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

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Message-ID: <20190506044916.GO14916@sirena.org.uk>
Date:   Mon, 6 May 2019 13:49:16 +0900
From:   Mark Brown <broonie@...nel.org>
To:     Sowjanya Komatineni <skomatineni@...dia.com>
Cc:     "thierry.reding@...il.com" <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Timo Alho <talho@...dia.com>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "mark.rutland@....com" <mark.rutland@....com>,
        Krishna Yarlagadda <kyarlagadda@...dia.com>,
        Laxman Dewangan <ldewangan@...dia.com>,
        "linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-spi@...r.kernel.org" <linux-spi@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>
Subject: Re: [PATCH V3 3/9] spi: add SPI_LSBYTE_FIRST mode

On Sat, Apr 27, 2019 at 12:32:58AM +0000, Sowjanya Komatineni wrote:
> > On Mon, Apr 15, 2019 at 02:30:28PM -0700, Sowjanya Komatineni wrote:

> > 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.

> Current upstream platforms have no specific device requirement but
> added this feature as Tegra support it for specific requirements of
> some slaves.

Do we have any examples of such devices?  In any case I think the main
thing here would be a software implementation of the feature so that
drivers can use it sensibly - at the minute they'd have to provide code
to work without the feature anyway and it seems like a relatively small
optimization for most things.

> [Changed mail client message format word wrap limit to 74 columns]

It's not working, and it's also mangling quoted sections of the mail
too.

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