lirc-write.rst (2252B)
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************ 7LIRC write() 8************ 9 10Name 11==== 12 13lirc-write - Write to a LIRC device 14 15Synopsis 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 24Arguments 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 36Description 37=========== 38 39:c:func:`write()` writes up to ``count`` bytes to the device 40referenced by the file descriptor ``fd`` from the buffer starting at 41``buf``. 42 43The 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 47When in :ref:`LIRC_MODE_PULSE <lirc-mode-PULSE>` mode, the data written to 48the chardev is a pulse/space sequence of integer values. Pulses and spaces 49are only marked implicitly by their position. The data must start and end 50with a pulse, therefore, the data must always include an uneven number of 51samples. The write function blocks until the data has been transmitted 52by the hardware. If more data is provided than the hardware can send, the 53driver returns ``EINVAL``. 54 55When 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, 58and the :ref:`IR protocol <Remote_controllers_Protocols>` in the 59:c:type:`rc_proto`: member. All other members must be 60set to 0, else ``EINVAL`` is returned. If there is no protocol encoder 61for the protocol or the scancode is not valid for the specified protocol, 62``EINVAL`` is returned. The write function blocks until the scancode 63is transmitted by the hardware. 64 65Return Value 66============ 67 68On success, the number of bytes written is returned. It is not an error if 69this number is smaller than the number of bytes requested, or the amount 70of data required for one frame. On error, -1 is returned, and the ``errno`` 71variable is set appropriately. The generic error codes are described at the 72:ref:`Generic Error Codes <gen-errors>` chapter.