Android中 LED 系统架构
Android中背光系统架构
分类: Adroid开发 Linux操作系统 嵌入式Linux驱动 2011-09-24 16:00 1650人阅读 评论(6) 收藏 举报 android struct frameworks jni notifications moduleMg Android中背光系统架构
Email:[email protected]
Blog:http://blog.csdn.net/yinwei520
Author:Yww
Time:2011-9-24
Update:
(转载请注明出处,谢谢)
不知不觉喜欢上了写Blog,这还是一种不错的休闲方式,所噶~~,会不会也害怕过周末呢?因为寂寞~~啥样儿的生活才让觉得舒适哦~单身好~哈哈。搞了两天,还是姚哥一语惊醒梦中人啊~忽略了Linux下的权限问题,让我纠结了好几个小时啊。首先说明一下,这次学习中让我学到的东西:
最主要的莫过于是了解了Android中jni编程,游荡整个Android源码,可以看到很多直接操作底层驱动接口,封装成so库,供Java调用的例子哦。
这次学习,也正是出于这样的想法,没想到这个设想高手们早就实现了哦,菜鸟现在也只能算是验证了。诶,菜鸟就是菜鸟,有虫子吃,就兴奋的不得了。
驱动架构略,这里只讨论jni接口的实现。
一、我的设想
其实设想很简单,找到背光驱动提供给上层的API接口,人家Android还不是一样需要一层一层的抽象(HAL、Framework),高手们考虑的东东很多,所以才一层层抽象封装,既然这样,咱菜鸟不就一根筋,有虫吃就是王道啊,我为什么不能直接将这个驱动接口封装成jni提供给Java呢?其实这想法很早就有了,只是到现在才验证,确实可以啊。其实Android中还是有N多这样的例子的。
背光驱动提供的接口是:/sys/class/leds/lcd-backlight/brightness。至于这个接口是怎么来的??那就要去看驱动结构了。驱动注册此接口的源码位于:
Kernel/driver/leds/led-class.c中。
这个文件只是实现了提供上层的接口,至于真正操作硬件的驱动程序,可以给出其源码路径为:(硬件操作其实就是脉宽调制(PWM)),mediatek\source\kernel\drivers\leds
二、设想验证
这里关键就是要清楚jni的接口实现规则咯,不过环境搭建也比较麻烦(ndk编译环境)。
环境搭建另外给出日志。
Jni接口的源码如下:
[cpp] view plain copy print ?- #include<unistd.h>
- #include<stdio.h>
- #include<stdlib.h>
- #include<fcntl.h>
- #include<sys/types.h>
- #include<sys/stat.h>
- //#include<dirent.h>
- //#include<jni.h>
- #include<string.h>
- #include<android/log.h>
- #include"com_yecon_CtlBL_CtlBLActivity.h"
- #defineLOG_TAG"ctlbl.c"
- #defineLOGI(...)__android_log_print(ANDROID_LOG_INFO,LOG_TAG,__VA_ARGS__)
- //#defineDEV_PATH"/sys/class/leds/lcd-backlight/brightness"
- //#defineDEV_PATH"/sys/devices/platform/leds-mt65xx/leds/lcd-backlight/brightness"
- /**
- *nativemethod
- */
- //JNIEXPORTjobjectArrayJNICALLJava_com_yecon_CtlBL_CtlBLActivity_ctlbl(JNIEnv*env,jobjectobj)
- JNIEXPORTjintJNICALLJava_com_yecon_CtlBL_CtlBLActivity_ctlbl(JNIEnv*env,jobjectobj)
- {
- intfd;
- interr;
- char*p;
- charctl[10]={"20"};
- LOGI("HELLO!\n");
- //__android_log_print("");
- //printf("callctlblfunctionsucc!\n");
- fd=open("/sys/class/leds/lcd-backlight/brightness",O_RDWR);
- if(fd<0)
- {
- //fprintf(stderr,"error:open%s\n",DEV_PATH);
- LOGI("error:open!\n");
- exit(1);
- }
- #if0
- err=read(fd,ctl,1);
- if(err!=1)
- {
- //fprintf(stderr,"error:write%d!\n",err);
- exit(1);
- }else{
- //printf("thedatais%s\n",ctl[0]);
- }
- #endif
- err=write(fd,ctl,2);
- //printf("%s\n",ctl);
- if(err!=2)
- {
- //fprintf(stderr,"error:write%d!\n",err);
- LOGI("error:write!\n");
- exit(1);
- }
- close(fd);
- return0;
- //return(*env)->NewStringUTF(env,"HellowwJNI!");
- }
上层Java调用的源码如下:(只是实现了一个Button,点击,有一个消息响应,将背光调到20)
[java] view plain copy print ?- packagecom.yecon.CtlBL;
- importandroid.app.Activity;
- importandroid.os.Bundle;
- importandroid.view.View;
- importandroid.view.View.OnClickListener;
- importandroid.widget.Button;
- importandroid.widget.TextView;
- //importcom.yecon.CtlBL.ctlbljni;
- publicclassCtlBLActivityextendsActivity{
- Buttonb=null;
- //ctl=newctlbljni();
- privateOnClickListenerclickListener=newOnClickListener(){
- @Override
- publicvoidonClick(Viewv){
- //TODOAuto-generatedmethodstub
- //ctl.ctlbl();
- ctlbl();
- }
- };
- /**Calledwhentheactivityisfirstcreated.*/
- @Override
- publicvoidonCreate(BundlesavedInstanceState){
- super.onCreate(savedInstanceState);
- setContentView(R.layout.main);
- b=(Button)this.findViewById(R.id.BtnCancel);
- b.setOnClickListener(clickListener);
- //TextViewtv=newTextView(this);
- //tv.setText(ctlbl());
- //setContentView(tv);
- }
- publicnativeintctlbl();//本地方法
- static{
- System.loadLibrary("ctlbl");//载入so库
- }
- }
看上去,没几行代码,so easy!!看看高手们的实现吧!!
三、Android中背光系统实现
以往,我经常都是从底层往上看,这次从上层往下找找吧,同样的眼睛,不一样的视角,会别有一番风景哦~~其实,美女也要应该这样欣赏。
玩玩Android机子,其实知道背光调节就是在“设置”中的那个seekBar,那我们就去setting中去找源码吧.其源码路径为:
packages\apps\Settings\src\com\android\settings\ BrightnessPreference.java
打开看看吧~宽衣解带是最让人兴奋的啊。你会看到这样几行注释:
// Backlight range is from 0 - 255. Need to make sure that user
// doesn't set the backlight to 0 and get stuck
private static final intMINIMUM_BACKLIGHT = android.os.Power.BRIGHTNESS_DIM + 10;
private static final int MAXIMUM_BACKLIGHT = android.os.Power.BRIGHTNESS_ON;
背光的调节范围是0-255啊~~
继续解带吧~会看到一个很亲切的函数:
public void UpdateBrightness()
{
if(mIsActive)
{
setBrightness(mSeekBar.getProgress() +MINIMUM_BACKLIGHT);
}
}
更新背光亮度,太亲切了,这不慢慢接近目标了吗?其调用了setBrightness()函数,跳进去看看其实现哦~~
private void setBrightness(int brightness) {
try {
IPowerManager power = IPowerManager.Stub.asInterface(
ServiceManager.getService("power"));
if (power !=null) {
power.setBacklightBrightness(brightness);
}
} catch (RemoteException doe) {
}
}
这不就是韩哥给出的那几行代码嘛~~呵呵~终于找到要点了吧,所谓打蛇要打七寸,不就是这样吗?这个IPowerManager类中有个setBacklightBrightness函数啊,那它又是怎么实现的啊?找来找去只找到了一个申明啊:
public void setBacklightBrightness(int brightness)throws android.os.RemoteException;
找不到其实现怎么办呢??这是个棘手的问题啊~还好Eclipse很恶心啊~~搜搜就又出来了,这个函数的实现在:
frameworks\base\services\java\com\android\server\PowerManagerService.java中。
[java] view plain copy print ?- publicvoidsetBacklightBrightness(intbrightness){
- mContext.enforceCallingOrSelfPermission(android.Manifest.permission.DEVICE_POWER,null);
- //Don'tletapplicationsturnthescreenallthewayoff
- synchronized(mLocks){
- brightness=Math.max(brightness,Power.BRIGHTNESS_DIM);
- mLcdLight.setBrightness(brightness);
- //Wewon'tadjustButton/KeyboardBKLhereforthetimebeing,seeCR[ALPS00132847]
- //mKeyboardLight.setBrightness(mKeyboardVisible?brightness:0);
- //mButtonLight.setBrightness(brightness);
- longidentity=Binder.clearCallingIdentity();
- try{
- mBatteryStats.noteScreenBrightness(brightness);
- }catch(RemoteExceptione){
- Slog.w(TAG,"RemoteExceptioncallingnoteScreenBrightnessonBatteryStatsService",e);
- }finally{
- Binder.restoreCallingIdentity(identity);
- }
- //updateouranimationstate
- synchronized(mLocks){
- mScreenBrightness.targetValue=brightness;
- mScreenBrightness.jumpToTargetLocked();
- }
- }
- }
看着看着又模糊啦,这里怎么又调用了setBrightness()哦,此setBrightness非BrightnessPreference.java中的setBrightness。其类属于:
private LightsService.Light mLcdLight;
革命尚未成功,你说咋办,那好吧,为了革命的胜利,再进去看看这个类中setBrightness()的实现吧。源码路径为:
frameworks\base\services\java\com\android\server\LightsService.java
[java] view plain copy print ?- publicvoidsetBrightness(intbrightness){
- setBrightness(brightness,BRIGHTNESS_MODE_USER);
- }
- publicvoidsetBrightness(intbrightness,intbrightnessMode){
- synchronized(this){
- intcolor=brightness&0x000000ff;
- color=0xff000000|(color<<16)|(color<<8)|color;
- setLightLocked(color,LIGHT_FLASH_NONE,0,0,brightnessMode);
- }
- }
这里又调用了setLightLocked()
[java] view plain copy print ?- privatevoidsetLightLocked(intcolor,intmode,intonMS,intoffMS,intbrightnessMode){
- 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);
- }
- }
革命的曙光来啦,看到没,这里调用了setLight_native这个本地接口,
private static native void setLight_native(int ptr,int light,int color,int mode,
int onMS,int offMS,int brightnessMode);
皇天不负有心人啊,胜利的曙光照耀着我们啊,终于就快脱光光啦~~!难以按捺住这颗激动的心啊。
可是这个setLight_native又是在哪里呢??经过一番苦苦搜索,它并不在灯火阑珊处,而是在:
frameworks\base\services\jni\ com_android_server_LightsService.cpp
宽衣,看看:
四、JNI层
[cpp] view plain copy print ?- staticvoidsetLight_native(JNIEnv*env,jobjectclazz,intptr,
- intlight,intcolorARGB,intflashMode,intonMS,intoffMS,intbrightnessMode)
- {
- Devices*devices=(Devices*)ptr;
- light_state_tstate;
- 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;
- devices->lights[light]->set_light(devices->lights[light],&state);
- }
- staticJNINativeMethodmethod_table[]={
- {"init_native","()I",(void*)init_native},
- {"finalize_native","(I)V",(void*)finalize_native},
- {"setLight_native","(IIIIIII)V",(void*)setLight_native},
- };
哇,高手就是高手啊。看看,一个函数人家处理的不只是backlight,还有flash,color哦。惭愧啊~
到此,一个美女就这样被你看完啦~~当然,还有三点哦~~还想要激情的吗??激情就在底层了哦。想单刀直入吗?那还得看你本事了哦~~
devices->lights[light]->set_light(devices->lights[light], &state);
这句将带你穿梭进赤裸裸的XX。
五、HAL层
太神奇啦,这里直接给出HAL层的源码路劲,如下:
\mediatek\source\hardware\liblights\ lights.c
\hardware\libhardware\include\hardware\ lights.h
你会看到引你越过道德边缘的set_light的申明就在lights.h中啊。真是罪孽啊~~
[cpp] view plain copy print ?- /**
- *modulemethods
- */
- /**Openanewinstanceofalightsdeviceusingname*/
- staticintopen_lights(conststructhw_module_t*module,charconst*name,
- structhw_device_t**device)
- {
- int(*set_light)(structlight_device_t*dev,
- structlight_state_tconst*state);
- if(0==strcmp(LIGHT_ID_BACKLIGHT,name)){
- set_light=set_light_backlight;
- }
- elseif(0==strcmp(LIGHT_ID_KEYBOARD,name)){
- set_light=set_light_keyboard;
- }
- elseif(0==strcmp(LIGHT_ID_BUTTONS,name)){
- set_light=set_light_buttons;
- }
- elseif(0==strcmp(LIGHT_ID_BATTERY,name)){
- set_light=set_light_battery;
- }
- elseif(0==strcmp(LIGHT_ID_NOTIFICATIONS,name)){
- set_light=set_light_notifications;
- }
- elseif(0==strcmp(LIGHT_ID_ATTENTION,name)){
- set_light=set_light_attention;
- }
- else{
- return-EINVAL;
- }
- pthread_once(&g_init,init_globals);
- structlight_device_t*dev=malloc(sizeof(structlight_device_t));
- memset(dev,0,sizeof(*dev));
- dev->common.tag=HARDWARE_DEVICE_TAG;
- dev->common.version=0;
- dev->common.module=(structhw_module_t*)module;
- dev->common.close=(int(*)(structhw_device_t*))close_lights;
- dev->set_light=set_light;
- *device=(structhw_device_t*)dev;
- return0;
- }
看看吧,其实我们需要找的就是set_light_backlight。
[html] view plain copy print ?- staticint
- set_light_backlight(structlight_device_t*dev,
- structlight_state_tconst*state)
- {
- interr=0;
- intbrightness=rgb_to_brightness(state);
- pthread_mutex_lock(&g_lock);
- LOGD("%s:brightness=%dstart+++\n",__func__,brightness);
- g_backlight=brightness;
- err=write_int(LCD_FILE,brightness);
- if(g_haveTrackballLight){
- handle_trackball_light_locked(dev);
- }
- pthread_mutex_unlock(&g_lock);
- returnerr;
- }
当你认真看完lights.c会发现其基本思想跟之前的设想一样,只是人家是高手,我是菜鸟,人家看到赤裸裸的美女不是表面,而是艺术~~~~!!
通过这个分析,可以延伸了解到led灯的结构。
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