HelenOS sources

USB_HIDUT_PAGE_KEYBOARD   48 uspace/app/vuhid/hids/bootkbd.c 	STD_USAGE_PAGE(USB_HIDUT_PAGE_KEYBOARD),
USB_HIDUT_PAGE_KEYBOARD   76 uspace/app/vuhid/hids/bootkbd.c 	STD_USAGE_PAGE(USB_HIDUT_PAGE_KEYBOARD),
USB_HIDUT_PAGE_KEYBOARD  436 uspace/drv/hid/usbhid/kbd/kbddev.c 	    usb_hid_report_path_append_item(path, USB_HIDUT_PAGE_KEYBOARD, 0);
USB_HIDUT_PAGE_KEYBOARD  507 uspace/drv/hid/usbhid/kbd/kbddev.c 	    usb_hid_report_path_append_item(path, USB_HIDUT_PAGE_KEYBOARD, 0);
HelenOS homepage, sources at GitHub