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

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Date:   Thu, 10 Nov 2016 14:34:07 +0000
From:   Sudeep Holla <sudeep.holla@....com>
To:     Rob Herring <robh@...nel.org>
Cc:     Sudeep Holla <sudeep.holla@....com>,
        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 10/11/16 14:12, Rob Herring wrote:
> 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.
>

OK, but IIUC Olof's concern wanted a generic one along with the platform
specific compatible which kind of makes sense as so far we have seen
some commonality between Amlogic and Rockchip.

E.g. Amlogic follows most of the legacy protocol though it deviates in
couple of things which we can handle with platform specific compatible
(in the following patch in the series). When another user(Rockchip ?)
make use of this legacy protocol, we can start using those platform
specific compatible for deviations only.

Is that not acceptable ?

-- 
Regards,
Sudeep