AOSP - How Much Work Is Involved in Creating a Module?

We have done something like 30 different modules now. Some are easy, but some are just a lot more difficult than first anticipated. Part of that interface cleanup is also working with the device manufacturers and figuring out where are areas where they need to have kind of extensibility inside the module as well. And it's very easy, especially at the C or C++ level. It just takes like one wrong include to break that layering.