【安卓13 源码】Input子系统（3） - EventHub增加设备的流程

由前面的分析知道，在创建inputreader 线程的时候，会去循环执行 looponce 方法。主要的处理工作是：

通过 getEvents() 从 EventHub 获取未处理的事件，这些事件分为两类：一类是原始输入事件即从设备节点中读取出的原始事件；一类是设备事件即输入设备可用性变化事件
通过 processEventsLocked() 对事件进行预处理

/frameworks/native/services/inputflinger/reader/InputReader.cpp

void InputReader::loopOnce() {
    int32_t oldGeneration;
    int32_t timeoutMillis;
    bool inputDevicesChanged = false;
    std::vector<InputDeviceInfo> inputDevices;
    { // acquire lock
        std::scoped_lock _l(mLock);

        oldGeneration = mGeneration;
        timeoutMillis = -1;

        uint32_t changes = mConfigurationChangesToRefresh;
        if (changes) {
            mConfigurationChangesToRefresh = 0;
            timeoutMillis = 0;
            refreshConfigurationLocked(changes);
        } else if (mNextTimeout != LLONG_MAX) {
            nsecs_t now = systemTime(SYSTEM_TIME_MONOTONIC);
            timeoutMillis = toMillisecondTimeoutDelay(now, mNextTimeout);
        }
    } // release lock


// 1）首先去eventhub 中获取事件，缓存到 mEventBuffer
    size_t count = mEventHub->getEvents(timeoutMillis, mEventBuffer, EVENT_BUFFER_SIZE);

    { // acquire lock
        std::scoped_lock _l(mLock);
        mReaderIsAliveCondition.notify_all();

        if (count) {

// 2）对 mEventBuffer 事件进行处理
            processEventsLocked(mEventBuffer, count);
        }

1）首先去eventhub 中获取事件，缓存到 mEventBuffer

/frameworks/native/services/inputflinger/reader/EventHub.cpp

size_t EventHub::getEvents(int timeoutMillis, RawEvent* buffer, size_t bufferSize) {
    ALOG_ASSERT(bufferSize >= 1);

    std::scoped_lock _l(mLock);

。。。。
//  初始值 mNeedToScanDevices 是为true 的
        if (mNeedToScanDevices) {
            mNeedToScanDevices = false;
// 去扫描设备 scanDevicesLocked
            scanDevicesLocked();
            mNeedToSendFinishedDeviceScan = true;
        }
// 遍历所有的打开的设备mOpeningDevices
        while (!mOpeningDevices.empty()) {
// 获取设备 Device
            std::unique_ptr<Device> device = std::move(*mOpeningDevices.rbegin());
            mOpeningDevices.pop_back();
            ALOGV("Reporting device opened: id=%d, name=%s\n", device->id, device->path.c_str());
            event->when = now;
            event->deviceId = device->id == mBuiltInKeyboardId ? 0 : device->id;

// 设置event事件类型是增加的DEVICE_ADDED
            event->type = DEVICE_ADDED;
            event += 1;

            // Try to find a matching video device by comparing device names
            for (auto it = mUnattachedVideoDevices.begin(); it != mUnattachedVideoDevices.end();
                 it++) {
                std::unique_ptr<TouchVideoDevice>& videoDevice = *it;
                if (tryAddVideoDeviceLocked(*device, videoDevice)) {
                    // videoDevice was transferred to 'device'
                    it = mUnattachedVideoDevices.erase(it);
                    break;
                }
            }

// 然后将设备的id和设备保存到 mDevices 中
            auto [dev_it, inserted] = mDevices.insert_or_assign(device->id, std::move(device));

// 扫描设备 scanDevicesLocked

// 扫描设备，path 为：DEVICE_PATH = "/dev/input";
void EventHub::scanDevicesLocked() {
    status_t result = scanDirLocked(DEVICE_PATH);

=======
status_t EventHub::scanDirLocked(const std::string& dirname) {
    for (const auto& entry : std::filesystem::directory_iterator(dirname)) {

// 打开所有的设备
        openDeviceLocked(entry.path());
    }

=======
void EventHub::openDeviceLocked(const std::string& devicePath) {

    ALOGV("Opening device: %s", devicePath.c_str());

// 打开驱动设备
    int fd = open(devicePath.c_str(), O_RDWR | O_CLOEXEC | O_NONBLOCK);

。。。。。
    // Allocate device.  (The device object takes ownership of the fd at this point.)
    int32_t deviceId = mNextDeviceId++;
// 创建 Device 对象
    std::unique_ptr<Device> device = std::make_unique<Device>(fd, deviceId, devicePath, identifier);

。。。。
    device->configureFd();

// 增肌 device，会打印下列log
    ALOGI("New device: id=%d, fd=%d, path='%s', name='%s', classes=%s, "
          "configuration='%s', keyLayout='%s', keyCharacterMap='%s', builtinKeyboard=%s, ",
          deviceId, fd, devicePath.c_str(), device->identifier.name.c_str(),
          device->classes.string().c_str(), device->configurationFile.c_str(),
          device->keyMap.keyLayoutFile.c_str(), device->keyMap.keyCharacterMapFile.c_str(),
          toString(mBuiltInKeyboardId == deviceId));

// 将其增加到map 中
    addDeviceLocked(std::move(device));
}

======
void EventHub::addDeviceLocked(std::unique_ptr<Device> device) {
    reportDeviceAddedForStatisticsLocked(device->identifier, device->classes);

// 将其保存到已经打开的设备map 中mOpeningDevices
    mOpeningDevices.push_back(std::move(device));
}

eventhub 将打开的设备保存到了 mOpeningDevices 中，在 InputReader 调用eventhub getevents的时候，去获取 mOpeningDevices先去eventhub 中获取事件，缓存到 mEventBuffer

2）对 mEventBuffer 事件进行处理

设置事件类型是增加的DEVICE_ADDED ，然后在inputreader 线程中处理 processEventsLocked

/frameworks/native/services/inputflinger/reader/InputReader.cpp

cpp 复制代码

void InputReader::processEventsLocked(const RawEvent* rawEvents, size_t count) {
    for (const RawEvent* rawEvent = rawEvents; count;) {
        int32_t type = rawEvent->type;
        size_t batchSize = 1;
        if (type < EventHubInterface::FIRST_SYNTHETIC_EVENT) {
            int32_t deviceId = rawEvent->deviceId;
            while (batchSize < count) {
                if (rawEvent[batchSize].type >= EventHubInterface::FIRST_SYNTHETIC_EVENT ||
                    rawEvent[batchSize].deviceId != deviceId) {
                    break;
                }
                batchSize += 1;
            }
#if DEBUG_RAW_EVENTS
            ALOGD("BatchSize: %zu Count: %zu", batchSize, count);
#endif
            processEventsForDeviceLocked(deviceId, rawEvent, batchSize);
        } else {
            switch (rawEvent->type) {
                case EventHubInterface::DEVICE_ADDED:

// 处理设备增加的消息
                    addDeviceLocked(rawEvent->when, rawEvent->deviceId);
                    break;
                case EventHubInterface::DEVICE_REMOVED:
                    removeDeviceLocked(rawEvent->when, rawEvent->deviceId);
                    break;
                case EventHubInterface::FINISHED_DEVICE_SCAN:
                    handleConfigurationChangedLocked(rawEvent->when);
                    break;
                default:
                    ALOG_ASSERT(false); // can't happen
                    break;
            }
        }
        count -= batchSize;
        rawEvent += batchSize;
    }
}

cpp 复制代码

void InputReader::addDeviceLocked(nsecs_t when, int32_t eventHubId) {
    if (mDevices.find(eventHubId) != mDevices.end()) {
        ALOGW("Ignoring spurious device added event for eventHubId %d.", eventHubId);
        return;
    }

    InputDeviceIdentifier identifier = mEventHub->getDeviceIdentifier(eventHubId);

// 依据设备的id 创建了 inputdevice 对象
    std::shared_ptr<InputDevice> device = createDeviceLocked(eventHubId, identifier);
    device->configure(when, &mConfig, 0);
    device->reset(when);

    if (device->isIgnored()) {
        ALOGI("Device added: id=%d, eventHubId=%d, name='%s', descriptor='%s' "
              "(ignored non-input device)",
              device->getId(), eventHubId, identifier.name.c_str(), identifier.descriptor.c_str());
    } else {

// 会打印下列log 增加了设备
        ALOGI("Device added: id=%d, eventHubId=%d, name='%s', descriptor='%s',sources=0x%08x",
              device->getId(), eventHubId, identifier.name.c_str(), identifier.descriptor.c_str(),
              device->getSources());
    }

// 将id 和对应的device 增加到了 mDevices 中
    mDevices.emplace(eventHubId, device);
    // Add device to device to EventHub ids map.
    const auto mapIt = mDeviceToEventHubIdsMap.find(device);
    if (mapIt == mDeviceToEventHubIdsMap.end()) {
        std::vector<int32_t> ids = {eventHubId};
        mDeviceToEventHubIdsMap.emplace(device, ids);
    } else {
        mapIt->second.push_back(eventHubId);
    }
    bumpGenerationLocked();

// 依据设备的id 创建了 inputdevice 对象

cpp 复制代码

std::shared_ptr<InputDevice> InputReader::createDeviceLocked(
        int32_t eventHubId, const InputDeviceIdentifier& identifier) {
    auto deviceIt = std::find_if(mDevices.begin(), mDevices.end(), [identifier](auto& devicePair) {
        return devicePair.second->getDescriptor().size() && identifier.descriptor.size() &&
                devicePair.second->getDescriptor() == identifier.descriptor;
    });

    std::shared_ptr<InputDevice> device;
    if (deviceIt != mDevices.end()) {
        device = deviceIt->second;
    } else {
        int32_t deviceId = (eventHubId < END_RESERVED_ID) ? eventHubId : nextInputDeviceIdLocked();

// 创建了 InputDevice 对象
        device = std::make_shared<InputDevice>(&mContext, deviceId, bumpGenerationLocked(),
                                               identifier);
    }

// 调用方法 addEventHubDevice
    device->addEventHubDevice(eventHubId);
    return device;
}

// 调用方法 addEventHubDevice

/frameworks/native/services/inputflinger/reader/InputDevice.cpp

New device: id=2, fd=246, path='/dev/input/event4', name='adaptive_ts', classes=TOUCH | TOUCH_MT

cpp 复制代码

void InputDevice::addEventHubDevice(int32_t eventHubId, bool populateMappers) {
    if (mDevices.find(eventHubId) != mDevices.end()) {
        return;
    }

/ / 创建了 InputDeviceContext 对象，传入this 对象和 eventHubId
    std::unique_ptr<InputDeviceContext> contextPtr(new InputDeviceContext(*this, eventHubId));
    Flags<InputDeviceClass> classes = contextPtr->getDeviceClasses();
    std::vector<std::unique_ptr<InputMapper>> mappers;

    // Check if we should skip population
    if (!populateMappers) {
        mDevices.insert({eventHubId, std::make_pair(std::move(contextPtr), std::move(mappers))});
        return;
    }

// 然后依据不同的设备创建不同的 mapper：SwitchInputMapper
// 将其放到 mappers 中
    // Switch-like devices.
    if (classes.test(InputDeviceClass::SWITCH)) {
        mappers.push_back(std::make_unique<SwitchInputMapper>(*contextPtr));
    }

// 下列是多点触控和单触控的
    // Touchscreens and touchpad devices.
    if (classes.test(InputDeviceClass::TOUCH_MT)) {
        mappers.push_back(std::make_unique<MultiTouchInputMapper>(*contextPtr));
    } else if (classes.test(InputDeviceClass::TOUCH)) {
        mappers.push_back(std::make_unique<SingleTouchInputMapper>(*contextPtr));
    }

。。。。
    // insert the context into the devices set
// 最后将其保存到 mDevices 中
    mDevices.insert({eventHubId, std::make_pair(std::move(contextPtr), std::move(mappers))});

MultiTouchInputMapper 多点触控是继承了 TouchInputMapper

class MultiTouchInputMapper : public TouchInputMapper

/frameworks/native/services/inputflinger/reader/mapper/InputMapper.h

cpp 复制代码

47      inline InputDeviceContext& getDeviceContext() { return mDeviceContext; }
48      inline const std::string getDeviceName() { return mDeviceContext.getName(); }
49      inline InputReaderContext* getContext() { return mDeviceContext.getContext(); }
50      inline InputReaderPolicyInterface* getPolicy() { return getContext()->getPolicy(); }

// getContext 获取的值是 inputreader：：contextimpl 对象，在获取getListener，则是
51      inline InputListenerInterface* getListener() { return getContext()->getListener(); }

=======
/frameworks/native/services/inputflinger/reader/InputReader.cpp

InputListenerInterface* InputReader::ContextImpl::getListener() {

// 获取的是  mQueuedListener
    return mReader->mQueuedListener.get();
}