linux-kernel - Re: Can an ahash driver be used through shash API?

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Date:   Wed, 29 May 2019 22:21:50 +0200 (CEST)
From:   Richard Weinberger <richard@....at>
To:     Stephan Mueller <smueller@...onox.de>
Cc:     david <david@...ma-star.at>,
        Linux Crypto Mailing List <linux-crypto@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: Can an ahash driver be used through shash API?

Stephan,

----- Ursprüngliche Mail -----
>> 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 translating
>> calls from ahash to shash and that's how the *-generic drivers are usable
>> through the ahash API.
> 
> The crypto_alloc_shash will only identify cipher implementations that were
> registered with the CRYPTO_ALG_TYPE_SHASH flag. That flag is set when a cipher
> is registered using crypto_register_shash.
> 
> Thus, ciphers registered with crypto_register_ahash will not bear this flag
> and thus will not be found by the allocation function.

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?

Or is it just a matter of -ENOPATCH? :)

Thanks,
//richard