linux-kernel - Re: [PATCH v2 1/6] spi: dt-bindings: Add spi-data-buses property

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Message-ID: <20251118155717.GA3236324-robh@kernel.org>
Date: Tue, 18 Nov 2025 09:57:17 -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 v2 1/6] spi: dt-bindings: Add spi-data-buses property

On Fri, Nov 07, 2025 at 02:52:47PM -0600, David Lechner wrote:
> Add a spi-data-buses property to the spi-peripheral-props binding to
> allow specifying the SPI data bus or buses that a peripheral is
> connected to in cases where the SPI controller has more than one
> physical SPI data bus.
> 
> Signed-off-by: David Lechner <dlechner@...libre.com>
> ---
> 
> v2 changes:
> * Renamed property from spi-buses to spi-data-buses to make it clear
>   that we are only talking about the SDI/SDO lines and not the entire
>   SPI bus (SCK, CS, etc).
> * Fixed prefix order in subject.
> 
> This patch has been seen before in a different series from Sean [1].
> 
> [1]: https://lore.kernel.org/linux-spi/20250616220054.3968946-2-sean.anderson@linux.dev/
> 
> Changes:
> * Added maxItems. (8 is the most I've seen so far on an ADC)
> * Tweaked the description a bit.
> ---
>  .../devicetree/bindings/spi/spi-peripheral-props.yaml        | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/spi/spi-peripheral-props.yaml b/Documentation/devicetree/bindings/spi/spi-peripheral-props.yaml
> index 8b6e8fc009dbdc80978f3afef84ddc688ade4348..6fe739eaf09876b9c5d8902f792ca02181d7266f 100644
> --- a/Documentation/devicetree/bindings/spi/spi-peripheral-props.yaml
> +++ b/Documentation/devicetree/bindings/spi/spi-peripheral-props.yaml
> @@ -89,6 +89,18 @@ properties:
>      description:
>        Delay, in microseconds, after a write transfer.
>  
> +  spi-data-buses:

I think spi-data-map would be better.

Or we could just reuse 'data-lanes' property. It seems like the same 
problem of mapping peripheral lanes/lines to controller/host 
lanes/lines.

> +    description:
> +      Array of data bus numbers that describes which SPI data buses of the
> +      controller are connected to the peripheral. This only applies to
> +      peripherals connected to specialized SPI controllers that have multiple
> +      SPI data buses (a set of independent SDI/SDO lines each with its own
> +      serializer) on a single controller.

Please make it clear what's the index and what's the value: "The index 
corresponds to the peripheral data line and the value corresponds to the 
controller data line."

> +    $ref: /schemas/types.yaml#/definitions/uint32-array
> +    minItems: 1
> +    maxItems: 8
> +    default: [0]
> +
>    stacked-memories:
>      description: Several SPI memories can be wired in stacked mode.
>        This basically means that either a device features several chip
> 
> -- 
> 2.43.0
>