字符设备驱动程序之定时器防抖动

ys9815076

今天看了韦东山视频第12课第8节讲的是字符设备驱动程序之定时器防抖动，该视频详细的讲解了按键防抖动的原理：当你按一次按健时，由于按健有反应时间、有抖动，可能你按一次机器感应到几次，防抖就是让在按键正常反应时间内机器只感应一次按键效果，防止误操作。当按键发生时产生中断，在中断服务程序中修改一个定时器的定时时间为10ms,并从10ms开始重新计数。定时器时间到后产生定时器中断，按键处理放在定时器中断里面。这样当10ms内有多个中断发生时只有最后一个中断起作用，以达到消除抖动的目的。
韦东山视频讲得非常好，视频介绍及下载地址：http://www.100ask.net/showtopic-3568.aspx
一、开发环境
•主  机：VMWare--Fedora 9
•Kernel：linux-2.6.32.2
•编译器：arm-linux-gcc-4.3.2
二、参考驱动程序
#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/uaccess.h>
#include <asm/irq.h>
#include <asm/io.h>
#include <linux/interrupt.h> /*linux中断*/
#include <mach/regs-gpio.h>
#include <mach/hardware.h>
#include <linux/device.h>
#include <linux/cdev.h>
#include <mach/gpio-fns.h>
#include <linux/sched.h>
struct cdev cdev;
#include <linux/poll.h>
static struct class *sixthdrv_class;
//volatile unsigned long *gpfcon;
//volatile unsigned long *gpfdat;
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 0x05, 0x06 */
/* 键值: 松开时, 0x81, 0x82, 0x83, 0x84 0x85, 0x86*/
static unsigned char key_val;
struct pin_desc pins_desc[6] = {
{S3C2410_GPG(0), 0x01},
{S3C2410_GPG(3), 0x02},
{S3C2410_GPG(5), 0x03},
{S3C2410_GPG(6), 0x04},
{S3C2410_GPG(7), 0x05},
{S3C2410_GPG(11),0x06},
};
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

static irqreturn_t buttons_irq(int irq, void *dev_id)
{
/* 发生中断20ms后启动定时器 */
irq_pd = (struct pin_desc *)dev_id;
mod_timer(&buttons_timer, jiffies+HZ/50);
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);
}
/* 设置GPG0,3,5,6,7,11为中断引脚 ,寄存器与中断引脚的联结*/
s3c2410_gpio_cfgpin(S3C2410_GPG(0),S3C2410_GPG0_EINT8);
s3c2410_gpio_cfgpin(S3C2410_GPG(3),S3C2410_GPG3_EINT11);
s3c2410_gpio_cfgpin(S3C2410_GPG(5),S3C2410_GPG5_EINT13);
s3c2410_gpio_cfgpin(S3C2410_GPG(6),S3C2410_GPG6_EINT14);
s3c2410_gpio_cfgpin(S3C2410_GPG(7),S3C2410_GPG7_EINT15);
s3c2410_gpio_cfgpin(S3C2410_GPG(11),S3C2410_GPG11_EINT19);
/*中断的注册*/
request_irq(IRQ_EINT8,  buttons_irq, IRQF_DISABLED, "S1", &pins_desc[0]);
request_irq(IRQ_EINT11, buttons_irq, IRQF_DISABLED, "S2", &pins_desc[1]);
request_irq(IRQ_EINT13, buttons_irq, IRQF_DISABLED, "S3", &pins_desc[2]);
request_irq(IRQ_EINT14, buttons_irq, IRQF_DISABLED, "S4", &pins_desc[3]);
request_irq(IRQ_EINT15, buttons_irq, IRQF_DISABLED, "S5", &pins_desc[4]);
request_irq(IRQ_EINT19, buttons_irq, IRQF_DISABLED, "S6", &pins_desc[5]);
/*中断类型的设置，为双边缘触发*/
set_irq_type(IRQ_EINT8,IRQ_TYPE_EDGE_BOTH);
set_irq_type(IRQ_EINT11,IRQ_TYPE_EDGE_BOTH);
set_irq_type(IRQ_EINT13,IRQ_TYPE_EDGE_BOTH);
set_irq_type(IRQ_EINT14,IRQ_TYPE_EDGE_BOTH);
set_irq_type(IRQ_EINT15,IRQ_TYPE_EDGE_BOTH);
set_irq_type(IRQ_EINT19,IRQ_TYPE_EDGE_BOTH);  
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_EINT8,  &pins_desc[0]);
free_irq(IRQ_EINT11, &pins_desc[1]);
free_irq(IRQ_EINT13, &pins_desc[2]);
free_irq(IRQ_EINT14, &pins_desc[3]);
free_irq(IRQ_EINT15, &pins_desc[4]);
free_irq(IRQ_EINT19, &pins_desc[5]);
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 sixth_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,
};
/*
  * 确定按键值
  */
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);
}
int major;
static int sixth_drv_init(void)
{
int result;
   dev_t devno = MKDEV(major, 0);
   /* 静态申请设备号*/
   if (major)
    result = register_chrdev_region(devno, 1, "sixth_drv_new");
   else  /* 动态分配设备号 */
   {
     result = alloc_chrdev_region(&devno, 0, 1, "sixth_drv_new");
     major = MAJOR(devno);
   }  
  
   if (result < 0)
     return result;
   /*初始化cdev结构*/
   cdev_init(&cdev, &sixth_drv_fops);
   cdev.owner = THIS_MODULE;
   cdev.ops = &sixth_drv_fops;
  
   /* 注册字符设备 */
   cdev_add(&cdev, MKDEV(major, 0), 1);
sixthdrv_class = class_create(THIS_MODULE, "sixth_drv");
device_create(sixthdrv_class, NULL, MKDEV(major,0), NULL, "buttons"); /* /dev/buttons */
init_timer(&buttons_timer);
buttons_timer.function = buttons_timer_function;
//buttons_timer.expires  = 0;
add_timer(&buttons_timer);
  
// gpfcon = (volatile unsigned long *)ioremap(0x56000050, 16);
// gpfdat = gpfcon + 1;
return 0;
}
static void sixth_drv_exit(void)
{
   cdev_del(&cdev);   /*注销设备*/
   
        unregister_chrdev_region(MKDEV(major, 0), 1); /*释放设备号*/
   device_destroy(sixthdrv_class,MKDEV(major,0));  //释放设备文件
   class_destroy(sixthdrv_class);//释放设备类
// iounmap(gpfcon);
//return 0;
}
module_init(sixth_drv_init);
module_exit(sixth_drv_exit);
MODULE_LICENSE("GPL");

1060295719

谢谢，了解了

sxhhhjicbb

看看。

Andy126