netdev - RE: Link down reasons

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Message-ID: <AM0PR0502MB38267B345D7829A00790285DD78E0@AM0PR0502MB3826.eurprd05.prod.outlook.com>
Date:   Thu, 28 May 2020 05:56:47 +0000
From:   Amit Cohen <amitc@...lanox.com>
To:     Andrew Lunn <andrew@...n.ch>
CC:     mlxsw <mlxsw@...lanox.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "o.rempel@...gutronix.de" <o.rempel@...gutronix.de>
Subject: RE: Link down reasons

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

>On Wed, May 27, 2020 at 03:41:22PM +0000, Amit Cohen wrote:
>> Hi Andrew,
>> 
>> We are planning to send a set that exposes link-down reason in ethtool.
>> 
>> It seems that the ability of your set “Ethernet cable test support” 
>> can be integrated with link-down reason.
>> 
>>  
>> 
>> The idea is to expose reason and subreason (if there is):
>> 
>> $ ethtool ethX
>> 
>> …
>> 
>> Link detected: no (No cable) // No sub reason
>> 
>>  
>> 
>> $ ethtool ethY
>> 
>> Link detected: no (Autoneg failure, No partner detected)
>> 
>>  
>> 
>> Currently we have reason “cable issue” and subreasons “unsupported 
>> cable” and “shorted cable”.
>> 
>> The mechanism of cable test can be integrated and allow us report “cable issue”
>> reason and “shorted cable” subreason.
>
>Hi Amit
>
>I don't really see them being combinable. First off, your API seems too limiting. How do you say which pair is broken, or at what distance? What about open cable, as opposed to shorted cable?
>
>So i would suggest:
>
>Link detected: no (cable issue)
>
>And then recommend the user uses ethtool --cable-test to get all the details, and you have a much more flexible API to provide as much or as little information as you have.
>
>   Andrew

Thanks!
Link-down reason has to consider cable-test or not? In order to report "cable issue", we assume that the driver implemented link-down reason in addition to cable-test?
I'm asking about PHY driver for example that implemented cable-test and not link-down reason, so according to cable-test we should report "cable issue" as a link-down reason or do not expose reason here?