linux-kernel - Re: [PATCH v3 03/03]: hwrng: khwrngd derating per device

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Message-ID: <CALCETrXrHOJkEvYv8VGaNNJSFarAaD7E7G7myOvWo5SG4m4qKg@mail.gmail.com>
Date:	Tue, 15 Apr 2014 09:53:53 -0700
From:	Andy Lutomirski <luto@...capital.net>
To:	Torsten Duwe <duwe@....de>
Cc:	"H. Peter Anvin" <hpa@...or.com>, "Theodore Ts'o" <tytso@....edu>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Matt Mackall <mpm@...enic.com>,
	Herbert Xu <herbert@...dor.apana.org.au>,
	Arnd Bergmann <arnd@...db.de>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Satoru Takeuchi <satoru.takeuchi@...il.com>,
	ingo.tuchscherer@...ibm.com,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Hans-Georg Markgraf <MGRF@...ibm.com>,
	Gerald Schaefer <gerald.schaefer@...ibm.com>,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	Heiko Carstens <heiko.carstens@...ibm.com>,
	Joe Perches <joe@...ches.com>
Subject: Re: [PATCH v3 03/03]: hwrng: khwrngd derating per device

On Tue, Apr 15, 2014 at 1:51 AM, Torsten Duwe <duwe@....de> wrote:
> On Mon, Apr 14, 2014 at 09:41:10AM -0700, Andy Lutomirski wrote:
>> On Mon, Apr 14, 2014 at 9:06 AM, Torsten Duwe <duwe@....de> wrote:
>> >
>> > This patch introduces a derating factor to struct hwrng for
>> > the random bits going into the kernel input pool, and a common
>> > default derating for drivers which do not specify one.
>> >
>> > Signed-off-by: Torsten Duwe <duwe@...e.de>
>> >
>> > ---
>> >  drivers/char/hw_random/core.c |   11 ++++++++++-
>> >  include/linux/hw_random.h     |    3 +++
>> >  2 files changed, 13 insertions(+), 1 deletion(-)
>> >
>> > --- linux/include/linux/hw_random.h.orig
>> > +++ linux/include/linux/hw_random.h
>> > @@ -29,6 +29,8 @@
>> >   * @read:              New API. drivers can fill up to max bytes of data
>> >   *                     into the buffer. The buffer is aligned for any type.
>> >   * @priv:              Private data, for use by the RNG driver.
>> > + * @derating:          Estimation of true entropy in RNG's bitstream
>> > + *                     (per mill).
>>
>> I'll bikeshed again: this is a rating, not a *de*rating.  Higher =
>> more confidence, at least assuming the comment is right.
>>
> You're right. Would anyone object to call it "quality", as in RX signal quality?
> In context of a random source that is pretty accurate, I'd say. Other opinions?

I'm okay with "quality", although I'm still partial to "entropy_per_1000bits".

--Andy
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