Re: [PATCH net-next v2 2/3] net: ethtool: Add impedance mismatch result code to cable test

[Paweł Dembicki]

pt., 29 mar 2024 o 03:02 Jakub Kicinski <kuba@xxxxxxxxxx> napisał(a):
>
> On Wed, 27 Mar 2024 17:29:13 +0100 Pawel Dembicki wrote:
> > This commit introduces a new result code:
> > ETHTOOL_A_CABLE_RESULT_CODE_IMPEDANCE_MISMATCH
> > which represents the results of a cable test indicating abnormal impedance.
>
> I'm not a cable expert but going purely by the language
> abnormal != mismatch. Mismatch indicates there are two
> values we are comparing.

Impedance mismatch can be detected because some parts of the cable may
have different (abnormal) impedance, causing reflections at those
points. Ethernet cables should have a characteristic impedance of 100
Ohms, so any mismatch from this value is considered abnormal. I can
provide a rephrased version if the commit description was not detailed
enough.