NAME

makedev, major, minor — device number conversion

SYNOPSIS

#include < sys/types.h>

dev_t
makedev( int major, int minor);

int
major( dev_t dev);

int
minor( dev_t dev);

DESCRIPTION

The makedev() macro allows a unique device number to be generated based on its major and minor number. The major() and minor() macros can be used to obtain the original numbers from the device number dev.

In previous implementations of FreeBSD all block and character devices were uniquely identified by a pair of major and minor numbers. The major number referred to a certain device class (e.g. disks, TTYs) while the minor number identified an instance within the device class. Later versions of FreeBSD automatically generate a unique device number for each character device visible in /dev/. These numbers are not divided in device classes.

On FreeBSD these macros are only used by utilities that need to exchange numbers with other operating systems that may use different encodings for dev_t, but also applications that present these numbers to the user in a more conventional way.

RETURN VALUES

The major() macro returns a device major number that has a value between 0 and 255. The minor() macro returns a device minor number whose value can span the complete range of an int.

SEE ALSO

devfs(5), devname(3), mknod(2)