linux-kernel - Re: [PATCH] crypto: sun4i-ss: support the Security System PRNG

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Date:   Fri, 18 Nov 2016 08:55:04 +0100
From:   Corentin Labbe <clabbe.montjoie@...il.com>
To:     Sandy Harris <sandyinchina@...il.com>
Cc:     Herbert Xu <herbert@...dor.apana.org.au>,
        "David S. Miller" <davem@...emloft.net>,
        maxime.ripard@...e-electrons.com, wens@...e.org,
        LKML <linux-kernel@...r.kernel.org>,
        linux-crypto@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] crypto: sun4i-ss: support the Security System PRNG

On Thu, Nov 17, 2016 at 08:07:09PM -0500, Sandy Harris wrote:
> Add Ted T'so to cc list. Shouldn't he be included on anything affecting
> the random(4) driver?
> 

Blindy used get_maintainer.pl, and since the file is in crypto, hw_random people were not set.
Note that get_maintainer.pl on drivers/char/hw_random/, does not give his address also.
My V2 patch will have them in CC/TO.

> On Tue, Oct 18, 2016 at 8:34 AM, Corentin Labbe
> <clabbe.montjoie@...il.com> wrote:
> 
> > From: LABBE Corentin <clabbe.montjoie@...il.com>
> >
> > The Security System have a PRNG.
> > This patch add support for it as an hwrng.
> 
> Which is it? A PRNG & a HW RNG are quite different things.
> It would, in general, be a fairly serious error to treat a PRNG
> as a HWRNG.
> 
> If it is just a prng (which it appears to be from a quick look
> at your code) then it is not clear it is useful since the
> random(4) driver already has two PRNGs. It might be
> but I cannot tell.

For me hwrng is a way to give user space an another way to get "random" data via /dev/hwrng.
The only impact of hwrng with random is that just after init some data of hwrng is used for having more entropy.

Grepping prng in drivers/char/hw_random/ and drivers/crypto show me some other PRNG used with hwrng.

Regards
Corentin Labbe