On Tue, Nov 09, 2021 at 11:49:09PM +0530, Pratyush Yadav wrote: > Many SPI controllers need to add properties to peripheral devices. This > could be the delay in clock or data lines, etc. These properties are > controller specific but need to be defined in the peripheral node > because they are per-peripheral and there can be multiple peripherals > attached to a controller. > > If these properties are not added to the peripheral binding, then the > dtbs check emits a warning. But these properties do not make much sense > in the peripheral binding because they are controller-specific and they > will just pollute every peripheral binding. So this binding is added to > collect all such properties from all such controllers. Peripheral > bindings should simply refer to this binding and they should be rid of > the warnings. > > There are some limitations with this approach. Firstly, there is no way > to specify required properties. The schema contains properties for all > controllers and there is no way to know which controller is being used. > Secondly, there is no way to restrict additional properties. Since this > schema will be used with an allOf operator, additionalProperties needs > to be true. In addition, the peripheral schema will have to set > unevaluatedProperties: false. > > Despite these limitations, this appears to be the best solution to this > problem that doesn't involve modifying existing tools or schema specs. > > Signed-off-by: Pratyush Yadav <p.yadav@xxxxxx> > > --- > > Changes in v3: > - s/slave/peripheral/g > - Drop the | on description. > - Drop the compatible property. > > Changes in v2: > - Move other subnode properties listed in spi-controller.yaml to > spi-slave-props.yaml > - Move the Cadence controller-specific properties out of > spi-slave-props.yaml. They will be added in a separate file. > - Add a reference to spi-slave-props.yaml in spi-controller.yaml. > - Update description. > > .../bindings/spi/spi-controller.yaml | 69 +-------------- > .../bindings/spi/spi-peripheral-props.yaml | 87 +++++++++++++++++++ > 2 files changed, 89 insertions(+), 67 deletions(-) > create mode 100644 Documentation/devicetree/bindings/spi/spi-peripheral-props.yaml Reviewed-by: Rob Herring <robh@xxxxxxxxxx>
