nuttx/Documentation/components/drivers/character/index.rst

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.. _chardev:
========================
Character Device Drivers
========================
Character device drivers have these properties:
- ``include/nuttx/fs/fs.h``. All structures and APIs needed
to work with character drivers are provided in this header
file.
- ``struct file_operations``. Each character device driver
must implement an instance of ``struct file_operations``. That
structure defines a call table with the following methods:
- ``int register_driver(const char *path, const struct file_operations *fops, mode_t mode, void *priv);``.
Each character driver registers itself by calling
``register_driver()``, passing it the ``path`` where it will
appear in the :ref:`pseudo file system <file_system_overview>` and it's
initialized instance of ``struct file_operations``.
- **User Access**. After it has been registered, the character
driver can be accessed by user code using the standard driver
operations including
``open()``, ``close()``, ``read()``, ``write()``, etc.
- **Specialized Character Drivers**. Within the common character
driver framework, there are different specific varieties of
*specialized* character drivers. The unique requirements of the
underlying device hardware often mandates some customization of
the character driver. These customizations tend to take the
form of:
- Device-specific ``ioctl()`` commands used to performed
specialized operations on the device. These ``ioctl()`` will
be documented in header files under ``include/nuttx`` that
detail the specific device interface.
- Specialized I/O formats. Some devices will require that
``read()`` and/or ``write()`` operations use data conforming
to a specific format, rather than a plain stream of bytes.
These specialized I/O formats will be documented in header
files under ``include/nuttx`` that detail the specific
device interface. The typical representation of the I/O
format will be a C structure definition.
The specialized character drivers support by NuttX are
documented in the following paragraphs.
- **Examples**: ``drivers/dev_null.c``, ``drivers/fifo.c``,
``drivers/serial.c``, etc.
.. toctree::
:caption: Supported Drivers
serial.rst
touchscreen.rst
analog.rst
pwm.rst
can.rst
quadrature.rst
timer.rst
rtc.rst
watchdog.rst
keypad.rst
note.rst
foc.rst