openDeviceLocked

识别和匹配idc配置文件

按键映射

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

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

    int fd = open(devicePath, O_RDWR | O_CLOEXEC);/*open()系统调用返回文件描述符，O_RDWR是指以读写方式打开，O_CLOEXEC的作用是百度来的。Linux中，文件描述符有一个属性：CLOEXEC，即当调用exec()函数成功后，文件描述符会自动关闭。在以往的内核版本（2.6.23以前）中，需要调用 fcntl(fd, F_SETFD, FD_CLOEXEC)来设置这个属性。而新版本（2.6.23开始）中，可以在调用open函数的时候，通过 flags 参数设置CLOEXEC 功能，如open(filename, O_CLOEXEC)。*/
    if(fd < 0) {
        ALOGE("could not open %s, %s\n", devicePath, strerror(errno));
        return -1;
    }

　　InputDeviceIdentifier identifier;//input设备标识符
　　struct InputDeviceIdentifier {
　　    inline InputDeviceIdentifier() :
　　            bus(0), vendor(0), product(0), version(0) {
　　    }
　　
　　    // Information provided by the kernel.
　　    String8 name;
　　    String8 location;
　　    String8 uniqueId;//唯一的ID
　　    uint16_t bus;
　　    uint16_t vendor;
　　    uint16_t product;
　　    uint16_t version;
　　
　　    // A composite input device descriptor string that uniquely identifies the device
　　    // even across reboots or reconnections.  The value of this field is used by
　　    // upper layers of the input system to associate settings with individual devices.
　　    // It is hashed from whatever kernel provided information is available.
　　    // Ideally, the way this value is computed should not change between Android releases
　　    // because that would invalidate persistent settings that rely on it.
　　    String8 descriptor;
　　};

    // Get device name.
　　if(ioctl(fd, EVIOCGNAME(sizeof(buffer) - 1), &buffer) < 1) {//input_dev的name，”ft5x06”
        //fprintf(stderr, "could not get device name for %s, %s\n", devicePath, strerror(errno));
    } else {
        buffer[sizeof(buffer) - 1] = '\0';
        identifier.name.setTo(buffer);
    }

　　// Check to see if the device is on our excluded list
　　//检查是不是要排除的device，一般都不是
    for (size_t i = 0; i < mExcludedDevices.size(); i++) {
        const String8& item = mExcludedDevices.itemAt(i);
        if (identifier.name == item) {
            ALOGI("ignoring event id %s driver %s\n", devicePath, item.string());
            close(fd);
            return -1;
        }
    }

    // Get device driver version.
    int driverVersion;
    if(ioctl(fd, EVIOCGVERSION, &driverVersion)) {// 得到EV_VERSION 0x010001
        ALOGE("could not get driver version for %s, %s\n", devicePath, strerror(errno));
        close(fd);
        return -1;
    }

    // Get device identifier.
    struct input_id inputId;
    if(ioctl(fd, EVIOCGID, &inputId)) {//返回struct input_id
        ALOGE("could not get device input id for %s, %s\n", devicePath, strerror(errno));
        close(fd);
        return -1;
    }
    identifier.bus = inputId.bustype;
    identifier.product = inputId.product;
    identifier.vendor = inputId.vendor;
    identifier.version = inputId.version;

    // Get device physical location.
    if(ioctl(fd, EVIOCGPHYS(sizeof(buffer) - 1), &buffer) < 1) {//物理位置，字符串
        //fprintf(stderr, "could not get location for %s, %s\n", devicePath, strerror(errno));
    } else {
        buffer[sizeof(buffer) - 1] = '\0';
        identifier.location.setTo(buffer);
    }

    // Get device unique id.
    if(ioctl(fd, EVIOCGUNIQ(sizeof(buffer) - 1), &buffer) < 1) {//唯一ID，字符串
        //fprintf(stderr, "could not get idstring for %s, %s\n", devicePath, strerror(errno));
    } else {
        buffer[sizeof(buffer) - 1] = '\0';
        identifier.uniqueId.setTo(buffer);
    }

    // Fill in the descriptor.
    setDescriptor(identifier);//设置identifier.descriptor

    // Make file descriptor non-blocking for use with poll().
    if (fcntl(fd, F_SETFL, O_NONBLOCK)) {//设置fd非阻塞
        ALOGE("Error %d making device file descriptor non-blocking.", errno);
        close(fd);
        return -1;
    }

    // Allocate device.  (The device object takes ownership of the fd at this point.)
    int32_t deviceId = mNextDeviceId++;//deviceId=1，mNextDeviceId=2
    Device* device = new Device(fd, deviceId, String8(devicePath), identifier);//一个input device

    ALOGV("add device %d: %s\n", deviceId, devicePath);
    ALOGV("  bus:        %04x\n"
         "  vendor      %04x\n"
         "  product     %04x\n"
         "  version     %04x\n",
        identifier.bus, identifier.vendor, identifier.product, identifier.version);
    ALOGV("  name:       \"%s\"\n", identifier.name.string());
    ALOGV("  location:   \"%s\"\n", identifier.location.string());
    ALOGV("  unique id:  \"%s\"\n", identifier.uniqueId.string());
    ALOGV("  descriptor: \"%s\"\n", identifier.descriptor.string());
    ALOGV("  driver:     v%d.%d.%d\n",
        driverVersion >> 16, (driverVersion >> 8) & 0xff, driverVersion & 0xff);

    // Load the configuration file for the device.
    loadConfigurationLocked(device);
　　/*获取输入设备配置文件，有几个路径，依次找，找到为止
　　// Figure out the kinds of events the device reports.
/*使用EVIOCGBIT ioctl可以获取设备的能力和特性。它告知你设备是否有key或者button。EVIOCGBIT ioctl处理4个参数( ioctl(fd, EVIOCGBIT(ev_type, max_bytes), bitfield))。 ev_type是返回的 type feature( 0是个特殊 case，表示返回设备支持的所有的 type features)。 max_bytes表示返回的最大字节数。bitfield域是指向保存结果的内存指针。return value表示保存结果的实际字节数，如果调用失败，则返回负值。*/
    ioctl(fd, EVIOCGBIT(EV_KEY, sizeof(device->keyBitmask)), device->keyBitmask);
    ioctl(fd, EVIOCGBIT(EV_ABS, sizeof(device->absBitmask)), device->absBitmask);
    ioctl(fd, EVIOCGBIT(EV_REL, sizeof(device->relBitmask)), device->relBitmask);
    ioctl(fd, EVIOCGBIT(EV_SW, sizeof(device->swBitmask)), device->swBitmask);
    ioctl(fd, EVIOCGBIT(EV_LED, sizeof(device->ledBitmask)), device->ledBitmask);
    ioctl(fd, EVIOCGBIT(EV_FF, sizeof(device->ffBitmask)), device->ffBitmask);
    ioctl(fd, EVIOCGPROP(sizeof(device->propBitmask)), device->propBitmask);

    // See if this is a keyboard.  Ignore everything in the button range except for
　　// joystick and gamepad buttons which are handled like keyboards for the most part.
　　/*如果是键盘，除了操纵杆和大部分像键盘一样处理的游戏手柄按钮之外，可以忽略所以的按钮范围*/
    bool haveKeyboardKeys = containsNonZeroByte(device->keyBitmask, 0, sizeof_bit_array(BTN_MISC))
            || containsNonZeroByte(device->keyBitmask, sizeof_bit_array(KEY_OK),
                    sizeof_bit_array(KEY_MAX + 1));
/*
haveKeyboardKeys：上报0~BTN_MISC(100)-1或KEY_OK(160)~KEY_MAX(0x2ff)之间的type。
haveGamepadButtons：上报BTN_MISC~BTN_MOUSE(0x110)-1或BTN_JOYSTICK(0x120)~BTN_DIGI(0x140)的type。
*/
    bool haveGamepadButtons = containsNonZeroByte(device->keyBitmask, sizeof_bit_array(BTN_MISC),
                    sizeof_bit_array(BTN_MOUSE))
            || containsNonZeroByte(device->keyBitmask, sizeof_bit_array(BTN_JOYSTICK),
                    sizeof_bit_array(BTN_DIGI));
    if (haveKeyboardKeys || haveGamepadButtons) {
        device->classes |= INPUT_DEVICE_CLASS_KEYBOARD;/*input外设是一个键盘或者按钮*/
    }

    // See if this is a cursor device such as a trackball or mouse.
    if (test_bit(BTN_MOUSE, device->keyBitmask)
            && test_bit(REL_X, device->relBitmask)
            && test_bit(REL_Y, device->relBitmask)) {
        device->classes |= INPUT_DEVICE_CLASS_CURSOR;//是一个光标，比如轨迹球或鼠标
    }

    // See if this is a touch pad.
    // Is this a new modern multi-touch driver?
    if (test_bit(ABS_MT_POSITION_X, device->absBitmask)
            && test_bit(ABS_MT_POSITION_Y, device->absBitmask)) {
        // Some joysticks such as the PS3 controller report axes that conflict
        // with the ABS_MT range.  Try to confirm that the device really is
        // a touch screen.
        if (test_bit(BTN_TOUCH, device->keyBitmask) || !haveGamepadButtons) {
            device->classes |= INPUT_DEVICE_CLASS_TOUCH | INPUT_DEVICE_CLASS_TOUCH_MT;
        }
    // Is this an old style single-touch driver?
    } else if (test_bit(BTN_TOUCH, device->keyBitmask)
            && test_bit(ABS_X, device->absBitmask)
            && test_bit(ABS_Y, device->absBitmask)) {
        device->classes |= INPUT_DEVICE_CLASS_TOUCH;
    }
/*
(1) 如果是一个touch pad(不透明的触摸板)，还要看它是不是现代的多点触摸driver，所以要看一下有没有report ABS_MT_POSITION_X和ABS_MT_POSITION_Y；多点协议要求的。
(2) 如果是多点上报协议，还要看下是不是操纵杆。比如PS3控制器也会上报坐标轴，这与多点上报 ABS_MT范围是冲突的，所以还要确认一下这个外设确实是触摸屏。怎么看呢？如果上报了BTN_TOUCH那就是touch，如果没有上报BTN_TOUCH，也不是游戏手柄按钮，那也是touch。device->classes |= INPUT_DEVICE_CLASS_TOUCH | INPUT_DEVICE_CLASS_TOUCH_MT。
(3) 如果是老式的单点上报，device->classes |= INPUT_DEVICE_CLASS_TOUCH。
*/
    // See if this device is a joystick.
    // Assumes that joysticks always have gamepad buttons in order to distinguish them
　　// from other devices such as accelerometers that also have absolute axes.
　　//如果这个外设是一个操纵杆。假设它总是有游戏手柄按钮，为了与同样上报绝对坐标的其他外设，比如感应器区分开来，还需要设置INPUT_DEVICE_CLASS_JOYSTICK。
    if (haveGamepadButtons) {
        uint32_t assumedClasses = device->classes | INPUT_DEVICE_CLASS_JOYSTICK;
        for (int i = 0; i <= ABS_MAX; i++) {
            if (test_bit(i, device->absBitmask)
                    && (getAbsAxisUsage(i, assumedClasses) & INPUT_DEVICE_CLASS_JOYSTICK)) {
                device->classes = assumedClasses;
                break;
            }
        }
    }

    // Check whether this device has switches.开关
    for (int i = 0; i <= SW_MAX; i++) {
        if (test_bit(i, device->swBitmask)) {
            device->classes |= INPUT_DEVICE_CLASS_SWITCH;
            break;
        }
    }

    // Check whether this device supports the vibrator.振荡器
    if (test_bit(FF_RUMBLE, device->ffBitmask)) {
        device->classes |= INPUT_DEVICE_CLASS_VIBRATOR;
    }

    // Configure virtual keys.
    if ((device->classes & INPUT_DEVICE_CLASS_TOUCH)) {
        // Load the virtual keys for the touch screen, if any.
        // We do this now so that we can make sure to load the keymap if necessary.
/*如果有的话，为触摸屏load虚拟按键。我们现在这样做，所以可以确保load键映射，如果需要的话。一般虚拟按键都是利用触摸屏的边缘坐标模拟的按键。配置文件名就是/sys/board_properties/virtualkeys.{devicename}，格式为：0x1:扫描码:X:Y:W:H:0x1: ……例如：
0x01:158:55:835:90:55:0x01:139:172:835:125:55:0x01:102:298:835:115:55:0x01:217:412:835:95:55。如果定义了这个配置文件就可以自动把RawInputEvent(原始输入事件)转换为KeyEvent(按键事件)。base/core/java/android/view/inputDevice.java负责处理虚拟按键。要实现虚拟按键还可以在driver中用input_event发送按键消息，往往是这种方式较为常用，尤其是需要校准的电阻屏。
注意：使用虚拟按键转换成为的是按键的扫描码，不是按键码，因此依然需要经过按键布局文件的转化才能得到按键码。我们driver中所用的也是扫描码,例如：KEY_MENU、KEY_BACK。
*/
        status_t status = loadVirtualKeyMapLocked(device);//load虚拟按键配置文件
        if (!status) {
            device->classes |= INPUT_DEVICE_CLASS_KEYBOARD;//支持键盘
        }
    }

    // Load the key map.
　　// We need to do this for joysticks too because the key layout may specify axes.
　　//Load按键映射，我们还需要为操纵杆做这个是因为键盘布局可能是一个指定轴。
    status_t keyMapStatus = NAME_NOT_FOUND;
    if (device->classes & (INPUT_DEVICE_CLASS_KEYBOARD | INPUT_DEVICE_CLASS_JOYSTICK)) {
        // Load the keymap for the device.先找*.kl，再找*.kcm，查找顺序同
        keyMapStatus = loadKeyMapLocked(device);
    }

    // Configure the keyboard, gamepad or virtual keyboard.
    if (device->classes & INPUT_DEVICE_CLASS_KEYBOARD) {
        // Register the keyboard as a built-in keyboard if it is eligible.
//如果有资格注册一个键盘作为嵌入键盘，什么是有资格，就是if的条件了
        if (!keyMapStatus//上一节load keymap失败了
                && mBuiltInKeyboardId == NO_BUILT_IN_KEYBOARD(构造函数是这样初始化的)
                && isEligibleBuiltInKeyboard(device->identifier,
                        device->configuration, &device->keyMap)) {
            mBuiltInKeyboardId = device->id;
        }
/*isEligibleBuiltInKeyboard()成立的条件是：
(1) *.kcm有，type不是SPECIAL_FUNCTION。
(2) 如果idc文件中设置了keyboard.builtIn = true，那(1)+(2)条件成立。
(3) 如果input device的name中含有"-keypad"，那(1)+(3)条件也成立。 
*/
        // 'Q' key support = cheap test of whether this is an alpha-capable kbd
//简单测试下是否有字母功能的键盘文本
        if (hasKeycodeLocked(device, AKEYCODE_Q)) {
            device->classes |= INPUT_DEVICE_CLASS_ALPHAKEY;
        }

        // See if this device has a DPAD.//D-Pad( directional pad)方向键
        if (hasKeycodeLocked(device, AKEYCODE_DPAD_UP) &&
                hasKeycodeLocked(device, AKEYCODE_DPAD_DOWN) &&
                hasKeycodeLocked(device, AKEYCODE_DPAD_LEFT) &&
                hasKeycodeLocked(device, AKEYCODE_DPAD_RIGHT) &&
                hasKeycodeLocked(device, AKEYCODE_DPAD_CENTER)) {
            device->classes |= INPUT_DEVICE_CLASS_DPAD;
        }

        // See if this device has a gamepad.
        for (size_t i = 0; i < sizeof(GAMEPAD_KEYCODES)/sizeof(GAMEPAD_KEYCODES[0]); i++) {
            if (hasKeycodeLocked(device, GAMEPAD_KEYCODES[i])) {
                device->classes |= INPUT_DEVICE_CLASS_GAMEPAD;
                break;
            }
        }

        // Disable kernel key repeat since we handle it ourselves
//失能 kernel key repeat，因为我们除了它
        unsigned int repeatRate[] = {0,0};
        if (ioctl(fd, EVIOCSREP, repeatRate)) {
            ALOGW("Unable to disable kernel key repeat for %s: %s", devicePath, strerror(errno));
        }
    }

　　// If the device isn't recognized as something we handle, don't monitor it.
　　//如果device没有被识别为我们可以处理的东西，就不要监视它了
    if (device->classes == 0) {
        ALOGV("Dropping device: id=%d, path='%s', name='%s'",
                deviceId, devicePath, device->identifier.name.string());
        delete device;
        return -1;
    }

　　// Determine whether the device is external or internal.
　　//确定是内部设备还是外部设备
    if (isExternalDeviceLocked(device)) {
        device->classes |= INPUT_DEVICE_CLASS_EXTERNAL;
    }
　　(1) 如果idc配置文件中，device.internal = true，就直接是内部设备了。
　　(2) 如果device.internal 没有写，要看input device的bus，如果是BUS_USB或者BUS_BLUETOOTH就是外部设备。 
    // Register with epoll.
    struct epoll_event eventItem;
    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;
    }
/*又添加了一个epoll事件，这次是要查询/dev/input/eventx是否可读。
*/
    // Enable wake-lock behavior on kernels that support it.
    // TODO: Only need this for devices that can really wake the system.
    bool usingSuspendBlockIoctl;
    char value[8];
    property_get("ro.platform.has.mbxuimode", value, "false");
    if(strcmp(value, "true") == 0) {
        usingSuspendBlockIoctl = !ioctl(fd, EVIOCSSUSPENDBLOCK, 0);//失能
    } else {
        usingSuspendBlockIoctl = !ioctl(fd, EVIOCSSUSPENDBLOCK, 1);//使能
    }
/*int property_get(const char *key, char *value, const char *default_value);
失能时，到kernel调用evdev_disable_suspend_block()->
　　client->use_wake_lock = false;
　　wake_lock_destroy(&client->wake_lock);
使能时调用evdev_enable_suspend_block()->
	wake_lock_init(&client->wake_lock, WAKE_LOCK_SUSPEND, client->name);
	client->use_wake_lock = true;
	if (client->packet_head != client->tail)
这时候是上锁，什么时候解锁呢？循环buffer首尾相接的时候。
	if (unlikely(client->head == client->tail)) {
		if (client->use_wake_lock)
			wake_unlock(&client->wake_lock);
　　}
	if (client->use_wake_lock &&
		client->packet_head == client->tail)
		wake_unlock(&client->wake_lock);
*/
    // Tell the kernel that we want to use the monotonic clock for reporting timestamps
    // associated with input events.  This is important because the input system
    // uses the timestamps extensively and assumes they were recorded using the monotonic
    // clock.
/*通知kernel我们想用monotonic(单调递增)时钟作为input events的报告时间戳，这是非常重要的，假设input system用monotonic时钟记录时间戳，时间戳的应用非常广泛。
    // In older kernel, before Linux 3.4, there was no way to tell the kernel which
    // clock to use to input event timestamps.  The standard kernel behavior was to
    // record a real time timestamp, which isn't what we want.  Android kernels therefore
    // contained a patch to the evdev_event() function in drivers/input/evdev.c to
    // replace the call to do_gettimeofday() with ktime_get_ts() to cause the monotonic
    // clock to be used instead of the real time clock.
/*在Linux 3.4之前的内核中，没有办法通知kernel用哪种时钟作为input系统的时间戳。标准内核行为是记录real(实时)时间的时间戳，这个时间并不是我们想要的。因此，android内核包含一个对drivers/input/evdev.c中evdev_event()函数的patch，用ktime_get_ts()取代 do_gettimeofday()，从而实现monotonic时钟代替real time时钟。
*/  
    // As of Linux 3.4, there is a new EVIOCSCLOCKID ioctl to set the desired clock.
    // Therefore, we no longer require the Android-specific kernel patch described above
　　// as long as we make sure to set select the monotonic clock.  We do that here.
/*从Linux 3.4开始，出现了新的EVIOCSCLOCKID EVIOCSCLOCKID来设置期望的时钟。因此，我们不再需要android特殊的内核patch，综上所述，只有我们确定需要设置 monotonic clock，就执行下列代码。
*/
    int clockId = CLOCK_MONOTONIC;
    bool usingClockIoctl = !ioctl(fd, EVIOCSCLOCKID, &clockId);
    ALOGI("New device: id=%d, fd=%d, path='%s', name='%s', classes=0x%x, "
            "configuration='%s', keyLayout='%s', keyCharacterMap='%s', builtinKeyboard=%s, "
            "usingSuspendBlockIoctl=%s, usingClockIoctl=%s",
         deviceId, fd, devicePath, device->identifier.name.string(),
         device->classes,
         device->configurationFile.string(),
         device->keyMap.keyLayoutFile.string(),
         device->keyMap.keyCharacterMapFile.string(),
         toString(mBuiltInKeyboardId == deviceId),
         toString(usingSuspendBlockIoctl), toString(usingClockIoctl));

    addDeviceLocked(device);
    return 0;
}
void EventHub::addDeviceLocked(Device* device) {
    mDevices.add(device->id, device);
    device->next = mOpeningDevices;
    mOpeningDevices = device;
}
//KeyedVector.add()添加一个键值对，最后通过device->id就能找到device。
//通过mOpeningDevices可以找到我们第一open的设备，一直next下去，所以open的都找到了。