如何在内核中定义模块的依赖关系，
例子：
got module1 and module2.
怎么说内核module2 应该在module1 或module2 依赖于module1 之后加载？
注意：模块 2 没有使用模块 1 中的任何符号，但在我的用例中顺序仍然很重要。所以不要与内核中的 moddep 相关。
【问题讨论】：
标签： linux-kernel linux-device-driver
从 linux 4.4 内核（可能更早）开始，软依赖项可用于指定在请求加载模块之前或之后加载内核模块。这些软依赖可以在配置文件中设置，如 modprobe.d (5) 联机帮助页中所述，或者可以直接使用MODULE_SOFTDEP 宏在内核模块的代码中直接指定。
要通过修改module2的代码来完成在module1之后加载module2，请将这一行添加到函数之外的module2代码中：
MODULE_SOFTDEP("pre: module1")
要通过修改module1 代码来完成相同的操作，您可以使用以下行：
MODULE_SOFTDEP("post: module2")
【讨论】：
来自 depmod 的手册页：
Linux kernel modules can provide services (called "symbols") for other
modules to use (using one of the EXPORT_SYMBOL variants in the code).
If a second module uses this symbol, that second module clearly depends
on the first module. These dependencies can get quite complex.
depmod creates a list of module dependencies by reading each module
under /lib/modules/version and determining what symbols it exports and
what symbols it needs. By default, this list is written to modules.dep,
and a binary hashed version named modules.dep.bin, in the same
directory. If filenames are given on the command line, only those
modules are examined (which is rarely useful unless all modules are
listed). depmod also creates a list of symbols provided by modules in
the file named modules.symbols and its binary hashed version,
modules.symbols.bin. Finally, depmod will output a file named
modules.devname if modules supply special device names (devname) that
should be populated in /dev on boot (by a utility such as udev).
【讨论】：
为了简单的解决方案，您可以在第一个模块中添加符号并在第二个模块 init 中检查该符号。如果符号不是使用
导出的EXPORT_SYMBOL
您可以从第二个模块初始化本身返回。
详情请看标题
Linux kernel modules can provide services (called "symbols") for other
modules to use (using one of the EXPORT_SYMBOL variants in the code).
If a second module uses this symbol, that second module clearly depends
on the first module. These dependencies can get quite complex.
depmod creates a list of module dependencies by reading each module
under /lib/modules/version and determining what symbols it exports and
what symbols it needs. By default, this list is written to modules.dep,
and a binary hashed version named modules.dep.bin, in the same
directory. If filenames are given on the command line, only those
modules are examined (which is rarely useful unless all modules are
listed). depmod also creates a list of symbols provided by modules in
the file named modules.symbols and its binary hashed version,
modules.symbols.bin. Finally, depmod will output a file named
modules.devname if modules supply special device names (devname) that
should be populated in /dev on boot (by a utility such as udev).
【讨论】：