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:
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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
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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。
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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_BASE 64 //evdev的设备次设备起始为64
#define EVDEV_MINORS 32 //最大支持32个设备
#define EVDEV_BUFFER_SIZE 64
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handle
wait_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
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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 evdev
if (!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handle
evdev->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dev
evdev->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。
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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_client
int 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
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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handle
retval = 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
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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。
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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);
else
list_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.
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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code
if (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