Re: [PATCH 1/3] net: phy: add support to detect 100BASE-T1 capability

quoted

Hi Lucas

Why did you decide to do this, and not add a SUPPORTED_100baseT1?

Could a device support both 100-BASE-T and 100-BASE-T1?  If at some
point we need to differentiate between them, it is going to be
hard. Especially since this is part of the kernel ABI.

Networking and especially PHY isn't really my primary area of
expertise, so excuse my ignorance. My reasoning was that we don't
differentiate between 100BASE-T2 and 100BASE-T4 in the kernel today, so
I thought it was fine to handle T1 the same way.

There are PHYs that can both do regular 100/1000 MBit Ethernet and
100BASE-T1, but definitely not at the same time or over the same
electrical wiring. 100BASE-T1 is really different in that it uses
capacitive coupling, instead of magnetic like on regular Ethernet. So
it is really a board level decision what gets used and is not something
I would expect to change at runtime.

Hi Lucus

http://www.marvell.com/docs/automotive/assets/marvell-automotive-ethernet-88Q5050-product-brief-2017-07.pdf

This is a Marvell 8-port switch. It appears it can switch some of its
ports between T1, TX, xMII, GMII and SGMII.

So maybe an end device is fixed to 100BASE-T1, but it looks like
switches could be more flexible.

So i think we should be able to differentiate between T1 and TX.
We might also need an PHY_INTERFACE_MODE_100BASE_T1.

Florian, what do you think?

   Andrew