netdev - Re: [PATCH 1/2] ethtool: transceiver reset and presence pin control

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Message-ID: <8b8dca4d-bdf3-49e4-b081-5f51e26269bb@lunn.ch>
Date: Mon, 7 Apr 2025 22:39:17 +0200
From: Andrew Lunn <andrew@...n.ch>
To: Marek Pazdan <mpazdan@...sta.com>
Cc: linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
	intel-wired-lan@...ts.osuosl.org,
	Tony Nguyen <anthony.l.nguyen@...el.com>,
	Przemek Kitszel <przemyslaw.kitszel@...el.com>,
	Andrew Lunn <andrew+netdev@...n.ch>,
	"David S . Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Simon Horman <horms@...nel.org>,
	Kory Maincent <kory.maincent@...tlin.com>,
	Willem de Bruijn <willemb@...gle.com>,
	Alexander Lobakin <aleksander.lobakin@...el.com>,
	Mina Almasry <almasrymina@...gle.com>,
	Edward Cree <ecree.xilinx@...il.com>,
	Daniel Zahka <daniel.zahka@...il.com>,
	Jianbo Liu <jianbol@...dia.com>, Gal Pressman <gal@...dia.com>
Subject: Re: [PATCH 1/2] ethtool: transceiver reset and presence pin control

On Mon, Apr 07, 2025 at 12:35:37PM +0000, Marek Pazdan wrote:
> Signal Definition section (Other signals) of SFF-8636 Spec mentions that
> additional signals like reset and module present may be implemented for
> a specific hardware. There is currently no user space API for control of
> those signals so user space management applications have no chance to
> perform some diagnostic or configuration operations.

How do you tell the kernel to stop managing the SFP? If you hit the
module with a reset from user space, the kernel is going to get
confused. And how are you talking to the module? Are you going to
hijack the i2c device via i2-dev? Again, you need to stop the kernel
from using the device.

Before you go any further, i think you need to zoom out and tell us
the big picture....

    Andrew