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([178.197.222.11]) by smtp.gmail.com with ESMTPSA id m7-20020a05600c4f4700b0040772138bb7sm17248340wmq.2.2023.11.20.00.40.50 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 20 Nov 2023 00:40:51 -0800 (PST) From: Krzysztof Kozlowski To: Rob Herring , Krzysztof Kozlowski , Conor Dooley , Matthias Brugger , AngeloGioacchino Del Regno , devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-mediatek@lists.infradead.org Cc: Krzysztof Kozlowski , Andrew Davis , Arnd Bergmann , Bjorn Andersson , Geert Uytterhoeven , Heiko Stuebner , Konrad Dybcio , Michal Simek , Neil Armstrong , Nishanth Menon , Olof Johansson , linux-rockchip@lists.infradead.org, linux-samsung-soc@vger.kernel.org, linux-amlogic@lists.infradead.org, linux-arm-msm@vger.kernel.org Subject: [PATCH v2] docs: dt-bindings: add DTS Coding Style document Date: Mon, 20 Nov 2023 09:40:44 +0100 Message-Id: <20231120084044.23838-1-krzysztof.kozlowski@linaro.org> X-Mailer: git-send-email 2.34.1 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-samsung-soc@vger.kernel.org Document preferred coding style for Devicetree sources (DTS and DTSI), to bring consistency among all (sub)architectures and ease in reviews. Cc: Andrew Davis Cc: AngeloGioacchino Del Regno Cc: Arnd Bergmann Cc: Bjorn Andersson Cc: Geert Uytterhoeven Cc: Heiko Stuebner Cc: Konrad Dybcio Cc: Matthias Brugger Cc: Michal Simek Cc: Neil Armstrong Cc: Nishanth Menon Cc: Olof Johansson Signed-off-by: Krzysztof Kozlowski Acked-by: Neil Armstrong Acked-by: Heiko Stuebner --- Merging idea: Rob/DT bindings Changes in v2 ============= 1. Hopefully incorporate entire feedback from comments: a. Fix \ { => / { (Rob) b. Name: dts-coding-style (Rob) c. Exceptions for ordering nodes by name for Renesas and pinctrl (Geert, Konrad) d. Ordering properties by common/vendor (Rob) e. Array entries in <> (Rob) 2. New chapter: Organizing DTSI and DTS 3. Several grammar fixes (missing articles) Cc: linux-rockchip@lists.infradead.org Cc: linux-mediatek@lists.infradead.org Cc: linux-samsung-soc@vger.kernel.org Cc: linux-amlogic@lists.infradead.org Cc: linux-arm-kernel@lists.infradead.org Cc: linux-arm-msm@vger.kernel.org --- .../devicetree/bindings/dts-coding-style.rst | 163 ++++++++++++++++++ Documentation/devicetree/bindings/index.rst | 1 + 2 files changed, 164 insertions(+) create mode 100644 Documentation/devicetree/bindings/dts-coding-style.rst diff --git a/Documentation/devicetree/bindings/dts-coding-style.rst b/Documentation/devicetree/bindings/dts-coding-style.rst new file mode 100644 index 000000000000..cc7e3b4d1b92 --- /dev/null +++ b/Documentation/devicetree/bindings/dts-coding-style.rst @@ -0,0 +1,163 @@ +.. SPDX-License-Identifier: GPL-2.0 +.. _dtscodingstyle: + +===================================== +Devicetree Sources (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. The address + part can be padded with leading zeros. + +Example:: + + gpi_dma2: dma-controller@800000 { + 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. + Alternatively for some sub-architectures, nodes of the same type can be + grouped together (e.g. all I2C controllers one after another even if this + breaks unit address ordering). + +2. Nodes without unit addresses should be ordered alpha-numerically by the node + name. For a few types of nodes, they can be ordered by the main property + (e.g. pin configuration states ordered by value of "pins" property). + +3. When extending nodes in the board DTS via &label, the entries should be + ordered alpha-numerically. + +Example:: + + // SoC DTSI + + / { + cpus { + // ... + }; + + psci { + // ... + }; + + soc@ { + dma: dma-controller@10000 { + // ... + }; + + clk: clock-controller@80000 { + // ... + }; + }; + }; + + // 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. Standard/common properties (defined by common bindings, e.g. without + vendor-prefixes) +5. Vendor-specific properties +6. status (if applicable) +7. Child nodes, where each node is preceded with a blank line + +The "status" property is by default "okay", thus it can be omitted. + +Example:: + + // SoC DTSI + + usb_1_hsphy: phy@88e3000 { + 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, it is preferred to align the continued + entries with opening < from the first line. +3. Each entry in arrays with multiple cells (e.g. "reg" with two IO addresses) + should be enclosed in <>. + +Example:: + + thermal-sensor@c271000 { + compatible = "qcom,sm8550-tsens", "qcom,tsens-v2"; + reg = <0x0 0x0c271000 0x0 0x1000>, + <0x0 0x0c222000 0x0 0x1000>; + }; + +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). +3. DTS representing the board. + +Hardware components which are present on the board should be placed in the +board DTS, not in the SoC or SoM DTSI. A partial exception is a common +external reference SoC-input clock, which could be coded as a fixed-clock in +the SoC DTSI with its frequency provided by each board DTS. diff --git a/Documentation/devicetree/bindings/index.rst b/Documentation/devicetree/bindings/index.rst index d9002a3a0abb..cc1fbdc05657 100644 --- a/Documentation/devicetree/bindings/index.rst +++ b/Documentation/devicetree/bindings/index.rst @@ -4,6 +4,7 @@ :maxdepth: 1 ABI + dts-coding-style writing-bindings writing-schema submitting-patches