Surfaceflinger process流程分析

最新推荐文章于 2025-07-30 10:22:54 发布

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#buffer #layer #alignment #thread #filter #animation

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本文深入解析了SurfaceFlinger的工作原理，包括其初始化过程、线程循环机制、surface和layer的创建，以及如何处理上层命令并通过OpenGL进行图像合成。

根据前面的介绍，surfaceflinger作为一个server process（其进程入口见main_surfaceflinger.cpp中的main函数），上层的应用程序（作为client）通过Binder方式与其进行通信。Surfaceflinger作为一个进程，这里把它分为3个部分，如下：

1、 Thread本身处理部分，包括初始化以及thread loop。

2、 Binder部分，负责接收上层应用的各个设置和命令，并反馈状态标志给上层。

3、与底层的交互，负责调用底层接口（HAL）。

结构图如下：

注释：

a、 Binder接收到应用程序的命令（如创建surface、设置参数等），传递给flinger。

b、 Flinger完成对应命令后将相关结果状态反馈给上层。

c、在处理上层命令过程中，根据需要设置event（主要和显示有关），通知Thread Loop进行处理。

d、 Flinger根据上层命令通知底层进行处理（主要是设置一些参数，Layer、position等）

e、 Thread Loop中进行surface的合成并通知底层进行显示（Post buffer）。

f、 DisplayHardware层根据flinger命令调用HAL进行HW的操作。

下面来具体分析一些SurfaceFlinger中重要的处理函数以及surface、Layer的属性

1. SurfaceFlinger::readyToRun

SurfaceFlinger thread的初始化函数，主要任务是分配内存和设置底层接口(EGL&HAL)。

status_t SurfaceFlinger::readyToRun()
{
    LOGI(   "SurfaceFlinger's main thread ready to run. "
            "Initializing graphics H/W...");

    // we only support one display currently
    int dpy = 0;

    {
        // initialize the main display
        GraphicPlane& plane(graphicPlane(dpy));
        DisplayHardware* const hw = new DisplayHardware(this, dpy);
        plane.setDisplayHardware(hw);
    }

    // create the shared control-block
    mServerHeap = new MemoryHeapBase(4096,
            MemoryHeapBase::READ_ONLY, "SurfaceFlinger read-only heap");
    LOGE_IF(mServerHeap==0, "can't create shared memory dealer");

    mServerCblk = static_cast<surface_flinger_cblk_t*>(mServerHeap->getBase());
    LOGE_IF(mServerCblk==0, "can't get to shared control block's address");

    new(mServerCblk) surface_flinger_cblk_t;

    // initialize primary screen
    // (other display should be initialized in the same manner, but
    // asynchronously, as they could come and go. None of this is supported
    // yet).
    const GraphicPlane& plane(graphicPlane(dpy));
    const DisplayHardware& hw = plane.displayHardware();
    const uint32_t w = hw.getWidth();
    const uint32_t h = hw.getHeight();
    const uint32_t f = hw.getFormat();
    hw.makeCurrent();

    // initialize the shared control block
    mServerCblk->connected |= 1<<dpy;
    display_cblk_t* dcblk = mServerCblk->displays + dpy;
    memset(dcblk, 0, sizeof(display_cblk_t));
    dcblk->w            = plane.getWidth();
    dcblk->h            = plane.getHeight();
    dcblk->format       = f;
    dcblk->orientation  = ISurfaceComposer::eOrientationDefault;
    dcblk->xdpi         = hw.getDpiX();
    dcblk->ydpi         = hw.getDpiY();
    dcblk->fps          = hw.getRefreshRate();
    dcblk->density      = hw.getDensity();

    // Initialize OpenGL|ES
    glPixelStorei(GL_UNPACK_ALIGNMENT, 4);
    glPixelStorei(GL_PACK_ALIGNMENT, 4);
    glEnableClientState(GL_VERTEX_ARRAY);
    glEnable(GL_SCISSOR_TEST);
    glShadeModel(GL_FLAT);
    glDisable(GL_DITHER);
    glDisable(GL_CULL_FACE);

    const uint16_t g0 = pack565(0x0F,0x1F,0x0F);
    const uint16_t g1 = pack565(0x17,0x2f,0x17);
    const uint16_t wormholeTexData[4] = { g0, g1, g1, g0 };
    glGenTextures(1, &mWormholeTexName);
    glBindTexture(GL_TEXTURE_2D, mWormholeTexName);
    glTexParameterx(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
    glTexParameterx(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
    glTexParameterx(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
    glTexParameterx(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, 2, 2, 0,
            GL_RGB, GL_UNSIGNED_SHORT_5_6_5, wormholeTexData);

    const uint16_t protTexData[] = { pack565(0x03, 0x03, 0x03) };
    glGenTextures(1, &mProtectedTexName);
    glBindTexture(GL_TEXTURE_2D, mProtectedTexName);
    glTexParameterx(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
    glTexParameterx(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
    glTexParameterx(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
    glTexParameterx(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, 1, 1, 0,
            GL_RGB, GL_UNSIGNED_SHORT_5_6_5, protTexData);

    glViewport(0, 0, w, h);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    // put the origin in the left-bottom corner
    glOrthof(0, w, 0, h, 0, 1); // l=0, r=w ; b=0, t=h

    mReadyToRunBarrier.open();

    /*
     *  We're now ready to accept clients...
     */

    // start boot animation
    property_set("ctl.start", "bootanim");

    return NO_ERROR;
}

2. SurfaceFlinger::threadLoop

Surfaceflinger的loop函数，主要是等待其他接口发送的event，进行显示数据的合成以及显示。

bool SurfaceFlinger::threadLoop()
{
    waitForEvent();  //等待其他接口的signal event

    // post surfaces (if needed)
    handlePageFlip();   //处理翻页机制

    if (UNLIKELY(mHwWorkListDirty)) {
        // build the h/w work list
        handleWorkList();
    }

    const DisplayHardware& hw(graphicPlane(0).displayHardware());
    if (LIKELY(hw.canDraw())) {
        // repaint the framebuffer (if needed)

        const int index = hw.getCurrentBufferIndex();
        GraphicLog& logger(GraphicLog::getInstance());

        logger.log(GraphicLog::SF_REPAINT, index);
        handleRepaint(); //合并所有layer并填充到buffer中去

        // inform the h/w that we're done compositing
        logger.log(GraphicLog::SF_COMPOSITION_COMPLETE, index);
        hw.compositionComplete();

        logger.log(GraphicLog::SF_SWAP_BUFFERS, index);
        postFramebuffer();  //互换front buffer和back buffer，调用EGL接口进行显示

        logger.log(GraphicLog::SF_REPAINT_DONE, index);
    } else {
        // pretend we did the post
        hw.compositionComplete();
        usleep(16667); // 60 fps period,每秒刷新60次
    }
    return true;
}

3. SurfaceFlinger::createSurface

提供给应用程序的主要接口，该接口可以创建一个surface，底层会根据参数创建layer以及分配内存（共2个buffer：front/back buffer），surface相关参数会反馈给上层。

sp<ISurface> SurfaceFlinger::createSurface(
        ISurfaceComposerClient::surface_data_t* params,
        const String8& name,
        const sp<Client>& client,
        DisplayID d, uint32_t w, uint32_t h, PixelFormat format,
        uint32_t flags)
{
    sp<LayerBaseClient> layer;
    sp<ISurface> surfaceHandle;

    if (int32_t(w|h) < 0) {
        LOGE("createSurface() failed, w or h is negative (w=%d, h=%d)",
                int(w), int(h));
        return surfaceHandle;
    }

    //LOGD("createSurface for pid %d (%d x %d)", pid, w, h);
    sp<Layer> normalLayer;
    //创建layer，根据参数（宽高格式）分配内存（共2个buffer：front/back buffer）
    switch (flags & eFXSurfaceMask) {
        case eFXSurfaceNormal:
            normalLayer = createNormalSurface(client, d, w, h, flags, format);
            layer = normalLayer;
            break;
        case eFXSurfaceBlur:
            // for now we treat Blur as Dim, until we can implement it
            // efficiently.
        case eFXSurfaceDim:
            layer = createDimSurface(client, d, w, h, flags);
            break;
        case eFXSurfaceScreenshot:
            layer = createScreenshotSurface(client, d, w, h, flags);
            break;
    }

    if (layer != 0) {
        layer->initStates(w, h, flags);
        layer->setName(name);
        ssize_t token = addClientLayer(client, layer);
        
        //创建surface
        surfaceHandle = layer->getSurface();
        if (surfaceHandle != 0) {
            params->token = token;
            params->identity = layer->getIdentity();
            if (normalLayer != 0) {
                Mutex::Autolock _l(mStateLock);
                mLayerMap.add(layer->getSurfaceBinder(), normalLayer);
            }
        }

        setTransactionFlags(eTransactionNeeded);
    }

    return surfaceHandle;
}

4. SurfaceFlinger::setTransactionState

处理上层的各个命令，并根据flag设置event通知Threadloop进行处理。

void SurfaceFlinger::setTransactionState(const Vector<ComposerState>& state,
        int orientation) {
    Mutex::Autolock _l(mStateLock);

    uint32_t flags = 0;
    if (mCurrentState.orientation != orientation) {
        if (uint32_t(orientation)<=eOrientation270 || orientation==42) {
            mCurrentState.orientation = orientation;
            flags |= eTransactionNeeded;
            mResizeTransationPending = true;
        } else if (orientation != eOrientationUnchanged) {
            LOGW("setTransactionState: ignoring unrecognized orientation: %d",
                    orientation);
        }
    }

    const size_t count = state.size();
    for (size_t i=0 ; i<count ; i++) {
        const ComposerState& s(state[i]);
        sp<Client> client( static_cast<Client *>(s.client.get()) );
        flags |= setClientStateLocked(client, s.state);
    }
    if (flags) {
        setTransactionFlags(flags);
    }

    signalEvent();

    // if there is a transaction with a resize, wait for it to
    // take effect before returning.
    while (mResizeTransationPending) {
        status_t err = mTransactionCV.waitRelative(mStateLock, s2ns(5));
        if (CC_UNLIKELY(err != NO_ERROR)) {
            // just in case something goes wrong in SF, return to the
            // called after a few seconds.
            LOGW_IF(err == TIMED_OUT, "closeGlobalTransaction timed out!");
            mResizeTransationPending = false;
            break;
        }
    }
}

5. SurfaceFlinger::composeSurfaces

该接口在threadLoop->handleRepaint中被调用，负责将所有存在的surface进行合并，OpenGL模块负责这个部分。

6. SurfaceFlinger::postFramebuffer

该接口在threadLoop中被调用，负责将合成好的数据（存在于back buffer中）推入front buffer中，然后调用HAL接口命令底层显示。

7. surface与layer

从3中可知，上层每创建一个surface的时候，底层都会同时创建一个layer，下面看一下surface及layer的相关属性。

Note：code中相关结构体太大，就不全部罗列出来了

A、Surface相关属性（详细参考文件surface.h）

a1：SurfaceID：根据此ID把相关surface和layer对应起来

a2：SurfaceInfo

包括宽高格式等信息

a3：2个buffer指针、buffer索引等信息