Re: [patch net-next v2 05/10] rocker: introduce rocker switch driver

[Florian Fainelli <f.fainelli@gmail.com>]

Le 11/11/2014 07:40, Jiri Pirko a écrit :
> Tue, Nov 11, 2014 at 04:32:32PM CET, tgraf@suug.ch wrote:
>> On 11/11/14 at 04:19pm, Jiri Pirko wrote:
>>> Tue, Nov 11, 2014 at 03:29:46PM CET, tgraf@suug.ch wrote:
>>>> On 11/10/14 at 02:04pm, John Fastabend wrote:
>>>>> On 11/09/2014 02:51 AM, Jiri Pirko wrote:
>>>>>> +static int rocker_port_sw_parent_id_get(struct net_device *dev,
>>>>>> +					struct netdev_phys_item_id *psid)
>>>>>> +{
>>>>>> +	struct rocker_port *rocker_port = netdev_priv(dev);
>>>>>> +	struct rocker *rocker = rocker_port->rocker;
>>>>>> +
>>>>>
>>>>> hmm looks like you read this out of a magic switch register :) but
>>>>> my switch doesn't have this magic reg. I suposse the switch MAC address
>>>>> should work.
>>>>
>>>> This needs more work afterwards. Either we define that the switch ID
>>>> is only unique in combination with the parent ifindex or we need to
>>>> introduce a notation of uniquness into the switch ID itself.
>>>
>>> This is something similar to physical port id. Each driver should take
>>> care of generating that id.
>>
>> If the ID is only unique within a driver, then the user space cannot
>> rely on using the ID to group switch ports. Multiple drivers might
>> come up with the same ID.
> 
> Well, as I said, it is the same as for physical port id. But if needed,
> there can be added some simple mechanism for the id registration
> ensuring their uniqueness.

We could use the idr/ida subsystem to provide a global unique id per
switch device that gets registered, ultimately, I suspect that a
management application might want to get some sense of the topology by
exploiting some unique HW properties such as:

- MDIO bus address for MDIO-connected switches
- SPI chip-select address
- GPIO(s) used to connect
- PCI bus/slot

they are also unique by design, and add to that any revision/OUI
register that is available for the driver. I can't find of a good way to
hash that to produce a unique identifier, but maybe we can use that
information somehow.

> 
>>
>> Even now, multiple rocker instances would have the same ID.
> 
> It depends on what hw returns to driver.
>