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ÏÈÊÇÍ·Îļþ demo.h
#ifndef _DEMO_H_
#define _DEMO_H_
#include <linux/ioctl.h> /* needed for the _IOW etc stuff used later */
/********************************************************
* Macros to help debugging
********************************************************/
#undef PDEBUG             /* undef it, just in case */
#ifdef DEMO_DEBUG
#ifdef __KERNEL__
#    define PDEBUG(fmt, args...) printk( KERN_DEBUG "DEMO: " fmt, ## args)
#else//usr space
#    define PDEBUG(fmt, args...) fprintf(stderr, fmt, ## args)
#endif
#else
# define PDEBUG(fmt, args...) /* not debugging: nothing */
#endif
#undef PDEBUGG
#define PDEBUGG(fmt, args...) /* nothing: it's a placeholder */
//É豸ºÅ
#define DEMO_MAJOR 224
#define DEMO_MINOR 0
#define COMMAND1 1
#define COMMAND2 2
//×Ô¼º¶¨ÒåµÄÉ豸½á¹¹
struct DEMO_dev
{
    struct cdev cdev;    /* Char device structure        */
};
//º¯ÊýÉêÃ÷ Ô­À´LinuxÇý¶¯³ÌÐòÉè¼ÆÕâô¼òµ¥ Ö»ÐèҪʵÏÖÕâô¼¸¸öº¯Êý¾Í¿ÉÒÔÁË
ssize_t DEMO_read(struct file *filp, char __user *buf, size_t count,
                   loff_t *f_pos);
ssize_t DEMO_write(struct file *filp, const char __user *buf, size_t count,
                    loff_t *f_pos);
loff_t DEMO_llseek(struct file *filp, loff_t off, int whence);
int     DEMO_ioctl(struct inode *inode, struct file *filp,
                &nbs