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 *********** 7 LIRC read() 8 *********** 9 10 Name 11 ==== 12 13 lirc-read - Read from a LIRC device 14 15 Synopsis 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 24 Arguments 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 36 Description 37 =========== 38 39 :c:func:`read()` attempts to read up to ``count`` bytes from file 40 descriptor ``fd`` into the buffer starting at ``buf``. If ``count`` is zero, 41 :c:func:`read()` returns zero and has no other results. If ``count`` 42 is greater than ``SSIZE_MAX``, the result is unspecified. 43 44 The exact format of the data depends on what :ref:`lirc_modes` a driver 45 uses. Use :ref:`lirc_get_features` to get the supported mode, and use 46 :ref:`lirc_set_rec_mode` set the current active mode. 47 48 The mode :ref:`LIRC_MODE_MODE2 <lirc-mode-mode2>` is for raw IR, 49 in which packets containing an unsigned int value describing an IR signal are 50 read from the chardev. 51 52 Alternatively, :ref:`LIRC_MODE_SCANCODE <lirc-mode-scancode>` can be available, 53 in this mode scancodes which are either decoded by software decoders, or 54 by hardware decoders. The :c:type:`rc_proto` member is set to the 55 :ref:`IR protocol <Remote_controllers_Protocols>` 56 used for transmission, and ``scancode`` to the decoded scancode, 57 and the ``keycode`` set to the keycode or ``KEY_RESERVED``. 58 59 Return Value 60 ============ 61 62 On success, the number of bytes read is returned. It is not an error if 63 this number is smaller than the number of bytes requested, or the amount 64 of data required for one frame. On error, -1 is returned, and the ``errno`` 65 variable is set appropriately.
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