linux-kernel - Re: [PATCH 3/3] hwrng: msm

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Date:   Wed, 20 Jun 2018 23:15:12 +0530
From:   PrasannaKumar Muralidharan <prasannatsmkumar@...il.com>
To:     Vinod <vkoul@...nel.org>
Cc:     Herbert Xu <herbert@...dor.apana.org.au>,
        "open list:HARDWARE RANDOM NUMBER GENERATOR CORE" 
        <linux-crypto@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>,
        Matt Mackall <mpm@...enic.com>, Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-arm-msm@...r.kernel.org
Subject: Re: [PATCH 3/3] hwrng: msm - Add support for prng v2

Hi Vinod,

On 20 June 2018 at 11:02, Vinod <vkoul@...nel.org> wrote:
> On 19-06-18, 22:28, Herbert Xu wrote:
>> On Mon, Jun 18, 2018 at 07:42:59PM +0530, Vinod Koul wrote:
>> > Qcom 8996 and later chips support prng v2 where we need to only
>> > implement .read callback for hwrng.
>> >
>> > Add a new table for v2 which supports this and get version required for
>> > driver data.
>> >
>> > Signed-off-by: Vinod Koul <vkoul@...nel.org>
>>
>> Is this really a pseudo-RNG? If so it needs to be moved over to
>> the algif_rng interface.
>>
>> hwrng is for true hardware RNGs only, because it may be directly
>> fed into /dev/random.
>
> I am trying to find how how much random output this hardware generates.
>
> Meanwhile, can you please point out examples/Documentation for algif_rng
> and if any test tools for this?

As Herbert suggested exynos rng is a good example. It was wrongly
using hwrng framework then switched to using crypto framework.

I have a patch for msm rng using crypto framework, only compile tested
though. You can find the patch at
https://pastebin.ubuntu.com/p/44r6BJgBkN/. I am having a hard time
sending patches via git send-email form a gmail account so I have put
it in pastebin. Feel free to use it if that is useful.

Regards,
PrasannaKumar