netdev - Re: Reporting SFP presence status

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Message-ID: <24cb0fa7-13fc-4463-bb3e-fcd1d13b3fcc@silicom.dk>
Date:   Tue, 22 Dec 2020 07:28:10 +0100
From:   Martin Hundebøll <mhu@...icom.dk>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     netdev <netdev@...r.kernel.org>
Subject: Re: Reporting SFP presence status

Hi Andrew,

On 21/12/2020 16.22, Andrew Lunn wrote:
> On Mon, Dec 21, 2020 at 11:37:55AM +0100, Martin Hundebøll wrote:
>> Hi Andrew,
>>
>> I've browsed the code in drivers/net/phy, but haven't found a place where
>> the SFP module status/change is reported to user-space. Is there a
>> "standard" way to report insert/remove events for SFP modules, or should we
>> just add a custom sysfs attribute to our driver?
> 
> Hi Martin
> 
> There is currently no standard way of notifying user space. But it is
> something which could be added. But it should not be systfs. This
> should be a netlink notification, probably as part of ethtool netlink
> API. Or maybe the extended link info.
> 
> What is your intended use case? Why do you need to know when a module
> has been inserted? It seems like you cannot do too much on such a
> notification. It seems lots of modules don't conform to the standard,
> will not immediately respond on the i2c bus. So ethtool -m is probably
> not going to be useful. You probably need to poll until it does
> respond, which defeats the purpose of having a notification.

You're right; a notification isn't what I need. But a way to query the 
current state of the module would be nice, i.e. using ethtool.

// Martin