linux驱动简易模版

#include <linux/init.h>
#include <linux/module.h>
#include <linux/fs.h>
#include <linux/cdev.h>

MODULE_LICENSE("GPL");
#define CDD_MAJOR    200//cat /proc/devices找一个尚未使用的
#define CDD_MINOR    0
#define CDD_COUNT    1
dev_t dev = 0;
u32 cdd_major = 0;
u32 cdd_minor = 0;
/*定义cdev类型的变量*/
struct cdev cdd_cdev;

int cdd_open(struct inode* inode, struct file *filp)
{
    printk("enter cdd_open!n");
    return 0;
}

int cdd_read(struct file *filp, char __user *buf, size_t count, loff_t *offset)
{
    printk("enter cdd_read!n");
    return 0;
}

int cdd_write(struct file *filp, const char __user *buf, size_t count, loff_t *offset)
{
    printk("enter cdd_write!n");
    return 0;
}

int cdd_ioctl(struct inode *inode, struct file *filp, unsigned int cmd, unsigned long data)
{
    printk("enter cdd_ioctl!n");
    return 0;
}

int cdd_release(struct inode *inode, struct file *filp)
{
    printk("enter cdd_release!n");
    return 0;
}

struct file_operations cdd_fops = {
    .owner = THIS_MODULE,
    .open = cdd_open,
    .read = cdd_read,
    .write = cdd_write,
    .unlocked_ioctl = cdd_ioctl,
    .release = cdd_release,
    };

int __init cdd_init(void)
{
    int ret = 0;
    if(cdd_major){
        dev = MKDEV(CDD_MAJOR, CDD_MINOR);//生成设备号
        //注册设备号;1、要注册的起始设备号2、连续注册的设备号个数3、名字
        ret = register_chrdev_region(dev, CDD_COUNT, "cdd_demo");
    }else{
        // 动态分配设备号
        ret = alloc_chrdev_region(&dev, cdd_minor, CDD_COUNT, "cdd_demo02");
    }
    
    if(ret < 0){
        printk("register_chrdev_region failed!n");
        goto failure_register_chrdev;
    }
    //获取主设备号
    cdd_major = MAJOR(dev);
    printk("cdd_major = %dn", cdd_major);

    /*初始化cdev*/
    cdev_init(&cdd_cdev, &cdd_fops);
    /*添加cdev到内核*/
    ret = cdev_add(&cdd_cdev, dev, CDD_COUNT);
    if(ret < 0){
        printk("cdev_add failed!n");
        goto failure_cdev_add;
    }
    
    return 0;
failure_cdev_add:
    unregister_chrdev_region(dev, CDD_COUNT);
failure_register_chrdev:
    return ret;
}

void __exit cdd_exit(void)
{
/*逆序消除*/
    //从内核中删除cdev
    cdev_del(&cdd_cdev);
    
    //注销设备号
    unregister_chrdev_region(dev, CDD_COUNT);
}    

module_init(cdd_init);
module_exit(cdd_exit);