HelenOS sources

XHCI_EC_SP_MAJOR  332 uspace/drv/bus/usb/xhci/debug.c 		    XHCI_REG_RD(ec, XHCI_EC_SP_MAJOR),
XHCI_EC_SP_MAJOR   98 uspace/drv/bus/usb/xhci/hc.c 			major = XHCI_REG_RD(ec, XHCI_EC_SP_MAJOR);
HelenOS homepage, sources at GitHub