Since version 2.6.x, Linux gives the developer the opportunity to compile parts of the kernel as separated modules that can be injected into the core, to add more features at runtime. This approach gives flexibility and freedom: there is no need to reboot the system to enjoy new features and there is no need to rebuild the whole kernel if you only need to update a specific module. This approach is widely use in the PC world, by embedded devices such as routers, smart TVs, and even by our familiar UDOO board.

To code a new kernel module is no easy task and it's far from the purpose of this book: there are plenty of books on the topic and most of the skill set comes from experience. In these pages, you are going to learn about the big picture, the key points, and the possibilities.

Unfortunately, Android doesn't use this modular approach: every required feature is built in a single binary kernel file, for practical and simplicity reasons. In the last few years there has been a trend to integrate into the kernel even the logic needed for Wi-Fi functionality, that was before it was loaded from a separated module during the boot sequence.

As we saw with the FTDI example in the previous pages, the most practical way to add a new driver to our Android kernel is using menuconfig and building the feature as a core part of the kernel.

In the next chapter, we will dig deeper in this topic and add new features to our kernel that are not present in the default configuration.