1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
|
.\" Copyright (c) 2005 Gleb Smirnoff <glebius@FreeBSD.org>
.\" All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\" notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\" notice, this list of conditions and the following disclaimer in the
.\" documentation and/or other materials provided with the distribution.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\" $FreeBSD$
.\"
.Dd July 5, 2010
.Dt ALLOC_UNR 9
.Os
.Sh NAME
.Nm new_unrhdr ,
.Nm delete_unrhdr ,
.Nm alloc_unr ,
.Nm alloc_unr_specific ,
.Nm free_unr
.Nd "kernel unit number allocator"
.Sh SYNOPSIS
.In sys/systm.h
.Ft "struct unrhdr *"
.Fn new_unrhdr "int low" "int high" "struct mtx *mutex"
.Ft void
.Fn delete_unrhdr "struct unrhdr *uh"
.Ft int
.Fn alloc_unr "struct unrhdr *uh"
.Ft int
.Fn alloc_unrl "struct unrhdr *uh"
.Ft int
.Fn alloc_unr_specific "struct unrhdr *uh" "u_int item"
.Ft void
.Fn free_unr "struct unrhdr *uh" "u_int item"
.Sh DESCRIPTION
The kernel unit number allocator is a generic facility, which allows to allocate
unit numbers within a specified range.
.Bl -tag -width indent
.It Fn new_unrhdr low high mutex
Initialize a new unit number allocator entity.
The
.Fa low
and
.Fa high
arguments
specify minimum and maximum number of unit numbers.
There is no cost associated with the range of unit numbers, so unless the resource
really is finite,
.Dv INT_MAX
can be used.
If
.Fa mutex
is not
.Dv NULL ,
it is used for locking when allocating and freeing units.
Otherwise, internal mutex is used.
.It Fn delete_unrhdr uh
Destroy specified unit number allocator entity.
.It Fn alloc_unr uh
Return a new unit number.
The lowest free number is always allocated.
This function does not allocate memory and never sleeps, however it may
block on a mutex.
If no free unit numbers are left,
.Li \-1
is returned.
.It Fn alloc_unrl uh
Same as
.Fn alloc_unr
except that mutex is assumed to be already locked and thus is not used.
.It Fn alloc_unr_specific uh item
Allocate a specific unit number.
This function allocates memory and thus may sleep.
The allocated unit number is returned on success.
If the specified number is already allocated or out of the range,
.Li \-1
is returned.
.It Fn free_unr uh item
Free a previously allocated unit number.
This function may require allocating memory, and thus it can sleep.
There is no pre-locked variant.
.El
.Sh CODE REFERENCES
The above functions are implemented in
.Pa sys/kern/subr_unit.c .
.Sh HISTORY
Kernel unit number allocator first appeared in
.Fx 6.0 .
.Sh AUTHORS
.An -nosplit
Kernel unit number allocator was written by
.An Poul-Henning Kamp .
This manpage was written by
.An Gleb Smirnoff .
|
