Linux/Android——Input系统之InputReader (七)

   在前文 Linux/Android——Input系统之frameworks层InputManagerService (六)  这里介绍了android层input服务的启动，其中启动了一个读取来自底层event事件的线程.

而在Linux/Android——input系统之 kernel层 与 frameworks层交互 (五) 有分析到是通过一个event%d的设备文件交互的，也就是说android层是通过读取event%d来获取event的，这个工作就是InputReader

                                              撰写不易,转载需注明出处：http://blog.csdn.net/jscese/article/details/42739197

getEvents:

 这个是运行在inputread线程里面的，上篇有介绍到，字面意思就是获取事件的，实现在/frameworks/base/services/input/EventHub.cpp中，函数很长，列出几个重要的：

size_t EventHub::getEvents(int timeoutMillis, RawEvent* buffer, size_t bufferSize) {

...

    struct input_event readBuffer[bufferSize];

    RawEvent* event = buffer;

...

        if (mNeedToScanDevices) {  //这个在EventHub初始时为true
            mNeedToScanDevices = false;
            scanDevicesLocked();  // 扫描去打开设备，后面跟进去看
            mNeedToSendFinishedDeviceScan = true;  
        }

        while (mOpeningDevices != NULL) {  //这个指针有指向，代表上面打开了某些input设备
            Device* device = mOpeningDevices;    //  初始化一个添加event，type 为DEVICE_ADDED
            ALOGV("Reporting device opened: id=%d, name=%s\n",
                 device->id, device->path.string());
            mOpeningDevices = device->next;
            event->when = now;
            event->deviceId = device->id == mBuiltInKeyboardId ? 0 : device->id;
            event->type = DEVICE_ADDED;
            event += 1;
            mNeedToSendFinishedDeviceScan = true;
            if (--capacity == 0) {
                break;
            }
        }

...

   while (mPendingEventIndex < mPendingEventCount) {  //这个是为处理多个input event 做的一个epoll_event 类型数组
            const struct epoll_event& eventItem = mPendingEventItems[mPendingEventIndex++];

            Device* device = mDevices.valueAt(deviceIndex)  ; // 上面会把打开的device 加入到 这个Vector
            if (eventItem.events & EPOLLIN) {
                int32_t readSize = read(device->fd, readBuffer,   //这个之前有提到过。最终会调用到evdev中的read
                        sizeof(struct input_event) * capacity);

...

       for (size_t i = 0; i < count; i++) {
                        const struct input_event& iev = readBuffer[i];   //这里把上面读到的input_event 转化过这里的RawEvent

     event->deviceId = deviceId;
                        event->type = iev.type;
                        event->code = iev.code;
                        event->value = iev.value;
                        event += 1;

     }

...
   int pollResult = epoll_wait(mEpollFd, mPendingEventItems, EPOLL_MAX_EVENTS, timeoutMillis); //用于等待监测是否有事件可读
...
 }

    // All done, return the number of events we read.
    return event - buffer;   //指针相减，这个数组的元素个数

}

scanDevicesLocked：

这个往下就是打开一个input 设备文件，配置并抽象为一个android层这边的input device：

void EventHub::scanDevicesLocked() {
    status_t res = scanDirLocked(DEVICE_PATH);
    if(res < 0) {
        ALOGE("scan dir failed for %s\n", DEVICE_PATH); //这里的PATH为"/dev/input"
    }
    if (mDevices.indexOfKey(VIRTUAL_KEYBOARD_ID) < 0) {
        createVirtualKeyboardLocked();
    }
}

继续往下看会依次读取目录下的文件，并调用进openDeviceLocked打开，这个函数也比较长，关注几个地方先：

status_t EventHub::openDeviceLocked(const char *devicePath) {
    char buffer[80];

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

    int fd = open(devicePath, O_RDWR | O_CLOEXEC);
    if(fd < 0) {
        ALOGE("could not open %s, %s\n", devicePath, strerror(errno));
        return -1;
    }

...  //  无非是根据打开的fd获取一些相关参数信息

    // Allocate device.  (The device object takes ownership of the fd at this point.)
    int32_t deviceId = mNextDeviceId++;
    Device* device = new Device(fd, deviceId, String8(devicePath), identifier);  //这里根据前面获取的参数new成一个device，算是初步打开完成抽象成一个Device了

...

    // Load the configuration file for the device.
    loadConfigurationLocked(device);   // 这个比较重要  ，加载这个device的配置信息，后面将会根据这个配置来定义规则

... //又是一系列的判断初始化，其中比较重要的就是 device->classes 这个变量，代表了input 设备类型，是键盘，鼠标，触摸屏...

    // Register with epoll.
    struct epoll_event eventItem;   //注册epoll
    memset(&eventItem, 0, sizeof(eventItem));
    eventItem.events = EPOLLIN;
    eventItem.data.u32 = deviceId;
    if (epoll_ctl(mEpollFd, EPOLL_CTL_ADD, fd, &eventItem)) {
        ALOGE("Could not add device fd to epoll instance.  errno=%d", errno);
        delete device;
        return -1;
    }

...

    addDeviceLocked(device);  //添加到 KeyedVector中

}

这个里面有很多原始打印，想深入理解的可以放开调试看看，这里不多做介绍，可以看下 加载配置那个函数loadConfigurationLocked：

void EventHub::loadConfigurationLocked(Device* device) {
    device->configurationFile = getInputDeviceConfigurationFilePathByDeviceIdentifier(   //根据上面获取到的一些设备信息，进一步去找config文件
            device->identifier, INPUT_DEVICE_CONFIGURATION_FILE_TYPE_CONFIGURATION);
    if (device->configurationFile.isEmpty()) {
        ALOGD("No input device configuration file found for device '%s'.",
                device->identifier.name.string());
    } else {
        status_t status = PropertyMap::load(device->configurationFile,  //找到之后 ，把这个device 的config file保存起来
                &device->configuration);
        if (status) {
            ALOGE("Error loading input device configuration file for device '%s'.  "
                    "Using default configuration.",
                    device->identifier.name.string());
        }
    }
}

接下来看怎么找对应config文件的，这里调用到了/frameworks/base/libs/androidfw/InputDevice.cpp中的：

String8 getInputDeviceConfigurationFilePathByDeviceIdentifier(
        const InputDeviceIdentifier& deviceIdentifier,
        InputDeviceConfigurationFileType type) {
    if (deviceIdentifier.vendor !=0 && deviceIdentifier.product != 0) {
        if (deviceIdentifier.version != 0) {
            // Try vendor product version.
            String8 versionPath(getInputDeviceConfigurationFilePathByName(
                    String8::format("Vendor_%04x_Product_%04x_Version_%04x",   //用前面获取的input device 的相关VID PID 来找文件
                            deviceIdentifier.vendor, deviceIdentifier.product,
                            deviceIdentifier.version),
                    type));
            if (!versionPath.isEmpty()) {
                return versionPath;
            }
        }

        // Try vendor product.
        String8 productPath(getInputDeviceConfigurationFilePathByName(
                String8::format("Vendor_%04x_Product_%04x",
                        deviceIdentifier.vendor, deviceIdentifier.product),
                type));
        if (!productPath.isEmpty()) {
            return productPath;
        }
    }

    // Try device name.
    return getInputDeviceConfigurationFilePathByName(deviceIdentifier.name, type);  //这个函数也在同文件中，就是到  path.setTo(getenv("ANDROID_ROOT"));  path.append("/usr/"); 也就是文件系统中/system/usr目录下去找
}

所以我们对一些输出设备需要把它的配置文件编译进系统，而且命名一般都是 Vendor_%04x_Product_%04x.XXX 类型，这里就明白啦！

到这里getEvents应该差不多了，细节部分就需要另行细读代码了，当上面read到事件数组返回之后接下来就是初步处理了！

processEventsLocked：

上面getEvents返回了mEventBuffer之后，做初步的处理：

void InputReader::processEventsLocked(const RawEvent* rawEvents, size_t count) {


    for (const RawEvent* rawEvent = rawEvents; count;) {   遍历获取到的event数组
        int32_t type = rawEvent->type;
        size_t batchSize = 1;



        if (type < EventHubInterface::FIRST_SYNTHETIC_EVENT) {  //如果是常规的event事件
            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
            ALOGW("BatchSize: %d Count: %d", batchSize, count);
//#endif
            processEventsForDeviceLocked(deviceId, rawEvent, batchSize);  //把这次获取到的event数组中属于同一批次的，进一步处理，判定条件就是：常规event以及是属于同一设备
        } else {
            switch (rawEvent->type) {  //这里就是一些特殊的event类型了，上面有说到，打开设备的时候会有这个ADD事件
            case EventHubInterface::DEVICE_ADDED:
                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;   //如果再上面没有处理完event数组中的成员，那么依次继续
        rawEvent += batchSize; 
    }
}

传进来的参数为 前面getEvents一定时间内获取到的event数组以及个数，原型定义在/frameworks/base/services/input/InputReader.h中：

    // The event queue.
    static const int EVENT_BUFFER_SIZE = 256;
    RawEvent mEventBuffer[EVENT_BUFFER_SIZE];

/*
 * A raw event as retrieved from the EventHub.
 */
struct RawEvent {
    nsecs_t when;
    int32_t deviceId;
    int32_t type;
    int32_t code;
    int32_t value;
};

这里可以看到 processEventsLocked 只是对get到的event做一个初步的分发处理，先看添加的事件类型.

可以看到在InputReader里面又来了一次addDeviceLocked  ，这个要更最上面getEvents中往下打开设备时addDeviceLocked 区分开来，不要给绕晕了哟～

void InputReader::addDeviceLocked(nsecs_t when, int32_t deviceId) {
    ssize_t deviceIndex = mDevices.indexOfKey(deviceId);
    if (deviceIndex >= 0) {
        ALOGW("Ignoring spurious device added event for deviceId %d.", deviceId);
        return;
    }

    InputDeviceIdentifier identifier = mEventHub->getDeviceIdentifier(deviceId);  //这里取之前在EventHub中解析出来的设备相关参数
    uint32_t classes = mEventHub->getDeviceClasses(deviceId);  //这个上面有说到，在open设备时 初始化，代表类型

    ALOGW("jscese display in addDeviceLocked classes == 0x%x \n",classes);
    InputDevice* device = createDeviceLocked(deviceId, identifier, classes);  //这里又创建一个 InputDervice，这个就不继续跟进了，会根据classes 选择对应的事件处理map与当前的设备绑定
    device->configure(when, &mConfig, 0);
    device->reset(when);

    if (device->isIgnored()) {
        ALOGI("Device added: id=%d, name='%s' (ignored non-input device)", deviceId,
                identifier.name.string());
    } else {
        ALOGI("Device added: id=%d, name='%s', sources=0x%08x", deviceId,
                identifier.name.string(), device->getSources());
    }

    mDevices.add(deviceId, device); //添加这个input device
    bumpGenerationLocked();
}

看处理平常事件时接下来的处理：

void InputReader::processEventsForDeviceLocked(int32_t deviceId,
        const RawEvent* rawEvents, size_t count) {
    ssize_t deviceIndex = mDevices.indexOfKey(deviceId);
    if (deviceIndex < 0) {
        ALOGW("Discarding event for unknown deviceId %d.", deviceId);
        return;
    }

    InputDevice* device = mDevices.valueAt(deviceIndex); //这里根据id 取出上面添加进去的inputdevice
    if (device->isIgnored()) {
        //ALOGD("Discarding event for ignored deviceId %d.", deviceId);
        return;
    }

    device->process(rawEvents, count); //这里调用了一个process的函数
}

继续看InputDevice的process：

void InputDevice::process(const RawEvent* rawEvents, size_t count) {
    // Process all of the events in order for each mapper.
    // We cannot simply ask each mapper to process them in bulk because mappers may
    // have side-effects that must be interleaved.  For example, joystick movement events and
    // gamepad button presses are handled by different mappers but they should be dispatched
    // in the order received.
    size_t numMappers = mMappers.size();  //这里有个map个数，这个也在上面提到过，在create时 会根据classes类型去匹配处理map，一般都是匹配一个
    for (const RawEvent* rawEvent = rawEvents; count--; rawEvent++) {   //遍历事件数组，依次去处理
#if DEBUG_RAW_EVENTS
        ALOGD("Input event: device=%d type=0x%04x code=0x%04x value=0x%08x when=%lld",
                rawEvent->deviceId, rawEvent->type, rawEvent->code, rawEvent->value,
                rawEvent->when);
#endif

        if (mDropUntilNextSync) {
            if (rawEvent->type == EV_SYN && rawEvent->code == SYN_REPORT) {
                mDropUntilNextSync = false;
#if DEBUG_RAW_EVENTS
                ALOGD("Recovered from input event buffer overrun.");
#endif
            } else {
#if DEBUG_RAW_EVENTS
                ALOGD("Dropped input event while waiting for next input sync.");
#endif
            }
        } else if (rawEvent->type == EV_SYN && rawEvent->code == SYN_DROPPED) {
            ALOGI("Detected input event buffer overrun for device %s.", getName().string());
            mDropUntilNextSync = true;
            reset(rawEvent->when);
        } else {
            for (size_t i = 0; i < numMappers; i++) {
                InputMapper* mapper = mMappers[i];
                mapper->process(rawEvent);  //这里就是调用处理map的process 函数啦
            }
        }
    }
}

多次提到classes 设备类型，看下定义，在EventHub.h中：

/*//classes=0x80000004
 * Input device classes.
 */
enum {
    /* The input device is a keyboard or has buttons. */
    INPUT_DEVICE_CLASS_KEYBOARD      = 0x00000001,

    /* The input device is an alpha-numeric keyboard (not just a dial pad). */
    INPUT_DEVICE_CLASS_ALPHAKEY      = 0x00000002,

    /* The input device is a touchscreen or a touchpad (either single-touch or multi-touch). */
    INPUT_DEVICE_CLASS_TOUCH         = 0x00000004,

    /* The input device is a cursor device such as a trackball or mouse. */
    INPUT_DEVICE_CLASS_CURSOR        = 0x00000008,

    /* The input device is a multi-touch touchscreen. */
    INPUT_DEVICE_CLASS_TOUCH_MT      = 0x00000010,

    /* The input device is a directional pad (implies keyboard, has DPAD keys). */
    INPUT_DEVICE_CLASS_DPAD          = 0x00000020,

    /* The input device is a gamepad (implies keyboard, has BUTTON keys). */
    INPUT_DEVICE_CLASS_GAMEPAD       = 0x00000040,

    /* The input device has switches. */
    INPUT_DEVICE_CLASS_SWITCH        = 0x00000080,

    /* The input device is a joystick (implies gamepad, has joystick absolute axes). */
    INPUT_DEVICE_CLASS_JOYSTICK      = 0x00000100,

    /* The input device has a vibrator (supports FF_RUMBLE). */
    INPUT_DEVICE_CLASS_VIBRATOR      = 0x00000200,

    /* The input device is virtual (not a real device, not part of UI configuration). */
    INPUT_DEVICE_CLASS_VIRTUAL       = 0x40000000,

    /* The input device is external (not built-in). */
    INPUT_DEVICE_CLASS_EXTERNAL      = 0x80000000,
};

那么接下来需要处理的就是 定义的InputReader中的各个InputMap类了。

总结：

这里牵扯到了EventHub     InputReader      Device     InputDevice     InputMap

把关系理一下：

EventHub 中 会创建多个Device  ，这个是根据/dev/input下面的设备文件 一一对应的，也就是kernel中注册的input设备.

InputReader 中会create多个 InputDevice ，这个是由Device中的参数为基础创建的，所以与EventHub中的Device 一一对应.

InputDevice 在创建的时候会根据 classes 来添加需要的InputMap，每一个不同的InputMap 在InputReader中定义，有很多种处理方式.

大体就是这么回事，这里关于InputReader部分就先分析到这里，再往下InputMap中的事件分发处理，后续分析～