DASD_PARTN_BITS
gdp->first_minor = devindex << DASD_PARTN_BITS;
gdp->minors = 1 << DASD_PARTN_BITS;
#define DASD_PER_MAJOR (1U << (MINORBITS - DASD_PARTN_BITS))
#define DASD_PARTN_MASK ((1 << DASD_PARTN_BITS) - 1)