Subject: Re: [PATCH net-next v3 2/5] swdevice: add new api to set and del bridge port attributes

From: roopa <[email-masked]>
Date: Sat, 24 Jan 2015 17:03:51 -0800

On 1/24/15, 3:26 AM, Jiri Pirko wrote:
> Sat, Jan 24, 2015 at 12:10:01AM CET, [email-masked] wrote:
>> On 1/23/15, 2:45 PM, roopa wrote:
>>> On 1/23/15, 8:06 AM, Jiri Pirko wrote:
>>>> Fri, Jan 23, 2015 at 04:58:57PM CET, [email-masked] wrote:
>>>>> On 1/23/15, 2:41 AM, Jiri Pirko wrote:
>>>>>
>>>>> <snip..>
>>>>>> +
>>>>>> +/**
>>>>>> + *    netdev_switch_port_bridge_dellink - Notify switch device port
>>>>>> of bridge
>>>>>> + *    attribute delete
>>>>>> + *
>>>>>> + *    @dev: port device
>>>>>> + *    @nlh: netlink msg with bridge port attributes
>>>>>> + *
>>>>>> + *    Notify switch device port of bridge port attribute delete
>>>>>> + */
>>>>>> +int netdev_switch_port_bridge_dellink(struct net_device *dev,
>>>>>> +                      struct nlmsghdr *nlh, u16 flags)
>>>>>> +{
>>>>>> +    const struct net_device_ops *ops = dev->netdev_ops;
>>>>>> +    struct net_device *lower_dev;
>>>>>> +    struct list_head *iter;
>>>>>> +    int ret = 0, err = 0;
>>>>>> +
>>>>>> +    if (!(dev->features & NETIF_F_HW_NETFUNC_OFFLOAD))
>>>>>> +        return err;
>>>>>> +
>>>>>> +    if (ops->ndo_bridge_dellink) {
>>>>>> +        WARN_ON(!ops->ndo_switch_parent_id_get);
>>>>>> +        return ops->ndo_bridge_dellink(dev, nlh, flags);
>>>>>> +    }
>>>>>> +
>>>>>> +    netdev_for_each_lower_dev(dev, lower_dev, iter) {
>>>>>> +        err = netdev_switch_port_bridge_dellink(lower_dev, nlh,
>>>>>> flags);
>>>>>> +        if (err)
>>>>>> +            ret = err;
>>>>>> +    }
>>>>>> +
>>>>>> +    return ret;
>>>>>> +}
>>>>>> +EXPORT_SYMBOL(netdev_switch_port_bridge_dellink);
>>>>>> -- 
>>>>>> 1.7.10.4
>>>>>>
>>>>>> Is there any other place, other than bridge code, this functions are
>>>>>> suppored to be called from?
>>>>> No other place today. Its usually the master that implements
>>>>> ndo_bridge_setlink/dellink.
>>>>>
>>>>>> If not, which I consider likely, it would
>>>>>> make more sense to me to:
>>>>>>
>>>>>> - move netdev_for_each_lower_dev iterations directly to bridge code
>>>>>> - let the masters (bond, team, ..) implement ndo_bridge_*link and do
>>>>>>    the traversing there (can be in a form of pre-prepared default
>>>>>>    ndo callback (ndo_dflt_netdev_switch_port_bridge_*link)
>>>>> But, i am still not understanding why i would modify bond, team and
>>>>> other
>>>>> slaves
>>>> Well, that is the usual way to propagate ndo calls. People are used to
>>>> this. It is visible right away in bonding/other code that is propagated
>>>> some ndo call to slaves. With your code, that is somehow hidden and only
>>>> dependent on NETIF_F_HW_NETFUNC_OFFLOAD flag.
>>>>
>>>> Note that there are only couple of "master drivers" (for this, most
>>>> likely
>>>> only bond and team modifications are needed).
>>> ndo_bridge_setlink today is only implemented by drivers that implement
>>> bridging function.
>>> So, having the bond and team driver implement it...seems odd.
> Well, it is not odd. It is ok I believe. Same as for example:
> .ndo_set_mac_address
> .ndo_change_mtu
> .ndo_vlan_rx_add_vid
> .ndo_vlan_rx_kill_vid
> .ndo_poll_controller
> .ndo_netpoll_setup
> .ndo_netpoll_cleanup
>
> All take care of propagating the ndo to slaves.
These mostly operate on netdevs directly.
I do have some hesitation, But, I will take your suggestion and add it 
to the bond and team drivers,
>
>>> But if you insist, i am going to do just that.
>> A side note, I dont see any reason for ndo_bridge_setlink to be renamed to
>> ndo_setlink. Because it seems to take the whole netlink msg anyways. It can
>> be used to offload other link attributes besides bridging (vxlan and so on).
>> Any thoughts on that ?.
> Well, it is PF_BRIDGE so I think that the name is accurate.
The ndo op does not necessarily have to be tied to the netlink msg family.
I don't plan to rename it now. But, in future if i see more value in 
reusing it for other offloads,
i will come back to this.

Thanks for the review.