linux-kernel - Re: [Regression?] Commit cb4f71c429 deliberately changes order of network interfaces

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Message-ID: <20160824165011.6c811913@free-electrons.com>
Date:   Wed, 24 Aug 2016 16:50:11 +0200
From:   Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>
To:     Ralph Sennhauser <ralph.sennhauser@...il.com>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Gregory CLEMENT <gregory.clement@...e-electrons.com>
Subject: Re: [Regression?] Commit cb4f71c429 deliberately changes order of
 network interfaces

Hello,

On Sun, 21 Aug 2016 15:11:58 +0200, Ralph Sennhauser wrote:

> Commit cb4f71c4298853db0c6751b1209e4535956f136c changes the order of
> the network interfaces for armada-38x. As a special exception to the
> "order by register address" rule says the comment in the dtsi. The
> commit messages even calls it a violation.
> 
> I can't remember having owned a device were the internal and external
> numbering actually matched, so the important bit for me is whatever the
> order is it should remain constant.
> 
> Distributions like OpenWrt have to fix their code when moving from 4.4
> currently to past 4.6 [1]. Worse the so called "wrong ordering" is
> actually documented [2]. There are likely more victims out there. In
> case it goes unnoticed by the distribution the users lan becomes wan
> and vice versa.

We had many many users getting confused by the fact that the order of
the network interfaces was inverted compared to:

 * The board documentations
 * The U-Boot numbering
 * And to a lesser extent, the vendor kernel

So having things match the documentation numbering was in our opinion
the least confusing thing moving forward. We should have done it
earlier, but we thought that the rule "order by register address" was a
very strong rule.

At this point, reverting the patch is I believe cause more harm than
good. It's going to re-confuse again people.

Regarding the fact that the "wrong numbering if actually documented" is
a fairly specious argument. The OpenWRT Wiki has never been an official
documentation of any sort. I see it as a much more important aspect
that the numbering of the Ethernet interfaces matches the user manual
Marvell provides with its development and evaluation boards. The
OpenWRT Wiki can certainly be fixed accordingly.

Best regards,

Thomas
-- 
Thomas Petazzoni, CTO, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com