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Subject: Re: another testmgr question
To:     Pascal Van Leeuwen <pvanleeuwen@insidesecure.com>
Cc:     Eric Biggers <ebiggers@kernel.org>,
        "linux-crypto@vger.kernel.org" <linux-crypto@vger.kernel.org>
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From:   Christophe Leroy <christophe.leroy@c-s.fr>
Message-ID: <6e5a9618-fc54-f649-6ca3-5c8ced027630@c-s.fr>
Date:   Fri, 24 May 2019 08:21:05 +0200
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Hi Pascal,

Le 23/05/2019 à 23:43, Pascal Van Leeuwen a écrit :
>> -----Original Message-----
>> From: Eric Biggers [mailto:ebiggers@kernel.org]

[...]

>> Note that it's not necessary that your *hardware* supports empty messages,
>> since you can simply do this in the driver instead:
>>
>>        if (req->cryptlen == 0)
>>                return 0;
>>
> For skciphers, yes, it's not such a problem. Neither for basic hash.
> (And thanks for the code suggestion BTW, this will be a lot more efficient
> then what I'm doing now for this particular case :-)
> For HMAC, however, where you would have to return a value depending on the
> key ... not so easy to solve. I don't have a solution for that yet :-(

I had the same issue when porting the SEC2 Talitos driver to also 
support SEC1. See following commit to see the way it has been fixed:

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=2d02905ebd22c0271a25e424ab209c8b7067be67

Christophe

> 
> And I'm pretty sure this affects all Inside Secure HW drivers in the tree:
> inside-secure, amcc, mediatek and omap ...
> 
> Regards,
> Pascal van Leeuwen
> Silicon IP Architect, Multi-Protocol Engines, Inside Secure
> www.insidesecure.com
>