Re: [PATCH net-next v3 0/5] net: pse-pd: pd692x0: Add permanent configuration management support

Jakub Kicinski
2025-09-22T18:02:21Z

On Mon, 22 Sep 2025 18:20:02 +0200 Kory Maincent wrote:
> > > I think the only reason to save the config in the NVM instead of the
> > > userspace is to improve boot time. As Oleksij described:
> > >
> > > He told me that he also had added support for switches in Barebox for the
> > > same reason, the boot time. I don't know if it is a reasonable reason to
> > > add it in Linux.
> >
> > Right, subjectively I focused on the last sentence of Oleksij's reply.
> > I vote we leave it out for now.
>
> I would like to restart the discussion as I have one more argument besides the
> boot time optimization coming from Luka Perkov in CC.
>
> According to him, not having this feature supported also brings an issue across
> reboot:
> "When a network switch reboots, any devices receiving Power over
> Ethernet (PoE) from that switch will lose power unless the PoE
> configuration is persisted across the reboot cycle. This creates a
> significant operational impact: WiFi access points and other
> PoE-powered devices will experience an unplanned hard power loss,
> forcing them offline without any opportunity for graceful shutdown.
>
> The critical issue is not the impact on the switch itself, but rather
> the cascading effect on all dependent infrastructure. Without
> kernel-level persistence of PoE settings, a simple switch reboot
> (whether for maintenance, updates, or recovery) forces all connected
> PoE devices into an abrupt power cycle. This results in extended
> downtime as these devices must complete their full boot sequence once
> power is restored, rather than remaining operational throughout the
> switch's reboot process."

Any sort of hot reset that maintains the pre-existing configuration
and doesn't issue resets is orthogonal to storing the configuration
into the flash.