linux-kernel - Re: [PATCH v2 1/2] dt-bindings: mtd: spi-nand: Convert to DT schema format

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Message-ID: <YUj6RUNYDoWA30Ln@robh.at.kernel.org>
Date:   Mon, 20 Sep 2021 16:16:53 -0500
From:   Rob Herring <robh@...nel.org>
To:     Serge Semin <fancer.lancer@...il.com>
Cc:     Apurva Nandan <a-nandan@...com>,
        Miquel Raynal <miquel.raynal@...tlin.com>,
        Richard Weinberger <richard@....at>,
        Vignesh Raghavendra <vigneshr@...com>,
        Mark Brown <broonie@...nel.org>, linux-mtd@...ts.infradead.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-spi@...r.kernel.org, michael@...le.cc
Subject: Re: [PATCH v2 1/2] dt-bindings: mtd: spi-nand: Convert to DT schema
 format

On Mon, Sep 20, 2021 at 06:06:51PM +0300, Serge Semin wrote:
> Hello Apurva
> 
> On Mon, Sep 20, 2021 at 07:57:12PM +0530, Apurva Nandan wrote:
> > Convert spi-nand.txt binding to YAML format with an added example.
> > 
> > Signed-off-by: Apurva Nandan <a-nandan@...com>
> > ---
> >  .../devicetree/bindings/mtd/spi-nand.txt      |  5 --
> >  .../devicetree/bindings/mtd/spi-nand.yaml     | 62 +++++++++++++++++++
> >  2 files changed, 62 insertions(+), 5 deletions(-)
> >  delete mode 100644 Documentation/devicetree/bindings/mtd/spi-nand.txt
> >  create mode 100644 Documentation/devicetree/bindings/mtd/spi-nand.yaml
> 
> Thanks for the bindings conversion patch. There are several comments
> below. But before addressing them it would be better to also get a
> response from Rob.
> 
> > 
> > diff --git a/Documentation/devicetree/bindings/mtd/spi-nand.txt b/Documentation/devicetree/bindings/mtd/spi-nand.txt
> > deleted file mode 100644
> > index 8b51f3b6d55c..000000000000
> > --- a/Documentation/devicetree/bindings/mtd/spi-nand.txt
> > +++ /dev/null
> > @@ -1,5 +0,0 @@
> > -SPI NAND flash
> > -
> > -Required properties:
> > -- compatible: should be "spi-nand"
> > -- reg: should encode the chip-select line used to access the NAND chip
> > diff --git a/Documentation/devicetree/bindings/mtd/spi-nand.yaml b/Documentation/devicetree/bindings/mtd/spi-nand.yaml
> > new file mode 100644
> > index 000000000000..601beba8d971
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/mtd/spi-nand.yaml
> > @@ -0,0 +1,62 @@
> > +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
> > +%YAML 1.2
> > +---
> > +$id: http://devicetree.org/schemas/mtd/spi-nand.yaml#
> > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > +
> > +title: SPI NAND flash
> > +
> > +maintainers:
> > +  - Apurva Nandan <a-nandan@...com>
> > +
> > +allOf:
> > +  - $ref: "mtd.yaml#"
> > +
> > +properties:
> > +  compatible:
> > +    const: spi-nand
> > +
> > +  reg:
> > +    maxItems: 1
> > +
> 
> > +  spi-max-frequency: true
> > +  spi-rx-bus-width: true
> > +  spi-tx-bus-width: true
> > +  rx-sample-delay-ns: true
> 
> Since it's an SPI-client device there are more than these properties
> could be set for it. See the SPI-controller bindings schema:
> Documentation/devicetree/bindings/spi/spi-controller.yaml
> So there is two possible ways to make it more generic:
> 1) Detach the spi-client part from the spi-controller.yaml bindings
> into a dedicated DT-schema file and refer to that new scheme from
> here.

Yes, as mentioned there's patches doing this. But the above is fine. 
There's some value in defining here which properties are valid.

> 2) Forget about these controller-specific properties and let the
> parental SPI-controller bindings parsing them. Of course there must be
> at least one of the next properties declared for it to work:
> {unevaluatedProperties, additionalProperties}.
> 
> It's up to Rob to decided which approach is better though...
> 
> > +
> > +  '#address-cells': true
> > +  '#size-cells': true
> 
> Aren't they always equal to 1?

No SPI nand devices >4GB?

> 
> > +
> > +additionalProperties:
> > +  type: object
> 
> I'd suggest to elaborate the way the partition sub-nodes looks
> like, for instance, the node names, supported compatible names,
> labels, etc.

That should probably all be in mtd.yaml. The question here is whether 
partitions are always under a 'partitions' node. Maybe this is new 
enough that only the new way has to be supported. Though if mtd.yaml 
supported both forms, allowing both all the time is okay IMO.

Rob