netdev - Re: [PATCH RFC 1/2] net: dsa: integrate with SWITCHDEV for HW bridging

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Message-ID: <CAGVrzcZNEz6+peBAaSfadFf+wf9p=8EJ0yqBVZqAmnfEaPDFPA@mail.gmail.com>
Date:	Tue, 17 Feb 2015 20:53:08 -0800
From:	Florian Fainelli <f.fainelli@...il.com>
To:	Guenter Roeck <linux@...ck-us.net>
Cc:	Andrew Lunn <andrew@...n.ch>, netdev <netdev@...r.kernel.org>,
	David Miller <davem@...emloft.net>,
	Vivien Didelot <vivien.didelot@...oirfairelinux.com>,
	jerome.oufella@...oirfairelinux.com,
	Chris Healy <cphealy@...il.com>
Subject: Re: [PATCH RFC 1/2] net: dsa: integrate with SWITCHDEV for HW bridging

2015-02-17 19:53 GMT-08:00 Guenter Roeck <linux@...ck-us.net>:
> On 02/17/2015 05:19 PM, Andrew Lunn wrote:
>>>
>>> +/* Return a bitmask of all ports being currently bridged. Note that on
>>> + * leave, the mask will still return the bitmask of ports currently
>>> bridged,
>>> + * prior to port removal, and this is exactly what we want.
>>> + */
>>> +static u32 dsa_slave_br_port_mask(struct dsa_switch *ds)
>>> +{
>>> +       unsigned int port;
>>> +       u32 mask = 0;
>>> +
>>> +       for (port = 0; port < DSA_MAX_PORTS; port++) {
>>> +               if (!((1 << port) & ds->phys_port_mask))
>>> +                       continue;
>>> +
>>> +               if (ds->ports[port]->priv_flags & IFF_BRIDGE_PORT)
>>> +                       mask |= 1 << port;
>>> +       }
>>> +
>>> +       return mask;
>>> +}
>>> +
>>> +static int dsa_slave_bridge_port_join(struct net_device *dev,
>>> +                                     struct net_device *bridge)
>>> +{
>>> +       struct dsa_slave_priv *p = netdev_priv(dev);
>>> +       struct dsa_switch *ds = p->parent;
>>> +       int ret = -EOPNOTSUPP;
>>> +
>>> +       if (ds->drv->port_join_bridge)
>>> +               ret = ds->drv->port_join_bridge(ds, p->port,
>>> +
>>> dsa_slave_br_port_mask(ds));
>>
>>
>> Hi Florian
>>
>> Shouldn't this bridge port mask also be dependent on bridge?
>>
>> I'm thinking of cases like
>>
>> brctl addbr br0
>> brctl addif br0 lan0
>> brctl addif br0 lan1
>>
>> brctl addbr br1
>> brctl addif br1 lan2
>> brctl addif br1 lan3
>>
>> We have two software bridges, so need two masks.  It does look like
>> your hardware and the Marvell hardware supports this, disjoint sets of
>> bridged ports.  But with the current implementation, your going to end
>> up with one hardware bridge with four ports, and broken STP.
>>
>
> Same problem here.
>
> With the code above I see the ports which are part of "a" bridge group,
> but I can not determine which group the port is supposed to join.

I have put a v2 here which addresses that by retaining which bridge
the port was added to and comparing that against the bridge net_device
we want to join:

https://github.com/ffainelli/linux/tree/dsa-hw-bridge-v2

>
> I don't really see the value in providing the port mask to
> port_join_bridge, but maybe I am missing something. In my
> implementation I just passed on bridge * and used it to
> determine which port belongs to which bridge group.
> It doesn't have to be that, but maybe we can use the bridge
> ifindex or anything else that lets me determine which bridge
> group the port belongs to.

As I described in the cover letter, I tend to think that resolving
this bitmask is part of the abstraction DSA should provide to its
driver, maybe it is more future proof and better to give access to the
bridge net_device pointer such that drivers can figure out the bridge
details themselves. With that in mind, maybe we can do something like
this:

- add the bridge net_device pointer to the join/leave callbacks
- provide a helper like dsa_slave_br_port_mask that drivers use or not
-- 
Florian
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