| .. SPDX-License-Identifier: GPL-2.0 |
| |
| ====================================================== |
| Infrared remote control support in video4linux drivers |
| ====================================================== |
| |
| Authors: Gerd Hoffmann, Mauro Carvalho Chehab |
| |
| Basics |
| ====== |
| |
| 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"). |
| |
| 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. |
| |
| 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-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 |
| ============ |
| |
| The modules register the remote as keyboard within the linux input |
| layer, i.e. you'll see the keys of the remote as normal key strokes |
| (if CONFIG_INPUT_KEYBOARD is enabled). |
| |
| Using the event devices (CONFIG_INPUT_EVDEV) it is possible for |
| applications to access the remote via /dev/input/event<n> devices. |
| 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 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 any other input utility that changes |
| the keymaps, like the input kbd utility. |
| |
| |
| Using with lircd |
| ---------------- |
| |
| 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 |
| ------------------- |
| |
| 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 reassign |
| 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. |
