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- .. SPDX-License-Identifier: GPL-2.0 OR GFDL-1.1-no-invariants-or-later
- .. c:namespace:: RC
- .. _lirc-read:
- ***********
- LIRC read()
- ***********
- Name
- ====
- lirc-read - Read from a LIRC device
- Synopsis
- ========
- .. code-block:: c
- #include <unistd.h>
- .. c:function:: ssize_t read( int fd, void *buf, size_t count )
- Arguments
- =========
- ``fd``
- File descriptor returned by ``open()``.
- ``buf``
- Buffer to be filled
- ``count``
- Max number of bytes to read
- Description
- ===========
- :c:func:`read()` attempts to read up to ``count`` bytes from file
- descriptor ``fd`` into the buffer starting at ``buf``. If ``count`` is zero,
- :c:func:`read()` returns zero and has no other results. If ``count``
- is greater than ``SSIZE_MAX``, the result is unspecified.
- The exact format of the data depends on what :ref:`lirc_modes` a driver
- uses. Use :ref:`lirc_get_features` to get the supported mode, and use
- :ref:`lirc_set_rec_mode` set the current active mode.
- The mode :ref:`LIRC_MODE_MODE2 <lirc-mode-mode2>` is for raw IR,
- in which packets containing an unsigned int value describing an IR signal are
- read from the chardev.
- Alternatively, :ref:`LIRC_MODE_SCANCODE <lirc-mode-scancode>` can be available,
- in this mode scancodes which are either decoded by software decoders, or
- by hardware decoders. The :c:type:`rc_proto` member is set to the
- :ref:`IR protocol <Remote_controllers_Protocols>`
- used for transmission, and ``scancode`` to the decoded scancode,
- and the ``keycode`` set to the keycode or ``KEY_RESERVED``.
- Return Value
- ============
- On success, the number of bytes read is returned. It is not an error if
- this number is smaller than the number of bytes requested, or the amount
- of data required for one frame. On error, -1 is returned, and the ``errno``
- variable is set appropriately.
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