linux-kernel - Re: [PATCH v3 7/7] dt-bindings: iio: adc: adi,ad4030: add data-lanes property

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Message-ID: <20251204213348.GA2198382-robh@kernel.org>
Date: Thu, 4 Dec 2025 15:33:48 -0600
From: Rob Herring <robh@...nel.org>
To: David Lechner <dlechner@...libre.com>
Cc: Mark Brown <broonie@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Marcelo Schmitt <marcelo.schmitt@...log.com>,
	Michael Hennerich <michael.hennerich@...log.com>,
	Nuno Sá <nuno.sa@...log.com>,
	Jonathan Cameron <jic23@...nel.org>,
	Andy Shevchenko <andy@...nel.org>,
	Sean Anderson <sean.anderson@...ux.dev>, linux-spi@...r.kernel.org,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-iio@...r.kernel.org
Subject: Re: [PATCH v3 7/7] dt-bindings: iio: adc: adi,ad4030: add data-lanes
 property

On Mon, Dec 01, 2025 at 08:20:45PM -0600, David Lechner wrote:
> Add data-lanes property to specify the number of data lanes used on the
> ad463x chips that support reading two samples at the same time using
> two data lanes with a capable SPI controller.
> 
> Signed-off-by: David Lechner <dlechner@...libre.com>
> ---
> v3 changes: new patch
> 
> I added this one to give a real-world use case where spi-rx-bus-width
> was not sufficient to fully describe the hardware configuration.
> 
> spi-rx-bus-width = <4>; alone could be be interpreted as either:
> 
> +--------------+    +----------+
> | SPI          |    | AD4630   |
> | Controller   |    | ADC      |
> |              |    |          |
> |        SDIA0 |<---| SDOA0    |
> |        SDIA1 |<---| SDOA1    |
> |        SDIA2 |<---| SDOA2    |
> |        SDIA3 |<---| SDOA3    |
> |              |    |          |
> |        SDIB0 |x   | SDOB0    |
> |        SDIB1 |x   | SDOB1    |
> |        SDIB2 |x   | SDOB2    |
> |        SDIB3 |x   | SDOB3    |
> |              |    |          |
> +--------------+     +---------+
> 
> or
> 
> +--------------+    +----------+
> | SPI          |    | AD4630   |
> | Controller   |    | ADC      |
> |              |    |          |
> |        SDIA0 |<---| SDOA0    |
> |        SDIA1 |<---| SDOA1    |
> |        SDIA2 |x   | SDOA2    |
> |        SDIA3 |x   | SDOA3    |
> |              |    |          |
> |        SDIB0 |<---| SDOB0    |
> |        SDIB1 |<---| SDOB1    |
> |        SDIB2 |x   | SDOB2    |
> |        SDIB3 |x   | SDOB3    |
> |              |    |          |
> +--------------+     +---------+
> 
> Now, with data-lanes having a default value of [0] (inherited from
> spi-peripheral-props.yaml), specifying:
> 
>     spi-rx-bus-width = <4>;
> 
> is unambiguously the first case and the example given in the binding
> documentation is the second case:
> 
>     spi-rx-bus-width = <2>;
>     data-lanes = <0>, <1>;

I just reviewed this and all, but what if you just did:

spi-rx-bus-width = <2>, <2>;

So *-bus-width becomes equal to the number of serializers/channels.

Rob