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The documentation grew one page at a time, so the tree follows the
history of who wrote what and not the shape of NuttX. Scheduling is
spread over three places, a driver page can sit above the subsystem
that owns it, and the front page lists everything at the same level.
That is a lot to face when all you want to know is where the scheduler
lives.
This change files every page under the code it describes. It is a move,
not a rewrite: outside the ten pages named below, every page keeps the
text that is already in master, and no page's text is deleted.
What it does:
* Groups the table of contents into nine chapters.
* Moves the OS subsystems under os/: scheduling, memory, drivers,
filesystem, networking, IPC, interrupts, libs, time.
* Renames the platform pages to the names the source tree uses, and
derives their tags from the tree instead of by hand.
* Splits guides/ by subject.
* Adds Documentation/redirects.py, with a rule for every page that left
its old path, so old URLs keep working. The redirect page also carries
a link's #anchor across to the new page.
Ten pages have text that is new or rewritten. Nine of them are the
landing page of a chapter, which has to exist for the new structure:
index the front page
os/index OS Design
os/scheduling/index Scheduling
os/interrupts/index Interrupts
os/ipc/index IPC
os/time/index Time and timers
about/index About
developing/index Developing NuttX
ReleaseNotes/index Release notes
The tenth is os/libs/libbuiltin, the only page here with technical
content: libs/libbuiltin/ had no page at all. Five SVG diagrams come
with these pages, hand-written XML with no editor metadata.
Nothing outside Documentation/ is touched.
How it was checked:
* Sphinx builds with -W: no warnings, and no document left outside a
toctree.
* A script, offered in the PR, proves the narrow claim this rests on.
For every page outside the ten named above it erases what a move
touches -- link target, path, tag line, toctree block, table border --
from the whole old text and the whole new text, and requires the two
to be byte for byte identical. It also requires every sentence of a
deleted page to turn up somewhere, and every page that left its old
path to have a redirect, from a URL that existed, to where its content
went. It exits non-zero and names the page if any of that is not true,
and it tests added pages too, so forgetting to declare one cannot make
it pass.
* An independent audit checked 133 factual claims on these ten pages
against the tree, one shell command per claim: 130 confirmed, 1
refuted and fixed here, 2 not checkable.
* tools/checkpatch.sh is clean over the range.
The diff is large because moving a page changes every link that points
to it. Most of it is pure renames, and board pages that gained one tag
line.
Assisted-by: Claude:claude-opus-5
73 lines
3.6 KiB
ReStructuredText
73 lines
3.6 KiB
ReStructuredText
.. _mdio_bus:
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.. include:: /substitutions.rst
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=================
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MDIO Bus Driver
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=================
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The NuttX MDIO bus driver provides a standardized interface for communicating with Ethernet PHY (Physical Layer) transceivers.
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It employs a classic upper-half/lower-half architecture to abstract hardware-specific logic from the generic MDIO protocol,
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which is currently compliant with Clause 22 of the IEEE 802.3 standard.
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The primary implementation of the upper-half can be found in ``drivers/net/mdio.c``.
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Driver Architecture
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===================
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The MDIO driver framework serves as an intermediary layer between a network device driver and the physical bus.
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The intended operational model is ``netdev -> phydev -> mdio``, where the network device communicates with a dedicated PHY driver,
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which in turn uses the MDIO bus driver for low-level hardware access.
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Direct interaction between the network device and the MDIO bus is discouraged.
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Upper-Half Implementation
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-------------------------
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The upper-half driver contains the core logic for the MDIO bus, including bus locking mechanisms to ensure safe transactions.
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It exposes a generic API for managing the bus lifecycle and is capable of handling multiple, independent MDIO bus instances concurrently.
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This abstracts implementation details from both the PHY driver and the underlying hardware-specific code.
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Lower-Half Implementation
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-------------------------
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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.
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It is not intended to contain complex logic, but rather to provide a direct translation for bus operations.
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Implementing a Lower-Half Driver
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================================
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Integrating MDIO support for new hardware requires the implementation of a lower-half driver.
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The contract between the upper and lower halves is defined in ``include/nuttx/net/mdio.h`` and is centered around two key structures.
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Key Data Structures
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-------------------
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1. ``struct mdio_ops_s``: A structure containing function pointers that the lower-half driver must implement to perform hardware-level operations.
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* ``read``: Performs a Clause 22 MDIO read operation.
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* ``write``: Performs a Clause 22 MDIO write operation.
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* ``reset``: An optional function to execute a hardware-specific PHY reset.
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2. ``struct mdio_lowerhalf_s``: The container for the lower-half instance, which holds a pointer to the ``mdio_ops_s`` vtable
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and an optional private data pointer for the driver's internal state.
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Registration and Unregistration
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-------------------------------
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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.
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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.
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.. code-block:: c
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FAR struct mdio_dev_s *mdio_register(FAR struct mdio_lowerhalf_s *lower);
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This function accepts the lower-half instance and returns an opaque handle (``FAR struct mdio_dev_s *``),
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which is subsequently used by the PHY driver to interact with the bus.
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When a bus instance is no longer required, it should be deallocated by calling the ``mdio_unregister()`` function to ensure proper cleanup of resources.
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.. code-block:: c
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int mdio_unregister(FAR struct mdio_dev_s *dev);
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This function takes the handle returned by ``mdio_register()`` and releases the associated bus instance.
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A (mostly) complete reference implementation for a lower-half driver is available in ``arch/arm/src/stm32h7/stm32_mdio.c``.
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