[PATCH 0/6] Ancillary bus implementation and SOF multi-client support

[Pierre-Louis Bossart]

>> are controlled by DT/ACPI. The same argument applies for not using MFD
>> in this scenario as it relies on individual function devices being
>> physical devices that are DT enumerated.
> 
> MFD has no reliance on devices being DT enumerated, it works on systems
> that don't have DT and in many cases it's not clear that the split you'd
> want for the way Linux describes devices is a sensible one for other
> operating systems so we don't want to put it into DT.  Forcing things to
> be DT enumerated would just create needless ABIs.

I agree the "DT enumerated" part should be removed.

To the best of my knowledge, the part of 'individual function devices 
being physical devices' is correct though. MFDs typically expose 
different functions on a single physical bus, and the functions are 
separated out by register maps. In the case where there's no physical 
bus/device and no register map it's unclear how MFDs would help?