MAKEDEV(3) Linux Programmer's Manual MAKEDEV(3)
makedev, major, minor - manage a device number
#define _BSD_SOURCE /* See feature_test_macros(7) */
dev_t makedev(int maj, int min);
unsigned int major(dev_t dev);
unsigned int minor(dev_t dev);
A device ID consists of two parts: a major ID, identifying the class of the device, and a
minor ID, identifying a specific instance of a device in that class. A device ID is rep-
resented using the type dev_t.
Given major and minor device IDs, makedev() combines these to produce a device ID,
returned as the function result. This device ID can be given to mknod(2), for example.
The major() and minor() functions perform the converse task: given a device ID, they
return, respectively, the major and minor components. These macros can be useful to, for
example, decompose the device IDs in the structure returned by stat(2).
The makedev(), major(), and minor() functions are not specified in POSIX.1, but are
present on many other systems.
These interfaces are defined as macros. Since glibc 2.3.3, they have been aliases for
three GNU-specific functions: gnu_dev_makedev(), gnu_dev_major(), and gnu_dev_minor().
The latter names are exported, but the traditional names are more portable.
This page is part of release 3.55 of the Linux man-pages project. A description of the
project, and information about reporting bugs, can be found at
Linux 2012-05-10 MAKEDEV(3)