Messages in this thread |  | | Subject | Re: [PATCH] Documentation: dt-bindings: Document 'rng-seed' for /chosen | From | Florian Fainelli <> | Date | Thu, 2 Apr 2020 11:07:08 -0700 |
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On 4/2/2020 1:13 AM, Will Deacon wrote: > 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@gmail.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.
Humm indeed, we can pass an arbitrary value, I completely conflated the type of "l" here:
int l; ... rng_seed = of_get_flat_dt_prop(node, "rng-seed", &l);
with how much we would be reading from the property, which is complete nonsense. Out of curiosity, what property length do platforms typically populate? -- Florian
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