linux-kernel - Re: [PATCH 2.6.18-rc5] PCI: sort device lists breadth-first

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Date:	Fri, 8 Sep 2006 11:18:17 -0500
From:	Matt Domsch <Matt_Domsch@...l.com>
To:	Dave Jones <davej@...hat.com>
Cc:	linux-pci@...ey.karlin.mff.cuni.cz, Greg KH <greg@...ah.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2.6.18-rc5] PCI: sort device lists breadth-first

On Fri, Sep 08, 2006 at 11:56:39AM -0400, Dave Jones wrote:
> On Thu, Sep 07, 2006 at 10:14:22PM -0500, Matt Domsch wrote:
>  > Problem:
>  > New Dell PowerEdge servers have 2 embedded ethernet ports, which are
>  > labeled NIC1 and NIC2 on the chassis, in the BIOS setup screens, and
>  > in the printed documentation.  Assuming no other add-in ethernet ports
>  > in the system, Linux 2.4 kernels name these eth0 and eth1
>  > respectively.  Many people have come to expect this naming.  Linux 2.6
>  > kernels name these eth1 and eth0 respectively (backwards from
>  > expectations).  I also have reports that various Sun and HP servers
>  > have similar behavior.
>  
> This came up years back when 2.6 was something new, and the answer
> then was 'bind the interface to the MAC address'.

Both Red Hat-based distros and openSuSE-based distros do something
like this with configuration files automatically.  Red Hat's
anaconda/kudzu puts the HWADDR lines in the generated
/etc/sysconfig/network-scripts/ifcfg-* files.  openSuSE's udev rules
puts lines in /etc/udev/rules.d/30-net_persistent_names.rules the
first time it discovers a new interface.  Both methods are intended to
maintain a persistent name for each NIC, after being set up the first
time.  Neither deals well with replacing one NIC with another - you
must edit the config files.

This works pretty well post-install.  It doesn't work well at install
time, all the installers use the kernel's original names, and then
those names become the persistent names in the config files.

> Whilst your patch will fix the case that's currently broken (2.4->2.6),
> doesn't it offer equal possibility to break existing setups when people move
> from <=2.6.18 -> 2.6.19 ?

If they're using config files / udev rules as suggested, it shouldn't
break them.

If they're not, then yes, this could.  Debian's
/etc/network/interfaces file allows use of hwaddr fields, though by
default it doesn't appear anything sets it up.

I'm open to suggestions on how *not* to break setups that don't use
the MAC addresses.

Thanks,
Matt

-- 
Matt Domsch
Software Architect
Dell Linux Solutions linux.dell.com & www.dell.com/linux
Linux on Dell mailing lists @ http://lists.us.dell.com
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