netdev - Re: [PATCH v4 10/10] bnxt: Create an auxiliary device for fwctl

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Message-ID: <b0395452-dc56-414d-950c-9d0c68cf0f4a@amd.com>
Date: Tue, 11 Feb 2025 10:36:37 -0800
From: "Nelson, Shannon" <shannon.nelson@....com>
To: Leon Romanovsky <leon@...nel.org>, Jakub Kicinski <kuba@...nel.org>,
 Jason Gunthorpe <jgg@...dia.com>
Cc: Saeed Mahameed <saeedm@...dia.com>,
 Andy Gospodarek <andrew.gospodarek@...adcom.com>,
 Aron Silverton <aron.silverton@...cle.com>,
 Dan Williams <dan.j.williams@...el.com>,
 Daniel Vetter <daniel.vetter@...ll.ch>, Dave Jiang <dave.jiang@...el.com>,
 David Ahern <dsahern@...nel.org>, Andy Gospodarek <gospo@...adcom.com>,
 Christoph Hellwig <hch@...radead.org>, Itay Avraham <itayavr@...dia.com>,
 Jiri Pirko <jiri@...dia.com>, Jonathan Cameron
 <Jonathan.Cameron@...wei.com>, Leonid Bloch <lbloch@...dia.com>,
 linux-cxl@...r.kernel.org, linux-rdma@...r.kernel.org,
 netdev@...r.kernel.org, Michael Chan <michael.chan@...adcom.com>
Subject: Re: [PATCH v4 10/10] bnxt: Create an auxiliary device for fwctl_bnxt

On 2/10/2025 11:55 PM, Leon Romanovsky wrote:
> 
> On Mon, Feb 10, 2025 at 05:04:23PM -0800, Jakub Kicinski wrote:
>> On Fri, 7 Feb 2025 21:16:47 -0400 Jason Gunthorpe wrote:
>>> On Fri, Feb 07, 2025 at 01:51:11PM -0800, Jakub Kicinski wrote:
>>>
>>>> But if you agree the netdev doesn't need it seems like a fairly
>>>> straightforward way to unblock your progress.
>>>
>>> I'm trying to understand what you are suggesting here.
>>>
>>> We have many scenarios where mlx5_core spawns all kinds of different
>>> devices, including recovery cases where there is no networking at all
>>> and only fwctl. So we can't just discard the aux dev or mlx5_core
>>> triggered setup without breaking scenarios.
>>>
>>> However, you seem to be suggesting that netdev-only configurations (ie
>>> netdev loaded but no rdma loaded) should disable fwctl. Is that the
>>> case? All else would remain the same. It is very ugly but I could see
>>> a technical path to do it, and would consider it if that brings peace.
>>
>> Yes, when RDMA driver is not loaded there should be no access to fwctl.
> 
> There are users mentioned in cover letter, which need FWCTL without RDMA.
> https://lore.kernel.org/all/0-v4-0cf4ec3b8143+4995-fwctl_jgg@nvidia.com/
> 
> I want to suggest something different. What about to move all XXX_core
> logic (mlx5_core, bnxt_core, e.t.c.) from netdev to some other dedicated
> place?
> 
> There is no technical need to have PCI/FW logic inside networking stack.
> 
> Thanks

Our pds_core device fits this description as well: it is not an ethernet 
PCI device, but helps manage the FW/HW for Eth and other things that are 
separate PCI functions.  We ended up in the netdev arena because we 
first went in as a support for vDPA VFs.

Should these 'core' devices live in linux-pci land?  Is it possible that 
some 'core' things might be platform devices rather than PCI?

sln