Android P图形架构之SurfaceFlinger加载显示屏流程

拼搏现实的明天。 2024-04-18 13:10 78阅读 0赞

相关源码：  
\\frameworks\\base\\services\\core\\java\\com\\android\\server\\display\\LocalDisplayAdapter.java  
\\frameworks\\base\\core\\java\\android\\view\\SurfaceControl.java  
\\frameworks\\base\\core/jni\\android\_view\_SurfaceControl.cpp  
frameworks\\native\\libs\\gui\\include\\private\\gui\\ComposerService.h  
\\frameworks\\base\\services\\core\\java\\com\\android\\server\\display\\DisplayManagerService.java  
\\frameworks/native/services/surfaceflinger/DisplayDevice.h  
frameworks/native/services/surfaceflinger/DisplayHardware/HWComposer.h  
\\frameworks\\native\\libs\\gui\\ISurfaceComposerClient.cpp  
\\frameworks\\native\\libs\\gui\\ISurfaceComposer.cpp  
hardware\\libhardware\\include\\hardware\\hwcomposer\_defs.h  
\\frameworks\\native\\services\\surfaceflinger\\SurfaceFlinger.cpp  
\\frameworks\\native\\services\\surfaceflinger\\DisplayHardware\\HWC2.cpp  
\\vendor\\nxp-opensource\\imx\\display\\hwcomposer\_v20\\hwcomposer.cpp  
\\hardware\\interfaces\\graphics\\composer\\2.1\\utils\\passthrough\\include\\composer-passthrough\\2.1\\HwcHal.h

官方资料：  
[https://source.android.com/devices/graphics][https_source.android.com_devices_graphics]  
[https://source.android.google.cn/devices/graphics?hl=zh\_cn][https_source.android.google.cn_devices_graphics_hl_zh_cn]  
[https://source.android.google.cn/devices/graphics][https_source.android.google.cn_devices_graphics]

谷歌官网图形架构：  
![Surface 如何被渲染][Surface]

### 1、LocalDisplayAdapter.java ###

LocalDisplayAdapter的主要作用是初始化显示屏，从SurfaceFlinger中获取到屏的显示，并发送给DisplayManagerService进行显示屏的初始化。  
其中，getBuiltInDisplay最终是调用SurfaceFlinger中的getBuiltInDisplay，由SurfaceFlinger管理的显示适配器。

源码路径：\\frameworks\\base\\services\\core\\java\\com\\android\\server\\display\\LocalDisplayAdapter.java

private static final int[] BUILT_IN_DISPLAY_IDS_TO_SCAN = new int[] { 
            SurfaceControl.BUILT_IN_DISPLAY_ID_MAIN,
            SurfaceControl.BUILT_IN_DISPLAY_ID_HDMI,
            SurfaceControl.BUILT_IN_DISPLAY_ID_THIRD,	//add by sunxiaolin 20190906
    };
    
    @Override
    public void registerLocked() { 
        super.registerLocked();
        mHotplugReceiver = new HotplugDisplayEventReceiver(getHandler().getLooper());
        for (int builtInDisplayId : BUILT_IN_DISPLAY_IDS_TO_SCAN) { 
            tryConnectDisplayLocked(builtInDisplayId);
        }
    }
    从SurfaceFlinger中获取显示屏信息，并通过DisplayManagerService，add displays
    private void tryConnectDisplayLocked(int builtInDisplayId) { 
    	//最终调用到SurfaceFlinger中getBuiltInDisplay，获取到可以使用的显示屏display
        IBinder displayToken = SurfaceControl.getBuiltInDisplay(builtInDisplayId);
        if (displayToken != null) { 
    		//省略一部分代码
    		//...
    		//
    		sendDisplayDeviceEventLocked(device, DISPLAY_DEVICE_EVENT_ADDED);
    	}
    }

### 2、ISurfaceComposer.cpp ###

LocalDisplayAdapter中的getBuiltInDisplay，最终是调用SurfaceFlinger中的getBuiltInDisplay()，但是我们还是详细跟一下JNI调用的流程：  
SurfaceControl中的getBuiltInDisplay()调用了JNI的nativeGetBuiltInDisplay，定义如下：  
\\frameworks\\base\\core\\java\\android\\view\\SurfaceControl.java

private static native IBinder nativeGetBuiltInDisplay(int physicalDisplayId);
    public static IBinder getBuiltInDisplay(int builtInDisplayId) { 
        return nativeGetBuiltInDisplay(builtInDisplayId);
    }

android\_view\_SurfaceControl中调用的是SurfaceComposerClient中的getBuiltInDisplay，  
\\frameworks\\base\\core/jni\\android\_view\_SurfaceControl.cpp

static jobject nativeGetBuiltInDisplay(JNIEnv* env, jclass clazz, jint id) { 
        sp<IBinder> token(SurfaceComposerClient::getBuiltInDisplay(id));
        return javaObjectForIBinder(env, token);
    }

SurfaceComposerClient调用是ISurfaceComposer中的getBuiltInDisplay，实现如下：  
\\frameworks\\native\\libs\\gui\\SurfaceComposerClient.cpp

sp<IBinder> SurfaceComposerClient::getBuiltInDisplay(int32_t id) { 
        return ComposerService::getComposerService()->getBuiltInDisplay(id);
    }

ComposerService中关于getComposerService()的定义，得知调用的是ISurfaceComposer中的接口：  
frameworks\\native\\libs\\gui\\include\\private\\gui\\ComposerService.h

// Get a connection to the Composer Service. This will block until
    // a connection is established.
    static sp<ISurfaceComposer> getComposerService();

\\frameworks\\native\\libs\\gui\\ISurfaceComposer.cpp

virtual sp<IBinder> getBuiltInDisplay(int32_t id)
    { 
        Parcel data, reply;
        data.writeInterfaceToken(ISurfaceComposer::getInterfaceDescriptor());
        data.writeInt32(id);
        remote()->transact(BnSurfaceComposer::GET_BUILT_IN_DISPLAY, data, &reply);
        return reply.readStrongBinder();
    }
    status_t BnSurfaceComposer::onTransact(uint32_t code, const Parcel& data, Parcel* reply, uint32_t flags)
    { 
        switch(code) { 
           case GET_BUILT_IN_DISPLAY: { 
    	        CHECK_INTERFACE(ISurfaceComposer, data, reply);
    	        int32_t id = data.readInt32();
    	        //调用到SurfaceFlinger中的getBuiltInDisplay
    	        sp<IBinder> display(getBuiltInDisplay(id));
    	        reply->writeStrongBinder(display);
    	        return NO_ERROR;
         }
       }
    }

### 3、SurfaceFlinger.java ###

源码路径：\\frameworks\\native\\services\\surfaceflinger\\SurfaceFlinger.cpp  
//返回给LocalDisplayAdapter.java中的tryConnectDisplayLocked，以便完成显示屏连接的功能

sp<IBinder> SurfaceFlinger::getBuiltInDisplay(int32_t id) { 
        if (uint32_t(id) >= DisplayDevice::NUM_BUILTIN_DISPLAY_TYPES) { 
            ALOGE("getDefaultDisplay: id=%d is not a valid default display id", id);
            return nullptr;
        }
        ALOGI("sunxiaolin,getDefaultDisplay: id=%d", id);
        return mBuiltinDisplays[id];
    }

问题点：SurfaceFlinger中的显示屏信息又是从何而来呢？  
getBuiltInDisplay()中可以看到，显示屏信息是存在mBuiltinDisplays中的，mBuiltinDisplays定义如下：

sp<IBinder> mBuiltinDisplays[DisplayDevice::NUM_BUILTIN_DISPLAY_TYPES];

而mBuiltinDisplays的初始化又是在processDisplayHotplugEventsLocked中进行完成。  
事实上，底层驱动层代码将发送Hotplug的消息给到SurfaceFlinger，告知SurfaceFlinger有几块显示屏和相关信息，并进行初始化处理。

void SurfaceFlinger::processDisplayHotplugEventsLocked() { 
        for (const auto& event : mPendingHotplugEvents) { 
        	//判断displayType
            auto displayType = determineDisplayType(event.display, event.connection);
            if (displayType == DisplayDevice::DISPLAY_ID_INVALID) { 
                ALOGW("Unable to determine the display type for display %" PRIu64, event.display);
                continue;
            }
    
    		//省略一部分代码
    		//...
    		
    		//调用onHotplug，获取到
            getBE().mHwc->onHotplug(event.display, displayType, event.connection);
    
    		ALOGI("sunxiaolin processDisplayHotplugEventsLocked displayType=%d",displayType);
    
            if (event.connection == HWC2::Connection::Connected) { 
                if (!mBuiltinDisplays[displayType].get()) { 
                    ALOGV("sunxiaolin,Creating built in display %d", displayType);
                    mBuiltinDisplays[displayType] = new BBinder();
                    // All non-virtual displays are currently considered secure.
                    DisplayDeviceState info(displayType, true);
                    if( displayType == DisplayDevice::DISPLAY_THIRD ){ 
    					info.displayName = "THIRD Screen";
    				}else{ 
    					 info.displayName = displayType == DisplayDevice::DISPLAY_PRIMARY ?
                            "Built-in Screen" : "External Screen";
    				}
                    mCurrentState.displays.add(mBuiltinDisplays[displayType], info);
                    mInterceptor->saveDisplayCreation(info);
                }
            } else { 
                ALOGV("Removing built in display %d", displayType);
    
                ssize_t idx = mCurrentState.displays.indexOfKey(mBuiltinDisplays[displayType]);
                if (idx >= 0) { 
                    const DisplayDeviceState& info(mCurrentState.displays.valueAt(idx));
                    mInterceptor->saveDisplayDeletion(info.displayId);
                    mCurrentState.displays.removeItemsAt(idx);
                }
                mBuiltinDisplays[displayType].clear();
            }
    
            processDisplayChangesLocked();
        }
    
        mPendingHotplugEvents.clear();
    }

SurfaceFlinger接收到HAL层Hotplug消息流程如下：  
HAL层调用到HWC2.cpp中，代码如下：  
\\frameworks\\native\\services\\surfaceflinger\\DisplayHardware\\HWC2.cpp

Return<void> onHotplug(Hwc2::Display display,
                           IComposerCallback::Connection conn) override
    { 
        HWC2::Connection connection = static_cast<HWC2::Connection>(conn);
        mCallback->onHotplugReceived(mSequenceId, display, connection);
        return Void();
    }

mCallback是在SurfaceFlinger中init()的时候注册的：

getBE().mHwc->registerCallback(this, getBE().mComposerSequenceId);

所以onHotplugReceived调用到SurfaceFlinger中的onHotplugReceived，并最终processDisplayHotplugEventsLocked，对mBuiltinDisplays进行了初始化。

调式中打印的Log,可以分析整个display加载的流程

1970-01-01 08:00:14.457 2506-2506/? I/HWC2: sunxiaolin,registerCallback,Hwc2
    1970-01-01 08:00:14.461 2592-2667/? I/display: sunxiaolin,DisplayManager
    1970-01-01 08:00:14.574 2592-2684/? I/display: sunxiaolin,threadLoop
    1970-01-01 08:00:14.574 2592-2667/? I/hwcomposer: sunxiaolin,hwc2_register_callback HWC_DISPLAY_PRIMARY
    1970-01-01 08:00:14.574 2592-2667/? I/hwcomposer: sunxiaolin,onHotplug disp=0,connected=1
    1970-01-01 08:00:14.574 2506-2506/? I/HWC2: sunxiaolin,onHotplug,Hwc2
    1970-01-01 08:00:14.575 2506-2506/? I/SurfaceFlinger: sunxiaolin determineDisplayType
    1970-01-01 08:00:14.575 2506-2506/? I/SurfaceFlinger: sunxiaolin determineDisplayType primaryDisplayId2
    1970-01-01 08:00:14.575 2506-2506/? I/HWC2: sunxiaolin, Device::onHotplug,Hwc2
    1970-01-01 08:00:14.575 2506-2506/? I/HWC2: sunxiaolin, Device::onHotplug,Hwc2,displayId=0
    1970-01-01 08:00:14.575 2506-2506/? I/HWC2: sunxiaolin, Device::onHotplug,Hwc2,displayType=1
    1970-01-01 08:00:14.575 2506-2506/? I/SurfaceFlinger: sunxiaolin processDisplayHotplugEventsLocked displayType=0
    1970-01-01 08:00:14.575 2506-2506/? V/SurfaceFlinger: sunxiaolin,Creating built in display 0
    1970-01-01 08:00:14.575 2506-2506/? I/SurfaceFlinger: sunxiaolin processDisplayChangesLocked find displays that were added state.type(hwcId)=0
    1970-01-01 08:00:15.048 2691-2696/? I/SurfaceFlinger: sunxiaolin,ISurfaceComposer,getDefaultDisplay: id=0
    1970-01-01 08:00:15.048 2506-2629/? I/SurfaceFlinger: sunxiaolin,getDefaultDisplay: id=0
    1970-01-01 08:00:15.241 2592-2592/? I/hwcomposer: sunxiaolin,hwc2_present_display HWC_DISPLAY_EXTERNAL
    1970-01-01 08:00:15.241 2592-2592/? I/hwcomposer: sunxiaolin,onHotplug disp=1,connected=1
    1970-01-01 08:00:15.241 2506-2506/? I/HWC2: sunxiaolin,onHotplug,Hwc2
    1970-01-01 08:00:15.241 2506-2506/? I/SurfaceFlinger: sunxiaolin determineDisplayType
    1970-01-01 08:00:15.241 2506-2506/? I/SurfaceFlinger: sunxiaolin determineDisplayType externalDisplayId2
    1970-01-01 08:00:15.241 2506-2506/? I/HWC2: sunxiaolin, Device::onHotplug,Hwc2
    1970-01-01 08:00:15.241 2506-2506/? I/HWC2: sunxiaolin, Device::onHotplug,Hwc2,displayId=1
    1970-01-01 08:00:15.242 2506-2506/? I/HWC2: sunxiaolin, Device::onHotplug,Hwc2,displayType=1
    1970-01-01 08:00:15.242 2506-2506/? I/SurfaceFlinger: sunxiaolin processDisplayHotplugEventsLocked displayType=1
    1970-01-01 08:00:15.242 2506-2506/? V/SurfaceFlinger: sunxiaolin,Creating built in display 1
    1970-01-01 08:00:15.242 2506-2506/? I/SurfaceFlinger: sunxiaolin processDisplayChangesLocked find displays that were added state.type(hwcId)=1
    1970-01-01 08:00:15.253 2592-2592/? I/hwcomposer: sunxiaolin,hwc2_present_display HWC_DISPLAY_EXTERNAL + 1
    1970-01-01 08:00:15.253 2592-2592/? I/hwcomposer: sunxiaolin,onHotplug disp=2,connected=1
    1970-01-01 08:00:15.253 2506-2506/? I/HWC2: sunxiaolin,onHotplug,Hwc2
    1970-01-01 08:00:15.253 2506-2506/? I/SurfaceFlinger: sunxiaolin determineDisplayType
    1970-01-01 08:00:15.253 2506-2506/? I/SurfaceFlinger: sunxiaolin determineDisplayType thirdDisplayId2
    1970-01-01 08:00:15.253 2506-2506/? I/HWC2: sunxiaolin, Device::onHotplug,Hwc2
    1970-01-01 08:00:15.253 2506-2506/? I/HWC2: sunxiaolin, Device::onHotplug,Hwc2,displayId=2
    1970-01-01 08:00:15.254 2506-2506/? I/HWC2: sunxiaolin, Device::onHotplug,Hwc2,displayType=1
    1970-01-01 08:00:15.254 2506-2506/? I/SurfaceFlinger: sunxiaolin processDisplayHotplugEventsLocked displayType=2
    1970-01-01 08:00:15.254 2506-2506/? V/SurfaceFlinger: sunxiaolin,Creating built in display 2
    1970-01-01 08:00:15.254 2506-2506/? I/SurfaceFlinger: sunxiaolin processDisplayChangesLocked find displays that were added state.type(hwcId)=2
    1970-01-01 08:00:15.290 2506-2522/? I/HWC2: sunxiaolin,onVsync,Hwc2

[https_source.android.com_devices_graphics]: https://source.android.com/devices/graphics
[https_source.android.google.cn_devices_graphics_hl_zh_cn]: https://source.android.google.cn/devices/graphics?hl=zh_cn
[https_source.android.google.cn_devices_graphics]: https://source.android.google.cn/devices/graphics
[Surface]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/18/f521b437a79a4b689778694c7d87d52f.png