[PATCH net-next 00/13] net: phy_port: SFP modules representation and phy_port listing

Maxime Chevallier
2026-01-27T13:42:21Z

Hello everyone,

This series is another step towards dealing with multi-port interfaces.

It build on the recent addition of phy_port representation to enable
listing the front-facing ports of an interface. For now, we don't control
these ports, we merely list their presence and their capabilities.

As the most common use-case of multi-port interfaces is combo-ports that
provide both RJ45 and SFP connectors on a single MAC, there's a lot of
SFP stuff in this series.

This series is in 2 main parts. The first one aims at representing the
SFP cages and modules using phy_port, as combo-ports with RJ45 + SFP are
by far the most common cases for multi-connector setups.

The second part is the netlink interface to list those ports, now that
most use-cases are covered.

Let's see what we can do with some examples of the new ethtool API :

- Get MII interfaces supported by an empty SFP cage :

# ethtool --show-ports eth3

Port for eth3:
Port id: 1
Occupied: no
Supported MII interfaces : sgmii, 1000base-x, 2500base-x
Port type: sfp

- Get Combo-ports supported modes, on each port :

# ethtool --show-ports eth0

Port for eth0:
Port id: 1
Occupied: no
Supported link modes: 10baseT/Half 10baseT/Full
100baseT/Half 100baseT/Full
1000baseT/Half 1000baseT/Full
10000baseT/Full
2500baseT/Full
5000baseT/Full
Port type: mdi

Port for eth0:
Port id: 2
Occupied: no
Supported MII interfaces : 10gbase-r
Port type: sfp

- Get Achievable linkmodes on a SFP module (combo port with a DAC in the
SFP cage)

# ethtool --show-ports eth1

Port for eth1:
Port id: 1
Occupied: no
Supported link modes: 10baseT/Half 10baseT/Full
100baseT/Half 100baseT/Full
1000baseT/Half 1000baseT/Full
10000baseT/Full
2500baseT/Full
5000baseT/Full
Port type: mdi

Port for eth1:
Port id: 2
Occupied: yes
Supported MII interfaces : 10gbase-r
Port type: sfp

Port for eth1:
Port id: 3
Occupied: no
Supported link modes: 10000baseCR/Full
Port type: mdi

Note that here, we have 3 ports :
- The Copper port
- The SFP Cage itself, marked as 'occupied'
- The SFP module

This series builds on top of phy_port and phy_link_topology to allow
tracking the ports of an interface. We maintain a list of supported
linkmodes/interfaces on each port, which allows for fine-grained
reporting of each port's capability.

What this series doesn't do :
- We don't support selecting which port is active. This is the next step.
- We only support PHY-driven combo ports. The end-goal of this whole
journey that started with phy_link_topology is to get support for MII
muxes, such as the one we have on the Turris Omnia. This will eventually
be upstreamed as well.

If you want to play around with it, here's [1] the patched ethtool that I've
been using to produce the outputs above.

Thanks !

Maxime

[1] : https://github.com/minimaxwell/ethtool/tree/mc/ethtool_port

Maxime Chevallier (13):
net: phy: phy_port: Correctly recompute the port's linkmodes
net: phy: phy_link_topology: Add a helper for opportunistic alloc
net: phy: phy_link_topology: Track ports in phy_link_topology
net: phylink: Register a phy_port for MAC-driven SFP busses
net: phy: Create SFP phy_port before registering usptream
net: sfp: Add a sfp-bus ops when connecting a module without PHY
net: phy: Represent PHY-less SFP modules with phy_port
net: phylink: Represent PHY-less SFP modules with phy_port
net: phy: phy_port: Store information about a MII port's occupancy
net: phy: phy_link_topology: Add a helper to retrieve ports
net: phy: store phy_modes in a static array
netlink: specs: Add ethernet port listing with ethtool
net: ethtool: Introduce ethtool command to list ports

Documentation/netlink/specs/ethtool.yaml | 50 +++
Documentation/networking/ethtool-netlink.rst | 35 ++
MAINTAINERS | 1 +
drivers/net/phy/phy-caps.h | 2 +
drivers/net/phy/phy_caps.c | 26 ++
drivers/net/phy/phy_device.c | 104 ++++-
drivers/net/phy/phy_link_topology.c | 80 +++-
drivers/net/phy/phy_port.c | 9 +-
drivers/net/phy/phylink.c | 121 ++++++
drivers/net/phy/sfp-bus.c | 20 +
drivers/net/phy/sfp.c | 12 +
drivers/net/phy/sfp.h | 2 +
include/linux/phy.h | 88 +----
include/linux/phy_link_topology.h | 34 ++
include/linux/phy_port.h | 5 +
include/linux/sfp.h | 5 +
.../uapi/linux/ethtool_netlink_generated.h | 19 +
net/ethtool/Makefile | 2 +-
net/ethtool/common.c | 44 +++
net/ethtool/netlink.c | 11 +
net/ethtool/netlink.h | 5 +
net/ethtool/port.c | 373 ++++++++++++++++++
22 files changed, 943 insertions(+), 105 deletions(-)
create mode 100644 net/ethtool/port.c

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2.49.0