Re: [net-next PATCH v6 03/10] net: pcs: Add subsystem

On 6/10/25 20:24, Randy Dunlap wrote:

Hi,

quoted

diff --git a/Documentation/networking/pcs.rst b/Documentation/networking/pcs.rst
new file mode 100644
index 000000000000..4b41ba884160
--- /dev/null
+++ b/Documentation/networking/pcs.rst

@@ -0,0 +1,102 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+=============
+PCS Subsystem
+=============
+
+The PCS (Physical Coding Sublayer) subsystem handles the registration and lookup
+of PCS devices. These devices contain the upper sublayers of the Ethernet
+physical layer, generally handling framing, scrambling, and encoding tasks. PCS
+devices may also include PMA (Physical Medium Attachment) components. PCS
+devices transfer data between the Link-layer MAC device, and the rest of the
+physical layer, typically via a serdes. The output of the serdes may be
+connected more-or-less directly to the medium when using fiber-optic or
+backplane connections (1000BASE-SX, 1000BASE-KX, etc). It may also communicate
+with a separate PHY (such as over SGMII) which handles the connection to the
+medium (such as 1000BASE-T).
+
+Looking up PCS Devices
+----------------------
+
+There are generally two ways to look up a PCS device. If the PCS device is
+internal to a larger device (such as a MAC or switch), and it does not share an
+implementation with an existing PCS, then it does not need to be registered with
+the PCS subsystem. Instead, you can populate a :c:type:`phylink_pcs`
+in your probe function. Otherwise, you must look up the PCS.
+
+If your device has a :c:type:`fwnode_handle`, you can add a PCS using the
+``pcs-handle`` property::
+
+    ethernet-controller {
+        // ...
+        pcs-handle = <&pcs>;
+        pcs-handle-names = "internal";
+    };
+
+Then, during your probe function, you can get the PCS using :c:func:`pcs_get`::

It's preferable to use                               PCS using pcs_get()::
instead of the :c:func: notation to make the .rst file more human-readable.
They produce the same generated output.

If you find this syntax useful, then you should update
Documentation/doc-guide/{kernel-doc,sphinx}.rst. I did not use it
because it I did not know about it because it is not documented.

--Sean