1 .. SPDX-License-Identifier: GPL-2.0 OR GFDL-1. 1 .. SPDX-License-Identifier: GPL-2.0 OR GFDL-1.1-no-invariants-or-later
2 .. c:namespace:: RC 2 .. c:namespace:: RC
3 3
4 .. _lirc-read: 4 .. _lirc-read:
5 5
6 *********** 6 ***********
7 LIRC read() 7 LIRC read()
8 *********** 8 ***********
9 9
10 Name 10 Name
11 ==== 11 ====
12 12
13 lirc-read - Read from a LIRC device 13 lirc-read - Read from a LIRC device
14 14
15 Synopsis 15 Synopsis
16 ======== 16 ========
17 17
18 .. code-block:: c 18 .. code-block:: c
19 19
20 #include <unistd.h> 20 #include <unistd.h>
21 21
22 .. c:function:: ssize_t read( int fd, void *bu 22 .. c:function:: ssize_t read( int fd, void *buf, size_t count )
23 23
24 Arguments 24 Arguments
25 ========= 25 =========
26 26
27 ``fd`` 27 ``fd``
28 File descriptor returned by ``open()``. 28 File descriptor returned by ``open()``.
29 29
30 ``buf`` 30 ``buf``
31 Buffer to be filled 31 Buffer to be filled
32 32
33 ``count`` 33 ``count``
34 Max number of bytes to read 34 Max number of bytes to read
35 35
36 Description 36 Description
37 =========== 37 ===========
38 38
39 :c:func:`read()` attempts to read up to ``coun 39 :c:func:`read()` attempts to read up to ``count`` bytes from file
40 descriptor ``fd`` into the buffer starting at 40 descriptor ``fd`` into the buffer starting at ``buf``. If ``count`` is zero,
41 :c:func:`read()` returns zero and has no other 41 :c:func:`read()` returns zero and has no other results. If ``count``
42 is greater than ``SSIZE_MAX``, the result is u 42 is greater than ``SSIZE_MAX``, the result is unspecified.
43 43
44 The exact format of the data depends on what : 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 45 uses. Use :ref:`lirc_get_features` to get the supported mode, and use
46 :ref:`lirc_set_rec_mode` set the current activ 46 :ref:`lirc_set_rec_mode` set the current active mode.
47 47
48 The mode :ref:`LIRC_MODE_MODE2 <lirc-mode-mode 48 The mode :ref:`LIRC_MODE_MODE2 <lirc-mode-mode2>` is for raw IR,
49 in which packets containing an unsigned int va 49 in which packets containing an unsigned int value describing an IR signal are
50 read from the chardev. 50 read from the chardev.
51 51
52 Alternatively, :ref:`LIRC_MODE_SCANCODE <lirc- 52 Alternatively, :ref:`LIRC_MODE_SCANCODE <lirc-mode-scancode>` can be available,
53 in this mode scancodes which are either decode 53 in this mode scancodes which are either decoded by software decoders, or
54 by hardware decoders. The :c:type:`rc_proto` m 54 by hardware decoders. The :c:type:`rc_proto` member is set to the
55 :ref:`IR protocol <Remote_controllers_Protocol 55 :ref:`IR protocol <Remote_controllers_Protocols>`
56 used for transmission, and ``scancode`` to the 56 used for transmission, and ``scancode`` to the decoded scancode,
57 and the ``keycode`` set to the keycode or ``KE 57 and the ``keycode`` set to the keycode or ``KEY_RESERVED``.
58 58
59 Return Value 59 Return Value
60 ============ 60 ============
61 61
62 On success, the number of bytes read is return 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 byte 63 this number is smaller than the number of bytes requested, or the amount
64 of data required for one frame. On error, -1 64 of data required for one frame. On error, -1 is returned, and the ``errno``
65 variable is set appropriately. 65 variable is set appropriately.
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