introduce struct kobject: simple, generic object for embedding in other structures.

This is not meant to be fancy; just something simple for which we can 
control the refcount and other common functionality using common code. 
   
The basic operations for registration and reference count manipulation are
included. 

include/linux/kobject.h

+/*
+ * kobject.h - generic kernel object infrastructure.
+ *
+ */
+
+#ifndef _KOBJECT_H_
+#define _KOBJECT_H_
+
+#include <linux/types.h>
+#include <linux/list.h>
+#include <linux/sysfs.h>
+#include <asm/atomic.h>
+
+struct kobject {
+	char			name[16];
+	atomic_t		refcount;
+	struct list_head	entry;
+	struct kobject		* parent;
+};
+
+extern void kobject_init(struct kobject *);
+
+extern int kobject_register(struct kobject *);
+extern void kobject_unregister(struct kobject *);
+
+extern struct kobject * kobject_get(struct kobject *);
+extern void kobject_put(struct kobject *);
+
+#endif /* _KOBJECT_H_ */

lib/Makefile

@@ -9,10 +9,11 @@
 L_TARGET := lib.a
 
 export-objs := cmdline.o dec_and_lock.o rwsem-spinlock.o rwsem.o \
-	       crc32.o rbtree.o radix-tree.o
+	       crc32.o rbtree.o radix-tree.o kobject.o
 
 obj-y := errno.o ctype.o string.o vsprintf.o brlock.o cmdline.o \
-	 bust_spinlocks.o rbtree.o radix-tree.o dump_stack.o
+	 bust_spinlocks.o rbtree.o radix-tree.o dump_stack.o \
+	 kobject.o
 
 obj-$(CONFIG_RWSEM_GENERIC_SPINLOCK) += rwsem-spinlock.o
 obj-$(CONFIG_RWSEM_XCHGADD_ALGORITHM) += rwsem.o

lib/kobject.c

+/*
+ * kobject.c - library routines for handling generic kernel objects
+ */
+
+#define DEBUG 1
+
+#include <linux/kobject.h>
+#include <linux/module.h>
+#include <linux/stat.h>
+
+/**
+ *	kobject_init - initialize object.
+ *	@kobj:	object in question.
+ */
+
+void kobject_init(struct kobject * kobj)
+{
+	atomic_set(&kobj->refcount,1);
+	INIT_LIST_HEAD(&kobj->entry);
+}
+
+/**
+ *	kobject_register - register an object.
+ *	@kobj:	object in question.
+ *
+ *	For now, fill in the replicated fields in the object's
+ *	directory entry, and create a dir in sysfs. 
+ *	This stuff should go away in the future, as we move
+ *	more implicit things to sysfs.
+ */
+
+int kobject_register(struct kobject * kobj)
+{
+	pr_debug("kobject %s: registering\n",kobj->name);
+	if (kobj->parent)
+		kobject_get(kobj->parent);
+	return 0;
+}
+
+/**
+ *	kobject_unregister - unlink an object.
+ *	@kobj:	object going away.
+ *
+ *	The device has been told to be removed, but may
+ *	not necessarily be disappearing from the kernel.
+ *	So, we remove the directory and decrement the refcount
+ *	that we set with kobject_register().
+ *
+ *	Eventually (maybe now), the refcount will hit 0, and 
+ *	put_device() will clean the device up.
+ */
+
+void kobject_unregister(struct kobject * kobj)
+{
+	pr_debug("kobject %s: unregistering\n",kobj->name);
+	kobject_put(kobj);
+}
+
+/**
+ *	kobject_get - increment refcount for object.
+ *	@kobj:	object.
+ */
+
+struct kobject * kobject_get(struct kobject * kobj)
+{
+	struct kobject * ret = kobj;
+	if (atomic_read(&kobj->refcount) > 0)
+		atomic_inc(&kobj->refcount);
+	else
+		ret = NULL;
+	return ret;
+}
+
+/**
+ *	kobject_put - decrement refcount for object.
+ *	@kobj:	object.
+ *
+ *	Decrement the refcount, and check if 0. If it is, then 
+ *	we're gonna need to clean it up, and decrement the refcount
+ *	of its parent.
+ */
+
+void kobject_put(struct kobject * kobj)
+{
+	struct kobject * parent = kobj->parent;
+
+	if (!atomic_dec_and_test(&kobj->refcount))
+		return;
+	pr_debug("kobject %s: cleaning up\n",kobj->name);
+	if (parent)
+		kobject_put(parent);
+}
+
+EXPORT_SYMBOL(kobject_init);
+EXPORT_SYMBOL(kobject_register);
+EXPORT_SYMBOL(kobject_unregister);
+EXPORT_SYMBOL(kobject_get);
+EXPORT_SYMBOL(kobject_put);