linux-kernel - Re: [PATCH V3 3/9] spi: add SPI_LSBYTE

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Date:   Fri, 19 Apr 2019 16:22:08 +0100
From:   Mark Brown <broonie@...nel.org>
To:     Sowjanya Komatineni <skomatineni@...dia.com>
Cc:     thierry.reding@...il.com, jonathanh@...dia.com, talho@...dia.com,
        robh+dt@...nel.org, mark.rutland@....com, kyarlagadda@...dia.com,
        ldewangan@...dia.com, linux-tegra@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-spi@...r.kernel.org,
        devicetree@...r.kernel.org
Subject: Re: [PATCH V3 3/9] spi: add SPI_LSBYTE_FIRST mode

On Mon, Apr 15, 2019 at 02:30:28PM -0700, Sowjanya Komatineni wrote:
> Some SPI slaves expect bytes to be in least significant first order
> and some expects most significant first oder.
> 
> This patch adds support for requesting SPI master controllers for
> least significant first order using SPI_LSBYTE_FIRST mode.

This is byte ordering as opposed to bit ordering which the core already
supports.  Do you have any examples of devices that need this or is it
just being added for completeness?  If devices are going to rely on this
we probably need emulation support in the core I guess given that this
is a pretty unusual controller feature.

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