write.c

static ssize_t rwbuf_write(struct file *filep, const char *buf, size_t count, loff_t *ppos)
{
	if(count<=1024)
	{
		writenum++;
		//printk(KERN_ALERT "write1\n");
		copy_from_user(rwbuf,buf,count);
		//printk(KERN_ALERT "write2\n");
		rwlen = count;
		//printk(KERN_ALERT "write ok\n");
		return rwlen;
	}
	else
	{
		writenum++;
		copy_from_user(rwbuf,buf,1024);
		rwlen = 1024;
		printk(KERN_ALERT "write overflow\n");
		return rwlen;
	}
}