linux-kernel - Re: [PATCH 2/2] regmap: sdw: Remove 8-bit value size restriction

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Message-ID: <Y8BkiF8sfqPifYTO@sirena.org.uk>
Date:   Thu, 12 Jan 2023 19:50:32 +0000
From:   Mark Brown <broonie@...nel.org>
To:     Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
Cc:     Charles Keepax <ckeepax@...nsource.cirrus.com>, vkoul@...nel.org,
        yung-chuan.liao@...ux.intel.com, sanyog.r.kale@...el.com,
        linux-kernel@...r.kernel.org, patches@...nsource.cirrus.com
Subject: Re: [PATCH 2/2] regmap: sdw: Remove 8-bit value size restriction

On Thu, Jan 12, 2023 at 12:43:46PM -0600, Pierre-Louis Bossart wrote:
> On 1/12/23 12:14, Mark Brown wrote:

> > The regmap gather_write() operation allows the bus to take two buffers,
> > one for the register and one for the value, rather than requiring the
> > core combine everything into a single buffer (mainly useful for large
> > transfers like firmware downloads).

> Right, but that's not supported in SoundWire. sdw_nwrite() will only
> work with consecutive addresses - and the auto-increment is handled in
> software, not hardware.

No, that's exactly what this is for.  It's for the *register address*
being in a separate buffer, the data is then a sequence of consecutive
register values.

> What's suggested here is to use the first element of reg_buf, which begs
> the question how different this is from a regular write. If there was a
> discontinuity in reg_buf then this wouldn't work at all.

reg_buf contains the address of exactly one register.

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