编译模块时EXPORT_SYMBOL的用法 （转）

原帖http://blog.csdn.net/aaa6695798/archive/2009/08/25/4483748.aspx

Linux symbol export method:

[1] If we want export the symbol in a module, just use the EXPORT_SYMBOL(xxxx) in the C or H file.
    And compile the module by adding the compile flag -DEXPORT_SYMTAB.
    Then we can use the xxxx in the other module.

[2] If we want export some symbol in Kernel that is not in a module such as xxxx in the /arch/ppc/fec.c.
    Firstly, define the xxxx in the fec.c;
    Secondly, make a new file which contain the "extern" define the xxxx(for example, extern int xxxx);
    Lastly, in the ppc_ksyms.c we includes the new file, and add the EXPORT_SYMBOL(xxxx).
    Then we can use the xxxx.

其中第二条指明：在编译内核的同时编译模块，若出现内核中某符号在模块中未定义的错误，则需要做以下事情（实践经验步骤）：

（1）找到该符号在内核代码中定义的文件

（2）在符号定义文件内#include 文件

（3）在符号定义文件内EXPORT_SYMBOL(XXX) 导出该符号XXX供模块代码使用;