netdev - Re: IRQF_SAMPLE_RANDOM question...

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Date:	Thu, 9 Apr 2009 09:54:54 -0400
From:	Robin Getz <rgetz@...ckfin.uclinux.org>
To:	"Matt Mackall" <mpm@...enic.com>
CC:	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	"Chris Peterson" <cpeterso@...terso.com>
Subject: Re: IRQF_SAMPLE_RANDOM question...

On Wed 8 Apr 2009 15:51, Matt Mackall pondered:
> On Tue, 2009-04-07 at 17:44 -0400, Robin Getz wrote:
> > Is that "Everything in general, with a few exceptions", or
> > "__Everything__"?
> 
> Everything. We want every input point to better document the type of
> entropy source.

OK - any objections to something like this?

===================================================================
--- Documentation/feature-removal-schedule.txt  (revision 6236)
+++ Documentation/feature-removal-schedule.txt  (working copy)
@@ -6,6 +6,19 @@

 ---------------------------

+What:  IRQF_SAMPLE_RANDOM
+Check: IRQF_SAMPLE_RANDOM
+When:  July 2009
+Why:   Many of IRQF_SAMPLE_RANDOM users are technically bogus as entropy
+       sources in the kernel's current entropy model. To resolve this, every
+       input point to the kernel's entropy pool needs to better document the
+       type of entropy source it actually is. This will be replaced with
+       additional add_*_randomness functions in drivers/char/random.c
+
+Who:   Robin Getz <rgetz@...ckfin.uclinux.org> & Matt Mackall 
<mpm@...enic.com>
+
+---------------------------
+

Then if someone attempts to add it, and runs checkpatch, it will generate 
something like:

--------
ERROR: Don't use IRQF_SAMPLE_RANDOM(): see 
Documentation/feature-removal-schedule.txt
#10: FILE: serial/bfin_5xx.c:650:
+       if (request_irq(uart->port.irq, bfin_serial_rx_int, IRQF_DISABLED | 
IRQF_SAMPLE_RANDOM,
--------

My only real question is on the date... In a previous email:

On Mon 6 Apr 2009 15:01, Matt Mackall pondered:
> I'm eventually going to move the RNG away from the strict theoretical
>  entropy accounting model to a more pragmatic one which will be much
>  happier with iffy entropy sources, but that's a ways off.

I was not sure what "a ways off" was defined as - or are the two (removal of 
IRQF_SAMPLE_RANDOM, and the pragmatic entropy accounting model) separate in 
your mind? I guess various add_*_randomness functions can be added today, and 
change how they are accounted for in the future?

-Robin
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