From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 12758285CA2; Mon, 22 Sep 2025 18:02:21 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1758564142; cv=none; b=daumaz1uERir793tRZdYDyjc7IC0jj5Nm+S3wPYv8sLTYohdSJ5kHkK7n/MuqRWjZvwOSHie1A4j/3rwfYHKt21e/u6+PxrZBZi2WwAPq4glbiLZ9jDQ4TB2gEIIfLwnXQyPSwn9tAvct61a2tdYjArwT50KfYqs7GSFUOkIxeo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1758564142; c=relaxed/simple; bh=hqcYFdmQGHTd43tWX+HtkWYFfrsMuhVJNngoHln+C3Q=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=IoLn1qznjnOmeAPVhLWD/zyKviDYUir8LKJRHlkI7ZO3doKen+EAV/tVTKqEGIRDLYEG2ifDYDqkvplaR2BuC/Ek4Cf31ERZjT3H+76FHwurVR0ymazsCLOrl1GiTQFErT8542HxbabfWQTxRKUtd1Xu1NeqwXu2bukpF+9G718= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Q3/rDtC0; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Q3/rDtC0" Received: by smtp.kernel.org (Postfix) with ESMTPSA id F101BC4CEF0; Mon, 22 Sep 2025 18:02:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1758564141; bh=hqcYFdmQGHTd43tWX+HtkWYFfrsMuhVJNngoHln+C3Q=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=Q3/rDtC09F2D7j5nsSE36Hh9igWt74TsxXzWN5xRvGxL30R5IfeLUt2JHOJde47Pg SRyWEIfULyXRu2UR5MoYo0ZFLBJ6ssfNPv0UXzvsKUVZ7Ooh9Pv8xNrPCHVzAdTxV0 rWLW54H2pCz3KZGSgybvsSVo/+IvH06snSiQYsFFaDCvUlvo3fkr+gslKG8Ev0ylXA raP7KfC8MkXOGRkSoUgaaB3SPOovJ6fxbvgotU0qJwhKr6Xgq4sKq4omS3FPlV6Gwg WLKIpgbzM3FMPlvNIWNdAegT5ITsYx8YdIkxflOHnXX6cHm0rN9I/HAfxPlob7zyml QQ+HrKcCIbIvw== Date: Mon, 22 Sep 2025 11:02:20 -0700 From: Jakub Kicinski To: Kory Maincent Cc: Oleksij Rempel , Andrew Lunn , "David S. Miller" , Eric Dumazet , Paolo Abeni , Jiri Pirko , Simon Horman , Jonathan Corbet , Donald Hunter , kernel@pengutronix.de, Dent Project , Thomas Petazzoni , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Maxime Chevallier , linux-doc@vger.kernel.org, Kyle Swenson , Luka Perkov , Robert Marko , Sridhar Rao Subject: Re: [PATCH net-next v3 0/5] net: pse-pd: pd692x0: Add permanent configuration management support Message-ID: <20250922110220.4909e58b@kernel.org> In-Reply-To: <20250922182002.6948586f@kmaincent-XPS-13-7390> References: <20250915-feature_poe_permanent_conf-v3-0-78871151088b@bootlin.com> <20250916165440.3d4e498a@kernel.org> <20250917114655.6ed579eb@kmaincent-XPS-13-7390> <20250917141912.314ea89b@kernel.org> <20250922182002.6948586f@kmaincent-XPS-13-7390> Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit 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.