This is a crate for the Game Boy Advance Hardware Abstraction Layer. It consists of types that the memory mapped IO uses as well as the MMIO addresses that they go with.
The types can of course safely be used on any device.
The MMIO addresses can only be safely used on a GBA, and any attempt to use them elsewhere is UB. The addresses are kept in a separate module that is only compiled in when compiling for GBA (using the compilation system suggested by the gba crate), though there is also a special override flag so that the address docs can be generated for docs.rs. You should not use the override flag otherwise.