be called once by the system or platform using AVDTP
** before the other functions of the API an be used.
**
**
** Returns void
**
*******************************************************************************/
void AVDT_Register(tAVDT_REG *p_reg, tAVDT_CTRL_CBACK *p_cback)
{
/* register PSM with L2CAP */
L2CA_Register(AVDT_PSM, (tL2CAP_APPL_INFO *) &avdt_l2c_appl); /* set security level */
BTM_SetSecurityLevel(TRUE, "", BTM_SEC_SERVICE_AVDTP, p_reg->sec_mask,
AVDT_PSM, BTM_SEC_PROTO_AVDT, AVDT_CHAN_SIG);
BTM_SetSecurityLevel(FALSE, "", BTM_SEC_SERVICE_AVDTP, p_reg->sec_mask,
AVDT_PSM, BTM_SEC_PROTO_AVDT, AVDT_CHAN_SIG); /* do not use security on the media channel */
BTM_SetSecurityLevel(TRUE, "", BTM_SEC_SERVICE_AVDTP_NOSEC, BTM_SEC_NONE,
AVDT_PSM, BTM_SEC_PROTO_AVDT, AVDT_CHAN_MEDIA);
BTM_SetSecurityLevel(FALSE, "", BTM_SEC_SERVICE_AVDTP_NOSEC, BTM_SEC_NONE,
AVDT_PSM, BTM_SEC_PROTO_AVDT, AVDT_CHAN_MEDIA); #if AVDT_REPORTING == TRUE
/* do not use security on the reporting channel */
BTM_SetSecurityLevel(TRUE, "", BTM_SEC_SERVICE_AVDTP_NOSEC, BTM_SEC_NONE,
AVDT_PSM, BTM_SEC_PROTO_AVDT, AVDT_CHAN_REPORT);
BTM_SetSecurityLevel(FALSE, "", BTM_SEC_SERVICE_AVDTP_NOSEC, BTM_SEC_NONE,
AVDT_PSM, BTM_SEC_PROTO_AVDT, AVDT_CHAN_REPORT);
#endif /* initialize AVDTP data structures */
avdt_scb_init();
avdt_ccb_init();
avdt_ad_init(); /* copy registration struct */
memcpy(&avdt_cb.rcb, p_reg, sizeof(tAVDT_REG));//保存reg信息到avdt_cb.rcb里面
avdt_cb.p_conn_cback = p_cback;//保存回调bta_ar_avdt_cback，发现这个函数的实现就是调用bta_ar_cb.p_av_conn_cback
}
下面我们分析一下，上面的初始化AVDTP 数据结构的三个函数，我们先看看avdt_scb_init，从名字上面看，应该是初始化stream control block，
/*******************************************************************************
**
** Function avdt_scb_init
**
** Description Initialize stream control block module.
**
**
** Returns Nothing.
**
*******************************************************************************/
void avdt_scb_init(void)
{
memset(&avdt_cb.scb[], , sizeof(tAVDT_SCB) * AVDT_NUM_SEPS);
avdt_cb.p_scb_act = (tAVDT_SCB_ACTION *) avdt_scb_action;//保存action，这个是为了之后状态机中执行
}
继续看avdt_ccb_init， 从名字上面看，应该是初始化channel control block，
/*******************************************************************************
**
** Function avdt_ccb_init
**
** Description Initialize channel control block module.
**
**
** Returns Nothing.
**
*******************************************************************************/
void avdt_ccb_init(void)
{
memset(&avdt_cb.ccb[], , sizeof(tAVDT_CCB) * AVDT_NUM_LINKS);
avdt_cb.p_ccb_act = (tAVDT_CCB_ACTION *) avdt_ccb_action;//为了后续在channel 状态机中执行action 使用
}
最后，我们看看avdt_ad_init的实现：Initialize adaption layer
/*******************************************************************************
**
** Function avdt_ad_init
**
** Description Initialize adaption layer.
**
**
** Returns Nothing.
**
*******************************************************************************/
void avdt_ad_init(void)
{
int i;
tAVDT_TC_TBL *p_tbl = avdt_cb.ad.tc_tbl;
memset(&avdt_cb.ad, , sizeof(tAVDT_AD)); /* make sure the peer_mtu is a valid value */
for (i = ; i < AVDT_NUM_TC_TBL; i++, p_tbl++)
{
p_tbl->peer_mtu = L2CAP_DEFAULT_MTU;
}
}
关于a2dp的JNI以下的初始化的过程,这里补了一张图片:
好了，关于BTA_AvRegister 就讲到这里，a2dp的初始化的工作也已经完成了。
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