mirror of https://gitee.com/openkylin/linux.git
77 lines
2.1 KiB
ReStructuredText
77 lines
2.1 KiB
ReStructuredText
.. Permission is granted to copy, distribute and/or modify this
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.. document under the terms of the GNU Free Documentation License,
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.. Version 1.1 or any later version published by the Free Software
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.. Foundation, with no Invariant Sections, no Front-Cover Texts
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.. and no Back-Cover Texts. A copy of the license is included at
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.. Documentation/media/uapi/fdl-appendix.rst.
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..
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.. TODO: replace it to GFDL-1.1-or-later WITH no-invariant-sections
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.. _lirc-read:
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***********
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LIRC read()
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***********
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Name
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====
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lirc-read - Read from a LIRC device
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Synopsis
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========
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.. code-block:: c
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#include <unistd.h>
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.. c:function:: ssize_t read( int fd, void *buf, size_t count )
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:name: lirc-read
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Arguments
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=========
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``fd``
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File descriptor returned by ``open()``.
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``buf``
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Buffer to be filled
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``count``
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Max number of bytes to read
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Description
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===========
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:ref:`read() <lirc-read>` attempts to read up to ``count`` bytes from file
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descriptor ``fd`` into the buffer starting at ``buf``. If ``count`` is zero,
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:ref:`read() <lirc-read>` returns zero and has no other results. If ``count``
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is greater than ``SSIZE_MAX``, the result is unspecified.
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The exact format of the data depends on what :ref:`lirc_modes` a driver
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uses. Use :ref:`lirc_get_features` to get the supported mode, and use
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:ref:`lirc_set_rec_mode` set the current active mode.
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The mode :ref:`LIRC_MODE_MODE2 <lirc-mode-mode2>` is for raw IR,
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in which packets containing an unsigned int value describing an IR signal are
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read from the chardev.
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Alternatively, :ref:`LIRC_MODE_SCANCODE <lirc-mode-scancode>` can be available,
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in this mode scancodes which are either decoded by software decoders, or
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by hardware decoders. The :c:type:`rc_proto` member is set to the
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:ref:`IR protocol <Remote_controllers_Protocols>`
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used for transmission, and ``scancode`` to the decoded scancode,
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and the ``keycode`` set to the keycode or ``KEY_RESERVED``.
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Return Value
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============
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On success, the number of bytes read is returned. It is not an error if
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this number is smaller than the number of bytes requested, or the amount
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of data required for one frame. On error, -1 is returned, and the ``errno``
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variable is set appropriately.
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