Most presentations in the software world describes a positive achievement of sorts: a feature added or a bug removed. This presentation is different. In this presentation we shall describe how we deleted over 4000 lines of code, together comprising 30% of the code base of a complex device driver, without even trying.

Last year my team started working on refactoring the Arm CryptoCell device driver for the purpose of integrating it upstream. While doing so, a pattern emerged - almost each set of changes would reduce the code line count, and yet the functionality stayed exactly the same.

This presentation explains how and why we cut 40% of the code with no functionality loss without trying.