linux-kernel - Re: [PATCH v3 1/2] dt-bindings: i2c: add binding for i2c-hotplug-gpio

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Message-ID: <20230811173752.GA3639776-robh@kernel.org>
Date:   Fri, 11 Aug 2023 11:37:52 -0600
From:   Rob Herring <robh@...nel.org>
To:     Svyatoslav Ryhel <clamor95@...il.com>
Cc:     Andi Shyti <andi.shyti@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Wolfram Sang <wsa@...nel.org>,
        Michał Mirosław <mirq-linux@...e.qmqm.pl>,
        linux-i2c@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 1/2] dt-bindings: i2c: add binding for i2c-hotplug-gpio

On Sat, Jul 29, 2023 at 07:08:56PM +0300, Svyatoslav Ryhel wrote:
> Document device tree schema which describes hot-pluggable via GPIO
> i2c bus.

What's that? 'hot-pluggable via GPIO i2c bus' is not coherent.

> 
> Signed-off-by: Svyatoslav Ryhel <clamor95@...il.com>
> ---
>  .../bindings/i2c/i2c-hotplug-gpio.yaml        | 65 +++++++++++++++++++
>  1 file changed, 65 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/i2c/i2c-hotplug-gpio.yaml
> 
> diff --git a/Documentation/devicetree/bindings/i2c/i2c-hotplug-gpio.yaml b/Documentation/devicetree/bindings/i2c/i2c-hotplug-gpio.yaml
> new file mode 100644
> index 000000000000..21f2b74ca6c1
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/i2c/i2c-hotplug-gpio.yaml
> @@ -0,0 +1,65 @@
> +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/i2c/i2c-hotplug-gpio.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: GPIO detected hot-plugged I2C bus
> +
> +maintainers:
> +  - Michał Mirosław <mirq-linux@...e.qmqm.pl>
> +
> +description:
> +  Driver for hot-plugged I2C busses, where some devices on a bus

Bindings are for h/w, not a driver.

> +  are hot-pluggable and their presence is indicated by GPIO line.
> +
> +properties:
> +  compatible:
> +    items:
> +      - const: i2c-hotplug-gpio
> +
> +  '#address-cells':
> +    const: 1
> +
> +  '#size-cells':
> +    const: 0

What are these for? You don't have any child nodes.

> +
> +  interrupts-extended:
> +    minItems: 1
> +
> +  detect-gpios:
> +    maxItems: 1
> +
> +  i2c-parent:
> +    maxItems: 1
> +
> +required:
> +  - compatible
> +  - '#address-cells'
> +  - '#size-cells'
> +  - interrupts-extended
> +  - detect-gpios
> +  - i2c-parent
> +
> +unevaluatedProperties: false
> +
> +examples:
> +  - |
> +    /*
> +     * Asus Transformers use I2C hotplug for attachable dock keyboard
> +     */
> +    #include <dt-bindings/gpio/gpio.h>
> +    #include <dt-bindings/interrupt-controller/irq.h>
> +
> +    i2c-dock {
> +        compatible = "i2c-hotplug-gpio";
> +
> +        #address-cells = <1>;
> +        #size-cells = <0>;
> +
> +        interrupts-extended = <&gpio 164 IRQ_TYPE_EDGE_BOTH>;
> +        detect-gpios = <&gpio 164 GPIO_ACTIVE_LOW>;

Looks like the same signal. You should only need one of them. Probably 
'detect-gpios' as I guess you need to read the state of the line.

> +
> +        i2c-parent = <&gen2_i2c>;

Couldn't you just add 'detect-gpios' to the existing bus node? It's 
really part of that bus and there's not a separate bus. That would be a 
lot simpler. I suppose you want to instantiate a driver, but that's not 
DT's problem.

Rob