netdev - RE: [RFC PATCH v4 2/4] dpll: Add DPLL framework base functions

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Message-ID: <DM6PR11MB4657C8417DEB0B14EC35802E9B179@DM6PR11MB4657.namprd11.prod.outlook.com>
Date:   Fri, 2 Dec 2022 14:54:33 +0000
From:   "Kubalewski, Arkadiusz" <arkadiusz.kubalewski@...el.com>
To:     Jiri Pirko <jiri@...nulli.us>
CC:     Vadim Fedorenko <vfedorenko@...ek.ru>,
        Jakub Kicinski <kuba@...nel.org>,
        Jonathan Lemon <jonathan.lemon@...il.com>,
        Paolo Abeni <pabeni@...hat.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Vadim Fedorenko <vadfed@...com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-clk@...r.kernel.org" <linux-clk@...r.kernel.org>,
        "Olech, Milena" <milena.olech@...el.com>,
        "Michalik, Michal" <michal.michalik@...el.com>
Subject: RE: [RFC PATCH v4 2/4] dpll: Add DPLL framework base functions

>From: Jiri Pirko <jiri@...nulli.us>
>Sent: Friday, December 2, 2022 1:40 PM
>
>Fri, Dec 02, 2022 at 12:27:35PM CET, arkadiusz.kubalewski@...el.com wrote:
>>>From: Jiri Pirko <jiri@...nulli.us>
>>>Sent: Wednesday, November 30, 2022 5:37 PM Tue, Nov 29, 2022 at
>>>10:37:22PM CET, vfedorenko@...ek.ru wrote:
>>>>From: Vadim Fedorenko <vadfed@...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
>

OK, I now see your point what is the confusion.
Thanks for explanation.
But I am still not sure how to make it this way in Linux, if interface added to
netns uses original netdev ifindex, and driver after reload receives new
(previously unused ifindex) what would be the steps/commands to make it as you
described? 

>>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.

Sure, I won't insist on having it there, as I said, thought Maciej have seen
a benefit with such traceability, unfortunately I cannot recall what was it.


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