> > do you think it makes sense then to have a similar encoded value from DT
> > (maybe "mmc-fixed-driver-type-<n>" with n=0..4)?
> 
> The _DSM, being a device-specific method does not have to support different
> devices with different requirements whereas DT does.

So, it is more like a vendor specific property (e.g. "renesas,
mmc-driver-type")? Sorry, I don't know much about ACPI.

> >                                                  This is a largely
> > reduced encoding of what you proposed in 2015 [1] but may be more
> > pragmatic for soldered on-board devices working on their max speeds with
> > fixed voltages and frequencies? Or did I get something wrong?
> 
> What I proposed was being forced on me by the requirement to provide a
> solution that could meet any conceivable need.  That gets over-complicated.

Yeah, that became pretty clear.

> But as you say, in practice people are probably only interested in providing
> one value for the max speed / frequency.

OK. Thanks for your answers! Much appreciated.