linux-kernel - Re: [PATCH] ASoC: simple-card: Add dummy dai support simple sound card

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Message-ID: <20210302163229.GN4522@sirena.org.uk>
Date:   Tue, 2 Mar 2021 16:32:29 +0000
From:   Mark Brown <broonie@...nel.org>
To:     Shengjiu Wang <shengjiu.wang@...il.com>
Cc:     Shengjiu Wang <shengjiu.wang@....com>,
        guennadi.liakhovetski@...ux.intel.com, alsa-devel@...a-project.org,
        kai.vehmanen@...ux.intel.com, stephan@...hold.net,
        Liam Girdwood <lgirdwood@...il.com>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>,
        Takashi Iwai <tiwai@...e.com>
Subject: Re: [PATCH] ASoC: simple-card: Add dummy dai support simple sound
 card

On Fri, Feb 26, 2021 at 02:05:29PM +0800, Shengjiu Wang wrote:
> On Thu, Feb 25, 2021 at 9:17 PM Mark Brown <broonie@...nel.org> wrote:
> > On Thu, Feb 25, 2021 at 08:08:32PM +0800, Shengjiu Wang wrote:

> > > If sound card doesn't need specific codec device, just
> > > dummy codec is enough, then we can link the dummy component
> > > directly.

> > This is a big red flag - what circumstances are these?  If it's a simple
> > CODEC with no control then the general approach is to provide a driver
> > which announces the capabilities of the CODEC and can be bound to as
> > normal, the dummy component should never actively be used.

> For the DMIC, SPDIF, HDMI ARC device or other
> similar device that there is no codec connected,  then dummy codec is
> just used for registering the sound card.

There are logical CODECs there, and we already have devices set up for
those (like dmic.c for example).  All the above cases have at least
some constraints from the spec for the interface.

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