netdev - Re: [patch net-next RFC 0/6] Introduce devlink interface and first drivers to use it

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Date:	Mon, 8 Feb 2016 11:55:29 +0100
From:	Jiri Pirko <jiri@...nulli.us>
To:	Hannes Frederic Sowa <hannes@...essinduktion.org>
Cc:	Alexei Starovoitov <alexei.starovoitov@...il.com>,
	Daniel Borkmann <daniel@...earbox.net>,
	Jesper Dangaard Brouer <brouer@...hat.com>,
	netdev@...r.kernel.org, davem@...emloft.net, idosch@...lanox.com,
	eladr@...lanox.com, yotamg@...lanox.com, ogerlitz@...lanox.com,
	yishaih@...lanox.com, dledford@...hat.com, sean.hefty@...el.com,
	hal.rosenstock@...il.com, eugenia@...lanox.com,
	roopa@...ulusnetworks.com, nikolay@...ulusnetworks.com,
	hadarh@...lanox.com, jhs@...atatu.com, john.fastabend@...il.com,
	jeffrey.t.kirsher@...el.com, jbenc@...hat.com
Subject: Re: [patch net-next RFC 0/6] Introduce devlink interface and first
 drivers to use it

Mon, Feb 08, 2016 at 11:15:38AM CET, hannes@...essinduktion.org wrote:
>Hello,
>
>On 06.02.2016 20:40, Jiri Pirko wrote:
>>Fri, Feb 05, 2016 at 06:38:42PM CET, alexei.starovoitov@...il.com wrote:
>>>On Fri, Feb 05, 2016 at 11:01:22AM +0100, Hannes Frederic Sowa wrote:
>>>>
>>>>Okay. I see it more as changing mode of operation of hardware and thus has
>>>>not really anything to do with networking. If you say you change ethernet to
>>>>infiniband it has something to do with networking, sure. But I am fine with
>>>>this, I just thought the code size could be reduced by adding this to sysfs
>>>>quite a lot. I don't have a strong opinion on this.
>>>
>>>there is already a way to change eth/ib via
>>>echo 'eth' > /sys/bus/pci/drivers/mlx4_core/0000:02:00.0/mlx4_port1
>>>
>>>sounds like this is another way to achieve the same?
>>
>>It is. However the current way is driver-specific, not correct.
>
>Why is driver specific not correct? Actually it is very much a device
>specific thing, isn't it?

Well, adding driver specific sysfs file called "driver_name_port_type"
does not seem correct to me.

>
>>For mlx5, we need the same, it cannot be done in this way. Do devlink is
>>the correct way to go.
>
>Do two drivers already justify a new complete netlink api? Doesn't this
>create the same problems like netdevice naming problems which needed multiple
>years to become stable in case we have multiple cards or some administrator

The thing is, other driver would use it as well, but there's no way to
do it :) So vendors have their proprietary configuration utils. Devlink
objective is to avoid those, to introduce vendor-neutral interface.


>reorders the cards (biosdevorder, systemd/udev issues)? Are ports always
>stable? How can we have a 1:1 relationship with ifindexes and how can they be
>stable? It is impossible to use that in scripts?

Port index is setup by driver always, they have stable internal
numbering. devlink device name is not stable (as for example netdev
name), but can be easily identified by bus name and device name. I don't
see a reason why udev cannot rename it according to some rules. By the
way, this is very similar to phyX wireless devices.


>
>>>Why not hide echo/cat in iproute2 instead of adding parallel netlink api?
>>>Or this is for switches instead of nics?
>>>Then why it's not adding to switchdev?
>>
>>Note this is not specific to switch ASICs. This is for all network devices.
>
>That's actually my fear. The relationship from "devlink-names" to ifindexes I
>didn't understand at all architecturally.

Again, this is very similar to phyX wireless devices.
I don't understand the reason for your fear :)