idr.h 2.4 KB

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