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

#include <linux/errno.h>
#include <linux/mm.h>
#include <linux/sched.h>
#include <asm/io.h>
#include <asm/system.h>
#include <asm/uaccess.h>

#include <linux/device.h>

#define _DEBUG_
#define	DEVICE_NUM	1			//需要申请的设备数量

//结构体声明,字符设备结构体
struct device_dev{
	struct 		cdev cdev;                                  
};

//全局变量
//默认主设备号,0为自动分配,否则外部设置 
int g_major = 0;
struct class *g_my_class;
//设备结构指针
static struct device_dev *g_devp;
//设置字符设备对应的fops
static struct file_operations device_fops = {
  	.owner		= THIS_MODULE,
}; 

/* 
    名称: device_setup_cdev 
    功能: 字符设备注册 
    参数:  
            输入: 
                1:struct cdev *_pcdev,						//cdev指针
				2:struct file_operations *_pdevice_fops,	//文件操作结构体指针
				3:int _major,					//设备主设备号
				4:int _index					//设备从设备号
    返回值: 
            return 0; 	//注册成功
			其他		//注册失败
*/
static int device_setup_cdev(struct cdev *_pcdev,struct file_operations *_pdevice_fops,
	int _major,int _index)
{
	int err;
	
	dev_t devno = MKDEV(_major,_index);
	
	cdev_init(_pcdev,_pdevice_fops);                                   //初始化字符设备,并跟fops建立链接
	_pcdev->owner = THIS_MODULE;
	err = cdev_add(_pcdev,devno,1);                                    //向内核增加当前字符设备
	
	if (err) {
		return err;
	}
	
	return 0;
}

/* 
    名称: register_region 
    功能: 申请设备号, *_pmajor = 0; 则自动分配
    参数:  
            输出: 
                1:int *_pmajor,				//返回主设备号
			输入:	
				2:const int _dev_size			//需要注册的设备数量
				3:const char *_p_dev_name,		//注册的设备名字
    返回值: 
            return 0; 		//注册成功
			其他		//注册失败
*/
static int register_region(int *_pmajor,const int _dev_size,const char *_p_dev_name)
{
	int 	result = 0;
	dev_t 	devno;
	if (*_pmajor == 0) {
		result = alloc_chrdev_region(&devno,0,_dev_size,_p_dev_name);
		*_pmajor = MAJOR(devno);
	} else {
		devno  = MKDEV(*_pmajor,0); 
	    result = register_chrdev_region(devno,_dev_size,_p_dev_name);
	}
	return result;
}

/* 
    名称: device_class 
    功能: 创建设备文件
    参数:  
            输入: 
				1:int _major,					//主设备号
				3:const char *_szclass_name,		//类名
				4:const char *_szdevice_name	//设备名
			输出:
				2:struct class **_p_class,		//返回类名结构体地址
    返回值: 
            return 0; 	//注册成功
			return -1	//注册失败
*/
static int device_class(int _major,struct class **_p_class,const \
	char *_szclass_name,const char *_szdevice_name)
{
	//创建设备文件
	*_p_class = class_create(THIS_MODULE, _szclass_name);
	if(IS_ERR(*_p_class)) 
	{
		return -1;
	}
	
	device_create(*_p_class, NULL, MKDEV(_major, 0),0,_szdevice_name);
	
	return 0;
}
static int __init initialization_function(void)
{
	/*初始化代码*/
	int 	result;
	//添加设备号
	if(register_region(&g_major,DEVICE_NUM,"interrupt"))
	{
		result = -1;
		goto fail_register; 	
	}
	//分配设备结构体空间
	g_devp = kmalloc(sizeof(struct device_dev),GFP_KERNEL);
	if (!g_devp) {		
		result = -ENOMEM;
		goto fail_malloc;	
	}
	
	//注册字符设备
	if (device_setup_cdev(&(g_devp->cdev),&device_fops,g_major,0)) {
		result = -1;
		goto fail_setup_cdev;		
	}

	//生成设备文件
	if(device_class(g_major,&g_my_class,"chass_inputer","device_interrupt")){
		result = -1;
		goto fail_class;
	}

	printk(KERN_INFO "initialization_function Sucessful %d\n",g_major);

	return 0;
	
fail_class:
	cdev_del(&(g_devp->cdev));
fail_setup_cdev:
	kfree(g_devp);							//释放已申请的内存
fail_malloc:
	unregister_chrdev_region(MKDEV(g_major,0),DEVICE_NUM); 
fail_register:	
#ifdef _DEBUG_
	printk(KERN_INFO "fail_malloc\n");
#endif
	return result;
}

static void __exit cleanup_function(void)
{
	/*释放代码*/
	device_destroy(g_my_class, MKDEV(g_major, 0)); 		//delete device node under /dev
    class_destroy(g_my_class);                          //delete class created by us
	cdev_del(&(g_devp->cdev));							//删除cdev结构
	if(!g_devp)
		kfree(g_devp);											//释放已申请的内存
	unregister_chrdev_region(MKDEV(g_major,0),DEVICE_NUM);	//注销设备区域
	printk(KERN_INFO "Sucessful cleanup_function\n");
}

//注册模块加载卸载函数
module_init(initialization_function);						//指定模块加载函数
module_exit(cleanup_function);							//指定模块卸载函数

//模块参数
module_param(g_major,int,S_IRUGO);               		//导出参数,为了人工设定主设备号

//模块信息及许可证
MODULE_AUTHOR("LvApp");									//作者
MODULE_LICENSE("Dual BSD/GPL");							//许可证
MODULE_DESCRIPTION("A simple module");						//描述
MODULE_ALIAS("LvApp's device");								//别名