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Date:   Wed, 14 Jun 2023 13:30:44 -0600
From:   Rob Herring <robh@kernel.org>
To:     Linus Walleij <linus.walleij@linaro.org>
Cc:     Mark Brown <broonie@kernel.org>,
        Matthias Schiffer <matthias.schiffer@ew.tq-group.com>,
        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
Subject: Re: [PATCH 1/2] spi: dt-bindings: introduce linux,use-rt-queue flag
Message-ID: <20230614193044.GA2595668-robh@kernel.org>
References: <20230602115201.415718-1-matthias.schiffer@ew.tq-group.com>
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 <CACRpkdYhFmG-Cb-5+dt1Huktnm+tkOjSGO5ZFPjGeOXRott6Dw@mail.gmail.com>
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On Tue, Jun 06, 2023 at 04:37:08PM +0200, Linus Walleij wrote:
> On Fri, Jun 2, 2023 at 2:22 PM Mark Brown <broonie@kernel.org> wrote:
> > 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...

I don't don't know where you got that impression. I'm fine with them in 
the sense that I don't look at downstream and anything goes there.

Rob