linux-kernel - Re: [PATCH 2/4] dt-bindings: iio: magnetometer: Add DT binding for Voltafield AF8133J

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Message-ID: <i2q2vntbhilrpwppzl367ndoetbyd6guyti4t4n7vtg5pwq7bi@tjkio7zpwrfw>
Date: Mon, 12 Feb 2024 14:38:40 +0100
From: Ondřej Jirman <megi@....cz>
To: Jonathan Cameron <Jonathan.Cameron@...wei.com>
Cc: Jonathan Cameron <jic23@...nel.org>, 
	Lars-Peter Clausen <lars@...afoo.de>, Rob Herring <robh+dt@...nel.org>, 
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>, Conor Dooley <conor+dt@...nel.org>, 
	Andrey Skvortsov <andrej.skvortzov@...il.com>, Icenowy Zheng <icenowy@...c.io>, linux-iio@...r.kernel.org, 
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/4] dt-bindings: iio: magnetometer: Add DT binding for
 Voltafield AF8133J

Hi Jonathan,

thanks for the feedback.

On Mon, Feb 12, 2024 at 11:47:38AM +0000, Jonathan Cameron wrote:
> On Sun, 11 Feb 2024 21:51:58 +0100
> Ondřej Jirman <megi@....cz> wrote:
> 
> > From: Icenowy Zheng <icenowy@...c.io>
> 
> Title doesn't need to mention binding (it's implicit from the dt-bindings bit
> dt-bindings: iio: magnetometer: Add Voltafield AF8133J
> 
> > 
> > Voltafield AF8133J is a simple magnetometer sensor produced by Voltafield
> > Technology Corp, with dual power supplies (one for core and one for I/O)
> > and active-low reset pin.
> > 
> > The sensor has configurable range 1.2 - 2.2 mT and a software controlled
> > standby mode.
> > 
> > Add a device tree binding for it.
> > 
> > Signed-off-by: Icenowy Zheng <icenowy@...c.io>
> > Signed-off-by: Ondřej Jirman <megi@....cz>
> 
> Hi Ondřej
> 
> A few quick comments.
> 
> 
> > ---
> >  .../iio/magnetometer/voltafield,af8133j.yaml  | 58 +++++++++++++++++++
> >  1 file changed, 58 insertions(+)
> >  create mode 100644 Documentation/devicetree/bindings/iio/magnetometer/voltafield,af8133j.yaml
> > 
> > diff --git a/Documentation/devicetree/bindings/iio/magnetometer/voltafield,af8133j.yaml b/Documentation/devicetree/bindings/iio/magnetometer/voltafield,af8133j.yaml
> > new file mode 100644
> > index 000000000000..ab56c0f798ad
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/iio/magnetometer/voltafield,af8133j.yaml
> > @@ -0,0 +1,58 @@
> > +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
> > +%YAML 1.2
> > +---
> > +$id: http://devicetree.org/schemas/iio/magnetometer/voltafield,af8133j.yaml#
> > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > +
> > +title: Voltafield AF8133J magnetometer sensor
> > +
> > +maintainers:
> > +  - Ondřej Jirman <megi@....cz>
> > +
> > +properties:
> > +  compatible:
> > +    - voltafield,af8133j
> Test your bindings (as described in the bot message).
>     const: voltafield,af8133j

I did, but didn't notice that DT_SCHEMA_FILES= didn't work as expected when
provided with full path to the bindings file. :)

Just using DT_SCHEMA_FILES=voltafield,af8133j.yaml works better and catches this
issue.

> > +
> > +  reg:
> > +    maxItems: 1
> > +
> > +  reset-gpios:
> > +    description: |
> No need for the | as the formatting doesn't need to be preserved.
> 
> > +      an pin needed for AF8133J to set the reset state. This should be usually
> 
> A pin
> 
> > +      active low.
> > +
> > +  avdd-supply:
> > +    description: |
> > +      an optional regulator that needs to be on to provide AVDD power (Working
> 
> An optional (if it were optional, A regulator if not)
> 
> > +      power, usually 3.3V) to the sensor.
> Seems unlikely the power supply is optional (though specifying it in DT might be -
> however see below).
> 
> > +
> > +  dvdd-supply:
> > +    description: |
> > +      an optional regulator that needs to be on to provide DVDD power (Digital
> > +      IO power, 1.8V~AVDD) to the sensor.
> > +
> > +  mount-matrix:
> > +    description: an optional 3x3 mounting rotation matrix.
> > +
> > +required:
> > +  - compatible
> > +  - reg
> 
> Any power supply that is required for operation should be listed here (even though
> we can rely on the stub supplies if it isn't in the DT).
> I used to think this wasn't necessary, so lots of bindings upstream don't yet
> have it.

By stub supply you mean dummy supply created when the *-supply property is not
specified in DT? Or something else?

Because DTC_CHK prints a warning if I make the proerty required in bindings and
not specify it in DT

arch/arm64/boot/dts/allwinner/sun50i-a64-pinephone-1.2b.dtb: magnetometer@1c: 'avdd-supply' is a required property
	from schema $id: http://devicetree.org/schemas/iio/magnetometer/voltafield,af8133j.yaml#


kind regards,
	o.

> > +
> > +additionalProperties: false
> > +
> > +examples:
> > +  - |
> > +    #include <dt-bindings/interrupt-controller/irq.h>
> > +    #include <dt-bindings/gpio/gpio.h>
> > +    i2c {
> > +        #address-cells = <1>;
> > +        #size-cells = <0>;
> > +
> > +        magnetometer@1c {
> > +            compatible = "voltafield,af8133j";
> > +            reg = <0x1c>;
> > +            avdd-supply = <&reg_dldo1>;
> > +            dvdd-supply = <&reg_dldo1>;
> > +            reset-gpios = <&pio 1 1 GPIO_ACTIVE_LOW>;
> > +        };
> > +    };
>