static struct input_handler evdev_handler = {

     .event        = evdev_event,

     .events        = evdev_events,

     .connect    = evdev_connect,

     .disconnect    = evdev_disconnect,

     .legacy_minors    = true,

     .minor        = EVDEV_MINOR_BASE,///次设备号从64开始

     .name        = "evdev",

     .id_table    = evdev_ids,

 };

 static int __init evdev_init(void)

 {

     return input_register_handler(&evdev_handler); ///注册 evdev_handler 这个input事件驱动

 }

 int input_register_handler(struct input_handler *handler)///把input 事件驱动注册到内核

 {

     struct input_dev *dev;

     int error;

     error = mutex_lock_interruptible(&input_mutex);

     if (error)

         return error;

     INIT_LIST_HEAD(&handler->h_list);///初始化链表头，把链表的前和后都指向它自己

     list_add_tail(&handler->node, &input_handler_list);///把 handler的 node 加到 input_handler_list这个双向链表，之后就可以通过这个链表访问所有的input_handler

     list_for_each_entry(dev, &input_dev_list, node)
input_attach_handler(dev, handler);////inout 设备和 input 事件进行匹配

     input_wakeup_procfs_readers();

     mutex_unlock(&input_mutex);

     return ;

 }

 static int input_attach_handler(struct input_dev *dev, struct input_handler *handler)

 {

     const struct input_device_id *id;

     int error;

     id = input_match_device(handler, dev);///input_dev 和 input_handler 通过id_table进行匹配

     if (!id)

         return -ENODEV;

     error = handler->connect(handler, dev, id);///如果返回id不为空就执行handler 的 connect  ---> 调用 evdev.c 的 connect 函数

     if (error && error != -ENODEV)

         pr_err("failed to attach handler %s to device %s, error: %d\n",

                handler->name, kobject_name(&dev->dev.kobj), error);

     return error;

 }

 /*

  * Create new evdev device. Note that input core serializes calls

  * to connect and disconnect.

  */

 static int evdev_connect(struct input_handler *handler, struct input_dev *dev,

              const struct input_device_id *id)

 {

     struct evdev *evdev;

     int minor;

     int dev_no;

     int error;

     minor = input_get_new_minor(EVDEV_MINOR_BASE, EVDEV_MINORS, true);//动态分配一个新的设备号minor

     if (minor < ) {

         error = minor;

         pr_err("failed to reserve new minor: %d\n", error);

         return error;

     }

     evdev = kzalloc(sizeof(struct evdev), GFP_KERNEL);///初始化evdev ，为evdev分配空间

     if (!evdev) {

         error = -ENOMEM;

         goto err_free_minor;

     }

     INIT_LIST_HEAD(&evdev->client_list);///初始化队列

     spin_lock_init(&evdev->client_lock);

     mutex_init(&evdev->mutex);

     init_waitqueue_head(&evdev->wait);///初始化等待队列

     evdev->exist = true;

     dev_no = minor;

     /* Normalize device number if it falls into legacy range */

     if (dev_no < EVDEV_MINOR_BASE + EVDEV_MINORS)

         dev_no -= EVDEV_MINOR_BASE;

     dev_set_name(&evdev->dev, "event%d", dev_no);///给设备设置名字(event0、event1、...)

     evdev->handle.dev = input_get_device(dev);

     evdev->handle.name = dev_name(&evdev->dev);

     evdev->handle.handler = handler;

     evdev->handle.private = evdev;

     evdev->dev.devt = MKDEV(INPUT_MAJOR, minor);////根据主设备号(主设备号都是13)和次设备号生成一个设备号(次设备号从64开始)

     evdev->dev.class = &input_class;

     evdev->dev.parent = &dev->dev;

     evdev->dev.release = evdev_free;

     device_initialize(&evdev->dev);///对设备进行初始化

     error = input_register_handle(&evdev->handle);///注册 handle，handle 用来关联 input_dev 和 input_handler

     if (error)

         goto err_free_evdev;

     cdev_init(&evdev->cdev, &evdev_fops);//// 初始化一个 cdev

     evdev->cdev.kobj.parent = &evdev->dev.kobj;

     error = cdev_add(&evdev->cdev, evdev->dev.devt, );

     if (error)

         goto err_unregister_handle;

     error = device_add(&evdev->dev);///把初始化好的 evdev 添加到内核

     if (error)

         goto err_cleanup_evdev;

     return ;

  err_cleanup_evdev:

     evdev_cleanup(evdev);

  err_unregister_handle:

     input_unregister_handle(&evdev->handle);

  err_free_evdev:

     put_device(&evdev->dev);

  err_free_minor:

     input_free_minor(minor);

     return error;

 }