//字符设备驱动的另外一种写法：

#include "linux/device.h"

#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/poll.h"

#include "linux/cdev.h"

// 1. 确定主设备号 

static int major;

static int hello_open(struct inode *inode, struct file *file)

{

    printk("hello_open\n");

    return 0;

}

static int hello2_open(struct inode *inode, struct file *file)

{

    printk("hello2_open\n");

    return 0;

}

// 2. 构造file_operations 

static struct file_operations hello_fops = {

    .owner = THIS_MODULE,

    .open  = hello_open,

};

static struct file_operations hello2_fops = {

    .owner = THIS_MODULE,

    .open  = hello2_open,

};

#define HELLO_CNT   2

static struct cdev hello_cdev;

static struct cdev hello2_cdev;

static struct class *cls;

static int hello_init(void)

{

    dev_t devid;

    // 3. 告诉内核 

#if 0

    major = register_chrdev(0, "hello", &hello_fops); // (major,  0), (major, 1), ..., (major, 255)都对应hello_fops 

#else

    if (major) {

        devid = MKDEV(major, 0);

        register_chrdev_region(devid, HELLO_CNT, "hello");  // (major,0~1) 对应 hello_fops, (major, 2~255)都不对应hello_fops 

    } else {

        alloc_chrdev_region(&devid, 0, HELLO_CNT, "hello"); // (major,0~1) 对应 hello_fops, (major, 2~255)都不对应hello_fops 

        major = MAJOR(devid);                     

    }

    cdev_init(&hello_cdev, &hello_fops);

    cdev_add(&hello_cdev, devid, HELLO_CNT);

    devid = MKDEV(major, 2);

    register_chrdev_region(devid, 1, "hello2");

    cdev_init(&hello2_cdev, &hello2_fops);

    cdev_add(&hello2_cdev, devid, 1);

#endif

    cls = class_create(THIS_MODULE, "hello");

    device_create(cls, NULL, MKDEV(major, 0), NULL, "hello0"); // /dev/hello0 

    device_create(cls, NULL, MKDEV(major, 1), NULL, "hello1"); // /dev/hello1 

    device_create(cls, NULL, MKDEV(major, 2), NULL, "hello2"); // /dev/hello2 

    device_create(cls, NULL, MKDEV(major, 3), NULL, "hello3"); // /dev/hello3 

    return 0;

}

static void hello_exit(void)

{

    device_destroy(cls, MKDEV(major, 0));

    device_destroy(cls, MKDEV(major, 1));

    device_destroy(cls, MKDEV(major, 2));

    device_destroy(cls, MKDEV(major, 3));

    class_destroy(cls);

    cdev_del(&hello_cdev);

    unregister_chrdev_region(MKDEV(major, 0), HELLO_CNT);

    cdev_del(&hello2_cdev);

    unregister_chrdev_region(MKDEV(major, 2), 1);

}

module_init(hello_init);

module_exit(hello_exit);

MODULE_LICENSE("GPL");

===================================================================

测试程序：

#include "stdio.h"

#include "stdlib.h"

#include "string.h"

#include "sys/types.h"

#include "sys/stat.h"

#include "fcntl.h"

// hello_test /dev/hello0

void print_usage(char *file)

{

    printf("%s 《dev》\n", file); //“《”实际为“

}

int main(int argc, char **argv)

{

    int fd;

    if (argc != 2)

    {

        print_usage(argv[0]);

        return 0;

    }

    fd = open(argv[1], O_RDWR);

    if (fd < 0)

        printf("can't open %s\n", argv[1]);

    else

        printf("can open %s\n", argv[1]);

    return 0;

}