From: =?iso-8859-2?Q?Horia_Geant=E3?= Subject: Re: [PATCH v1] crypto: caam - set hwrng quality level Date: Wed, 19 Jul 2017 16:53:21 +0000 Message-ID: References: <20170719074458.9247-1-o.rempel@pengutronix.de> <20170719163248.sn7mvnq2s3fm2hvh@pengutronix.de> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-2" Content-Transfer-Encoding: quoted-printable Cc: Oleksij Rempel , "kernel@pengutronix.de" , Dan Douglass , Herbert Xu , "David S. Miller" , "linux-crypto@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "Harald Freudenberger" , Martin Schwidefsky To: Oleksij Rempel Return-path: Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-crypto.vger.kernel.org On 7/19/2017 7:32 PM, Oleksij Rempel wrote:=0A= > On Wed, Jul 19, 2017 at 12:49:47PM +0000, Horia Geant=E3 wrote:=0A= >> On 7/19/2017 10:45 AM, Oleksij Rempel wrote:=0A= >>> According documentation, it is NIST certified TRNG.=0A= >>> So, set high quality to let the HWRNG framework automatically use it.= =0A= >>>=0A= >>> Signed-off-by: Oleksij Rempel =0A= >>> ---=0A= >>> drivers/crypto/caam/caamrng.c | 6 ++++++=0A= >>> 1 file changed, 6 insertions(+)=0A= >>>=0A= >>> diff --git a/drivers/crypto/caam/caamrng.c b/drivers/crypto/caam/caamrn= g.c=0A= >>> index 41398da3edf4..684c0bc88dfd 100644=0A= >>> --- a/drivers/crypto/caam/caamrng.c=0A= >>> +++ b/drivers/crypto/caam/caamrng.c=0A= >>> @@ -292,10 +292,16 @@ static int caam_init_rng(struct caam_rng_ctx *ctx= , struct device *jrdev)=0A= >>> return 0;=0A= >>> }=0A= >>> =0A= >>> +/*=0A= >>> + * hwrng register struct=0A= >>> + * The trng is suppost to have 100% entropy, and thus=0A= >>> + * we register with a very high quality value.=0A= >>> + */=0A= >>> static struct hwrng caam_rng =3D {=0A= >>> .name =3D "rng-caam",=0A= >>> .cleanup =3D caam_cleanup,=0A= >>> .read =3D caam_read,=0A= >>> + .quality =3D 999,=0A= >>=0A= >> Why not 1024, i.e. where is 999 coming from?=0A= > =0A= > It comes from s390-trng.c driver.=0A= > Should I use 1024 instead?=0A= > =0A= AFAICT the range for quality is from 0 to 1024 (no entropy -> perfect=0A= entropy).=0A= =0A= 1024 should be used since I'd expect a HW TRNG to provide perfect=0A= entropy unless otherwise stated.=0A= =0A= [Cc-ing Harald and Martin for awareness wrt. s390/trng.]=0A= =0A= Thanks,=0A= Horia=0A=