スキャンコードをキーコードにマップ

ノート: このページは既に特別なキーボードキーを読んでいることを前提としています。特別なキーボードキーでは広い範囲で問題を扱っています。

Mapping scancodes to keycodes is universal and not specific to Linux console or Xorg, which means that changes to this mapping will be effective in both.

スキャンコードをキーコードにマップする方法は2つあります:

• udev を使う
• setkeycodes を使う

The preferred method is to use udev because it uses hardware information (which is a quite reliable source) to choose the keyboard model in a database. It means that if your keyboard model has been found in the database, your keys are recognized out of the box.

スキャンコードの確認

リマップするキーのスキャンコードを知っておく必要があります。詳しくは特別なキーボードキー#スキャンコードを見て下さい。

udev を使う

udev provides a builtin function called hwdb to maintain the hardware database index in /etc/udev/hwdb.bin. The database is compiled from files with .hwdb extension located in directories /usr/lib/udev/hwdb.d/, /run/udev/hwdb.d/ and /etc/udev/hwdb.d/. The default scancodes-to-keycodes mapping file is /usr/lib/udev/hwdb.d/60-keyboard.hwdb. See man udev for details.

The .hwdb file can contain multiple blocks of mappings for different keyboards, or one block can be applied to multiple keyboards. The keyboard: prefix is used to match a block against a hardware, the following hardware matches are supported:

• USB keyboards identified by the usb kernel modalias:

  keyboard:usb:v<vendor_id>p<product_id>*

  where <vendor_id> and <product_id> are the 4-digit hex uppercase vendor and product IDs (you can find those by running the lsusb command).
• AT keyboard DMI data matches:

  keyboard:dmi:bvn*:bvr*:bd*:svn<vendor>:pn<product>:pvr*

  where <vendor> and <product> are the firmware-provided strings exported by the kernel DMI modalias.
• Platform driver device name and DMI data match:

  keyboard:name:<input_device_name>:dmi:bvn*:bvr*:bd*:svn<vendor>:pn*

  where <input_device_name> is the name device specified by the driver and <vendor> is the firmware-provided string exported by the kernel DMI modalias.

The format of each line in the block body is KEYBOARD_KEY_<scancode>=<keycode>. The value of <scancode> is hexadecimal, but without the leading 0x (i.e. specify a0 instead of 0xa0), whereas the value of <keycode> is the lower-case keycode name string as listed in /usr/include/linux/input.h (see the KEY_<KEYCODE> variables), a sorted list is available at [1]. It is not possible to specify decimal value in <keycode>.

hwdb のカスタム例

The example hwdb file will match all USB and AT keyboards:

/etc/udev/hwdb.d/90-custom-keyboard.hwdb

keyboard:usb:v*p*
keyboard:dmi:bvn*:bvr*:bd*:svn*:pn*:pvr*
 KEYBOARD_KEY_10=suspend
 KEYBOARD_KEY_a0=search

Hardware Database Index のアップデート

After changing the configuration files, the hardware database index, hwdb.bin, needs to be rebuilt.

• Update hwdb.bin manually by running

# udevadm hwdb --update

• Update automatically on each reboot by commenting out ConditionNeedsUpdate in systemd-udev-hwdb-update.service.

/usr/lib/systemd/system/systemd-udev-hwdb-update.service

#  This file is part of systemd.
.
.
#ConditionNeedsUpdate=/etc
.
.

After systemd-udev-hwdb-update.service finished loading systemd-udev-trigger.service will reload the changes from hwdb.bin.

• Automatically after Systemd upgrade.

On each upgrade of Systemd, the installation script rebuilds hwdb.bin by running # udevadm hwdb --update so we don't need to care about it.

Hardware Database Index のリロード

The kernel loads hwdb.bin as part of the boot process, rebooting the system will promise the loading of the updated hwdb.bin.

With udevadm it's possible to load new key mapping from the updated hwdb.bin by running

# udevadm trigger

Be aware that with udevadm only added or changed key mapping are loaded so if we delete a mapping from the config file, rebuild hwdb.bin and run # udevadm trigger then the deleted mapping still kept by the kernel, at least until a reboot.

setkeycodes を使う

setkeycodes is a tool to load scancodes-to-keycodes mapping table into Linux kernel. Its usage is:

# setkeycodes scancode keycode ...

It is possible to specify multiple pairs at once. Scancodes are given in hexadecimal, keycodes in decimal.