On Fri, Oct 28, 2022 at 07:37:01PM -0400, Krzysztof Kozlowski wrote: > It is useful to start from existing bindings when writing new ones, > especially when one does not know that much DT schema. However we have > several bindings which are not the best examples, so people tend to copy > their issues into new bindings. > > Beginners also might not know how to achieve some more complex solutions > in DT schema, e.g. how one of two properties should be required by the > bindings. Some of such solutions are already in example-schema.yaml, > but several other are missing. Add reference with such re-usable > design-patterns. My main concern here is what's a good example today is not tomorrow... > Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@xxxxxxxxxx> > --- > .../devicetree/bindings/examples.rst | 63 +++++++++++++++++++ > Documentation/devicetree/bindings/index.rst | 1 + > 2 files changed, 64 insertions(+) > create mode 100644 Documentation/devicetree/bindings/examples.rst > > diff --git a/Documentation/devicetree/bindings/examples.rst b/Documentation/devicetree/bindings/examples.rst > new file mode 100644 > index 000000000000..710eea81d8b7 > --- /dev/null > +++ b/Documentation/devicetree/bindings/examples.rst > @@ -0,0 +1,63 @@ > +.. SPDX-License-Identifier: GPL-2.0 > + > +Examples of Devicetree Bindings to use a base > +============================================= > + > +Following Devicetree Bindings in DT Schema are a known good starting point when > +writing new bindings: > + > +1. Simple SPI device: > + Documentation/devicetree/bindings/iio/adc/maxim,max11205.yaml > + > +2. PMIC (MFD) with several sub-devices: > + Documentation/devicetree/bindings/mfd/mediatek,mt6370.yaml > + > +3. Battery charger (power supply): > + Documentation/devicetree/bindings/power/supply/bq256xx.yaml > + (but use vendor prefix in filename) > + > +4. Clock controller for several devices with different clock inputs: > + Documentation/devicetree/bindings/clock/qcom,mmcc.yaml > + > +5. GPIO controller: > + Documentation/devicetree/bindings/gpio/qcom,wcd934x-gpio.yaml > + > + > +Re-usable design patterns when writing your own bindings > +======================================================== > + > +Following bindings show how to use common pattern of writing bindings: > + > +1. Property required and present only for one variant. Property cannot appear > + on other variants: > + Documentation/devicetree/bindings/example-schema.yaml > + Line: 212 > + > +2. Excluding properties, but none are required: > + Documentation/devicetree/bindings/mfd/samsung,s5m8767.yaml > + Line: 155 > + > +3. Excluding required properties, but one is required: > + Documentation/devicetree/bindings/reserved-memory/reserved-memory.yaml > + Line: 91 > + > +4. Array with numbers (items) from given range - min/max: > + Documentation/devicetree/bindings/arm/l2c2x0.yaml > + Line: 74 > + > +5. Array with numbers (items) from given range - enum: > + Documentation/devicetree/bindings/display/msm/dsi-controller-main.yaml > + Line: 101 > + > +6. Uint32 matrix, variable length of two-items: > + Documentation/devicetree/bindings/iio/adc/st,stm32-adc.yaml > + Line: 278 > + > +7. Phandle to syscon with offset: > + Documentation/devicetree/bindings/soc/samsung/exynos-usi.yaml > + Line: 42 > + > +8. Variable length of array (e.g. clocks and clock-names) but narrowed to > + specific variant: > + Documentation/devicetree/bindings/clock/qcom,mmcc.yaml > + Lines: 33 and 71 It seems like some of these that are just a single property we could add to example-schema.yaml. Also, perhaps a reference to this from writing-schema.rst. Rob
