netdev - RE: [RFC net-next 0/8] Introducing subdev bus and devlink extension

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Date:   Tue, 5 Mar 2019 16:52:06 +0000
From:   Parav Pandit <parav@...lanox.com>
To:     Jakub Kicinski <jakub.kicinski@...ronome.com>
CC:     Or Gerlitz <gerlitz.or@...il.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "michal.lkml@...kovi.net" <michal.lkml@...kovi.net>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        Jiri Pirko <jiri@...lanox.com>
Subject: RE: [RFC net-next 0/8] Introducing subdev bus and devlink extension



> -----Original Message-----
> From: Jakub Kicinski <jakub.kicinski@...ronome.com>
> Sent: Monday, March 4, 2019 7:46 PM
> To: Parav Pandit <parav@...lanox.com>
> Cc: Or Gerlitz <gerlitz.or@...il.com>; netdev@...r.kernel.org; linux-
> kernel@...r.kernel.org; michal.lkml@...kovi.net; davem@...emloft.net;
> gregkh@...uxfoundation.org; Jiri Pirko <jiri@...lanox.com>
> Subject: Re: [RFC net-next 0/8] Introducing subdev bus and devlink extension
> 
> On Mon, 4 Mar 2019 04:41:01 +0000, Parav Pandit wrote:
> > > > $ devlink dev show
> > > > pci/0000:05:00.0
> > > > subdev/subdev0
> > >
> > > Please don't spawn devlink instances.  Devlink instance is supposed
> > > to represent an ASIC.  If we start spawning them willy nilly for
> > > whatever software construct we want to model the clarity of the
> > > ontology will suffer a lot.
> > Devlink devices not restricted to ASIC even though today it is
> > representing ASIC for one vendor. Today for one ASIC, it already
> > presents multiple devlink devices (128 or more) for PF and VFs, two
> > PFs on same ASIC etc. VF is just a sub-device which is well defined by
> > PCISIG, whereas sub-device is not. Sub-device do consume actual ASIC
> > resources (just like PFs and VFs), Hence point-(6) of cover-letter
> > indicate that the devlink capability to tell how many such sub-devices
> > can be created.
> >
> > In above example, they are created for a given bus-device following
> > existing devlink construct.
> 
> No, it's not "representing the ASIC for one vendor".  It's how it works for
> switches (including mlxsw) and how it was described in the original cover
> letter:
> 
Sorry for the confusion.
I meant to say, my understanding is Netronome creates one devlink instance for whole ASIC.
Please correct me if this is incorrect.
mlx5_core driver creates multiple devlink devices for PF and VFs for one ASIC.

>     Introduce devlink interface and first drivers to use it
> 
>     There a is need for some userspace API that would allow to expose things
>     that are not directly related to any device class like net_device of
>     ib_device, but rather chip-wide/switch-ASIC-wide stuff.
> 
>     [...]
> 
> We can deviate from the original intent if need be and dilute the ontology.
> But let's be clear on the status quo, please.
Status quo is mlx5_core driver creates multiple devlink devices. It creates for devlink device for each PF and VF of a single ASIC.