On 25/11/2023 20:37, Laurent Pinchart wrote: > Hi Krzysztof, > > Thank you for the patch. > > On Sat, Nov 25, 2023 at 07:44:22PM +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. >> >> Cc: Andrew Davis <a...@ti.com> >> cc: Andrew Lunn <and...@lunn.ch> >> Cc: AngeloGioacchino Del Regno <angelogioacchino.delre...@collabora.com> >> Cc: Arnd Bergmann <a...@arndb.de> >> Cc: Bjorn Andersson <anders...@kernel.org> >> Cc: Chen-Yu Tsai <w...@kernel.org> >> Cc: Dmitry Baryshkov <dmitry.barysh...@linaro.org> >> Cc: Geert Uytterhoeven <geert+rene...@glider.be> >> Cc: Heiko Stuebner <he...@sntech.de> >> Cc: Jonathan Corbet <cor...@lwn.net> >> Cc: Konrad Dybcio <konrad.dyb...@linaro.org> >> Cc: Matthias Brugger <matthias....@gmail.com> >> Cc: Michal Simek <michal.si...@amd.com> >> Cc: Neil Armstrong <neil.armstr...@linaro.org> >> Cc: Nishanth Menon <n...@ti.com> >> Cc: Olof Johansson <o...@lixom.net> >> Cc: Rafał Miłecki <zaj...@gmail.com> >> Acked-by: Neil Armstrong <neil.armstr...@linaro.org> >> Acked-by: Heiko Stuebner <he...@sntech.de> >> Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlow...@linaro.org> >> >> --- >> >> Merging idea: Rob/DT bindings >> >> Changes in v3 >> ============= >> 1. should->shall (Angelo) >> 2. Comments // -> /* (Angelo, Michal) >> 3. Use imaginary example in "Order of Properties in Device Node" >> (Angelo) >> 4. Added paragraphs for three sections with justifications of chosen >> style. >> 5. Allow two style of ordering overrides in board DTS: alphabetically or >> by order of DTSI (Rob). >> 6. I did not incorporate feedback about, due to lack of consensus and my >> disagreement: >> a. SoM being DTS without DTSI in "Organizing DTSI and DTS" >> >> 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-rockc...@lists.infradead.org >> Cc: linux-media...@lists.infradead.org >> Cc: linux-samsung-...@vger.kernel.org >> Cc: linux-amlo...@lists.infradead.org >> Cc: linux-arm-ker...@lists.infradead.org >> Cc: linux-arm-...@vger.kernel.org >> Cc: workfl...@vger.kernel.org >> Cc: linux-doc@vger.kernel.org >> --- >> .../devicetree/bindings/dts-coding-style.rst | 194 ++++++++++++++++++ >> Documentation/devicetree/bindings/index.rst | 1 + >> 2 files changed, 195 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..e374bec0f555 >> --- /dev/null >> +++ b/Documentation/devicetree/bindings/dts-coding-style.rst >> @@ -0,0 +1,194 @@ >> +.. 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 >> +--------------------------- >> + >> +Devicetree specification allows broader range of characters in node and > > s/Devicetree specification/The Devicetree specification/ > s/broader range/a broad range/
Ack, but I really expect people finish with grammar and style fixes at v3. Please point the language things now or just let it go. > >> +property names, but for code readability the choice shall be narrowed. >> + >> +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 shall use lowercase hex, without leading zeros (padding). > > I'm curious, what's the reason for this ? I think it makes the sources > less readable. If the rule is "just" because that's how DT sources are > written today and it would be too complicated to change that, that's > fine with me. Warning (unit_address_format): /cpus/cpu@0100: unit name should not have leading 0s And we fixed all or most of DTS some time ago. > >> + >> +4. Hex values in properties, e.g. "reg", shall 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 shall 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 shall be >> + ordered either alpha-numerically or by keeping the order from DTSI >> (choice >> + depending on sub-architecture). >> + >> +Above ordering rules are easy to enforce during review, reduce chances of >> +conflicts for simultaneous additions (new nodes) to a file and help in >> +navigating through the DTS source. >> + >> +Example:: >> + >> + /* SoC DTSI */ >> + >> + / { >> + cpus { >> + /* ... */ >> + }; >> + >> + psci { >> + /* ... */ >> + }; >> + >> + soc@ { >> + dma: dma-controller@10000 { >> + /* ... */ >> + }; >> + >> + clk: clock-controller@80000 { >> + /* ... */ >> + }; >> + }; >> + }; >> + >> + /* Board DTS - alphabetical order */ >> + >> + &clk { >> + /* ... */ >> + }; >> + >> + &dma { >> + /* ... */ >> + }; >> + >> + /* Board DTS - alternative order, keep as DTSI */ >> + >> + &dma { >> + /* ... */ >> + }; >> + >> + &clk { >> + /* ... */ >> + }; >> + >> +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. >> + >> +Above order follows approach: >> + >> +1. Most important properties start the node: compatible then bus addressing >> to >> + match unit address. >> +2. Each node will have common properties in similar place. >> +3. Status is the last information to annotate that device node is or is not >> + finished (board resources are needed). >> + >> +Example:: >> + >> + /* SoC DTSI */ >> + >> + device_node: device-class@6789abc { >> + compatible = "vendor,device"; >> + reg = <0x0 0x06789abc 0x0 0xa123>; >> + ranges = <0x0 0x0 0x06789abc 0x1000>; >> + #dma-cells = <1>; >> + clocks = <&clock_controller 0>, <&clock_controller 1>; >> + clock-names = "bus", "host"; >> + vendor,custom-property = <2>; >> + status = "disabled"; >> + >> + child_node: child-class@100 { >> + reg = <0x100 0x200>; >> + /* ... */ >> + }; >> + }; >> + >> + /* Board DTS */ >> + >> + &device_node { >> + vdd-supply = <&board_vreg1>; >> + 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) >> + shall 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 shall 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 shall 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. > > I'm looking forward to discussing how to organize overlays. That > discussion should be separate though, or this patch will never get > merged :-) > > Reviewed-by: Laurent Pinchart <laurent.pinch...@ideasonboard.com> Thanks Best regards, Krzysztof