Often you're unaware that these things contain firmware. They're just sold as e.g. 'bluetooth controller', but internally, there's a largish processor, a chunk

Often you're unaware that these things contain firmware. They're just sold as e.g. 'bluetooth controller', but internally, there's a largish processor, a chunk of RAM and firmware in ROM mask. The firmware versioning is implicit in the chip revision. (Of course, this just moves the problem around; it's not uncommon for a chip revision to break software elsewhere in the system.)