73 lines
2.2 KiB
ReStructuredText
73 lines
2.2 KiB
ReStructuredText
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.. SPDX-License-Identifier: GPL-2.0 OR GFDL-1.1-no-invariants-or-later
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.. c:namespace:: RC
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.. _lirc-write:
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************
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LIRC write()
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************
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Name
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====
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lirc-write - Write to a LIRC device
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Synopsis
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========
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.. code-block:: c
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#include <unistd.h>
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.. c:function:: ssize_t write( int fd, void *buf, size_t count )
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Arguments
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=========
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``fd``
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File descriptor returned by ``open()``.
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``buf``
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Buffer with data to be written
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``count``
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Number of bytes at the buffer
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Description
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===========
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:c:func:`write()` writes up to ``count`` bytes to the device
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referenced by the file descriptor ``fd`` from the buffer starting at
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``buf``.
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The exact format of the data depends on what mode a driver is in, use
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:ref:`lirc_get_features` to get the supported modes and use
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:ref:`lirc_set_send_mode` set the mode.
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When in :ref:`LIRC_MODE_PULSE <lirc-mode-PULSE>` mode, the data written to
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the chardev is a pulse/space sequence of integer values. Pulses and spaces
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are only marked implicitly by their position. The data must start and end
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with a pulse, therefore, the data must always include an uneven number of
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samples. The write function blocks until the data has been transmitted
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by the hardware. If more data is provided than the hardware can send, the
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driver returns ``EINVAL``.
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When in :ref:`LIRC_MODE_SCANCODE <lirc-mode-scancode>` mode, one
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``struct lirc_scancode`` must be written to the chardev at a time, else
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``EINVAL`` is returned. Set the desired scancode in the ``scancode`` member,
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and the :ref:`IR protocol <Remote_controllers_Protocols>` in the
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:c:type:`rc_proto`: member. All other members must be
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set to 0, else ``EINVAL`` is returned. If there is no protocol encoder
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for the protocol or the scancode is not valid for the specified protocol,
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``EINVAL`` is returned. The write function blocks until the scancode
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is transmitted by the hardware.
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Return Value
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============
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On success, the number of bytes written is returned. It is not an error if
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this number is smaller than the number of bytes requested, or the amount
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of data required for one frame. On error, -1 is returned, and the ``errno``
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variable is set appropriately. The generic error codes are described at the
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:ref:`Generic Error Codes <gen-errors>` chapter.
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