linux-kernel - Re: [PATCH 4/4] regmap: sdw: add support for SoundWire 1.2 MBQ

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Message-ID: <20200826101637.GC4965@sirena.org.uk>
Date:   Wed, 26 Aug 2020 11:16:37 +0100
From:   Mark Brown <broonie@...nel.org>
To:     Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
Cc:     alsa-devel@...a-project.org, linux-kernel@...r.kernel.org,
        tiwai@...e.de, vkoul@...nel.org, gregkh@...uxfoundation.org,
        jank@...ence.com, srinivas.kandagatla@...aro.org,
        slawomir.blauciak@...el.com,
        Bard liao <yung-chuan.liao@...ux.intel.com>,
        Rander Wang <rander.wang@...ux.intel.com>,
        Ranjani Sridharan <ranjani.sridharan@...ux.intel.com>,
        Hui Wang <hui.wang@...onical.com>,
        Guennadi Liakhovetski <guennadi.liakhovetski@...ux.intel.com>,
        Kai Vehmanen <kai.vehmanen@...ux.intel.com>,
        "Rafael J. Wysocki" <rafael@...nel.org>
Subject: Re: [PATCH 4/4] regmap: sdw: add support for SoundWire 1.2 MBQ

On Tue, Aug 25, 2020 at 12:16:56PM -0500, Pierre-Louis Bossart wrote:

> One possible objection is that this code could have been handled with
> regmap-sdw.c. However this is a new spec addition not handled by every
> SoundWire 1.1 and non-SDCA device, so there's no reason to load code
> that will never be used.

> Also in practice it's extremely unlikely that CONFIG_REGMAP would not
> be selected with CONFIG_REGMAP_MBQ selected. However there's no
> functional dependency between the two modules so they can be selected
> separately.

The other thing I'm wondering here is about compatibility - is this
something we can enumerate at runtime and if so couldn't this be done
more like how we handle the various I2C and SMBus variants so the driver
just says it wants a SoundWire regmap and then based on the capabilities
of the device and the controller the regmap decides if it can use MBQ or
not on the current system?

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