ioctl方法简单用法

#include <linux/module.h>
#include <linux/init.h>
#include <linux/ioctl.h>
#include <linux/fs.h>
#include <linux/kdev_t.h>
#include <linux/cdev.h>
#include <asm/uaccess.h>
#include <linux/types.h>
#include <linux/kernel.h>

#define DEVICE_NAME "chardev"

#define TEST_MAGIC 'k'
#define IOCTL_PRINTK _IO(TEST_MAGIC, 0)

static int chardev_ioctl(struct inode *inodp, struct file *filp, unsigned int cmd, unsigned long arg);

static struct file_operations chardev_fops = {
        .ioctl = chardev_ioctl,
};

static struct cdev *cdevp = NULL;
static dev_t devno;

static int chardev_ioctl(struct inode *inodp, struct file *filp, unsigned int cmd, unsigned long arg)
{
        if (cmd == IOCTL_PRINTK)
                printk(KERN_ALERT "chardev_ioctl running.\n");

        return 0;
}

static int __init chardev_init(void)
{
        int ret;

        ret = alloc_chrdev_region(&devno, 0, 1, DEVICE_NAME);
        if (ret < 0)
                goto out;

        cdevp = cdev_alloc();
        if (!cdevp)
                goto alloc_err;

        cdev_init(cdevp, &chardev_fops);
        ret = cdev_add(cdevp, devno, 1);
        if (!ret)
                goto out;

        cdev_del(cdevp);
alloc_err:
        unregister_chrdev_region(devno, 1);
out:
        return ret;
}

static void __exit chardev_exit(void)
{
        cdev_del(cdevp);

        unregister_chrdev_region(devno, 1);
}

MODULE_LICENSE("GPL");

module_init(chardev_init);
module_exit(chardev_exit);


应用程序：
cat ../2.c
#include <stdio.h>
#include <fcntl.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include <linux/ioctl.h>

#define TEST_MAGIC 'k'
#define IOCTL_PRINTK _IO(TEST_MAGIC, 0)

int main(void)
{
        int fd;

        fd = open("/dev/chardev", O_RDWR);
        if (fd == -1)
                goto err;

        if (ioctl(fd, IOCTL_PRINTK) == -1)
                perror("ioctl");

        return 0;
err:
        return -1;
}