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1.. SPDX-License-Identifier: GPL-2.0 OR GFDL-1.1-no-invariants-or-later2.. c:namespace:: RC3 4.. _lirc-read:5 6***********7LIRC read()8***********9 10Name11====12 13lirc-read - Read from a LIRC device14 15Synopsis16========17 18.. code-block:: c19 20 #include <unistd.h>21 22.. c:function:: ssize_t read( int fd, void *buf, size_t count )23 24Arguments25=========26 27``fd``28 File descriptor returned by ``open()``.29 30``buf``31 Buffer to be filled32 33``count``34 Max number of bytes to read35 36Description37===========38 39:c:func:`read()` attempts to read up to ``count`` bytes from file40descriptor ``fd`` into the buffer starting at ``buf``. If ``count`` is zero,41:c:func:`read()` returns zero and has no other results. If ``count``42is greater than ``SSIZE_MAX``, the result is unspecified.43 44The exact format of the data depends on what :ref:`lirc_modes` a driver45uses. Use :ref:`lirc_get_features` to get the supported mode, and use46:ref:`lirc_set_rec_mode` set the current active mode.47 48The mode :ref:`LIRC_MODE_MODE2 <lirc-mode-mode2>` is for raw IR,49in which packets containing an unsigned int value describing an IR signal are50read from the chardev.51 52Alternatively, :ref:`LIRC_MODE_SCANCODE <lirc-mode-scancode>` can be available,53in this mode scancodes which are either decoded by software decoders, or54by hardware decoders. The :c:type:`rc_proto` member is set to the55:ref:`IR protocol <Remote_controllers_Protocols>`56used for transmission, and ``scancode`` to the decoded scancode,57and the ``keycode`` set to the keycode or ``KEY_RESERVED``.58 59Return Value60============61 62On success, the number of bytes read is returned. It is not an error if63this number is smaller than the number of bytes requested, or the amount64of data required for one frame. On error, -1 is returned, and the ``errno``65variable is set appropriately.66