linux-kernel - Re: [PATCH 3/9] regmap: spi: SPI_CONTROLLER_CS_PER

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Message-ID: <20210824163721.GF4393@sirena.org.uk>
Date:   Tue, 24 Aug 2021 17:37:21 +0100
From:   Mark Brown <broonie@...nel.org>
To:     Lucas Tanure <tanureal@...nsource.cirrus.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        Sanjay R Mehta <sanju.mehta@....com>,
        Nehal Bakulchandra Shah <Nehal-Bakulchandra.shah@....com>,
        linux-kernel@...r.kernel.org, linux-spi@...r.kernel.org,
        patches@...nsource.cirrus.com
Subject: Re: [PATCH 3/9] regmap: spi: SPI_CONTROLLER_CS_PER_TRANSFER affects
 max read/write

On Tue, Aug 24, 2021 at 11:40:35AM +0100, Lucas Tanure wrote:
> regmap-spi will split data and address between two transfers in the
> same message so use addr_affects_max_raw_rw to flag that the number
> bytes to read or write should be a little less (address + padding size),
> so that the SPI controller can merge the entire message into a single
> CS period

This should be handled by the SPI core, it's already relying on being
able to do multiple transfers to handle message size limits and in any
case this is a super standard thing to do so many clients would require
special code.  The core should transparently coalesce things where it
can, or error out if it can't, like it currently does when splitting
transfers up.

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