HelenOS sources
KC_N0 125 uspace/drv/hid/adb-kbd/ctl.c [0x52] = KC_N0,
KC_N0 159 uspace/drv/hid/atkbd/atkbd.c [0x70] = KC_N0,
KC_N0 148 uspace/drv/hid/usbhid/kbd/conv.c [0x62] = KC_N0,
KC_N0 152 uspace/drv/hid/xtkbd/xtkbd.c [0x52] = KC_N0,
KC_N0 192 uspace/srv/hid/input/ctl/sun.c [0x5e] = KC_N0,
KC_N0 194 uspace/srv/hid/input/layout/ar.c [KC_N0] = '0',
KC_N0 223 uspace/srv/hid/input/layout/cz.c [KC_N0] = '0',
KC_N0 202 uspace/srv/hid/input/layout/fr_azerty.c [KC_N0] = '0',
KC_N0 203 uspace/srv/hid/input/layout/us_dvorak.c [KC_N0] = '0',
KC_N0 197 uspace/srv/hid/input/layout/us_qwerty.c [KC_N0] = '0',
HelenOS homepage, sources at GitHub