Shouldn't be a problem to create a `const` object that contains information about the registers or file-like objects (for Linux) relevant to the specific bus. Then `init` can do some some work on those registers/file-like objects.
Some devices have configurable sercoms (<https://learn.adafruit.com/using-atsamd21-sercom-to-add-more-spi-i2c-serial-ports/overview>) which can be configured as either spi/i2c/uart at runtime. Maybe in this case a macro could be used to "configure" the sercom once (at compile time) as either spi/etc and generate the appropriate `const` object. "Configure" here meaning to instantiate a `const` object, which is either `I2C` or `SPI` etc with a reference to the sercom specific registers. Not doing any actual hardware work (obviously, it's a macro, but I wanted to clarify).
