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Subject: Re: another testmgr question
To:     Ard Biesheuvel <ard.biesheuvel@linaro.org>,
        Pascal Van Leeuwen <pvanleeuwen@insidesecure.com>
Cc:     Eric Biggers <ebiggers@kernel.org>,
        "linux-crypto@vger.kernel.org" <linux-crypto@vger.kernel.org>
From:   Kamil Konieczny <k.konieczny@partner.samsung.com>
Message-ID: <bbf4749b-9f7c-90d3-9adc-72e96467d0c4@partner.samsung.com>
Date:   Fri, 24 May 2019 09:04:00 +0200
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On 24.05.2019 07:24, Ard Biesheuvel wrote:
> On Thu, 23 May 2019 at 22:44, Pascal Van Leeuwen
> <pvanleeuwen@insidesecure.com> wrote:
>>
> [...]
> In fact, given the above, I am slightly shocked that your hardware
> does not handle empty messages correctly. [...]

Imho hardware handles it in the way it was designed, for Exynos
writing non-zero value to len message register starts hash/hmac.
Writing zero and waiting for result will cause hang, as there will be
no result ever.
It can be done in HW to handle zero with additional register and more wires,
but it was left to software driver as trivial case.

-- 
Best regards,
Kamil Konieczny
Samsung R&D Institute Poland