Documentation/media/uapi/rc/lirc-dev-intro.rst

.. -*- 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 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.

    This mode is used only for IR receive.

.. _lirc-mode-lirccode:

``LIRC_MODE_LIRCCODE``

    The IR signal is decoded internally by the receiver. The LIRC interface
    returns the scancode as an integer value. This is the usual mode used
    by several TV media cards.

    This mode is used only for IR receive.

.. _lirc-mode-pulse:

``LIRC_MODE_PULSE``

    On puse mode, a sequence of pulse/space integer values are written to the
    lirc device using :Ref:`lirc-write`.

    This mode is used only for IR send.