linux-kernel - Re: [PATCH 09/11] crypto: remove LZO fallback from crypto 842

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Date:	Wed, 8 Apr 2015 10:45:45 -0400
From:	Dan Streetman <ddstreet@...e.org>
To:	Herbert Xu <herbert@...dor.apana.org.au>
Cc:	"David S. Miller" <davem@...emloft.net>,
	Michael Ellerman <mpe@...erman.id.au>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Paul Mackerras <paulus@...ba.org>,
	Seth Jennings <sjennings@...iantweb.net>,
	Robert Jennings <rob@...hix.net>, linux-crypto@...r.kernel.org,
	"linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 09/11] crypto: remove LZO fallback from crypto 842

On Wed, Apr 8, 2015 at 10:38 AM, Herbert Xu <herbert@...dor.apana.org.au> wrote:
> On Wed, Apr 08, 2015 at 10:28:23AM -0400, Dan Streetman wrote:
>>
>> So, the sw implementation is only for decompression; there's no sw
>> compression implementation in these patches.
>
> As a general rule we don't add any hardware implementation unless
> there is a software implementation.  The reason is that every new
> algorithm creates an API (potentially a user-space API if the
> algorithm can be exported via algif).  But sometimes things slip
> through.
>
> So I'm not going to immediately remove 842 but it would be nice
> if we had a reference implementation so that if ever there were
> another hardware 842 implmentation added then at least we have
> something that we can judge against.

Ok I'll see if I can include a sw compression implementation.

>
>> The hw 842 driver is currently at drivers/crypto/nx, and the
>> crypto/842 driver just calls the hw driver (after correctly
>> aligning/sizing the provided buffers to what the hw driver expects),
>> and falls back to the sw decompression if the hw decompression fails
>> (there is no compression fallback, a failure is reported to the
>> caller).
>>
>> Is that setup ok?  If users had to directly call the hw driver,
>> instead of using the generic crypto_comp interface, it would
>> complicate things, e.g. in zswap it only expects to call
>> crypto_comp_compress()/decompress(), not call the 842 hw driver
>> directly.
>
> I think the only thing that needs to happen for now is moving
> crypto/842.c over to drivers/crypto/nx (perhaps merge it into
> nx-842.c) so that it's obvious that this is not a generic
> implementation.

ah ok, so you mean it can still be a crypto_comp interface, just move
its location and/or merge it into nx-842.c?

>
> Cheers,
> --
> Email: Herbert Xu <herbert@...dor.apana.org.au>
> Home Page: http://gondor.apana.org.au/~herbert/
> PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
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