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