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###############################################################################################
早前曾研究了一下输入子系统的原理,给人的感觉是输入子系统很复杂.但其实内核开发者在这方面已经做得很完善了,
输入子系统虽然错综复杂,但是只要我们领会了输入子系统的一些设计思想后,我们要使用它并非难事.
以下以内核自带的gpio_keys驱动为例,介绍输入子系统的使用.
主要的原因是gpio_keys驱动比较简单易懂,另外不是没个人都有触摸屏,但键盘的话相信每一块开发板上都配有吧^_^
按照以前的习惯,先从下到上的研究底层驱动是如何提交输入事件的:
###############################################################################################
drivers/input/keyboard/gpio_keys.c:
static int __devinit
gpio_keys_probe(struct platform_device*pdev)
{
structgpio_keys_platform_data *pdata =pdev->dev.platform_data;
structinput_dev *input;
int i,error;
input =input_allocate_device();
//申请input_dev结构
if(!input)
return-ENOMEM;
platform_set_drvdata(pdev, input);
//把input_dev结构放好(以后方便调用)
input->evbit[0] = BIT(EV_KEY);
//目前event的类型不操作32,所以你会看到对于evbit数组的操作都是对evbit[0]中的位来进行操作.
input->name = pdev->name;
input->phys = "gpio-keys/input0";
input->dev.parent =&pdev->dev;
input->id.bustype = BUS_HOST;
input->id.vendor = 0x0001;
input->id.product = 0x0001;
input->id.version = 0x0100;
for (i = 0;i < pdata->nbuttons; i++) {
structgpio_keys_button *button =&pdata->buttons[i];
int irq =gpio_to_irq(button->gpio);
unsigned inttype = button->type ?: EV_KEY;
set_irq_type(irq, IRQ_TYPE_EDGE_BOTH);
error =request_irq(irq, gpio_keys_isr, IRQF_SAMPLE_RANDOM,
button->desc ? button->desc :"gpio_keys",
pdev);
if (error){
printk(KERN_ERR "gpio-keys: unable to claim irq %d; error%d\n",
irq,error);
gotofail;
}
input_set_capability(input, type,button->code);
}
error =input_register_device(input);
//注册输入设备,并和对应的handler处理函数挂钩
if (error){
printk(KERN_ERR "Unable to register gpio-keys inputdevice\n");
gotofail;
}
return0;
fail:
for (i = i -1; i >= 0; i--)
free_irq(gpio_to_irq(pdata->buttons[i].gpio),pdev);
input_free_device(input);
returnerror;
}
提到input_dev结构,以下谈一下我对于它的理解:
struct
input_dev
{
void*private;
const char*name;
const char*phys;
const char*uniq;
structinput_id id;
unsignedlong evbit[NBITS(EV_MAX)];
unsignedlong keybit[NBITS(KEY_MAX)];
unsignedlong relbit[NBITS(REL_MAX)];
unsignedlong absbit[NBITS(ABS_MAX)];
unsignedlong mscbit[NBITS(MSC_MAX)];
unsignedlong ledbit[NBITS(LED_MAX)];
unsignedlong sndbit[NBITS(SND_MAX)];
unsignedlong ffbit[NBITS(FF_MAX)];
unsignedlong swbit[NBITS(SW_MAX)];
.........................................
};
void
input_set_capability(struct input_dev *dev,unsigned int type, unsigned int code)
{
switch(type) {
caseEV_KEY:
__set_bit(code, dev->keybit);
//比如按键,应该对哪些键值的按键进行处理(对于其它按键不予理睬)
break;
caseEV_REL:
__set_bit(code, dev->relbit);
break;
caseEV_ABS:
__set_bit(code, dev->absbit);
break;
caseEV_MSC:
__set_bit(code, dev->mscbit);
break;
caseEV_SW:
__set_bit(code, dev->swbit);
break;
caseEV_LED:
__set_bit(code, dev->ledbit);
break;
caseEV_SND:
__set_bit(code, dev->sndbit);
break;
caseEV_FF:
__set_bit(code, dev->ffbit);
break;
default:
printk(KERN_ERR
"input_set_capability: unknown type %u (code %u)\n",
type,code);
dump_stack();
return;
}
__set_bit(type, dev->evbit);
//感觉和前面重复了(前面一经配置过一次了)
}
EXPORT_SYMBOL(input_set_capability);
static irqreturn_t
gpio_keys_isr(int irq, void *dev_id)
{
int i;
struct platform_device *pdev = dev_id;
struct gpio_keys_platform_data *pdata =pdev->dev.platform_data;
struct input_dev *input = platform_get_drvdata(pdev);
for (i = 0; i < pdata->nbuttons; i++){
struct gpio_keys_button *button =&pdata->buttons[i];
int gpio = button->gpio;
if (irq == gpio_to_irq(gpio)) {
//判断哪个键被按了?
unsigned int type = button->type ?: EV_KEY;
int state = (gpio_get_value(gpio) ? 1 : 0) ^button->active_low;
//记录按键状态
input_event(input, type, button->code,!!state);
//汇报输入事件
input_sync(input);
//等待输入事件处理完成
}
}
return IRQ_HANDLED;
}
void
input_event(struct input_dev *dev, unsigned inttype, unsigned int code, int value)
{
structinput_handle *handle;
if (type> EV_MAX || !test_bit(type,dev->evbit))
//首先判断该事件类型是否有效且为该设备所接受
return;
add_input_randomness(type, code, value);
switch(type) {
caseEV_SYN:
switch(code) {
caseSYN_CONFIG:
if(dev->event)
dev->event(dev, type, code, value);
break;
caseSYN_REPORT:
if(dev->sync)
return;
dev->sync = 1;
break;
}
break;
caseEV_KEY:
if (code> KEY_MAX || !test_bit(code,dev->keybit) || !!test_bit(code,dev->key) == value)
return;
if (value ==2)
break;
change_bit(code, dev->key);
//改变对应按键的状态
if(test_bit(EV_REP, dev->evbit)&&dev->rep[REP_PERIOD]&&dev->rep[REP_DELAY]&& dev->timer.data&& value) {
dev->repeat_key = code;
mod_timer(&dev->timer, jiffies +msecs_to_jiffies(dev->rep[REP_DELAY]));
}
break;
........................................................
if (type !=EV_SYN)
dev->sync = 0;
if(dev->grab)
dev->grab->handler->event(dev->grab,type, code, value);
else
list_for_each_entry(handle,&dev->h_list, d_node)
if(handle->open)
handle->handler->event(handle, type,code, value);
}
EXPORT_SYMBOL(input_event);
#########################################################################
好了,下面再来研究一下event层对于input层报告的这个键盘输入事件是如何来处理的.
#########################################################################
drivers/input/evdev.c:
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,
};
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;
if (evdev->grab) {
client = evdev->grab;
do_gettimeofday(&client->buffer[client->head].time);
client->buffer[client->head].type =type;
client->buffer[client->head].code =code;
client->buffer[client->head].value =value;
client->head = (client->head + 1)& (EVDEV_BUFFER_SIZE - 1);
kill_fasync(&client->fasync, SIGIO,POLL_IN);
} else
list_for_each_entry(client,&evdev->client_list, node) {
do_gettimeofday(&client->buffer[client->head].time);
client->buffer[client->head].type =type;
client->buffer[client->head].code =code;
client->buffer[client->head].value =value;
client->head = (client->head + 1)& (EVDEV_BUFFER_SIZE - 1);
kill_fasync(&client->fasync, SIGIO,POLL_IN);//通知调用input_sync的进程:输入事件经已处理完毕(通知底层).
}
wake_up_interruptible(&evdev->wait);//唤醒睡眠在evdev->wait等待队列等待输入信息的进程(通知上层).
}
###################################################################################
好了,至此一个按键的输入事件处理完毕,现在再来从上到上的来看看用户是如何获取这个输入事件的.
###################################################################################
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
};
static int evdev_open(struct inode *inode, struct file*file)
{
struct evdev_client *client;
struct evdev *evdev;
int i = iminor(inode) - EVDEV_MINOR_BASE;
int error;
if (i >= EVDEV_MINORS)
return -ENODEV;
evdev = evdev_table[i];
if (!evdev || !evdev->exist)
return -ENODEV;
client = kzalloc(sizeof(struct evdev_client), GFP_KERNEL);
if (!client)
return -ENOMEM;
client->evdev = evdev;
list_add_tail(&client->node,&evdev->client_list);
if (!evdev->open++&& evdev->exist){
error =input_open_device(&evdev->handle);
if (error) {
list_del(&client->node);
kfree(client);
return error;
}
}
file->private_data = client;//存放好evdev_client结构方便以后使用
return 0;
}
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;
int retval;
if (count < evdev_event_size())//对于每次读取的数据大小是有一定的要求.
return -EINVAL;
if (client->head == client->tail&& evdev->exist&& (file->f_flags& O_NONBLOCK))//缓存中没有数据可读且设备是存在的,
如果设置为NONBLOCK方式来读,立即返回.
return -EAGAIN;
retval = wait_event_interruptible(evdev->wait,
client->head != client->tail ||!evdev->exist);//否则等待缓存有数据可读或设备不存在(被移去)
if (retval)
return retval;
if (!evdev->exist)
return -ENODEV;
while (client->head != client->tail&& retval + evdev_event_size()<= count) {//下面开始读取数据
struct input_event *event = (struct input_event *)client->buffer +client->tail;//获取缓存中的读指针
if (evdev_event_to_user(buffer + retval, event))//返回数据给用户
return -EFAULT;
client->tail = (client->tail + 1)& (EVDEV_BUFFER_SIZE - 1);//更新读指针
retval += evdev_event_size();
}
return retval;
}
呵呵,看到了吧,应用程序就是这样获取输入事件的^_^
##########################################################################################################
本来对于gpio_keys这样的驱动程序,只要当发生按键事件的时候向上层应用程序汇报键值即可.
不过,对于一些带输出设备(例如led灯)的输入设备来说(例如键盘),上层应用程序同样可以利用event层来读取或改变其状态.
请看以下代码:
##########################################################################################################
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 = 0;
if (!evdev->exist)
return -ENODEV;
while (retval < count) {
if (evdev_event_from_user(buffer + retval,&event))//从用户处获取事件结构
return -EFAULT;
input_inject_event(&evdev->handle,event.type, event.code, event.value);//往底层发送事件
retval += evdev_event_size();
}
return retval;
}
void input_inject_event(struct input_handle *handle,unsigned int type, unsigned int code, int value)
{
if (!handle->dev->grab ||handle->dev->grab == handle)
input_event(handle->dev, type, code, value);
}
EXPORT_SYMBOL(input_inject_event);
void input_event(struct input_dev *dev, unsigned inttype, unsigned int code, int value)
{
structinput_handle *handle;
if (type> EV_MAX || !test_bit(type,dev->evbit))//首先判断该事件类型是否有效且为该设备所接受
return;
add_input_randomness(type, code, value);
switch(type) {
caseEV_SYN:
switch(code) {
caseSYN_CONFIG:
if(dev->event)
dev->event(dev, type, code, value);
break;
caseSYN_REPORT:
if(dev->sync)
return;
dev->sync = 1;
break;
}
break;
.............................................................
caseEV_LED:
if (code> LED_MAX || !test_bit(code,dev->ledbit) || !!test_bit(code,dev->led) == value)
return;
change_bit(code, dev->led);
if(dev->event)
dev->event(dev, type, code, value);
break;
if (type !=EV_SYN)
dev->sync = 0;
if(dev->grab)
dev->grab->handler->event(dev->grab,type, code, value);
else
list_for_each_entry(handle,&dev->h_list, d_node)
if(handle->open)
handle->handler->event(handle, type,code, value);
}
EXPORT_SYMBOL(input_event);
注:
鉴于简单的gpio_keys驱动中没有注册自己的event接口,当然也没有对于LED灯的处理,而event层只是简单的向上层汇报输入事件(event层也不可能帮你处理你的led设备,对吧),所以这个通过输入子系统控制LED的部分暂时不去研究.
(输出设备LED灯不属于这个输入设备gpio_key的一部分.当然,如果你想通过这个gpio_keys设备来控制led灯的话,可以修改这个gpio_keys驱动,详细可参考driver/input/keyboard目录下的驱动)
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