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/*清除空间*/
memset(mem_devp,0,sizeof(struct mem_dev));
for(i = 0; i < MEMDEV_NR_DEVS; ++i)
{
mem_devp[i].size = MEMDEV_SIZE;
mem_devp[i].data = kmalloc(MEMDEV_SIZE,GFP_KERNEL);
/*问题，没有进行错误的控制*/
memset(mem_devp[i].data,0,MEMDEV_SIZE);
}
return 0;
fail_malloc:
unregister_chrdev_region(devno,1);
return result;
}
/*模块清除函数*/
static void memdev_exit(void)
{
cdev_del(&cdev);/*注销字符设备*/
/*释放两个物理内存*/
kfree(mem_devp[0].data);
kfree(mem_devp[1].data);
kfree(mem_devp);/*释放设备结构体内存*/
unregister_chrdev_region(MKDEV(mem_major,0),2);
}
/*定义相关的操作函数*/
/*mem_open*/
int mem_open(struct inode *inode,struct file *filp)
{
struct mem_dev *dev;
/*判断设备文件的次设备号*/
int num = MINOR(inode->i_rdev);
if(num >= MEMDEV_NR_DEVS)
return -ENODEV;
dev = &mem_devp[num];
/*将数据指向两个内存空间*/
filp->private_data = dev;
return 0;
}
/*release函数的实现*/
int mem_release(struct inode *inode, struct file *flip)
{
return 0;
}
/*read函数的实现*/
static ssize_t mem_read(struct file *filp,char __user *buf, size_t size,loff_t *ppos)
{
unsigned long p = *ppos;
unsigned int count = size;
int ret = 0;
/*获得file结构体上的指针*/
struct mem_dev *dev = filp->private_data;
/*参数的检查*/
if(p >= MEMDEV_SIZE)
return 0;
if(count > MEMDEV_SIZE - p)
count = MEMDEV_SIZE - p;
/*从内核读数据到用户空间*/
if(copy_to_user(buf,(void *)(dev->data + p),count))
{
/*出错误*/
ret = -EFAULT;
}
else
{
/*移动当前文件光标的位置*/
*ppos += count;
ret = count;
printk(KERN_INFO "read %d bytes(s) from %d",count,p);
}
return ret;
}
/*write函数的实现*/
static ssize_t mem_write(struct file *filp,const char __user *buf,size_t size,loff_t *ppos)
{
unsigned long p = *ppos;
unsigned int count = size;
int ret = 0;
/*获得设备结构体的指针*/
struct mem_dev *dev = filp->private_data;
/*检查参数的长度*/
if(p >= MEMDEV_SIZE)
return 0;
if(count > MEMDEV_SIZE - p)
count = MEMDEV_SIZE - p;
if(copy_from_user(dev->data + p,buf,count))
ret = -EFAULT;
else
{
/*改变文件位置*/
*ppos += count;
ret = count;
printk(KERN_INFO "writted %d bytes(s) from %d",count,p);
}
return ret;
}
/*lseek的实现*/
static loff_t mem_llseek(struct file *filp,loff_t offset, int whence)
{
loff_t newpos;
switch(whence)
{
case 0:/*SEEK_SET*/
newpos = offset;
break;
case 1:/*SEEK_CUR*/
newpos = filp->f_pos + offset;
break;
case 2:/*SEEK_END*/
newpos = MEMDEV_SIZE - 1 + offset;
break;
default:
return -EINVAL;
}
filp->f_pos = newpos;
return newpos;
}
/*作者以及权限的声明*/
MODULE_AUTHOR("GongPing");
MODULE_LICENSE("GPL");
/*通过宏module_init和module_exit实现模块添加*/
module_init(memdev_init);
module_exit(memdev_exit);
第三个是Makefile：
ifneq ($(KERNELRELEASE),)
obj-m := memdev.o
else
#KDIR :=/usr/src/kernels/2.6.35.14-96.fc14.i686
#KDIR :=/lib/modules/2.6.35.14-96.fc14.i686/build
#KDIR ?=/opt/LinuxKernel/linux-2.6.38.1
KDIR :=/opt/LinuxKernel/linux-2.6.38.1
PWD :=$(shell pwd)
default:
make -C $(KDIR) M=$(PWD) modules
clean:
rm -f *.ko *.o *.mod.o *.mod.c *.symvers
endif
第4个是应用程序：
#include
#include
#include
int main()
{
FILE *fp0 = NULL;
char Buf[4096];
/*复制数据到buf中*/
strcpy(Buf,"Mem is char devices!");
printf("Buf: %s",Buf);
/*打开设备文件*/
fp0 = fopen("/dev/memdev0","rw");
/*错误处理*/
if(fp0 == NULL)
{
printf("Open Memdev0 Error!");
return -1;
}
/*写数据到设备中*/
//fread(Buf,sizeof(Buf),1,fp0);
fwrite(Buf,sizeof(Buf),1,fp0);
/*定位*/
fseek(fp0,0,SEEK_SET);
/*复制数据到Buf*/
strcpy(Buf,"Buf is NULL!");
/*打印*/
printf("Buf: %s",Buf);
/*读数据*/
fread(Buf,sizeof(Buf),1,fp0);
printf("BUF: %s",Buf);
fclose(fp0);
return 0;
}
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