6.5 实例 秒字符设备 《linux设备驱动开发详解》

linux设备驱动开发详解p207内核定时器---秒字符设备

代码附件：  timer_me.rar   将rar修改为tar.bz2

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#include <linux/module.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/fs.h>//container_of
#include <linux/types.h>//atomic_t
#include <linux/cdev.h>//cdev
#include <asm/uaccess.h>//put_user
#include <linux/slab.h>//kmalloc
#include <linux/moduleparam.h>//moudule_param

static int second_major =240;
module_param(second_major,int,00644);//

struct second_dev{
    struct cdev cdev;
    atomic_t counter;
    struct timer_list s_timer;
};
struct second_dev *second_devp;

static void second_timer_handler(unsigned long arg)
{
    mod_timer(&second_devp->s_timer,jiffies+HZ);
    atomic_inc(&second_devp->counter);//puls 1
    printk(KERN_NOTICE"currretn jiffies is %ld\n",jiffies);
}

int second_open(struct inode *inode,struct file *filp)
{
    struct second_dev *dev;
    dev = container_of(inode->i_cdev,struct second_dev,cdev);
    filp->private_data = dev;

    init_timer(&second_devp->s_timer);
    second_devp->s_timer.function = &second_timer_handler;
    second_devp->s_timer.expires = jiffies + HZ;
    add_timer(&second_devp->s_timer);
    atomic_set(&second_devp->counter,0);
    return 0;
}

int second_release(struct inode *inode,struct file *filp)
{
    del_timer(&second_devp->s_timer);
    return 0;
}

static ssize_t second_read(struct file *filp, char __user *buf,size_t count,off_t *ppos)
{
    int counter;
    struct second_dev *dev = filp->private_data;

//    counter = atomic_read(&second_devp->counter);
    counter = atomic_read(&dev->counter);
    if(put_user(counter,(int *)buf))
        return -EFAULT;
    else
        return sizeof(unsigned int);
}

static const struct file_operations second_fops={
    .owner = THIS_MODULE,
    .open = second_open,
    .release = second_release,
    .read = second_read,
};

static void second_setup_cdev(struct second_dev *dev ,int index)
{
    int err;
    int devno = MKDEV(second_major,index);
    cdev_init(&dev->cdev,&second_fops);
    dev->cdev.owner = THIS_MODULE;
    err = cdev_add(&dev->cdev,devno,1);
    if(err)
        printk(KERN_INFO"error %d adding LED %d\n",err,index);
}

static int __init second_init(void)
{
    int ret;
    dev_t devno = MKDEV(second_major,0);

    if(second_major)
    {
        ret = register_chrdev_region(devno,1,"second");
    }
    else
    {
        ret = alloc_chrdev_region(&devno,0,1,"second");
        second_major = MAJOR(devno);
    }

    if(ret < 0)
        return ret;

    second_devp = kmalloc(sizeof(struct second_dev),GFP_KERNEL);
    if(!second_devp)
    {
        ret = -ENOMEM;
        goto fail_malloc;
    }

    memset(second_devp,0,sizeof(struct second_dev));
    second_setup_cdev(second_devp,0);
    return 0;
fail_malloc:
    unregister_chrdev_region(devno,1);
    return ret;
}

static void __exit second_exit(void)
{
    cdev_del(&second_devp->cdev);
    kfree(second_devp);
    unregister_chrdev_region(MKDEV(second_major,0),1);
}

MODULE_LICENSE("GPL");
module_init(second_init);
module_exit(second_exit);

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>//O_RDONLY

int main(int argc, char **argv)
{
    int fd;
    int counter = 0;
    int old_counter = 0;

    fd = open("/dev/second",O_RDONLY);
    if(fd != -1)
    {
        while(1)
        {
            read(fd,&counter,sizeof(unsigned int));
            if(counter != old_counter)
            {
                printf("secons after open /dev/second:%d\n",counter);
                old_counter = counter;
            }
        }
    }
    else
    {
        printf("device open faile\n");
        exit(EXIT_FAILURE);
    }
}

使用方法：

ywx@ywx:~/Desktop/module/baohua/timer/timer_me$ ls
app       modules.order   timer.c   timer.mod.c  timer.o
Makefile  Module.symvers  timer.ko  timer.mod.o
ywx@ywx:~/Desktop/module/baohua/timer/timer_me$ sudo insmod ./timer.ko
ywx@ywx:~/Desktop/module/baohua/timer/timer_me$ cat /proc/devices | grep second
240 second
ywx@ywx:~/Desktop/module/baohua/timer/timer_me$ sudo mknod /dev/second c 240 0

root@ywx:/home/ywx/desktop/module/baohua/timer/timer_me/app# ls
app  app.c  app.c.old  app.o  Makefile
root@ywx:/home/ywx/desktop/module/baohua/timer/timer_me/app# ./app
secons after open /dev/second:1
secons after open /dev/second:2
secons after open /dev/second:3
^C
root@ywx:/home/ywx/desktop/module/baohua/timer/timer_me/app#

root@ywx:/home/ywx/desktop/module/baohua/timer/timer_me/app# dmesg | tail -20
[ 6977.244239] currretn jiffies is 1669311
[ 6978.245753] currretn jiffies is 1669561
[ 6979.244045] currretn jiffies is 1669811
[ 6980.244742] currretn jiffies is 1670061
[ 6981.244750] currretn jiffies is 1670311
[ 7448.756231] currretn jiffies is 1787189
[ 7449.756231] currretn jiffies is 1787439