MAX_NUMBER_OF_DESCRIPTORS  494 drivers/net/ethernet/intel/e1000/e1000_hw.h #define MAX_NUMBER_OF_DESCRIPTORS  0xFFF8
MAX_NUMBER_OF_DESCRIPTORS   81 drivers/net/ethernet/intel/ixgb/ixgb_hw.h #define MAX_NUMBER_OF_DESCRIPTORS  0xFFF8	/* 13 bits in RDLEN/TDLEN, 128B aligned     */