android graphic(11)—底层初始化displays

这里的底层不牵扯内核以下的分析，主要是内核亮屏后，HAL层以上各层是如何联系起来的，通过层层转交，将displays的信息从内核填充到上层。这里主要涉及framework中的HWComposer，surfaceflinger，HAL层的Hwcomposer，为了便于区分，framework层记为HWC，HAL层记为Hwc，HWC相当于是Hwc的wrapper。

初始化HWC

SurfaceFlinger::init()—>初始化HWC

 mHwc = new HWComposer(this,
            *static_cast<HWComposer::EventHandler *>(this));

HWComposer::HWComposer(
        const sp<SurfaceFlinger>& flinger,
        EventHandler& handler)
    : mFlinger(flinger),
      mFbDev(0), mHwc(0), mNumDisplays(1),
      mCBContext(new cb_context),
      mEventHandler(handler),
      mDebugForceFakeVSync(false)
{
    for (size_t i =0 ; i<MAX_HWC_DISPLAYS ; i++) {
        mLists[i] = 0;
    }

    for (size_t i=0 ; i<HWC_NUM_PHYSICAL_DISPLAY_TYPES ; i++) {
        mLastHwVSync[i] = 0;
        mVSyncCounts[i] = 0;
    }

    // Note: some devices may insist that the FB HAL be opened before HWC.
    int fberr = loadFbHalModule();
    loadHwcModule();
    //如果有Hwc，即HWComposer的hal层，则关闭fb
    if (mFbDev && mHwc && hwcHasApiVersion(mHwc, HWC_DEVICE_API_VERSION_1_1)) {
        // close FB HAL if we don't needed it.
        // FIXME: this is temporary until we're not forced to open FB HAL
        // before HWC.
        framebuffer_close(mFbDev);
        mFbDev = NULL;
    }


    // these display IDs are always reserved
    // NUM_BUILTIN_DISPLAYS 2
    for (size_t i=0 ; i<NUM_BUILTIN_DISPLAYS ; i++) {
        mAllocatedDisplayIDs.markBit(i);
    }

    if (mHwc) {
        ALOGI("Using %s version %u.%u", HWC_HARDWARE_COMPOSER,
              (hwcApiVersion(mHwc) >> 24) & 0xff,
              (hwcApiVersion(mHwc) >> 16) & 0xff);
        //把HWC中，即framework中的回调函数注册到HAL中，用来在HAL中回调
        if (mHwc->registerProcs) {
            mCBContext->hwc = this;
            mCBContext->procs.invalidate = &hook_invalidate;
            mCBContext->procs.vsync = &hook_vsync;
            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);
        }

        // don't need a vsync thread if we have a hardware composer
        needVSyncThread = false;
        // 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
        // 1.3版本，已经支持虚拟display，3个
        if (hwcHasApiVersion(mHwc, HWC_DEVICE_API_VERSION_1_3)) {
            // 1.3 adds support for virtual displays
            mNumDisplays = MAX_HWC_DISPLAYS;
        } else if (hwcHasApiVersion(mHwc, HWC_DEVICE_API_VERSION_1_1)) {
            // 1.1 adds support for multiple displays
            mNumDisplays = NUM_BUILTIN_DISPLAYS;
        } else {
            mNumDisplays = 1;
        }
    }
    //fb已经关闭 
    if (mFbDev) {

    } else if (mHwc) {
        // here we're guaranteed to have at least HWC 1.1
        //HWC获取display信息的地方，填充mDisplayData[3]
        //DisplayData mDisplayData[MAX_HWC_DISPLAYS];
        for (size_t i =0 ; i<NUM_BUILTIN_DISPLAYS ; i++) {
            queryDisplayProperties(i);
        }
    }
    //vsync软件模拟线程
    if (needVSyncThread) {
        // we don't have VSYNC support, we need to fake it
        mVSyncThread = new VSyncThread(*this);
    }
}

//调用HAL层接口，获取屏幕的参数，HAL会和驱动打交道
//这样就相当于在上层把display的参数初始化了,
//主要填充DisplayData mDisplayData[MAX_HWC_DISPLAYS];
status_t HWComposer::queryDisplayProperties(int disp) {

    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);


    err = mHwc->getDisplayAttributes(mHwc, disp, config, DISPLAY_ATTRIBUTES, values);


    int32_t w = 0, h = 0;
    for (size_t i = 0; i < NUM_DISPLAY_ATTRIBUTES - 1; i++) {
        switch (DISPLAY_ATTRIBUTES[i]) {
        case HWC_DISPLAY_VSYNC_PERIOD:
            mDisplayData[disp].refresh = nsecs_t(values[i]);
            break;
        case HWC_DISPLAY_WIDTH:
            mDisplayData[disp].width = values[i];
            break;
        case HWC_DISPLAY_HEIGHT:
            mDisplayData[disp].height = values[i];
            break;
        case HWC_DISPLAY_DPI_X:
            mDisplayData[disp].xdpi = values[i] / 1000.0f;
            break;
        case HWC_DISPLAY_DPI_Y:
            mDisplayData[disp].ydpi = values[i] / 1000.0f;
            break;
        default:
            ALOG_ASSERT(false, "unknown display attribute[%d] %#x",
                    i, DISPLAY_ATTRIBUTES[i]);
            break;
        }
    }

    // FIXME: what should we set the format to?
    mDisplayData[disp].format = HAL_PIXEL_FORMAT_RGBA_8888;
    mDisplayData[disp].connected = true;
    if (mDisplayData[disp].xdpi == 0.0f || mDisplayData[disp].ydpi == 0.0f) {
        float dpi = getDefaultDensity(h);
        mDisplayData[disp].xdpi = dpi;
        mDisplayData[disp].ydpi = dpi;
    }
    return NO_ERROR;
}

surfaceflinger 初始化displays

SurfaceFlinger::init()—>

 // initialize our non-virtual displays
 // 初始化物理屏幕，NUM_BUILTIN_DISPLAY_TYPES 2
 // 目前除了默认屏幕，还支持一个hdmi的物理屏幕
    for (size_t i=0 ; i<DisplayDevice::NUM_BUILTIN_DISPLAY_TYPES ; i++) {
        DisplayDevice::DisplayType type((DisplayDevice::DisplayType)i);
        // set-up the displays that are already connected
        // 屏幕是否连接，即HWC中已经成功获取到这个屏幕的信息
        if (mHwc->isConnected(i) || type==DisplayDevice::DISPLAY_PRIMARY) { // All non-virtual displays are currently considered secure. bool isSecure = true; // 创建显示器在surface flinger中的代表，new BBinder， // 将new BBinder和DisplayDeviceState保存在mCurrentState.displays中 createBuiltinDisplayLocked(type); //取出上面的BBinder wp<IBinder> token = mBuiltinDisplays[i]; //新建BufferQueue，FramebufferSurface，DisplayDevice sp<BufferQueue> bq = new BufferQueue(new GraphicBufferAlloc()); sp<FramebufferSurface> fbs = new FramebufferSurface(*mHwc, i, bq); sp<DisplayDevice> hw = new DisplayDevice(this, type, allocateHwcDisplayId(type), isSecure, token, fbs, bq, mEGLConfig); if (i > DisplayDevice::DISPLAY_PRIMARY) { // 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(); }
        // DefaultKeyedVector< wp<IBinder>, sp<DisplayDevice> > mDisplays;
            mDisplays.add(token, hw);
        }
    }

bool HWComposer::isConnected(int disp) const {
    return mDisplayData[disp].connected;
}

    struct State {
        LayerVector layersSortedByZ;
        DefaultKeyedVector< wp<IBinder>, DisplayDeviceState> displays;
    };

    struct DisplayDeviceState {
        DisplayDeviceState();
        DisplayDeviceState(DisplayDevice::DisplayType type);
        bool isValid() const { return type >= 0; }
        bool isMainDisplay() const { return type == DisplayDevice::DISPLAY_PRIMARY; }
        bool isVirtualDisplay() const { return type >= DisplayDevice::DISPLAY_VIRTUAL; }
        DisplayDevice::DisplayType type;
        sp<IGraphicBufferProducer> surface;
        uint32_t layerStack;
        Rect viewport;
        Rect frame;
        uint8_t orientation;
        String8 displayName;
        bool isSecure;
    };

void SurfaceFlinger::createBuiltinDisplayLocked(DisplayDevice::DisplayType type) {
    ALOGW_IF(mBuiltinDisplays[type],
            "Overwriting display token for display type %d", type);
    //sp<IBinder> mBuiltinDisplays[2]; 就是new BBinder，
    mBuiltinDisplays[type] = new BBinder();
    DisplayDeviceState info(type);
    // All non-virtual displays are currently considered secure.
    // 非virtual display都是secure的
    info.isSecure = true;
    // State mCurrentState;
    mCurrentState.displays.add(mBuiltinDisplays[type], info);
}

SurfaceFlinger::DisplayDeviceState::DisplayDeviceState(DisplayDevice::DisplayType type)
    : type(type), layerStack(DisplayDevice::NO_LAYER_STACK), orientation(0) { viewport.makeInvalid(); frame.makeInvalid(); }

通过上面的步骤，主要填充了HWComposer的mDisplayDate[3]、surface flinger的mCurrentState.displays(token,DisplayDeviceState)，mDisplays(token,DisplayDevice)，mBuiltinDisplays[2]（BBinder），

    // initialize our drawing state
    mDrawingState = mCurrentState;
    // set initial conditions (e.g. unblank default device) initializeDisplays();

void SurfaceFlinger::initializeDisplays() {
    class MessageScreenInitialized : public MessageBase {
        SurfaceFlinger* flinger;
    public:
        MessageScreenInitialized(SurfaceFlinger* flinger) : flinger(flinger) { }
        virtual bool handler() {
            flinger->onInitializeDisplays();
            return true;
        }
    };
    sp<MessageBase> msg = new MessageScreenInitialized(this);
    postMessageAsync(msg);  // we may be called from main thread, use async message
}

void SurfaceFlinger::onInitializeDisplays() {
    // reset screen orientation and use primary layer stack
    Vector<ComposerState> state;
    Vector<DisplayState> displays;
    //新建一个DisplayState 
    DisplayState d;
    d.what = DisplayState::eDisplayProjectionChanged |
             DisplayState::eLayerStackChanged;
    //默认屏幕的token
    d.token = mBuiltinDisplays[DisplayDevice::DISPLAY_PRIMARY];
    //layerStack 为0，orientation 为默认的eOrientationDefault
    d.layerStack = 0;
    d.orientation = DisplayState::eOrientationDefault;
    d.frame.makeInvalid();
    d.viewport.makeInvalid();
    displays.add(d);
    //利用displays的信息，设置mCurrentState.displays的状态
    setTransactionState(state, displays, 0);
    onScreenAcquired(getDefaultDisplayDevice());

    const nsecs_t period =
            getHwComposer().getRefreshPeriod(HWC_DISPLAY_PRIMARY);
    mAnimFrameTracker.setDisplayRefreshPeriod(period);
}

void SurfaceFlinger::setTransactionState(
        const Vector<ComposerState>& state,
        const Vector<DisplayState>& displays,
        uint32_t flags)
{
    ATRACE_CALL();
    Mutex::Autolock _l(mStateLock);
    uint32_t transactionFlags = 0;



    size_t count = displays.size();
    for (size_t i=0 ; i<count ; i++) {
        const DisplayState& s(displays[i]);
        transactionFlags |= setDisplayStateLocked(s);
    }
}

//根据DisplayState的信息更新mCurrentState.displays的信息
uint32_t SurfaceFlinger::setDisplayStateLocked(const DisplayState& s)
{
    ssize_t dpyIdx = mCurrentState.displays.indexOfKey(s.token);
    if (dpyIdx < 0)
        return 0;

    uint32_t flags = 0;
    DisplayDeviceState& disp(mCurrentState.displays.editValueAt(dpyIdx));
    if (disp.isValid()) {
        const uint32_t what = s.what;
        if (what & DisplayState::eSurfaceChanged) {
            if (disp.surface->asBinder() != s.surface->asBinder()) {
                disp.surface = s.surface;
                flags |= eDisplayTransactionNeeded;
            }
        }
        if (what & DisplayState::eLayerStackChanged) {
            if (disp.layerStack != s.layerStack) {
                disp.layerStack = s.layerStack;
                flags |= eDisplayTransactionNeeded;
            }
        }
        if (what & DisplayState::eDisplayProjectionChanged) {
            if (disp.orientation != s.orientation) {
                disp.orientation = s.orientation;
                flags |= eDisplayTransactionNeeded;
            }
            if (disp.frame != s.frame) {
                disp.frame = s.frame;
                flags |= eDisplayTransactionNeeded;
            }
            if (disp.viewport != s.viewport) {
                disp.viewport = s.viewport;
                flags |= eDisplayTransactionNeeded;
            }
        }
    }
    return flags;
}

    // returns the default Display
    // 返回默认屏幕的DisplayDevice
    sp<const DisplayDevice> getDefaultDisplayDevice() const {
        return getDisplayDevice(mBuiltinDisplays[DisplayDevice::DISPLAY_PRIMARY]);
    }

    sp<DisplayDevice> getDisplayDevice(const wp<IBinder>& dpy) {
        return mDisplays.valueFor(dpy);
    }

void SurfaceFlinger::onScreenAcquired(const sp<const DisplayDevice>& hw) {
    ALOGD("Screen acquired, type=%d flinger=%p", hw->getDisplayType(), this);
    if (hw->isScreenAcquired()) {
        // this is expected, e.g. when power manager wakes up during boot
        ALOGD(" screen was previously acquired");
        return;
    }

    hw->acquireScreen();
    int32_t type = hw->getDisplayType();
    if (type < DisplayDevice::NUM_BUILTIN_DISPLAY_TYPES) {
        // built-in display, tell the HWC
        getHwComposer().acquire(type);

        if (type == DisplayDevice::DISPLAY_PRIMARY) {
            // FIXME: eventthread only knows about the main display right now
            mEventThread->onScreenAcquired();
        //开启vsync开关
            resyncToHardwareVsync(true);
        }
    }
    mVisibleRegionsDirty = true;
    repaintEverything();
}

void DisplayDevice::acquireScreen() const {
    mScreenAcquired = true;
}

//acquire就是调用Hwc HAL的blank函数，
status_t HWComposer::acquire(int disp) {
    LOG_FATAL_IF(disp >= VIRTUAL_DISPLAY_ID_BASE);
    if (mHwc) {
        return (status_t)mHwc->blank(mHwc, disp, 0);
    }
    return NO_ERROR;
}

通过上面的分析，在底层，即surfaceflinger、HWC、Hwc中已经填充了系统displays的基本信息，后续分析surfaceflinger之上是如何初始化和使用displays的，上下联系起来。