[media] v4l-with-ir.rst: update it to reflect the current status

infrared remote control support in video4linux drivers

Infrared remote control support in video4linux drivers

======================================================

Author: Gerd Hoffmann

.. note::

   This section is outdated.

Authors: Gerd Hoffmann, Mauro Carvalho Chehab

Basics

------

Current versions use the linux input layer to support infrared

remote controls.  I suggest to download my input layer tools

from http://bytesex.org/snapshot/input-<date>.tar.gz

Most analog and digital TV boards support remote controllers. Several of

them have a microprocessor that receives the IR carriers, convert into

pulse/space sequences and then to scan codes, returning such codes to

userspace ("scancode mode"). Other boards return just the pulse/space

sequences ("raw mode").

Modules you have to load:

The support for remote controller in scancode mode is provided by the

standard Linux input layer. The support for raw mode is provided via LIRC.

  saa7134	statically built in, i.e. just the driver :)

  bttv		ir-kbd-gpio or ir-kbd-i2c depending on your

		card.

In order to check the support and test it, it is suggested to download

the `v4l-utils <https://git.linuxtv.org/v4l-utils.git/>`_. It provides

two tools to handle remote controllers:

ir-kbd-gpio and ir-kbd-i2c don't support all cards lirc supports

(yet), mainly for the reason that the code of lirc_i2c and lirc_gpio

was very confusing and I decided to basically start over from scratch.

Feel free to contact me in case of trouble.  Note that the ir-kbd-*

modules work on 2.6.x kernels only through ...

- ir-keytable: provides a way to query the remote controller, list the

  protocols it supports, enable in-kernel support for IR decoder or

  switch the protocol and to test the reception of scan codes;

- ir-ctl: provide tools to handle remote controllers that support raw mode

  via LIRC interface.

Usually, the remote controller module is auto-loaded when the TV card is

detected. However, for a few devices, you need to manually load the

ir-kbd-i2c module.

How it works

------------

Using the event devices (CONFIG_INPUT_EVDEV) it is possible for

applications to access the remote via /dev/input/event<n> devices.

You might have to create the special files using "/sbin/MAKEDEV

input".  The input layer tools mentioned above use the event device.

The udev/systemd will automatically create the devices. If you install

the `v4l-utils <https://git.linuxtv.org/v4l-utils.git/>`_, it may also

automatically load a different keytable than the default one. Please see

`v4l-utils <https://git.linuxtv.org/v4l-utils.git/>`_ ir-keytable.1

man page for details.

The input layer tools are nice for trouble shooting, i.e. to check

The ir-keytable tool is nice for trouble shooting, i.e. to check

whenever the input device is really present, which of the devices it

is, check whenever pressing keys on the remote actually generates

events and the like.  You can also use the kbd utility to change the

keymaps (2.6.x kernels only through).

events and the like.  You can also use any other input utility that changes

the keymaps, like the input kbd utility.

Using with lircd

================

The cvs version of the lircd daemon supports reading events from the

linux input layer (via event device).  The input layer tools tarball

comes with a lircd config file.

The latest versions of the lircd daemon supports reading events from the

linux input layer (via event device). It also supports receiving IR codes

in lirc mode.

Using without lircd

===================

XFree86 likely can be configured to recognise the remote keys.  Once I

simply tried to configure one of the multimedia keyboards as input

device, which had the effect that XFree86 recognised some of the keys

of my remote control and passed volume up/down key presses as

XF86AudioRaiseVolume and XF86AudioLowerVolume key events to the X11

clients.

It likely is possible to make that fly with a nice xkb config file,

I know next to nothing about that through.

Have fun,

  Gerd

Xorg recognizes several IR keycodes that have its numerical value lower

than 247. With the advent of Wayland, the input driver got updated too,

and should now accept all keycodes. Yet, you may want to just reasign

the keycodes to something that your favorite media application likes.

--

This can be done by setting

`v4l-utils <https://git.linuxtv.org/v4l-utils.git/>`_ to load your own

keytable in runtime. Please read  ir-keytable.1 man page for details.