Re: [PATCH 4/7] ASoC: soc-dai: define TDM idle behaviour modes

[Mark Brown <broonie@kernel.org>]

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On Tue, Dec 09, 2025 at 07:31:17PM +1000, James Calligeros wrote:

> Imagine for example two codecs sharing a bus. When one codec is
> transmitting, the other must ensure that it is holding its side
> to 0, or data from the transmitting codec will be corrupted. We
> can trust the "idle" codec to simply do this itself, however
> this is undefined behaviour. Some devices may leave the line
> floating, others still may pull the line high. We need a way to
> control this behaviour.

I'm finding this explanation quite confusing - you appear to be
describing the situation where two devices simultaneously drive the same
signal which would be extremely unusual and I can't see how it would
work electrically.

> Thus, we define five possible bus-keeping modes that a device can
> be in: NONE (UB/as initialised), OFF (explicitly disabled), ZERO
> (actively transmit a 0), PULLDOWN, and HIZ (floating).

What is "explicitly disabled" in ths context?  Why aren't pull up or
drive high options?

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