1.\" Copyright (c) 2008 Ed Schouten <ed@FreeBSD.org> 2.\" All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 13.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 14.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 15.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 16.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 17.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 18.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 19.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 20.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 21.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 22.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 23.\" SUCH DAMAGE. 24.\" 25.\" $FreeBSD$ 26.\" 27.Dd August 3, 2017 28.Dt MAKEDEV 3 29.Os 30.Sh NAME 31.Nm makedev , 32.Nm major , 33.Nm minor 34.Nd device number conversion 35.Sh SYNOPSIS 36.In sys/types.h 37.Ft dev_t 38.Fn makedev "int major" "int minor" 39.Ft int 40.Fn major "dev_t dev" 41.Ft int 42.Fn minor "dev_t dev" 43.Sh DESCRIPTION 44The 45.Fn makedev 46macro returns a device number created from the provided 47.Fa major 48and 49.Fa minor 50number. 51The 52.Fn major 53and 54.Fn minor 55macros return the original numbers from the device number 56.Fa dev . 57In other words, for a value 58.Va dev 59of the type 60.Vt dev_t , 61and values 62.Va ma , mi 63of the type 64.Vt int , 65the assertions 66.Dl dev == makedev(major(dev), minor(dev)) 67.Dl ma == major(makedev(ma, mi)) 68.Dl mi == minor(makedev(ma, mi)) 69are valid. 70.Pp 71In previous implementations of 72.Fx 73all block and character devices were uniquely identified by a pair of 74stable major and minor numbers. 75The major number referred to a certain device class (e.g. disks, TTYs) 76while the minor number identified an instance within the device class. 77Later versions of 78.Fx 79automatically generate a unique device number for each character device 80visible in 81.Pa /dev/ . 82These numbers are not divided in device classes and are not guaranteed 83to be stable upon reboot or driver reload. 84.Pp 85On 86.Fx 87these macros are only used by utilities that need to exchange numbers 88with other operating systems that may use different encodings for 89.Vt dev_t , 90but also applications that present these numbers to the user in a more 91conventional way. 92.Sh RETURN VALUES 93The 94.Fn major 95and 96.Fn minor 97macros return numbers whose value can span the complete range of an 98.Vt int . 99.Sh SEE ALSO 100.Xr mknod 2 , 101.Xr devname 3 , 102.Xr devfs 5 103