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Date:   Tue, 12 Dec 2023 15:35:12 +0100
From:   Maxime Chevallier <maxime.chevallier@bootlin.com>
To:     Daniel Golle <daniel@makrotopia.org>
Cc:     Andrew Lunn <andrew@lunn.ch>,
        Heiner Kallweit <hkallweit1@gmail.com>,
        Russell King <linux@armlinux.org.uk>,
        "David S. Miller" <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH net] net: phy: skip LED triggers on PHYs on SFP modules
Message-ID: <20231212153512.67a7a35b@device.home>
In-Reply-To: <102a9dce38bdf00215735d04cd4704458273ad9c.1702339354.git.daniel@makrotopia.org>
References: <102a9dce38bdf00215735d04cd4704458273ad9c.1702339354.git.daniel@makrotopia.org>
Organization: Bootlin
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Hi Daniel

On Tue, 12 Dec 2023 00:05:35 +0000
Daniel Golle <daniel@makrotopia.org> wrote:

> Calling led_trigger_register() when attaching a PHY located on an SFP
> module potentially (and practically) leads into a deadlock.
> Fix this by not calling led_trigger_register() for PHYs localted on SFP
> modules as such modules actually never got any LEDs.

While I don't have a fix for this issue, I think your justification
isn't good. This isn't about having LEDs on the module or not, but
rather the PHY triggering LED events for LEDS that can be located
somewhere else on the system (like the front pannel of a switch).

So I think it would be wiser to avoid the deadlock with a proper
analysis of what the locking scheme does. Maybe Andrew or Russell
have a better vision of what's going-on here, I tried to dive into
it but it doesn't look straightfoward to me :(

Maxime