Re: [PATCH v2 13/16] dt-bindings: i2c: tegra-bpmp: Convert to json-schema

[Thierry Reding <thierry.reding@gmail.com>]

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On Mon, Nov 29, 2021 at 07:44:32PM -0600, Rob Herring wrote:
> On Fri, Nov 19, 2021 at 03:38:36PM +0100, Thierry Reding wrote:
> > From: Thierry Reding <treding@nvidia.com>
> > 
> > Convert the NVIDIA Tegra186 (and later) BPMP I2C bindings from the
> > free-form text format to json-schema.
> > 
> > Signed-off-by: Thierry Reding <treding@nvidia.com>
> > ---
> > Changes in v2:
> > - add missing additionalProperties: false
> > 
> >  .../bindings/i2c/nvidia,tegra186-bpmp-i2c.txt | 42 -------------------
> >  .../i2c/nvidia,tegra186-bpmp-i2c.yaml         | 42 +++++++++++++++++++
> >  2 files changed, 42 insertions(+), 42 deletions(-)
> >  delete mode 100644 Documentation/devicetree/bindings/i2c/nvidia,tegra186-bpmp-i2c.txt
> >  create mode 100644 Documentation/devicetree/bindings/i2c/nvidia,tegra186-bpmp-i2c.yaml
> > 
> > diff --git a/Documentation/devicetree/bindings/i2c/nvidia,tegra186-bpmp-i2c.txt b/Documentation/devicetree/bindings/i2c/nvidia,tegra186-bpmp-i2c.txt
> > deleted file mode 100644
> > index ab240e10debc..000000000000
> > --- a/Documentation/devicetree/bindings/i2c/nvidia,tegra186-bpmp-i2c.txt
> > +++ /dev/null
> > @@ -1,42 +0,0 @@
> > -NVIDIA Tegra186 BPMP I2C controller
> > -
> > -In Tegra186, the BPMP (Boot and Power Management Processor) owns certain HW
> > -devices, such as the I2C controller for the power management I2C bus. Software
> > -running on other CPUs must perform IPC to the BPMP in order to execute
> > -transactions on that I2C bus. This binding describes an I2C bus that is
> > -accessed in such a fashion.
> > -
> > -The BPMP I2C node must be located directly inside the main BPMP node. See
> > -../firmware/nvidia,tegra186-bpmp.txt for details of the BPMP binding.
> > -
> > -This node represents an I2C controller. See ../i2c/i2c.txt for details of the
> > -core I2C binding.
> > -
> > -Required properties:
> > -- compatible:
> > -    Array of strings.
> > -    One of:
> > -    - "nvidia,tegra186-bpmp-i2c".
> > -- #address-cells: Address cells for I2C device address.
> > -    Single-cell integer.
> > -    Must be <1>.
> > -- #size-cells:
> > -    Single-cell integer.
> > -    Must be <0>.
> > -- nvidia,bpmp-bus-id:
> > -    Single-cell integer.
> > -    Indicates the I2C bus number this DT node represent, as defined by the
> > -    BPMP firmware.
> > -
> > -Example:
> > -
> > -bpmp {
> > -	...
> > -
> > -	i2c {
> > -		compatible = "nvidia,tegra186-bpmp-i2c";
> > -		#address-cells = <1>;
> > -		#size-cells = <0>;
> > -		nvidia,bpmp-bus-id = <5>;
> > -	};
> > -};
> > diff --git a/Documentation/devicetree/bindings/i2c/nvidia,tegra186-bpmp-i2c.yaml b/Documentation/devicetree/bindings/i2c/nvidia,tegra186-bpmp-i2c.yaml
> > new file mode 100644
> > index 000000000000..351e12124959
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/i2c/nvidia,tegra186-bpmp-i2c.yaml
> > @@ -0,0 +1,42 @@
> > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> > +%YAML 1.2
> > +---
> > +$id: http://devicetree.org/schemas/i2c/nvidia,tegra186-bpmp-i2c.yaml#
> > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > +
> > +title: NVIDIA Tegra186 (and later) BPMP I2C controller
> > +
> > +maintainers:
> > +  - Thierry Reding <thierry.reding@gmail.com>
> > +  - Jon Hunter <jonathanh@nvidia.com>
> > +
> > +description: |
> > +  In Tegra186 and later, the BPMP (Boot and Power Management Processor)
> > +  owns certain HW devices, such as the I2C controller for the power
> > +  management I2C bus. Software running on other CPUs must perform IPC to
> > +  the BPMP in order to execute transactions on that I2C bus. This
> > +  binding describes an I2C bus that is accessed in such a fashion.
> > +
> > +  The BPMP I2C node must be located directly inside the main BPMP node.
> > +  See ../firmware/nvidia,tegra186-bpmp.yaml for details of the BPMP
> > +  binding.
> > +
> > +  This node represents an I2C controller. See ../i2c/i2c.txt for details
> > +  of the core I2C binding.
> > +
> > +properties:
> > +  compatible:
> > +    const: nvidia,tegra186-bpmp-i2c
> > +
> 
> > +  "#address-cells":
> > +    const: 1
> > +
> > +  "#size-cells":
> > +    const: 0
> 
> Covered by i2c-controller.yaml. Add a reference and then use 
> unevaluatedProperties.

About that: I've recently noticed that this doesn't seem to work
properly. I'm using branch draft2020-12 from your github and my
understanding was that this should give us support for
unevaluatedProperties. And indeed, it no longer complains about
#address-cells and #size-cells if I remove them from this binding,
presumably because it gets them from i2c-controller.yaml.

However, a side-effect seems to be that now it also ignores any
properties that aren't defined anywhere. So for example if I touch
up the example in firmware/nvidia,tegra186-bpmp.yaml and add a bogus
"foo-bar = <0>;" property in the BPMP I2C node, then it'll blindly
accept that as valid.

The validation will flag if I set #address-cells = <2> in the BPMP
I2C node, so validation of the schema still seems to work, but for
some reason it won't flag any properties that haven't been specified
in the schema.

Do I misunderstand how this is supposed to work, or is there something
wrong with the current implementation of unevaluatedProperties?

Thierry

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