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

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Message-ID: <20250828153845.4928772b@kernel.org>
Date: Thu, 28 Aug 2025 15:38:45 -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 Thu, 28 Aug 2025 13:09:50 -0700 Saeed Mahameed wrote:
> >> 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.
> 
> Sorry for replying late, had to work on other stuff and was waiting
> internally for a question I had to ask about this, only recently got the
> answer.
> 
> I get your point, but I am not trying to implement any link policy
> or eth link specification tunables. For me and maybe other vendors
> this knob makes sense, and Important for the usecase I described.

I think I was alluding to making the link stay up dependent on presence
of BMC / management engine and or some NIC-internal agents. So to give
a trivial example the policy could be:
 - force down
 - leave up if BMC present
 - force up
I don't recall prior discussions TBH so doing more research will be
necessary..