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 #include <linux/types.h>
  12 #include <linux/bitops.h>
  13
  14 #if BITS_PER_LONG == 32
  15 # define IDR_BITS 5
  16 # define IDR_FULL 0xfffffffful
  17 /* We can only use two of the bits in the top level because there is
  18    only one possible bit in the top level (5 bits * 7 levels = 35
  19    bits, but you only use 31 bits in the id). */
  20 # define TOP_LEVEL_FULL (IDR_FULL >> 30)
  21 #elif BITS_PER_LONG == 64
  22 # define IDR_BITS 6
  23 # define IDR_FULL 0xfffffffffffffffful
  24 /* We can only use two of the bits in the top level because there is
  25    only one possible bit in the top level (6 bits * 6 levels = 36
  26    bits, but you only use 31 bits in the id). */
  27 # define TOP_LEVEL_FULL (IDR_FULL >> 62)
  28 #else
  29 # error "BITS_PER_LONG is not 32 or 64"
  30 #endif
  31
  32 #define IDR_SIZE (1 << IDR_BITS)
  33 #define IDR_MASK ((1 << IDR_BITS)-1)
  34
  35 #define MAX_ID_SHIFT (sizeof(int)*8 - 1)
  36 #define MAX_ID_BIT (1U << MAX_ID_SHIFT)
  37 #define MAX_ID_MASK (MAX_ID_BIT - 1)
  38
  39 /* Leave the possibility of an incomplete final layer */
  40 #define MAX_LEVEL (MAX_ID_SHIFT + IDR_BITS - 1) / IDR_BITS
  41
  42 /* Number of id_layer structs to leave in free list */
  43 #define IDR_FREE_MAX MAX_LEVEL + MAX_LEVEL
  44
  45 struct idr_layer {
  46         unsigned long            bitmap; /* A zero bit means "space here" */
  47         struct idr_layer        *ary[1<<IDR_BITS];
  48         int                      count;  /* When zero, we can release it */
  49 };
  50
  51 struct idr {
  52         struct idr_layer *top;
  53         struct idr_layer *id_free;
  54         int               layers;
  55         int               id_free_cnt;
  56         spinlock_t        lock;
  57 };
  58
  59 #define IDR_INIT(name)                                          \
  60 {                                                               \
  61         .top            = NULL,                                 \
  62         .id_free        = NULL,                                 \
  63         .layers         = 0,                                    \
  64         .id_free_cnt    = 0,                                    \
  65         .lock           = SPIN_LOCK_UNLOCKED,                   \
  66 }
  67 #define DEFINE_IDR(name)        struct idr name = IDR_INIT(name)
  68
  69 /*
  70  * This is what we export.
  71  */
  72
  73 void *idr_find(struct idr *idp, int id);
  74 int idr_pre_get(struct idr *idp, unsigned gfp_mask);
  75 int idr_get_new(struct idr *idp, void *ptr, int *id);
  76 int idr_get_new_above(struct idr *idp, void *ptr, int starting_id, int *id);
  77 void idr_remove(struct idr *idp, int id);
  78 void idr_init(struct idr *idp);