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