this is what i got so far for the gameboy emulator, besides the things that are already implemented in radare2 apis and sdl2. The idea is to inject io-plugins into RIO, that mimic the behaviour of gameboy memory mapped hardware registers, and then map these into the virtual address space implemented in RIO, so that i don't need to do any tedious boundary checks and can take full advantage of RIOBank api to perform bankswitching and locking of certain memory regions for ppu emulation.