Re: [RFC net-next v2 1/6] ethtool: Add loopback netlink UAPI definitions

[Maxime Chevallier]

On 09/03/2026 17:45, Andrew Lunn wrote:
>>> +    doc: |
>>> +      Loopback component. Identifies where in the network path the
>>> +      loopback is applied.
>>> +    entries:
>>> +      -
>>> +        name: mac
>>> +        doc: MAC loopback
>>> +      -
>>> +        name: pcs
>>> +        doc: PCS loopback
>>> +      -
>>> +        name: phy
>>> +        doc: PHY loopback
>>> +      -
>>> +        name: module
>>> +        doc: Pluggable module (e.g. CMIS (Q)SFP) loopback
>>
>> Should we also add "serdes" ?
> 
> What is the difference between SERDES and PCS?

By Serdes I mean "generic PHY", but as you state below I don't really
want to use the word "PHY" as it's very prone to confusion with Ethernet
PHYs.

> 
> Maybe we should also make it clear PHY means Ethernet PHY. The Marvell
> Generic PHYs have
> 
> phy-mvebu-a3700-comphy.c:#define COMPHY_DIG_LOOPBACK_EN		0x23
> phy-mvebu-cp110-comphy.c:#define MVEBU_COMPHY_LOOPBACK(n)		(0x88c + (n) * 0x1000)
> 
> which suggests it can also do loopback. We don't want PHY meaning two
> different things.

Agreed,

Maxime