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$FreeBSD: releng/9.3/share/man/man3/makedev.3 183443 2008-09-28 20:26:16Z ed $
.Dd September 28, 2008 .Dt MAKEDEV 3 .Os .Sh NAME .Nm makedev , .Nm major , .Nm minor .Nd device number conversion .Sh SYNOPSIS n sys/types.h .Ft dev_t .Fn makedev "int major" "int minor" .Ft int .Fn major "dev_t dev" .Ft int .Fn minor "dev_t dev" .Sh DESCRIPTION The .Fn makedev macro allows a unique device number to be generated based on its .Fa major and .Fa minor number. The .Fn major and .Fn minor macros can be used to obtain the original numbers from the device number .Fa dev .
p In previous implementations of .Fx 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 .Fx automatically generate a unique device number for each character device visible in
a /dev/ . These numbers are not divided in device classes.
p On .Fx these macros are only used by utilities that need to exchange numbers with other operating systems that may use different encodings for .Vt dev_t , but also applications that present these numbers to the user in a more conventional way. .Sh RETURN VALUES The .Fn major macro returns a device major number that has a value between 0 and 255. The .Fn minor macro returns a device minor number whose value can span the complete range of an .Vt int . .Sh SEE ALSO .Xr devfs 5 , .Xr devname 3 , .Xr mknod 2