linux-kernel - Re: [v7 2/4] ASoC: mediatek: mt8192: refactor for I2S3 DAI link of speaker

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Message-ID: <20220330161450.xxak64el6g6lzcem@notapiano>
Date:   Wed, 30 Mar 2022 12:14:50 -0400
From:   Nícolas F. R. A. Prado 
        <nfraprado@...labora.com>
To:     Jiaxin Yu <jiaxin.yu@...iatek.com>
Cc:     Mark Brown <broonie@...nel.org>, robh+dt@...nel.org,
        tzungbi@...gle.com, angelogioacchino.delregno@...labora.com,
        aaronyu@...gle.com, matthias.bgg@...il.com, trevor.wu@...iatek.com,
        linmq006@...il.com, alsa-devel@...a-project.org,
        devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Project_Global_Chrome_Upstream_Group@...iatek.com,
        Tzung-Bi Shih <tzungbi@...nel.org>
Subject: Re: [v7 2/4] ASoC: mediatek: mt8192: refactor for I2S3 DAI link of
 speaker

On Wed, Mar 30, 2022 at 11:48:01PM +0800, Jiaxin Yu wrote:
> On Wed, 2022-03-30 at 15:24 +0100, Mark Brown wrote:
> > On Wed, Mar 30, 2022 at 10:06:24PM +0800, Jiaxin Yu wrote:
> > > On Wed, 2022-03-30 at 13:30 +0100, Mark Brown wrote:
> > > > Making a previously optional property required means that systems
> > > > that
> > > > previously worked may stop working unless they update their DT,
> > > > DTs
> > > > may
> > > > be distributed separately to the kernel and perhaps even baked
> > > > into
> > > > firmware or similar.
> > > Thank you for your detailed answer. I should keep the driver's
> > > behavior
> > > consistent with the description of dt-bindings. The "mediatek,hdmi-
> > > codec" needs to be set as the required property. Is my
> > > understanding
> > > right?
> > 
> > The binding document and code should match so if one is changed the
> > other needs to be changed too.
> > 
> > In theory we should never change a previously optional property to
> > required which would mean that the code should be updated to reflect
> > the
> > binding document, however sometimes the DT isn't actually used as a
> > stable intereface by anything for a given property or device type so
> > we
> > can get away with changing things.
> 
> "however sometimes the DT isn't actually used as a stable intereface by
> anything for a given property or device type so we can get away with
> changing things."
> 
> Sorry, I don't understand the real idea of this description. Does it
> mean that dt-bindings in this series don't need to be updated, but the
> driver?

He means that usually the DT (and dt-binding) shouldn't be changed to avoid
incompatibilities, but sometimes it's OK to change them. For example if there
are no users of the DT yet.

But in any case, like I mentioned in my latest reply [1], I don't think changing
the dt-binding is the proper solution in this case. The driver should be changed
instead.

Thanks,
Nícolas

[1] https://lore.kernel.org/all/20220330152026.6nuigsldx46lue44@notapiano