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From: Rob Herring <robherring2@gmail.com>
Date: Thu, 29 Jan 2015 10:44:42 -0600
Message-ID: <CAL_JsqLE+W+T5YqzdB+DkdBE+HsgySX0yJHzn1y43QDfw4GA9A@mail.gmail.com>
Subject: Re: [PATCH 02/24] Documentation: DT bindings: add more chip
 compatible strings for Tegra PCIe
To: Paul Walmsley <paul@pwsan.com>
Cc: Mark Rutland <mark.rutland@arm.com>, Alexandre Courbot <gnurou@gmail.com>,
        Pawel Moll <pawel.moll@arm.com>,
        Ian Campbell <ijc+devicetree@hellion.org.uk>,
        "linux-pci@vger.kernel.org" <linux-pci@vger.kernel.org>,
        Stephen Warren <swarren@wwwdotorg.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Rob Herring <robh+dt@kernel.org>,
        "devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
        Thierry Reding <thierry.reding@gmail.com>,
        Kumar Gala <galak@codeaurora.org>,
        "linux-tegra@vger.kernel.org" <linux-tegra@vger.kernel.org>
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On Thu, Jan 29, 2015 at 9:45 AM, Paul Walmsley <paul@pwsan.com> wrote:
> Hi Rob
>
> On Thu, 29 Jan 2015, Rob Herring wrote:
>
>> On Wed, Jan 28, 2015 at 5:49 PM, Paul Walmsley <paul@pwsan.com> wrote:
>> >
>> > Add compatible strings for the PCIe IP blocks present on several Tegra
>> > chips.  The primary objective here is to avoid checkpatch warnings,
>> > per:
>> >

[...]

>> > +  - "nvidia,tegra132-pcie" (not yet matched in the driver)
>> > +  - "nvidia,tegra210-pcie" (not yet matched in the driver)
>>
>> Whether the driver matches or not is irrelevant to the binding and may
>> change over time. Does this mean the driver matches on something else
>> or Tegra132 is not yet supported in the driver?
>
> It means that the driver currently matches on one of the first three
> strings that don't carry that annotation.
>
>> If the former, what is important is what are the valid combinations of
>> compatible properties and that is not captured here. In other words,
>> what is the fallback compatible string for each chip?
>
> The intention was to try to be helpful: to document that anyone adding a
> "nvidia,tegra132-pcie" compatible string would also need to add one of the
> other strings as a fallback.  Would you like that to be documented in a
> different way, or removed?

Then you should say something like 'must contain "nvidia,tegra20-pcie"
and one of: ...'

You can also use nvidia,<chip>-pcie if you want. checkpatch will check
for that pattern too. Then your documentation can be something like:

Must contain '"nvidia,<chip>-pcie", "nvidia,tegra20-pcie"' where
<chip> is tegra30, tegra132, ...

We don't enforce that the <chip> part is documented ATM and not likely
until we have a schema if ever.

Rob