android sensor framework

1. 简介

    在了解Sensor工作流程以前,一直以为其事件是通过Event Hub来进行输送的,可是研究完Android4.0代码之后,才发现自己错了。

    其主要框架如下图所示:

 

android sensor framework_第1张图片

2.功能模块

2.1 SensorManager.java

与下层接口功能:
1) 在SensorManager函数中
   (1) 调用native sensors_module_init初始化sensor list,即实例化native中的SensorManager

   (2) 创建SensorThread线程

2) 在类SensorThread中
   (1) 调用native sensors_create_queue创建队列
   (2) 在线程中dead loop地调用native sensors_data_poll以从队列sQueue中获取事件(float[] values = new float[3];)
   (3) 收到事件之后,报告sensor event给所有注册且关心此事件的listener

 

与上层的接口功能:

1) 在onPause时取消listener注册

2) 在onResume时注册listener

3) 把收到的事件报告给注册的listener

2.2 android_hardware_SensorManager.cpp

      实现SensorManager.java中的native函数,它主要调用SenrsorManager.cpp和SensorEventQueue.cpp中的类来完成相关的工作。

2.3 SensorManager.cpp

[cpp] view plain copy print ?
  1. class SensorManager :  
  2.     public ASensorManager,  
  3.     public Singleton  
  4. {  
  5. public:  
  6.     SensorManager(); //调用assertStateLocked   
  7.     ~SensorManager();  
  8.     //调用assertStateLocked,并返回mSensorList   
  9.     ssize_t getSensorList(Sensor constconst** list) const;  
  10.   
  11.     // 返回mSensorList中第一个类型与type一致的sensor       
  12.     Sensor const* getDefaultSensor(int type);  
  13.   
  14.     // 调用mSensorServer->createSensorEventConnection创建一个连接(ISensorEventConnection)   
  15.     // 并用此连接做为参数创建一个SensorEventQueue对象并返回   
  16.     sp createEventQueue();  
  17.   
  18. private:  
  19.     // DeathRecipient interface   
  20.     void sensorManagerDied();  
  21.     // 调用getService获取SensorService客户端并保存在mSensorServer中   
  22.     // 调用mSensorServer->getSensorList获取sensor列表,并保存在mSensors和mSensorList中   
  23.     status_t assertStateLocked() const;  
  24.   
  25. private:  
  26.     mutable Mutex mLock;  
  27.     mutable sp mSensorServer; // SensorService客户端   
  28.     mutable Sensor const** mSensorList; // sensor列表   
  29.     mutable Vector mSensors;    // sensor列表   
  30.     mutable sp mDeathObserver;  
  31. }  
class SensorManager :
    public ASensorManager,
    public Singleton
{
public:
    SensorManager(); //调用assertStateLocked
    ~SensorManager();
    //调用assertStateLocked,并返回mSensorList
    ssize_t getSensorList(Sensor const* const** list) const;

    // 返回mSensorList中第一个类型与type一致的sensor	
    Sensor const* getDefaultSensor(int type);

    // 调用mSensorServer->createSensorEventConnection创建一个连接(ISensorEventConnection)
    // 并用此连接做为参数创建一个SensorEventQueue对象并返回
    sp createEventQueue();

private:
    // DeathRecipient interface
    void sensorManagerDied();
    // 调用getService获取SensorService客户端并保存在mSensorServer中
    // 调用mSensorServer->getSensorList获取sensor列表,并保存在mSensors和mSensorList中
    status_t assertStateLocked() const;

private:
    mutable Mutex mLock;
    mutable sp mSensorServer; // SensorService客户端
    mutable Sensor const** mSensorList; // sensor列表
    mutable Vector mSensors;    // sensor列表
    mutable sp mDeathObserver;
}

 

[cpp] view plain copy print ?
  1. class ISensorEventConnection : public IInterface  
  2. {  
  3. public:  
  4.     DECLARE_META_INTERFACE(SensorEventConnection);  
  5.   
  6.     virtual sp getSensorChannel() const = 0;  
  7.     virtual status_t enableDisable(int handle, bool enabled) = 0;  
  8.     virtual status_t setEventRate(int handle, nsecs_t ns) = 0;  
  9. };  
class ISensorEventConnection : public IInterface
{
public:
    DECLARE_META_INTERFACE(SensorEventConnection);

    virtual sp getSensorChannel() const = 0;
    virtual status_t enableDisable(int handle, bool enabled) = 0;
    virtual status_t setEventRate(int handle, nsecs_t ns) = 0;
};

2.4 SensorService.cpp

       SensorService作为一个轻量级的system service,它运行于SystemServer内,即在system_init调用SensorService::instantiate();

      SensorService主要功能如下:
          1) SensorService::instantiate创建实例对象,并增加到ServiceManager中,且创建并启动线程,并执行threadLoop
          2) threadLoop从sensor驱动获取原始数据,然后通过SensorEventConnection把事件发送给客户端
          3) BnSensorServer的成员函数负责让客户端获取sensor列表和创建SensorEventConnection

      SensorService与客户端的接口定义如下:

[cpp] view plain copy print ?
  1. class ISensorServer : public IInterface  
  2. {  
  3. public:  
  4.     DECLARE_META_INTERFACE(SensorServer);  
  5.   
  6.     virtual Vector getSensorList() = 0;  
  7.     virtual sp createSensorEventConnection() = 0;  
  8. };  
class ISensorServer : public IInterface
{
public:
    DECLARE_META_INTERFACE(SensorServer);

    virtual Vector getSensorList() = 0;
    virtual sp createSensorEventConnection() = 0;
};

    SensorService定义如下:

[cpp] view plain copy print ?
  1. class SensorService :  
  2.         public BinderService//创建SensorService对象,并增加到ServiceManager中   
  3.         public BnSensorServer, // 申明了SensorService与客户端(SensorManager)间的binder接口   
  4.         protected Thread // 线程辅助类,调用run创建并启动线程,然后在线程主函数内回调threadLoop函数,   
  5.                          // 所以在使用它时,做一个派生,并根据需要重写threadLoop即可   
  6.                       
  7. {  
  8.    friend class BinderService;  
  9.   
  10.    static const nsecs_t MINIMUM_EVENTS_PERIOD =   1000000; // 1000 Hz   
  11.   
  12.             SensorService();  
  13.     virtual ~SensorService();  
  14.      
  15.     /* 
  16.     在addService时,第一次构建sp强引用对象时,会调用onFirstRef函数 
  17.      实现功能如下: 
  18.      1) 获取SensorDevice实例 
  19.      2) 调用SensorDevice.getSensorList获取sensor_t列表 
  20.      3) 根据硬件sensor_t创建HardwareSensor,然后加入mSensorList(Sensor) 
  21.             和mSensorMap(HardwareSensor)中 
  22.      4) 根据硬件sensor_t创建对应的senosr(如GravitySensor), 
  23.             然后加入mVirtualSensorList和mSensorList中 
  24.      5) mUserSensorList = mSensorList; 
  25.      6) run("SensorService", PRIORITY_URGENT_DISPLAY);运行线程,并执行threadLoop 
  26.     */  
  27.     virtual void onFirstRef();   
  28.   
  29.     // Thread interface   
  30.     /* 
  31.       1) 调用SensorDevice.poll获取sensors_event_t事件 
  32.       2) 获取已经激活的sensor列表mActiveVirtualSensors 
  33.       3) 对每一个事件,执行SensorFusion.process 
  34.       4) 对每一个事件,执行HardwareSensor.process(事件无变化,直接copy) 
  35.       5) 调用SensorService::SensorEventConnection::sendEvents,把事件发 
  36.              送给所有的listener 
  37.     */  
  38.     virtual bool threadLoop();  
  39.   
  40.     // ISensorServer interface   
  41.     // 返回mUserSensorList   
  42.     virtual Vector getSensorList();  
  43.       
  44.     // 实例化SensorEventConnection并返回   
  45.     virtual sp createSensorEventConnection();  
  46.   
  47.     virtual status_t dump(int fd, const Vector& args);  
  48.   
  49.     //====================================================================   
  50.     //============== SensorEventConnection  start ========================   
  51.     class SensorEventConnection : public BnSensorEventConnection {  
  52.   
  53.         virtual ~SensorEventConnection();  
  54.         virtual void onFirstRef();  
  55.   
  56.     // 返回mChannel   
  57.         virtual sp getSensorChannel() const;  
  58.   
  59.     // 调用SensorService::enable或SensorService::disable   
  60.         virtual status_t enableDisable(int handle, bool enabled);  
  61.   
  62.         // 调用SensorService::setEventRate   
  63.         virtual status_t setEventRate(int handle, nsecs_t ns);  
  64.   
  65.         sp const mService; // 保存当前SensorService实例   
  66.         sp const mChannel; // SensorChannel实例   
  67.         mutable Mutex mConnectionLock;  
  68.   
  69.         // protected by SensorService::mLock   
  70.         SortedVector<int> mSensorInfo;  
  71.   
  72.     public:  
  73.         /* 
  74.           1) 把当前service保存在mService中 
  75.           2) 创建SensorChannel实例,并保存在mChannel中 
  76.              (在SensorChannel::SensorChannel中创建pipe,并把收和发都设置非阻塞) 
  77.         */  
  78.         SensorEventConnection(const sp& service);  
  79.   
  80.         // 调用连接中的mChannel->write (SensorChannel::write),把符合条件的事件写入pipe   
  81.         status_t sendEvents(sensors_event_t const* buffer, size_t count,  
  82.                 sensors_event_t* scratch = NULL);  
  83.   
  84.         bool hasSensor(int32_t handle) const//检查handle是否在mSensorInfo中   
  85.         bool hasAnySensor() const;   //检查mSensorInfo中是否有sensor   
  86.         bool addSensor(int32_t handle); //把handle增加到mSensorInfo列表中   
  87.         bool removeSensor(int32_t handle); //把handle从mSensorInfo中删除   
  88.     };  
  89.     //============== SensorEventConnection  end ========================   
  90.     //====================================================================   
  91.   
  92.     class SensorRecord {  
  93.         SortedVector< wp > mConnections;  
  94.     public:  
  95.         SensorRecord(const sp& connection);  
  96.         bool addConnection(const sp& connection);  
  97.         bool removeConnection(const wp& connection);  
  98.         size_t getNumConnections() const { return mConnections.size(); }  
  99.     };  
  100.   
  101.     SortedVector< wp > getActiveConnections() const;  
  102.     DefaultKeyedVector<int, SensorInterface*> getActiveVirtualSensors() const;  
  103.   
  104.     String8 getSensorName(int handle) const;  
  105.     void recordLastValue(sensors_event_t const * buffer, size_t count);  
  106.     static void sortEventBuffer(sensors_event_t* buffer, size_t count);  
  107.     void registerSensor(SensorInterface* sensor);  
  108.     void registerVirtualSensor(SensorInterface* sensor);  
  109.   
  110.     // constants   
  111.     Vector mSensorList;  // Sensor列表   
  112.     Vector mUserSensorList; //与mSensorList一样   
  113.     DefaultKeyedVector<int, SensorInterface*> mSensorMap; //其成员为HardwareSensor   
  114.     Vector mVirtualSensorList; //其成员为HardwareSensor   
  115.     status_t mInitCheck;  
  116.   
  117.     // protected by mLock   
  118.     mutable Mutex mLock;  
  119.     DefaultKeyedVector<int, SensorRecord*> mActiveSensors; //成员为SensorRecord   
  120.     DefaultKeyedVector<int, SensorInterface*> mActiveVirtualSensors; //成员为HardwareSensor   
  121.     SortedVector< wp > mActiveConnections;  
  122.   
  123.     // The size of this vector is constant, only the items are mutable   
  124.     KeyedVector mLastEventSeen;  
  125.   
  126. public:  
  127.     static char const* getServiceName() { return "sensorservice"; }  
  128.   
  129.     void cleanupConnection(SensorEventConnection* connection);  
  130.   
  131.     /* 
  132.       1) 调用HardwareSensor::activate,即SensorDevice::activate 
  133.       2) 然后创建SensorRecord并增加到列表mActiveSensors 
  134.       3) 把此HardwareSensor增加到连接的mSensorInfo 
  135.       4) 把此连接增加到mActiveConnections中 
  136.     */  
  137.     status_t enable(const sp& connection, int handle);  
  138.   
  139.     /* 
  140.        1) 把此sensor从连接的mSensorInfo中删除 
  141.        2) 把此连接从mActiveConnections中删除 
  142.        3) 调用HardwareSensor::activate,即SensorDevice::activate 
  143.     */  
  144.     status_t disable(const sp& connection, int handle);  
  145.     /* 
  146.        1)调用HardwareSensor::setDelay,即SensorDevice::setDelay 
  147.      */  
  148.     status_t setEventRate(const sp& connection, int handle, nsecs_t ns);  
  149. }  
class SensorService :
        public BinderService, //创建SensorService对象,并增加到ServiceManager中
        public BnSensorServer, // 申明了SensorService与客户端(SensorManager)间的binder接口
        protected Thread // 线程辅助类,调用run创建并启动线程,然后在线程主函数内回调threadLoop函数,
                         // 所以在使用它时,做一个派生,并根据需要重写threadLoop即可
                    
{
   friend class BinderService;

   static const nsecs_t MINIMUM_EVENTS_PERIOD =   1000000; // 1000 Hz

            SensorService();
    virtual ~SensorService();
   
    /*
    在addService时,第一次构建sp强引用对象时,会调用onFirstRef函数
     实现功能如下:
     1) 获取SensorDevice实例
     2) 调用SensorDevice.getSensorList获取sensor_t列表
     3) 根据硬件sensor_t创建HardwareSensor,然后加入mSensorList(Sensor)
            和mSensorMap(HardwareSensor)中
     4) 根据硬件sensor_t创建对应的senosr(如GravitySensor),
            然后加入mVirtualSensorList和mSensorList中
     5) mUserSensorList = mSensorList;
     6) run("SensorService", PRIORITY_URGENT_DISPLAY);运行线程,并执行threadLoop
    */
    virtual void onFirstRef(); 

    // Thread interface
    /*
      1) 调用SensorDevice.poll获取sensors_event_t事件
      2) 获取已经激活的sensor列表mActiveVirtualSensors
      3) 对每一个事件,执行SensorFusion.process
      4) 对每一个事件,执行HardwareSensor.process(事件无变化,直接copy)
      5) 调用SensorService::SensorEventConnection::sendEvents,把事件发
             送给所有的listener
    */
    virtual bool threadLoop();

    // ISensorServer interface
    // 返回mUserSensorList
    virtual Vector getSensorList();
    
    // 实例化SensorEventConnection并返回
    virtual sp createSensorEventConnection();

    virtual status_t dump(int fd, const Vector& args);

    //====================================================================
    //============== SensorEventConnection  start ========================
    class SensorEventConnection : public BnSensorEventConnection {

        virtual ~SensorEventConnection();
        virtual void onFirstRef();

	// 返回mChannel
        virtual sp getSensorChannel() const;

	// 调用SensorService::enable或SensorService::disable
        virtual status_t enableDisable(int handle, bool enabled);

        // 调用SensorService::setEventRate
        virtual status_t setEventRate(int handle, nsecs_t ns);

        sp const mService; // 保存当前SensorService实例
        sp const mChannel; // SensorChannel实例
        mutable Mutex mConnectionLock;

        // protected by SensorService::mLock
        SortedVector mSensorInfo;

    public:
        /*
          1) 把当前service保存在mService中
          2) 创建SensorChannel实例,并保存在mChannel中
             (在SensorChannel::SensorChannel中创建pipe,并把收和发都设置非阻塞)
        */
        SensorEventConnection(const sp& service);

        // 调用连接中的mChannel->write (SensorChannel::write),把符合条件的事件写入pipe
        status_t sendEvents(sensors_event_t const* buffer, size_t count,
                sensors_event_t* scratch = NULL);

        bool hasSensor(int32_t handle) const; //检查handle是否在mSensorInfo中
        bool hasAnySensor() const;   //检查mSensorInfo中是否有sensor
        bool addSensor(int32_t handle); //把handle增加到mSensorInfo列表中
        bool removeSensor(int32_t handle); //把handle从mSensorInfo中删除
    };
    //============== SensorEventConnection  end ========================
    //====================================================================

    class SensorRecord {
        SortedVector< wp > mConnections;
    public:
        SensorRecord(const sp& connection);
        bool addConnection(const sp& connection);
        bool removeConnection(const wp& connection);
        size_t getNumConnections() const { return mConnections.size(); }
    };

    SortedVector< wp > getActiveConnections() const;
    DefaultKeyedVector getActiveVirtualSensors() const;

    String8 getSensorName(int handle) const;
    void recordLastValue(sensors_event_t const * buffer, size_t count);
    static void sortEventBuffer(sensors_event_t* buffer, size_t count);
    void registerSensor(SensorInterface* sensor);
    void registerVirtualSensor(SensorInterface* sensor);

    // constants
    Vector mSensorList;  // Sensor列表
    Vector mUserSensorList; //与mSensorList一样
    DefaultKeyedVector mSensorMap; //其成员为HardwareSensor
    Vector mVirtualSensorList; //其成员为HardwareSensor
    status_t mInitCheck;

    // protected by mLock
    mutable Mutex mLock;
    DefaultKeyedVector mActiveSensors; //成员为SensorRecord
    DefaultKeyedVector mActiveVirtualSensors; //成员为HardwareSensor
    SortedVector< wp > mActiveConnections;

    // The size of this vector is constant, only the items are mutable
    KeyedVector mLastEventSeen;

public:
    static char const* getServiceName() { return "sensorservice"; }

    void cleanupConnection(SensorEventConnection* connection);

    /*
      1) 调用HardwareSensor::activate,即SensorDevice::activate
      2) 然后创建SensorRecord并增加到列表mActiveSensors
      3) 把此HardwareSensor增加到连接的mSensorInfo
      4) 把此连接增加到mActiveConnections中
    */
    status_t enable(const sp& connection, int handle);

    /*
       1) 把此sensor从连接的mSensorInfo中删除
       2) 把此连接从mActiveConnections中删除
       3) 调用HardwareSensor::activate,即SensorDevice::activate
    */
    status_t disable(const sp& connection, int handle);
    /*
       1)调用HardwareSensor::setDelay,即SensorDevice::setDelay
     */
    status_t setEventRate(const sp& connection, int handle, nsecs_t ns);
}


2.5 SensorDevice.cpp

      SensorDevice封装了对SensorHAL层代码的调用,主要包含以下功能:
         1) 获取sensor列表(getSensorList)
         2) 获取sensor事件(poll)
         3) Enable或Disable sensor (activate)
         4) 设置delay时间

 

[cpp] view plain copy print ?
  1. class SensorDevice : public Singleton {  
  2.   
  3.     friend class Singleton;  
  4.   
  5.     struct sensors_poll_device_t* mSensorDevice; // sensor设备   
  6.   
  7.     struct sensors_module_t* mSensorModule;  
  8.   
  9.     mutable Mutex mLock; // protect mActivationCount[].rates   
  10.     // fixed-size array after construction   
  11.     struct Info {  
  12.         Info() : delay(0) { }  
  13.         KeyedVector<void*, nsecs_t> rates;  
  14.         nsecs_t delay;  
  15.         status_t setDelayForIdent(void* ident, int64_t ns);  
  16.         nsecs_t selectDelay();  
  17.     };  
  18.     DefaultKeyedVector<int, Info> mActivationCount;  
  19.   
  20.     /* 
  21.       1) 调用hw_get_module(SENSORS_HARDWARE_MODULE_ID,..)获取sensors_module_t, 
  22.              并保存在mSensorModule中 
  23.       2) 调用mSensorModule->common->methods->open,以返回sensors_poll_device_t, 
  24.              并保存在mSensorDevice中 
  25.       3) 调用mSensorModule->get_sensors_list所有可访问的sensor_t 
  26.       4) 调用mSensorDevice->activate激活所有的sensor 
  27.     */  
  28.     SensorDevice();  
  29. public:  
  30.     // 调用mSensorModule->get_sensors_list实现   
  31.     ssize_t getSensorList(sensor_t const** list);  
  32.   
  33.     status_t initCheck() const;  
  34.   
  35.     // 调用mSensorDevice->poll实现   
  36.     ssize_t poll(sensors_event_t* buffer, size_t count);  
  37.   
  38.     // 调用mSensorDevice->activate实现   
  39.     status_t activate(void* ident, int handle, int enabled);  
  40.       
  41.     // 调用mSensorDevice->setDelay实现   
  42.     status_t setDelay(void* ident, int handle, int64_t ns);  
  43.     void dump(String8& result, char* buffer, size_t SIZE);  
  44. };  
class SensorDevice : public Singleton {

    friend class Singleton;

    struct sensors_poll_device_t* mSensorDevice; // sensor设备

    struct sensors_module_t* mSensorModule;

    mutable Mutex mLock; // protect mActivationCount[].rates
    // fixed-size array after construction
    struct Info {
        Info() : delay(0) { }
        KeyedVector rates;
        nsecs_t delay;
        status_t setDelayForIdent(void* ident, int64_t ns);
        nsecs_t selectDelay();
    };
    DefaultKeyedVector mActivationCount;

    /*
      1) 调用hw_get_module(SENSORS_HARDWARE_MODULE_ID,..)获取sensors_module_t,
             并保存在mSensorModule中
      2) 调用mSensorModule->common->methods->open,以返回sensors_poll_device_t,
             并保存在mSensorDevice中
      3) 调用mSensorModule->get_sensors_list所有可访问的sensor_t
      4) 调用mSensorDevice->activate激活所有的sensor
    */
    SensorDevice();
public:
    // 调用mSensorModule->get_sensors_list实现
    ssize_t getSensorList(sensor_t const** list);

    status_t initCheck() const;

    // 调用mSensorDevice->poll实现
    ssize_t poll(sensors_event_t* buffer, size_t count);

    // 调用mSensorDevice->activate实现
    status_t activate(void* ident, int handle, int enabled);
    
    // 调用mSensorDevice->setDelay实现
    status_t setDelay(void* ident, int handle, int64_t ns);
    void dump(String8& result, char* buffer, size_t SIZE);
};


2.6 Sensor HAL

定义:/hardware/libhardware/include/hardware/sensors.h

实现:/hardware/mychip/sensor/st/sensors.c

2.6.1 struct sensors_poll_device_t 定义     

[cpp] view plain copy print ?
  1. struct sensors_poll_device_t {  
  2.     struct hw_device_t common;  
  3.   
  4.     // Activate/deactivate one sensor.   
  5.     int (*activate)(struct sensors_poll_device_t *dev,  
  6.             int handle, int enabled);  
  7.   
  8.     // Set the delay between sensor events in nanoseconds for a given sensor.   
  9.     int (*setDelay)(struct sensors_poll_device_t *dev,  
  10.             int handle, int64_t ns);  
  11.   
  12.     // Returns an array of sensor data.   
  13.     int (*poll)(struct sensors_poll_device_t *dev,  
  14.             sensors_event_t* data, int count);  
  15. };  
struct sensors_poll_device_t {
    struct hw_device_t common;

    // Activate/deactivate one sensor.
    int (*activate)(struct sensors_poll_device_t *dev,
            int handle, int enabled);

    // Set the delay between sensor events in nanoseconds for a given sensor.
    int (*setDelay)(struct sensors_poll_device_t *dev,
            int handle, int64_t ns);

    // Returns an array of sensor data.
    int (*poll)(struct sensors_poll_device_t *dev,
            sensors_event_t* data, int count);
};

2.6.2 struct sensors_module_t  定义

[cpp] view plain copy print ?
  1. struct sensors_module_t {  
  2.     struct hw_module_t common;  
  3.   
  4.     /** 
  5.      * Enumerate all available sensors. The list is returned in "list". 
  6.      * @return number of sensors in the list 
  7.      */  
  8.     int (*get_sensors_list)(struct sensors_module_t* module,  
  9.             struct sensor_t const** list);  
  10. };  
struct sensors_module_t {
    struct hw_module_t common;

    /**
     * Enumerate all available sensors. The list is returned in "list".
     * @return number of sensors in the list
     */
    int (*get_sensors_list)(struct sensors_module_t* module,
            struct sensor_t const** list);
};

2.6.3  struct sensor_t 定义

[cpp] view plain copy print ?
  1. struct sensor_t {  
  2.     /* name of this sensors */  
  3.     const char*     name;  
  4.     /* vendor of the hardware part */  
  5.     const char*     vendor;  
  6.     /* version of the hardware part + driver. The value of this field 
  7.      * must increase when the driver is updated in a way that changes the 
  8.      * output of this sensor. This is important for fused sensors when the 
  9.      * fusion algorithm is updated. 
  10.      */      
  11.     int             version;  
  12.     /* handle that identifies this sensors. This handle is used to activate 
  13.      * and deactivate this sensor. The value of the handle must be 8 bits 
  14.      * in this version of the API.  
  15.      */  
  16.     int             handle;  
  17.     /* this sensor's type. */  
  18.     int             type;  
  19.     /* maximaum range of this sensor's value in SI units */  
  20.     float           maxRange;  
  21.     /* smallest difference between two values reported by this sensor */  
  22.     float           resolution;  
  23.     /* rough estimate of this sensor's power consumption in mA */  
  24.     float           power;  
  25.     /* minimum delay allowed between events in microseconds. A value of zero 
  26.      * means that this sensor doesn't report events at a constant rate, but 
  27.      * rather only when a new data is available */  
  28.     int32_t         minDelay;  
  29.     /* reserved fields, must be zero */  
  30.     void*           reserved[8];  
  31. };  
struct sensor_t {
    /* name of this sensors */
    const char*     name;
    /* vendor of the hardware part */
    const char*     vendor;
    /* version of the hardware part + driver. The value of this field
     * must increase when the driver is updated in a way that changes the
     * output of this sensor. This is important for fused sensors when the
     * fusion algorithm is updated.
     */    
    int             version;
    /* handle that identifies this sensors. This handle is used to activate
     * and deactivate this sensor. The value of the handle must be 8 bits
     * in this version of the API. 
     */
    int             handle;
    /* this sensor's type. */
    int             type;
    /* maximaum range of this sensor's value in SI units */
    float           maxRange;
    /* smallest difference between two values reported by this sensor */
    float           resolution;
    /* rough estimate of this sensor's power consumption in mA */
    float           power;
    /* minimum delay allowed between events in microseconds. A value of zero
     * means that this sensor doesn't report events at a constant rate, but
     * rather only when a new data is available */
    int32_t         minDelay;
    /* reserved fields, must be zero */
    void*           reserved[8];
};

2.6.4 struct sensors_event_t 定义

[cpp] view plain copy print ?
  1. typedef struct {  
  2.     union {  
  3.         float v[3];  
  4.         struct {  
  5.             float x;  
  6.             float y;  
  7.             float z;  
  8.         };  
  9.         struct {  
  10.             float azimuth;  
  11.             float pitch;  
  12.             float roll;  
  13.         };  
  14.     };  
  15.     int8_t status;  
  16.     uint8_t reserved[3];  
  17. } sensors_vec_t;  
  18.   
  19. /** 
  20.  * Union of the various types of sensor data 
  21.  * that can be returned. 
  22.  */  
  23. typedef struct sensors_event_t {  
  24.     /* must be sizeof(struct sensors_event_t) */  
  25.     int32_t version;  
  26.   
  27.     /* sensor identifier */  
  28.     int32_t sensor;  
  29.   
  30.     /* sensor type */  
  31.     int32_t type;  
  32.   
  33.     /* reserved */  
  34.     int32_t reserved0;  
  35.   
  36.     /* time is in nanosecond */  
  37.     int64_t timestamp;  
  38.   
  39.     union {  
  40.         float           data[16];  
  41.   
  42.         /* acceleration values are in meter per second per second (m/s^2) */  
  43.         sensors_vec_t   acceleration;  
  44.   
  45.         /* magnetic vector values are in micro-Tesla (uT) */  
  46.         sensors_vec_t   magnetic;  
  47.   
  48.         /* orientation values are in degrees */  
  49.         sensors_vec_t   orientation;  
  50.   
  51.         /* gyroscope values are in rad/s */  
  52.         sensors_vec_t   gyro;  
  53.   
  54.         /* temperature is in degrees centigrade (Celsius) */  
  55.         float           temperature;  
  56.   
  57.         /* distance in centimeters */  
  58.         float           distance;  
  59.   
  60.         /* light in SI lux units */  
  61.         float           light;  
  62.   
  63.         /* pressure in hectopascal (hPa) */  
  64.         float           pressure;  
  65.   
  66.         /* relative humidity in percent */  
  67.         float           relative_humidity;  
  68.     };  
  69.     uint32_t        reserved1[4];  
  70. } sensors_event_t;  
typedef struct {
    union {
        float v[3];
        struct {
            float x;
            float y;
            float z;
        };
        struct {
            float azimuth;
            float pitch;
            float roll;
        };
    };
    int8_t status;
    uint8_t reserved[3];
} sensors_vec_t;

/**
 * Union of the various types of sensor data
 * that can be returned.
 */
typedef struct sensors_event_t {
    /* must be sizeof(struct sensors_event_t) */
    int32_t version;

    /* sensor identifier */
    int32_t sensor;

    /* sensor type */
    int32_t type;

    /* reserved */
    int32_t reserved0;

    /* time is in nanosecond */
    int64_t timestamp;

    union {
        float           data[16];

        /* acceleration values are in meter per second per second (m/s^2) */
        sensors_vec_t   acceleration;

        /* magnetic vector values are in micro-Tesla (uT) */
        sensors_vec_t   magnetic;

        /* orientation values are in degrees */
        sensors_vec_t   orientation;

        /* gyroscope values are in rad/s */
        sensors_vec_t   gyro;

        /* temperature is in degrees centigrade (Celsius) */
        float           temperature;

        /* distance in centimeters */
        float           distance;

        /* light in SI lux units */
        float           light;

        /* pressure in hectopascal (hPa) */
        float           pressure;

        /* relative humidity in percent */
        float           relative_humidity;
    };
    uint32_t        reserved1[4];
} sensors_event_t;


2.6.5 struct sensors_module_t 实现

[cpp] view plain copy print ?
  1. #include    
  2. #include "nusensors.h"   
  3.   
  4. /* 
  5.  * the AK8973 has a 8-bit ADC but the firmware seems to average 16 samples, 
  6.  * or at least makes its calibration on 12-bits values. This increases the 
  7.  * resolution by 4 bits. 
  8.  */  
  9. static const struct sensor_t sSensorList[] = {  
  10.         { "MMA8452Q 3-axis Accelerometer",      
  11.                 "Freescale Semiconductor",  
  12.                 1, SENSORS_HANDLE_BASE+ID_A,  
  13.                 SENSOR_TYPE_ACCELEROMETER, 4.0f*9.81f, (4.0f*9.81f)/256.0f, 0.2f, 0, { } },  
  14.         { "AK8975 3-axis Magnetic field sensor",  
  15.                 "Asahi Kasei",  
  16.                 1, SENSORS_HANDLE_BASE+ID_M,  
  17.                 SENSOR_TYPE_MAGNETIC_FIELD, 2000.0f, 1.0f/16.0f, 6.8f, 0, { } },  
  18.         { "AK8975 Orientation sensor",  
  19.                 "Asahi Kasei",  
  20.                 1, SENSORS_HANDLE_BASE+ID_O,  
  21.                 SENSOR_TYPE_ORIENTATION, 360.0f, 1.0f, 7.0f, 0, { } },   
  22.   
  23.     { "ST 3-axis Gyroscope sensor",  
  24.           "STMicroelectronics",  
  25.           1, SENSORS_HANDLE_BASE+ID_GY,  
  26.           SENSOR_TYPE_GYROSCOPE, RANGE_GYRO, CONVERT_GYRO, 6.1f, 1190, { } },  
  27.               
  28.     { "AL3006Proximity sensor",  
  29.         "Dyna Image Corporation",  
  30.         1, SENSORS_HANDLE_BASE+ID_P,  
  31.         SENSOR_TYPE_PROXIMITY,  
  32.         PROXIMITY_THRESHOLD_CM, PROXIMITY_THRESHOLD_CM,  
  33.         0.5f, 0, { } },  
  34.           
  35.         { "AL3006 light sensor",  
  36.                 "Dyna Image Corporation",  
  37.                 1, SENSORS_HANDLE_BASE+ID_L,  
  38.                 SENSOR_TYPE_LIGHT, 10240.0f, 1.0f, 0.5f, 0, { } },  
  39.   
  40. };  
  41.   
  42. static int open_sensors(const struct hw_module_t* module, const char* name,  
  43.         struct hw_device_t** device);  
  44.   
  45. static int sensors__get_sensors_list(struct sensors_module_t* module,  
  46.         struct sensor_t const** list)  
  47. {  
  48.     *list = sSensorList;  
  49.     return ARRAY_SIZE(sSensorList);  
  50. }  
  51.   
  52. static struct hw_module_methods_t sensors_module_methods = {  
  53.     .open = open_sensors  
  54. };  
  55.   
  56. const struct sensors_module_t HAL_MODULE_INFO_SYM = {  
  57.     .common = {  
  58.         .tag = HARDWARE_MODULE_TAG,  
  59.         .version_major = 1,  
  60.         .version_minor = 0,  
  61.         .id = SENSORS_HARDWARE_MODULE_ID,  
  62.         .name = "MMA8451Q & AK8973A & gyro Sensors Module",  
  63.         .author = "The Android Project",  
  64.         .methods = &sensors_module_methods,  
  65.     },  
  66.     .get_sensors_list = sensors__get_sensors_list  
  67. };  
  68.   
  69. static int open_sensors(const struct hw_module_t* module, const char* name,  
  70.         struct hw_device_t** device)  
  71. {  
  72.     return init_nusensors(module, device); //待后面讲解   
  73. }  
#include 
#include "nusensors.h"

/*
 * the AK8973 has a 8-bit ADC but the firmware seems to average 16 samples,
 * or at least makes its calibration on 12-bits values. This increases the
 * resolution by 4 bits.
 */
static const struct sensor_t sSensorList[] = {
        { "MMA8452Q 3-axis Accelerometer",    
            	"Freescale Semiconductor",
                1, SENSORS_HANDLE_BASE+ID_A,
                SENSOR_TYPE_ACCELEROMETER, 4.0f*9.81f, (4.0f*9.81f)/256.0f, 0.2f, 0, { } },
        { "AK8975 3-axis Magnetic field sensor",
                "Asahi Kasei",
                1, SENSORS_HANDLE_BASE+ID_M,
                SENSOR_TYPE_MAGNETIC_FIELD, 2000.0f, 1.0f/16.0f, 6.8f, 0, { } },
        { "AK8975 Orientation sensor",
                "Asahi Kasei",
                1, SENSORS_HANDLE_BASE+ID_O,
                SENSOR_TYPE_ORIENTATION, 360.0f, 1.0f, 7.0f, 0, { } }, 

	{ "ST 3-axis Gyroscope sensor",
          "STMicroelectronics",
          1, SENSORS_HANDLE_BASE+ID_GY,
          SENSOR_TYPE_GYROSCOPE, RANGE_GYRO, CONVERT_GYRO, 6.1f, 1190, { } },
			
	{ "AL3006Proximity sensor",
		"Dyna Image Corporation",
		1, SENSORS_HANDLE_BASE+ID_P,
		SENSOR_TYPE_PROXIMITY,
		PROXIMITY_THRESHOLD_CM, PROXIMITY_THRESHOLD_CM,
		0.5f, 0, { } },
		
        { "AL3006 light sensor",
                "Dyna Image Corporation",
                1, SENSORS_HANDLE_BASE+ID_L,
                SENSOR_TYPE_LIGHT, 10240.0f, 1.0f, 0.5f, 0, { } },

};

static int open_sensors(const struct hw_module_t* module, const char* name,
        struct hw_device_t** device);

static int sensors__get_sensors_list(struct sensors_module_t* module,
        struct sensor_t const** list)
{
    *list = sSensorList;
    return ARRAY_SIZE(sSensorList);
}

static struct hw_module_methods_t sensors_module_methods = {
    .open = open_sensors
};

const struct sensors_module_t HAL_MODULE_INFO_SYM = {
    .common = {
        .tag = HARDWARE_MODULE_TAG,
        .version_major = 1,
        .version_minor = 0,
        .id = SENSORS_HARDWARE_MODULE_ID,
        .name = "MMA8451Q & AK8973A & gyro Sensors Module",
        .author = "The Android Project",
        .methods = &sensors_module_methods,
    },
    .get_sensors_list = sensors__get_sensors_list
};

static int open_sensors(const struct hw_module_t* module, const char* name,
        struct hw_device_t** device)
{
    return init_nusensors(module, device); //待后面讲解
}

2.6.6 struct sensors_poll_device_t 实现

    实现代码位于:/hardware/mychip/sensor/st/nusensors.cpp

    从上面的代码中可以看出,当调用init_nusensors时,它将返回sensors_poll_device_t,然后就可以调用sensors_poll_device_t 的以下方法进行相关操作:

      1) activate 
      2) setDelay
      3) poll

6.1) struct sensors_poll_context_t 定义 

[cpp] view plain copy print ?
  1. struct sensors_poll_context_t {  
  2.     struct sensors_poll_device_t device; // must be first   
  3.   
  4.         sensors_poll_context_t();  
  5.         ~sensors_poll_context_t();  
  6.     int activate(int handle, int enabled);  
  7.     int setDelay(int handle, int64_t ns);  
  8.     int pollEvents(sensors_event_t* data, int count);  
  9.   
  10. private:  
  11.     enum {        
  12.         light           = 0,  
  13.         proximity       = 1,  
  14.         mma             = 2,  
  15.         akm             = 3,  
  16.         gyro            = 4,  
  17.         numSensorDrivers,  
  18.         numFds,  
  19.     };  
  20.   
  21.     static const size_t wake = numFds - 1;  
  22.     static const char WAKE_MESSAGE = 'W';  
  23.     struct pollfd mPollFds[numFds];  
  24.     int mWritePipeFd;  
  25.     SensorBase* mSensors[numSensorDrivers];  
  26.   
  27.     int handleToDriver(int handle) const {  
  28.         switch (handle) {  
  29.             case ID_A:  
  30.                 return mma;  
  31.             case ID_M:  
  32.             case ID_O:  
  33.                 return akm;   
  34.             case ID_P:  
  35.                 return proximity;  
  36.             case ID_L:  
  37.                 return light;     
  38.             case ID_GY:  
  39.                 return gyro;  
  40.         }  
  41.         return -EINVAL;  
  42.     }  
  43. }  
struct sensors_poll_context_t {
    struct sensors_poll_device_t device; // must be first

        sensors_poll_context_t();
        ~sensors_poll_context_t();
    int activate(int handle, int enabled);
    int setDelay(int handle, int64_t ns);
    int pollEvents(sensors_event_t* data, int count);

private:
    enum {		
        light           = 0,
        proximity       = 1,
        mma             = 2,
        akm             = 3,
        gyro            = 4,
        numSensorDrivers,
        numFds,
    };

    static const size_t wake = numFds - 1;
    static const char WAKE_MESSAGE = 'W';
    struct pollfd mPollFds[numFds];
    int mWritePipeFd;
    SensorBase* mSensors[numSensorDrivers];

    int handleToDriver(int handle) const {
        switch (handle) {
            case ID_A:
                return mma;
            case ID_M:
			case ID_O:
                return akm;	
            case ID_P:
                return proximity;
            case ID_L:
                return light;	
			case ID_GY:
				return gyro;
        }
        return -EINVAL;
    }
}

6.2) init_nusensors 实现

[cpp] view plain copy print ?
  1. int init_nusensors(hw_module_t const* module, hw_device_t** device)  
  2. {  
  3.     int status = -EINVAL;  
  4.   
  5.     sensors_poll_context_t *dev = new sensors_poll_context_t();  
  6.     memset(&dev->device, 0, sizeof(sensors_poll_device_t));  
  7.   
  8.     dev->device.common.tag = HARDWARE_DEVICE_TAG;  
  9.     dev->device.common.version  = 0;  
  10.     dev->device.common.module   = const_cast(module);  
  11.     dev->device.common.close    = poll__close;  
  12.     dev->device.activate        = poll__activate;  
  13.     dev->device.setDelay        = poll__setDelay;  
  14.     dev->device.poll            = poll__poll;  
  15.   
  16.     *device = &dev->device.common;  
  17.     status = 0;  
  18.     return status;  
  19. }  
int init_nusensors(hw_module_t const* module, hw_device_t** device)
{
    int status = -EINVAL;

    sensors_poll_context_t *dev = new sensors_poll_context_t();
    memset(&dev->device, 0, sizeof(sensors_poll_device_t));

    dev->device.common.tag = HARDWARE_DEVICE_TAG;
    dev->device.common.version  = 0;
    dev->device.common.module   = const_cast(module);
    dev->device.common.close    = poll__close;
    dev->device.activate        = poll__activate;
    dev->device.setDelay        = poll__setDelay;
    dev->device.poll            = poll__poll;

    *device = &dev->device.common;
    status = 0;
    return status;
}

     由以上代码可见,sensors_poll_device_t的activate、setDelay和poll的实现函数分别为:

        (1)  poll__activate

        (2)   poll__setDelay

        (3)   poll__poll

     下面讲解以上三个关键函数的实现

6.3) struct sensors_poll_context_t 的实现

[cpp] view plain copy print ?
  1. sensors_poll_context_t::sensors_poll_context_t()  
  2. {     
  3.     mSensors[light] = new LightSensor();  
  4.     mPollFds[light].fd = mSensors[light]->getFd();  
  5.     mPollFds[light].events = POLLIN;  
  6.     mPollFds[light].revents = 0;  
  7.   
  8.     mSensors[proximity] = new ProximitySensor();  
  9.     mPollFds[proximity].fd = mSensors[proximity]->getFd();  
  10.     mPollFds[proximity].events = POLLIN;  
  11.     mPollFds[proximity].revents = 0;  
  12.       
  13.   
  14.     mSensors[mma] = new MmaSensor();  //下面MmmaSensor为例进行分析   
  15.     mPollFds[mma].fd = mSensors[mma]->getFd();  
  16.     mPollFds[mma].events = POLLIN;  
  17.     mPollFds[mma].revents = 0;  
  18.   
  19.     mSensors[akm] = new AkmSensor();  
  20.     mPollFds[akm].fd = mSensors[akm]->getFd();  
  21.     mPollFds[akm].events = POLLIN;  
  22.     mPollFds[akm].revents = 0;  
  23.   
  24.     mSensors[gyro] = new GyroSensor();  
  25.     mPollFds[gyro].fd = mSensors[gyro]->getFd();  
  26.     mPollFds[gyro].events = POLLIN;  
  27.     mPollFds[gyro].revents = 0;  
  28.   
  29.     int wakeFds[2];  
  30.     int result = pipe(wakeFds);  
  31.     LOGE_IF(result<0, "error creating wake pipe (%s)", strerror(errno));  
  32.     fcntl(wakeFds[0], F_SETFL, O_NONBLOCK);  
  33.     fcntl(wakeFds[1], F_SETFL, O_NONBLOCK);  
  34.     mWritePipeFd = wakeFds[1];  
  35.   
  36.     mPollFds[wake].fd = wakeFds[0];  
  37.     mPollFds[wake].events = POLLIN;  
  38.     mPollFds[wake].revents = 0;  
  39. }  
  40.   
  41. sensors_poll_context_t::~sensors_poll_context_t() {  
  42.     for (int i=0 ; i
  43.         delete mSensors[i];  
  44.     }  
  45.     close(mPollFds[wake].fd);  
  46.     close(mWritePipeFd);  
  47. }  
  48.   
  49. int sensors_poll_context_t::activate(int handle, int enabled) {  
  50.     int index = handleToDriver(handle);  
  51.     if (index < 0) return index;  
  52.     int err =  mSensors[index]->enable(handle, enabled);  
  53.     if (enabled && !err) {  
  54.         const char wakeMessage(WAKE_MESSAGE);  
  55.         int result = write(mWritePipeFd, &wakeMessage, 1);  
  56.         LOGE_IF(result<0, "error sending wake message (%s)", strerror(errno));  
  57.     }  
  58.     return err;  
  59. }  
  60.   
  61. int sensors_poll_context_t::setDelay(int handle, int64_t ns) {  
  62.   
  63.     int index = handleToDriver(handle);  
  64.     if (index < 0) return index;  
  65.     return mSensors[index]->setDelay(handle, ns);  
  66. }  
  67.   
  68. int sensors_poll_context_t::pollEvents(sensors_event_t* data, int count)  
  69. {  
  70.     int nbEvents = 0;  
  71.     int n = 0;  
  72.   
  73.     do {  
  74.         // see if we have some leftover from the last poll()   
  75.         for (int i=0 ; count && i
  76.             SensorBase* const sensor(mSensors[i]);  
  77.             if ((mPollFds[i].revents & POLLIN) || (sensor->hasPendingEvents())) {  
  78.                 int nb = sensor->readEvents(data, count);    // num of evens received.   
  79.                 D("nb = %d.", nb);  
  80.                 if (nb < count) {  
  81.                     // no more data for this sensor   
  82.                     mPollFds[i].revents = 0;  
  83.                 }  
  84.                 count -= nb;  
  85.                 nbEvents += nb;  
  86.                 data += nb;  
  87.             }  
  88.         }  
  89.   
  90.         if (count) {  
  91.             // we still have some room, so try to see if we can get   
  92.             // some events immediately or just wait if we don't have   
  93.             // anything to return   
  94.             n = poll(mPollFds, numFds, nbEvents ? 0 : -1);  
  95.             if (n<0) {  
  96.                 LOGE("poll() failed (%s)", strerror(errno));  
  97.                 return -errno;  
  98.             }  
  99.             if (mPollFds[wake].revents & POLLIN) {  
  100.                 char msg;  
  101.                 int result = read(mPollFds[wake].fd, &msg, 1);  
  102.                 LOGE_IF(result<0, "error reading from wake pipe (%s)", strerror(errno));  
  103.                 LOGE_IF(msg != WAKE_MESSAGE, "unknown message on wake queue (0x%02x)"int(msg));  
  104.                 mPollFds[wake].revents = 0;  
  105.             }  
  106.         }  
  107.         // if we have events and space, go read them   
  108.     } while (n && count);  
  109.   
  110.     return nbEvents;  
  111. }  
  112.   
  113. /*****************************************************************************/  
  114.   
  115. static int poll__close(struct hw_device_t *dev)  
  116. {  
  117.     sensors_poll_context_t *ctx = (sensors_poll_context_t *)dev;  
  118.     if (ctx) {  
  119.         delete ctx;  
  120.     }  
  121.     return 0;  
  122. }  
  123.   
  124. static int poll__activate(struct sensors_poll_device_t *dev,  
  125.         int handle, int enabled) {  
  126.     sensors_poll_context_t *ctx = (sensors_poll_context_t *)dev;  
  127.     return ctx->activate(handle, enabled);  
  128. }  
  129.   
  130. static int poll__setDelay(struct sensors_poll_device_t *dev,  
  131.         int handle, int64_t ns) {  
  132.     sensors_poll_context_t *ctx = (sensors_poll_context_t *)dev;  
  133.     return ctx->setDelay(handle, ns);  
  134. }  
  135.   
  136. static int poll__poll(struct sensors_poll_device_t *dev,  
  137.         sensors_event_t* data, int count) {  
  138.     sensors_poll_context_t *ctx = (sensors_poll_context_t *)dev;  
  139.     return ctx->pollEvents(data, count);  
  140. }  
sensors_poll_context_t::sensors_poll_context_t()
{	
    mSensors[light] = new LightSensor();
    mPollFds[light].fd = mSensors[light]->getFd();
    mPollFds[light].events = POLLIN;
    mPollFds[light].revents = 0;

    mSensors[proximity] = new ProximitySensor();
    mPollFds[proximity].fd = mSensors[proximity]->getFd();
    mPollFds[proximity].events = POLLIN;
    mPollFds[proximity].revents = 0;
	

    mSensors[mma] = new MmaSensor();  //下面MmmaSensor为例进行分析
    mPollFds[mma].fd = mSensors[mma]->getFd();
    mPollFds[mma].events = POLLIN;
    mPollFds[mma].revents = 0;

    mSensors[akm] = new AkmSensor();
    mPollFds[akm].fd = mSensors[akm]->getFd();
    mPollFds[akm].events = POLLIN;
    mPollFds[akm].revents = 0;

	mSensors[gyro] = new GyroSensor();
    mPollFds[gyro].fd = mSensors[gyro]->getFd();
    mPollFds[gyro].events = POLLIN;
    mPollFds[gyro].revents = 0;

    int wakeFds[2];
    int result = pipe(wakeFds);
    LOGE_IF(result<0, "error creating wake pipe (%s)", strerror(errno));
    fcntl(wakeFds[0], F_SETFL, O_NONBLOCK);
    fcntl(wakeFds[1], F_SETFL, O_NONBLOCK);
    mWritePipeFd = wakeFds[1];

    mPollFds[wake].fd = wakeFds[0];
    mPollFds[wake].events = POLLIN;
    mPollFds[wake].revents = 0;
}

sensors_poll_context_t::~sensors_poll_context_t() {
    for (int i=0 ; ienable(handle, enabled);
    if (enabled && !err) {
        const char wakeMessage(WAKE_MESSAGE);
        int result = write(mWritePipeFd, &wakeMessage, 1);
        LOGE_IF(result<0, "error sending wake message (%s)", strerror(errno));
    }
    return err;
}

int sensors_poll_context_t::setDelay(int handle, int64_t ns) {

    int index = handleToDriver(handle);
    if (index < 0) return index;
    return mSensors[index]->setDelay(handle, ns);
}

int sensors_poll_context_t::pollEvents(sensors_event_t* data, int count)
{
    int nbEvents = 0;
    int n = 0;

    do {
        // see if we have some leftover from the last poll()
        for (int i=0 ; count && ihasPendingEvents())) {
                int nb = sensor->readEvents(data, count);	// num of evens received.
				D("nb = %d.", nb);
                if (nb < count) {
                    // no more data for this sensor
                    mPollFds[i].revents = 0;
                }
                count -= nb;
                nbEvents += nb;
                data += nb;
            }
        }

        if (count) {
            // we still have some room, so try to see if we can get
            // some events immediately or just wait if we don't have
            // anything to return
            n = poll(mPollFds, numFds, nbEvents ? 0 : -1);
            if (n<0) {
                LOGE("poll() failed (%s)", strerror(errno));
                return -errno;
            }
            if (mPollFds[wake].revents & POLLIN) {
                char msg;
                int result = read(mPollFds[wake].fd, &msg, 1);
                LOGE_IF(result<0, "error reading from wake pipe (%s)", strerror(errno));
                LOGE_IF(msg != WAKE_MESSAGE, "unknown message on wake queue (0x%02x)", int(msg));
                mPollFds[wake].revents = 0;
            }
        }
        // if we have events and space, go read them
    } while (n && count);

    return nbEvents;
}

/*****************************************************************************/

static int poll__close(struct hw_device_t *dev)
{
    sensors_poll_context_t *ctx = (sensors_poll_context_t *)dev;
    if (ctx) {
        delete ctx;
    }
    return 0;
}

static int poll__activate(struct sensors_poll_device_t *dev,
        int handle, int enabled) {
    sensors_poll_context_t *ctx = (sensors_poll_context_t *)dev;
    return ctx->activate(handle, enabled);
}

static int poll__setDelay(struct sensors_poll_device_t *dev,
        int handle, int64_t ns) {
    sensors_poll_context_t *ctx = (sensors_poll_context_t *)dev;
    return ctx->setDelay(handle, ns);
}

static int poll__poll(struct sensors_poll_device_t *dev,
        sensors_event_t* data, int count) {
    sensors_poll_context_t *ctx = (sensors_poll_context_t *)dev;
    return ctx->pollEvents(data, count);
}

下面MmaSensor为例进行分析。

2.7 MmaSensor.cpp

1)  SensorBase的实现(SensorBase.cpp)

[cpp] view plain copy print ?
  1. class SensorBase {  
  2. protected:  
  3.     const char* dev_name; // "/dev/mma8452_daemon"   
  4.     const char* data_name; // "gsensor"   
  5.     int         dev_fd; // 打开设备"/dev/mma8452_daemon"的fd   
  6.       
  7.     // 打开事件"/dev/input/eventx"的fd,其驱动的名字为"gsensor"   
  8.     int         data_fd;   
  9.       
  10.     // 打开与"gsensor"对应的事件"/dev/input/eventx"   
  11.     static int openInput(const char* inputName);   
  12.   
  13.     //通过clock_gettime获取当前时间   
  14.     static int64_t getTimestamp();   
  15.   
  16.   
  17.     static int64_t timevalToNano(timeval const& t) {  
  18.         return t.tv_sec*1000000000LL + t.tv_usec*1000;  
  19.     }  
  20.   
  21.     int open_device(); //打开设备"dev/mma8452_daemon"   
  22.     int close_device(); //关闭设备"dev/mma8452_daemon"   
  23.   
  24. public:  
  25.     // 调用openInput   
  26.             SensorBase(  
  27.                     const char* dev_name,  
  28.                     const char* data_name);  
  29.   
  30.     virtual ~SensorBase();  
  31.   
  32.     virtual int readEvents(sensors_event_t* data, int count) = 0;  
  33.     virtual bool hasPendingEvents() const;  
  34.     virtual int getFd() const;  //返回data_fd   
  35.     virtual int setDelay(int32_t handle, int64_t ns);  
  36.     virtual int enable(int32_t handle, int enabled) = 0;  
  37. };  
class SensorBase {
protected:
    const char* dev_name; // "/dev/mma8452_daemon"
    const char* data_name; // "gsensor"
    int         dev_fd; // 打开设备"/dev/mma8452_daemon"的fd
    
    // 打开事件"/dev/input/eventx"的fd,其驱动的名字为"gsensor"
    int         data_fd; 
    
    // 打开与"gsensor"对应的事件"/dev/input/eventx"
    static int openInput(const char* inputName); 

    //通过clock_gettime获取当前时间
    static int64_t getTimestamp(); 


    static int64_t timevalToNano(timeval const& t) {
        return t.tv_sec*1000000000LL + t.tv_usec*1000;
    }

    int open_device(); //打开设备"dev/mma8452_daemon"
    int close_device(); //关闭设备"dev/mma8452_daemon"

public:
    // 调用openInput
            SensorBase(
                    const char* dev_name,
                    const char* data_name);

    virtual ~SensorBase();

    virtual int readEvents(sensors_event_t* data, int count) = 0;
    virtual bool hasPendingEvents() const;
    virtual int getFd() const;  //返回data_fd
    virtual int setDelay(int32_t handle, int64_t ns);
    virtual int enable(int32_t handle, int enabled) = 0;
};

2) MmaSensor的实现

[cpp] view plain copy print ?
  1. class MmaSensor : public SensorBase {  
  2. public:  
  3.     /* 
  4.       1) 设置dev_name为 "/dev/mma8452_daemon" 
  5.       2) 设置data_name为 "gsensor" 
  6.       3) open设备 "/dev/mma8452_daemon" 
  7.     */  
  8.             MmaSensor();  
  9.     virtual ~MmaSensor();  
  10.   
  11.     enum {  
  12.         Accelerometer   = 0,  
  13.         numSensors  
  14.     };  
  15.   
  16.     // 调用ioctl(MMA_IOCTL_APP_SET_RATE)   
  17.     virtual int setDelay(int32_t handle, int64_t ns);  
  18.   
  19.     /* 
  20.       1) Activate: ioctl(MMA_IOCTL_START) 
  21.       2) Deactivate: ioctl(MMA_IOCTL_CLOSE) 
  22.     */  
  23.     virtual int enable(int32_t handle, int enabled);  
  24.       
  25.     /* 
  26.       1) 从data_fd read input_event 
  27.       2) 调用processEvent对事件进行处理 
  28.       3) 把事件通过data返回 
  29.     */  
  30.     virtual int readEvents(sensors_event_t* data, int count);  
  31.   
  32.     void processEvent(int code, int value);  
  33.   
  34. private:  
  35.     int update_delay();  
  36.     uint32_t mEnabled;  
  37.     uint32_t mPendingMask;  
  38.     InputEventCircularReader mInputReader;  
  39.     sensors_event_t mPendingEvents[numSensors];  
  40.     uint64_t mDelays[numSensors];  
  41. };  
class MmaSensor : public SensorBase {
public:
    /*
      1) 设置dev_name为 "/dev/mma8452_daemon"
      2) 设置data_name为 "gsensor"
      3) open设备 "/dev/mma8452_daemon"
    */
            MmaSensor();
    virtual ~MmaSensor();

    enum {
        Accelerometer   = 0,
        numSensors
    };

    // 调用ioctl(MMA_IOCTL_APP_SET_RATE)
    virtual int setDelay(int32_t handle, int64_t ns);

    /*
      1) Activate: ioctl(MMA_IOCTL_START)
      2) Deactivate: ioctl(MMA_IOCTL_CLOSE)
    */
    virtual int enable(int32_t handle, int enabled);
    
    /*
      1) 从data_fd read input_event
      2) 调用processEvent对事件进行处理
      3) 把事件通过data返回
    */
    virtual int readEvents(sensors_event_t* data, int count);

    void processEvent(int code, int value);

private:
    int update_delay();
    uint32_t mEnabled;
    uint32_t mPendingMask;
    InputEventCircularReader mInputReader;
    sensors_event_t mPendingEvents[numSensors];
    uint64_t mDelays[numSensors];
};


3. 加载HAL

HAL 为一个.so库,其加载过程相关代码如下:

[cpp] view plain copy print ?
  1. #define HAL_LIBRARY_PATH1 "/system/lib/hw"   
  2. #define HAL_LIBRARY_PATH2 "/vendor/lib/hw"   
  3. #define SENSORS_HARDWARE_MODULE_ID "sensors"   
  4.   
  5. SensorDevice::SensorDevice()  
  6.     :  mSensorDevice(0),  
  7.        mSensorModule(0)  
  8. {  
  9.     status_t err = hw_get_module(SENSORS_HARDWARE_MODULE_ID,  
  10.             (hw_module_t const**)&mSensorModule);  
  11.   
  12.     ALOGE_IF(err, "couldn't load %s module (%s)",  
  13.             SENSORS_HARDWARE_MODULE_ID, strerror(-err));  
  14.   
  15.     if (mSensorModule) {  
  16.         err = sensors_open(&mSensorModule->common, &mSensorDevice);  
  17.   
  18.         ALOGE_IF(err, "couldn't open device for module %s (%s)",  
  19.                 SENSORS_HARDWARE_MODULE_ID, strerror(-err));  
  20.   
  21.         if (mSensorDevice) {  
  22.             sensor_t const* list;  
  23.             ssize_t count = mSensorModule->get_sensors_list(mSensorModule, &list);  
  24.             mActivationCount.setCapacity(count);  
  25.             Info model;  
  26.             for (size_t i=0 ; i<size_t(count) ; i++) {  
  27.                 mActivationCount.add(list[i].handle, model);  
  28.                 mSensorDevice->activate(mSensorDevice, list[i].handle, 0);  
  29.             }  
  30.         }  
  31.     }  
  32. }  
  33.   
  34. int hw_get_module(const char *id, const struct hw_module_t **module)  
  35. {  
  36.     return hw_get_module_by_class(id, NULL, module);  
  37. }  
  38.   
  39.   
  40. int hw_get_module_by_class(const char *class_id, const char *inst,  
  41.                            const struct hw_module_t **module)  
  42. {  
  43.     int status;  
  44.     int i;  
  45.     const struct hw_module_t *hmi = NULL;  
  46.     char prop[PATH_MAX];  
  47.     char path[PATH_MAX];  
  48.     char name[PATH_MAX];  
  49.   
  50.     if (inst)  
  51.         snprintf(name, PATH_MAX, "%s.%s", class_id, inst);  
  52.     else  
  53.         strlcpy(name, class_id, PATH_MAX);  
  54.   
  55.     /* 
  56.      * Here we rely on the fact that calling dlopen multiple times on 
  57.      * the same .so will simply increment a refcount (and not load 
  58.      * a new copy of the library). 
  59.      * We also assume that dlopen() is thread-safe. 
  60.      */  
  61.   
  62.     /* Loop through the configuration variants looking for a module */  
  63.     for (i=0 ; i
  64.         if (i < HAL_VARIANT_KEYS_COUNT) {  
  65.             if (property_get(variant_keys[i], prop, NULL) == 0) {  
  66.                 continue;  
  67.             }  
  68.             snprintf(path, sizeof(path), "%s/%s.%s.so",  
  69.                      HAL_LIBRARY_PATH2, name, prop);  
  70.             if (access(path, R_OK) == 0) break;  
  71.   
  72.             snprintf(path, sizeof(path), "%s/%s.%s.so",  
  73.                      HAL_LIBRARY_PATH1, name, prop);  
  74.             if (access(path, R_OK) == 0) break;  
  75.         } else {  
  76.             snprintf(path, sizeof(path), "%s/%s.default.so",  
  77.                      HAL_LIBRARY_PATH1, name);  
  78.             if (access(path, R_OK) == 0) break;  
  79.         }  
  80.     }  
  81.   
  82.     status = -ENOENT;  
  83.     if (i < HAL_VARIANT_KEYS_COUNT+1) {  
  84.         /* load the module, if this fails, we're doomed, and we should not try 
  85.          * to load a different variant. */  
  86.         status = load(class_id, path, module);  
  87.     }  
  88.   
  89.     return status;  
  90. }  
#define HAL_LIBRARY_PATH1 "/system/lib/hw"
#define HAL_LIBRARY_PATH2 "/vendor/lib/hw"
#define SENSORS_HARDWARE_MODULE_ID "sensors"

SensorDevice::SensorDevice()
    :  mSensorDevice(0),
       mSensorModule(0)
{
    status_t err = hw_get_module(SENSORS_HARDWARE_MODULE_ID,
            (hw_module_t const**)&mSensorModule);

    ALOGE_IF(err, "couldn't load %s module (%s)",
            SENSORS_HARDWARE_MODULE_ID, strerror(-err));

    if (mSensorModule) {
        err = sensors_open(&mSensorModule->common, &mSensorDevice);

        ALOGE_IF(err, "couldn't open device for module %s (%s)",
                SENSORS_HARDWARE_MODULE_ID, strerror(-err));

        if (mSensorDevice) {
            sensor_t const* list;
            ssize_t count = mSensorModule->get_sensors_list(mSensorModule, &list);
            mActivationCount.setCapacity(count);
            Info model;
            for (size_t i=0 ; iactivate(mSensorDevice, list[i].handle, 0);
            }
        }
    }
}

int hw_get_module(const char *id, const struct hw_module_t **module)
{
    return hw_get_module_by_class(id, NULL, module);
}


int hw_get_module_by_class(const char *class_id, const char *inst,
                           const struct hw_module_t **module)
{
    int status;
    int i;
    const struct hw_module_t *hmi = NULL;
    char prop[PATH_MAX];
    char path[PATH_MAX];
    char name[PATH_MAX];

    if (inst)
        snprintf(name, PATH_MAX, "%s.%s", class_id, inst);
    else
        strlcpy(name, class_id, PATH_MAX);

    /*
     * Here we rely on the fact that calling dlopen multiple times on
     * the same .so will simply increment a refcount (and not load
     * a new copy of the library).
     * We also assume that dlopen() is thread-safe.
     */

    /* Loop through the configuration variants looking for a module */
    for (i=0 ; i

4. 启动SensorService

    SensorService在SystemServer中启动(system_init.cpp),其相关代码如下:

[cpp] view plain copy print ?
  1. extern "C" status_t system_init()  
  2. {  
  3.     ....  
  4.     property_get("system_init.startsensorservice", propBuf, "1");  
  5.     if (strcmp(propBuf, "1") == 0) {  
  6.         // Start the sensor service   
  7.         SensorService::instantiate();  
  8.     }  
  9.     ...  
  10.     return NO_ERROR;  
  11. }  
extern "C" status_t system_init()
{
    ....
    property_get("system_init.startsensorservice", propBuf, "1");
    if (strcmp(propBuf, "1") == 0) {
        // Start the sensor service
        SensorService::instantiate();
    }
    ...
    return NO_ERROR;
}

5. SensorManager注册Listener过程

[cpp] view plain copy print ?
  1. private SensorManager mSensorManager = (SensorManager) getSystemService(SENSOR_SERVICE);  
  2. registerListener(SensorManager.java)->  
  3.  registerListenerImpl (SystemSensorManager.java)->  
  4.   enableSensorLocked(SystemSensorManager.java)->  
  5.    sensors_enable_sensor(android_hardware_SensorManager.cpp)->  
  6.     SensorEventQueue::enableSensor(SensorEventQueue.cpp)->  
  7.      1>SensorService::SensorEventConnection::enableDisable(handle, true) (SensorService.cpp)->  
  8.          SensorService::enable(SensorService.cpp)->  
  9.            HardwareSensor::activate(SensorInterface.cpp)->  
  10.              SensorDevice::activate(SensorDevice.cpp)->  
  11.                sensors_poll_device_t::activate(HAL)  
  12.            
  13.      2>SensorService::SensorEventConnection::setEventRate(SensorService.cpp)->  
  14.        
private SensorManager mSensorManager = (SensorManager) getSystemService(SENSOR_SERVICE);
registerListener(SensorManager.java)->
 registerListenerImpl (SystemSensorManager.java)->
  enableSensorLocked(SystemSensorManager.java)->
   sensors_enable_sensor(android_hardware_SensorManager.cpp)->
    SensorEventQueue::enableSensor(SensorEventQueue.cpp)->
     1>SensorService::SensorEventConnection::enableDisable(handle, true) (SensorService.cpp)->
         SensorService::enable(SensorService.cpp)->
           HardwareSensor::activate(SensorInterface.cpp)->
             SensorDevice::activate(SensorDevice.cpp)->
               sensors_poll_device_t::activate(HAL)
         
     2>SensorService::SensorEventConnection::setEventRate(SensorService.cpp)->
     


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