From: Corentin Labbe Subject: Re: [PATCH] crypto: sun4i-ss: support the Security System PRNG Date: Thu, 17 Nov 2016 09:07:48 +0100 Message-ID: <20161117080748.GB25394@Red> References: <1476794067-28563-1-git-send-email-clabbe.montjoie@gmail.com> <1722218.eZlGktOxfL@tauon.atsec.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: herbert@gondor.apana.org.au, davem@davemloft.net, maxime.ripard@free-electrons.com, wens@csie.org, linux-kernel@vger.kernel.org, linux-crypto@vger.kernel.org, linux-arm-kernel@lists.infradead.org To: Stephan Mueller Return-path: Received: from mail-wm0-f67.google.com ([74.125.82.67]:34717 "EHLO mail-wm0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750790AbcKQIHw (ORCPT ); Thu, 17 Nov 2016 03:07:52 -0500 Content-Disposition: inline In-Reply-To: <1722218.eZlGktOxfL@tauon.atsec.com> Sender: linux-crypto-owner@vger.kernel.org List-ID: On Tue, Oct 18, 2016 at 04:24:22PM +0200, Stephan Mueller wrote: > Am Dienstag, 18. Oktober 2016, 14:34:27 CEST schrieb Corentin Labbe: > > Hi Corentin, > > > diff --git a/drivers/crypto/sunxi-ss/sun4i-ss-hwrng.c > > b/drivers/crypto/sunxi-ss/sun4i-ss-hwrng.c new file mode 100644 > > index 0000000..95fadb7 > > --- /dev/null > > +++ b/drivers/crypto/sunxi-ss/sun4i-ss-hwrng.c > > @@ -0,0 +1,70 @@ > > +#include "sun4i-ss.h" > > + > > +static int sun4i_ss_hwrng_init(struct hwrng *hwrng) > > +{ > > + struct sun4i_ss_ctx *ss; > > + > > + ss = container_of(hwrng, struct sun4i_ss_ctx, hwrng); > > + get_random_bytes(ss->seed, SS_SEED_LEN); > > Is it wise to call get_random_bytes once in the init function and never > thereafter? > > This init function may be called during boot time of the kernel at which the > input_pool may not yet have received sufficient amounts of entropy. > > What about registering a callback with add_random_ready_callback and seed > again when sufficient entropy was collected? > Seed again, or just do not seed (and so return -EAGAIN for read() function) until ready_callback ? Thanks Corentin Labbe