11.按键驱动之定时器防抖(详解)

1)data     //传递到*function超时处理函数的参数，主要在多个定时器同时使用时，区别是哪个timer超时。

2)expires  //定时器到期的时间,当expires小于等于jiffies时,这个定时器便到期并调用定时器超时处理函数,然后就不会再调用了,             比如要使用10ms后到期,赋值(jiffies+HZ/100)即可

3)void (*function)(unsigned long) //定时器超时处理函数。

init_timer(struct timer_list*)    //定时器初始化结构体函数,

add_timer(struct timer_list*)     //往系统添加定时器,告诉内核有个定时器结构体

mod_timer(struct timer_list *, unsigned long jiffier_timerout) //修改定时器的超时时间为jiffies_timerout,                                                                 当expires小于等于jiffies时,便调用定时器超时处理函数。

timer_pending(struct timer_list *)    //定时器状态查询，如果在系统的定时器列表中则返回1，否则返回0；

del_timer(struct timer_list*)         //删除定时器,在本驱动程序出口函数sixth_drv_exit()里添加

static struct timer_list buttons_timer;   //定义定时器结构体

init_timer(&buttons_timer);     //初始化结构体

/*本中断都是更新同一个定时器,所以成员.data无需初始,默认为0
不需要定时器到期时间,所以成员.expires无需初始化,默认为0,由于小于等于jiffies,会进入一次定时器超时函数*/
buttons_timer. function= buttons_timer_ function;

add_timer(&buttons_timer);       //告诉内核，有一个定时器

del_timer(&buttons_timer);        //删除定时器

struct pin_desc *irq_dev_id ;    //定义全局变量获取dev_id

static irqreturn_t  buttons_irq (int irq, void *dev_id)       //中断服务函数
{
     irq_dev_id =(struct pin_desc *)dev_id;     //获取引脚描述结构体
          /*每产生一次中断,则更新定时器10ms超时 */   
     mod_timer(&buttons_timer, jiffies+HZ/100);

     return IRQ_RETVAL(IRQ_HANDLED);                
}

static  void buttons_timer_function(unsigned long data)   //定时器超时函数
{      
       unsigned int  pin_val=0;   
       if(!irq_dev_id)   //初始化时,由于定时器.expires成员=0,会进入一次,若irq_dev_id为0则退出
       {printk("expires: timer out\n");
         return ; }                                              

       pin_val=s3c2410_gpio_getpin(irq_dev_id->pin);   //获取按键值

        if(pin_val)
        {
                  /*按下 (下降沿),清除0x80*/      
                   key_val=irq_dev_id->pin_status&0xef;
         }
         else
         {
                   /*没有按下(上升沿),加上0x80*/
                   key_val=irq_dev_id->pin_status|0x80;
         }
       
            even_press=1;                                        //退出等待队列
            wake_up_interruptible(&button_wait);                //唤醒 中断
            kill_fasync(&button_async, SIGIO, POLL_IN);        //发送SIGIO信号给应用层
}

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/init.h>
#include <linux/delay.h>
#include <linux/irq.h>  
#include <asm/irq.h>
#include <asm/arch/regs-gpio.h>
#include <asm/hardware.h>
#include <asm/uaccess.h>
#include <asm/io.h>                      
#include <linux/poll.h>                  

static struct timer_list buttons_timer;   //定义定时器结构体
struct pin_desc *irq_dev_id ;    //定义全局变量获取dev_id
static struct class *sixthdrv_class;                 
static struct class_device   *sixthdrv_class_devs; 

/*定义互斥锁button_lock,被用来后面的down()和up()使用 */
static DECLARE_MUTEX(button_lock);  

/*    声明等待队列类型中断 button_wait      */
static DECLARE_WAIT_QUEUE_HEAD(button_wait);

/*    异步信号结构体变量    */
static struct fasync_struct * button_async;
 

/*
  * 定义中断事件标志
  * 0:进入等待队列        1:退出等待队列
  */
static int even_press=0;                          

 
/*
  * 定义全局变量key_val,保存key状态
  */
static int key_val=0;                          

 
/*
  *引脚描述结构体
  */
 struct pin_desc{
   unsigned int  pin;
   unsigned int  pin_status;
};

 
/*
  *key初始状态(没有按下): 0x81,0x82,0x83,0x84
  *key状态(按下):        0x01,0x02,0x03,0x04
  */
         struct pin_desc  pins_desc[4]={
                   {S3C2410_GPF0,0x01 },
                   {S3C2410_GPF2, 0x02 },
                   {S3C2410_GPG3, 0x03 },
                   {S3C2410_GPG11,0x04},
} ;


int  sixth_drv_class(struct inode *inode, struct file  *file)  //卸载中断
{
  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]);

           /*释放信号量*/
           up(&button_lock);                                   

          return 0;
}



/*
  *   确定是上升沿还是下降沿
  */
static irqreturn_t  buttons_irq (int irq, void *dev_id)       //中断服务函数
{
        irq_dev_id =(struct pin_desc *)dev_id;     //获取引脚描述结构体
 
         /*每产生一次中断,则更新定时器10ms超时 */   
         mod_timer(&buttons_timer, jiffies+HZ/100);
       
         return IRQ_RETVAL(IRQ_HANDLED);                          
}

 


static int sixth_drv_open(struct inode *inode, struct file  *file)
{
   if(  file->f_flags & O_NONBLOCK )   //非阻塞操作,获取不到则退出
  {
   if(down_trylock(&button_lock) )
                   return -1;
  }

  else   //阻塞操作，获取不到则进入休眠
  {
     down(&button_lock); 
  }


   request_irq(IRQ_EINT0,buttons_irq,IRQT_BOTHEDGE,"S1",&pins_desc[0]);
   request_irq(IRQ_EINT2, buttons_irq,IRQT_BOTHEDGE, "S2", &pins_desc[1]);
   request_irq(IRQ_EINT11, buttons_irq,IRQT_BOTHEDGE, "S3", &pins_desc[2]);
   request_irq(IRQ_EINT19, buttons_irq,IRQT_BOTHEDGE, "S4", &pins_desc[3]);
 
   return 0;
}

 

static int sixth_drv_read(struct file *file, const char __user *buf, size_t count, loff_t * ppos)
{      

         if(   file->f_flags & O_NONBLOCK ) //非阻塞操作,获取不到则退出
         {
          if(!even_press )   //没有按键按下
                     return -1;
         }

       /*阻塞操作,则直接进入休眠状态,直到有按键按下为止*/         
         /*进程 进入等待队列(休眠状态)*/
         wait_event_interruptible(button_wait, even_press);           

        /*有按键按下,退出等待队列,上传key_val 给用户层*/
         if(copy_to_user(buf,&key_val,sizeof(key_val)))
          return EFAULT;
        　　    even_press=0;          return 0;
}

  static unsigned sixth_poll(struct file *file, poll_table *wait)
{
 　　 unsigned int mask = 0;
      poll_wait(file, &button_wait, wait); // 不会立即休眠
        
      if (even_press)
          mask |= POLLIN | POLLRDNORM;
       return mask;
 }

 
static int sixth_fasync (int fd, struct file *file, int on)
{
  return fasync_helper(fd, file, on, & button_async); //初始化button_async结构体,就能使用kill_fasync()了
}

 

 

static struct file_operations sixth_drv_fops={
         .owner = THIS_MODULE,
         .open = sixth_drv_open,
         .read = sixth_drv_read,
        .release=sixth_drv_class,    //里面添加free_irq函数,来释放中断服务函数
        .poll = sixth_poll,
        .fasync= sixth_fasync,     //初始化异步信号函数
};

 

static  void buttons_timer_function(unsigned long data)   //定时器超时函数
{      
     unsigned int  pin_val=0;     

     if(!irq_dev_id)        //定时器.expires成员=0,会进入一次,若irq_dev_id为0则退出
   {printk("expires: timer out\n");
     return ;  }

    pin_val=s3c2410_gpio_getpin(irq_dev_id->pin);
    if(pin_val)
   {
    /* 按下 (下降沿),清除0x80*/
   key_val=irq_dev_id->pin_status&0xef;
    }
    else
   {
    /*没有按下(上升沿),加上0x80*/
   key_val=irq_dev_id->pin_status|0x80;
    }

    even_press=1;                                        //退出等待队列
    wake_up_interruptible(&button_wait);               //唤醒 中断
    kill_fasync(&button_async, SIGIO, POLL_IN);        //发送SIGIO信号给应用层 

}

volatile int sixth_major;
static int sixth_drv_init(void)
{
   init_timer(&buttons_timer);  //初始化定时器  
   buttons_timer. function= buttons_timer_function;   //定时器超时函数
   add_timer(&buttons_timer);    //添加到内核中


   sixth_major=register_chrdev(0,"sixth_drv",&sixth_drv_fops);  //创建驱动
   sixthdrv_class=class_create(THIS_MODULE,"sixth_dev");    //创建类名
   sixthdrv_class_devs=class_device_create(sixthdrv_class, NULL, MKDEV(sixth_major,0), NULL,"buttons");

   return 0;
}

static int sixth_drv_exit(void)
{
 unregister_chrdev(sixth_major,"sixth_drv");            //卸载驱动 
 class_device_unregister(sixthdrv_class_devs);         //卸载类设       
 class_destroy(sixthdrv_class);                         //卸载类

   del_timer(&buttons_timer);               //删除定时器

 return 0;
}

module_init(sixth_drv_init);
module_exit(sixth_drv_exit); 
MODULE_LICENSE("GPL v2");}