Adding code to the kernel to support new hardware is relatively easy. Removing code that is no longer useful can be harder, mostly because it can be difficult to know when something is truly no longer needed. Arnd Bergman, who removed support for eight architectures from the kernel in 2018, knows well just how hard this can be. At the 2020 Linux Plumbers Conference, he led two sessions dedicated to the topic of obsolete software and hardware. With a bit of effort, he said, it should be possible to have a better idea of when something can be removed.