From owner-freebsd-hackers@FreeBSD.ORG  Mon Oct 24 16:28:03 2005
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Date: Mon, 24 Oct 2005 10:27:47 -0600 (MDT)
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From: "M. Warner Losh" <imp@bsdimp.com>
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Cc: frank@pinky.sax.de, freebsd-hackers@freebsd.org
Subject: Re: How disable attachment of sio(4) driver to device?
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In message: <200510241120.31203.jhb@freebsd.org>
            John Baldwin <jhb@freebsd.org> writes:
: Only if you make sure that sio(4) doesn't try to pass data between probe() and 
: attach() via the softc since the softc is preserved from probe to attach if 
: you return 0 from probe.

sio's probe routine, now that you mention this, I believe leaves
things in a state that sioattach knows abou.

However, it looks like the probe routine will get called twice when
you return < 0, so maybe this is OK.

Warner