Subject: Re: [PATCH] i2c: xiic: Support disabling multi-master in DT

From: Wolfram Sang <[email-masked]>
Date: Thu, 2 Apr 2020 11:28:13 +0200

Hi Jaako,

> > My best bet is to introduce another binding "single-master" which says
> > clearly that we are the only bus master on that bus.
> >
> > Both bindings missing means then "unclear".
> >
> > I think this matches reality best.
> >
> > Opinions?

> I agree that this sounds like the best option if original binding
> can't be used, even though it can also be a bit confusing to have 2
> similar bindings.

I think it becomes understandable if we emphasize that "no bindings"
means "unclear". We need to document it.

> How would both bindings existing simultaneously be interpreted? Maybe
> both existing simultaneously should be considered as an invalid
> configuration, so that it would be enough to just check the one you
> need? The other option would be to treat both existing similarly to
> neither existing, which would require the driver to always check both
> if checking one.

I am clearly for saying that this is an illegal combination. I'd hope
this can be expressed in a YAML binding. Yet, my research didn't give me
an answer. Adding Rob and DT list to CC. Question is:

Can we check if the boolean bindings "multi-master" and "single-master"
are not applied at the same time? Any other combination is okay, i.e.
just one of them or none of them.

> Should the new single-master binding also be a general binding for all
> I2C drivers or a binding just defined for the XIIC driver? Having it

It should definately be global.

Thanks,

   Wolfram

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