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-write: 4 .. _lirc-write:
5 5
6 ************ 6 ************
7 LIRC write() 7 LIRC write()
8 ************ 8 ************
9 9
10 Name 10 Name
11 ==== 11 ====
12 12
13 lirc-write - Write to a LIRC device 13 lirc-write - Write to 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 write( int fd, void *b 22 .. c:function:: ssize_t write( 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 with data to be written 31 Buffer with data to be written
32 32
33 ``count`` 33 ``count``
34 Number of bytes at the buffer 34 Number of bytes at the buffer
35 35
36 Description 36 Description
37 =========== 37 ===========
38 38
39 :c:func:`write()` writes up to ``count`` bytes 39 :c:func:`write()` writes up to ``count`` bytes to the device
40 referenced by the file descriptor ``fd`` from 40 referenced by the file descriptor ``fd`` from the buffer starting at
41 ``buf``. 41 ``buf``.
42 42
43 The exact format of the data depends on what m 43 The exact format of the data depends on what mode a driver is in, use
44 :ref:`lirc_get_features` to get the supported 44 :ref:`lirc_get_features` to get the supported modes and use
45 :ref:`lirc_set_send_mode` set the mode. 45 :ref:`lirc_set_send_mode` set the mode.
46 46
47 When in :ref:`LIRC_MODE_PULSE <lirc-mode-PULSE 47 When in :ref:`LIRC_MODE_PULSE <lirc-mode-PULSE>` mode, the data written to
48 the chardev is a pulse/space sequence of integ 48 the chardev is a pulse/space sequence of integer values. Pulses and spaces
49 are only marked implicitly by their position. 49 are only marked implicitly by their position. The data must start and end
50 with a pulse, therefore, the data must always 50 with a pulse, therefore, the data must always include an uneven number of
51 samples. The write function blocks until the d 51 samples. The write function blocks until the data has been transmitted
52 by the hardware. If more data is provided than 52 by the hardware. If more data is provided than the hardware can send, the
53 driver returns ``EINVAL``. 53 driver returns ``EINVAL``.
54 54
55 When in :ref:`LIRC_MODE_SCANCODE <lirc-mode-sc 55 When in :ref:`LIRC_MODE_SCANCODE <lirc-mode-scancode>` mode, one
56 ``struct lirc_scancode`` must be written to th 56 ``struct lirc_scancode`` must be written to the chardev at a time, else
57 ``EINVAL`` is returned. Set the desired scanco 57 ``EINVAL`` is returned. Set the desired scancode in the ``scancode`` member,
58 and the :ref:`IR protocol <Remote_controllers_ 58 and the :ref:`IR protocol <Remote_controllers_Protocols>` in the
59 :c:type:`rc_proto`: member. All other members 59 :c:type:`rc_proto`: member. All other members must be
60 set to 0, else ``EINVAL`` is returned. If ther 60 set to 0, else ``EINVAL`` is returned. If there is no protocol encoder
61 for the protocol or the scancode is not valid 61 for the protocol or the scancode is not valid for the specified protocol,
62 ``EINVAL`` is returned. The write function blo 62 ``EINVAL`` is returned. The write function blocks until the scancode
63 is transmitted by the hardware. 63 is transmitted by the hardware.
64 64
65 Return Value 65 Return Value
66 ============ 66 ============
67 67
68 On success, the number of bytes written is ret 68 On success, the number of bytes written is returned. It is not an error if
69 this number is smaller than the number of byte 69 this number is smaller than the number of bytes requested, or the amount
70 of data required for one frame. On error, -1 70 of data required for one frame. On error, -1 is returned, and the ``errno``
71 variable is set appropriately. The generic err 71 variable is set appropriately. The generic error codes are described at the
72 :ref:`Generic Error Codes <gen-errors>` chapte 72 :ref:`Generic Error Codes <gen-errors>` chapter.
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