Re: [RFC PATCH v4 2/4] dpll: Add DPLL framework base functions

Jiri Pirko
2022-12-02T12:39:47Z

Fri, Dec 02, 2022 at 12:27:35PM CET, arkadiusz.kubalewski@intel.com wrote:
>>From: Jiri Pirko <jiri@resnulli.us>
>>Sent: Wednesday, November 30, 2022 5:37 PM
>>Tue, Nov 29, 2022 at 10:37:22PM CET, vfedorenko@novek.ru wrote:
>>>From: Vadim Fedorenko <vadfed@fb.com>

[...]

>>>+static int
>>>+dpll_msg_add_pin_netifindex(struct sk_buff *msg, const struct
>>dpll_pin_attr *attr)
>>>+{
>>>+ unsigned int netifindex; // TODO: Should be u32?
>>>+
>>>+ if (dpll_pin_attr_netifindex_get(attr, &netifindex))
>>>+ return 0;
>>>+ if (nla_put_u32(msg, DPLLA_PIN_NETIFINDEX, netifindex))
>>
>>I was thinking about this. It is problematic. DPLL has no notion of
>>network namespaces. So if the driver passes ifindex, dpll/user has no
>>clue in which network namespace it is (ifindexes ovelay in multiple
>>namespaces).
>>
>>There is no easy/nice solution. For now, I would go without this and
>>only have linkage the opposite direction, from netdev to dpll.
>
>Well, makes sense to me.
>Although as I have checked `ip a` showed the same ifindex either if port was
>in the namespace or not.

That is not the problem. The problem is, that you can have following
two netdevs with the same ifindex each in different netns.
1) netdev x: ifindex 8, netns ns1
2) netdev y: ifindex 8, netns ns2

>Isn't it better to let the user know ifindex, even if he has to iterate all
>the namespaces he has created?

Definitelly not. As I showed above, one ifindex may refer to multiple
netdevice instances.

[...]

>>>+ DPLLA_NETIFINDEX,
>>
>>Duplicate, you have it under pin.
>
>The pin can have netifindex as pin signal source may originate there by
>Clock recovery mechanics.
>The dpll can have ifindex as it "owns" the dpll.

DPLL is not owned by any netdevice. That does not make any sense.
Netdevice may be "child" of the same PCI device as the dpll instance.
But that's it.

>Shall user know about it? probably nothing usefull for him, although
>didn't Maciej Machnikowski asked to have such traceability?