简单的字符设备驱动程序问题__struct_inode_return_int_file_

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简单的字符设备驱动程序问题

来源: 互联网发布时间：2016-04-04

本文导语: 我写了十分简单的module，只实现read的功能，测试文件可以如下： int main() { printf("Scull testn"); char buf[20]; int fd=open("/dev/scull0",O_RDWR); printf("fd is %d",fd); read(fd,buf,10); printf("the output is %cn",buf[0]); close(fd); return 0...

我写了十分简单的module，只实现read的功能，
测试文件可以如下：
int main()
{
printf("Scull testn");
char buf[20];
int fd=open("/dev/scull0",O_RDWR);
printf("fd is %d",fd);
read(fd,buf,10);
printf("the output is %cn",buf[0]);
close(fd);
return 0;
}
最后没有正确的读到内容，不解，各位高手帮帮忙
以下是代码（头文件省略了）

static char buffer[]="123456789012345678901234567890";

int scull_trim(Scull_Dev *dev)
{return 0;
}

int scull_open(struct inode *inode,struct file *filp)
{return 0;
}

void scull_release(struct inode *inode,struct file *filp)
{
//MOD_DEC_USE_COUNT;
}

Scull_Dev *scull_follow(Scull_Dev *dev, int n)
{
    return dev;
}

read_write_t scull_read (struct inode *inode, struct file *filp,
                char *buf, count_t count)
{
copy_to_user(buf,buffer,count);
    return count;
}

read_write_t scull_write (struct inode *inode, struct file *filp,const char *buf, count_t count)
{
printk("in write functionn");
    return count;
}

int scull_ioctl (struct inode *inode, struct file *filp,
                 unsigned int cmd, unsigned long arg)
{
return 0;
}

int scull_lseek (struct inode *inode, struct file *filp,
                 off_t off, int whence)
{
return 0;
}
struct file_operations scull_fops = {
    read:       scull_read,
    write:      scull_write,
    open:       scull_open,
    release:    scull_release,
};

int init_module(void)
{
    int result, i;
SET_MODULE_OWNER(&scull_fops);
    result = register_chrdev(0, "scull", &scull_fops);
    if (result