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android qcom Lights框架以及开发外部应用调用思路

程序员文章站 2022-07-01 20:18:49
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    近期项目开发中遇到需要增加手电筒控制的接口(不访问camera)。此类问题实际上实现起来非常简单。本着学习的精神以及不愿意简陋的实现该功能，因此把Lights框架查看了一遍，并增加新灯的控制方式。

先从调用处开始查看：

frameworks/base/services/core/java/com/android/server/BatteryService.java


//调用处，获取LightsManager的操作句柄
mLed = new Led(context, getLocalService(LightsManager.class));

private final class Led {
        private final Light mBatteryLight;
         
        …………………………………………//省略无关代码
 
        public Led(Context context, LightsManager lights) {
            //获取灯光操作句柄的方法
            mBatteryLight = lights.getLight(LightsManager.LIGHT_ID_BATTERY);
            ……………………………………//省略无关代码
            mBatteryLight.setFlashing(mBatteryLowARGB, Light.LIGHT_FLASH_TIMED,mBatteryLedOn, mBatteryLedOff);//红灯闪
            mBatteryLight.setColor(mBatteryFullARGB);//绿灯亮
            mBatteryLight.turnOff();//充电灯关
        }
}

注意此处代码获取LightsManager类为getlocalService方式，而非ServiceManager.getService的方式获取。因此无法用进程间通信。这里给应用开发人员出了难题。我们此次会将这个问题处理使得应用开发人员可以操作到LightsManager的句柄。

继续分析代码

frameworks/base/services/core/java/com/android/server/lights/LightsManager.java

public abstract class LightsManager {
    public static final int LIGHT_ID_BACKLIGHT = 0;//背光灯
    public static final int LIGHT_ID_KEYBOARD = 1;//键盘灯
    public static final int LIGHT_ID_BUTTONS = 2;//Home Menu,Back键灯
    public static final int LIGHT_ID_BATTERY = 3;  //充电灯
    public static final int LIGHT_ID_NOTIFICATIONS = 4;//通知灯
    public static final int LIGHT_ID_ATTENTION = 5;   //重要灯
    public static final int LIGHT_ID_BLUETOOTH = 6;//蓝牙
    public static final int LIGHT_ID_WIFI = 7;//WIFI灯
    public static final int LIGHT_ID_TORCH = 8;//新增手电筒灯
    public static final int LIGHT_ID_COUNT = 9;//修改原来个数为8
 
    public abstract Light getLight(int id);
}

分析代码可得，LightsManager实际仅仅只是通过ID号获取对应灯光句柄。因此。我们这里新添加手电筒类型，并且将计数值增加1.我们再来看看灯光句柄的代码

frameworks/base/services/core/java/com/android/server/lights/Light.java


public abstract class Light {
    public static final int LIGHT_FLASH_NONE = 0;
    public static final int LIGHT_FLASH_TIMED = 1;
    public static final int LIGHT_FLASH_HARDWARE = 2;
 
    /**
     * Light brightness is managed by a user setting.
     */
    public static final int BRIGHTNESS_MODE_USER = 0;
 
    /**
     * Light brightness is managed by a light sensor.
     */
    public static final int BRIGHTNESS_MODE_SENSOR = 1;
 
    public abstract void setBrightness(int brightness);
    public abstract void setBrightness(int brightness, int brightnessMode);
    public abstract void setColor(int color);
    public abstract void setFlashing(int color, int mode, int onMS, int offMS);
    public abstract void pulse();
    public abstract void pulse(int color, int onMS);
    public abstract void turnOff();
}

是一个抽象类。这两个文件的具体实现都在

frameworks/base/services/core/java/com/android/server/lights/LightsService.java

public class LightsService extends SystemService { 

        ……………………//省略
        //灯光操作句柄实现处
       private final class LightImpl extends Light {

        private LightImpl(int id) {
            mId = id;
        }

        @Override
        public void setBrightness(int brightness) {
            setBrightness(brightness, BRIGHTNESS_MODE_USER);
        }

        @Override
        public void setBrightness(int brightness, int brightnessMode) {
            synchronized (this) {
                int color = brightness & 0x000000ff;
                color = 0xff000000 | (color << 16) | (color << 8) | color;
                //最终这个函数也会调用到一个jni方法setLight_native
                setLightLocked(color, LIGHT_FLASH_NONE, 0, 0, brightnessMode);
            }
        }
        ……………………//省略
    }
    …………………………//省略
    @Override
    public void onStart() {
        ……………………//省略
        //此行代码表明为本地服务。app无法直接调用。
        publishLocalService(LightsManager.class, mService);
    }   

    //LightsManager具体实现主要作用就是获取对应id的灯光句柄
    private final LightsManager mService = new LightsManager() {
        @Override
        public com.android.server.lights.Light getLight(int id) {
            if (id < LIGHT_ID_COUNT) {
                return mLights[id];
            } else {
                return null;
            }   
        }   
    };  
    ……………………………………//省略
    public LightsService(Context context) {
        //构造函数中初始化走向一个jni方法
        mNativePointer = init_native();  
    }
}

我们来看两个关键jni方法

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


enum {
    LIGHT_INDEX_BACKLIGHT = 0,
    LIGHT_INDEX_KEYBOARD = 1,
    LIGHT_INDEX_BUTTONS = 2,
    LIGHT_INDEX_BATTERY = 3,
    LIGHT_INDEX_NOTIFICATIONS = 4,
    LIGHT_INDEX_ATTENTION = 5,
    LIGHT_INDEX_BLUETOOTH = 6,
    LIGHT_INDEX_WIFI = 7,
    LIGHT_INDEX_TORCH = 8, //新增索引
    LIGHT_COUNT
};


static jlong init_native(JNIEnv *env, jobject clazz)
{                                                                                          
    int err;
    hw_module_t* module;
    Devices* devices;
        
    devices = (Devices*)malloc(sizeof(Devices));

    err = hw_get_module(LIGHTS_HARDWARE_MODULE_ID, (hw_module_t const**)&module);
    if (err == 0) {
        devices->lights[LIGHT_INDEX_BACKLIGHT]
                = get_device(module, LIGHT_ID_BACKLIGHT);
        devices->lights[LIGHT_INDEX_KEYBOARD]
                = get_device(module, LIGHT_ID_KEYBOARD);
        devices->lights[LIGHT_INDEX_BUTTONS]
                = get_device(module, LIGHT_ID_BUTTONS);
        devices->lights[LIGHT_INDEX_BATTERY]
                = get_device(module, LIGHT_ID_BATTERY);
        devices->lights[LIGHT_INDEX_NOTIFICATIONS]
                = get_device(module, LIGHT_ID_NOTIFICATIONS);
        devices->lights[LIGHT_INDEX_ATTENTION]
                = get_device(module, LIGHT_ID_ATTENTION);
        devices->lights[LIGHT_INDEX_BLUETOOTH]
                = get_device(module, LIGHT_ID_BLUETOOTH);
        devices->lights[LIGHT_INDEX_WIFI]
                = get_device(module, LIGHT_ID_WIFI);
        //新增手电筒索引LIGHT_INDEX_TORCH以及
        //手电筒对象名称LIGHT_ID_TORCH 在头文件lights.h中定义.
        //get_deivce实现的就是名称匹配获取hw对象，
        //此处不再赘述，熟悉hw中间层的应该了解。可以仔细看源码。
        devices->lights[LIGHT_INDEX_TORCH] 
                = get_device(module, LIGHT_ID_TORCH);
    } else {
        memset(devices, 0, sizeof(Devices));
    }

    return (jlong)devices;
}

static void setLight_native(JNIEnv *env, jobject clazz, jlong ptr,
        jint light, jint colorARGB, jint flashMode, jint onMS, jint offMS, jint brightnessM
ode)
{
    Devices* devices = (Devices*)ptr;
    light_state_t state;

    if (light < 0 || light >= LIGHT_COUNT || devices->lights[light] == NULL) {
        return ;
    }

    memset(&state, 0, sizeof(light_state_t));
    state.color = colorARGB;
    state.flashMode = flashMode;
    state.flashOnMS = onMS;
    state.flashOffMS = offMS;
    state.brightnessMode = brightnessMode;

    {
        ALOGD_IF_SLOW(50, "Excessive delay setting light");
        devices->lights[light]->set_light(devices->lights[light], &state);//最终调用hw中间层的set_light函数指针所指向的方法。
    }
}

新增内容以及关键点已在代码中注释，现转到hardware层

hardware/qcom/display/liblight/lights.c

//上个代码get_device所对应调用函数
static int open_lights(const struct hw_module_t* module, char const* name,                 
        struct hw_device_t** device)
{
    int (*set_light)(struct light_device_t* dev,
            struct light_state_t const* state);

    if (0 == strcmp(LIGHT_ID_BACKLIGHT, name))
        …………………………//省略
    else if (0 == strcmp(LIGHT_ID_TORCH, name)) 
        //上个代码中get_device传入的名字以手电筒为例匹配对应然后将对应set_light操作赋值
        set_light = set_light_torch;        
    else
        return -EINVAL;

    …………………………//省略

    struct light_device_t *dev = malloc(sizeof(struct light_device_t));

    …………………………//省略
    dev->set_light = set_light;//将对应的set_light赋予Devi设备的操作。

    *device = (struct hw_device_t*)dev;
    return 0;
}


//上个代码set_light最终调用函数以手电筒为例
static int
set_light_torch(struct light_device_t* dev,                                                
        struct light_state_t const* state)
{
    int err = 0;
    int brightness = rgb_to_brightness(state);
    if(!dev) {
        return -1;
    }
    pthread_mutex_lock(&g_lock);
    //TORCH_FILE为新增
    //char const*const TORCH_FILE ="/sys/class/leds/torch-light0/brightness"
    //实际上最终也是写文件实现灯的亮灭。
    err = write_int(TORCH_FILE, brightness);
    pthread_mutex_unlock(&g_lock);
    return err;
}

分析整个框架。基本上新灯添加完毕，原生框架代码也很清晰，只是因为是localservice。外部无法调用只能systemservice自己玩。因此考虑包一层bindservice这样既不影响原来的localservice又能实现应用调用，这包一层的方法自然想到aidl。

interface IUserLightsManager { 
       void setLight(int light_id);
       void setBrightness(int brightness);
}

实现它！！盘它！！

//注意此处需要继承SystemService才能getLocalService
public class UserLightsManager extends SystemService {

       private final String Tag = "UserLightsManager";
       private Light mLight;
       private LightsManager mLightsManager;


       public void onStart() {
               //获得原生框架LightsManager句柄
               mLightsManager = getLocalService(LightsManager.class);
               //将mService实际上是aidl的实现作为bindservice。
               //此函数最终实现ServiceManager.addService类似。
               publishBinderService("UserLightsManager", mService); 
       }

       public UserLightsManager(Context context) {
               super(context);
       }
        //实现aidl 通过此aidl间接调用LightsManager
       private final IBinder mService = new IUserLightsManager.Stub() { 
               //light_id 
               //see frameworks/base/services/core/java/com/android/server/lights/LightsMa
               public void setLight(int light_id ) {
                       //mLightsManager = getLocalService(LightsManager.class);
                       //LightsManager.LIGHT_ID_xxxx
                       Log.d(Tag,"setLight");
                       mLight = mLightsManager.getLight(light_id);
                       Log.d(Tag,"setLight mLight" + mLight);

               }

               public void setBrightness(int brightness) {
                       Log.d(Tag,"setBrightness mLight" + mLight);
                       if(mLight != null) {
                               mLight.setBrightness(brightness);       
                       }
               }
       };
}

还需要将这个服务启动一下

frameworks/base/services/java/com/android/server/SystemServer.java

mSystemServiceManager.startService(UserLightsManager.class);

最后应用层调用方法

  IBinder b = ServiceManager.getService("UserLightsManager"); 
               if(b != null ) {
                       mIUserLightsManager = IUserLightsManager.Stub.asInterface(b);
               }

    mIUserLightsManager.setLight(8);
    mIUserLightsManager.setBrightness(255);

以上，如有不足之处欢迎来讨论优化

相关标签： qcom lights 灯光 android 框架

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