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Date: Mon, 13 Jun 2005 17:23:07 -0600 (MDT)
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To: hselasky@c2i.net
From: "M. Warner Losh" <imp@bsdimp.com>
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Cc: freebsd-hackers@freebsd.org
Subject: Re: Obvious bug in /sys/i386/include/bus.h
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In message: <200506131412.38967.hselasky@c2i.net>
            Hans Petter Selasky <hselasky@c2i.net> writes:
: So can someone have this fixed, or is there a reason not to fix it. The one 
: who wrote the code has done the same mistake with every one of the 
: bus_space_XXXX that does memory mapped I/O. It currently breaks my drivers.

One isn't supposed to call these routines with count == 0.  One could
say your drivers are broken :-)

Back when these were written, small optimizations like this were made
to make things go faster.  Now that cache sizes are bigger, a few
extra instructions likely wouldn't affect things too much.  Best to
measure the effects of your proposed changes on real workloads...

Warner