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34 .Nm alloc_unr_specific ,
36 .Nd "kernel unit number allocator"
40 .Fn new_unrhdr "int low" "int high" "struct mtx *mutex"
42 .Fn delete_unrhdr "struct unrhdr *uh"
44 .Fn alloc_unr "struct unrhdr *uh"
46 .Fn alloc_unrl "struct unrhdr *uh"
48 .Fn alloc_unr_specific "struct unrhdr *uh" "u_int item"
50 .Fn free_unr "struct unrhdr *uh" "u_int item"
52 The kernel unit number allocator is a generic facility, which allows to allocate
53 unit numbers within a specified range.
54 .Bl -tag -width indent
55 .It Fn new_unrhdr low high mutex
56 Initialize a new unit number allocator entity.
62 specify minimum and maximum number of unit numbers.
63 There is no cost associated with the range of unit numbers, so unless the resource
71 it is used for locking when allocating and freeing units.
72 Otherwise, internal mutex is used.
73 .It Fn delete_unrhdr uh
74 Destroy specified unit number allocator entity.
76 Return a new unit number.
77 The lowest free number is always allocated.
78 This function does not allocate memory and never sleeps, however it may
80 If no free unit numbers are left,
86 except that mutex is assumed to be already locked and thus is not used.
87 .It Fn alloc_unr_specific uh item
88 Allocate a specific unit number.
89 This function allocates memory and thus may sleep.
90 The allocated unit number is returned on success.
91 If the specified number is already allocated or out of the range,
94 .It Fn free_unr uh item
95 Free a previously allocated unit number.
96 This function may require allocating memory, and thus it can sleep.
97 There is no pre-locked variant.
100 The above functions are implemented in
101 .Pa sys/kern/subr_unit.c .
103 Kernel unit number allocator first appeared in
107 Kernel unit number allocator was written by
108 .An Poul-Henning Kamp .
109 This manpage was written by