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

On Tue, Apr 15, 2014 at 1:51 AM, Torsten Duwe <duwe@lst.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@lst.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@suse.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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