1/*
2 * include/linux/idr.h
3 *
4 * 2002-10-18  written by Jim Houston jim.houston@ccur.com
5 *	Copyright (C) 2002 by Concurrent Computer Corporation
6 *	Distributed under the GNU GPL license version 2.
7 *
8 * Small id to pointer translation service avoiding fixed sized
9 * tables.
10 */
11
12#ifndef __IDR_H__
13#define __IDR_H__
14
15#include <linux/types.h>
16#include <linux/bitops.h>
17
18#if BITS_PER_LONG == 32
19# define IDR_BITS 5
20# define IDR_FULL 0xfffffffful
21/* We can only use two of the bits in the top level because there is
22   only one possible bit in the top level (5 bits * 7 levels = 35
23   bits, but you only use 31 bits in the id). */
24# define TOP_LEVEL_FULL (IDR_FULL >> 30)
25#elif BITS_PER_LONG == 64
26# define IDR_BITS 6
27# define IDR_FULL 0xfffffffffffffffful
28/* We can only use two of the bits in the top level because there is
29   only one possible bit in the top level (6 bits * 6 levels = 36
30   bits, but you only use 31 bits in the id). */
31# define TOP_LEVEL_FULL (IDR_FULL >> 62)
32#else
33# error "BITS_PER_LONG is not 32 or 64"
34#endif
35
36#define IDR_SIZE (1 << IDR_BITS)
37#define IDR_MASK ((1 << IDR_BITS)-1)
38
39#define MAX_ID_SHIFT (sizeof(int)*8 - 1)
40#define MAX_ID_BIT (1U << MAX_ID_SHIFT)
41#define MAX_ID_MASK (MAX_ID_BIT - 1)
42
43/* Leave the possibility of an incomplete final layer */
44#define MAX_LEVEL (MAX_ID_SHIFT + IDR_BITS - 1) / IDR_BITS
45
46/* Number of id_layer structs to leave in free list */
47#define IDR_FREE_MAX MAX_LEVEL + MAX_LEVEL
48
49struct idr_layer {
50	unsigned long		 bitmap; /* A zero bit means "space here" */
51	struct idr_layer	*ary[1<<IDR_BITS];
52	int			 count;	 /* When zero, we can release it */
53};
54
55struct idr {
56	struct idr_layer *top;
57	struct idr_layer *id_free;
58	int		  layers;
59	int		  id_free_cnt;
60	spinlock_t	  lock;
61};
62
63#define IDR_INIT(name)						\
64{								\
65	.top		= NULL,					\
66	.id_free	= NULL,					\
67	.layers 	= 0,					\
68	.id_free_cnt	= 0,					\
69	.lock		= __SPIN_LOCK_UNLOCKED(name.lock),	\
70}
71#define DEFINE_IDR(name)	struct idr name = IDR_INIT(name)
72
73/*
74 * This is what we export.
75 */
76
77void *idr_find(struct idr *idp, int id);
78int idr_pre_get(struct idr *idp, gfp_t gfp_mask);
79int idr_get_new(struct idr *idp, void *ptr, int *id);
80int idr_get_new_above(struct idr *idp, void *ptr, int starting_id, int *id);
81void *idr_replace(struct idr *idp, void *ptr, int id);
82void idr_remove(struct idr *idp, int id);
83void idr_destroy(struct idr *idp);
84void idr_init(struct idr *idp);
85
86#endif /* __IDR_H__ */
87