All the AVRs that I've looked at had the same pin/port structure, with
the possible states being input/floating, input/pullup, low, and high
(with the same PORT/DDR registers). The main difference is the number of
available ports and pins. To reduce the amount of code and avoid
duplication (and thus errors) I decided to centralize this, following
the design used by the atmega2560 but while using a trick to save
tracking a few registers.
In the process, I noticed that the Pin.Get() function was incorrect on
the atmega2560 implementation. It is now fixed in the unified code.
