Re: [RFC] current devlink extension plan for NICs

From: Jiri Pirko <jiri@resnulli.us>
To: Jakub Kicinski <kuba@kernel.org>
Cc: netdev@vger.kernel.org, davem@davemloft.net, parav@mellanox.com,
	yuvalav@mellanox.com, jgg@ziepe.ca, saeedm@mellanox.com,
	leon@kernel.org, andrew.gospodarek@broadcom.com,
	michael.chan@broadcom.com, moshe@mellanox.com, ayal@mellanox.com,
	eranbe@mellanox.com, vladbu@mellanox.com, kliteyn@mellanox.com,
	dchickles@marvell.com, sburla@marvell.com, fmanlunas@marvell.com,
	tariqt@mellanox.com, oss-drivers@netronome.com,
	snelson@pensando.io, drivers@pensando.io, aelior@marvell.com,
	GR-everest-linux-l2@marvell.com, grygorii.strashko@ti.com,
	mlxsw@mellanox.com, idosch@mellanox.com, markz@mellanox.com,
	jacob.e.keller@intel.com, valex@mellanox.com,
	linyunsheng@huawei.com, lihong.yang@intel.com,
	vikas.gupta@broadcom.com, magnus.karlsson@intel.com
Subject: Re: [RFC] current devlink extension plan for NICs
Date: Thu, 26 Mar 2020 15:59:53 +0100	[thread overview]
Message-ID: <20200326145953.GY11304@nanopsycho.orion> (raw)
In-Reply-To: <20200323122123.2a3ff20f@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>

>> >> >> $ devlink slice add pci/0000.06.00.0/100 flavour pcisf pfnum 1 sfnum 10 hw_addr aa:bb:cc:aa:bb:cc    
>> >> >
>> >> >Why is the SF number specified by the user rather than allocated?    
>> >> 
>> >> Because it is snown in representor netdevice name. And you need to have
>> >> it predetermined: enp6s0pf1sf10  
>> >
>> >I'd think you need to know what was assigned, not necessarily pick
>> >upfront.. I feel like we had this conversation before as well.  
>> 
>> Yeah. For the scripting sake, always when you create something, you can
>> directly use it later in the script. Like if you create a bridge, you
>> assign it a name so you can use it.
>> 
>> The "what was assigned" would mean that the assigne
>> value has to be somehow returned from the kernel and passed to the
>> script. Not sure how. Do you have any example where this is happening in
>> networking?
>
>Not really, but when allocating objects it seems idiomatic to get the
>id / handle / address of the new entity in response. Seems to me we're
>not doing it because the infrastructure for it is not in place, but
>it'd be a good extension.
>
>Times are a little crazy but I can take a poke at implementing
>something along those lines once I find some time..

I can't really see how is this supposed to work efficiently. Imagine a
simple dummy script:
devlink slice add pci/0000.06.00.0/100 flavour pcisf pfnum 1 sfnum 10
devlink slice set pci/0000.06.00.0/100 hw_addr aa:bb:cc:aa:bb:cc
devlink slice del pci/0000.06.00.0/100

The handle is clear then, used for add/set/del. The same thing.

Now with dynamically allocated index that you suggest:
devlink slice add pci/0000.06.00.0 flavour pcisf pfnum 1 sfnum 10
#somehow get the 100 into variable $XXX
XXX=???
devlink slice set pci/0000.06.00.0/$XXX hw_addr aa:bb:cc:aa:bb:cc
devlink slice del pci/0000.06.00.0/$XXX

there are two things I don't like about this:
1) You use different handles for different actions.
2) You need to somehow get the number into variable $XXX

What is the benefit of this approach?