linux-kernel - Re: [PATCH v2] docs: dt-bindings: add DTS Coding Style document

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Message-ID: <bd49f17c-7ebf-4e19-b77b-b5ec95375f7d@amd.com>
Date:   Tue, 21 Nov 2023 08:33:15 +0100
From:   Michal Simek <michal.simek@....com>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, Andrew Davis <afd@...com>,
        Arnd Bergmann <arnd@...db.de>,
        Bjorn Andersson <andersson@...nel.org>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Heiko Stuebner <heiko@...ech.de>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Neil Armstrong <neil.armstrong@...aro.org>,
        Nishanth Menon <nm@...com>, Olof Johansson <olof@...om.net>,
        linux-rockchip@...ts.infradead.org,
        linux-samsung-soc@...r.kernel.org,
        linux-amlogic@...ts.infradead.org, linux-arm-msm@...r.kernel.org
Subject: Re: [PATCH v2] docs: dt-bindings: add DTS Coding Style document



On 11/20/23 20:31, Krzysztof Kozlowski wrote:
> On 20/11/2023 20:18, Geert Uytterhoeven wrote:
>> Hi Krzysztof,
>>
>> On Mon, Nov 20, 2023 at 3:53 PM Krzysztof Kozlowski
>> <krzysztof.kozlowski@...aro.org> wrote:
>>> On 20/11/2023 15:01, Michal Simek wrote:> >
>>>> On 11/20/23 09:40, Krzysztof Kozlowski wrote:
>>>>> Document preferred coding style for Devicetree sources (DTS and DTSI),
>>>>> to bring consistency among all (sub)architectures and ease in reviews.
>>
>>>>> +Organizing DTSI and DTS
>>>>> +-----------------------
>>>>> +
>>>>> +The DTSI and DTS files should be organized in a way representing the common
>>>>> +(and re-usable) parts of the hardware.  Typically this means organizing DTSI
>>>>> +and DTS files into several files:
>>>>> +
>>>>> +1. DTSI with contents of the entire SoC (without nodes for hardware not present
>>>>> +   on the SoC).
>>>>> +2. If applicable: DTSI with common or re-usable parts of the hardware (e.g.
>>>>> +   entire System-on-Module).
>>>>
>>>> DTS/DTSI - SOMs can actually run as they are that's why it is fair to say that
>>>> there doesn't need to be DTS representing the board.
>>>
>>> I have never seen a SoM which can run without elaborate hardware-hacking
>>> (e.g. connecting multiple wires to the SoM pins). The definition of the
>>> SoM is that it is a module. Module can be re-used, just like SoC.
>>
>> /me looks at his board farm...
>>
>> The Renesas White-Hawk CPU board can be used standalone, and has a
>> separate power input connector for this operation mode.  As it has RAM,
>> Ethernet, serial console, eMMC, and even mini-DP, it can serve useful
>> purposes on its own.
>> I agree it's not a super-good example, as the board is not really a
>> "SoM", and we currently don't have r8a779g0-white-hawk-cpu.dts, only
>> r8a779g0-white-hawk-cpu.dtsi.
>>
>> The RZ/A2M CPU Board is a real SoM, which can be powered over USB.
>> It has less standard connectors (microSD, USB, MIPI CSI-2), but still
>> sufficient features to be usable on its own.
>> Again, we're doing a bad job, as we only have a DTS for the full eval
>> board (r7s9210-rza2mevb.dts).
>>
>> I guess there are (many) other examples...
> 
> OK, I never had such in my hands. Anyway, the SoM which can run
> standalone  has a meaning of a board, so how exactly you want to
> rephrase the paragraph?

What about?

2. If applicable: DTSI with common or re-usable parts of the hardware (e.g.
entire System-on-Module). DTS if runs standalone.

Thanks,
Michal