/*
   * include/linux/idr.h
   * 
   * 2002-10-18  written by Jim Houston jim.houston@ccur.com
   *	Copyright (C) 2002 by Concurrent Computer Corporation
   *	Distributed under the GNU GPL license version 2.
   *
   * Small id to pointer translation service avoiding fixed sized
   * tables.
   */

  
  #ifndef __IDR_H__
  #define __IDR_H__

  #include <linux/types.h>
  #include <linux/bitops.h>

  #include <linux/init.h>

  #include <linux/rcupdate.h>

  
  #if BITS_PER_LONG == 32
  # define IDR_BITS 5
  # define IDR_FULL 0xfffffffful
  /* We can only use two of the bits in the top level because there is
     only one possible bit in the top level (5 bits * 7 levels = 35
     bits, but you only use 31 bits in the id). */
  # define TOP_LEVEL_FULL (IDR_FULL >> 30)
  #elif BITS_PER_LONG == 64
  # define IDR_BITS 6
  # define IDR_FULL 0xfffffffffffffffful
  /* We can only use two of the bits in the top level because there is
     only one possible bit in the top level (6 bits * 6 levels = 36
     bits, but you only use 31 bits in the id). */
  # define TOP_LEVEL_FULL (IDR_FULL >> 62)
  #else
  # error "BITS_PER_LONG is not 32 or 64"
  #endif
  
  #define IDR_SIZE (1 << IDR_BITS)
  #define IDR_MASK ((1 << IDR_BITS)-1)
  
  #define MAX_ID_SHIFT (sizeof(int)*8 - 1)
  #define MAX_ID_BIT (1U << MAX_ID_SHIFT)
  #define MAX_ID_MASK (MAX_ID_BIT - 1)
  
  /* Leave the possibility of an incomplete final layer */
  #define MAX_LEVEL (MAX_ID_SHIFT + IDR_BITS - 1) / IDR_BITS
  
  /* Number of id_layer structs to leave in free list */
  #define IDR_FREE_MAX MAX_LEVEL + MAX_LEVEL
  
  struct idr_layer {
  	unsigned long		 bitmap; /* A zero bit means "space here" */

  	struct idr_layer __rcu	*ary[1<<IDR_BITS];

  	int			 count;	 /* When zero, we can release it */

  	int			 layer;	 /* distance from leaf */

  	struct rcu_head		 rcu_head;

  };
  
  struct idr {

  	struct idr_layer __rcu *top;

  	struct idr_layer *id_free;

  	int		  layers; /* only valid without concurrent changes */

  	int		  id_free_cnt;
  	spinlock_t	  lock;
  };
  
  #define IDR_INIT(name)						\
  {								\
  	.top		= NULL,					\
  	.id_free	= NULL,					\
  	.layers 	= 0,					\
  	.id_free_cnt	= 0,					\

  	.lock		= __SPIN_LOCK_UNLOCKED(name.lock),	\

  }
  #define DEFINE_IDR(name)	struct idr name = IDR_INIT(name)

  /* Actions to be taken after a call to _idr_sub_alloc */
  #define IDR_NEED_TO_GROW -2
  #define IDR_NOMORE_SPACE -3
  
  #define _idr_rc_to_errno(rc) ((rc) == -1 ? -EAGAIN : -ENOSPC)

  /**

   * DOC: idr sync

   * idr synchronization (stolen from radix-tree.h)
   *
   * idr_find() is able to be called locklessly, using RCU. The caller must
   * ensure calls to this function are made within rcu_read_lock() regions.
   * Other readers (lock-free or otherwise) and modifications may be running
   * concurrently.
   *
   * It is still required that the caller manage the synchronization and
   * lifetimes of the items. So if RCU lock-free lookups are used, typically
   * this would mean that the items have their own locks, or are amenable to
   * lock-free access; and that the items are freed by RCU (or only freed after
   * having been deleted from the idr tree *and* a synchronize_rcu() grace
   * period).
   */

  /*
   * This is what we export.
   */
  
  void *idr_find(struct idr *idp, int id);

  int idr_pre_get(struct idr *idp, gfp_t gfp_mask);

  int idr_get_new(struct idr *idp, void *ptr, int *id);
  int idr_get_new_above(struct idr *idp, void *ptr, int starting_id, int *id);

  int idr_for_each(struct idr *idp,
  		 int (*fn)(int id, void *p, void *data), void *data);

  void *idr_get_next(struct idr *idp, int *nextid);

  void *idr_replace(struct idr *idp, void *ptr, int id);

  void idr_remove(struct idr *idp, int id);

  void idr_remove_all(struct idr *idp);

  void idr_destroy(struct idr *idp);

  void idr_init(struct idr *idp);

  
  /*
   * IDA - IDR based id allocator, use when translation from id to
   * pointer isn't necessary.

   *
   * IDA_BITMAP_LONGS is calculated to be one less to accommodate
   * ida_bitmap->nr_busy so that the whole struct fits in 128 bytes.

   */
  #define IDA_CHUNK_SIZE		128	/* 128 bytes per chunk */

  #define IDA_BITMAP_LONGS	(IDA_CHUNK_SIZE / sizeof(long) - 1)
  #define IDA_BITMAP_BITS 	(IDA_BITMAP_LONGS * sizeof(long) * 8)

  
  struct ida_bitmap {
  	long			nr_busy;
  	unsigned long		bitmap[IDA_BITMAP_LONGS];
  };
  
  struct ida {
  	struct idr		idr;
  	struct ida_bitmap	*free_bitmap;
  };
  
  #define IDA_INIT(name)		{ .idr = IDR_INIT(name), .free_bitmap = NULL, }
  #define DEFINE_IDA(name)	struct ida name = IDA_INIT(name)
  
  int ida_pre_get(struct ida *ida, gfp_t gfp_mask);
  int ida_get_new_above(struct ida *ida, int starting_id, int *p_id);
  int ida_get_new(struct ida *ida, int *p_id);
  void ida_remove(struct ida *ida, int id);
  void ida_destroy(struct ida *ida);
  void ida_init(struct ida *ida);

  int ida_simple_get(struct ida *ida, unsigned int start, unsigned int end,
  		   gfp_t gfp_mask);
  void ida_simple_remove(struct ida *ida, unsigned int id);

  void __init idr_init_cache(void);

  #endif /* __IDR_H__ */