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Message-ID: <20231116-sandblast-groggy-c35eb536c34d@squawk>
Date: Thu, 16 Nov 2023 21:27:03 +0000
From: Conor Dooley <conor@...nel.org>
To: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Cc: Rob Herring <robh+dt@...nel.org>,
Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
Conor Dooley <conor+dt@...nel.org>, devicetree@...r.kernel.org,
linux-kernel@...r.kernel.org,
AngeloGioacchino Del Regno
<angelogioacchino.delregno@...labora.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>,
Matthias Brugger <matthias.bgg@...il.com>,
Michal Simek <michal.simek@....com>,
Neil Armstrong <neil.armstrong@...aro.org>,
Nishanth Menon <nm@...com>, Olof Johansson <olof@...om.net>
Subject: Re: [PATCH] docs: dt-bindings: add DTS Coding Style document
On Thu, Nov 16, 2023 at 07:12:18PM +0100, Krzysztof Kozlowski wrote:
> Document preferred coding style for Devicetree sources (DTS and DTSI),
> to bring consistency among all (sub)architectures and ease in reviews.
This is a good idea IMO, thanks for writing it.
Should we also mention in this about the expected breakdown of things
between $soc.dtsi and $soc-$board.dtsi? There's commonly confusion about
things like oscillators and where they belong - particularly when the
SoC mandates that these oscillators be of a single frequency.
It may seem obvious to us what goes where, but certainly contributors
frequently get this wrong.
Cheers,
Conor.
>
> Cc: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
> Cc: Arnd Bergmann <arnd@...db.de>
> Cc: Bjorn Andersson <andersson@...nel.org>
> Cc: Geert Uytterhoeven <geert+renesas@...der.be>
> Cc: Heiko Stuebner <heiko@...ech.de>
> Cc: Konrad Dybcio <konrad.dybcio@...aro.org>
> Cc: Matthias Brugger <matthias.bgg@...il.com>
> Cc: Michal Simek <michal.simek@....com>
> Cc: Neil Armstrong <neil.armstrong@...aro.org>
> Cc: Nishanth Menon <nm@...com>
> Cc: Olof Johansson <olof@...om.net>
> Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
>
> ---
>
> Merging idea: Rob/DT bindings
> ---
> Documentation/devicetree/bindings/index.rst | 1 +
> .../devicetree/bindings/writing-dts.rst | 137 ++++++++++++++++++
> 2 files changed, 138 insertions(+)
> create mode 100644 Documentation/devicetree/bindings/writing-dts.rst
>
> diff --git a/Documentation/devicetree/bindings/index.rst b/Documentation/devicetree/bindings/index.rst
> index d9002a3a0abb..975449be4862 100644
> --- a/Documentation/devicetree/bindings/index.rst
> +++ b/Documentation/devicetree/bindings/index.rst
> @@ -5,5 +5,6 @@
>
> ABI
> writing-bindings
> + writing-dts
> writing-schema
> submitting-patches
> diff --git a/Documentation/devicetree/bindings/writing-dts.rst b/Documentation/devicetree/bindings/writing-dts.rst
> new file mode 100644
> index 000000000000..10c477ec1eed
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/writing-dts.rst
> @@ -0,0 +1,137 @@
> +.. SPDX-License-Identifier: GPL-2.0
> +.. _writingdts:
> +
> +===================================================
> +Writing Devicetree Sources (DTS) - DTS Coding Style
> +===================================================
> +
> +When writing Devicetree Sources (DTS) please observe below guidelines. They
> +should be considered complementary to any rules expressed already in Devicetree
> +Specification and dtc compiler (including W=1 and W=2 builds).
> +
> +Individual architectures and sub-architectures can add additional rules, making
> +the style stricter.
> +
> +Naming and Valid Characters
> +---------------------------
> +
> +1. Node and property names are allowed to use only:
> +
> + * lowercase characters:: [a-z]
> + * digits:: [0-9]
> + * dash:: -
> +
> +2. Labels are allowed to use only:
> +
> + * lowercase characters:: [a-z]
> + * digits:: [0-9]
> + * underscore:: _
> +
> +3. Unit addresses should use lowercase hex, without leading zeros (padding).
> +
> +4. Hex values in properties, e.g. "reg", should use lowercase hex. Any address
> + part can be padded with leading zeros.
> +
> +Example::
> +
> + gpi_dma2: dma-controller@...000 {
> + compatible = "qcom,sm8550-gpi-dma", "qcom,sm6350-gpi-dma";
> + reg = <0x0 0x00800000 0x0 0x60000>;
> + }
> +
> +Order of Nodes
> +--------------
> +
> +1. Nodes within any bus, thus using unit addresses for children, shall be
> + ordered incrementally by unit address.
> +
> +2. Nodes without unit addresses should be ordered alpha-numerically.
> +
> +3. When extending nodes in board DTS via &label, the entries should be ordered
> + alpha-numerically.
> +
> +Example::
> +
> + // SoC DTSI
> +
> + \ {
> + cpus {
> + // ...
> + };
> +
> + psci {
> + // ...
> + };
> +
> + soc@ {
> + dma: dma-controller@...00 {
> + // ...
> + };
> +
> + clk: clock-controller@...00 {
> + // ...
> + };
> + };
> + };
> +
> + // Board DTS
> +
> + &clk {
> + // ...
> + };
> +
> + &dma {
> + // ...
> + };
> +
> +
> +Order of Properties in Device Node
> +----------------------------------
> +
> +Following order of properties in device nodes is preferred:
> +
> +1. compatible
> +2. reg
> +3. ranges
> +4. All properties with values
> +5. Boolean properties
> +6. status (if applicable)
> +7. Child nodes
> +
> +The "status" property is by default "okay", thus it can be omitted.
> +
> +Example::
> +
> + // SoC DTSI
> +
> + usb_1_hsphy: phy@...3000 {
> + compatible = "qcom,sm8550-snps-eusb2-phy";
> + reg = <0x0 0x088e3000 0x0 0x154>;
> + #phy-cells = <0>;
> + resets = <&gcc GCC_QUSB2PHY_PRIM_BCR>;
> + status = "disabled";
> + };
> +
> + // Board DTS
> +
> + &usb_1_hsphy {
> + clocks = <&tcsr TCSR_USB2_CLKREF_EN>;
> + clock-names = "ref";
> + status = "okay";
> + };
> +
> +
> +Indentation
> +-----------
> +
> +1. Use indentation according to :ref:`codingstyle`.
> +2. For arrays spanning across lines, preferred is to align the continued
> + entries with opening < from first line.
> +
> +Example::
> +
> + thermal-sensor@...1000 {
> + compatible = "qcom,sm8550-tsens", "qcom,tsens-v2";
> + reg = <0x0 0x0c271000 0x0 0x1000>,
> + <0x0 0x0c222000 0x0 0x1000>;
> + };
> --
> 2.34.1
>
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