字符设备驱动-定时器

当我们用阻塞的方式来驱动按键时：

按下按键由于机械按键的波动性，会导致中断处理函数发生多次。

我们可以采用定时器来解决此bug：

Makefile:

KERN_DIR = /work/system/linux-2.6.22.6all:    make -C $(KERN_DIR) M=`pwd` modules clean:    make -C $(KERN_DIR) M=`pwd` modules clean    rm -rf modules.orderobj-m += seventh_drv.o

驱动程序：seventh_drv.c

#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 <asm/arch/regs-gpio.h>  #include <asm/hardware.h>#include <linux/poll.h>static struct fasync_struct *button_async;static struct class *sixthdrv_class;static struct class_device *sixthdrv_class_dev;static DECLARE_WAIT_QUEUE_HEAD(button_waitq);/* 中断事件标志, 中断服务程序将它置1，s3c24xx_sixth_read将它清0 */static volatile int ev_press = 0;struct timer_list buttons_timer;volatile unsigned long *gpfcon;volatile unsigned long *gpfdat;volatile unsigned long *gpgcon;volatile unsigned long *gpgdat;struct pin_desc{    unsigned int pin;    unsigned int key_val;};/* 键值： 按下时，0x01、0x02、0x03 *//* 键值： 松开时，0x81、0x82、0x83 */static unsigned char key_val;struct pin_desc pin_desc[3] = {    {S3C2410_GPF0,0X01},    {S3C2410_GPF2,0X02},    {S3C2410_GPG3,0X03},};//atomic_t canopen = ATOMIC_INIT(1);//定义原子变量canopen并初始化为1static DECLARE_MUTEX(button_lock);     //定义互斥锁static struct pin_desc *irq_pd;static irqreturn_t buttons_irq(int irq, void *dev_id){    /* 设置定时器，发生中断10ms后再去读电平值 */    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、GPG3为中断引脚 */    request_irq(IRQ_EINT0, buttons_irq,IRQT_BOTHEDGE,"s2",&pin_desc[0]);    request_irq(IRQ_EINT2, buttons_irq,IRQT_BOTHEDGE,"s3",&pin_desc[1]);    request_irq(IRQ_EINT11,buttons_irq,IRQT_BOTHEDGE,"s4",&pin_desc[2]);    /* 配置GPF4、5、6为输入引脚 */    *gpfcon &= ~((0x3<<4*2) | (0x3<<5*2) | (0x3<<6*2));    *gpfcon |=  ((1<<4*2) | (1<<5*2) | (1<<6*2));    return 0;}static ssize_t sixth_drv_read (struct file *file, char __user *buf, size_t count, loff_t *ppos){    //看用户需要读取的空间，和这里的是否相同    if(count != 1)        return -EINVAL;    if(file->f_flags & O_NONBLOCK)    {        if(!ev_press)            return -EAGAIN;    }    else    {    /* 如果无按键动作发生，则进行休眠状态 */    /* 如果ev_press等于0，休眠 */    wait_event_interruptible(button_waitq,ev_press);    }    /* 如果有按键动作发生，则返回按键的值 */    copy_to_user(buf,&key_val,1);    ev_press = 0;    return 1;}static int sixth_drv_close (struct inode *inode, struct file *file){    //atomic_inc(&canopen);     /* 释放信号量 */    up(&button_lock);    free_irq(IRQ_EINT0,  &pin_desc[0]);    free_irq(IRQ_EINT2,  &pin_desc[1]);    free_irq(IRQ_EINT11, &pin_desc[2]);    return 0;}static unsigned int sixth_drv_poll(struct file *file, struct poll_table_struct *wait){    unsigned int mask = 0;    poll_wait(file, &button_waitq, wait);    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,};int major; static int 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);        *gpfdat |= ((1<<4) | (1<<5) | (1<<6));    }    else    {        /* 按下 */        key_val = pindesc->key_val;        *gpfdat &= ~((1<<4) | (1<<5) | (1<<6));    }    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;        major = register_chrdev(0,"sixth_drv",&sixth_drv_fops);        sixthdrv_class = class_create(THIS_MODULE,"sixthdrv");        sixthdrv_class_dev = class_device_create(sixthdrv_class,NULL,MKDEV(major,0),NULL,"buttons");        gpfcon = (volatile unsigned long *)ioremap(0x56000050,16);        gpfdat = gpfcon + 1;        gpgcon = (volatile unsigned long *)ioremap(0x56000060,16);        gpgdat = gpgcon + 1;        return 0;}static int 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");

驱动测试程序：seventhdrvtest.c

    #include <sys/types.h>      #include <sys/stat.h>      #include <fcntl.h>      #include <stdio.h>      #include <poll.h>    #include <signal.h>    #include <sys/types.h>    #include <unistd.h>    /*      * sixthdrvtest     */    int fd;    void czg_signal_handler(int signum)    {        unsigned char key_val = 0;        read(fd,&key_val,1);        printf("key_val: 0x%x\n",key_val);    }    int main(int argc, char **argv)    {        int ret;        int oflags;        unsigned char key_val = 0;        //signal(SIGIO,czg_signal_handler);        fd = open("/dev/buttons",O_RDWR);        if(fd < 0)        {            printf("can't open!\n");            return -1;        }        //fcntl(fd,F_SETOWN,getpid()); // 告诉内核，发给谁        //oflags = fcntl(fd,F_GETFL);        //fcntl(fd,F_SETFL,oflags | FASYNC); // 改变fasync标记，        //最终会调用到驱动的faync > fasync_helper：初始化/释放fasync_struct        //然后当按键按下时候，在irqreturn_t buttons_irq中断处理中调用kill_fasync        while(1)        {            ret = read(fd,&key_val,1);            printf("key_val: 0x%x,ret = %d\n",key_val,ret);            //sleep(4);        }        return 0;    }