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

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Message-ID: <Z66WfMwNpVBeWLLq@x130>
Date: Thu, 13 Feb 2025 17:03:56 -0800
From: Saeed Mahameed <saeed@...nel.org>
To: Leon Romanovsky <leon@...nel.org>
Cc: "Nelson, Shannon" <shannon.nelson@....com>,
	Jakub Kicinski <kuba@...nel.org>, Jason Gunthorpe <jgg@...dia.com>,
	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 12 Feb 15:22, Leon Romanovsky wrote:
>On Tue, Feb 11, 2025 at 10:36:37AM -0800, Nelson, Shannon wrote:
>> 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?
>
>IMHO, linux-pci was right place before FWCTL and auxbus arrived, but now
>these core drivers can be placed in drivers/fwctl instead. It will be natural
+1

Fwctl subsystem is perfect for shared modules that need to initialize the
pci device to a minimal state where fwctl uAPIs are enabled for debug and
bare metal device configs while aux sunsystem can carry out the
spawning of other subsystems.

>place for them as they will be located near the UAPI which provides an access
>to them.
>
>All other components will be auxbus devices in their respective
>subsystems (eth, RDMA ...).
>
>Thanks
>
>>
>> sln
>>
>>
>