--- /dev/null
+/*
+ * 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/bitmap.h>
+#include <linux/bitops.h>
+#include <linux/preempt.h>
+#include <linux/rcupdate.h>
+#include <linux/spinlock.h>
+
+/*
+ * We want shallower trees and thus more bits covered at each layer. 8
+ * bits gives us large enough first layer for most use cases and maximum
+ * tree depth of 4. Each idr_layer is slightly larger than 2k on 64bit and
+ * 1k on 32bit.
+ */
+#define IDR_BITS 8
+#define IDR_SIZE (1 << IDR_BITS)
+#define IDR_MASK ((1 << IDR_BITS)-1)
+
+struct idr_layer {
+ int prefix; /* the ID prefix of this idr_layer */
+ int layer; /* distance from leaf */
+ struct idr_layer __rcu *ary[1<<IDR_BITS];
+ int count; /* When zero, we can release it */
+ union {
+ /* A zero bit means "space here" */
+ DECLARE_BITMAP(bitmap, IDR_SIZE);
+ struct rcu_head rcu_head;
+ };
+};
+
+struct idr {
+ struct idr_layer __rcu *hint; /* the last layer allocated from */
+ struct idr_layer __rcu *top;
+ int layers; /* only valid w/o concurrent changes */
+ int cur; /* current pos for cyclic allocation */
+ spinlock_t lock;
+ int id_free_cnt;
+ struct idr_layer *id_free;
+};
+
+#define IDR_INIT(name) \
+{ \
+ .lock = __SPIN_LOCK_UNLOCKED(name.lock), \
+}
+#define DEFINE_IDR(name) struct idr name = IDR_INIT(name)
+
+/**
+ * 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_slowpath(struct idr *idp, int id);
+void idr_preload(gfp_t gfp_mask);
+
+static inline int idr_alloc(struct idr *idp, void *ptr, int start, int end, gfp_t gfp_mask)
+{
+ return 0;
+}
+
+static inline void idr_remove(struct idr *idp, int id) {}
+
+int idr_alloc_cyclic(struct idr *idr, void *ptr, int start, int end, gfp_t gfp_mask);
+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_destroy(struct idr *idp);
+void idr_init(struct idr *idp);
+bool idr_is_empty(struct idr *idp);
+
+/**
+ * idr_preload_end - end preload section started with idr_preload()
+ *
+ * Each idr_preload() should be matched with an invocation of this
+ * function. See idr_preload() for details.
+ */
+static inline void idr_preload_end(void)
+{
+ preempt_enable();
+}
+
+/**
+ * idr_find - return pointer for given id
+ * @idr: idr handle
+ * @id: lookup key
+ *
+ * Return the pointer given the id it has been registered with. A %NULL
+ * return indicates that @id is not valid or you passed %NULL in
+ * idr_get_new().
+ *
+ * This function can be called under rcu_read_lock(), given that the leaf
+ * pointers lifetimes are correctly managed.
+ */
+static inline void *idr_find(struct idr *idr, int id)
+{
+ struct idr_layer *hint = rcu_dereference_raw(idr->hint);
+
+ if (hint && (id & ~IDR_MASK) == hint->prefix)
+ return rcu_dereference_raw(hint->ary[id & IDR_MASK]);
+
+ return idr_find_slowpath(idr, id);
+}
+
+/**
+ * idr_for_each_entry - iterate over an idr's elements of a given type
+ * @idp: idr handle
+ * @entry: the type * to use as cursor
+ * @id: id entry's key
+ *
+ * @entry and @id do not need to be initialized before the loop, and
+ * after normal terminatinon @entry is left with the value NULL. This
+ * is convenient for a "not found" value.
+ */
+#define idr_for_each_entry(idp, entry, id) \
+ for (id = 0; ((entry) = idr_get_next(idp, &(id))) != NULL; ++id)
+
+/**
+ * idr_for_each_entry - continue iteration over an idr's elements of a given type
+ * @idp: idr handle
+ * @entry: the type * to use as cursor
+ * @id: id entry's key
+ *
+ * Continue to iterate over list of given type, continuing after
+ * the current position.
+ */
+#define idr_for_each_entry_continue(idp, entry, id) \
+ for ((entry) = idr_get_next((idp), &(id)); \
+ entry; \
+ ++id, (entry) = idr_get_next((idp), &(id)))
+
+/*
+ * 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).idr), .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);
+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);
+
+/**
+ * ida_get_new - allocate new ID
+ * @ida: idr handle
+ * @p_id: pointer to the allocated handle
+ *
+ * Simple wrapper around ida_get_new_above() w/ @starting_id of zero.
+ */
+static inline int ida_get_new(struct ida *ida, int *p_id)
+{
+ return ida_get_new_above(ida, 0, p_id);
+}
+
+void __init idr_init_cache(void);
+
+#endif /* __IDR_H__ */
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