netdev - Re: [PATCH net-next V6 09/13] devlink: Add 'keep_link

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Message-ID: <20250710152421.31901790@kernel.org>
Date: Thu, 10 Jul 2025 15:24:21 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: Saeed Mahameed <saeed@...nel.org>
Cc: "David S. Miller" <davem@...emloft.net>, Paolo Abeni
 <pabeni@...hat.com>, Eric Dumazet <edumazet@...gle.com>, Saeed Mahameed
 <saeedm@...dia.com>, netdev@...r.kernel.org, Tariq Toukan
 <tariqt@...dia.com>, Gal Pressman <gal@...dia.com>, Leon Romanovsky
 <leonro@...dia.com>, Jiri Pirko <jiri@...dia.com>, Simon Horman
 <horms@...nel.org>
Subject: Re: [PATCH net-next V6 09/13] devlink: Add 'keep_link_up' generic
 devlink device param

On Wed, 9 Jul 2025 23:04:07 -0700 Saeed Mahameed wrote:
> On 09 Jul 19:58, Jakub Kicinski wrote:
> >On Tue,  8 Jul 2025 20:04:51 -0700 Saeed Mahameed wrote:  
> >> Devices that support this in permanent mode will be requested to keep the
> >> port link up even when driver is not loaded, netdev carrier state won't
> >> affect the physical port link state.
> >>
> >> This is useful for when the link is needed to access onboard management
> >> such as BMC, even if the host driver isn't loaded.  
> >
> >Dunno. This deserves a fuller API, and it's squarely and netdev thing.
> >Let's not add it to devlink.  
> 
> I don't see anything missing in the definition of this parameter
> 'keep_link_up' it is pretty much self-explanatory, for legacy reasons the
> netdev controls the underlying physical link state. But this is not
> true anymore for complex setups (multi-host, DPU, etc..).

The policy can be more complex than "keep_link_up"
Look around the tree and search the ML archives please.

> This is not different as BMC is sort of multi-host, and physical link
> control here is delegated to the firmware.
> 
> Also do we really want netdev to expose API for permanent nic tunables ?
> I thought this is why we invented devlink to offload raw NIC underlying
> tunables.

Are you going to add devlink params for link config?
Its one of the things that's written into the NVMe, usually..