From: Rob Herring <robh@kernel.org>
To: Andreas Kemnade <andreas@kemnade.info>
Cc: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>,
ulf.hansson@linaro.org, krzysztof.kozlowski+dt@linaro.org,
shawnguo@kernel.org, s.hauer@pengutronix.de,
kernel@pengutronix.de, festevam@gmail.com, linux-imx@nxp.com,
linux-mmc@vger.kernel.org, devicetree@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] dt-bindings: mmc: fsl-imx-esdhc: allow more compatible combinations
Date: Sun, 8 Jan 2023 16:46:33 -0600 [thread overview]
Message-ID: <20230108224633.GA353691-robh@kernel.org> (raw)
In-Reply-To: <20230107165457.30f4dddf@aktux>
On Sat, Jan 07, 2023 at 04:54:57PM +0100, Andreas Kemnade wrote:
> On Sat, 7 Jan 2023 16:07:35 +0100
> Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org> wrote:
>
> > On 07/01/2023 16:01, Andreas Kemnade wrote:
> > > On Sat, 7 Jan 2023 15:09:24 +0100
> > > Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org> wrote:
> > >
> > >> On 07/01/2023 15:07, Andreas Kemnade wrote:
> > >>> On Sat, 7 Jan 2023 15:00:56 +0100
> > >>> Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org> wrote:
> > >>>
> > >>> [...]
> > >>>>>> I asked to remove half-compatible. Not to enforce.
> > >>>>>>
> > >>> so you are saying that allowing
> > >>> compatible = "A", "B"
> > >>> is not ok, if B is not fully compatible. I agree with that
> > >>> one.
> > >>
> > >> I did not say that. It's not related to this problem.
> > >>
> > > You said "I asked to remove half-compatible" that means to me
> > > remove "B" if not fully compatible with A which sounds sane to me.
> > >
> > >> Again - you cannot have device which is and is not compatible with
> > >> something else. It's not a Schroedinger's cat to be in two states,
> > >> unless you explicitly document the cases (there are exception). If this
> > >> is such exception, it requires it's own documentation.
> > >>
> > > so conclusion:
> > > If having A and B half-compatible with A:
> > >
> > > compatible = "A" only: is allowed to specifiy it the binding (status quo),
> > > but not allowed to make the actual dtsi match the binding documentation
> > > https://lore.kernel.org/linux-devicetree/72e1194e10ccb4f87aed96265114f0963e805092.camel@pengutronix.de/
> > > and
> > > https://lore.kernel.org/linux-devicetree/20210924091439.2561931-5-andreas@kemnade.info/
> > >
> > > compatible = "A", "B" in the binding definition: is not allowed ("I asked to remove
> > > half-compatible" (= removing B))
> >
> > No, half compatible is the A in such case.
> >
> I think that there is some misunderstanding in here. I try once again.
>
> Define compatible with "X" here:
> To me it means:
>
> device fully works with flags defined in:
>
> static const struct esdhc_soc_data usdhc_X_data = { ... };
>
> with usdhc_X_data referenced in
> { .compatible = "X", .data = &usdhc_X_data, },
>
>
> So if there is only "A" matching with above definition of compatibility
> compatible = "A" would sound sane to me.
>
> And scrutinizing the flags more and not just wanting to achieve error-free
> dtbs_check, I think is this in most cases where there is only "A".
>
> If there is "A" and "B" which match that compatibility definition, you
> say that only compatible = "A", "B" is allowed, but not compatible = "A".
> In that case I would have no problem with that.
>
> But if there is only "A" but no "B" matching the above definition, I would expect
> that only compatible = "A" is allowed but *not* compatible = "A", "B".
A is either compatible with B or it isn't. You can look at that from
the h/w perspective and client/OS perspective. From the h/w side, is the
h/w interface the same or only has additions which can be ignored? On
the client side, the question is whether a client that only understands
B could use A's h/w without change. Looking at the match data is a
good indicator of that for Linux. It's also possible the answer is
different for different clients, but we only need 1 client that could
benefit from compatibility.
Rob
next prev parent reply other threads:[~2023-01-08 22:47 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-01-05 21:38 [PATCH] dt-bindings: mmc: fsl-imx-esdhc: allow more compatible combinations Andreas Kemnade
2023-01-06 8:41 ` Krzysztof Kozlowski
2023-01-06 19:33 ` Andreas Kemnade
2023-01-07 13:23 ` Krzysztof Kozlowski
2023-01-07 13:43 ` Andreas Kemnade
2023-01-07 14:00 ` Krzysztof Kozlowski
2023-01-07 14:07 ` Andreas Kemnade
2023-01-07 14:09 ` Krzysztof Kozlowski
2023-01-07 15:01 ` Andreas Kemnade
2023-01-07 15:07 ` Krzysztof Kozlowski
2023-01-07 15:54 ` Andreas Kemnade
2023-01-08 14:45 ` Krzysztof Kozlowski
2023-01-08 17:20 ` Andreas Kemnade
2023-01-09 9:14 ` Krzysztof Kozlowski
2023-01-08 22:46 ` Rob Herring [this message]
2023-01-09 23:15 ` Andreas Kemnade
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