Linux输入子系统(3):evdev.c

linux内核中有很多自带的input_handler,其中evdev_handler是做常见的,因为它可以匹配任何的input_dev设备。下面我们就对它做一番简要的介绍

一、evdev注册过程
evdev注册如下:

static struct input_handler evdev_handler = {.event= evdev_event,//当硬件有事件上传将调用.connect= evdev_connect,//当有新的input_dev和它匹配成功时调用(来者不拒).disconnect= evdev_disconnect,.fops= &evdev_fops,//提供读写函数.minor= EVDEV_MINOR_BASE,//次设备起始号.name= "evdev",.id_table= evdev_ids,//它可接受的input_dev条件};static int __init evdev_init(void){return input_register_handler(&evdev_handler);}static void __exit evdev_exit(void){input_unregister_handler(&evdev_handler);}int input_register_handler(struct input_handler *handler){struct input_dev *dev;int retval;retval = mutex_lock_interruptible(&input_mutex);if (retval)return retval;INIT_LIST_HEAD(&handler->h_list);//初始化handler的handle链表头if (handler->fops != NULL) {if (input_table[handler->minor >> 5]) {retval = -EBUSY;goto out;}input_table[handler->minor >> 5] = handler;//将该handler放到input维护的全局input_table数组}list_add_tail(&handler->node, &input_handler_list);//将该handler放到input维护的全局input_handler_list链表list_for_each_entry(dev, &input_dev_list, node)//取出input维护的全局input_dev_list链表input_attach_handler(dev, handler);//找出和新注册的handler匹配的dev设备input_wakeup_procfs_readers(); out:mutex_unlock(&input_mutex);return retval;}

input_attach_handler用来匹配dev和handler

static int input_attach_handler(struct input_dev *dev, struct input_handler *handler){const struct input_device_id *id;int error;if (handler->blacklist && input_match_device(handler->blacklist, dev))//如果dev在handler的黑名单中就直接返回return -ENODEV;id = input_match_device(handler->id_table, dev);//通过handler的id_table来匹配if (!id)return -ENODEV;error = handler->connect(handler, dev, id);//匹配成功就调用handler的connect函数if (error && error != -ENODEV)printk(KERN_ERR"input: failed to attach handler %s to device %s,""error: %d\n",handler->name,kobject_name(&dev->dev.kobj), error);return error;}

在介绍evdev_handler之前先介绍下evdev_handler里面几个重要的数据类型。

在介绍evdev_handler之前先介绍下evdev_handler里面几个重要的数据类型。#define EVDEV_MINOR_BASE64  //evdev的设备次设备起始为64#define EVDEV_MINORS32  //最大支持32个设备#define EVDEV_BUFFER_SIZE64  struct evdev {int exist;//该evdev是否存在,在connect中被赋值int open;//该evdev是否被打开int minor;//次设备号char name[16];struct input_handle handle;//evdev关联的handlewait_queue_head_t wait;//当有应用程序读evdev时,如果没有数据,就在上面睡起struct evdev_client *grab;struct list_head client_list;//evdev管理的evdev_client链表spinlock_t client_lock; /* protects client_list */struct mutex mutex;struct device dev;//设备模型的东东};struct evdev_client {struct input_event buffer[EVDEV_BUFFER_SIZE];//缓冲区大小int head;//环形缓冲区头int tail;//环形缓冲区尾spinlock_t buffer_lock; /* protects access to buffer, head and tail */struct fasync_struct *fasync;struct evdev *evdev;//evdev_client挂靠的单位struct list_head node;//用于将evdev_client挂靠在evdev的client_list链表上};static struct evdev *evdev_table[EVDEV_MINORS];//evdev最多能处理32的设备现在来理下struct input_dev,struct input_handler,struct input_handle,struct evdev,struct evdev_client的关系吧struct input_dev    和一个硬件相关联,主要描述了该硬件支持什么事件,上报事件;struct input_handler主要就提供了设备的操作函数,比如读写等struct input_handle 当input_dev和struct input_handler相匹配的时候就新建一个struct input_handle作为它们的中间人struct evdev        当某个struct input_dev和evdev_handler匹配成功后就新建一个struct evdev,看到这里是不是有点和                       struct input_handle产生的时间一致呀,起始该结构体内部就包含一个struct input_handle;不过结合了                       一些其他信息,可以把它看做是struct input_handle的升级版。struct evdev_client 主要跟应用程序有关.每打开一次设备就新建一个struct evdev_client,里面保存了应用程序要读取的数据                       以及数据的位置。

在dev和handler匹配成功时调用evdev_connect

static int evdev_connect(struct input_handler *handler, struct input_dev *dev,const struct input_device_id *id){struct evdev *evdev;int minor;int error;for (minor = 0; minor < EVDEV_MINORS; minor++)//evdev支持32设备,如果分配使用完就返回if (!evdev_table[minor])break;if (minor == EVDEV_MINORS) {printk(KERN_ERR "evdev: no more free evdev devices\n");return -ENFILE;}evdev = kzalloc(sizeof(struct evdev), GFP_KERNEL);//新建一个struct evdevif (!evdev)return -ENOMEM;INIT_LIST_HEAD(&evdev->client_list);//初始化client_list链表头,代表了有多少应用读写这个evdev设备spin_lock_init(&evdev->client_lock);mutex_init(&evdev->mutex);init_waitqueue_head(&evdev->wait);//初始化等待队列,当evdev没有数据可读时,就在该等待队列上睡眠snprintf(evdev->name, sizeof(evdev->name), "event%d", minor);//设备新产生的设备的名字evdev->exist = 1;evdev->minor = minor;//新产生的evdev分配到的次设备号evdev->handle.dev = input_get_device(dev);//初始化evdev里面的handleevdev->handle.name = evdev->name;evdev->handle.handler = handler;evdev->handle.private = evdev;dev_set_name(&evdev->dev, evdev->name);//初始化evdev里面的devevdev->dev.devt = MKDEV(INPUT_MAJOR, EVDEV_MINOR_BASE + minor);evdev->dev.class = &input_class;evdev->dev.parent = &dev->dev;evdev->dev.release = evdev_free;device_initialize(&evdev->dev);error = input_register_handle(&evdev->handle);//将handle挂靠在dev和handler的链表中if (error)goto err_free_evdev;error = evdev_install_chrdev(evdev);//将新建的evdev放到evdev_table链表中去if (error)goto err_unregister_handle;error = device_add(&evdev->dev);//将该设备加入到linux设备模型中去if (error)goto err_cleanup_evdev;return 0; err_cleanup_evdev:evdev_cleanup(evdev); err_unregister_handle:input_unregister_handle(&evdev->handle); err_free_evdev:put_device(&evdev->dev);return error;}

到这里input_register_handler的注册工作就完成了,就是有几个input_dev需要我,我就建几个evdev来迎合它。

二、应用程序open操作

当我们使用应用程序的open函数打开一个event设备时,通过该设备的主设备号,调用input注册的input_open_file函数
该函数中通过此设备号在input_table数组中找到它的input_handler,然后调用input_handler里面的open函数。

static int evdev_open(struct inode *inode, struct file *file){struct evdev *evdev;struct evdev_client *client;//evdev_open是应用程序open的调用才导致调用的,一个应用程序调用机会新建一个struct evdev_clientint i = iminor(inode) - EVDEV_MINOR_BASE;//根据次设备得到要操作的设备在evdev_table中的下标int error;if (i >= EVDEV_MINORS)return -ENODEV;error = mutex_lock_interruptible(&evdev_table_mutex);if (error)return error;evdev = evdev_table[i];//从evdev_table取出evdev设备if (evdev)get_device(&evdev->dev);mutex_unlock(&evdev_table_mutex);if (!evdev)return -ENODEV;client = kzalloc(sizeof(struct evdev_client), GFP_KERNEL);if (!client) {error = -ENOMEM;goto err_put_evdev;}spin_lock_init(&client->buffer_lock);client->evdev = evdev;//说明client读取的数据来自evdev设备evdev_attach_client(evdev, client);//将client挂靠在evdev的client_list链表中去error = evdev_open_device(evdev);//将evdev设置为打开状态if (error)goto err_free_client;        /*         *应用程序打开一个设备,系统就给它分配struct file *file         *每个应用程序读这个evdev设备,就专门为它分配一个client为它服务         *此处就是将它们关联起来         */file->private_data = client;return 0; err_free_client:evdev_detach_client(evdev, client);kfree(client); err_put_evdev:put_device(&evdev->dev);return error;}

evdev_open中调用evdev_open_device来设置evdev和它的handle的状态

static int evdev_open_device(struct evdev *evdev){int retval;retval = mutex_lock_interruptible(&evdev->mutex);if (retval)return retval;if (!evdev->exist)retval = -ENODEV;else if (!evdev->open++) {//当evdev首次打开,那么就同时打开它的handleretval = input_open_device(&evdev->handle);//将evdev包含的handle也设置为打开状态if (retval)evdev->open--;}mutex_unlock(&evdev->mutex);return retval;}

三、应用程序read操作

当应用程序调用read函数后将导致evdev_read函数被调用

static ssize_t evdev_read(struct file *file, char __user *buffer,size_t count, loff_t *ppos){struct evdev_client *client = file->private_data;//在evdev_open末尾被赋值struct evdev *evdev = client->evdev;//得到应用程序读取数据的设备struct input_event event;int retval;if (count < input_event_size())return -EINVAL;                 /*当client缓冲区无数据;evdev不存在;文件非阻塞打开,那个read直接返回错误*/ if (client->head == client->tail && evdev->exist &&(file->f_flags & O_NONBLOCK))return -EAGAIN;        /*当client里面没有数据时,将应用程序请到evdev->wait休息*/retval = wait_event_interruptible(evdev->wait,client->head != client->tail || !evdev->exist);if (retval)return retval;if (!evdev->exist)return -ENODEV;        /*         *当应用程序读取的数据大于struct input_evevt         *并且client的buffer里面有数据         */while (retval + input_event_size() <= count &&evdev_fetch_next_event(client, &event)) {if (input_event_to_user(buffer + retval, &event))return -EFAULT;retval += input_event_size();}return retval;}static int evdev_fetch_next_event(struct evdev_client *client,struct input_event *event){int have_event;spin_lock_irq(&client->buffer_lock);have_event = client->head != client->tail;//如果client的环形缓冲区不为空,说明有事件if (have_event) {*event = client->buffer[client->tail++];//取出client缓冲区一个事件client->tail &= EVDEV_BUFFER_SIZE - 1;}spin_unlock_irq(&client->buffer_lock);return have_event;}int input_event_to_user(char __user *buffer,const struct input_event *event){if (copy_to_user(buffer, event, sizeof(struct input_event)))//将event事件拷贝到用户空间return -EFAULT;return 0;}

当读取数据的时候,如果client里面没有数据,那么应用程序调用read函数将睡眠,那睡眠什么时候结束呀,当硬件有事件发生时input_dev将调用input_event函数上报事件,在该函数内部将调用和它匹配的input_handler的event函数,在该函数内部将唤醒休眠的数据。

static void evdev_event(struct input_handle *handle,unsigned int type, unsigned int code, int value){struct evdev *evdev = handle->private;//该初始化在evdev_connect,获得handle对应的evdev设备struct evdev_client *client;struct input_event event;do_gettimeofday(&event.time);//初始化事件结构event.type = type;event.code = code;event.value = value;rcu_read_lock();                /*         *如果该evdev有个专用的client,那么就将事件发给它         *如果该evdev不存在专用的client,那个就把该事件发送给evdev上client_list链表上所有的client         */client = rcu_dereference(evdev->grab);if (client)evdev_pass_event(client, &event);elselist_for_each_entry_rcu(client, &evdev->client_list, node)evdev_pass_event(client, &event);rcu_read_unlock();wake_up_interruptible(&evdev->wait);}

四、应用程序write操作

输入子系统一般用来处理硬件输入,但是有些情况比如LED设备需要write操作.

static ssize_t evdev_write(struct file *file, const char __user *buffer,size_t count, loff_t *ppos){struct evdev_client *client = file->private_data;//在evdev_open末尾被赋值struct evdev *evdev = client->evdev;//得到应用程序读取数据的设备struct input_event event;int retval;retval = mutex_lock_interruptible(&evdev->mutex);if (retval)return retval;if (!evdev->exist) {retval = -ENODEV;goto out;}while (retval < count) {if (input_event_from_user(buffer + retval, &event)) {//拷贝应用程序到内核空间retval = -EFAULT;goto out;}input_inject_event(&evdev->handle,event.type, event.code, event.value);retval += input_event_size();} out:mutex_unlock(&evdev->mutex);return retval;}int input_event_from_user(const char __user *buffer,struct input_event *event){if (copy_from_user(event, buffer, sizeof(struct input_event)))//将用户空间的数据拷贝到event里面return -EFAULT;return 0;}void input_inject_event(struct input_handle *handle,unsigned int type, unsigned int code, int value){struct input_dev *dev = handle->dev;//得到将要接受数据的设备struct input_handle *grab;unsigned long flags;if (is_event_supported(type, dev->evbit, EV_MAX)) {//查看将要接受数据的设备是否支持type事件类型spin_lock_irqsave(&dev->event_lock, flags);rcu_read_lock();grab = rcu_dereference(dev->grab);if (!grab || grab == handle)input_handle_event(dev, type, code, value);rcu_read_unlock();spin_unlock_irqrestore(&dev->event_lock, flags);}}static void input_handle_event(struct input_dev *dev,unsigned int type, unsigned int code, int value){int disposition = INPUT_IGNORE_EVENT;switch (type) {..............................................case EV_LED:                /*                 *#define INPUT_PASS_TO_ALL  (INPUT_PASS_TO_HANDLERS | INPUT_PASS_TO_DEVICE)                 *查看设备是否支持EV_LED类型的codeif (is_event_supported(code, dev->ledbit, LED_MAX) &&!!test_bit(code, dev->led) != value) {__change_bit(code, dev->led);//设置dev中记录LED的数组disposition = INPUT_PASS_TO_ALL;//数据传送方向}break;......................}if (disposition != INPUT_IGNORE_EVENT && type != EV_SYN)dev->sync = 0;if ((disposition & INPUT_PASS_TO_DEVICE) && dev->event)dev->event(dev, type, code, value);//调用dev的event函数,用于写设备if (disposition & INPUT_PASS_TO_HANDLERS)input_pass_event(dev, type, code, value);//将数据传送到handler}

相关文章:
Linux输入子系统:input.c实现细节

Linux输入子系统:总体框架

参考文章:
http://blog.csdn.net/yaozhenguo2006/article/details/6775751
http://www.cnitblog.com/luofuchong/archive/2007/11/12/36157.html