linux-kernel - Re: [PATCH v8 4/6] dt-bindings: mfd: sensehat: Add Raspberry Pi Sense HAT schema

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Date:   Wed, 13 Apr 2022 15:38:51 +0200
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Charles Mirabile <cmirabil@...hat.com>,
        linux-kernel@...r.kernel.org
Cc:     Serge Schneider <serge@...pberrypi.org>,
        Stefan Wahren <stefan.wahren@...e.com>,
        Nicolas Saenz Julienne <nsaenzju@...hat.com>,
        Mattias Brugger <mbrugger@...e.com>,
        linux-rpi-kernel@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, fedora-rpi@...glegroups.com,
        Miguel Ojeda <ojeda@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Lee Jones <lee.jones@...aro.org>, devicetree@...r.kernel.org,
        linux-input@...r.kernel.org, Mwesigwa Guma <mguma@...hat.com>,
        Joel Savitz <jsavitz@...hat.com>
Subject: Re: [PATCH v8 4/6] dt-bindings: mfd: sensehat: Add Raspberry Pi Sense
 HAT schema

On 12/04/2022 22:13, Charles Mirabile wrote:
> This patch adds the device tree bindings for the Sense HAT
> and each of its children devices in yaml form.
>

Thank you for your patch. There is something to discuss/improve.

> +description:
> +  This device is part of the sensehat multi function device.
> +  For more information see ../mfd/raspberrypi,sensehat.yaml.
> +
> +  This device features a programmable 8x8 RGB LED matrix.
> +
> +properties:
> +  compatible:
> +    const: raspberrypi,sensehat-display

This binding is practically empty, so I wonder what's is purpose? Do you
plan to grow it? If this was already explained, sorry for bringing it up
again... :)

> +
> +required:
> +  - compatible
> +
> +additionalProperties: false
> diff --git a/Documentation/devicetree/bindings/input/raspberrypi,sensehat-joystick.yaml b/Documentation/devicetree/bindings/input/raspberrypi,sensehat-joystick.yaml
> new file mode 100644
> index 000000000000..c97cd1d8eac6
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/input/raspberrypi,sensehat-joystick.yaml
> @@ -0,0 +1,33 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/input/raspberrypi,sensehat-joystick.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Raspberry Pi Sensehat Joystick
> +
> +maintainers:
> +  - Charles Mirabile <cmirabil@...hat.com>
> +  - Mwesigwa Guma <mguma@...hat.com>
> +  - Joel Savitz <jsavitz@...hat.com>
> +
> +description:
> +  This device is part of the sensehat multi function device.
> +  For more information see ../mfd/raspberrypi,sensehat.yaml.
> +
> +  This device features a five button joystick (up, down,left,
> +  right, click)
> +
> +properties:
> +  compatible:
> +    const: raspberrypi,sensehat-joystick
> +
> +  interrupts:
> +    items:
> +      - description: pin number for joystick interrupt

Description is obvious, so just "maxItems: 1"

> +
> +required:
> +  - compatible
> +  - interrupts
> +
> +additionalProperties: false
> diff --git a/Documentation/devicetree/bindings/mfd/raspberrypi,sensehat.yaml b/Documentation/devicetree/bindings/mfd/raspberrypi,sensehat.yaml
> new file mode 100644
> index 000000000000..2484ec91b430
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/mfd/raspberrypi,sensehat.yaml
> @@ -0,0 +1,69 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/mfd/raspberrypi,sensehat.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Raspberry Pi Sensehat
> +
> +maintainers:
> +  - Charles Mirabile <cmirabil@...hat.com>
> +  - Mwesigwa Guma <mguma@...hat.com>
> +  - Joel Savitz <jsavitz@...hat.com>
> +
> +description:
> +  The Raspberry Pi Sensehat is an addon board originally developed
> +  for the Raspberry Pi that has a joystick and an 8x8 RGB LED display
> +  as well as several environmental sensors. It connects via i2c and
> +  a gpio for irq.
> +
> +properties:
> +  compatible:
> +    const: raspberrypi,sensehat
> +
> +  reg:
> +    items:
> +      - description: i2c device address

Description is obvious, so just "maxItems: 1"

> +
> +  "#address-cells":
> +    const: 1
> +
> +  "#size-cells":
> +    const: 0

Why do you need these? You are not allowing any children with unit
addresses.

> +
> +  "joystick":
> +    $ref: ../input/raspberrypi,sensehat-joystick.yaml

Full path, so "/schemas/input/raspberrypi,sensehat-joystick.yaml#"

> +
> +  "display":
> +    $ref: ../auxdisplay/raspberrypi,sensehat-display.yaml

The same.

> +
> +required:
> +  - compatible
> +  - reg
> +  - "#address-cells"
> +  - "#size-cells"
> +  - joystick
> +  - display
> +
> +additionalProperties: false
> +
> +examples:
> +  - |
> +    #include <dt-bindings/gpio/gpio.h>
> +    i2c {
> +      #address-cells = <1>;
> +      #size-cells = <0>;
> +      sensehat@46 {

Generic node names please, so "hat".

> +        #address-cells = <1>;
> +        #size-cells = <0>;
> +        compatible = "raspberrypi,sensehat";
> +        reg = <0x46>;

Could you put compatible and then reg at beginning of properties (before
address/size)? It is more common convention and these are more important
properties.

> +        display {
> +          compatible = "raspberrypi,sensehat-display";
> +        };
> +        joystick {
> +          compatible = "raspberrypi,sensehat-joystick";
> +          interrupts = <23 GPIO_ACTIVE_HIGH>;

This does not look like proper interrupt flag. Wrong constant.

> +        };
> +      };
> +    };


Best regards,
Krzysztof