This concludes this chapter on writing a simple misc class character device driver on the Linux OS; so, awesome, you now know the basics of writing a device driver on Linux!
The chapter began with an introduction to device basics, and importantly, the very brief essentials of the modern LDM. You then learned how to write a simple first character device driver, registering with the kernel's misc framework. Along the way, you also understood the connection between the process, the driver, and the kernel VFS. Copying data between user and kernel address spaces is essential; we saw how to do so. A more comprehensive demo misc driver (our 'secret' driver) showed you how to perform I/O – reads and writes – ferrying data between user and kernel space. A key part of this chapter is the last section, where you learned (well, made a start at least) about security and the driver; a "hack" even demonstrated a privesc attack!
As mentioned before, there's much more to this vast topic of writing drivers on Linux; indeed, whole books are devoted to it! Do check out the Further reading section for this chapter to find relevant books and online references.
In the following chapter you will learn a key task for a driver author - how exactly can you efficiently interface your device driver with user space processes; several useful approaches are covered in detail and contrasted. Do ensure you're clear on this chapter's material, work on the exercises given, review the Further reading resources and then dive into the next one.
