linux-kernel - Re: [PATCH 1/9] dt-bindings: misc: Describe TI FPC202 dual port controller

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Message-ID: <20241108-reimburse-saucy-2682e370469a@spud>
Date: Fri, 8 Nov 2024 18:23:37 +0000
From: Conor Dooley <conor@...nel.org>
To: Romain Gantois <romain.gantois@...tlin.com>
Cc: Wolfram Sang <wsa+renesas@...g-engineering.com>,
	Tomi Valkeinen <tomi.valkeinen@...asonboard.com>,
	Luca Ceresoli <luca.ceresoli@...tlin.com>,
	Andi Shyti <andi.shyti@...nel.org>, Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Derek Kiernan <derek.kiernan@....com>,
	Dragan Cvetic <dragan.cvetic@....com>,
	Arnd Bergmann <arnd@...db.de>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Mauro Carvalho Chehab <mchehab@...nel.org>,
	Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
	Kory Maincent <kory.maincent@...tlin.com>,
	linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org,
	devicetree@...r.kernel.org, linux-media@...r.kernel.org
Subject: Re: [PATCH 1/9] dt-bindings: misc: Describe TI FPC202 dual port
 controller

On Fri, Nov 08, 2024 at 04:36:53PM +0100, Romain Gantois wrote:
> The FPC202 dual port controller serves as a low speed signal aggregator for
> common port types, notably SFP. It provides access to I2C and low-speed
> GPIO signals of a downstream device through a single upstream control
> interface.
> 
> Up to two logical I2C addresses can be accessed on each of the FPC202's
> ports. The port controller acts as an I2C translator (ATR). It converts
> addresses of incoming and outgoing I2C transactions. One use case of this
> is accessing two SFP modules at logical address 0x50 from the same upstream
> I2C controller, using two different client aliases.
> 
> Signed-off-by: Romain Gantois <romain.gantois@...tlin.com>
> ---
>  .../devicetree/bindings/misc/ti,fpc202.yaml        | 75 ++++++++++++++++++++++
>  1 file changed, 75 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/misc/ti,fpc202.yaml b/Documentation/devicetree/bindings/misc/ti,fpc202.yaml
> new file mode 100644
> index 0000000000000000000000000000000000000000..ad11abe11e68aa266acdd6b43a5b425340bbbba8
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/misc/ti,fpc202.yaml
> @@ -0,0 +1,75 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/misc/ti,fpc202.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: TI FPC202 dual port controller with expanded IOs
> +
> +maintainers:
> +  - Romain Gantois <romain.gantois@...tlin.com>
> +
> +allOf:
> +  - $ref: /schemas/i2c/i2c-atr.yaml#

Gotta say, this looks absolutely nothing like the other i2c-atr user!

> +
> +properties:
> +  compatible:
> +    const: ti,fpc202
> +
> +  reg:
> +    maxItems: 1
> +
> +  gpio-controller: true
> +
> +  "#gpio-cells":
> +    const: 2
> +
> +  enable-gpios:
> +    description:
> +      Specifier for the GPIO connected to the EN pin.
> +    maxItems: 1
> +
> +  port0:

ports usually go in a ports node, and are port@0 not port0. That said,
these are i2c buses, so the node name would usually be i2c@ for those.
In fact, given you have i2c-mux as your node name, the binding for that
expects you to format your child nodes like '^i2c@[0-9a-f]+$'. Is there
a reason you can't just drop this ports business and go with a pattern
property here that restricts the pattern to '^i2c@[0-1]$'?

> +    $ref: /schemas/i2c/i2c-controller.yaml
> +    description:
> +      Device port 0, accessible over I2C.
> +
> +  port1:
> +    $ref: /schemas/i2c/i2c-controller.yaml
> +    description:
> +      Device port 1, accessible over I2C.
> +
> +
> +required:
> +  - compatible
> +  - gpio-controller
> +  - "#gpio-cells"
> +  - reg
> +
> +unevaluatedProperties: false
> +
> +examples:
> +  - |
> +    i2c {
> +        #address-cells = <1>;
> +        #size-cells = <0>;
> +
> +        fpc202: i2c-mux@f {

The label here is uused, you should drop it.

Cheers,
Conor.

> +            compatible = "ti,fpc202";
> +            reg = <0xf>;
> +
> +            gpio-controller;
> +            #gpio-cells = <2>;
> +
> +            port0 {
> +                #address-cells = <1>;
> +                #size-cells = <0>;
> +            };
> +
> +            port1 {
> +                #address-cells = <1>;
> +                #size-cells = <0>;
> +            };
> +        };
> +    };
> +...
> 
> -- 
> 2.47.0
> 

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