字符设备驱动之按键定时器消抖实现方法

字符设备驱动之按键定时器消抖实现方法。

#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 


static struct class *sixthdrv_class;
static struct class_device	*sixthdrv_class_dev;

volatile unsigned long *gpfcon;
volatile unsigned long *gpfdat;

volatile unsigned long *gpgcon;
volatile unsigned long *gpgdat;

static struct timer_list buttons_timer;


static DECLARE_WAIT_QUEUE_HEAD(button_waitq);

/* 中断事件标志, 中断服务程序将它置1，sixth_drv_read将它清0 */
static volatile int ev_press = 0;

static struct fasync_struct *button_async;


struct pin_desc{
	unsigned int pin;
	unsigned int key_val;
};


/* 键值: 按下时, 0x01, 0x02, 0x03, 0x04 */
/* 键值: 松开时, 0x81, 0x82, 0x83, 0x84 */
static unsigned char key_val;

struct pin_desc pins_desc[4] = {
	{S3C2410_GPF0, 0x01},
	{S3C2410_GPF2, 0x02},
	{S3C2410_GPG3, 0x03},
	{S3C2410_GPG11, 0x04},
};

static struct pin_desc *irq_pd;

//static atomic_t canopen = ATOMIC_INIT(1);     //定义原子变量并初始化为1

static DECLARE_MUTEX(button_lock);     //定义互斥锁

/*
  * 确定按键值
  */
static irqreturn_t buttons_irq(int irq, void *dev_id)
{
	/* 10ms后启动定时器 */
	irq_pd = (struct pin_desc *)dev_id;
	mod_timer(&buttons_timer, jiffies+HZ/100);
	return IRQ_RETVAL(IRQ_HANDLED);
}

static int sixth_drv_open(struct inode *inode, struct file *file)
{
#if 0	
	if (!atomic_dec_and_test(&canopen))
	{
		atomic_inc(&canopen);
		return -EBUSY;
	}
#endif		

	if (file->f_flags & O_NONBLOCK)
	{
		if (down_trylock(&button_lock))
			return -EBUSY;
	}
	else
	{
		/* 获取信号量 */
		down(&button_lock);
	}

	/* 配置GPF0,2为输入引脚 */
	/* 配置GPG3,11为输入引脚 */
	request_irq(IRQ_EINT0,  buttons_irq, IRQT_BOTHEDGE, "S2", &pins_desc[0]);
	request_irq(IRQ_EINT2,  buttons_irq, IRQT_BOTHEDGE, "S3", &pins_desc[1]);
	request_irq(IRQ_EINT11, buttons_irq, IRQT_BOTHEDGE, "S4", &pins_desc[2]);
	request_irq(IRQ_EINT19, buttons_irq, IRQT_BOTHEDGE, "S5", &pins_desc[3]);	

	return 0;
}

ssize_t sixth_drv_read(struct file *file, char __user *buf, size_t size, loff_t *ppos)
{
	if (size != 1)
		return -EINVAL;

	if (file->f_flags & O_NONBLOCK)
	{
		if (!ev_press)
			return -EAGAIN;
	}
	else
	{
		/* 如果没有按键动作, 休眠 */
		wait_event_interruptible(button_waitq, ev_press);
	}

	/* 如果有按键动作, 返回键值 */
	copy_to_user(buf, &key_val, 1);
	ev_press = 0;
	
	return 1;
}


int sixth_drv_close(struct inode *inode, struct file *file)
{
	//atomic_inc(&canopen);
	free_irq(IRQ_EINT0, &pins_desc[0]);
	free_irq(IRQ_EINT2, &pins_desc[1]);
	free_irq(IRQ_EINT11, &pins_desc[2]);
	free_irq(IRQ_EINT19, &pins_desc[3]);
	up(&button_lock);
	return 0;
}

static unsigned sixth_drv_poll(struct file *file, poll_table *wait)
{
	unsigned int mask = 0;
	poll_wait(file, &button_waitq, wait); // 不会立即休眠

	if (ev_press)
		mask |= POLLIN | POLLRDNORM;

	return mask;
}

static int sixth_drv_fasync (int fd, struct file *filp, int on)
{
	printk("driver: sixth_drv_fasync\n");
	return fasync_helper (fd, filp, on, &button_async);
}


static struct file_operations sencod_drv_fops = {
    .owner   =  THIS_MODULE,    /* 这是一个宏，推向编译模块时自动创建的__this_module变量 */
    .open    =  sixth_drv_open,     
	.read	 =	sixth_drv_read,	   
	.release =  sixth_drv_close,
	.poll    =  sixth_drv_poll,
	.fasync	 =  sixth_drv_fasync,
};


int major;

static void buttons_timer_function(unsigned long data)
{
	struct pin_desc * pindesc = irq_pd;
	unsigned int pinval;

	if (!pindesc)
		return;
	
	pinval = s3c2410_gpio_getpin(pindesc->pin);

	if (pinval)
	{
		/* 松开 */
		key_val = 0x80 | pindesc->key_val;
	}
	else
	{
		/* 按下 */
		key_val = pindesc->key_val;
	}

    ev_press = 1;                  /* 表示中断发生了 */
    wake_up_interruptible(&button_waitq);   /* 唤醒休眠的进程 */
	
	kill_fasync (&button_async, SIGIO, POLL_IN);
}


static int sixth_drv_init(void)
{
	init_timer(&buttons_timer);
	buttons_timer.function = buttons_timer_function;
	//buttons_timer.expires  = 0;
	add_timer(&buttons_timer); 

	major = register_chrdev(0, "sixth_drv", &sencod_drv_fops);

	sixthdrv_class = class_create(THIS_MODULE, "sixth_drv");

	/* 为了让mdev根据这些信息来创建设备节点 */
	sixthdrv_class_dev = class_device_create(sixthdrv_class, NULL, MKDEV(major, 0), NULL, "buttons"); /* /dev/buttons */

	gpfcon = (volatile unsigned long *)ioremap(0x56000050, 16);
	gpfdat = gpfcon + 1;

	gpgcon = (volatile unsigned long *)ioremap(0x56000060, 16);
	gpgdat = gpgcon + 1;

	return 0;
}

static void sixth_drv_exit(void)
{
	unregister_chrdev(major, "sixth_drv");
	class_device_unregister(sixthdrv_class_dev);
	class_destroy(sixthdrv_class);
	iounmap(gpfcon);
	iounmap(gpgcon);
	return 0;
}


module_init(sixth_drv_init);

module_exit(sixth_drv_exit);

MODULE_LICENSE("GPL");

代码出自“韦东山视频”。

1、初始化定时器

static struct timer_list buttons_timer;

init_timer(&buttons_timer);

buttons_timer.function = buttons_timer_function;

//buttons_timer.expires? = 0;

add_timer(&buttons_timer);? //void add_timer(struct timer_list * timer);

2、发生按键中断时，改动定时器的expire

mod_timer(&buttons_timer, jiffies+HZ/100);? //int mod_timer(struct timer_list *timer, unsigned long expires);

3、在定时器响应函数中唤醒休眠进程、发出异步通知

wake_up_interruptible(&button_waitq);

kill_fasync (&button_async, SIGIO, POLL_IN);

4、如果按键按下时间超过10ms，则触发定时器中断，发出“按下”通知，松开按键10ms后再发出“松开”通知；

如果按键按下不到10ms就松开，则重新设置expire，不会发出“按下”通知，只会在10ms后发出“松开”通知。