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Android Input系统3　InputReader线程

2021-02-05 23:57:56 作者：互联网

一　InputReader起点

上一篇文章Android Input系统2　输入系统启动，介绍IMS服务的启动过程会创建两个native线程，分别是InputReader,InputDispatcher. 接下来从InputReader线程的执行过程从threadLoop为起点开始分析。

1.1 threadLoop

InputReader.cpp

bool InputReaderThread::threadLoop() {
    mReader->loopOnce();
    return true;
}

threadLoop返回值true代表的是会不断地循环调用loopOnce()。另外，如果当返回值为false则会退出循环。整个过程是不断循环的地调用InputReader的loopOnce()方法，先来回顾一下InputReader对象构造方法。

1.2 loopOnce

InputReader.cpp

void InputReader::loopOnce() {
    ...
    {
        AutoMutex _l(mLock);
        uint32_t changes = mConfigurationChangesToRefresh;
        if (changes) {
            timeoutMillis = 0;
            ...
        } else if (mNextTimeout != LLONG_MAX) {
            nsecs_t now = systemTime(SYSTEM_TIME_MONOTONIC);
            timeoutMillis = toMillisecondTimeoutDelay(now, mNextTimeout);
        }
    }

    //从EventHub读取事件，其中EVENT_BUFFER_SIZE = 256【见小节2.1】
    size_t count = mEventHub->getEvents(timeoutMillis, mEventBuffer, EVENT_BUFFER_SIZE);

    { // acquire lock
        AutoMutex _l(mLock);
         mReaderIsAliveCondition.broadcast();
        if (count) { //处理事件【见小节3.1】
            processEventsLocked(mEventBuffer, count);
        }
        if (oldGeneration != mGeneration) {
            inputDevicesChanged = true;
            getInputDevicesLocked(inputDevices);
        }
        ...
    } // release lock


    if (inputDevicesChanged) { //输入设备发生改变
        mPolicy->notifyInputDevicesChanged(inputDevices);
    }
    //发送事件到nputDispatcher【见小节4.1】
    mQueuedListener->flush();
}

二　EventHub

2.1 getEvents

EventHub.cpp

size_t EventHub::getEvents(int timeoutMillis, RawEvent* buffer, size_t bufferSize) {
    AutoMutex _l(mLock); //加锁

    struct input_event readBuffer[bufferSize];
    RawEvent* event = buffer; //原始事件
    size_t capacity = bufferSize; //容量大小为256
    bool awoken = false;
    for (;;) {
        nsecs_t now = systemTime(SYSTEM_TIME_MONOTONIC);
        ...

        if (mNeedToScanDevices) {
            mNeedToScanDevices = false;
            scanDevicesLocked(); //扫描设备【见小节2.2】
            mNeedToSendFinishedDeviceScan = true;
        }

        while (mOpeningDevices != NULL) {
            Device* device = mOpeningDevices;
            mOpeningDevices = device->next;
            event->when = now;
            event->deviceId = device->id == mBuiltInKeyboardId ? 0 : device->id;
            event->type = DEVICE_ADDED; //添加设备的事件
            event += 1;
            mNeedToSendFinishedDeviceScan = true;
            if (--capacity == 0) {
                break;
            }
        }
        ...

        bool deviceChanged = false;
        while (mPendingEventIndex < mPendingEventCount) {
            //从mPendingEventItems读取事件项
            const struct epoll_event& eventItem = mPendingEventItems[mPendingEventIndex++];
            ...
            //获取设备ID所对应的device
            ssize_t deviceIndex = mDevices.indexOfKey(eventItem.data.u32);
            Device* device = mDevices.valueAt(deviceIndex);
            if (eventItem.events & EPOLLIN) {
                //从设备不断读取事件，放入到readBuffer
                int32_t readSize = read(device->fd, readBuffer,
                        sizeof(struct input_event) * capacity);

                if (readSize == 0 || (readSize < 0 && errno == ENODEV)) {
                    deviceChanged = true;
                    closeDeviceLocked(device);//设备已被移除则执行关闭操作
                } else if (readSize < 0) {
                    ...
                } else if ((readSize % sizeof(struct input_event)) != 0) {
                    ...
                } else {
                    int32_t deviceId = device->id == mBuiltInKeyboardId ? 0 : device->id;
                    size_t count = size_t(readSize) / sizeof(struct input_event);

                    for (size_t i = 0; i < count; i++) {
                        //获取readBuffer的数据
                        struct input_event& iev = readBuffer[i];
                        //将input_event信息, 封装成RawEvent
                        event->when = nsecs_t(iev.time.tv_sec) * 1000000000LL
                                + nsecs_t(iev.time.tv_usec) * 1000LL;
                        event->deviceId = deviceId;
                        event->type = iev.type;
                        event->code = iev.code;
                        event->value = iev.value;
                        event += 1;
                        capacity -= 1;
                    }
                    if (capacity == 0) {
                        mPendingEventIndex -= 1;
                        break;
                    }
                }
            }
            ...
        }
        ...
        mLock.unlock(); //poll之前先释放锁
        //等待input事件的到来
        int pollResult = epoll_wait(mEpollFd, mPendingEventItems, EPOLL_MAX_EVENTS, timeoutMillis);
        ...
        mLock.lock(); //poll之后再次请求锁

        if (pollResult < 0) { //出现错误
            mPendingEventCount = 0;
            if (errno != EINTR) {
                usleep(100000); //系统发生错误则休眠1s
            }
        } else {
            mPendingEventCount = size_t(pollResult);
        }
    }

    return event - buffer; //返回所读取的事件个数
}

EventHub采用INotify + epoll机制实现监听目录/dev/input下的设备节点，经过EventHub将input_event结构体 + deviceId 转换成RawEvent结构体，如下：

2.1.1 RawEvent

InputEventReader.h

struct input_event {
 struct timeval time; //事件发生的时间点
 __u16 type;
 __u16 code;
 __s32 value;
};

struct RawEvent {
    nsecs_t when; //事件发生的时间店
    int32_t deviceId; //产生事件的设备Id
    int32_t type; // 事件类型
    int32_t code;
    int32_t value;
};

此处事件类型：

DEVICE_ADDED(添加)
DEVICE_REMOVED(删除)
FINISHED_DEVICE_SCAN(扫描完成)
type<FIRST_SYNTHETIC_EVENT(其他事件)

getEvents()已完成转换事件转换工作, 接下来,顺便看看设备扫描过程。

2.2 设备扫描

2.2.1 scanDevicesLocked

void EventHub::scanDevicesLocked() {
    //此处DEVICE_PATH="/dev/input"【见小节2.3】
    status_t res = scanDirLocked(DEVICE_PATH);
    ...
}

2.2.2 scanDirLocked

status_t EventHub::scanDirLocked(const char *dirname)
{
    char devname[PATH_MAX];
    char *filename;
    DIR *dir;
    struct dirent *de;
    dir = opendir(dirname);

    strcpy(devname, dirname);
    filename = devname + strlen(devname);
    *filename++ = '/';
    //读取/dev/input/目录下所有的设备节点
    while((de = readdir(dir))) {
        if(de->d_name[0] == '.' &&
           (de->d_name[1] == '\0' ||
            (de->d_name[1] == '.' && de->d_name[2] == '\0')))
            continue;
        strcpy(filename, de->d_name);
        //打开相应的设备节点【2.2.3】
        openDeviceLocked(devname);
    }
    closedir(dir);
    return 0;
}

2.2.3 openDeviceLocked

status_t EventHub::openDeviceLocked(const char *devicePath) {
    char buffer[80];
    //打开设备文件
    int fd = open(devicePath, O_RDWR | O_CLOEXEC);
    InputDeviceIdentifier identifier;
    //获取设备名
    if(ioctl(fd, EVIOCGNAME(sizeof(buffer) - 1), &buffer) < 1){
    } else {
        buffer[sizeof(buffer) - 1] = '\0';
        identifier.name.setTo(buffer);
    }

    identifier.bus = inputId.bustype;
    identifier.product = inputId.product;
    identifier.vendor = inputId.vendor;
    identifier.version = inputId.version;

    //获取设备物理地址
    if(ioctl(fd, EVIOCGPHYS(sizeof(buffer) - 1), &buffer) < 1) {
    } else {
        buffer[sizeof(buffer) - 1] = '\0';
        identifier.location.setTo(buffer);
    }

    //获取设备唯一ID
    if(ioctl(fd, EVIOCGUNIQ(sizeof(buffer) - 1), &buffer) < 1) {
    } else {
        buffer[sizeof(buffer) - 1] = '\0';
        identifier.uniqueId.setTo(buffer);
    }
    //将identifier信息填充到fd
    assignDescriptorLocked(identifier);
    //设置fd为非阻塞方式
    fcntl(fd, F_SETFL, O_NONBLOCK);

    //获取设备ID，分配设备对象内存
    int32_t deviceId = mNextDeviceId++;
    Device* device = new Device(fd, deviceId, String8(devicePath), identifier);
    ...

    //注册epoll
    struct epoll_event eventItem;
    memset(&eventItem, 0, sizeof(eventItem));
    eventItem.events = EPOLLIN;
    if (mUsingEpollWakeup) {
        eventItem.events |= EPOLLWAKEUP;
    }
    eventItem.data.u32 = deviceId;
    if (epoll_ctl(mEpollFd, EPOLL_CTL_ADD, fd, &eventItem)) {
        delete device; //添加失败则删除该设备
        return -1;
    }
    ...
    //【见小节2.2.4】
    addDeviceLocked(device);
}

2.2.4 addDeviceLocked

void EventHub::addDeviceLocked(Device* device) {
    mDevices.add(device->id, device); //添加到mDevices队列
    device->next = mOpeningDevices;
    mOpeningDevices = device;
}

介绍了EventHub从设备节点获取事件的流程，当收到事件后接下里便开始处理事件。

三　InputReader

3.1 processEventsLocked

InputReader.cpp

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; //同一设备的事件打包处理
            }
            //数据事件的处理【见小节3.3】
            processEventsForDeviceLocked(deviceId, rawEvent, batchSize);
        } else {
            switch (rawEvent->type) {
            case EventHubInterface::DEVICE_ADDED:
                //设备添加【见小节3.2】
                addDeviceLocked(rawEvent->when, rawEvent->deviceId);
                break;
            case EventHubInterface::DEVICE_REMOVED:
                //设备移除
                removeDeviceLocked(rawEvent->when, rawEvent->deviceId);
                break;
            case EventHubInterface::FINISHED_DEVICE_SCAN:
                //设备扫描完成
                handleConfigurationChangedLocked(rawEvent->when);
                break;
            default:
                ALOG_ASSERT(false);//不会发生
                break;
            }
        }
        count -= batchSize;
        rawEvent += batchSize;
    }
}

事件处理总共有下几类类型：

DEVICE_ADDED(设备增加), [见小节3.2]
DEVICE_REMOVED(设备移除)
FINISHED_DEVICE_SCAN(设备扫描完成)
数据事件[见小节3.4]
先来说说DEVICE_ADDED设备增加的过程。

3.2 设备增加

3.2.1 addDeviceLocked

void InputReader::addDeviceLocked(nsecs_t when, int32_t deviceId) {
    ssize_t deviceIndex = mDevices.indexOfKey(deviceId);
    if (deviceIndex >= 0) {
        return; //已添加的相同设备则不再添加
    }

    InputDeviceIdentifier identifier = mEventHub->getDeviceIdentifier(deviceId);
    uint32_t classes = mEventHub->getDeviceClasses(deviceId);
    int32_t controllerNumber = mEventHub->getDeviceControllerNumber(deviceId);
    //【见小节3.2.2】
    InputDevice* device = createDeviceLocked(deviceId, controllerNumber, identifier, classes);
    device->configure(when, &mConfig, 0);
    device->reset(when);
    mDevices.add(deviceId, device); //添加设备到mDevices
    ...
}

3.2.2 createDeviceLocked

InputDevice* InputReader::createDeviceLocked(int32_t deviceId, int32_t controllerNumber,
        const InputDeviceIdentifier& identifier, uint32_t classes) {
    //创建InputDevice对象
    InputDevice* device = new InputDevice(&mContext, deviceId, bumpGenerationLocked(),
            controllerNumber, identifier, classes);
    ...

    //获取键盘源类型
    uint32_t keyboardSource = 0;
    int32_t keyboardType = AINPUT_KEYBOARD_TYPE_NON_ALPHABETIC;
    if (classes & INPUT_DEVICE_CLASS_KEYBOARD) {
        keyboardSource |= AINPUT_SOURCE_KEYBOARD;
    }
    if (classes & INPUT_DEVICE_CLASS_ALPHAKEY) {
        keyboardType = AINPUT_KEYBOARD_TYPE_ALPHABETIC;
    }
    if (classes & INPUT_DEVICE_CLASS_DPAD) {
        keyboardSource |= AINPUT_SOURCE_DPAD;
    }
    if (classes & INPUT_DEVICE_CLASS_GAMEPAD) {
        keyboardSource |= AINPUT_SOURCE_GAMEPAD;
    }

    //添加键盘类设备InputMapper
    if (keyboardSource != 0) {
        device->addMapper(new KeyboardInputMapper(device, keyboardSource, keyboardType));
    }

    //添加鼠标类设备InputMapper
    if (classes & INPUT_DEVICE_CLASS_CURSOR) {
        device->addMapper(new CursorInputMapper(device));
    }

    //添加触摸屏设备InputMapper
    if (classes & INPUT_DEVICE_CLASS_TOUCH_MT) {
        device->addMapper(new MultiTouchInputMapper(device));
    } else if (classes & INPUT_DEVICE_CLASS_TOUCH) {
        device->addMapper(new SingleTouchInputMapper(device));
    }
    ...
    return device;
}

该方法主要功能：

创建InputDevice对象，将InputReader的mContext赋给InputDevice对象所对应的变量
根据设备类型来创建并添加相对应的InputMapper，同时设置mContext.
input设备类型有很多种，以上代码只列举部分常见的设备以及相应的InputMapper：

键盘类设备：KeyboardInputMapper
触摸屏设备：MultiTouchInputMapper或SingleTouchInputMapper
鼠标类设备：CursorInputMapper
介绍完设备增加过程，继续回到[小节3.1]除了设备的增删，更常见事件便是数据事件，那么接下来介绍数据事件的处理过程。

3.3 事件处理

3.3.1 processEventsForDeviceLocked

void InputReader::processEventsForDeviceLocked(int32_t deviceId,
        const RawEvent* rawEvents, size_t count) {
    ssize_t deviceIndex = mDevices.indexOfKey(deviceId);
    ...

    InputDevice* device = mDevices.valueAt(deviceIndex);
    if (device->isIgnored()) {
        return; //可忽略则直接返回
    }
    //【见小节3.3.2】
    device->process(rawEvents, count);
}

标签：buffer,DEVICE,线程,deviceId,device,Input,Android,event,设备
来源： https://blog.csdn.net/liuwg1226/article/details/113705725

Android Input系统3 InputReader线程

一 InputReader起点

1.1 threadLoop

1.2 loopOnce

二 EventHub

2.1 getEvents

2.1.1 RawEvent

2.2 设备扫描

2.2.1 scanDevicesLocked

2.2.2 scanDirLocked

2.2.3 openDeviceLocked

2.2.4 addDeviceLocked

三 InputReader

3.1 processEventsLocked

3.2 设备增加

3.2.1 addDeviceLocked

3.2.2 createDeviceLocked

3.3 事件处理

3.3.1 processEventsForDeviceLocked

Android Input系统3　InputReader线程

一　InputReader起点

二　EventHub

三　InputReader