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From:   Loic Poulain <loic.poulain@linaro.org>
Date:   Fri, 16 Sep 2022 18:42:08 +0200
Message-ID: <CAMZdPi_+zQe41xSx+LHj_FDeHu7rs=TEgbWGBaMxcoSrOvXLRQ@mail.gmail.com>
Subject: Re: [PATCH v3 1/1] wcn36xx: Add RX frame SNR as a source of system entropy
To:     "Bryan O'Donoghue" <bryan.odonoghue@linaro.org>
Cc:     "Jason A . Donenfeld" <Jason@zx2c4.com>, davem@davemloft.net,
        edumazet@google.com, kuba@kernel.org, kvalo@kernel.org,
        linux-wireless@vger.kernel.org, netdev@vger.kernel.org,
        pabeni@redhat.com, wcn36xx@lists.infradead.org
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On Thu, 15 Sept 2022 at 02:41, Bryan O'Donoghue <bryan.odonoghue@linaro.org>
wrote:
>
> The signal-to-noise-ratio SNR is returned by the wcn36xx firmware for each
> received frame. SNR represents all of the unwanted interference signal
> after filtering out the fundamental frequency and harmonics of the
> frequency.
>
> Noise can come from various electromagnetic sources, from temperature
> affecting the performance hardware components or quantization effects
> converting from analog to digital domains.
>
> The SNR value returned by the WiFi firmware then is a good source of
> entropy.
>
> Other WiFi drivers offer up the noise component of the FFT as an entropy
> source for the random pool e.g.
>
> commit 2aa56cca3571 ("ath9k: Mix the received FFT bins to the random
pool")
>
> I attended Jason's talk on sources of randomness at Plumbers and it
> occurred to me that SNR is a reasonable candidate to add.
>
> Cc: Jason A. Donenfeld <Jason@zx2c4.com>
> Signed-off-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>

Acked-by: Loic Poulain <loic.poulain@linaro.org>