1.. SPDX-License-Identifier: GPL-2.0 2 3====================================================== 4Infrared remote control support in video4linux drivers 5====================================================== 6 7Authors: Gerd Hoffmann, Mauro Carvalho Chehab 8 9Basics 10====== 11 12Most analog and digital TV boards support remote controllers. Several of 13them have a microprocessor that receives the IR carriers, convert into 14pulse/space sequences and then to scan codes, returning such codes to 15userspace ("scancode mode"). Other boards return just the pulse/space 16sequences ("raw mode"). 17 18The support for remote controller in scancode mode is provided by the 19standard Linux input layer. The support for raw mode is provided via LIRC. 20 21In order to check the support and test it, it is suggested to download 22the `v4l-utils <https://git.linuxtv.org/v4l-utils.git/>`_. It provides 23two tools to handle remote controllers: 24 25- ir-keytable: provides a way to query the remote controller, list the 26 protocols it supports, enable in-kernel support for IR decoder or 27 switch the protocol and to test the reception of scan codes; 28 29- ir-ctl: provide tools to handle remote controllers that support raw mode 30 via LIRC interface. 31 32Usually, the remote controller module is auto-loaded when the TV card is 33detected. However, for a few devices, you need to manually load the 34ir-kbd-i2c module. 35 36How it works 37============ 38 39The modules register the remote as keyboard within the linux input 40layer, i.e. you'll see the keys of the remote as normal key strokes 41(if CONFIG_INPUT_KEYBOARD is enabled). 42 43Using the event devices (CONFIG_INPUT_EVDEV) it is possible for 44applications to access the remote via /dev/input/event<n> devices. 45The udev/systemd will automatically create the devices. If you install 46the `v4l-utils <https://git.linuxtv.org/v4l-utils.git/>`_, it may also 47automatically load a different keytable than the default one. Please see 48`v4l-utils <https://git.linuxtv.org/v4l-utils.git/>`_ ir-keytable.1 49man page for details. 50 51The ir-keytable tool is nice for trouble shooting, i.e. to check 52whenever the input device is really present, which of the devices it 53is, check whenever pressing keys on the remote actually generates 54events and the like. You can also use any other input utility that changes 55the keymaps, like the input kbd utility. 56 57 58Using with lircd 59---------------- 60 61The latest versions of the lircd daemon supports reading events from the 62linux input layer (via event device). It also supports receiving IR codes 63in lirc mode. 64 65 66Using without lircd 67------------------- 68 69Xorg recognizes several IR keycodes that have its numerical value lower 70than 247. With the advent of Wayland, the input driver got updated too, 71and should now accept all keycodes. Yet, you may want to just reassign 72the keycodes to something that your favorite media application likes. 73 74This can be done by setting 75`v4l-utils <https://git.linuxtv.org/v4l-utils.git/>`_ to load your own 76keytable in runtime. Please read ir-keytable.1 man page for details. 77