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References: <20230214080034.3828-1-marcan@marcan.st> <20230214080034.3828-3-marcan@marcan.st>
In-Reply-To: <20230214080034.3828-3-marcan@marcan.st>
From:   Julian Calaby <julian.calaby@gmail.com>
Date:   Tue, 14 Feb 2023 20:00:45 +1100
Message-ID: <CAGRGNgV6YMhBa1bdkf_EQ0Z+nwbfhJkKcTxtc=ukWVMWtvQ2PA@mail.gmail.com>
Subject: Re: [PATCH 2/2] brcmfmac: pcie: Provide a buffer of random bytes to
 the device
To:     Arend van Spriel <aspriel@gmail.com>
Cc:     Hector Martin <marcan@marcan.st>,
        Franky Lin <franky.lin@broadcom.com>,
        Hante Meuleman <hante.meuleman@broadcom.com>,
        Kalle Valo <kvalo@kernel.org>,
        "David S. Miller" <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>,
        Sven Peter <sven@svenpeter.dev>,
        Alyssa Rosenzweig <alyssa@rosenzweig.io>,
        Linus Walleij <linus.walleij@linaro.org>,
        asahi@lists.linux.dev, linux-wireless@vger.kernel.org,
        brcm80211-dev-list.pdl@broadcom.com,
        SHA-cyfmac-dev-list@infineon.com, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org
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Hi Arend,

On Tue, Feb 14, 2023 at 7:04 PM Hector Martin <marcan@marcan.st> wrote:
>
> Newer Apple firmwares on chipsets without a hardware RNG require the
> host to provide a buffer of 256 random bytes to the device on
> initialization. This buffer is present immediately before NVRAM,
> suffixed by a footer containing a magic number and the buffer length.
>
> This won't affect chips/firmwares that do not use this feature, so do it
> unconditionally for all Apple platforms (those with an Apple OTP).

Following on from the conversation a year ago, is there a way to
detect chipsets that need these random bytes? While I'm sure Apple is
doing their own special thing for special Apple reasons, it seems
relatively sensible to omit a RNG on lower-cost chipsets, so would
other chipsets need it?

> Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
> Signed-off-by: Hector Martin <marcan@marcan.st>

Beyond that, it all seems pretty sensible.

Reviewed-by: Julian Calaby <julian.calaby@gmail.com>

> ---
>  .../broadcom/brcm80211/brcmfmac/pcie.c        | 32 +++++++++++++++++++
>  1 file changed, 32 insertions(+)

Thanks,

-- 
Julian Calaby

Email: julian.calaby@gmail.com
Profile: http://www.google.com/profiles/julian.calaby/