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Diffstat (limited to 'Documentation/userspace-api/media/rc/lirc-write.rst')
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diff --git a/Documentation/userspace-api/media/rc/lirc-write.rst b/Documentation/userspace-api/media/rc/lirc-write.rst new file mode 100644 index 000000000..c1c3230d4 --- /dev/null +++ b/Documentation/userspace-api/media/rc/lirc-write.rst @@ -0,0 +1,72 @@ +.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later +.. c:namespace:: RC + +.. _lirc-write: + +************ +LIRC write() +************ + +Name +==== + +lirc-write - Write to a LIRC device + +Synopsis +======== + +.. code-block:: c + + #include <unistd.h> + +.. c:function:: ssize_t write( int fd, void *buf, size_t count ) + +Arguments +========= + +``fd`` + File descriptor returned by ``open()``. + +``buf`` + Buffer with data to be written + +``count`` + Number of bytes at the buffer + +Description +=========== + +:c:func:`write()` writes up to ``count`` bytes to the device +referenced by the file descriptor ``fd`` from the buffer starting at +``buf``. + +The exact format of the data depends on what mode a driver is in, use +:ref:`lirc_get_features` to get the supported modes and use +:ref:`lirc_set_send_mode` set the mode. + +When in :ref:`LIRC_MODE_PULSE <lirc-mode-PULSE>` mode, the data written to +the chardev is a pulse/space sequence of integer values. Pulses and spaces +are only marked implicitly by their position. The data must start and end +with a pulse, therefore, the data must always include an uneven number of +samples. The write function blocks until the data has been transmitted +by the hardware. If more data is provided than the hardware can send, the +driver returns ``EINVAL``. + +When in :ref:`LIRC_MODE_SCANCODE <lirc-mode-scancode>` mode, one +``struct lirc_scancode`` must be written to the chardev at a time, else +``EINVAL`` is returned. Set the desired scancode in the ``scancode`` member, +and the :ref:`IR protocol <Remote_controllers_Protocols>` in the +:c:type:`rc_proto`: member. All other members must be +set to 0, else ``EINVAL`` is returned. If there is no protocol encoder +for the protocol or the scancode is not valid for the specified protocol, +``EINVAL`` is returned. The write function blocks until the scancode +is transmitted by the hardware. + +Return Value +============ + +On success, the number of bytes written is returned. It is not an error if +this number is smaller than the number of bytes requested, or the amount +of data required for one frame. On error, -1 is returned, and the ``errno`` +variable is set appropriately. The generic error codes are described at the +:ref:`Generic Error Codes <gen-errors>` chapter. |