linux-kernel - Re: [PATCH 1/6] dt-bindings: nvmem: Add bindings for rmem driver

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Date:   Tue, 15 Dec 2020 14:25:34 -0600
From:   Rob Herring <robh+dt@...nel.org>
To:     Nicolas Saenz Julienne <nsaenzjulienne@...e.de>
Cc:     Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
        devicetree@...r.kernel.org,
        "maintainer:BROADCOM BCM7XXX ARM ARCHITECTURE" 
        <bcm-kernel-feedback-list@...adcom.com>,
        "moderated list:BROADCOM BCM2835 ARM ARCHITECTURE" 
        <linux-rpi-kernel@...ts.infradead.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Russell King <linux@...linux.org.uk>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Tim Gover <tim.gover@...pberrypi.com>,
        Phil Elwell <phil@...pberrypi.com>
Subject: Re: [PATCH 1/6] dt-bindings: nvmem: Add bindings for rmem driver

On Tue, Dec 15, 2020 at 9:56 AM Nicolas Saenz Julienne
<nsaenzjulienne@...e.de> wrote:
>
> Firmware/co-processors might use reserved memory areas in order to pass
> data stemming from an nvmem device otherwise non accessible to Linux.
> For example an EEPROM memory only physically accessible to firmware, or
> data only accessible early at boot time.
>
> Introduce the dt-bindings to nvmem's rmem.
>
> Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@...e.de>
> ---
>  .../devicetree/bindings/nvmem/rmem.yaml       | 35 +++++++++++++++++++
>  1 file changed, 35 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/nvmem/rmem.yaml
>
> diff --git a/Documentation/devicetree/bindings/nvmem/rmem.yaml b/Documentation/devicetree/bindings/nvmem/rmem.yaml
> new file mode 100644
> index 000000000000..3037ebc4634d
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/nvmem/rmem.yaml
> @@ -0,0 +1,35 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/nvmem/rmem.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Reserved Memory Based nvmem Device
> +
> +maintainers:
> +  - Nicolas Saenz Julienne <nsaenzjulienne@...e.de>
> +
> +properties:
> +  compatible:
> +    enum:
> +      - nvmem-rmem
> +
> +  memory-region:
> +    $ref: /schemas/types.yaml#/definitions/phandle
> +    description:
> +      phandle to the reserved memory region

There's no need for this indirection. Just add a compatible to the
reserved-memory node. See ramoops for example.

Please make the compatible specific enough to define what the memory
contains. If you want 'nvmem-rmem' as a fallback that's fine.

> +
> +required:
> +  - compatible
> +  - memory-region
> +
> +additionalProperties: false
> +
> +examples:
> +  - |
> +        fw-config {
> +                compatible = "nvmem-rmem";
> +                memory-region = <&mem>;
> +        };
> +
> +...
> --
> 2.29.2
>