On Fri, Dec 15, 2023 at 06:12:35PM +0100, Maxime Chevallier wrote:

...

+UAPI
+====
+
+There exist a set of netlink commands to query the link topology from userspace,
+see ``Documentation/networking/ethtool-netlink.rst``.
+
+The whole point of having a topology representation is to assign the phyindex
+field in :c:type:`struct phy_device <phy_device>`. This index is reported to
+userspace using the ``ETHTOOL_MSG_PHY_GET`` ethtnl command. Performing a DUMP operation
+will result in all PHYs from all net_device being listed. The DUMP command
+accepts either a ``ETHTOOL_A_HEADER_DEV_INDEX`` or ``ETHTOOL_A_HEADER_DEV_NAME``
+to be passed in the request to filter the DUMP to a single net_device.
+
+The retrieved index can then be passed as a request parameter using the
+``ETHTOOL_A_HEADER_PHY_INDEX`` field in the following ethnl commands :
+
+* ``ETHTOOL_MSG_STRSET_GET`` to get the stats strig set from a given PHY

string

+* ``ETHTOOL_MSG_CABLE_TEST_ACT`` and ``ETHTOOL_MSG_CABLE_TEST_ACT``, to perform
+  cable testing on a given PHY on the link (most likely the outermost PHY)
+* ``ETHTOOL_MSG_PSE_SET`` and ``ETHTOOL_MSG_PSE_GET`` for PHY-controlled PoE and PSE settings
+* ``ETHTOOL_MSG_PLCA_GET_CFG``, ``ETHTOOL_MSG_PLCA_SET_CFG`` and ``ETHTOOL_MSG_PLCA_GET_STATUS``
+  to set the PLCA (Physical Layer Collision Avoidance) parameters
+
+Note that the PHY index can be passed to other requests, which will silently
+ignore it if present and irrelevant.
-- 
2.43.0