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

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Message-ID: <BYAPR12MB33989D8DCEFCDE5DB76429E7C23F0@BYAPR12MB3398.namprd12.prod.outlook.com>
Date:   Sat, 27 Apr 2019 00:32:58 +0000
From:   Sowjanya Komatineni <skomatineni@...dia.com>
To:     Mark Brown <broonie@...nel.org>
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 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.

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

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

Thanks
Sowjanya