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References: <20230602115201.415718-1-matthias.schiffer@ew.tq-group.com> <628b7411-7d12-4915-80c8-cabb74ac6590@sirena.org.uk>
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From:   Linus Walleij <linus.walleij@linaro.org>
Date:   Tue, 6 Jun 2023 16:37:08 +0200
Message-ID: <CACRpkdYhFmG-Cb-5+dt1Huktnm+tkOjSGO5ZFPjGeOXRott6Dw@mail.gmail.com>
Subject: Re: [PATCH 1/2] spi: dt-bindings: introduce linux,use-rt-queue flag
To:     Mark Brown <broonie@kernel.org>
Cc:     Matthias Schiffer <matthias.schiffer@ew.tq-group.com>,
        Rob Herring <robh+dt@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        Conor Dooley <conor+dt@kernel.org>, linux-spi@vger.kernel.org,
        devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        linux-kernel@vger.kernel.org, linux@ew.tq-group.com
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On Fri, Jun 2, 2023 at 2:22=E2=80=AFPM Mark Brown <broonie@kernel.org> wrot=
e:
> On Fri, Jun 02, 2023 at 01:52:00PM +0200, Matthias Schiffer wrote:

> > We have seen a number of downstream patches that allow enabling the
> > realtime feature of the SPI subsystem to reduce latency. These were
> > usually implemented for a specific SPI driver, even though the actual
> > handling of the rt flag is happening in the generic SPI controller code=
.
> >
> > Introduce a generic linux,use-rt-queue flag that can be used with any
> > controller driver. The now redundant driver-specific pl022,rt flag is
> > marked as deprecated.
>
> This is clearly OS specific tuning so out of scope for DT...

In a sense, but to be fair anything prefixed linux,* is out of scope for DT=
,
Documentation/devicetree/bindings/input/matrix-keymap.yaml being
the most obvious offender.

On the other hand I think the DT maintainers said it is basically fine
to use undocumented DT properties for this kind of thing. Having
completely undocumented DT properties might seem evil in another
sense, but I think Apple does nothing but...

Yours,
Linus Walleij