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