Re: [PATCH v4 1/3] dt-bindings: iio: adc: sophgo,cv18xx-saradc.yaml: Add Sophgo CV18XX SARADC binding

Conor Dooley
2024-08-20T16:38:49Z

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On Tue, Aug 20, 2024 at 06:21:07PM +0200, Thomas Bonnefille wrote:
> Hello Conor,
>
> On 8/12/24 5:53 PM, Conor Dooley wrote:
> > On Mon, Aug 12, 2024 at 05:00:55PM +0200, Thomas Bonnefille wrote:
> > > The Sophgo SARADC is a Successive Approximation ADC that can be found in
> > > the Sophgo SoC.
> > >
> > > Signed-off-by: Thomas Bonnefille <thomas.bonnefille@bootlin.com>
> > > ---
> > > .../bindings/iio/adc/sophgo,cv18xx-saradc.yaml | 85 ++++++++++++++++++++++
> > > 1 file changed, 85 insertions(+)
> > >
> > > diff --git a/Documentation/devicetree/bindings/iio/adc/sophgo,cv18xx-saradc.yaml b/Documentation/devicetree/bindings/iio/adc/sophgo,cv18xx-saradc.yaml
> > > new file mode 100644
> > > index 000000000000..846590808e5f
> > > --- /dev/null
> > > +++ b/Documentation/devicetree/bindings/iio/adc/sophgo,cv18xx-saradc.yaml
> > > @@ -0,0 +1,85 @@
> > > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> > > +%YAML 1.2
> > > +---
> > > +$id: http://devicetree.org/schemas/iio/adc/sophgo,cv18xx-saradc.yaml#
> >
> > Filename matching the compatible please.
> >
> > > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > > +
> > > +title:
> > > + Sophgo CV18XX SoC series 3 channels Successive Approximation Analog to
> > > + Digital Converters
> > > +
> > > +maintainers:
> > > + - Thomas Bonnefille <thomas.bonnefille@bootlin.com>
> > > +
> > > +description:
> > > + Datasheet at https://github.com/sophgo/sophgo-doc/releases
> > > +
> > > +properties:
> > > + compatible:
> > > + const: sophgo,cv1800b-saradc
> > > +
> > > + reg:
> > > + maxItems: 1
> > > +
> > > + interrupts:
> > > + maxItems: 1
> > > +
> > > + clocks:
> > > + maxItems: 1
> > > +
> > > + '#address-cells':
> > > + const: 1
> > > +
> > > + '#size-cells':
> > > + const: 0
> > > +
> > > +patternProperties:
> > > + "^channel@[0-3]+$":
> > > + $ref: adc.yaml
> > > +
> > > + description: |
> >
> > This | is not required.
> >
> > > + Represents the channels of the ADC.
> > > +
> > > + properties:
> > > + reg:
> > > + description: |
> > > + The channel number. It can have up to 3 channels numbered from 0 to 2.
> > > + items:
> > > + - minimum: 0
> > > + maximum: 2
> >
> > Is this sufficient to limit the number of channels to 3? Aren't you relying
> > on the unique unit addresses warning in dtc to limit it, rather than
> > actually limiting with min/maxItems?
> >
> It seems like I can't use min/maxItems on this property. I think that it is
> using size-cells + address-cells to deduce that the number of items should
> be equal to 1.

I think I was mistaken in talking about mix/max items here. I had the
right idea, but mentioned an incorrect solution - sorry about that. I
wasn't talking about the number of elements in the reg property, what I
meant was limiting the number of channel nodes in the first place -
something which min/maxItems cannot do. As examples of the problem I was
thinking of, see the below two examples:

adc@30f0000 {
compatible = "sophgo,cv1800b-saradc";
reg = <0x030f0000 0x1000>;
clocks = <&clk CLK_SARADC>;
interrupts = <100 IRQ_TYPE_LEVEL_HIGH>;
#address-cells = <1>;
#size-cells = <0>;

channel@0 {
reg = <0>;
};
channel@2 {
reg = <2>;
};
channel@22 {
reg = <2>;
};
};

adc@30f0000 {
compatible = "sophgo,cv1800b-saradc";
reg = <0x030f0000 0x1000>;
clocks = <&clk CLK_SARADC>;
interrupts = <100 IRQ_TYPE_LEVEL_HIGH>;
#address-cells = <1>;
#size-cells = <0>;

channel@0 {
reg = <0>;
};
channel@2 {
reg = <2>;
};
channel@22 {
reg = <2>;
};
};

The solution is simple, remove the + from the regex. Sorry for sending
you on the wrong track Thomas.

Thanks,
Conor.

> Looking at the dtschema repository it seems to be the case in reg.yaml with
> address-cells/size-cells = 2/2, 1/1 and 2/1.
> If I try to use maxItems here :
>
> properties:
> reg:
> maxItems: 1
> items:
> - minimum: 0
> maximum: 2
>
> I get this strange error message from `make dt_binding_check`:
>
> DTEX
> Documentation/devicetree/bindings/iio/adc/sophgo,cv1800b-saradc.example.dts
> /home/thomas/linux/Documentation/devicetree/bindings/iio/adc/sophgo,cv1800b-saradc.yaml:
> patternProperties:^channel@[0-2]+$:properties:reg: {'maxItems': 1, 'items':
> [{'minimum': 0, 'maximum': 2}]} should not be valid under {'required':
> ['maxItems']}
> hint: "maxItems" is not needed with an "items" list
> from schema $id: http://devicetree.org/meta-schemas/items.yaml#
> /home/thomas/linux/Documentation/devicetree/bindings/iio/adc/sophgo,cv1800b-saradc.yaml:
> patternProperties:^channel@[0-2]+$:properties:reg: 'anyOf' conditional
> failed, one must be fixed:
> 'items' is not one of ['maxItems', 'description', 'deprecated']
> hint: Only "maxItems" is required for a single entry if there are no
> constraints defined for the values.
> 'maxItems' is not one of ['description', 'deprecated', 'const', 'enum',
> 'minimum', 'maximum', 'multipleOf', 'default', '$ref', 'oneOf']
> 'items' is not one of ['description', 'deprecated', 'const', 'enum',
> 'minimum', 'maximum', 'multipleOf', 'default', '$ref', 'oneOf']
> 1 is less than the minimum of 2
> hint: Arrays must be described with a combination of
> minItems/maxItems/items
> hint: cell array properties must define how many entries and what the
> entries are when there is more than one entry.
> from schema $id: http://devicetree.org/meta-schemas/core.yaml#
>
> Isn't it okay to just use minimum and maximum and rely on
> address-cells/size-cells for the number of items allowed ?
>

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