Sep 9 – 11, 2019
Europe/Lisbon timezone

Ethernet Cable Diagnostic using Netlink Ethtool API

Sep 10, 2019, 5:45 PM
Floriana/room-I (Corinthia Hotel Lisbon)


Corinthia Hotel Lisbon



Andrew Lunn


Many Ethernet PHYs contain hardware to perform diagnostics of the
Ethernet cable. Breaks in the cable and shorts within a twisted pair
or to other pairs can be detected, and an estimate to the length along
the cable to the fault can be made. The talk will explain, at a high
level, how such diagnostics work, sending pulses down the cables and
looking for reflections. There is no standardization on such
diagnostics, and what information the PHY reports varies between
vendors. The ongoing work to allow ethtool to make use of a netlink
socket makes the ethtool API much more flexiable. This flexibility has
been used to provide a generic API to request a PHY performs
diagnostics tests and to report the results. Some aspects of this API
will be discussed, using the Marvell PHYs as examples. The talk aims
to spread knowledge on this work and encourage driver writers to
implement diagnostics for other PHYs.

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