[dpdk-dev] Detecting breakout cable usage in xl710 NIC at run time through dpdk driver / i40e interface

[Efstratios Karatzas <efkaratzas@gmail.com>]

Hello dev@dpdk.org

In section "3.3.5.6 Update link mode" of the XL710 datasheet Rev2.4
there is a description on how to change the link mode configuration of
the NIC to enable support for breakout cable (4x10). This can also be
accomplished via the qcu utility provided by intel.

What I am looking for is whether there is way to reliably detect if a
breakout cable is plugged into the XL710 at run time. Keeping also in
mind that the cable could be either in the form of direct attach 4x10
or a standard qsfp + breakout fiber cable.

The end goal here is to automatically change the link mode of the NIC
to the appropriate value without requiring any manual step from user.
For example if direct attach 4x10 cable is plugged into the XL710
port, detect this and switch the link mode configuration to 4x10.

After looking into the i40e_* API and the datasheet, I can't find a
way to reliably perform this kind of check and I'm now wondering if
anyone knows if this is at all possible and if so, how I could go
about performing this kind of check.

Thank you,
Efstratios Karatzas