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Fri, 05 Dec 2025 13:11:08 -0800 (PST) Date: Fri, 5 Dec 2025 18:12:41 -0300 From: Marcelo Schmitt To: Rob Herring Cc: David Lechner , Mark Brown , Krzysztof Kozlowski , Conor Dooley , Marcelo Schmitt , Michael Hennerich , Nuno =?iso-8859-1?Q?S=E1?= , Jonathan Cameron , Andy Shevchenko , Sean Anderson , linux-spi@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-iio@vger.kernel.org Subject: Re: [PATCH v3 7/7] dt-bindings: iio: adc: adi,ad4030: add data-lanes property Message-ID: References: <20251201-spi-add-multi-bus-support-v3-0-34e05791de83@baylibre.com> <20251201-spi-add-multi-bus-support-v3-7-34e05791de83@baylibre.com> <20251204213348.GA2198382-robh@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20251204213348.GA2198382-robh@kernel.org> On 12/04, Rob Herring wrote: > 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 > > --- > > 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. Unless I'm missing something, I think that would also describe the currently possible use cases as well. To me, it actually seems even more accurate than data-lanes. The data-lanes property only describes the SPI controller input lines/lanes, no info is given about the output lanes. Well yeah, that would only be a problem for a device with multiple input serializers and multiple output serializers. Still, the *-bus-width = , , ... ; notation looks clearer, IMHO. > > Rob >