netdev - Re: [PATCH net-next 03/13] devlink: Support add and delete devlink port

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Message-ID: <e7b2b21f-b7d0-edd5-1af0-a52e2fc542ce@gmail.com>
Date:   Wed, 18 Nov 2020 09:21:26 -0700
From:   David Ahern <dsahern@...il.com>
To:     Parav Pandit <parav@...dia.com>, netdev@...r.kernel.org,
        linux-rdma@...r.kernel.org, gregkh@...uxfoundation.org
Cc:     jiri@...dia.com, jgg@...dia.com, dledford@...hat.com,
        leonro@...dia.com, saeedm@...dia.com, kuba@...nel.org,
        davem@...emloft.net, Vu Pham <vuhuong@...dia.com>
Subject: Re: [PATCH net-next 03/13] devlink: Support add and delete devlink
 port

On 11/12/20 12:24 PM, Parav Pandit wrote:
> Extended devlink interface for the user to add and delete port.
> Extend devlink to connect user requests to driver to add/delete
> such port in the device.
> 
> When driver routines are invoked, devlink instance lock is not held.
> This enables driver to perform several devlink objects registration,
> unregistration such as (port, health reporter, resource etc)
> by using exising devlink APIs.
> This also helps to uniformly use the code for port unregistration
> during driver unload and during port deletion initiated by user.
> 
> Examples of add, show and delete commands:
> $ devlink dev eswitch set pci/0000:06:00.0 mode switchdev
> 
> $ devlink port show
> pci/0000:06:00.0/65535: type eth netdev ens2f0np0 flavour physical port 0 splittable false
> 
> $ devlink port add pci/0000:06:00.0 flavour pcisf pfnum 0 sfnum 88
> 
> $ devlink port show pci/0000:06:00.0/32768
> pci/0000:06:00.0/32768: type eth netdev eth0 flavour pcisf controller 0 pfnum 0 sfnum 88 external false splittable false
>   function:
>     hw_addr 00:00:00:00:88:88 state inactive opstate detached
> 

There has to be limits on the number of sub functions that can be
created for a device. How does a user find that limit?

Also, seems like there are hardware constraint at play. e.g., can a user
reduce the number of queues used by the physical function to support
more sub-functions? If so how does a user programmatically learn about
this limitation? e.g., devlink could have support to show resource
sizing and configure constraints similar to what mlxsw has.