Re: [PATCH 4/4] ASoC: cs35l35: Add multi-device synchronisation

On Tue, May 30, 2017 at 09:51:38AM +0100, Charles Keepax wrote:

These activate the individual types of synchronisation between
the two stereo amps over a proprietary single wire connection
between the two amps. The audio option synchronises the group

So we should at least have something that represents that single wire
connection in DT since it might not be there and so that the kernel can
make sure that both devices agree if they're synced or not and can
disable the sync if it's been enabled in error (if one of the devices
is off, you seemed to be saying that might cause problems).

delay between the two amps. The VPBR links the brown out on the
two amps and the OTW links the over temperature warning.

It's not clear to me when it'd make sense to disable these from a system
integration point of view.

The issue is really one of it being use-case specific whether the
amps are being used independently or in a stereo configuration.
You could have only a single amp in use in which case the sync
features are best turned off. Or one might even have use-cases
with both amps where they are being used independently but at the
same time.

It feels like if this is going to be user controllable the UI needs to
be pulled up a level to be something like an on/off switch for the sync
rather than a series of magic _EXT controls on the individual CODECs.
Even if it is magic _EXT controls having them being per device feels
wrong.