Android4.2.2 SurfaceFlinger启动流程详解(二）

本文均属自己阅读源码的点滴总结，转账请注明出处谢谢。

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Android源码版本Version：4.2.2; 硬件平台 全志A31

 

接着上文的SF启动流程，这里单独拎出来分析SurfaceFlinger::readyToRun()函数。里面的知识点比较多，只能和大家分享自己所知道的，共同交流学习。

status_t SurfaceFlinger::readyToRun(){    ALOGI(  "SurfaceFlinger's main thread ready to run. "            "Initializing graphics H/W...");    // initialize EGL for the default display    mEGLDisplay = eglGetDisplay(EGL_DEFAULT_DISPLAY);    eglInitialize(mEGLDisplay, NULL, NULL);//EGL的初始化    // Initialize the H/W composer object.  There may or may not be an    // actual hardware composer underneath.    mHwc = new HWComposer(this,            *static_cast<HWComposer::EventHandler *>(this));//新建一个软硬件合成器HWComposer    // initialize the config and context    EGLint format = mHwc->getVisualID();    mEGLConfig  = selectEGLConfig(mEGLDisplay, format);//配置EGL的参数    mEGLContext = createGLContext(mEGLDisplay, mEGLConfig);//初始化上下文内容    LOG_ALWAYS_FATAL_IF(mEGLContext == EGL_NO_CONTEXT,            "couldn't create EGLContext");    // initialize our non-virtual displays    for (size_t i=0 ; i<DisplayDevice::NUM_DISPLAY_TYPES ; i++) {//DisplayDevice::NUM_DISPLAY_TYPES = 2        DisplayDevice::DisplayType type((DisplayDevice::DisplayType)i);//0:HWC_DISPLAY_PRIMARY,1:HWC_DISPLAY_EXTERNAL        mDefaultDisplays[i] = new BBinder();        wp<IBinder> token = mDefaultDisplays[i];        // set-up the displays that are already connected        if (mHwc->isConnected(i) || type==DisplayDevice::DISPLAY_PRIMARY) {            // All non-virtual displays are currently considered secure.            bool isSecure = mHwc->isSecure(i);            mCurrentState.displays.add(token, DisplayDeviceState(type));            sp<FramebufferSurface> fbs = new FramebufferSurface(*mHwc, i);            sp<SurfaceTextureClient> stc = new SurfaceTextureClient(                        static_cast< sp<ISurfaceTexture> >(fbs->getBufferQueue()));            sp<DisplayDevice> hw = new DisplayDevice(this,                    type, isSecure, token, stc, fbs, mEGLConfig);//新的显示设备            if (i > DisplayDevice::DISPLAY_PRIMARY) {//HDMI,i= 1                // FIXME: currently we don't get blank/unblank requests                // for displays other than the main display, so we always                // assume a connected display is unblanked.                ALOGD("marking display %d as acquired/unblanked", i);                hw->acquireScreen();            }            mDisplays.add(token, hw);//将准备好的显示硬件维护在mDefaultDisplays[i]中        }    }    //  we need a GL context current in a few places, when initializing    //  OpenGL ES (see below), or creating a layer,    //  or when a texture is (asynchronously) destroyed, and for that    //  we need a valid surface, so it's convenient to use the main display    //  for that.    sp<const DisplayDevice> hw(getDefaultDisplayDevice());    //  initialize OpenGL ES    DisplayDevice::makeCurrent(mEGLDisplay, hw, mEGLContext);    initializeGL(mEGLDisplay);    // start the EventThread    mEventThread = new EventThread(this);//新建一个事件线程用于创建event的消息，处理VSYC同步事件    mEventQueue.setEventThread(mEventThread);    // initialize our drawing state    mDrawingState = mCurrentState;    // We're now ready to accept clients...    mReadyToRunBarrier.open();    // set initial conditions (e.g. unblank default device)    initializeDisplays();    // start boot animation    startBootAnim();//开启动画属性    return NO_ERROR;}int32_t SurfaceFlinger::allocateHwcDisplayId(DisplayDevice::DisplayType type) {    return (uint32_t(type) < DisplayDevice::NUM_DISPLAY_TYPES) ?            type : mHwc->allocateDisplayId();}

在进入线程循环前，之所以执行他，因为SF正在运行前还有许多的工作要做，从下面几个点开始分析：

step1: new HWComposer()

在这里冒昧的称其为硬件合成器，从他的实现来看，可以看出他是和底层驱动走的最近的地方，因为涉及到了Gralloc模块（即所谓的Framebffer，主要用于图形的最终显示。

构造函数如下：

HWComposer::HWComposer(        const sp<SurfaceFlinger>& flinger,        EventHandler& handler)    : mFlinger(flinger),      mFbDev(0), mHwc(0), mNumDisplays(1),      mCBContext(new cb_context),      mEventHandler(handler),      mVSyncCount(0), mDebugForceFakeVSync(false){    for (size_t i =0 ; i<MAX_DISPLAYS ; i++) {        mLists[i] = 0;        mFrame[i].left = 0;        mFrame[i].top = 0;        mFrame[i].right = -1;        mFrame[i].bottom = -1;    }    char value[PROPERTY_VALUE_MAX];    property_get("debug.sf.no_hw_vsync", value, "0");    mDebugForceFakeVSync = atoi(value);    bool needVSyncThread = true;    // Note: some devices may insist that the FB HAL be opened before HWC.    loadFbHalModule();//加载framerbuffer模块gralloc    loadHwcModule();//加载HWComposer模块......{//如果支持硬件hw        ALOGI("Using %s version %u.%u", HWC_HARDWARE_COMPOSER,              (hwcApiVersion(mHwc) >> 24) & 0xff,              (hwcApiVersion(mHwc) >> 16) & 0xff);//1.1版本        if (mHwc->registerProcs) {            mCBContext->hwc = this;            mCBContext->procs.invalidate = &hook_invalidate;            mCBContext->procs.vsync = &hook_vsync;//相关hwc的回调函数初始化            if (hwcHasApiVersion(mHwc, HWC_DEVICE_API_VERSION_1_1))                mCBContext->procs.hotplug = &hook_hotplug;            else                mCBContext->procs.hotplug = NULL;            memset(mCBContext->procs.zero, 0, sizeof(mCBContext->procs.zero));            mHwc->registerProcs(mHwc, &mCBContext->procs);//向HAL注册回调函数        }        // don't need a vsync thread if we have a hardware composer        needVSyncThread = false;//有硬件合成器就不需要软件的Vsync同步        // always turn vsync off when we start        eventControl(HWC_DISPLAY_PRIMARY, HWC_EVENT_VSYNC, 0);        // the number of displays we actually have depends on the        // hw composer version        if (hwcHasApiVersion(mHwc, HWC_DEVICE_API_VERSION_1_2)) {            // 1.2 adds support for virtual displays            mNumDisplays = MAX_DISPLAYS;//1.2支持虚拟屏        } else if (hwcHasApiVersion(mHwc, HWC_DEVICE_API_VERSION_1_1)) {            // 1.1 adds support for multiple displays            mNumDisplays = HWC_NUM_DISPLAY_TYPES;//1.1支持2个屏        } else {            mNumDisplays = 1;        }    }}

两个重要的成员函数loadFbHalModule和loadHwcModule

void HWComposer::loadFbHalModule(){    hw_module_t const* module;    if (hw_get_module(GRALLOC_HARDWARE_MODULE_ID, &module) != 0) {//GRALLOC_HARDWARE_MODULE_ID = "Gralloc"        ALOGE("%s module not found", GRALLOC_HARDWARE_MODULE_ID);        return;    }    int err = framebuffer_open(module, &mFbDev);//gralloc内部的fb0模块    if (err) {        ALOGE("framebuffer_open failed (%s)", strerror(-err));        return;    }}

根据博文Android中的HAL相关库搜索机制和原理学习可知最终会获取对应的framebuffer和hardware composer模块。

另外通过mHwc->registerProcs(mHwc, &mCBContext->procs);//向HAL注册对应的回调函数，供底层事件的回调调用。

 

step2: 对显示屏的初始化

mDisplayData[HWC_DISPLAY_PRIMARY]维护主要的显示屏，由下面的枚举类型来负责

enum {    HWC_DISPLAY_PRIMARY     = 0,    HWC_DISPLAY_EXTERNAL    = 1,    // HDMI, DP, etc.    HWC_NUM_DISPLAY_TYPES};

显示屏的相关信息提取与维护有函数HWComposer::queryDisplayProperties来完成：

status_t HWComposer::queryDisplayProperties(int disp) {    LOG_ALWAYS_FATAL_IF(!mHwc || !hwcHasApiVersion(mHwc, HWC_DEVICE_API_VERSION_1_1));    // use zero as default value for unspecified attributes    int32_t values[NUM_DISPLAY_ATTRIBUTES - 1];    memset(values, 0, sizeof(values));    uint32_t config;    size_t numConfigs = 1;    status_t err = mHwc->getDisplayConfigs(mHwc, disp, &config, &numConfigs);//得到显示器的配置    if (err != NO_ERROR) {        // this can happen if an unpluggable display is not connected        mDisplayData[disp].connected = false;        return err;    }    err = mHwc->getDisplayAttributes(mHwc, disp, config, DISPLAY_ATTRIBUTES, values);//获取显示属性......}

 

step3:进一步初始化SF端需要的surface信息

  // initialize our non-virtual displays    for (size_t i=0 ; i<DisplayDevice::NUM_DISPLAY_TYPES ; i++) {//DisplayDevice::NUM_DISPLAY_TYPES = 2        DisplayDevice::DisplayType type((DisplayDevice::DisplayType)i);//0:HWC_DISPLAY_PRIMARY,1:HWC_DISPLAY_EXTERNAL        mDefaultDisplays[i] = new BBinder();        wp<IBinder> token = mDefaultDisplays[i];        // set-up the displays that are already connected        if (mHwc->isConnected(i) || type==DisplayDevice::DISPLAY_PRIMARY) {            // All non-virtual displays are currently considered secure.            bool isSecure = mHwc->isSecure(i);            mCurrentState.displays.add(token, DisplayDeviceState(type));            sp<FramebufferSurface> fbs = new FramebufferSurface(*mHwc, i);            sp<SurfaceTextureClient> stc = new SurfaceTextureClient(                        static_cast< sp<ISurfaceTexture> >(fbs->getBufferQueue()));            sp<DisplayDevice> hw = new DisplayDevice(this,                    type, isSecure, token, stc, fbs, mEGLConfig);//新的显示设备            if (i > DisplayDevice::DISPLAY_PRIMARY) {//HDMI,i= 1                // FIXME: currently we don't get blank/unblank requests                // for displays other than the main display, so we always                // assume a connected display is unblanked.                ALOGD("marking display %d as acquired/unblanked", i);                hw->acquireScreen();            }            mDisplays.add(token, hw);//将准备好的显示硬件维护在mDefaultDisplays[i]中        }    }

这里分别new了FramebufferSurface和SurfaceTextureClient，下面对其进行分析

FramebufferSurface::FramebufferSurface(HWComposer& hwc, int disp) :    ConsumerBase(new BufferQueue(true, new GraphicBufferAlloc())),    mDisplayType(disp),    mCurrentBufferSlot(-1),    mCurrentBuffer(0),    mHwc(hwc){    mName = "FramebufferSurface";    mBufferQueue->setConsumerName(mName);    mBufferQueue->setConsumerUsageBits(GRALLOC_USAGE_HW_FB |                                       GRALLOC_USAGE_HW_RENDER |                                       GRALLOC_USAGE_HW_COMPOSER);    mBufferQueue->setDefaultBufferFormat(mHwc.getFormat(disp));    mBufferQueue->setDefaultBufferSize(mHwc.getWidth(disp),  mHwc.getHeight(disp));    mBufferQueue->setSynchronousMode(true);    mBufferQueue->setDefaultMaxBufferCount(NUM_FRAMEBUFFER_SURFACE_BUFFERS);}

OK，这里又进入了FramebufferSurface的构造函数，该类继承ConsumerBase类，对该构造函数分为以下几个部分来分析。

a. new GraphicBufferAlloc()，新建一个图形缓存分配器类

b. new BufferQueue() 新建缓存队列类， 如下：

BufferQueue::BufferQueue(bool allowSynchronousMode,        const sp<IGraphicBufferAlloc>& allocator) {if (allocator == NULL) {        sp<ISurfaceComposer> composer(ComposerService::getComposerService());        mGraphicBufferAlloc = composer->createGraphicBufferAlloc();//创建GraphicBuffer        if (mGraphicBufferAlloc == 0) {            ST_LOGE("createGraphicBufferAlloc() failed in BufferQueue()");        }    } else {        mGraphicBufferAlloc = allocator;    }}

新建的图像缓存分配器保存在BufferQueue队列当中。

c. new ConsumerBase类

ConsumerBase::ConsumerBase(const sp<BufferQueue>& bufferQueue) :        mAbandoned(false),        mBufferQueue(bufferQueue) {    // Choose a name using the PID and a process-unique ID.    mName = String8::format("unnamed-%d-%d", getpid(), createProcessUniqueId());    // Note that we can't create an sp<...>(this) in a ctor that will not keep a    // reference once the ctor ends, as that would cause the refcount of 'this'    // dropping to 0 at the end of the ctor.  Since all we need is a wp<...>    // that's what we create.    wp<BufferQueue::ConsumerListener> listener;    sp<BufferQueue::ConsumerListener> proxy;    listener = static_cast<BufferQueue::ConsumerListener*>(this);    proxy = new BufferQueue::ProxyConsumerListener(listener);//新建一个监听代理    status_t err = mBufferQueue->consumerConnect(proxy);//创建一个ConsumerListener代理    if (err != NO_ERROR) {        CB_LOGE("SurfaceTexture: error connecting to BufferQueue: %s (%d)",                strerror(-err), err);    } else {        mBufferQueue->setConsumerName(mName);    }}

新建的ConsumerBase类，内部主要完成了创建一个BufferQueue的代理监听，同时将当前的mBufferQueue与监听连接在一起，具体如何使用后续会分析到。

status_t BufferQueue::consumerConnect(const sp<ConsumerListener>& consumerListener) {...    mConsumerListener = consumerListener;    return OK;}

 

step4,最终集成新建一个DisplayDevice

            sp<DisplayDevice> hw = new DisplayDevice(this,                    type, isSecure, token, stc, fbs, mEGLConfig);//新的显示设备

 

step5.在SurfaceFlinger内接下去的内容将会在后续进行进一步分析。