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From:   Stephan Mueller <smueller@chronox.de>
To:     Richard Weinberger <richard@nod.at>
Cc:     david <david@sigma-star.at>,
        Linux Crypto Mailing List <linux-crypto@vger.kernel.org>,
        linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: Can an ahash driver be used through shash API?
Date:   Thu, 30 May 2019 07:38:17 +0200
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Am Mittwoch, 29. Mai 2019, 22:21:50 CEST schrieb Richard Weinberger:

Hi Richard,

> Stephan,
>=20
> ----- Urspr=FCngliche Mail -----
>=20
> >> I've seen that it does actually work the other way around, since
> >> crypto_init_shash_ops_async() in crypto/shash.c takes care of translat=
ing
> >> calls from ahash to shash and that's how the *-generic drivers are usa=
ble
> >> through the ahash API.
> >=20
> > The crypto_alloc_shash will only identify cipher implementations that w=
ere
> > registered with the CRYPTO_ALG_TYPE_SHASH flag. That flag is set when a
> > cipher is registered using crypto_register_shash.
> >=20
> > Thus, ciphers registered with crypto_register_ahash will not bear this
> > flag
> > and thus will not be found by the allocation function.
>=20
> is there a reason why we don't emulate the synchronous functionality
> in the crypto API layer if a driver implements only the async interface?
>=20
> Or is it just a matter of -ENOPATCH? :)

How can that be done in the first place? SHASH is intended and is used with=
=20
stack variables. An AHASH will have to be expected to sleep inbetween. Thus=
,=20
it cannot be used as SHASH.

Ciao
Stephan