Using Modules

Modules provide a means for multiple drivers to share common functionality; for example, if a variety of types of device might be accessed on the same bus, a module might be created to provide a common interface to the bus.

Your driver can access these modules via the kernel functions get_module() and put_module(), which obtain and release references to a specified module. When you call get_module(), you obtain a structure that provides information about the module, plus pointers to the module's functions. The module is defined in a header file provided by the module's author, similar to this:

   #define MY_MODULE_NAME "generic/mymodule/v1"
   
   struct my_module_info {
      module_info module;
      int32 (*function1)();
      int32 (*function2)();
      void (*configure)(int32 parameter, int32 value);
   };

When you want to access the module's functions, you call get_module() to get a pointer to this structure from the kernel:

   struct my_module_info *minfo = NULL;
   
   /* get a pointer to the module */
   
   get_module(MY_MODULE_NAME, (module_info **) &minfo);

Once you've done this, you can call the module's functions through the structure:

   minfo->configure(0, 10);

When you're done with the module, you should call put_module() to release it. The kernel loads and unloads modules as needed, and properly calling put_module() lets the kernel do its job.

   put_module(MY_MODULE_NAME);

If you want a better understanding of how modules work, see the "Writing Modules" section.