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

Rob Herring
2023-08-11T17:37:57Z

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@gmail.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@rere.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