From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-1.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id E64BBC433DF for ; Wed, 20 May 2020 12:00:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C5106207D4 for ; Wed, 20 May 2020 12:00:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1589976016; bh=p2b++fqgB3j8t8wQVCowLSphUGbZ0n9M7PbJlfK7X/g=; h=References:In-Reply-To:From:Date:Subject:To:Cc:List-ID:From; b=qJIz0YKhVXQP/eFRKFllSwvALeSnHywze9e0kTDAyf/KqbZqMtJ8WHKh2ey/7b47Q NGzWCusHdYW5ZKHjDAJs7+PdkPoVxLibPqGCIPlezCumI69ppTm98KtJTluK1yepNo 4gDcHze9+VivF1JLyCSYv4hxcjy85ugHHfY+DTb4= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726851AbgETMAQ (ORCPT ); Wed, 20 May 2020 08:00:16 -0400 Received: from mail.kernel.org ([198.145.29.99]:50286 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726435AbgETMAP (ORCPT ); Wed, 20 May 2020 08:00:15 -0400 Received: from mail-lj1-f172.google.com (mail-lj1-f172.google.com [209.85.208.172]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id DD4F02088E; Wed, 20 May 2020 12:00:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1589976015; bh=p2b++fqgB3j8t8wQVCowLSphUGbZ0n9M7PbJlfK7X/g=; h=References:In-Reply-To:From:Date:Subject:To:Cc:From; b=CW5CxvEsFMAQykySax7pzLLLsuOOb0yHjoog78dUyoDsiNZGpdB8q/hjeryKbCcTP wIa4BnzHQws04aAqGlgPIA8bdvGr19unsaZtfbi4gLUwlMH2JvsZcNiutZfHgBEWvk gebWAQM0XpcbGPvbaAEOxAJQZtXaojp57sWXGDvY= Received: by mail-lj1-f172.google.com with SMTP id v16so3323685ljc.8; Wed, 20 May 2020 05:00:14 -0700 (PDT) X-Gm-Message-State: AOAM532eYYX0uWOGVm2+oU5QjmU2qUG2wfhKSV4RaFm4Om1FVb9OJaDj g4sPXTOz1bX3mbmanQWvemVWQGxJUWgnKudqtT8= X-Google-Smtp-Source: ABdhPJzqow3O8ENCEDm8pm97wOipgg7aCLHp2fW6FeVlcUNXw9PQ19agZuUv9OGshUKmBWlDt+HIDjaQRQTcXVnWHKU= X-Received: by 2002:a2e:8e99:: with SMTP id z25mr2440347ljk.142.1589976012909; Wed, 20 May 2020 05:00:12 -0700 (PDT) MIME-Version: 1.0 References: <15745285.MnsZKaK4VV@tauon.chronox.de> <2041475.ybOAuNAZB8@tauon.chronox.de> In-Reply-To: <2041475.ybOAuNAZB8@tauon.chronox.de> From: Krzysztof Kozlowski Date: Wed, 20 May 2020 14:00:01 +0200 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v2 1/2] hwrng: iproc-rng200 - Set the quality value To: Stephan Mueller Cc: Lukasz Stelmach , Matt Mackall , Herbert Xu , Arnd Bergmann , Greg Kroah-Hartman , Ray Jui , Scott Branden , bcm-kernel-feedback-list@broadcom.com, Kukjin Kim , Florian Fainelli , Markus Elfring , Matthias Brugger , Stefan Wahren , linux-crypto@vger.kernel.org, linux-arm-kernel@lists.infradead.org, "linux-kernel@vger.kernel.org" , "linux-samsung-soc@vger.kernel.org" , Bartlomiej Zolnierkiewicz Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 20 May 2020 at 13:53, Stephan Mueller wrote: > > > That said, the illustrated example is typical for hardware RNGs. Yet > > > it is never guaranteed to work that way. Thus, if you can point to > > > architecture documentation of your specific hardware RNGs showing that > > > the data read from the hardware is pure unconditioned noise data, then > > > I have no objections to the patch. > > > > I can tell for sure that this is the case for exynos-trng[1]. > > So you are saying that the output for the exynos-trng is straight from a ring > oscillator without any post-processing of any kind? Hi, I think we will never be able to state this because the manual is quite limited in sharing internals. What the driver does and probably Lukasz wanted to say is that there is "post processing" block and feature which can be disabled. The manual is saying the TRNG block generates random data from thermal noise but not how much in a direct way. There could be some simple post-processing or not (except the one able to on/off). Also manual says this post processing block is there to remove statistical weakness from the TRNG block. To me it does not prove enough that raw data is really raw... Best regards, Krzysztof