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

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Message-ID: <20210920150651.vvdhennblwhdi3jw@mobilestation>
Date:   Mon, 20 Sep 2021 18:06:51 +0300
From:   Serge Semin <fancer.lancer@...il.com>
To:     Apurva Nandan <a-nandan@...com>
Cc:     Miquel Raynal <miquel.raynal@...tlin.com>,
        Richard Weinberger <richard@....at>,
        Vignesh Raghavendra <vigneshr@...com>,
        Rob Herring <robh+dt@...nel.org>,
        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

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.
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?

> +
> +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.

-Sergey

> +
> +examples:
> +  - |
> +    spi {
> +        #address-cells = <1>;
> +        #size-cells = <0>;
> +
> +        flash@6 {
> +            #address-cells = <1>;
> +            #size-cells = <1>;
> +            compatible = "spi-nand";
> +            reg = <0x6>;
> +            spi-max-frequency = <42000000>;
> +
> +            partitions {
> +                compatible = "fixed-partitions";
> +                #address-cells = <1>;
> +                #size-cells = <1>;
> +
> +                partition@0 {
> +                    label = "boot";
> +                    reg = <0 0x200000>;
> +                };
> +
> +                partition@...000 {
> +                    label = "rootfs";
> +                    reg = <0x200000 0xce0000>;
> +                };
> +            };
> +        };
> +    };
> -- 
> 2.25.1
>