Lights System

一、Overall Architeture

二、Linux Driver Layer

三、Android HAL Layer

四、Hardware Interface

五、JNI Layer

六、Java Service

七、Java App

一、OverallArchiteture

Android lightssystem

二、LinuxDriver Layer

Linux DriverLayer 采用标准linux的LED框架，代码位于drivers/leds/，接口采用sys文件系统提供，分别为/sys/class/leds/[device]/brightness,/sys/class/leds/[device]/ max_brightness, /sys/class/leds/[device]/trigger.

三、AndroidHAL Layer

首先创建hw_module_t对象，对象名称唯一“HAL_MODULE_INFO_SYM”，

#define HAL_MODULE_INFO_SYMHMI

/**

* Name of the hal_module_info as a string

#defineHAL_MODULE_INFO_SYM_AS_STR"HMI"

conststruct hw_module_t HAL_MODULE_INFO_SYM = {

.tag = HARDWARE_MODULE_TAG,

.version_major = 1,

.version_minor = 0,

.id = LIGHTS_HARDWARE_MODULE_ID,

.name = "QCT MSM7K lightsModule",

.author = "Google, Inc.",

.methods = &lights_module_methods,

};

然后实现hw_module_methods_t方法，返回hw_device_t对象指针：

staticstruct hw_module_methods_t lights_module_methods = {

.open =open_lights,

};

static intopen_lights(const struct hw_module_t* module, char const* name,

struct hw_device_t** device)

{

&&&&&&&&&&&&&&&&

*device =(struct hw_device_t*)dev;

&&&&&&&&&&&&&&&&

}

四、HardwareInterface

JNI call hw_get_module fuction,returnhw_device_t object.

五、JNILayer

JNI code 在frameworks/base/services/jni/com_android_server_LightsService.cpp

首先实现标准接口函数int register_android_server_LightsService(JNIEnv*env)；这个函数调用JNI 函数jniRegisterNativeMethods（在onload.cpp）实现C/C++函数和JAVA对应关系.最后由JAVA程序调用JNI_OnLoad。见下图：

六、JavaService

Service layer 其实就是一个JAVA类，其中声明为本地的函数，这些函数通过JNI最后调用底层设备。

public class LightsService {

private staticnative int init_native();

private static native void finalize_native(int ptr);

private static native void setLight_native(int ptr, int light, intcolor, int mode,

int onMS, int offMS, int brightnessMode);

}

构造函数：

LightsService(Context context) {

mNativePointer = init_native();

mContext = context;

ServiceManager.addService("hardware", mLegacyFlashlightHack);

for (int i = 0; i < LIGHT_ID_COUNT; i++) {

mLights[i] = new Light(i);

}

析构函数：

protected void finalize() throws Throwable {

finalize_native(mNativePointer);

super.finalize();

}

private void setLightLocked(int color, intmode, int onMS, int offMS, int brightnessMode) {

if (color != mColor || mode != mMode || onMS != mOnMS || offMS !=mOffMS) {

mColor = color;

mMode = mode;

mOnMS = onMS;

mOffMS = offMS;

setLight_native(mNativePointer,mId, color, mode, onMS, offMS, brightnessMode);

}

七、JavaApp

class PowerManagerService{

private LightsService.Light mLcdLight;

private LightsService.Light mButtonLight;

private LightsService.Light mKeyboardLight;

private LightsService.Light mAttentionLight;

}

private void setLightBrightness(int mask,int value) {

int brightnessMode = (mAutoBrightessEnabled

?LightsService.BRIGHTNESS_MODE_SENSOR

:LightsService.BRIGHTNESS_MODE_USER);

if ((mask & SCREEN_BRIGHT_BIT) != 0) {

mLcdLight.setBrightness(value, brightnessMode);

}

if ((mask & BUTTON_BRIGHT_BIT) != 0) {

mButtonLight.setBrightness(value);

}

if ((mask & KEYBOARD_BRIGHT_BIT) != 0) {

mKeyboardLight.setBrightness(value);

}

Android 光系统