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From: Doug Ambrisko <ambrisko@ambrisko.com>
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To: Scott Long <scottl@freebsd.org>
Date: Mon, 16 Jun 2003 16:43:39 -0700 (PDT)
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cc: arch@freebsd.org
cc: John-Mark Gurney <gurney_j@efn.org>
Subject: Re: make /dev/pci really readable
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Scott Long writes:
| You should not always assume that reading PCI registers has no
| side-effects.  It is certainly legal and possible for a PCI device to
| detect the read request and alter the contents of the register (or some
| other register) as a side effect, or change an internal state machine.
| 'Fixing' the various bits to allow unpriviledged access to 'pciconf -r'
| is dangerous since you would have to teach the system about every pci
| device in existance and how to trap on registers that have side-effects.

I seem to recall reading some PCI chip spec. for a chip I was working on
that did a reset on read of that register.  I can't recall which or where 
so don't take this as fact but a distant memory.

Doug A.