linux-kernel - RE: [alsa-devel] [PATCH v2 1/3] ASoC: binding: add tdm-slot.txt

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Date:	Thu, 13 Feb 2014 07:32:10 +0000
From:	"Li.Xiubo@...escale.com" <Li.Xiubo@...escale.com>
To:	Mark Brown <broonie@...nel.org>,
	Lars-Peter Clausen <lars@...afoo.de>
CC:	"lgirdwood@...il.com" <lgirdwood@...il.com>,
	"alsa-devel@...a-project.org" <alsa-devel@...a-project.org>,
	"kuninori.morimoto.gx@...esas.com" <kuninori.morimoto.gx@...esas.com>,
	"tiwai@...e.de" <tiwai@...e.de>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [alsa-devel] [PATCH v2 1/3] ASoC: binding: add tdm-slot.txt

> > The current internal API for TDM is very poor, I don't think we want
> > to expose that 1 to 1 to the devicetree. Since this means we'd have
> > to support that forever. The first thing is that the semantics of
> > snd_soc_dai_set_tdm_slot() are very unclear. E.g. some drivers use a
> > zero bit for a active slot, some drivers use a 1 bit for a active
> 
> Yes, and if we do end up using masks we need to nail down what's going
> on in the DT.
>

Yes, certainly.

> > slot. The second thing is that we are not able to specify which
> > channel should be mapped to which slot. You can merely specify
> > from/to which slots the CODEC should read/write and then it is up to
> > the driver to guess which channel should go to which slot. In my
> > opinion a binding that allows to specify a explicit mapping of which
> > channel goes to which slot would be much better.
> 
> It'd certainly be good to be able to do that, though having a default
> would make life easier.
> 

@Lars, @Mark,

Yes, then will that means that we can just end up parsing masks from DT
and the masks will be generated by the driver specified
dai->driver->ops->of_xlate_tdm_slot_mask(slots, &tx_mask, &rx_mask)
callback or one default
snd_soc_of_xlate_tdm_slot_mask(slots, &tx_mask, &rx_mask), and the
'slots' is the number of the slot parsed from the DT node ?

Or other better ways ?


Thanks,

--
Best Regards,
Xiubo





> > Also those are four different settings. In my opinion they should
> > not be expressed in one property, but rather in four. E.g.
> > specifying a tx_mask for a rx only device does not make much sense.
> 
> That makes sense.
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