linux-kernel - Re: [PATCH v5 6/8] Documentation: bindings: add compatible specific to legacy SCPI protocol

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Message-ID: <CAL_JsqLW4JZHb0ncVUEefnKySA231EDgvCkY3xPdaJGf=uMJYg@mail.gmail.com>
Date:   Thu, 10 Nov 2016 08:12:15 -0600
From:   Rob Herring <robh@...nel.org>
To:     Sudeep Holla <sudeep.holla@....com>
Cc:     Neil Armstrong <narmstrong@...libre.com>,
        Olof Johansson <olof@...om.net>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        linux-amlogic@...ts.infradead.org
Subject: Re: [PATCH v5 6/8] Documentation: bindings: add compatible specific
 to legacy SCPI protocol

On Thu, Nov 10, 2016 at 4:26 AM, Sudeep Holla <sudeep.holla@....com> wrote:
>
>
> On 10/11/16 01:22, Rob Herring wrote:
>>
>> On Wed, Nov 02, 2016 at 10:52:09PM -0600, Sudeep Holla wrote:
>>>
>>> This patch adds specific compatible to support legacy SCPI protocol.
>>>
>>> Cc: Rob Herring <robh+dt@...nel.org>
>>> Signed-off-by: Sudeep Holla <sudeep.holla@....com>
>>> ---
>>>  Documentation/devicetree/bindings/arm/arm,scpi.txt | 4 +++-
>>>  1 file changed, 3 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/Documentation/devicetree/bindings/arm/arm,scpi.txt
>>> b/Documentation/devicetree/bindings/arm/arm,scpi.txt
>>> index d1882c4540d0..ebd03fc93135 100644
>>> --- a/Documentation/devicetree/bindings/arm/arm,scpi.txt
>>> +++ b/Documentation/devicetree/bindings/arm/arm,scpi.txt
>>> @@ -7,7 +7,9 @@ by Linux to initiate various system control and power
>>> operations.
>>>
>>>  Required properties:
>>>
>>> -- compatible : should be "arm,scpi"
>>> +- compatible : should be
>>> +       * "arm,scpi" : For implementations complying to SCPI v1.0 or
>>> above
>>> +       * "arm,legacy-scpi" : For implementations complying pre SCPI v1.0
>>
>>
>> I'd prefer that we explicitly enumerate the old versions. Are there
>> many?
>>
>
> I understand your concern, but this legacy SCPI protocol was not
> officially released. It was just WIP which vendors picked up from very
> early releases. Since they are not numbered, it's hard to have specific
> compatibles with different versions until v1.0. That's one of the reason
> to retain platform specific compatible so that we can add any quirks
> based on them if needed.
>
> I will probably add these information in the commit log so that it's
> clear why we can't do version based compatible.

This is exactly my point. By enumerate, I meant having platform
specific compatibles. Having "arm,legacy-scpi" is pointless because
who knows what version they followed and they may all be different.

Rob