linux-kernel - Re: [PATCH V2 2/3] dt-bindings: nvmem: add U-Boot environment variables binding

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Message-ID: <YdyXdrgh7+I2CaX6@robh.at.kernel.org>
Date:   Mon, 10 Jan 2022 14:30:46 -0600
From:   Rob Herring <robh@...nel.org>
To:     Rafał Miłecki <zajec5@...il.com>
Cc:     Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
        Miquel Raynal <miquel.raynal@...tlin.com>,
        Richard Weinberger <richard@....at>,
        Vignesh Raghavendra <vigneshr@...com>,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mtd@...ts.infradead.org,
        Rafał Miłecki <rafal@...ecki.pl>
Subject: Re: [PATCH V2 2/3] dt-bindings: nvmem: add U-Boot environment
 variables binding

On Thu, Dec 30, 2021 at 10:04:48AM +0100, Rafał Miłecki wrote:
> From: Rafał Miłecki <rafal@...ecki.pl>
> 
> This binding allows describing a (part of) MTD device (partition) that
> contains a block with environment variables. Operating system usually
> needs to parse that block to read variables values that may affect
> booting process & device configuration.

What do the u-boot folks think about this binding? This needs an ack 
from a u-boot maintainer.

> 
> Signed-off-by: Rafał Miłecki <rafal@...ecki.pl>
> ---
> V2: s/u,boot/u-boot/
> ---
>  .../devicetree/bindings/nvmem/u-boot,env.yaml | 56 +++++++++++++++++++
>  MAINTAINERS                                   |  5 ++
>  2 files changed, 61 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/nvmem/u-boot,env.yaml
> 
> diff --git a/Documentation/devicetree/bindings/nvmem/u-boot,env.yaml b/Documentation/devicetree/bindings/nvmem/u-boot,env.yaml
> new file mode 100644
> index 000000000000..e3296e005ffd
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/nvmem/u-boot,env.yaml
> @@ -0,0 +1,56 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/nvmem/u-boot,env.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: U-Boot environment variables
> +
> +description: |
> +  U-Boot uses environment variables to store device parameters and
> +  configuration. They may be used for booting process, setup or keeping end user
> +  interesting info.
> +
> +  Data is stored on flash partition in a U-Boot specific format (CRC32 and NUL
> +  separated key-value pairs).
> +
> +  This binding allows specifying data location and format (default one or vendor
> +  specific).
> +
> +maintainers:
> +  - Rafał Miłecki <rafal@...ecki.pl>
> +
> +allOf:
> +  - $ref: nvmem.yaml#
> +
> +properties:
> +  compatible:
> +    enum:
> +      - u-boot,env
> +      - brcm,env
> +
> +  reg:
> +    maxItems: 1
> +
> +unevaluatedProperties: false
> +
> +examples:
> +  - |
> +    partitions {
> +        compatible = "fixed-partitions";
> +        #address-cells = <1>;
> +        #size-cells = <1>;
> +
> +        partition@0 {
> +            label = "uboot";
> +            reg = <0x0 0x100000>;
> +
> +            #address-cells = <1>;
> +            #size-cells = <1>;
> +
> +            nvmem@...00 {

I think most existing cases define a partition for the u-boot env, but 
this looks like you have it nested with other u-boot related data? Is 
there any reason to nest the partitions? A compatible in a partition 
node should be enough.

> +                compatible = "u-boot,env";
> +                reg = <0x10000 0x10000>;
> +            };
> +        };
> +    };
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 67558097bb66..271c29c84c7d 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -19624,6 +19624,11 @@ W:	http://linuxtv.org
>  T:	git git://linuxtv.org/media_tree.git
>  F:	drivers/media/pci/tw686x/
>  
> +U-BOOT ENVIRONMENT VARIABLES
> +M:	Rafał Miłecki <rafal@...ecki.pl>
> +S:	Maintained
> +F:	Documentation/devicetree/bindings/nvmem/u-boot,env.yaml
> +
>  UACCE ACCELERATOR FRAMEWORK
>  M:	Zhangfei Gao <zhangfei.gao@...aro.org>
>  M:	Zhou Wang <wangzhou1@...ilicon.com>
> -- 
> 2.31.1
> 
>