netdev - Re: [RFC PATCH net-next 2/2] net: dsa: support SWITCHDEV_ATTR_ID_PORT_BRIDGE

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Date:	Wed, 09 Mar 2016 17:15:58 -0500
From:	Vivien Didelot <vivien.didelot@...oirfairelinux.com>
To:	Jiri Pirko <jiri@...nulli.us>, Andrew Lunn <andrew@...n.ch>
Cc:	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	kernel@...oirfairelinux.com,
	"David S. Miller" <davem@...emloft.net>,
	Florian Fainelli <f.fainelli@...il.com>,
	Scott Feldman <sfeldma@...il.com>,
	Ido Schimmel <idosch@...lanox.com>,
	nikolay@...ulusnetworks.com, Elad Raz <eladr@...lanox.com>
Subject: Re: [RFC PATCH net-next 2/2] net: dsa: support SWITCHDEV_ATTR_ID_PORT_BRIDGE_IF

Hi Jiri,

Jiri Pirko <jiri@...nulli.us> writes:

> Wed, Mar 09, 2016 at 07:32:13PM CET, andrew@...n.ch wrote:
>>Hi Vivien
>>
>>> -static bool dsa_slave_dev_check(struct net_device *dev)
>>> -{
>>> -	return dev->netdev_ops == &dsa_slave_netdev_ops;
>>> -}
>>
>>Where is the equivalent of this happening? Where do we check that the
>>interface added to the bridge is part of the switch?
>>
>>> -int dsa_slave_netdevice_event(struct notifier_block *unused,
>>> -			      unsigned long event, void *ptr)
>>> -{
>>> -	struct net_device *dev;
>>> -	int err = 0;
>>> -
>>> -	switch (event) {
>>> -	case NETDEV_CHANGEUPPER:
>>> -		dev = netdev_notifier_info_to_dev(ptr);
>>> -		if (!dsa_slave_dev_check(dev))
>>> -			goto out;
>>> -
>>> -		err = dsa_slave_master_changed(dev);
>>> -		if (err && err != -EOPNOTSUPP)
>>> -			netdev_warn(dev, "failed to reflect master change\n");
>>> -
>>> -		break;
>>> -	}
>>> -
>>> -out:
>>> -	return NOTIFY_DONE;
>>> -}
>>
>>How about team/bonding? We are not ready to implement it yet with the
>>Marvell devices, but at some point we probably will. Won't we need the
>>events then? We need to know when a switch port has been added to a
>>team?
>>
>>Or do you think a switchdev object will be added for this case?
>>Mellanox already have the ability to add switch interfaces to a team,
>>and then add the team to a bridge. So we need to ensure your solution
>>works for such stacked systems.
>
> I have to look at this more closer tomorrow, but I'm missing motivation
> behind this. Using existing notifiers, drivers can easily monitor what
> is going on with their uppers. Why do we need this to be changed?

Yes with notifiers, drivers can monitor these changes with the
NETDEV_CHANGEUPPER even. They can also forbid such bridging by returning
NOTIFY_BAD in the NETDEV_PRECHANGEUPPER event if I'm not mistaken.

But looking at DSA slave, Mellanox Spectrum, and Rocker, they all
implement this similar heavy code, while they could support a common
switchdev attribute and reduce boilerplate.

But maybe I'm wrong, what why I sent that as an RFC :-)

Thanks,
Vivien