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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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4.4 KiB
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ReStructuredText
===============
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Host Side Tools
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===============
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``bitmap_converter.py`` NxWidgets
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=================================
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This script converts from any image type supported by Python imaging library to
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the RLE-encoded format used by NxWidgets.
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RLE (Run Length Encoding) is a very simply encoding that compress quite well
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with certain kinds of images: Images that that have many pixels of the same
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color adjacent on a row (like simple graphics). It does not work well with
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photographic images.
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But even simple graphics may not encode compactly if, for example, they have
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been resized. Resizing an image can create hundreds of unique colors that may
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differ by only a bit or two in the RGB representation. This "color smear" is the
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result of pixel interpolation (and might be eliminated if your graphics software
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supports resizing via pixel replication instead of interpolation).
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When a simple graphics image does not encode well, the symptom is that the
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resulting RLE data structures are quite large. The palette structure, in
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particular, may have hundreds of colors in it. There is a way to fix the graphic
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image in this case. Here is what can be done:
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- Open the original image in GIMP.
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- Select the option to select the number of colors in the image.
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- Pick the smallest number of colors that will represent the image faithfully.
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For most simple graphic images this might be as few as 6 or 8 colors.
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- Save the image as PNG or other lossless format (NOT jpeg).
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- Then generate the image.
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``mkromfsimg.sh``
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=================
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**Q**: Why are there two versions of the script ``mkromfsimg.sh``, one in
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``apps/tools`` and one in ``nuttx/tools``.
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**A**: The version of ``mkromfsimg.sh`` in ``nuttx/tools`` is a generic
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tool to simplify creation of ROMFS file system from any directory containing
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content that you would like to access within the target.
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The version in ``apps/tools``, on the other hand, has a very special purpose.
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It is part of the support that can be used in the KERNEL build mode.
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Processes and Programs in the KERNEL Build
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------------------------------------------
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In the kernel build, there are no tasks. There are only processes and all
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code lives in its own, private address space.
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See :doc:`/os/scheduling/processes_vs_tasks`.
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One consequence of that is that functions like ``task_create()`` and friends
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cannot be used in the KERNEL build mode. Instead, all processes must be loaded
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into a virtual address space from an ELF or NxFLAT file residing in the file
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system. ROMFS is one of many file systems, but one that is particularly usable
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for this purpose in deeply embedded systems.
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KERNEL Build Differences
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------------------------
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In the FLAT and PROTECTED build mode all applications are built into a single
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BLOB, so every symbol must have a unique name to avoid name collisions.
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In the KERNEL build mode, all applications are built at separately linked
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programs that reside in a file system. The entry point to ALL programs is the
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function ``main()``.
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apps/bin
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--------
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When you build the ``apps/`` programs in FLAT or PROTECTED modes, all of the
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object files are put into an archive apps/libapps.a which is, eventually,
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copied to ``nuttx/libs`` and the BLOB is created by linking NuttX archives
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with ``lib/libapps.a``.
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But when you build the ``apps/`` programs in the KERNEL mode, the directory
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``apps/bin`` is created by the top-level apps/Makefile. Each source file is
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compiled, but the object files are not added to ayn archive. Instead, the
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object files are linked into a separate compiled and linked program. Each program
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is then installed at ``apps/bin``.
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apps/tools/mkromfsimg.sh
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------------------------
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When the ``apps/`` kernel build is complete, all of the programs have been installed
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in ``apps/bin``. That is where ``apps/tools/mkromfsimg.sh`` file comes into to play.
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It takes all of the programs in apps/bin and creates a ROMFS file system image
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containing all of the applications. That ROMFS file system image is built into
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the kernel.
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Application Initialization
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--------------------------
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At run time, when the kernel boots, it will mount that ROMFS file system at ``/bin``.
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In the FLAT build mode, the OS boot logic calls ``task_create()`` to start the initial
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task you have configured with ``CONFIG_INIT_ENTRYPOINT``. But in the KERNEL build, something
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different happens. ``CONFIG_INIT_ENTRYPOINT`` is not used. Instead, ``CONFIG_INIT_FILEPATH``
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is used. This will be the name of the program to stared in ``/bin`` to bring up the system.
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