Subject: Re: [PATCH ethtool 2/2] Ethtool: Implements PHY Loopback

From: "Allan W. Nielsen" <[email-masked]>
Date: Mon, 28 Nov 2016 20:34:59 +0100

On 28/11/16 09:56, Florian Fainelli wrote:
> On 11/28/2016 05:25 AM, Allan W. Nielsen wrote:
> > From: Raju Lakkaraju <[email-masked]>
> >
> > Add loopback in ethtool tunables to access PHY drivers.
> >
> > Ethtool Help: ethtool -h for PHY tunables
> >     ethtool --set-phy-tunable DEVNAME      Set PHY tunable
> >                 [ loopback off|near|far|extn ]
> >     ethtool --get-phy-tunable DEVNAME      Get PHY tunable
> >                 [ loopback ]
> >
> > Ethtool ex:
> >   ethtool --set-phy-tunable eth0 loopback near
> >   ethtool --set-phy-tunable eth0 loopback far
> >   ethtool --set-phy-tunable eth0 loopback extn
> >   ethtool --set-phy-tunable eth0 loopback off
> >
> >   ethtool --get-phy-tunable eth0 loopback
> >
> > Signed-off-by: Raju Lakkaraju <[email-masked]>
> > Signed-off-by: Allan W. Nielsen <[email-masked]>
> > ---
> 
> > +Near-End Loopback:
> > +Transmitted data (TXD) is looped back in the PCS block onto the receive data
> > +signal (RXD). When Near-End loopback enable, no data is transmitted over
> > +the network. no data receive from the network.
> 
> This is also known as the local loopback test mode, right?
Yes - Traffic transmitted/generated by the host list loopback to the
host instead of transmitting it on the wire.

> > +
> > +Far-End Loopback:
> > +This loopback is a special test mode to allow testing the PHY from link
> > +partner side. In this mode data that is received from the link partner pass
> > +through the PHY's receiver, looped back on the MII and transmitted back to
> > +the link partner.
> 
> And this is the remote loopback mode.
Yes - Traffic receiwed on the "wire" is transmitted back on the wire.

> > +
> > +External Loopback:
> > +An RJ45 loopback cable can be used to route the transmit signals an the
> > +output of the trnsformer back to the receiver inputs and this loopback will
> > +work at either 10 or 100 or 1000 Mbps speed.
> > +RJ45 Loopback cable created by conncting pin 1 to pin 3 and connecting pin
> > +2 to pin 6.
> 
> OK, this name makes sense to me, but for the two other names, we need to
> use a terminology that is clearer to the reader and/or people familiar
> and targeted at using this feature (e.g: in a lab or during manufacturing).
Sure, we can find better names and/or improve the documentation. But
before jumping to that, then it is properly a good idea to agree on
the overall concept.

We will get back to the naming when we agree on the other parts.

/Allan