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.. -*- coding: utf-8; mode: rst -*-
.. _lirc_dev_intro:
************
Introduction
************
The LIRC device interface is a bi-directional interface for transporting
raw IR data between userspace and kernelspace. Fundamentally, it is just
a chardev (/dev/lircX, for X = 0, 1, 2, ...), with a number of standard
struct file_operations defined on it. With respect to transporting raw
IR data to and fro, the essential fops are read, write and ioctl.
Example dmesg output upon a driver registering w/LIRC:
.. code-block:: none
$ dmesg |grep lirc_dev
lirc_dev: IR Remote Control driver registered, major 248
rc rc0: lirc_dev: driver ir-lirc-codec (mceusb) registered at minor = 0
What you should see for a chardev:
.. code-block:: none
$ ls -l /dev/lirc*
crw-rw---- 1 root root 248, 0 Jul 2 22:20 /dev/lirc0
.. _lirc_modes:
**********
LIRC modes
**********
LIRC supports some modes of receiving and sending IR codes, as shown
on the following table.
.. _lirc-mode-mode2:
``LIRC_MODE_MODE2``
The driver returns a sequence of pulse and space codes to userspace,
as a series of u32 values.
This mode is used only for IR receive.
The upper 8 bits determine the packet type, and the lower 24 bits
the payload. Use ``LIRC_VALUE()`` macro to get the payload, and
the macro ``LIRC_MODE2()`` will give you the type, which
is one of:
``LIRC_MODE2_PULSE``
Signifies the presence of IR in microseconds.
``LIRC_MODE2_SPACE``
Signifies absence of IR in microseconds.
``LIRC_MODE2_FREQUENCY``
If measurement of the carrier frequency was enabled with
:ref:`lirc_set_measure_carrier_mode` then this packet gives you
the carrier frequency in Hertz.
``LIRC_MODE2_TIMEOUT``
If timeout reports are enabled with
:ref:`lirc_set_rec_timeout_reports`, when the timeout set with
:ref:`lirc_set_rec_timeout` expires due to no IR being detected,
this packet will be sent, with the number of microseconds with
no IR.
.. _lirc-mode-pulse:
``LIRC_MODE_PULSE``
In pulse mode, a sequence of pulse/space integer values are written to the
lirc device using :ref:`lirc-write`.
The values are alternating pulse and space lengths, in microseconds. The
first and last entry must be a pulse, so there must be an odd number
of entries.
This mode is used only for IR send.
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