linux-kernel - Re: [PATCH net-next 7/9] net: dsa: mv88e6xxx: restore VLANTable map control

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Date:	Fri, 26 Feb 2016 22:04:19 +0100
From:	Andrew Lunn <andrew@...n.ch>
To:	Kevin Smith <kevin.smith@...csyscorp.com>
Cc:	Vivien Didelot <vivien.didelot@...oirfairelinux.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"kernel@...oirfairelinux.com" <kernel@...oirfairelinux.com>,
	"David S. Miller" <davem@...emloft.net>,
	Florian Fainelli <f.fainelli@...il.com>,
	Sergei Shtylyov <sergei.shtylyov@...entembedded.com>,
	Guenter Roeck <linux@...ck-us.net>,
	Neil Armstrong <narmstrong@...libre.com>,
	Sascha Hauer <s.hauer@...gutronix.de>,
	Russell King <rmk+kernel@....linux.org.uk>
Subject: Re: [PATCH net-next 7/9] net: dsa: mv88e6xxx: restore VLANTable map
 control

On Fri, Feb 26, 2016 at 08:45:28PM +0000, Kevin Smith wrote:
> Hi Vivien,
> 
> On 02/26/2016 12:16 PM, Vivien Didelot wrote:
> > +	/* allow CPU port or DSA link(s) to send frames to every port */
> > +	if (dsa_is_cpu_port(ds, port) || dsa_is_dsa_port(ds, port)) {
> > +		output_ports = mask;
> > +	} else {

> Is this always correct?  Are there situations where a CPU or neighboring 
> switch should not be allowed to access another port? (e.g. Figure 6 or 7 
> in the 88E6352 functional specification).

What do these figures show?

The CPU port needs to be able to send to each external port. The whole
DSA concept is that Linux has a netdev per external port, and can send
frames using the netdev out a specific port. Such frames have a DSA
header indicating which port they are destined to.  When you have a
multi chip setup, the frame needs to traverse DSA ports.

      Andrew