1 files changed, 78 insertions, 0 deletions
diff --git a/include/linux/idr.h b/include/linux/idr.h
new file mode 100644
index 000000000000..ca3b7e462576
--- /dev/null
+++ b/include/linux/idr.h
@@ -0,0 +1,78 @@
+/*
+ * 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.
+ */
+#include <linux/types.h>
+#include <linux/bitops.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	*ary[1<<IDR_BITS];
+	int			 count;	 /* When zero, we can release it */
+};
+
+struct idr {
+	struct idr_layer *top;
+	struct idr_layer *id_free;
+	int		  layers;
+	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,			\
+}
+#define DEFINE_IDR(name)	struct idr name = IDR_INIT(name)
+
+/*
+ * This is what we export.
+ */
+
+void *idr_find(struct idr *idp, int id);
+int idr_pre_get(struct idr *idp, unsigned 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);
+void idr_remove(struct idr *idp, int id);
+void idr_init(struct idr *idp);