1 .. SPDX-License-Identifier: GPL-2.0 OR GFDL-1.1-no-invariants-or-later 2 .. c:namespace:: RC 3 4 .. _lirc-write: 5 6 ************ 7 LIRC write() 8 ************ 9 10 Name 11 ==== 12 13 lirc-write - Write to a LIRC device 14 15 Synopsis 16 ======== 17 18 .. code-block:: c 19 20 #include <unistd.h> 21 22 .. c:function:: ssize_t write( 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 with data to be written 32 33 ``count`` 34 Number of bytes at the buffer 35 36 Description 37 =========== 38 39 :c:func:`write()` writes up to ``count`` bytes to the device 40 referenced by the file descriptor ``fd`` from the buffer starting at 41 ``buf``. 42 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 modes and use 45 :ref:`lirc_set_send_mode` set the mode. 46 47 When in :ref:`LIRC_MODE_PULSE <lirc-mode-PULSE>` mode, the data written to 48 the chardev is a pulse/space sequence of integer values. Pulses and spaces 49 are only marked implicitly by their position. The data must start and end 50 with a pulse, therefore, the data must always include an uneven number of 51 samples. The write function blocks until the data has been transmitted 52 by the hardware. If more data is provided than the hardware can send, the 53 driver returns ``EINVAL``. 54 55 When in :ref:`LIRC_MODE_SCANCODE <lirc-mode-scancode>` mode, one 56 ``struct lirc_scancode`` must be written to the chardev at a time, else 57 ``EINVAL`` is returned. Set the desired scancode in the ``scancode`` member, 58 and the :ref:`IR protocol <Remote_controllers_Protocols>` in the 59 :c:type:`rc_proto`: member. All other members must be 60 set to 0, else ``EINVAL`` is returned. If there is no protocol encoder 61 for the protocol or the scancode is not valid for the specified protocol, 62 ``EINVAL`` is returned. The write function blocks until the scancode 63 is transmitted by the hardware. 64 65 Return Value 66 ============ 67 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 bytes requested, or the amount 70 of data required for one frame. On error, -1 is returned, and the ``errno`` 71 variable is set appropriately. The generic error codes are described at the 72 :ref:`Generic Error Codes <gen-errors>` chapter.
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