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Date: Thu, 15 Jan 2009 13:06:26 +0000
From: "Bruce M. Simpson" <bms@FreeBSD.org>
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To: Yony Yossef <yonyossef.lists@gmail.com>
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Cc: Liran Liss <liranl@mellanox.co.il>, freebsd-net@freebsd.org,
	Oleg Kats <oleg@mellanox.co.il>, "'H.fazaeli'" <fazaeli@sepehrs.com>,
	Eitan Shefi <eitans@mellanox.co.il>, freebsd-questions@freebsd.org
Subject: Re: howto determine network device unit number? device.hints?
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Yony Yossef wrote:
> Thanks for the explanation.
>  
> So there's no way to determine this in advance.. 
> I must build a script that contains my own mapping between MAC addresses and
> the wanted interface names and run it after each driver load, rename the
> interfaces if necessary.
> It seems quite wrong, don't you agree?
>  
> And how come the unit number is given an arbitrary value? Is there a good
> reason for that?
>   

Normally the PCI probe runs in the opposite direction from that of 
Linux. It's largely to do with how the NEWBUS code walks the PCI bus. 
 From a systems management point of view, yeah, it's irritating, however 
it would probably take more effort (i.e. kernel code) to try to patch it 
to work differently, and not everyone has free time to sit down and 
patch the kernel.

That and (unlike Solaris) there is no *direct* mapping between the 
card's driver number on the bus and its network driver number.

In your case I'm not sure why your two cards would flip order. Could it 
be how your BIOS and hardware set up the PCI IDSEL lines at boot?