netdev - RE: [PATCH v6] r8152: Add support for setting pass through MAC address on RTL8153-AD

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Date:	Tue, 14 Jun 2016 22:27:12 +0000
From:	<Mario_Limonciello@...l.com>
To:	<davem@...emloft.net>, <pali.rohar@...il.com>
CC:	<gregkh@...uxfoundation.org>, <andrew@...n.ch>,
	<hayeswang@...ltek.com>, <linux-kernel@...r.kernel.org>,
	<netdev@...r.kernel.org>, <linux-usb@...r.kernel.org>,
	<anthony.wong@...onical.com>
Subject: RE: [PATCH v6] r8152: Add support for setting pass through MAC
 address on RTL8153-AD

> -----Original Message-----
> From: David Miller [mailto:davem@...emloft.net]
> Sent: Tuesday, June 14, 2016 1:35 PM
> To: pali.rohar@...il.com
> Cc: gregkh@...uxfoundation.org; andrew@...n.ch; Limonciello, Mario
> <Mario_Limonciello@...l.com>; hayeswang@...ltek.com; linux-
> kernel@...r.kernel.org; netdev@...r.kernel.org; linux-
> usb@...r.kernel.org; anthony.wong@...onical.com
> Subject: Re: [PATCH v6] r8152: Add support for setting pass through MAC
> address on RTL8153-AD
> 
> From: Pali Rohár <pali.rohar@...il.com>
> Date: Tue, 14 Jun 2016 18:47:36 +0200
> 
> > You have never seen two ethernet cards with same MAC addresses? Right
> I
> > have not seen two USB, but there is non zero chance that could happen.
> 
> It would be an error scenerio, and something to be avoided.
> 
> It is a valid and correct assumption that one is able to put
> several devices at the same time on the same physical network
> and expect it to work.
> 
> The behavior added by the change in question invalidates that.
> 
> I'm trying to consider the long term aspects of this, which is that if
> more devices adopt this scheme we're in trouble if we blindly
> interpret the MAC address in this way.
> 

Do you mean if other manufacturers start to ship devices with 
RTL8135-AD's w/ this pass through bit set and people start to try to 
mix and match?

> This firmware MAC property facility seems to be designed with only an
> extremely narrow use case being considered.

Yes, as I understand it this is the reason that it's only on such specific devices
that the mac address pass through bit is actually set on the efuse.