1 .\" Copyright (c) 2008 Ed Schouten <ed@FreeBSD.org>
2 .\" All rights reserved.
4 .\" Redistribution and use in source and binary forms, with or without
5 .\" modification, are permitted provided that the following conditions
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.
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
34 .Nd device number conversion
38 .Fn makedev "int major" "int minor"
46 macro returns a device number created from the provided
55 macros return the original numbers from the device number
57 In other words, for a value
66 .Dl dev == makedev(major(dev), minor(dev))
67 .Dl ma == major(makedev(ma, mi))
68 .Dl mi == minor(makedev(ma, mi))
71 In previous implementations of
73 all block and character devices were uniquely identified by a pair of
74 stable major and minor numbers.
75 The major number referred to a certain device class (e.g. disks, TTYs)
76 while the minor number identified an instance within the device class.
79 automatically generate a unique device number for each character device
82 These numbers are not divided in device classes and are not guaranteed
83 to be stable upon reboot or driver reload.
87 these macros are only used by utilities that need to exchange numbers
88 with other operating systems that may use different encodings for
90 but also applications that present these numbers to the user in a more
97 macros return numbers whose value can span the complete range of an