Entry Point size()

Entry Point size()

The pfxsize() entry point is required of block device drivers. It reports the size of the device in "sector" units, where a "sector" size is declared as NBPSCTR in sys/param.h (currently 512). The prototype is

int pfxsize(dev_t dev);

The device major and minor numbers can be extracted from the dev argument. The entry point is not called until pfxopen() has been called. Typically the driver will calculate the size of the medium during pfxopen().

Since the int return value is 32 bits in all systems, the largest possible block device is 1,024 gigabytes ((231*512)/1,0243).