linux-kernel - Re: [RFC PATCH 0/5] Apple Macs machine-level ASoC driver

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Message-Id: <3CD969AD-7316-4D83-AD92-CC85ED817125@cutebit.org>
Date:   Fri, 22 Apr 2022 14:53:54 +0200
From:   Martin Povišer <povik@...ebit.org>
To:     Mark Brown <broonie@...nel.org>
Cc:     Martin Povišer <povik+lin@...ebit.org>,
        Liam Girdwood <lgirdwood@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Jaroslav Kysela <perex@...ex.cz>,
        Takashi Iwai <tiwai@...e.com>, alsa-devel@...a-project.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        Mark Kettenis <kettenis@...nbsd.org>,
        Hector Martin <marcan@...can.st>,
        Sven Peter <sven@...npeter.dev>
Subject: Re: [RFC PATCH 0/5] Apple Macs machine-level ASoC driver



> On 22. 4. 2022, at 14:44, Mark Brown <broonie@...nel.org> wrote:
> 
> On Fri, Apr 22, 2022 at 02:36:03PM +0200, Martin Povišer wrote:
> 
>>> Ah, I think the confusion here is that I'm using slot and channel
>>> interchangably whereas you're saying that previously the driver would
>>> allocate two channels to each speaker with duplicate data?
> 
>> I guess you could say that. Not that there’s duplicate data on the I2S
>> bus, but the speaker amp would previously be configured to look for the
>> left and right channel in the same TDM slot (see e.g. set_tdm_slot of
>> tas2770 [0]).  (Each speaker amp drives a single speaker, but it still
>> has a notion of left and right channel.)
> 
> Oh, I see - the speaker actually allows configuration of the slots
> independently.  Usually the left/right thing on mono devices only does
> something for I2S where the bus clocking enforces that there be both
> left and right channels.  Either configuration is fine by me TBH, if you
> can do that then you could just keep them mapped to the same channel
> then mark the control as disabled since it should have no effect.

Well but is there some established way to mark a control as disabled?

Another issue here is that if I disable it I can’t leave the routing
control in it’s default value, which is ‘I2C Offset’ and makes the speaker
amp ignore the slot mapping.