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Message-ID: <20171110140101.GB11872@lunn.ch>
Date: Fri, 10 Nov 2017 15:01:01 +0100
From: Andrew Lunn <andrew@...n.ch>
To: Egil Hjelmeland <privat@...l-hjelmeland.no>
Cc: Roman Yeryomin <roman@...em.lv>,
Linus Walleij <linus.walleij@...aro.org>,
Vivien Didelot <vivien.didelot@...oirfairelinux.com>,
Florian Fainelli <f.fainelli@...il.com>,
netdev@...r.kernel.org,
Antti Seppälä <a.seppala@...il.com>,
Colin Leitner <colin.leitner@...glemail.com>,
Gabor Juhos <juhosg@...nwrt.org>
Subject: Re: [PATCH 4/4] RFC: net: dsa: realtek-smi: Add Realtek SMI driver
> Out of curiosity: Are there fundamental reasons why ToR switches don't use
> the DSA model, or is it more historical?
Yes, there is a fundamental reason.
https://www.netdevconf.org/2.1/session.html?lunn_didelot_fainelli
DSA always has a host Ethernet interface connected to a port of the
switch.
A pure switchdev device does not. Often, the switch is a PCIe
device. It DMAs frames directly to/from the switch.
Basically, DSA just adds another layer, abstracting that Ethernet
interface into common code which all DSA devices share.
Andrew
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