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 September 28, 2008 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 allows a unique device number to be generated based on its 47.Fa major 48and 49.Fa minor 50number. 51The 52.Fn major 53and 54.Fn minor 55macros can be used to obtain the original numbers from the device number 56.Fa dev . 57.Pp 58In previous implementations of 59.Fx 60all block and character devices were uniquely identified by a pair of 61major and minor numbers. 62The major number referred to a certain device class (e.g. disks, TTYs) 63while the minor number identified an instance within the device class. 64Later versions of 65.Fx 66automatically generate a unique device number for each character device 67visible in 68.Pa /dev/ . 69These numbers are not divided in device classes. 70.Pp 71On 72.Fx 73these macros are only used by utilities that need to exchange numbers 74with other operating systems that may use different encodings for 75.Vt dev_t , 76but also applications that present these numbers to the user in a more 77conventional way. 78.Sh RETURN VALUES 79The 80.Fn major 81macro returns a device major number that has a value between 0 and 255. 82The 83.Fn minor 84macro returns a device minor number whose value can span the complete 85range of an 86.Vt int . 87.Sh SEE ALSO 88.Xr mknod 2 , 89.Xr devname 3 , 90.Xr devfs 5 91