Re: [PATCH v2] RANDOM: ATH9K RNG delivers zero bits of entropy

Hi Stephan,

On Mon, Aug 08, 2016 at 05:29:30PM +0000, Jason Cooper wrote:

On Mon, Aug 08, 2016 at 08:41:36AM +0200, Stephan Mueller wrote:

...

quoted

If you think that this patch is a challenge because your driver starts to 
spin, please help and offer another solution.

Well, I don't buy the reasoning listed above for not using the hwrng
framework.  Interrupt timings were never designed to be a source of entropy
either.  We need to grab it where ever we can find it, especially on
embedded systems.  Documentation/hw_random.txt even says:

"""
This data is NOT CHECKED by any fitness tests, and could potentially be
bogus (if the hardware is faulty or has been tampered with).
"""

I really don't think there's a problem with adding these sorts of
sources under char/hw_random/.  I think the only thing we would be
concerned about, other than the already addressed entropy estimation,
would be constraining the data rate.

Further research yields char/hw_random/timeriomem-rng.c

It could use an update to ->read() vice data_{present,read}(), but it's
functionally exactly what the ath9k rng is doing. :)

thx,

Jason.