SensorService启动

SensorService启动_第1张图片

SystemServer进程启动SensorService

系统启动system_server进程，SystemServer.java 负责启动 startSensorService()
frameworks/base/services/java/com/android/server/SystemServer.java

system_server进程启动 new SystemServer().run()

    private void run() {        // ... ...        // Start services.        try {            traceBeginAndSlog("StartServices");            startBootstrapServices();            startCoreServices();            startOtherServices();            SystemServerInitThreadPool.shutdown();        } catch (Throwable ex) {            Slog.e("System", "******************************************");            Slog.e("System", "************ Failure starting system services", ex);            throw ex;        } finally {            traceEnd();        }        // ... ...    }

在引导服务 startBootstrapServices 中启动 startSensorService()

    /**     * Start the sensor service. This is a blocking call and can take time.     */    private static native void startSensorService();    // ... ...    private void startBootstrapServices() {        // ... ...        traceBeginAndSlog("StartSensorPrivacyService");        mSystemServiceManager.startService(new SensorPrivacyService(mSystemContext));        traceEnd();        if (SystemProperties.getInt("persist.sys.displayinset.top", 0) > 0) {            // DisplayManager needs the overlay immediately.            mActivityManagerService.updateSystemUiContext();            LocalServices.getService(DisplayManagerInternal.class).onOverlayChanged();        }        // The sensor service needs access to package manager service, app ops        // service, and permissions service, therefore we start it after them.        // Start sensor service in a separate thread. Completion should be checked        // before using it.        mSensorServiceStart = SystemServerInitThreadPool.get().submit(() -> {            TimingsTraceLog traceLog = new TimingsTraceLog(                    SYSTEM_SERVER_TIMING_ASYNC_TAG, Trace.TRACE_TAG_SYSTEM_SERVER);            traceLog.traceBegin(START_SENSOR_SERVICE);            startSensorService();            traceLog.traceEnd();        }, START_SENSOR_SERVICE);    }

1、SensorService 需要访问 PKMS服务，AppOpsService服务和PermissionsService服务，因此在它们之后启动SensorService。
2、SystemServerInitThreadPool在单独的线程中启动传感器服务
3、native 调用 startSensorService()

native 调用 startSensorService()

frameworks/base/services/core/jni/com_android_server_SystemServer.cpp

SensorService::publish 启动

static void android_server_SystemServer_startSensorService(JNIEnv* /* env */, jobject /* clazz */) {    char propBuf[PROPERTY_VALUE_MAX];    property_get("system_init.startsensorservice", propBuf, "1");    if (strcmp(propBuf, "1") == 0) {        SensorService::publish(false /* allowIsolated */,                               IServiceManager::DUMP_FLAG_PRIORITY_CRITICAL);    }}

SensorService 实例创建

SensorService继承

frameworks/native/services/sensorservice/SensorService.h

继承BinderService、BnSensorServer、Thread

class SensorService :        public BinderService<SensorService>,        public BnSensorServer,        protected Thread

1、BinderService：frameworks/native/libs/binder/include/binder/BinderService.h
BinderService 是 Android Service 框架的主要类，是个模板类，它提供了 Service 的生命周期管理、进程间通信、请求响应处理等功能。Android 中的绝大部分 Service 都会继承此类。
new SERVICE()：new一个SensorService，然后以 “sensorservice”为key，把sensorservice实例加入到ServiceManaer
2、BnSensorServer：frameworks/native/libs/sensor/include/sensor/ISensorServer.h
和 BinderService 主要实现IPC跨进程通信，实际继承BnInterface: frameworks/native/libs/binder/include/binder/IInterface.h
3、Thread：继承 Thread 启动 threadLoop

SensorService 创建 onFirstRef

当 SensorService 第一个实例创建时，其 onFirstRef 接口将会被调用

① 在 SensorDevice 的构造函数中，会调用 hw_get_module 接口加载 Sensor HAL 的动态库
② 通过 SensorDevice，调用 Sensor HAL 提供的 get_sensors_list 接口，获取所支持的 Sensor 信息获，调用registerSensor函数把Sensor保存起来
③ SensorFusion功能，传感融合。它的主要作用就是，按照一定的算法计算系统的多个传感器对某一个值的上报的数据，得到更准确的值。
④ registerVirtualSensor注册虚拟传感器：这些虚拟的传感器步会产生真的数据，而是通过SensorFusion功能计算得到的值，作为虚拟传感的数据。分发过程中会有分析到。
⑤ 初始化一些Buffer，用他们保存sensor硬件上报的数据
⑥ 创建一个 Looper 和 SensorEventAckReceiver。其中 Looper 用于 enable sensor 后，进行数据的接收；而 SensorEventAckReceiver 则用于在 dispatch wake up sensor event 给上层后，接收上层返回的确认 ACK。
⑦ SensorService 不仅是一个服务，而且他还是一个线程，初始化工作的最后就是启动该线程执行threadLoop函数。threadLoop函数主要的工作就是，循环读取sensor硬件上传上来的数据，然后分发给应用。

void SensorService::onFirstRef() {// ① 在 SensorDevice 的构造函数中，会调用 hw_get_module 接口加载 Sensor HAL 的动态库    SensorDevice& dev(SensorDevice::getInstance());    //.......    if (dev.initCheck() == NO_ERROR) {// ② 通过 SensorDevice，调用 Sensor HAL 提供的 get_sensors_list 接口，获取所支持的 Sensor 信息获，调用registerSensor函数把Sensor保存起来        sensor_t const* list;        ssize_t count = dev.getSensorList(&list);        //.......            for (ssize_t i=0 ; i<count ; i++) {            //.......                if (useThisSensor) {                    registerSensor( new HardwareSensor(list[i]) );                }            }// ③ SensorFusion功能，传感融合。它的主要作用就是，按照一定的算法计算系统的多个传感器对某一个值的上报的数据，得到更准确的值。            // it's safe to instantiate the SensorFusion object here            // (it wants to be instantiated after h/w sensors have been            // registered)            SensorFusion::getInstance();// ④ 注册虚拟传感器：这些虚拟的传感器步会产生真的数据，而是通过SensorFusion功能计算得到的值，作为虚拟传感的数据。           //.......                registerSensor(new RotationVectorSensor(), !needRotationVector, true);                registerSensor(new OrientationSensor(), !needRotationVector, true);                registerSensor(new LinearAccelerationSensor(list, count),                               !needLinearAcceleration, true);                registerSensor( new CorrectedGyroSensor(list, count), true, true);                registerSensor( new GyroDriftSensor(), true, true);           //.......                registerSensor(new GravitySensor(list, count), !needGravitySensor, true);           //.......                registerSensor(new GameRotationVectorSensor(), !needGameRotationVector, true);           //.......                registerSensor(new GeoMagRotationVectorSensor(), !needGeoMagRotationVector, true);            //.......// ⑤ 初始化一些Buffer，用他们保存sensor硬件上报的数据            mLooper = new Looper(false);            const size_t minBufferSize = SensorEventQueue::MAX_RECEIVE_BUFFER_EVENT_COUNT;            mSensorEventBuffer = new sensors_event_t[minBufferSize];            mSensorEventScratch = new sensors_event_t[minBufferSize];            mMapFlushEventsToConnections = new wp<const SensorEventConnection> [minBufferSize];            mCurrentOperatingMode = NORMAL;            //.......// ⑥ 创建一个 Looper 和 SensorEventAckReceiver。其中 Looper 用于 enable sensor 后，进行数据的接收；而 SensorEventAckReceiver 则用于在 dispatch wake up sensor event 给上层后，接收上层返回的确认 ACK。            mAckReceiver = new SensorEventAckReceiver(this);            mAckReceiver->run("SensorEventAckReceiver", PRIORITY_URGENT_DISPLAY);// ⑦ SensorService 不仅是一个服务，而且他还是一个线程，初始化工作的最后就是启动该线程执行threadLoop函数。threadLoop函数主要的工作就是，循环读取sensor硬件上传上来的数据，然后分发给应用。            run("SensorService", PRIORITY_URGENT_DISPLAY);             //.......}

SensorService::threadLoop()

1、通过poll往hal层取sensor数据，若没有数据的时候就一直阻塞（该阻塞功能由HAL层实现），当有数据时该函数就会返回
2、virtual sensors 相关数据计算后上报
3、通过SensorEventConnection中 sendEvents 将数据给到每个应用，每个应用都有自己的SensorEventConnection

bool SensorService::threadLoop() {    ALOGD("nuSensorService thread starting...");    //.......    SensorDevice& device(SensorDevice::getInstance());    const int halVersion = device.getHalDeviceVersion();    do {        // ① 通过poll往hal层取sensor数据， 若没有数据的时候就一直阻塞（该阻塞功能由HAL层实现），当有数据时该函数就会返回        ssize_t count = device.poll(mSensorEventBuffer, numEventMax);//①        if (count < 0) {            if(count == DEAD_OBJECT && device.isReconnecting()) {                device.reconnect();                continue;            } else {                ALOGE("sensor poll failed (%s)", strerror(-count));                break;            }        }        //.......        // handle virtual sensors        if (count && vcount) {            sensors_event_t const * const event = mSensorEventBuffer;            if (!mActiveVirtualSensors.empty()) {                size_t k = 0;                SensorFusion& fusion(SensorFusion::getInstance());                if (fusion.isEnabled()) {                    for (size_t i=0 ; i<size_t(count) ; i++) {                        fusion.process(event[i]);                    }                }                for (size_t i=0 ; i<size_t(count) && k<minBufferSize ; i++) {                    for (int handle : mActiveVirtualSensors) {                        if (count + k >= minBufferSize) {                            ALOGE("buffer too small to hold all events: "                                    "count=%zd, k=%zu, size=%zu",                                    count, k, minBufferSize);                            break;                        }                        sensors_event_t out;                        sp<SensorInterface> si = mSensors.getInterface(handle);                        if (si == nullptr) {                            ALOGE("handle %d is not an valid virtual sensor", handle);                            continue;                        }                        // ② virtual sensors 相关数据计算后上报                        if (si->process(&out, event[i])) {                            mSensorEventBuffer[count + k] = out;                            k++;                        }                    }                }                if (k) {                    // record the last synthesized values                    recordLastValueLocked(&mSensorEventBuffer[count], k);                    count += k;                    // sort the buffer by time-stamps                    sortEventBuffer(mSensorEventBuffer, count);                }            }        }        //.......        // Send our events to clients. Check the state of wake lock for each client and release the        // lock if none of the clients need it.        bool needsWakeLock = false;        for (const sp<SensorEventConnection>& connection : activeConnections) {            // ② 通过SensorEventConnection 将数据给到每个应用，每个应用都有自己的SensorEventConnection            connection->sendEvents(mSensorEventBuffer, count, mSensorEventScratch,                    mMapFlushEventsToConnections); //②            needsWakeLock |= connection->needsWakeLock();            // If the connection has one-shot sensors, it may be cleaned up after first trigger.            // Early check for one-shot sensors.            if (connection->hasOneShotSensors()) {                cleanupAutoDisabledSensorLocked(connection, mSensorEventBuffer, count);            }        }        if (mWakeLockAcquired && !needsWakeLock) {            setWakeLockAcquiredLocked(false);        }    } while (!Thread::exitPending());    ALOGW("Exiting SensorService::threadLoop => aborting...");    abort();    return false;}

时序图

SensorService启动_第2张图片

SensorService启动

SensorService启动

SystemServer进程启动SensorService

native 调用 startSensorService()

SensorService 实例创建

SensorService继承

SensorService 创建 onFirstRef

SensorService::threadLoop()

时序图

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