linux-kernel - Re: [PATCH v2 1/3] dt-bindings: reserved-memory: ramoops: Update the binding

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Date:   Fri, 13 Jan 2023 13:04:59 +0100
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Mukesh Ojha <quic_mojha@...cinc.com>, keescook@...omium.org,
        gpiccoli@...lia.com, corbet@....net, tony.luck@...el.com,
        robh+dt@...nel.org, krzysztof.kozlowski+dt@...aro.org
Cc:     linux-hardening@...r.kernel.org, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [PATCH v2 1/3] dt-bindings: reserved-memory: ramoops: Update the
 binding

Subject: drop second/last, redundant "binding". The "dt-bindings" prefix
is already stating that these are bindings.

Your subject says nothing. Everything is "update".

On 13/01/2023 12:58, Mukesh Ojha wrote:
> Update the ramoops region binding document with details
> like region can also be reserved dynamically apart from
> reserving it statically.

So what exactly can be here reserved dynamically? And what does it mean
'dynamically'? By whom? How is this property of hardware (not OS)?

> 
> Signed-off-by: Mukesh Ojha <quic_mojha@...cinc.com>
> ---
> Change in v2:
>   - Added this patch as per changes going to be done in patch 3/3
> 
>  .../bindings/reserved-memory/ramoops.yaml          | 34 ++++++++++++++++++++--
>  1 file changed, 32 insertions(+), 2 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/reserved-memory/ramoops.yaml b/Documentation/devicetree/bindings/reserved-memory/ramoops.yaml
> index 0391871..54e46e8 100644
> --- a/Documentation/devicetree/bindings/reserved-memory/ramoops.yaml
> +++ b/Documentation/devicetree/bindings/reserved-memory/ramoops.yaml
> @@ -10,7 +10,8 @@ description: |
>    ramoops provides persistent RAM storage for oops and panics, so they can be
>    recovered after a reboot. This is a child-node of "/reserved-memory", and
>    is named "ramoops" after the backend, rather than "pstore" which is the
> -  subsystem.
> +  subsystem. This region can be reserved both statically or dynamically by
> +  using appropriate property in device tree.
>  
>    Parts of this storage may be set aside for other persistent log buffers, such
>    as kernel log messages, or for optional ECC error-correction data.  The total
> @@ -112,7 +113,13 @@ unevaluatedProperties: false
>  
>  required:
>    - compatible
> -  - reg
> +
> +oneOf:
> +  - required:
> +      - reg
> +
> +  - required:
> +      - size

There is no such property. You cannot require it.

>  
>  anyOf:
>    - required: [record-size]
> @@ -142,3 +149,26 @@ examples:
>              };
>          };
>      };
> +
> +  - |
> +    / {
> +        compatible = "foo";
> +        model = "foo";
> +        #address-cells = <2>;
> +        #size-cells = <2>;
> +
> +        reserved-memory {
> +            #address-cells = <2>;
> +            #size-cells = <2>;
> +            ranges;
> +
> +            ramoops: ramoops_region {

Node names should be generic, no underscores in node names.
https://devicetree-specification.readthedocs.io/en/latest/chapter2-devicetree-basics.html#generic-names-recommendation

Any reason in naming it differently then existing one? You have there
example.

> +                compatible = "ramoops";
> +                alloc-ranges = <0x0 0x00000000 0xffffffff 0xffffffff>;
> +                size = <0x0 0x10000>;       /* 64kB */
> +                console-size = <0x8000>;    /* 32kB */
> +                record-size = <0x400>;      /*  1kB */
> +                ecc-size = <16>;
> +            };
> +        };
> +    };

Best regards,
Krzysztof