Android 8.0 SurfaceFlinger

一、SurfaceFlinger编译模块组成

码路径：frameworks/native/services/surfaceflinger

SurfaceFlinger二进制分成surfaceflinger（main入口）可执行文件和libsurfaceflinger.so库文件。surfaceflinger文件有main_surfaceflinger.cpp文件编译而成，为模块入口，真正实现在so文件中。

Android.mk代码模块编译配置如下：

surfaceflinger

LOCAL_SRC_FILES := \  main_surfaceflinger.cpp  ....  
LOCAL_MODULE := surfaceflinger  

libsurfaceflinger.so

LOCAL_SRC_FILES := \  Client.cpp \  ...  LayerRejecter.cpp \  ...  RenderEngine/GLES20RenderEngine.cpp \  LOCAL_MODULE := libsurfaceflinger  
...  
ifeq ($(TARGET_USES_HWC2),true)  LOCAL_CFLAGS += -DUSE_HWC2  LOCAL_SRC_FILES += \  SurfaceFlinger.cpp \  DisplayHardware/HWComposer.cpp  
else  LOCAL_SRC_FILES += \  SurfaceFlinger_hwc1.cpp \  DisplayHardware/HWComposer_hwc1.cpp  
endif  

ASFDSFADF
二、SurfaceFlinger可执行二进制文件surfaceflinger

surfaceflinger可执行文件由main_surfaceflinger.cpp  文件独立编译而成，主要负责搭建进程启动环境。直接上代码：

int main(int, char**) {

    // 从8.0开始，Android提供了hidl机制，将原先直接由JNI->Native->HAL的接口调用形式，统一规范成hidl service/client交互形式。该方式从一方面规范和统一了Android Framework和HAL的调用机制，但实际上，从项目维度，这种调用方式对性能上开销，将比直接调用的方式要花费更多的时间。startHidlServices();signal(SIGPIPE, SIG_IGN);// When SF is launched in its own process, limit the number of// binder threads to 4.ProcessState::self()->setThreadPoolMaxThreadCount(4);// start the thread poolsp<ProcessState> ps(ProcessState::self());ps->startThreadPool();

    // 初始化SurfaceFlinger对象，由强指针指向。SurfaceFlinger继承RefBase类，所以此处一旦new出对象赋给sp指针后，将立刻出发SurfaceFlinger类的onFirstRef方法的调用。// instantiate surfaceflingersp<SurfaceFlinger> flinger = new SurfaceFlinger();setpriority(PRIO_PROCESS, 0, PRIORITY_URGENT_DISPLAY);set_sched_policy(0, SP_FOREGROUND);// Put most SurfaceFlinger threads in the system-background cpuset// Keeps us from unnecessarily using big cores// Do this after the binder thread pool initif (cpusets_enabled()) set_cpuset_policy(0, SP_SYSTEM);

    // SurfaceFlinger类正式初始化// initialize before clients can connectflinger->init();

    // SurfaceFlinger向ServiceManager注册Binder服务，这样在其他进程中，可以通过getService+SERVICE_NAME来获取SurfaceFlinger服务，继而可以和SurfaceFlinger类进行Binder通信。// publish surface flingersp<IServiceManager> sm(defaultServiceManager());sm->addService(String16(SurfaceFlinger::getServiceName()), flinger, false);// publish GpuServicesp<GpuService> gpuservice = new GpuService();sm->addService(String16(GpuService::SERVICE_NAME), gpuservice, false);struct sched_param param = {0};param.sched_priority = 2;if (sched_setscheduler(0, SCHED_FIFO, ¶m) != 0) {ALOGE("Couldn't set SCHED_FIFO");}

    // SurfaceFlinger类进入主循环（此处注意SurfaceFlinger类未继承Threads类，不遵循Threads类的接口执行顺序）// run surface flinger in this threadflinger->run();return 0;
}

三、SurfaceFlinger库文件libsurfaceflinger.so