linux-kernel - Re: [PATCH] Documentation: dt-bindings: Document 'rng-seed' for /chosen

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Date:   Thu, 2 Apr 2020 09:13:47 +0100
From:   Will Deacon <will@...nel.org>
To:     Florian Fainelli <f.fainelli@...il.com>
Cc:     linux-kernel@...r.kernel.org, hsinyi@...omium.org,
        geert+renesas@...der.be, swboyd@...omium.org, robh@...nel.org,
        tytso@....edu
Subject: Re: [PATCH] Documentation: dt-bindings: Document 'rng-seed' for
 /chosen

Hi Florian,

On Wed, Apr 01, 2020 at 08:36:40PM -0700, Florian Fainelli wrote:
> The /chosen node can have a 'rng-seed' property read as a u32 quantity
> which would contain a random number provided by the boot agent. This is
> useful in configurations where the kernel does not have access to a
> random number generator.
> 
> Signed-off-by: Florian Fainelli <f.fainelli@...il.com>
> ---
>  Documentation/devicetree/bindings/chosen.txt | 13 +++++++++++++
>  1 file changed, 13 insertions(+)

Thanks for doing this; I realised it was undocumented the other day when I
tried to look it up myself.

> diff --git a/Documentation/devicetree/bindings/chosen.txt b/Documentation/devicetree/bindings/chosen.txt
> index 45e79172a646..126b31eecfeb 100644
> --- a/Documentation/devicetree/bindings/chosen.txt
> +++ b/Documentation/devicetree/bindings/chosen.txt
> @@ -28,6 +28,19 @@ mode) when EFI_RNG_PROTOCOL is supported, it will be overwritten by
>  the Linux EFI stub (which will populate the property itself, using
>  EFI_RNG_PROTOCOL).
>  
> +rng-seed
> +--------
> +
> +This property is used to initialize the kernel's entropy pool from a
> +trusted boot agent capable of providing a random number. It is parsed
> +as a u32 value, e.g.

Are you sure about this being limited to a u32 value? I thought you could
pass an arbitrary-length value here.

Will