Android按键灯流程分析

调用代码为：

alps\frameworks\base\services\java\com\Android\server\LightsService.java

使用方法：

private LightsService.Light mButtonLight;

mButtonLight = mLightsService.getLight(LightsService.LIGHT_ID_BUTTONS);

mButtonLight.setBrightness(screenBrightness);

mButtonLight.turnOff();

本地代码在：

alps\frameworks\base\services\jni\com_android_server_LightsService.cpp

接口关联使用：

static JNINativeMethod method_table[] = {

{ "init_native", "()I", (void*)init_native },

{ "finalize_native", "(I)V", (void*)finalize_native },

{ "setLight_native", "(IIIIIII)V", (void*)setLight_native },

};

int register_android_server_LightsService(JNIEnv *env)

{

return jniRegisterNativeMethods(env, "com/android/server/LightsService",

method_table, NELEM(method_table));

}

register_android_server_LightsService函数在alps\frameworks\base\services\jni\onload.cpp里面注册

本地c代码在：

alps\mediatek\hardware\liblights\lights.c里面open_lights里面

static int

set_light_buttons(struct light_device_t* dev,

struct light_state_t const* state)

{

int err = 0;

int on = is_lit(state);

pthread_mutex_lock(&g_lock);

g_buttons = on;

err = write_int(BUTTON_FILE, on?255:0);

pthread_mutex_unlock(&g_lock);

return err;

}

com_android_server_LightsService.cp里面使用 devices->lights[light]->set_light(devices->lights[light], &state);来调用真正的代码

如果有root机子，可以如下测试：

echo 0 > /sys/class/leds/button-backlight/brightness 关按键灯

echo 1 > /sys/class/leds/button-backlight/brightness 开按键灯

echo 0 > /sys/class/leds/button-backlight/brightness 执行的意思为：输出0，作为/sys/class/leds/button-backlight/brightness的输入传入。

如此便会打开brightness设备，并执行write将0带入执行。