内核编程学习笔记-char devices

《The Linux Kernel Module Programming Guide》一书中第七章Talking to Device Files
(book and source can be downloaded form http://blog.chinaunix.net/article.php?articleId=51744&blogId=2108)

insmod 的时候出错：
[root@localhost 07-TalkingToDeviceFiles]# insmod chardev.o
chardev.o: unresolved symbol module_unregister_chrdev
chardev.o: unresolved symbol module_register_chrdev
chardev.o:
Hint: You are trying to load a module without a GPL compatible license
and it has unresolved symbols. The module may be trying to access
GPLONLY symbols but the problem is more likely to be a coding or
user error. Contact the module supplier for assistance, only they
can help you.

google了一下，发现没有module_register_chrdev()和module_unregister_chrdev()。
于是修改代码:
module_register_chrdev()为register_chrdev()
module_unregister_chrdev()为unregister_chrdev()


然后insmod的时候又出错
[root@localhost 07-TalkingToDeviceFiles]# insmod chardev.o
Warning: loading chardev.o will taint the kernel: no license
See for information about tainted modules
chardev.o: init_module: Device or resource busy
Hint: insmod errors can be caused by incorrect module parameters, including invalid IO or IRQ parameters.
You may find more information in syslog or the output from dmesg

dmsg内容如下：
Sorry, registering the character device failed with -16

然后 cat /proc/devices
发现major num 100已经使用，
于是修改 chardev.h
#define MAJOR_NUM 200

then ok