ALLOC_UNR(9) MidnightBSD Kernel Developer’s Manual ALLOC_UNR(9)

NAME

new_unrhdr, delete_unrhdr, alloc_unr, free_unr — kernel unit number allocator

SYNOPSIS

#include <sys/systm.h>

struct unrhdr *

new_unrhdr(int low, int high, struct mtx *mutex);

void

delete_unrhdr(struct unrhdr *uh);

int

alloc_unr(struct unrhdr *uh);

int

alloc_unrl(struct unrhdr *uh);

void

free_unr(struct unrhdr *uh, u_int item);

DESCRIPTION

The kernel unit number allocator is a generic facility, which allows to allocate unit numbers within a specified range.

new_unrhdr(low, high, mutex)

Initialize a new unit number allocator entity. The low and 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, INT_MAX can be used. If mutex is not NULL, it is used for locking when allocating and freeing units. Otherwise, internal mutex is used.

delete_unrhdr(uh)

Destroy specified unit number allocator entity.

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, −1 is returned.

alloc_unrl(uh)

Same as alloc_unr() except that mutex is assumed to be already locked and thus is not used.

free_unr(uh)

Free a previously allocated unit number. This function may require allocating memory, and thus it can sleep. There is no pre-locked variant.

CODE REFERENCES

The above functions are implemented in sys/kern/subr_unit.c.

HISTORY

Kernel unit number allocator first appeared in FreeBSD 6.0.

AUTHORS

Kernel unit number allocator was written by Poul-Henning Kamp. This manpage was written by Gleb Smirnoff.

MidnightBSD 0.3 March 23, 2005 MidnightBSD 0.3