Android应用程序键盘（Keyboard）消息处理机制分析（6）

Step 21. EventHub.openDevice
这个函数定义在frameworks/base/libs/ui/EventHub.cpp文件中：

int EventHub::openDevice(const char *deviceName) {
    int version;
    int fd;
    struct pollfd *new_mFDs;
    device_t **new_devices;
    char **new_device_names;
    char name[80];
    char location[80];
    char idstr[80];
    struct input_id id;

    LOGV("Opening device: %s", deviceName);

    AutoMutex _l(mLock);

    fd = open(deviceName, O_RDWR);
    if(fd < 0) {
        LOGE("could not open %s, %s\n", deviceName, strerror(errno));
        return -1;
    }

    ......

    int devid = 0;
    while (devid < mNumDevicesById) {
        if (mDevicesById[devid].device == NULL) {
            break;
        }
        devid++;
    }

    ......

    mDevicesById[devid].seq = (mDevicesById[devid].seq+(1<<SEQ_SHIFT))&SEQ_MASK;
    if (mDevicesById[devid].seq == 0) {
        mDevicesById[devid].seq = 1<<SEQ_SHIFT;
    }

    new_mFDs = (pollfd*)realloc(mFDs, sizeof(mFDs[0]) * (mFDCount + 1));
    new_devices = (device_t**)realloc(mDevices, sizeof(mDevices[0]) * (mFDCount + 1));
    if (new_mFDs == NULL || new_devices == NULL) {
        LOGE("out of memory");
        return -1;
    }
    mFDs = new_mFDs;
    mDevices = new_devices;

    ......

    device_t* device = new device_t(devid|mDevicesById[devid].seq, deviceName, name);
    if (device == NULL) {
        LOGE("out of memory");
        return -1;
    }

    device->fd = fd;
    mFDs[mFDCount].fd = fd;
    mFDs[mFDCount].events = POLLIN;
    mFDs[mFDCount].revents = 0;

    // Figure out the kinds of events the device reports.

    uint8_t key_bitmask[sizeof_bit_array(KEY_MAX + 1)];
    memset(key_bitmask, 0, sizeof(key_bitmask));

    LOGV("Getting keys...");
    if (ioctl(fd, EVIOCGBIT(EV_KEY, sizeof(key_bitmask)), key_bitmask) >= 0) {
        // See if this is a keyboard.  Ignore everything in the button range except for
        // gamepads which are also considered keyboards.
        if (containsNonZeroByte(key_bitmask, 0, sizeof_bit_array(BTN_MISC))
            || containsNonZeroByte(key_bitmask, sizeof_bit_array(BTN_GAMEPAD),
            sizeof_bit_array(BTN_DIGI))
            || containsNonZeroByte(key_bitmask, sizeof_bit_array(KEY_OK),
            sizeof_bit_array(KEY_MAX + 1))) {
                device->classes |= INPUT_DEVICE_CLASS_KEYBOARD;

                device->keyBitmask = new uint8_t[sizeof(key_bitmask)];
                if (device->keyBitmask != NULL) {
                    memcpy(device->keyBitmask, key_bitmask, sizeof(key_bitmask));
                } else {
                    delete device;
                    LOGE("out of memory allocating key bitmask");
                    return -1;
                }
        }
    }

    ......

    if ((device->classes & INPUT_DEVICE_CLASS_KEYBOARD) != 0) {
        char tmpfn[sizeof(name)];
        char keylayoutFilename[300];

        // a more descriptive name
        device->name = name;

        // replace all the spaces with underscores
        strcpy(tmpfn, name);
        for (char *p = strchr(tmpfn, ' '); p && *p; p = strchr(tmpfn, ' '))
            *p = '_';

        // find the .kl file we need for this device
        const char* root = getenv("ANDROID_ROOT");
        snprintf(keylayoutFilename, sizeof(keylayoutFilename),
            "%s/usr/keylayout/%s.kl", root, tmpfn);
        bool defaultKeymap = false;
        if (access(keylayoutFilename, R_OK)) {
            snprintf(keylayoutFilename, sizeof(keylayoutFilename),
                "%s/usr/keylayout/%s", root, "qwerty.kl");
            defaultKeymap = true;
        }
        status_t status = device->layoutMap->load(keylayoutFilename);
        if (status) {
            LOGE("Error %d loading key layout.", status);
        }

        // tell the world about the devname (the descriptive name)
        if (!mHaveFirstKeyboard && !defaultKeymap && strstr(name, "-keypad")) {
            // the built-in keyboard has a well-known device ID of 0,
            // this device better not go away.
            mHaveFirstKeyboard = true;
            mFirstKeyboardId = device->id;
            property_set("hw.keyboards.0.devname", name);
        } else {
            // ensure mFirstKeyboardId is set to -something-.
            if (mFirstKeyboardId == 0) {
                mFirstKeyboardId = device->id;
            }
        }
        char propName[100];
        sprintf(propName, "hw.keyboards.%u.devname", device->id);
        property_set(propName, name);

        // 'Q' key support = cheap test of whether this is an alpha-capable kbd
        if (hasKeycodeLocked(device, AKEYCODE_Q)) {
            device->classes |= INPUT_DEVICE_CLASS_ALPHAKEY;
        }

        // See if this device has a DPAD.
        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;
            }
        }

        LOGI("New keyboard: device->id=0x%x devname='%s' propName='%s' keylayout='%s'\n",
            device->id, name, propName, keylayoutFilename);
    }

    ......

    mDevicesById[devid].device = device;
    device->next = mOpeningDevices;
    mOpeningDevices = device;
    mDevices[mFDCount] = device;

    mFDCount++;
    return 0;
}