Android P 显示流程（一）---Display设备初始化过程分析

最新推荐文章于 2025-04-27 17:31:29 发布

Give.Me.Five

最新推荐文章于 2025-04-27 17:31:29 发布

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分类专栏： Android P #显示文章标签： android

本文链接：https://blog.youkuaiyun.com/tovey2008/article/details/109681729

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Android P 显示流程（一）

SurfaceFlinger

SurfaceFlinger

SurfaceFlinger在Android中是显示的核心部分，所以我们今天从SurfaceFlinger开始来研究。

SurfaceFlinger的启动

SurfaceFlinger的启动要从main_surfaceflinger.cpp开始看：

int main(int, char**){
   
	...
	//启动 Hal层的IAllocator : hardware::graphics::allocator::V2.0::IAllocator
	startGraphicsAllocatorService();
	...
	//instantiate surfaceflinger
	sp<SurfaceFlinger> flinger = new SurfaceFlinger();
	//initialize before clients can connect
	flinger->init();
	//publish surface flinger
	sp<IServiceManager> sm(defaultServiceManager());
	sm->addService(String16(SrufaceFlinger::getServiceName()), flinger, false, 
		IServiceManager::DUMP_FLAG_PRIORITY_CRITICAL | IServiceManager::DUMP_FLAG_PROTO);
	//启动DisplayService
	startDisplayService();
	//run surface flinger in this thread
	flinger->run();
}

重点来看SurfaceFlinger实例化，以及init(), run()…

void SurfaceFlinger::init(){
   
	...
	//初始化mBE 即 SurfaceFlingerBE
	getBE().mRenderEngine = RE::impl::RenderEngine::create(HAL_PIXEL_FORMAT_RGBA_8888, hasWideColorDisplay? RE::RenderEngine::WIDE_COLOR_SUPPORT:0);
	getBE().mHwc.reset(new HWComposer(std::make_unique<Hwc2::impl::Composer>(getBe().mHwcServiceName)));
	//注册HAL事件上报的回调
	getBE().mHwc->registerCallback(this, getBE().mComposerSequenceId);
	//处理HAL层上报的事件回调
	processDisplayHotplugEventsLocked();
	getBE().mRenderEngine->primeCache();
	//初始化Displays
	initializeDisplays();
}

void SurfaceFlinger::run(){
   
	do{
   
		waitForEvent();
	}while(true);
}

init中有一部分是用来初始化SurfaceFlingerBE中的属性变量。主要是将SurfaceFlinger与Hal层的Composer连接起来。getBE()中的mHwc 就可以关联到HWComposer。
上面init()里主要有三步，第一步是注册回调，第二步为回调事件处理，第三步为显示的初始化。因为SurfaceFlinger启动时，kernel里的DRM的显示屏一般已经初始化好了，然后通过onHotPlug事件报上来了，这里再来获取配置相关参数。

注册HAL层事件回调

HWComposer->registerCallback(this, getBE().mComposerSequenceId)---->
HWC2::Device->registerCallback(callback, sequenceId)---->
HWC2::impl::Composer->registerCallback(new ComposerCallbackBridge(callback, sequenceId))---->
IComposerClient->registerCallback(callback)---->
HwcHalImpl->registerEventCallback(make_unique(callback, mResources.get())---->
mDispatch.registerCallback(mDevice, HWC2_CALLBACK_HOTPLUG, this,reinterpret_cast<hwc2_function_pointer_t>(hotplugHook))---->
HWC2On1Adapter::registerCallbackHook(mDevice, HWC2_CALLBACK_HOTPLUG, this,reinterpret_cast<hwc2_function_pointer_t>(hotplugHook)) ---->
HWC2On1Adapter::registerCallback(HWC2_CALLBACK_HOTPLUG,
hwc2_callback_data_t callbackData, reinterpret_cast<hwc2_function_pointer_t>(hotplugHook))
以上为完整的registerCallback的调用链。

Error HWC2On1Adapter::registerCallback(Callback descriptor,
        hwc2_callback_data_t callbackData, hwc2_function_pointer_t pointer)
{
   
	...
	 std::vector<std::pair<hwc2_display_t, int>> pendingHotplugs;
	 } else if (descriptor == Callback::Hotplug) {
   
        // Hotplug the primary display
        pendingHotplugs.emplace_back(mHwc1DisplayMap[HWC_DISPLAY_PRIMARY],
                static_cast<int32_t>(Connection::Connected));
		for (auto pending : mPendingHotplugs) {
   
            auto hwc1DisplayId