OK6410(256M RAM,1G SLC NAND)Linux-3.8.3驱动(5.2.5)按键驱动-定时器防抖

首先定义一个定时器button_timer
在init入口函数中初始化该定时器、定义定时器处理函数、add_timer
按下按键后，发生中断，在中断服务函数中不再处理中断，而是修改定时器的超时时间为10ms，超时后触发定时器处理函数来处理中断（读取按键值等过程）。

    若按键按下后不断有抖动导致中断发生，这些中断将使得中断服务程序不断的重新修改定时器的超时时间为10ms，由于各个抖动之间的时间间隙不太可能超过10ms，所以抖动过程中不会触发触发定时器处理函数来处理中断，这期间的按键值也不会被读取。最后一个抖动结束后，由于没有新的中断来修改定时器超时时间，经过10ms后定时器超时，触发定时器处理函数来处理中断，读取按键值。

驱动程序代码如下

//moudle.h 包含了大量加载模块需要的函数和符号的定义
#include <linux/module.h>
//kernel.h以便使用printk()等函数
#include <linux/kernel.h>
//fs.h包含常用的数据结构，如struct file等
#include <linux/fs.h>
//uaccess.h 包含copy_to_user()，copy_from_user()等函数
#include <linux/uaccess.h>
//io.h 包含inl()，outl()，readl()，writel()等IO口操作函数
#include <linux/io.h>
#include <linux/miscdevice.h>
#include <linux/pci.h>
//init.h来指定你的初始化和清理函数，例如：module_init(init_function)、module_exit(cleanup_function)
#include <linux/init.h>
#include <linux/delay.h>
#include <linux/device.h>
#include <linux/cdev.h>
#include <linux/gpio.h>
#include <linux/irq.h>
#include <linux/sched.h>
#include <linux/interrupt.h>
#include <linux/poll.h>
//irq.h中断与并发请求事件
#include <asm/irq.h>
//下面这些头文件是IO口在内核的虚拟映射地址，涉及IO口的操作所必须包含
//#include <mach/gpio.h>
#include <mach/regs-gpio.h>
#include <plat/gpio-cfg.h>
#include <mach/hardware.h>
#include <mach/map.h>


static struct class *button_stab_class;
static int major;

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

static struct fasync_struct *button_async;

static struct timer_list button_timer;//定时器

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

static DEFINE_SEMAPHORE(button_lock); //linux-2.6.36后DECLARE_MUTEX换成了DEFINE_SEMAPHORE

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

static unsigned char button_val;

static struct pin_desc pins_desc[6] = {
    {S3C64XX_GPN(0), 0x01},
    {S3C64XX_GPN(1), 0x02},
    {S3C64XX_GPN(2), 0x03},
    {S3C64XX_GPN(3), 0x04},
    {S3C64XX_GPN(4), 0x05},
    {S3C64XX_GPN(5), 0x06},
};

static struct pin_desc *irq_pd;

/*中断服务函数*/
/* 键值: 按下时, 0x01, 0x02, 0x03, 0x04 ...*/
/* 键值: 松开时, 0x81, 0x82, 0x83, 0x84 ...*/
static irqreturn_t button_stab_irq(int irq, void *dev_id)
{
    /* 10ms后启动定时器 */
    irq_pd = (struct pin_desc *)dev_id;
    mod_timer(&button_timer, jiffies+HZ/100);  //jiffies是系统的定时器时间，HZ/100表示10ms
    return IRQ_HANDLED;
}

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

    if (!pindesc)
        return;

    pinval = gpio_get_value(pindesc->pin);

    if (pinval)
    {
        /* 松开 */
        button_val = 0x80 | pindesc->button_val;
    }
    else
    {
        /* 按下 */
        button_val = pindesc->button_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);//通过这个函数去发送信号给应用程序
}


static int button_stab_open(struct inode *inode, struct file *file)
{
    int ret;

#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);
    }


    /*request_irq注册中断
     *第一个参数是中断号，也是中断处理函数button_stab的第一个参数
     *第二个参数是中断处理函数
     *第三个参数是中断触发方式
     *第四个参数是设备名称
     *第五个参数是设备ID，也是中断处理函数button_stab的第二个参数
     */
    ret = request_irq(IRQ_EINT(0), button_stab_irq, IRQ_TYPE_EDGE_BOTH, "k1", &pins_desc[0]);
    if (ret){
        printk("request IRQ_EINT(0) error!\n");
        free_irq(IRQ_EINT(0), &pins_desc[0]);
    }
    ret = request_irq(IRQ_EINT(1), button_stab_irq, IRQ_TYPE_EDGE_BOTH, "k2", &pins_desc[1]);
    if (ret){
        printk("request IRQ_EINT(1) error!\n");
        free_irq(IRQ_EINT(1), &pins_desc[1]);
    }

    ret = request_irq(IRQ_EINT(2), button_stab_irq, IRQ_TYPE_EDGE_BOTH, "k3", &pins_desc[2]);
    if (ret){
        printk("request IRQ_EINT(2) error!\n");
        free_irq(IRQ_EINT(2), &pins_desc[2]);
    }

    ret = request_irq(IRQ_EINT(3), button_stab_irq, IRQ_TYPE_EDGE_BOTH, "k4", &pins_desc[3]);
    if (ret){
        printk("request IRQ_EINT(3) error!\n");
        free_irq(IRQ_EINT(3), &pins_desc[3]);
    }

    ret = request_irq(IRQ_EINT(4), button_stab_irq, IRQ_TYPE_EDGE_BOTH, "k5", &pins_desc[4]);
    if (ret){
        printk("request IRQ_EINT(4) error!\n");
        free_irq(IRQ_EINT(4), &pins_desc[4]);
    }

    ret = request_irq(IRQ_EINT(5), button_stab_irq, IRQ_TYPE_EDGE_BOTH, "k6", &pins_desc[5]);
    if (ret){
        printk("request IRQ_EINT(5) error!\n");
        free_irq(IRQ_EINT(5), &pins_desc[5]);
    }
    return 0;
}

static ssize_t button_stab_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 */
        /*ev_press=0时休眠，ev_press=1时继续向下执行程序*/
        wait_event_interruptible(button_waitq, ev_press);
    }

    /* 如果有按键动作, 返回键值 */
    if( copy_to_user(buf, &button_val, 1) ){
        printk("error in function ‘copy_to_user’ !\n");
            return -EFAULT;
    }

    ev_press = 0;
    return 0;
}

static ssize_t button_stab_write(struct file *file, const char __user *buf, size_t count, loff_t * ppos)
{
    return 0;
}

static int button_stab_release(struct inode *inode, struct file *file)
{
    //atomic_inc(&canopen);
    free_irq(IRQ_EINT(0), &pins_desc[0]);
    free_irq(IRQ_EINT(1), &pins_desc[1]);
    free_irq(IRQ_EINT(2), &pins_desc[2]);
    free_irq(IRQ_EINT(3), &pins_desc[3]);
    free_irq(IRQ_EINT(4), &pins_desc[4]);
    free_irq(IRQ_EINT(5), &pins_desc[5]);
    up(&button_lock);

    return 0;
}

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

static struct file_operations button_stab_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 = button_stab_open,
    .read = button_stab_read,
    .write = button_stab_write,
    .release = button_stab_release,
    .poll = button_stab_poll,
    .fasync     = button_stab_fasync,
};

static int button_stab_init(void)
{
    init_timer(&button_timer);//初始化定时器
    button_timer.function = button_timer_function;//设置定时器处理函数
    add_timer(&button_timer);

    major = register_chrdev(0, "button_stab_dev", &button_stab_fops);//注册，告诉内核
    button_stab_class = class_create(THIS_MODULE, "button_stab_cls");
    device_create(button_stab_class, NULL, MKDEV(major, 0), NULL, "button_stab");/* /dev/button_stab */

    return 0;
}

static void button_stab_exit(void)
{
    unregister_chrdev(major, "button_stab_cls");
    device_destroy(button_stab_class, MKDEV(major, 0));
    class_destroy(button_stab_class);
}

module_init(button_stab_init);
module_exit(button_stab_exit);

MODULE_LICENSE("GPL");