B_TYPEMASK
name = devsw_blk2name((bootdev >> B_TYPESHIFT) & B_TYPEMASK);
name = devsw_blk2name((bootdev >> B_TYPESHIFT) & B_TYPEMASK);
name = devsw_blk2name((bootdev >> B_TYPESHIFT) & B_TYPEMASK);
#define B_TYPE(val) (((val) >> B_TYPESHIFT) & B_TYPEMASK)