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f6ecf80ebb
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
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==================================
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Naming and Header File Conventions
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==================================
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- **Common Microprocessor Interfaces**. Any interface that is
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common to all microprocessors should be prefixed with ``up_``
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and prototyped in ``include/nuttx/arch.h``. The definitions in
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that header file provide the common interface between NuttX and
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the architecture-specific implementation in ``arch/``.
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``up_`` is supposed to stand for microprocessor; the ``u``
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is like the Greek letter micron: μ. So it would be ``μP``
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which is a common shortening of the word microprocessor. I
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don't like that name very much. I wish I would have used a
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more obvious prefix like ``arch_`` instead -- then I would
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not have to answer this question so often.
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- **Microprocessor-Specific Interfaces**. An interface which is
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unique to a certain microprocessor should be prefixed with the
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name of the microprocessor, for example ``stm32_``, and be
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prototyped in some header file in the ``arch/`` directories.
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There is also a ``arch/<architecture>/include/<chip>/chip.h``
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header file that can be used to communicate other
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microprocessor-specific information between the board logic and
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even application logic. Application logic may, for example,
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need to know specific capabilities of the chip. Prototypes in
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that ``chip.h`` header file should follow the
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microprocessor-specific naming convention.
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- **Common Board Interfaces**. Any interface that is common to
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all boards should be prefixed with ``board_`` and should also
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be prototyped in ``include/nuttx/board.h``. These ``board_``
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definitions provide the interface between the board-level logic
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and the commaon and architecture-specific logic.
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- **Board-Specific Interfaces**. Any interface which is unique to
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a board should be prefixed with the board name, for example
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``stm32f4discovery_``. Sometimes the board name is too long so
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``stm32_`` would be okay too. These should be prototyped in
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``boards/<arch>/<chip>/<board>/src/<board>.h`` and should not
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be used outside of that directory since board-specific
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definitions have no meaning outside of the board directory.
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- **Scope of Inclusions**. Header files are made accessible to
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internal OS logic and to applications through symbolic links
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and through *include paths* that are provided to the C/C++
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compiler. Through these include paths, the NuttX build system
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also enforces modularity in the design. For example, one
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important design principle is architectural *layering*. In this
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case I am referring to the OS as layered into application
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interface, common internal OS logic, and lower level
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platform-specific layers. The platform-specific layers all
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reside in the either ``arch/`` sub-directories or the
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``boards/`` subdirectories: The former sub-directories are
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reserved for microcontroller-specific logic and the latter for
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board-specific logic.
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In the strict, layered NuttX architecture, the upper level OS
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services are always available to platform-specific logic.
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However, the opposite is *not* true: Common OS logic must never
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have any dependency on the lower level platform-specific code.
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The OS logic must be totally agnostic about its hardware
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environment. Similarly, microcontroller-specific logic was be
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completely ignorant of board-specific logic.
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This strict layering is enforced in the NuttX build system by
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controlling the compiler include paths: Higher level code can
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never include header files from either of the
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platform-specific source directories; microcontroller-specific
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code can never include header files from the board-specific
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source directories. The board-specific directories are, then,
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at the bottom of the layered hierarchy.
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An exception to these inclusion restrictions is the
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platform-specific *include/*. These are made available to
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higher level OS logic. The microcontroller-specific include
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directory will be linked at ``include/arch/chip`` and, hence,
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can be included like ``#include <arch/hardware/chip.h``.
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Similarly, the board-specific include directory will be linked
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at ``include/arch/board`` and, hence, can be included like
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``#include <arch/board/board.h``.
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Keeping in the spirit of the layered architecture, these
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publicly visible header files must *not* export
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platform-specific definitions; Only platform-specific
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realizations of standardized declarations should be visible.
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Those *standardized declarations* should appear in common
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header files such as those provided by ``include/nuttx/arch.h``
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and ``include/nuttx/board.h``. Similarly, these publicly
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visible header file must *not* include files that reside in the
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inaccessible platform-specific source directories. For example,
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the board-specific
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``boards/<arch>/<chip>/<board>/include/board.h`` header file
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must never include microcontroller-specific header files that
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reside in ``arch/<arch>/src/<mcu>``. That practice will cause
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inclusion failures when the publicly visible file is included
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in common logic outside of the platform-specific source
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directories.
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