mirror of
https://github.com/apache/nuttx.git
synced 2026-05-20 12:33:27 +08:00
LuchianMihai
95efa6f7cf
Currently the mdio communication is part of the monolithic 'full netdevs'. This commit serves as an way to add modularity for the netdevs drivers. A new upperhalf/lowerhalf mdio device comes with this commit that manages the data transfer ofer mdio interface. Signed-off-by: Luchian Mihai <luchiann.mihai@gmail.com>
74 lines
3.6 KiB
ReStructuredText
74 lines
3.6 KiB
ReStructuredText
.. _mdio_bus:
|
|
|
|
.. include:: /substitutions.rst
|
|
|
|
=================
|
|
MDIO Bus Driver
|
|
=================
|
|
|
|
The NuttX MDIO bus driver provides a standardized interface for communicating with Ethernet PHY (Physical Layer) transceivers.
|
|
It employs a classic upper-half/lower-half architecture to abstract hardware-specific logic from the generic MDIO protocol,
|
|
which is currently compliant with Clause 22 of the IEEE 802.3 standard.
|
|
The primary implementation of the upper-half can be found in ``drivers/net/mdio.c``.
|
|
|
|
Driver Architecture
|
|
===================
|
|
|
|
The MDIO driver framework serves as an intermediary layer between a network device driver and the physical bus.
|
|
The intended operational model is ``netdev -> phydev -> mdio``, where the network device communicates with a dedicated PHY driver,
|
|
which in turn uses the MDIO bus driver for low-level hardware access.
|
|
Direct interaction between the network device and the MDIO bus is discouraged.
|
|
|
|
Upper-Half Implementation
|
|
-------------------------
|
|
|
|
The upper-half driver contains the core logic for the MDIO bus, including bus locking mechanisms to ensure safe transactions.
|
|
It exposes a generic API for managing the bus lifecycle and is capable of handling multiple, independent MDIO bus instances concurrently.
|
|
This abstracts implementation details from both the PHY driver and the underlying hardware-specific code.
|
|
|
|
Lower-Half Implementation
|
|
-------------------------
|
|
|
|
A lower-half MDIO driver serves as a thin layer that maps the generic operations defined by the upper-half to hardware-specific register manipulations.
|
|
It is not intended to contain complex logic, but rather to provide a direct translation for bus operations.
|
|
|
|
Implementing a Lower-Half Driver
|
|
================================
|
|
|
|
Integrating MDIO support for new hardware requires the implementation of a lower-half driver.
|
|
The contract between the upper and lower halves is defined in ``include/nuttx/net/mdio.h`` and is centered around two key structures.
|
|
|
|
Key Data Structures
|
|
-------------------
|
|
|
|
1. ``struct mdio_ops_s``: A structure containing function pointers that the lower-half driver must implement to perform hardware-level operations.
|
|
* ``read``: Performs a Clause 22 MDIO read operation.
|
|
* ``write``: Performs a Clause 22 MDIO write operation.
|
|
* ``reset``: An optional function to execute a hardware-specific PHY reset.
|
|
|
|
2. ``struct mdio_lowerhalf_s``: The container for the lower-half instance, which holds a pointer to the ``mdio_ops_s`` vtable
|
|
and an optional private data pointer for the driver's internal state.
|
|
|
|
Registration and Unregistration
|
|
-------------------------------
|
|
|
|
The board-level initialization logic is responsible for instantiating the lower-half driver and registering it with the upper-half via the ``mdio_register()`` function.
|
|
Each call to this function with a distinct lower-half driver creates a new, unique bus handle, allowing the system to manage several MDIO buses concurrently.
|
|
|
|
.. code-block:: c
|
|
|
|
FAR struct mdio_dev_s *mdio_register(FAR struct mdio_lowerhalf_s *lower);
|
|
|
|
This function accepts the lower-half instance and returns an opaque handle (``FAR struct mdio_dev_s *``),
|
|
which is subsequently used by the PHY driver to interact with the bus.
|
|
|
|
When a bus instance is no longer required, it should be deallocated by calling the ``mdio_unregister()`` function to ensure proper cleanup of resources.
|
|
|
|
.. code-block:: c
|
|
|
|
int mdio_unregister(FAR struct mdio_dev_s *dev);
|
|
|
|
This function takes the handle returned by ``mdio_register()`` and releases the associated bus instance.
|
|
|
|
A (mostly) complete reference implementation for a lower-half driver is available in ``arch/arm/src/stm32h7/stm32_mdio.c``.
|