tongdev.c

一个linux字符设备驱动。根据操作系统课本上的实验内容设计编写

struct device_struct{
const char *name;
struct file_operations *chops;
};
static struct device_struct chrdevs[MAX_CHRDEV];
typedef struct tongdev_Dev{
void **data;
int quantum;                //the capacity of recent
int qset;                   //the num of the array
unsigned long size;
unsigned int access_key;    //used by tongdevuid and tongdevpriv
unsigned int usage;         //lock control
struct tongdev_Dev *next;
}tongdev

static int tongdev_open(struct inode *inode,struct file *filp);//open char equ
static int tongdev_release(struct inode *inode,struct file *filp);//release char equ
static ssize_t tongdev_write(struct inode *inode,struct file *filp,const char*buffer,int count);//write data to char equ
static ssize_t tongdev_read(struct inode*inode,struct file*filp,char*buffer,int count);//read data from char equ
static int tongdev_ioctl(struct inode*inode,struct file*filp,unsigned long int cmd,unsigned long arg);//char equ control
struct file_operations chr_fops={
null,                   //seek
tongdev_read,           //read
tongdev_write,          //write
null,                   //readdir
null,                   //poll
tongdev_ioctl,          //ioctl
null,                   //mmap
tongdev_open,           //open
null,                   //flush
tongdev_release,        //release
null,                   //fsync
null,                   //fasync
null,                   //check media change
null,                   //revalidate
null,                   //lock
};

#include <linux/fs.h>
#include <linux/errno.h>
int register_chrdev(unsigned int major,const char *name,struct file_operation *fops);

int tongdev_open(struct inode *inode,struct file *filp) //open
{mod_inc_use_count ; //increase these mod's user
printk("This chrdev is in open\n");
return 0;
}

int tongdev_write(struct inode *inode,struct file *filp, const char *buffer, int count) //write
{if (count<0)
return -einval;
if(tongdev.usage||tongdev.new_msg)
return -ebusy;
tongdev.usage=1;
kfree(tongdev.data);
data=kmalloc(sizeof(char)*(count+1),gef_kernel);
if (!tongdev.data){
return -enomem;
}
copy_from_user(tongdev.data,buffer,count+1);
tongdev.usage=0;
tongdev.new_msg=1;
return count;
}

int tongdev_read(struct inode *inode,struct file *filp,char *buffer, int count) //read
{int length;
if(count<0)
return -einval;
if(tongdev.usage)
return -ebusy;
tongdev.usage=1;
if(tongdev.data==0)
return 0;
length=strlen(tongdev.data);
if(length<count)
count=length;
copy_to_user(buf,tongdev.data,count+1);
tongdev.new_msg=0;
tongdev.usage=0;
return count;
}

#include <linux/ioctl.h>
#define tongdev_major 0
#define tongdev_magic tongdev_major
#define tongdev_reset _IO(tongdev_magic,0)//reset the data
#define tongdev_query_new_msg _IO(tongdev_magic,1)//check the new message
#define tongdev_query_msg_length _IO(tongdev_magic,2)//get the message length
#define ioc_new_msg 1 
static int usage,new_msg; //control tag
static char *data;
int tongdev_ioctl(struct inode *inode,struct file *filp,unsigned long int cmd, unsigned long arg){
int ret=0;
switch(cmd){
case tongdev_reset:
                   kfree(data);
                   data=null;
                   usage=0;
                   new_msg=0;
break;
case tongdev_query_new_msg:
                   if(new_msg)
                   return ioc_new_msg;
break;
case tongdec_query_msg_length:
                   if(data==null){
                   return 0;
                   }
                   else {
                   return strlen(data);}
break;
default:
                   return -enotty;
}
return ret;
}

void tongdev_release(struct inode *inode,struct file *filp){
mod_dec_use_count; //decrease these mod's user
printk("This chrdev is in release\n");
return 0;
#ifdef debug
printk("tongdev_release(%p,%p)\n",inode,filp);
#endif}