lirc-read.rst (1804B)
1.. SPDX-License-Identifier: GPL-2.0 OR GFDL-1.1-no-invariants-or-later 2.. c:namespace:: RC 3 4.. _lirc-read: 5 6*********** 7LIRC read() 8*********** 9 10Name 11==== 12 13lirc-read - Read from a LIRC device 14 15Synopsis 16======== 17 18.. code-block:: c 19 20 #include <unistd.h> 21 22.. c:function:: ssize_t read( int fd, void *buf, size_t count ) 23 24Arguments 25========= 26 27``fd`` 28 File descriptor returned by ``open()``. 29 30``buf`` 31 Buffer to be filled 32 33``count`` 34 Max number of bytes to read 35 36Description 37=========== 38 39:c:func:`read()` attempts to read up to ``count`` bytes from file 40descriptor ``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 driver 45uses. Use :ref:`lirc_get_features` to get the supported mode, and use 46: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 are 50read 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, or 54by hardware decoders. The :c:type:`rc_proto` member is set to the 55: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 Value 60============ 61 62On success, the number of bytes read is returned. It is not an error if 63this number is smaller than the number of bytes requested, or the amount 64of data required for one frame. On error, -1 is returned, and the ``errno`` 65variable is set appropriately.