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.