Linux驱动修炼之道-INPUT子系统(下)
2015-06-29 11:51
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努力成为linux kernel hacker的人李万鹏原创作品，为梦而战。转载请标明出处
http://blog.csdn.net/woshixingaaa/archive/2011/05/19/6433337.aspx
input子系统最重要的部分就是向上层report了。这里还是先介绍几个数据结构：
C-sharp代码
struct input_event {
struct timeval time; //事件发生的时间
__u16 type; //事件类型
__u16 code; //子事件
__s32 value; //事件的value
};
C-sharp代码
struct evdev_client {
struct input_event buffer[EVDEV_BUFFER_SIZE]; //可以同时管理EVDEV_BUFFER_SIZE(64)个事件
int head; //存储事件从head开始
int tail; //取出事件从tail开始
spinlock_t buffer_lock; /* protects access to buffer, head and tail */
struct fasync_struct *fasync; //异步通知事件发生
struct evdev *evdev; //指向本evdev_client归属的evdev
struct list_head node; //用于挂载到evdev的链表头client_list上
};
C-sharp代码
static struct input_handler evdev_handler = {
.event = evdev_event,
.connect = evdev_connect,
.disconnect = evdev_disconnect,
.fops = &evdev_fops,
.minor = EVDEV_MINOR_BASE,
.name = "evdev",
.id_table = evdev_ids,
};
这里的次设备号是EVDEV_MINOR_BASE(64)，也就是说evdev_handler所表示的设备文件范围(13,64)~(13,64+32)。
如下一个结构体:evdev_handler匹配所有设备。
C-sharp代码
static const struct input_device_id evdev_ids[] = {
{ .driver_info = 1 }, /* Matches all devices */
{ }, /* Terminating zero entry */
};
这个是evdev_handler是fops，下面的讲解中会用到其中的open,read函数。
C-sharp代码
static const struct file_operations evdev_fops = {
.owner = THIS_MODULE,
.read = evdev_read,
.write = evdev_write,
.poll = evdev_poll,
.open = evdev_open,
.release = evdev_release,
.unlocked_ioctl = evdev_ioctl,
#ifdef CONFIG_COMPAT
.compat_ioctl = evdev_ioctl_compat,
#endif
.fasync = evdev_fasync,
.flush = evdev_flush
};
在驱动程序中我们会调用input_report_abs等函数：
C-sharp代码
static inline void input_report_abs(struct input_dev *dev, unsigned int code, int value)
{
input_event(dev, EV_ABS, code, value);
}
跟踪input_event如下：
C-sharp代码
void input_event(struct input_dev *dev,
unsigned int type, unsigned int code, int value)
{
unsigned long flags;
if (is_event_supported(type, dev->evbit, EV_MAX)) {
spin_lock_irqsave(&dev->event_lock, flags);
/*利用输入值调正随机数产生器*/
add_input_randomness(type, code, value);
input_handle_event(dev, type, code, value);
spin_unlock_irqrestore(&dev->event_lock, flags);
}
}
跟踪input_handle_event如下：
C-sharp代码
static void input_handle_event(struct input_dev *dev,
unsigned int type, unsigned int code, int value)
{
int disposition = INPUT_IGNORE_EVENT;
switch (type) {
。。。。。。。。。。。。。。。。
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);
if (disposition & INPUT_PASS_TO_HANDLERS)
input_pass_event(dev, type, code, value);
}
如果该事件需要input device来完成，就会将disposition设置成INPUT_PASS_TO_DEVICE，如果需要input handler来完成，就会将disposition设置成INPUT_PASS_TO_DEVICE，如果需要两者都参与，则将disposition设置成INPUT_PASS_TO_ALL。
跟踪input_pass_event如下：
C-sharp代码
static void input_pass_event(struct input_dev *dev,
unsigned int type, unsigned int code, int value)
{
struct input_handle *handle;
rcu_read_lock();
/**/
handle = rcu_dereference(dev->grab);
if (handle)
/*如果input_dev的grab指向了一个handle，就用这个handle关联的handler的event，否则遍历整个挂在input_dev的h_list上的handle关联的handler*/
handle->handler->event(handle, type, code, value);
else
list_for_each_entry_rcu(handle, &dev->h_list, d_node)
if (handle->open)
handle->handler->event(handle,
type, code, value);
rcu_read_unlock();
}
比如下边的evdev_handler的evdev_event：
C-sharp代码
static void evdev_event(struct input_handle *handle,
unsigned int type, unsigned int code, int value)
{
struct evdev *evdev = handle->private;
struct evdev_client *client;
struct input_event event;
do_gettimeofday(&event.time);
event.type = type;
event.code = code;
event.value = value;
rcu_read_lock();
client = rcu_dereference(evdev->grab);
if (client)
/*如果evdev->grab指向一个当前使用的client就将event放到这个client的buffer中，否则放到整个client_list上的client的链表中*/
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);
}
C-sharp代码
static void evdev_pass_event(struct evdev_client *client,
struct input_event *event)
{
/*
* Interrupts are disabled, just acquire the lock
*/
spin_lock(&client->buffer_lock);
/*将event装入client的buffer中，buffer是一个环形缓存区*/
client->buffer[client->head++] = *event;
client->head &= EVDEV_BUFFER_SIZE - 1;
spin_unlock(&client->buffer_lock);
kill_fasync(&client->fasync, SIGIO, POLL_IN);
}
这里总结一下事件的传递过程：首先在驱动层中，调用inport_report_abs，然后他调用了input core层的input_event，input_event调用了input_handle_event对事件进行分派，调用input_pass_event，在这里他会把事件传递给具体的handler层，然后在相应handler的event处理函数中，封装一个event，然后把它投入evdev的那个client_list上的client的事件buffer中，等待用户空间来读取。
下边看一下用户程序打开文件时的过程，首先调用了input_open_file:
C-sharp代码
static int input_open_file(struct inode *inode, struct file *file)
{
struct input_handler *handler;
const struct file_operations *old_fops, *new_fops = NULL;
int err;
lock_kernel();
/* No load-on-demand here? */
/*因为32个input_dev公共一个handler所以低5位应该是相同的*/
handler = input_table[iminor(inode) >> 5];
if (!handler || !(new_fops = fops_get(handler->fops))) {
err = -ENODEV;
goto out;
}
/*
* That's _really_ odd. Usually NULL ->open means "nothing special",
* not "no device". Oh, well...
*/
if (!new_fops->open) {
fops_put(new_fops);
err = -ENODEV;
goto out;
}
/*保存以前的fops，使用相应的handler的fops*/
old_fops = file->f_op;
file->f_op = new_fops;
err = new_fops->open(inode, file);
if (err) {
fops_put(file->f_op);
file->f_op = fops_get(old_fops);
}
fops_put(old_fops);
out:
unlock_kernel();
return err;
}
这里还是假设handler是evdev_handler。
C-sharp代码
static int evdev_open(struct inode *inode, struct file *file)
{
struct evdev *evdev;
struct evdev_client *client;
/*因为次设备号是从EVDEV_MINOR_BASE开始的*/
int i = iminor(inode) - EVDEV_MINOR_BASE;
int error;
if (i >= EVDEV_MINORS)
return -ENODEV;
error = mutex_lock_interruptible(&evdev_table_mutex);
if (error)
return error;
/*evdev_table一共可容纳32个成员，找到次设备号对应的那个*/
evdev = evdev_table[i];
if (evdev)
get_device(&evdev->dev);
mutex_unlock(&evdev_table_mutex);
if (!evdev)
return -ENODEV;
/*打开的时候创建一个client*/
client = kzalloc(sizeof(struct evdev_client), GFP_KERNEL);
if (!client) {
error = -ENOMEM;
goto err_put_evdev;
}
spin_lock_init(&client->buffer_lock);
/*下边两句的作用就是将evdev和client绑定到一起*/
client->evdev = evdev;
evdev_attach_client(evdev, client);
error = evdev_open_device(evdev);
if (error)
goto err_free_client;
/*将file->private_data指向刚刚建的client，后边会用到的*/
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;
}
C-sharp代码
static int evdev_open_device(struct evdev *evdev)
{
int retval;
retval = mutex_lock_interruptible(&evdev->mutex);
if (retval)
return retval;
/*如果设备不存在，返回错误*/
if (!evdev->exist)
retval = -ENODEV;
/*如果是被第一次打开，则调用input_open_device*/
else if (!evdev->open++) {
retval = input_open_device(&evdev->handle);
if (retval)
evdev->open--;
}
mutex_unlock(&evdev->mutex);
return retval;
}
C-sharp代码
int input_open_device(struct input_handle *handle)
{
struct input_dev *dev = handle->dev;
int retval;
retval = mutex_lock_interruptible(&dev->mutex);
if (retval)
return retval;
if (dev->going_away) {
retval = -ENODEV;
goto out;
}
handle->open++;
if (!dev->users++ && dev->open)
retval = dev->open(dev);
if (retval) {
dev->users--;
if (!--handle->open) {
/*
* Make sure we are not delivering any more events
* through this handle
*/
synchronize_rcu();
}
}
out:
mutex_unlock(&dev->mutex);
return retval;
}
下面是用户进程读取event的底层实现：
C-sharp代码
static ssize_t evdev_read(struct file *file, char __user *buffer,
size_t count, loff_t *ppos)
{
/*这个就是刚才在open函数中*/
struct evdev_client *client = file->private_data;
struct evdev *evdev = client->evdev;
struct input_event event;
int retval;
if (count < input_event_size())
return -EINVAL;
/*如果client的环形缓冲区中没有数据并且是非阻塞的，那么返回-EAGAIN，也就是try again*/
if (client->head == client->tail && evdev->exist &&
(file->f_flags & O_NONBLOCK))
return -EAGAIN;
/*如果没有数据，并且是阻塞的，则在等待队列上等待吧*/
retval = wait_event_interruptible(evdev->wait,
client->head != client->tail || !evdev->exist);
if (retval)
return retval;
if (!evdev->exist)
return -ENODEV;
/*如果获得了数据则取出来，调用evdev_fetch_next_event*/
while (retval + input_event_size() <= count &&
evdev_fetch_next_event(client, &event)) {
/*input_event_to_user调用copy_to_user传入用户程序中，这样读取完成*/
if (input_event_to_user(buffer + retval, &event))
return -EFAULT;
retval += input_event_size();
}
return retval;
}
C-sharp代码
static int evdev_fetch_next_event(struct evdev_client *client,
struct input_event *event)
{
int have_event;
spin_lock_irq(&client->buffer_lock);
/*先判断一下是否有数据*/
have_event = client->head != client->tail;
/*如果有就从环形缓冲区的取出来，记得是从head存储，tail取出*/
if (have_event) {
*event = client->buffer[client->tail++];
client->tail &= EVDEV_BUFFER_SIZE - 1;
}
spin_unlock_irq(&client->buffer_lock);
return have_event;
}
C-sharp代码
int input_event_to_user(char __user *buffer,
const struct input_event *event)
{
/*如果设置了标志INPUT_COMPAT_TEST就将事件event包装成结构体compat_event*/
if (INPUT_COMPAT_TEST) {
struct input_event_compat compat_event;
compat_event.time.tv_sec = event->time.tv_sec;
compat_event.time.tv_usec = event->time.tv_usec;
compat_event.type = event->type;
compat_event.code = event->code;
compat_event.value = event->value;
/*将包装成的compat_event拷贝到用户空间*/
if (copy_to_user(buffer, &compat_event,
sizeof(struct input_event_compat)))
return -EFAULT;
} else {
/*否则，将event拷贝到用户空间*/
if (copy_to_user(buffer, event, sizeof(struct input_event)))
return -EFAULT;
}
return 0;
}
这里总结一下：如果两个进程打开同一个文件，每个进程在打开时都会生成一个evdev_client，evdev_client被挂在evdev的client_list，在handle收到一个事件的时候，会把事件copy到挂在client_list上的所有evdev_client的buffer中。这样所有打开同一个设备的进程都会收到这个消息而唤醒。
http://blog.csdn.net/woshixingaaa/archive/2011/05/19/6433337.aspx
input子系统最重要的部分就是向上层report了。这里还是先介绍几个数据结构：
C-sharp代码
struct input_event {
struct timeval time; //事件发生的时间
__u16 type; //事件类型
__u16 code; //子事件
__s32 value; //事件的value
};
C-sharp代码
struct evdev_client {
struct input_event buffer[EVDEV_BUFFER_SIZE]; //可以同时管理EVDEV_BUFFER_SIZE(64)个事件
int head; //存储事件从head开始
int tail; //取出事件从tail开始
spinlock_t buffer_lock; /* protects access to buffer, head and tail */
struct fasync_struct *fasync; //异步通知事件发生
struct evdev *evdev; //指向本evdev_client归属的evdev
struct list_head node; //用于挂载到evdev的链表头client_list上
};
C-sharp代码
static struct input_handler evdev_handler = {
.event = evdev_event,
.connect = evdev_connect,
.disconnect = evdev_disconnect,
.fops = &evdev_fops,
.minor = EVDEV_MINOR_BASE,
.name = "evdev",
.id_table = evdev_ids,
};
这里的次设备号是EVDEV_MINOR_BASE(64)，也就是说evdev_handler所表示的设备文件范围(13,64)~(13,64+32)。
如下一个结构体:evdev_handler匹配所有设备。
C-sharp代码
static const struct input_device_id evdev_ids[] = {
{ .driver_info = 1 }, /* Matches all devices */
{ }, /* Terminating zero entry */
};
这个是evdev_handler是fops，下面的讲解中会用到其中的open,read函数。
C-sharp代码
static const struct file_operations evdev_fops = {
.owner = THIS_MODULE,
.read = evdev_read,
.write = evdev_write,
.poll = evdev_poll,
.open = evdev_open,
.release = evdev_release,
.unlocked_ioctl = evdev_ioctl,
#ifdef CONFIG_COMPAT
.compat_ioctl = evdev_ioctl_compat,
#endif
.fasync = evdev_fasync,
.flush = evdev_flush
};
在驱动程序中我们会调用input_report_abs等函数：
C-sharp代码
static inline void input_report_abs(struct input_dev *dev, unsigned int code, int value)
{
input_event(dev, EV_ABS, code, value);
}
跟踪input_event如下：
C-sharp代码
void input_event(struct input_dev *dev,
unsigned int type, unsigned int code, int value)
{
unsigned long flags;
if (is_event_supported(type, dev->evbit, EV_MAX)) {
spin_lock_irqsave(&dev->event_lock, flags);
/*利用输入值调正随机数产生器*/
add_input_randomness(type, code, value);
input_handle_event(dev, type, code, value);
spin_unlock_irqrestore(&dev->event_lock, flags);
}
}
跟踪input_handle_event如下：
C-sharp代码
static void input_handle_event(struct input_dev *dev,
unsigned int type, unsigned int code, int value)
{
int disposition = INPUT_IGNORE_EVENT;
switch (type) {
。。。。。。。。。。。。。。。。
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);
if (disposition & INPUT_PASS_TO_HANDLERS)
input_pass_event(dev, type, code, value);
}
如果该事件需要input device来完成，就会将disposition设置成INPUT_PASS_TO_DEVICE，如果需要input handler来完成，就会将disposition设置成INPUT_PASS_TO_DEVICE，如果需要两者都参与，则将disposition设置成INPUT_PASS_TO_ALL。
跟踪input_pass_event如下：
C-sharp代码
static void input_pass_event(struct input_dev *dev,
unsigned int type, unsigned int code, int value)
{
struct input_handle *handle;
rcu_read_lock();
/**/
handle = rcu_dereference(dev->grab);
if (handle)
/*如果input_dev的grab指向了一个handle，就用这个handle关联的handler的event，否则遍历整个挂在input_dev的h_list上的handle关联的handler*/
handle->handler->event(handle, type, code, value);
else
list_for_each_entry_rcu(handle, &dev->h_list, d_node)
if (handle->open)
handle->handler->event(handle,
type, code, value);
rcu_read_unlock();
}
比如下边的evdev_handler的evdev_event：
C-sharp代码
static void evdev_event(struct input_handle *handle,
unsigned int type, unsigned int code, int value)
{
struct evdev *evdev = handle->private;
struct evdev_client *client;
struct input_event event;
do_gettimeofday(&event.time);
event.type = type;
event.code = code;
event.value = value;
rcu_read_lock();
client = rcu_dereference(evdev->grab);
if (client)
/*如果evdev->grab指向一个当前使用的client就将event放到这个client的buffer中，否则放到整个client_list上的client的链表中*/
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);
}
C-sharp代码
static void evdev_pass_event(struct evdev_client *client,
struct input_event *event)
{
/*
* Interrupts are disabled, just acquire the lock
*/
spin_lock(&client->buffer_lock);
/*将event装入client的buffer中，buffer是一个环形缓存区*/
client->buffer[client->head++] = *event;
client->head &= EVDEV_BUFFER_SIZE - 1;
spin_unlock(&client->buffer_lock);
kill_fasync(&client->fasync, SIGIO, POLL_IN);
}
这里总结一下事件的传递过程：首先在驱动层中，调用inport_report_abs，然后他调用了input core层的input_event，input_event调用了input_handle_event对事件进行分派，调用input_pass_event，在这里他会把事件传递给具体的handler层，然后在相应handler的event处理函数中，封装一个event，然后把它投入evdev的那个client_list上的client的事件buffer中，等待用户空间来读取。
下边看一下用户程序打开文件时的过程，首先调用了input_open_file:
C-sharp代码
static int input_open_file(struct inode *inode, struct file *file)
{
struct input_handler *handler;
const struct file_operations *old_fops, *new_fops = NULL;
int err;
lock_kernel();
/* No load-on-demand here? */
/*因为32个input_dev公共一个handler所以低5位应该是相同的*/
handler = input_table[iminor(inode) >> 5];
if (!handler || !(new_fops = fops_get(handler->fops))) {
err = -ENODEV;
goto out;
}
/*
* That's _really_ odd. Usually NULL ->open means "nothing special",
* not "no device". Oh, well...
*/
if (!new_fops->open) {
fops_put(new_fops);
err = -ENODEV;
goto out;
}
/*保存以前的fops，使用相应的handler的fops*/
old_fops = file->f_op;
file->f_op = new_fops;
err = new_fops->open(inode, file);
if (err) {
fops_put(file->f_op);
file->f_op = fops_get(old_fops);
}
fops_put(old_fops);
out:
unlock_kernel();
return err;
}
这里还是假设handler是evdev_handler。
C-sharp代码
static int evdev_open(struct inode *inode, struct file *file)
{
struct evdev *evdev;
struct evdev_client *client;
/*因为次设备号是从EVDEV_MINOR_BASE开始的*/
int i = iminor(inode) - EVDEV_MINOR_BASE;
int error;
if (i >= EVDEV_MINORS)
return -ENODEV;
error = mutex_lock_interruptible(&evdev_table_mutex);
if (error)
return error;
/*evdev_table一共可容纳32个成员，找到次设备号对应的那个*/
evdev = evdev_table[i];
if (evdev)
get_device(&evdev->dev);
mutex_unlock(&evdev_table_mutex);
if (!evdev)
return -ENODEV;
/*打开的时候创建一个client*/
client = kzalloc(sizeof(struct evdev_client), GFP_KERNEL);
if (!client) {
error = -ENOMEM;
goto err_put_evdev;
}
spin_lock_init(&client->buffer_lock);
/*下边两句的作用就是将evdev和client绑定到一起*/
client->evdev = evdev;
evdev_attach_client(evdev, client);
error = evdev_open_device(evdev);
if (error)
goto err_free_client;
/*将file->private_data指向刚刚建的client，后边会用到的*/
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;
}
C-sharp代码
static int evdev_open_device(struct evdev *evdev)
{
int retval;
retval = mutex_lock_interruptible(&evdev->mutex);
if (retval)
return retval;
/*如果设备不存在，返回错误*/
if (!evdev->exist)
retval = -ENODEV;
/*如果是被第一次打开，则调用input_open_device*/
else if (!evdev->open++) {
retval = input_open_device(&evdev->handle);
if (retval)
evdev->open--;
}
mutex_unlock(&evdev->mutex);
return retval;
}
C-sharp代码
int input_open_device(struct input_handle *handle)
{
struct input_dev *dev = handle->dev;
int retval;
retval = mutex_lock_interruptible(&dev->mutex);
if (retval)
return retval;
if (dev->going_away) {
retval = -ENODEV;
goto out;
}
handle->open++;
if (!dev->users++ && dev->open)
retval = dev->open(dev);
if (retval) {
dev->users--;
if (!--handle->open) {
/*
* Make sure we are not delivering any more events
* through this handle
*/
synchronize_rcu();
}
}
out:
mutex_unlock(&dev->mutex);
return retval;
}
下面是用户进程读取event的底层实现：
C-sharp代码
static ssize_t evdev_read(struct file *file, char __user *buffer,
size_t count, loff_t *ppos)
{
/*这个就是刚才在open函数中*/
struct evdev_client *client = file->private_data;
struct evdev *evdev = client->evdev;
struct input_event event;
int retval;
if (count < input_event_size())
return -EINVAL;
/*如果client的环形缓冲区中没有数据并且是非阻塞的，那么返回-EAGAIN，也就是try again*/
if (client->head == client->tail && evdev->exist &&
(file->f_flags & O_NONBLOCK))
return -EAGAIN;
/*如果没有数据，并且是阻塞的，则在等待队列上等待吧*/
retval = wait_event_interruptible(evdev->wait,
client->head != client->tail || !evdev->exist);
if (retval)
return retval;
if (!evdev->exist)
return -ENODEV;
/*如果获得了数据则取出来，调用evdev_fetch_next_event*/
while (retval + input_event_size() <= count &&
evdev_fetch_next_event(client, &event)) {
/*input_event_to_user调用copy_to_user传入用户程序中，这样读取完成*/
if (input_event_to_user(buffer + retval, &event))
return -EFAULT;
retval += input_event_size();
}
return retval;
}
C-sharp代码
static int evdev_fetch_next_event(struct evdev_client *client,
struct input_event *event)
{
int have_event;
spin_lock_irq(&client->buffer_lock);
/*先判断一下是否有数据*/
have_event = client->head != client->tail;
/*如果有就从环形缓冲区的取出来，记得是从head存储，tail取出*/
if (have_event) {
*event = client->buffer[client->tail++];
client->tail &= EVDEV_BUFFER_SIZE - 1;
}
spin_unlock_irq(&client->buffer_lock);
return have_event;
}
C-sharp代码
int input_event_to_user(char __user *buffer,
const struct input_event *event)
{
/*如果设置了标志INPUT_COMPAT_TEST就将事件event包装成结构体compat_event*/
if (INPUT_COMPAT_TEST) {
struct input_event_compat compat_event;
compat_event.time.tv_sec = event->time.tv_sec;
compat_event.time.tv_usec = event->time.tv_usec;
compat_event.type = event->type;
compat_event.code = event->code;
compat_event.value = event->value;
/*将包装成的compat_event拷贝到用户空间*/
if (copy_to_user(buffer, &compat_event,
sizeof(struct input_event_compat)))
return -EFAULT;
} else {
/*否则，将event拷贝到用户空间*/
if (copy_to_user(buffer, event, sizeof(struct input_event)))
return -EFAULT;
}
return 0;
}
这里总结一下：如果两个进程打开同一个文件，每个进程在打开时都会生成一个evdev_client，evdev_client被挂在evdev的client_list，在handle收到一个事件的时候，会把事件copy到挂在client_list上的所有evdev_client的buffer中。这样所有打开同一个设备的进程都会收到这个消息而唤醒。
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