linux-kernel - Re: [PATCH v4 1/9] spi: dt-bindings: change spi-{rx,tx}-bus-width to arrays

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Message-ID: <aV-ii6pdDYA02euV@debian-BULLSEYE-live-builder-AMD64>
Date: Thu, 8 Jan 2026 09:26:51 -0300
From: Marcelo Schmitt <marcelo.schmitt1@...il.com>
To: David Lechner <dlechner@...libre.com>
Cc: Mark Brown <broonie@...nel.org>, Rob Herring <robh@...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 v4 1/9] spi: dt-bindings: change spi-{rx,tx}-bus-width to
 arrays

On 12/19, David Lechner wrote:
> Change spi-rx-bus-width and spi-tx-bus-width properties from single
> uint32 values to arrays of uint32 values. This allows describing SPI
> peripherals connected to controllers that have multiple data lanes for
> receiving or transmitting two or more words in parallel.
> 
> Each index in the array corresponds to a physical data lane (one or more
> wires depending on the bus width). Additional mapping properties will be
> needed in cases where a lane on the controller or peripheral is skipped.
> 
> Bindings that make use of this property are updated in the same commit
> to avoid validation errors.
> 
> The adi,ad4030 binding can now better describe the chips multi-lane
> capabilities, so that binding is refined and gets a new example.
> 
> Converting from single uint32 to array of uint32 does not break .dts/
> .dtb files since there is no difference between specifying a single
> uint32 value and an array with a single uint32 value in devicetree.
> 
> Signed-off-by: David Lechner <dlechner@...libre.com>
> ---
> 
> v4 changes:
> - New patch to replace data-lanes property patch.
> 
> In v3, Rob suggested possibly splitting the spi-controller.yaml file
> to have a way to make most SPI controllers have maxItems: 1 for these
> properties. I would like to avoid that because it doesn't seem scalable,
> e.g. if we need another similar split in the future, the number of
> combinations would grow exponentially (factorially?). I have an idea to
> instead do this using $dynamicAnchor and $dynamicRef, but dt-schema
> doesn't currently support that. So I propose we do the best we can for
> now with the current dt-schema and make further improvements later.
> 
> Also, in v3, I suggested that we could have leading 0s in the arrays
> to indicate unused lanes. But after further consideration, I think it's
> better to have separate lane-mapping properties for that purpose. It
> will be easier to explain and parse and be a bit more flexible that way.

LGTM
Reviewed-by: Marcelo Schmitt <marcelo.schmitt@...log.com>