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

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Message-ID: <176771732187.2212863.8498767353794540092.robh@kernel.org>
Date: Tue, 6 Jan 2026 10:36:13 -0600
From: "Rob Herring (Arm)" <robh@...nel.org>
To: David Lechner <dlechner@...libre.com>
Cc: linux-iio@...r.kernel.org, Andy Shevchenko <andy@...nel.org>,
	devicetree@...r.kernel.org,
	Nuno Sá <nuno.sa@...log.com>,
	Jonathan Cameron <jic23@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Sean Anderson <sean.anderson@...ux.dev>,
	linux-kernel@...r.kernel.org, linux-spi@...r.kernel.org,
	Michael Hennerich <michael.hennerich@...log.com>,
	Marcelo Schmitt <marcelo.schmitt@...log.com>,
	Mark Brown <broonie@...nel.org>
Subject: Re: [PATCH v4 1/9] spi: dt-bindings: change spi-{rx,tx}-bus-width to
 arrays


On Fri, 19 Dec 2025 15:32:09 -0600, 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.
> ---
>  .../bindings/display/panel/sitronix,st7789v.yaml   |  5 +--
>  .../devicetree/bindings/iio/adc/adi,ad4030.yaml    | 42 +++++++++++++++++++++-
>  .../devicetree/bindings/iio/adc/adi,ad4695.yaml    |  5 +--
>  .../bindings/spi/allwinner,sun4i-a10-spi.yaml      |  6 ++--
>  .../bindings/spi/allwinner,sun6i-a31-spi.yaml      |  6 ++--
>  .../bindings/spi/nvidia,tegra210-quad.yaml         |  6 ++--
>  .../bindings/spi/spi-peripheral-props.yaml         | 26 ++++++++++----
>  7 files changed, 79 insertions(+), 17 deletions(-)
> 

You'll need to add spi/andestech,ae350-spi.yaml which is only in Mark's 
tree, but otherwise:

Reviewed-by: Rob Herring (Arm) <robh@...nel.org>