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

-----Original Message-----
From: David Miller [mailto:davem@davemloft.net]
Sent: Tuesday, June 14, 2016 1:35 PM
To: pali.rohar@gmail.com
Cc: gregkh@linuxfoundation.org; andrew@lunn.ch; Limonciello, Mario
[off-list ref]; hayeswang@realtek.com; linux-
kernel@vger.kernel.org; netdev@vger.kernel.org; linux-
usb@vger.kernel.org; anthony.wong@canonical.com
Subject: Re: [PATCH v6] r8152: Add support for setting pass through MAC
address on RTL8153-AD

From: Pali Rohár <redacted>
Date: Tue, 14 Jun 2016 18:47:36 +0200

quoted

You have never seen two ethernet cards with same MAC addresses? Right

I

quoted

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.