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Date:      Wed, 20 Jun 2001 19:06:42 -0400
From:      Bosko Milekic <bmilekic@technokratis.com>
To:        Jordan Hubbard <jkh@osd.bsdi.com>
Cc:        bright@sneakerz.org, cvs-committers@FreeBSD.org, cvs-all@FreeBSD.org
Subject:   Re: cvs commit: src/sys/dev/lge if_lge.c src/sys/dev/nge if_nge.c src/sys/dev/vx if_vx.c src/sys/kern uipc_mbuf.c src/sys/pci if_dc.c if_rl.c if_sf.c if_sis.c if_sk.c if_vr.c if_wb.c
Message-ID:  <20010620190642.A36898@technokratis.com>
In-Reply-To: <20010620151043X.jkh@osd.bsdi.com>; from jkh@osd.bsdi.com on Wed, Jun 20, 2001 at 03:10:43PM -0700
References:  <20010620162727.K4543@sneakerz.org> <20010620174149.A36453@technokratis.com> <20010620170145.N4543@sneakerz.org> <20010620151043X.jkh@osd.bsdi.com>

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On Wed, Jun 20, 2001 at 03:10:43PM -0700, Jordan Hubbard wrote:
> To be fair to Bosko, what it looks like he's saying is that there's no
> reason to pass _any_ value to it since only zero is allowed and it
> doesn't do anything different if you pass a difference value.  That
> would mean that people *can't* "rely on m_devget doing the wrong
> thing" because m_devget is currently capable of doing only one thing,
> regardless of what you pass to it, in any case.

	First of all, let me clarify by saying that none of our present code,
-CURRENT and -STABLE included, passes anything other than 0 as the `offset'
argument to m_devget() prior to this change. And if there is third-party
code doing that, then it is likely doing it for the wrong reason. The code
that may have required the `offset' argument as it was prior to this change
has been ripped out from FreeBSD long ago.
	The NetBSD guys have it documented:

	/*
	 * If 'off' is non-zero, packet is trailer-encapsulated, so we have
	 * to skip the type and length fields.
	 */

	As jlemon pointed out, related code has been ripped out and we'll
never see users for this code. If someone is using the `off' argument, they're
not getting what they paid for and probably have a broken driver.
	So yeah, only 0 is allowed because anything non-zero has insignificant
effects.
 
> - Jordan
 
-- 
 Bosko Milekic
 bmilekic@technokratis.com


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