On Mon, 4 Oct 2021, Mark Brown wrote:
> > > > +static const char * const micbias_voltage[] = { "off", "2V", "2.5V",
> > > > "AVDD" };
>
> > > This should be configured in the DT, it's going to be a property of the
> > > electrical design of the system.
>
> > I can very well imagine that this something that should be runtime
> > userspace configurable. In fact where I work we have had products where
> > the bias voltage (for an externally connected microphone) could be
> > configured by the end user, (although not for this specific driver quite
> > honestly, we have had the need for hardware engineers to change it runtime
> > during circuit verification though).
>
> > Would it be ok to have this configurable both in the DT as well as using a
> > control? Or should it be implemented in another way, such as a number of
> > pre set voltages that are selected between using a control?
>
> It seems like a lot less work to just not have the runtime control and
> let someone who needs it figure out how to represent it to userspace.
> Something that's basically a backdoor for validation doesn't seem
> persuasive, validation often wants to do things we actively wish to
> prevent at runtime.
True about validation, however, I would still say that there is a usecase
for having this user settable, if for instance the microphone is an
external device and not a fixed part of the design of which the codec is a
part.
Nevertheless it's not something I have any use for at the moment so I'll
relegate the function to a DT property. I see there are at least several
other codecs which do it that way.
/Ricard
--
Ricard Wolf Wanderlof ricardw(at)axis.com
Axis Communications AB, Lund, Sweden www.axis.com
Phone +46 46 272 2016 Fax +46 46 13 61 30
