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字符设备驱动框架代码的编写

程序员文章站 2022-03-22 20:22:17
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命令:lsmod —— 查看当前内核中加载了那些模块

字符设备驱动框架代码的编写

 

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

#define BASEMINOR 0
#define COUNT     3
#define NAME      "cdev_demo"

dev_t devno = 0;
struct cdev *cdevp = NULL;
int demo_open(struct inode *inode, struct file *filp)
{
	printk(KERN_DEBUG "---%s---%s---%d---\n",__FILE__,__func__,__LINE__);
	return 0;
}
int demo_release(struct inode *inode, struct file *filp)
{
	printk(KERN_DEBUG "---%s---%s---%d---\n",__FILE__,__func__,__LINE__);
	return 0;
}
struct file_operations fops = {
	.owner    = THIS_MODULE,
	.open     = demo_open,
	.release  = demo_release,
};
int __init demo_init(void)
{
	int ret = 0;
	//0.申请设备号-内核分配主设备号,次设备好从0开始,共三个(0,1,2)
	ret = alloc_chrdev_region(&devno,BASEMINOR,COUNT, NAME);
	if(ret < 0){
		printk(KERN_ERR "alloc_chrdev_region failed...\n");
		goto err0;
	}
	printk(KERN_INFO "---major:%d---\n",MAJOR(devno));
	//1.分配cdev结构体
	cdevp = cdev_alloc();
	if(cdevp == NULL){
		printk(KERN_ERR "cdev_alloc failed...\n");
		ret = -ENOMEM;
		goto err1;		
	}
	//2.初始化cdev结构体
	cdev_init(cdevp, &fops);

	//3.将cdev结构体添加到内核中,由内核对驱动进行统一的管理
	ret = cdev_add(cdevp, devno, COUNT);
	if(ret < 0){
		printk(KERN_ERR "cdev_add failed...\n");
		goto err1;
	}
	printk(KERN_DEBUG "---%s---%s---%d---\n",__FILE__,__func__,__LINE__);
	return 0;
err1:
	unregister_chrdev_region(devno, COUNT);
err0:
	return ret;
}
void __exit demo_exit(void)
{
	cdev_del(cdevp);
	unregister_chrdev_region(devno, COUNT);
	printk(KERN_DEBUG "---%s---%s---%d---\n",__FILE__,__func__,__LINE__);
}

module_init(demo_init);
module_exit(demo_exit);
MODULE_LICENSE("GPL");

字符设备驱动框架代码的编写

相关标签: 驱动程序