分类： LINUX
2010-08-27 18:35:22
linux输入子系统 2008-11-03 18:14:49 阅读135 评论0 字号：大中小
［转］http://blog.chinaunix.net/u1/38994/showart_1130025.html
浅析linux下键盘设备工作和注册流程
【浅析linux下鼠标驱动的实现】
input_init()=>
=>
class_register(&input_class);注册input类
input_proc_init();创建proc下的目录和文件
register_chrdev(INPUT_MAJOR, "input", &input_fops);注册驱动程序到cdev_map上,以待驱动设备.
drivers\input\keyboard\pxa3xx_keypad.c为我们的keyboard设备,
pxa3xx_keypad_probe=>
request_irq(IRQ_ENHROT, &enhanced_rotary_interrupt,
IRQF_DISABLED, "Enhanced Rotary", (void *)keypad);注册快捷键中断
request_irq(IRQ_KEYPAD, pxa3xx_keypad_interrupt, IRQF_DISABLED,pdev->name, keypad);注册中断
static irqreturn_t pxa3xx_keypad_interrupt(int irq, void *dev_id)
{
struct pxa3xx_keypad *keypad = dev_id;
uint32_t kpc = keypad_readl(KPC);
if (kpc & KPC_MI)
pxa3xx_keypad_scan_matrix(keypad);
if (kpc & KPC_DI)
pxa3xx_keypad_scan_direct(keypad);
return IRQ_HANDLED;
}
在irq中如果读到了key,那么会直接调用
input_report_key(keypad->input_dev,lookup_matrix_keycode(keypad, row, col),
new_state[col] & (1 << row));
static inline unsigned int lookup_matrix_keycode(
struct pxa3xx_keypad *keypad, int row, int col)
{
return keypad->matrix_keycodes[(row << 3) + col];
}
input_report_key(struct input_dev *dev, unsigned int code, int value)
dev为input_dev设备,我们的4*4键盘
code为标准PC键盘码值
value为按键动作,为1表示键盘按下,为0表示按键抬起
static inline void input_report_key(struct input_dev *dev, unsigned int code, int value)
{
input_event(dev, EV_KEY, code, !!value);
}
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);
add_input_randomness(type, code, value);//因为按键的存在随机性,所以按键是给系统提供墒随机数的好来源.
input_handle_event(dev, type, code, value);
spin_unlock_irqrestore(&dev->event_lock, flags);
}
}
static void input_handle_event(struct input_dev *dev,
unsigned int type, unsigned int code, int value)
{
...
case EV_KEY:
if (is_event_supported(code, dev->keybit, KEY_MAX) &&
!!test_bit(code, dev->key) != value) {//这次来的是否为新的键值
if (value != 2) {
__change_bit(code, dev->key);//通过异或^操作,反转code对应的bitmap,如果value等于2,那么将忽略该按键
if (value)
input_start_autorepeat(dev, code);//键盘按下,那么开启定时检测,这样可以出现连续输入的效果
}
disposition = INPUT_PASS_TO_HANDLERS;
}
break;
...
}
static void input_start_autorepeat(struct input_dev *dev, int code)
{
if (test_bit(EV_REP, dev->evbit) &&
dev->rep[REP_PERIOD] && dev->rep[REP_DELAY] &&
dev->timer.data) {
dev->repeat_key = code;
mod_timer(&dev->timer,//重新启动定时器input_repeat_key,时间间隔msecs_to_jiffies(dev->rep[REP_DELAY])
jiffies + msecs_to_jiffies(dev->rep[REP_DELAY]));
}
}
static void input_repeat_key(unsigned long data)
{
struct input_dev *dev = (void *) data;
unsigned long flags;
spin_lock_irqsave(&dev->event_lock, flags);
if (test_bit(dev->repeat_key, dev->key) &&
is_event_supported(dev->repeat_key, dev->keybit, KEY_MAX)) {
input_pass_event(dev, EV_KEY, dev->repeat_key, 2);//交给处理按键函数
if (dev->sync) {
/*
* Only send SYN_REPORT if we are not in a middle
* of driver parsing a new hardware packet.
* Otherwise assume that the driver will send
* SYN_REPORT once it's done.
*/
input_pass_event(dev, EV_SYN, SYN_REPORT, 1);
}
if (dev->rep[REP_PERIOD])
mod_timer(&dev->timer, jiffies +
msecs_to_jiffies(dev->rep[REP_PERIOD]));
}
spin_unlock_irqrestore(&dev->event_lock, flags);
}
input_pass_event=>
handle->handler->event(handle, type, code, value);
就是kbd_handler的kbd_event=>kbd_keycode=>
atomic_notifier_call_chain(&keyboard_notifier_list, KBD_UNICODE, ¶m)
通知挂在keyboard链上所有等待键盘输入的应用程序,
通过register_keyboard_notifier()函数可以注册到键盘链上【gliethttp.Leith】,
input_dev = input_allocate_device();申请一个input设备空间
input_dev->open = pxa3xx_keypad_open;给这个空间填充方法
input_dev->close = pxa3xx_keypad_close;
input_dev->private = keypad;
set_bit(EV_KEY, input_dev->evbit);//键按下
set_bit(EV_REL, input_dev->evbit);//键释放
pxa3xx_keypad_build_keycode(keypad);//设备键盘映射码
该函数将根据pxa3xx_device_keypad设备下的matrix_key_map进行键控设置,
pxa_set_keypad_info(&jades_keypad_info)=>将jades_keypad_info登记为pdata;
#define MAX_MATRIX_KEY_NUM (8 * 8)
matrix_keycodes[MAX_MATRIX_KEY_NUM];表示为8*8键盘
keypad->matrix_keycodes[(row << 3) + col] = code;表示第row行的第col列处按键,代表code编码值,这个为我们内部使用.
set_bit(code, input_dev->keybit);//设置code为我们的键盘对操作系统可用的键盘值
if(pdata->direct_key_num) {
for (i = 0; i < pdata->direct_key_num; i++) {
set_bit(pdata->direct_key_map[i], input_dev->keybit);//快捷键单元
}
}
set_bit(KEY_POWER, input_dev->keybit);//登记电源按键为系统可见按键
input_register_device(input_dev);=>//注册设该备devices_subsys总线上
int input_register_device(struct input_dev *dev)
{
static atomic_t input_no = ATOMIC_INIT(0);
struct input_handler *handler;
const char *path;
int error;
__set_bit(EV_SYN, dev->evbit);
/*
* If delay and period are pre-set by the driver, then autorepeating
* is handled by the driver itself and we don't do it in input.c.
*/
init_timer(&dev->timer);
if (!dev->rep[REP_DELAY] && !dev->rep[REP_PERIOD]) {
dev->timer.data = (long) dev;
dev->timer.function = input_repeat_key;//消抖处理函数,采用延时消抖
dev->rep[REP_DELAY] = 500;//250;
dev->rep[REP_PERIOD] = 66;//33;
}
if (!dev->getkeycode)
dev->getkeycode = input_default_getkeycode;
if (!dev->setkeycode)
dev->setkeycode = input_default_setkeycode;
//在/sys/class/input下创建以input0,input1为目录名的input类型设备
snprintf(dev->dev.bus_id, sizeof(dev->dev.bus_id),
"input%ld", (unsigned long) atomic_inc_return(&input_no) - 1);
if (dev->cdev.dev)
dev->dev.parent = dev->cdev.dev;
error = device_add(&dev->dev);//将设备登记到设备总线上,之后将以目录和文件的形式呈现
if (error)
return error;
path = kobject_get_path(&dev->dev.kobj, GFP_KERNEL);
printk(KERN_INFO "input: %s as %s\n",
dev->name ? dev->name : "Unspecified device", path ? path : "N/A");
kfree(path);
error = mutex_lock_interruptible(&input_mutex);
if (error) {
device_del(&dev->dev);
return error;
}
list_add_tail(&dev->node, &input_dev_list);
//将设备放到input的链表上,该链表上存放着所有input类型的dev设备对象【gliethttp.Leith】
list_for_each_entry(handler, &input_handler_list, node)
input_attach_handler(dev, handler);
//从input_handler_list驱动链表上尝试匹配,是否有驱动该dev设备的driver驱动,如果有,那么将匹配的驱动绑定给dev设备,来驱动这个dev.
input_wakeup_procfs_readers();
mutex_unlock(&input_mutex);
return 0;
}
drivers\char\keyboard.c
kbd_init()=>
input_register_handler(&kbd_handler); 注册键盘驱动到input_handler_list链表上
static int input_attach_handler(struct input_dev *dev, struct input_handler *handler)
{
const struct input_device_id *id;
int error;
//看看这个咚咚,是不是在黑名单里,如果在,那么就byebye了【gliethttp.Leith】
if (handler->blacklist && input_match_device(handler->blacklist, dev))
return -ENODEV;
id = input_match_device(handler->id_table, dev);
if (!id)
return -ENODEV;
error = handler->connect(handler, dev, id);//ok,找到驱动该dev的driver,那么尝试连接
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;
}
kbd_connect=>input_register_handle=>input_open_device=>pxa3xx_keypad_open配置键盘io口
以下内容转自：http://ericxiao.cublog.cn/
九:evdev的初始化
Evdev的模块初始化函数为evdev_init().代码如下:
static int __init evdev_init(void)
{
return input_register_handler(&evdev_handler);
}
它调用了input_register_handler注册了一个handler.
注意到,在这里evdev_handler中定义的minor为EVDEV_MINOR_BASE(64).也就是说evdev_handler所表示的设备文件范围为(13,64)à(13,64+32).
从之前的分析我们知道.匹配成功的关键在于handler中的blacklist和id_talbe. Evdev_handler的id_table定义如下:
static const struct input_device_id evdev_ids[] = {
{ .driver_info = 1 }, /* Matches all devices */
{ }, /* Terminating zero entry */
};
它没有定义flags.也没有定义匹配属性值.这个handler是匹配所有input device的.从前面的分析我们知道.匹配成功之后会调用handler->connect函数.
在Evdev_handler中,该成员函数如下所示:
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++)
if (!evdev_table[minor])
break;
if (minor == EVDEV_MINORS) {
printk(KERN_ERR "evdev: no more free evdev devices\n");
return -ENFILE;
}
EVDEV_MINORS定义为32.表示evdev_handler所表示的32个设备文件.evdev_talbe是一个struct evdev类型的数组.struct evdev是模块使用的封装结构.在接下来的代码中我们可以看到这个结构的使用.
这一段代码的在evdev_talbe找到为空的那一项.minor就是数组中第一项为空的序号.
evdev = kzalloc(sizeof(struct evdev), GFP_KERNEL);
if (!evdev)
return -ENOMEM;
INIT_LIST_HEAD(&evdev->client_list);
spin_lock_init(&evdev->client_lock);
mutex_init(&evdev->mutex);
init_waitqueue_head(&evdev->wait);
snprintf(evdev->name, sizeof(evdev->name), "event%d", minor);
evdev->exist = 1;
evdev->minor = minor;
evdev->handle.dev = input_get_device(dev);
evdev->handle.name = evdev->name;
evdev->handle.handler = handler;
evdev->handle.private = evdev;
接
下来,分配了一个evdev结构,并对这个结构进行初始化.在这里我们可以看到,这个结构封装了一个handle结构,这结构与我们之前所讨论的
handler是不相同的.注意有一个字母的差别哦.我们可以把handle看成是handler和input
device的信息集合体.在这个结构里集合了匹配成功的handler和input device
strlcpy(evdev->dev.bus_id, evdev->name, sizeof(evdev->dev.bus_id));
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);
在这段代码里主要完成evdev封装的device的初始化.注意在这里,使它所属的类指向input_class.这样在/sysfs中创建的设备目录就会在/sys/class/input/下面显示.
error = input_register_handle(&evdev->handle);
if (error)
goto err_free_evdev;
error = evdev_install_chrdev(evdev);
if (error)
goto err_unregister_handle;
error = device_add(&evdev->dev);
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;
}
注册handle,如果是成功的,那么调用evdev_install_chrdev将evdev_table的minor项指向evdev. 然后将evdev->device注册到sysfs.如果失败,将进行相关的错误处理.
万事俱备了,但是要接收事件,还得要等”东风”.这个”东风”就是要打开相应的handle.这个打开过程是在文件的open()中完成的.
十:evdev设备结点的open()操作
我们知道.对主设备号为INPUT_MAJOR的设备节点进行操作,会将操作集转换成handler的操作集.在evdev中,这个操作集就是evdev_fops.对应的open函数如下示:
static int evdev_open(struct inode *inode, struct file *file)
{
struct evdev *evdev;
struct evdev_client *client;
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 = evdev_table[i];
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;
evdev_attach_client(evdev, client);
error = evdev_open_device(evdev);
if (error)
goto err_free_client;
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;
}
iminor(inode) - EVDEV_MINOR_BASE就得到了在evdev_table[ ]中的序号.然后将数组中对应的evdev取出.递增devdev中device的引用计数.
分配并初始化一个client.并将它和evdev关联起来: client->evdev指向它所表示的evdev. 将client挂到evdev->client_list上. 将client赋为file的私有区.
对应handle的打开是在此evdev_open_device()中完成的.代码如下:
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++) {
retval = input_open_device(&evdev->handle);
if (retval)
evdev->open--;
}
mutex_unlock(&evdev->mutex);
return retval;
}
如果evdev是第一次打开,就会调用input_open_device()打开evdev对应的handle.跟踪一下这个函数:
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;
}
在这个函数中,我们看到.递增handle的打开计数.如果是第一次打开.则调用input device的open()函数.
十一:evdev的事件处理
经过上面的分析.每当input device上报一个事件时,会将其交给和它匹配的handler的event函数处理.在evdev中.这个event函数对应的代码为:
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)
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);
}
首先构造一个struct input_event结构.并设备它的type.code,value为处理事件的相关属性.如果该设备被强制设置了handle.则调用如之对应的client.
我们在open的时候分析到.会初始化clinet并将其链入到evdev->client_list. 这样,就可以通过evdev->client_list找到这个client了.
对于找到的第一个client都会调用evdev_pass_event( ).代码如下:
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);
client->buffer[client->head++] = *event;
client->head &= EVDEV_BUFFER_SIZE - 1;
spin_unlock(&client->buffer_lock);
kill_fasync(&client->fasync, SIGIO, POLL_IN);
}
这里的操作很简单.就是将event保存到client->buffer中.而client->head就是当前的数据位置.注意这里是一个环形缓存区.写数据是从client->head写.而读数据则是从client->tail中读.
十二:设备节点的read处理
对于evdev设备节点的read操作都会由evdev_read()完成.它的代码如下:
static ssize_t evdev_read(struct file *file, char __user *buffer,
size_t count, loff_t *ppos)
{
struct evdev_client *client = file->private_data;
struct evdev *evdev = client->evdev;
struct input_event event;
int retval;
if (count < evdev_event_size())
return -EINVAL;
if (client->head == client->tail && evdev->exist &&
(file->f_flags & O_NONBLOCK))
return -EAGAIN;
retval = wait_event_interruptible(evdev->wait,
client->head != client->tail || !evdev->exist);
if (retval)
return retval;
if (!evdev->exist)
return -ENODEV;
while (retval + evdev_event_size() <= count &&
evdev_fetch_next_event(client, &event)) {
if (evdev_event_to_user(buffer + retval, &event))
return -EFAULT;
retval += evdev_event_size();
}
return retval;
}
首先,它判断缓存区大小是否足够.在读取数据的情况下,可能当前缓存区内没有数据可读.在这里先睡眠等待缓存区中有数据.如果在睡眠的时候,.条件满足.是不会进行睡眠状态而直接返回的.
然后根据read()提够的缓存区大小.将client中的数据写入到用户空间的缓存区中.
十三:设备节点的写操作
同样.对设备节点的写操作是由evdev_write()完成的.代码如下:
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;
struct evdev *evdev = client->evdev;
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 (evdev_event_from_user(buffer + retval, &event)) {
retval = -EFAULT;
goto out;
}
input_inject_event(&evdev->handle,
event.type, event.code, event.value);
retval += evdev_event_size();
}
out:
mutex_unlock(&evdev->mutex);
return retval;
}
首先取得操作设备文件所对应的evdev.
实际上,这里写入设备文件的是一个event结构的数组.我们在之前分析过,这个结构里包含了事件的type.code和event.
将写入设备的event数组取出.然后对每一项调用event_inject_event().
这个函数的操作和input_event()差不多.就是将第一个参数handle转换为输入设备结构.然后这个设备再产生一个事件.
代码如下:
void input_inject_event(struct input_handle *handle,
unsigned int type, unsigned int code, int value)
{
struct input_dev *dev = handle->dev;
struct input_handle *grab;
unsigned long flags;
if (is_event_supported(type, dev->evbit, EV_MAX)) {
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);
}
}
我们在这里也可以跟input_event()对比一下,这里设备可以产生任意事件,而不需要和设备所支持的事件类型相匹配.
由此可见.对于写操作而言.就是让与设备文件相关的输入设备产生一个特定的事件.
将上述设备文件的操作过程以图的方式表示如下：
十四:小结
在
这一节点,分析了整个input子系统的架构,各个环节的流程.最后还以evdev为例.将各个流程贯穿在一起.以加深对input子系统的理解.由此也
可以看出.linux设备驱动采用了分层的模式.从最下层的设备模型到设备,驱动,总线再到input子系统最后到input
device.这样的分层结构使得最上层的驱动不必关心下层是怎么实现的.而下层驱动又为多种型号同样功能的驱动提供了一个统一的接口.
