B_UNITSHIFT
unit = (bootdev >> B_UNITSHIFT) & B_UNITMASK;
unit = (bootdev >> B_UNITSHIFT) & B_UNITMASK;
bootdev &= ~(B_UNITMASK << B_UNITSHIFT); /* XXX */
bootdev |= (unit << B_UNITSHIFT); /* XXX */
unit = (bootdev >> B_UNITSHIFT) & B_UNITMASK;
((controller) << B_CONTROLLERSHIFT) | ((unit) << B_UNITSHIFT) | \
#define B_UNIT(val) (((val) >> B_UNITSHIFT) & B_UNITMASK)