include/linux/idr.h

   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 #include <linux/init.h>
  18
  19 #if BITS_PER_LONG == 32
  20 # define IDR_BITS 5
  21 # define IDR_FULL 0xfffffffful
  22 /* We can only use two of the bits in the top level because there is
  23    only one possible bit in the top level (5 bits * 7 levels = 35
  24    bits, but you only use 31 bits in the id). */
  25 # define TOP_LEVEL_FULL (IDR_FULL >> 30)
  26 #elif BITS_PER_LONG == 64
  27 # define IDR_BITS 6
  28 # define IDR_FULL 0xfffffffffffffffful
  29 /* We can only use two of the bits in the top level because there is
  30    only one possible bit in the top level (6 bits * 6 levels = 36
  31    bits, but you only use 31 bits in the id). */
  32 # define TOP_LEVEL_FULL (IDR_FULL >> 62)
  33 #else
  34 # error "BITS_PER_LONG is not 32 or 64"
  35 #endif
  36
  37 #define IDR_SIZE (1 << IDR_BITS)
  38 #define IDR_MASK ((1 << IDR_BITS)-1)
  39
  40 #define MAX_ID_SHIFT (sizeof(int)*8 - 1)
  41 #define MAX_ID_BIT (1U << MAX_ID_SHIFT)
  42 #define MAX_ID_MASK (MAX_ID_BIT - 1)
  43
  44 /* Leave the possibility of an incomplete final layer */
  45 #define MAX_LEVEL (MAX_ID_SHIFT + IDR_BITS - 1) / IDR_BITS
  46
  47 /* Number of id_layer structs to leave in free list */
  48 #define IDR_FREE_MAX MAX_LEVEL + MAX_LEVEL
  49
  50 struct idr_layer {
  51         unsigned long            bitmap; /* A zero bit means "space here" */
  52         struct idr_layer        *ary[1<<IDR_BITS];
  53         int                      count;  /* When zero, we can release it */
  54 };
  55
  56 struct idr {
  57         struct idr_layer *top;
  58         struct idr_layer *id_free;
  59         int               layers;
  60         int               id_free_cnt;
  61         spinlock_t        lock;
  62 };
  63
  64 #define IDR_INIT(name)                                          \
  65 {                                                               \
  66         .top            = NULL,                                 \
  67         .id_free        = NULL,                                 \
  68         .layers         = 0,                                    \
  69         .id_free_cnt    = 0,                                    \
  70         .lock           = __SPIN_LOCK_UNLOCKED(name.lock),      \
  71 }
  72 #define DEFINE_IDR(name)        struct idr name = IDR_INIT(name)
  73
  74 /*
  75  * This is what we export.
  76  */
  77
  78 void *idr_find(struct idr *idp, int id);
  79 int idr_pre_get(struct idr *idp, gfp_t gfp_mask);
  80 int idr_get_new(struct idr *idp, void *ptr, int *id);
  81 int idr_get_new_above(struct idr *idp, void *ptr, int starting_id, int *id);
  82 int idr_for_each(struct idr *idp,
  83                  int (*fn)(int id, void *p, void *data), void *data);
  84 void *idr_replace(struct idr *idp, void *ptr, int id);
  85 void idr_remove(struct idr *idp, int id);
  86 void idr_remove_all(struct idr *idp);
  87 void idr_destroy(struct idr *idp);
  88 void idr_init(struct idr *idp);
  89
  90
  91 /*
  92  * IDA - IDR based id allocator, use when translation from id to
  93  * pointer isn't necessary.
  94  */
  95 #define IDA_CHUNK_SIZE          128     /* 128 bytes per chunk */
  96 #define IDA_BITMAP_LONGS        (128 / sizeof(long) - 1)
  97 #define IDA_BITMAP_BITS         (IDA_BITMAP_LONGS * sizeof(long) * 8)
  98
  99 struct ida_bitmap {
 100         long                    nr_busy;
 101         unsigned long           bitmap[IDA_BITMAP_LONGS];
 102 };
 103
 104 struct ida {
 105         struct idr              idr;
 106         struct ida_bitmap       *free_bitmap;
 107 };
 108
 109 #define IDA_INIT(name)          { .idr = IDR_INIT(name), .free_bitmap = NULL, }
 110 #define DEFINE_IDA(name)        struct ida name = IDA_INIT(name)
 111
 112 int ida_pre_get(struct ida *ida, gfp_t gfp_mask);
 113 int ida_get_new_above(struct ida *ida, int starting_id, int *p_id);
 114 int ida_get_new(struct ida *ida, int *p_id);
 115 void ida_remove(struct ida *ida, int id);
 116 void ida_destroy(struct ida *ida);
 117 void ida_init(struct ida *ida);
 118
 119 void __init idr_init_cache(void);
 120
 121 #endif /* __IDR_H__ */