netdev - Re: [RFC PATCH net-next 1/3] net: rtnetlink: Add link-down reason to RTNL messages

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Date:   Mon, 18 Mar 2019 13:47:34 +0000
From:   Petr Machata <petrm@...lanox.com>
To:     Andrew Lunn <andrew@...n.ch>
CC:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Jiri Pirko <jiri@...lanox.com>,
        Ido Schimmel <idosch@...lanox.com>,
        "davem@...emloft.net" <davem@...emloft.net>,
        Tariq Toukan <tariqt@...lanox.com>,
        "jakub.kicinski@...ronome.com" <jakub.kicinski@...ronome.com>,
        "stephen@...workplumber.org" <stephen@...workplumber.org>
Subject: Re: [RFC PATCH net-next 1/3] net: rtnetlink: Add link-down reason to
 RTNL messages


Andrew Lunn <andrew@...n.ch> writes:

> On Mon, Mar 18, 2019 at 01:15:41PM +0000, Petr Machata wrote:
>> 
>> Andrew Lunn <andrew@...n.ch> writes:
>> 
>> >> +enum rtnl_link_down_reason_major {
>> >> +	RTNL_LDR_OTHER,
>> >
>> > Does 'other' make any sense? Seem better to just not report anything
>> > at all, or add a comment that more reasons should be added at the end
>> > to reflect whatever the hardware or software can determine.
>> 
>> You still have the minor code to give you some information.
>> 
>> >> +	RTNL_LDR_NO_CABLE,
>> >> +	RTNL_LDR_UNSUPPORTED_CABLE,
>> >> +	RTNL_LDR_AUTONEG_FAILURE,
>> >> +	RTNL_LDR_NO_LINK_PARTNER,
>> >> +	RTNL_LDR_LINK_TRAINING_FAILURE,
>> >> +	RTNL_LDR_LOGICAL_MISMATCH,
>> >> +	RTNL_LDR_REMOTE_FAULT,
>> >> +	RTNL_LDR_BAD_SIGNAL_INTEGRITY,
>> >> +	RTNL_LDR_CALIBRATION_FAILURE,
>> >> +	RTNL_LDR_POWER_BUDGET_EXCEEDED,
>> >> +};
>> >
>> > What about SFP cage empty?, i.e. no SFP, SFP+ module in the cage?  An
>> 
>> No cable? Maybe the name needs to change...
>
> An SFP module, and the cable plugged into it via LC connectors, are
> physically different things. And you can also have an SFP with an RJ45
> for 1G copper. I know at higher speeds they can be inseparable, but
> this needs to be a generic API and also work with them being two
> separate things.

Understood.

>> 
>> > SFP can also report LOS. That does not appear to be any of the above.
>> > Or that the core SFP code has been unable to read the EEPROM? We have
>> 
>> My assumption was that cable with unreadable EEPROM is simply a bad
>> cable. Does the admin actually care which particular part of the cable
>> is at fault?
>
> Yes. I throw away the SFP module, because its EEPROM is broke, but
> don't need to replace the 1KM of fibre cable, or 100m of Cat 6a copper
> cable. Classic example would be fibre to the home.

OK, gotcha.