[PATCH 23/23] configfs: remove old API

From: Christoph Hellwig <hch@lst.de>
To: Joel Becker <jlbec@evilplan.org>,
	Andrew Morton <akpm@linux-foundation.org>
Cc: Felipe Balbi <balbi@ti.com>, Tejun Heo <tj@kernel.org>,
	Pratyush Anand <pratyush.anand@gmail.com>,
	target-devel@vger.kernel.org, cluster-devel@redhat.com,
	ocfs2-devel@oss.oracle.com, linux-usb@vger.kernel.org,
	netdev@vger.kernel.org
Subject: [PATCH 23/23] configfs: remove old API
Date: Fri, 25 Sep 2015 06:50:00 -0700	[thread overview]
Message-ID: <1443189000-13398-24-git-send-email-hch@lst.de> (raw)
In-Reply-To: <1443189000-13398-1-git-send-email-hch@lst.de>

Remove the old show_attribute and store_attribute methods and update
the documentation.  Also replace the two C samples with a single new
one in the proper samples directory where people expect to find it.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 Documentation/filesystems/Makefile                 |   2 -
 Documentation/filesystems/configfs/Makefile        |   3 -
 Documentation/filesystems/configfs/configfs.txt    |  43 +-
 .../configfs/configfs_example_explicit.c           | 483 ---------------------
 .../filesystems/configfs/configfs_example_macros.c | 446 -------------------
 fs/configfs/file.c                                 |  15 +-
 include/linux/configfs.h                           |  82 ----
 samples/Makefile                                   |   3 +-
 samples/configfs/Makefile                          |   2 +
 samples/configfs/configfs_sample.c                 | 404 +++++++++++++++++
 10 files changed, 427 insertions(+), 1056 deletions(-)
 delete mode 100644 Documentation/filesystems/configfs/Makefile
 delete mode 100644 Documentation/filesystems/configfs/configfs_example_explicit.c
 delete mode 100644 Documentation/filesystems/configfs/configfs_example_macros.c
 create mode 100644 samples/configfs/Makefile
 create mode 100644 samples/configfs/configfs_sample.c

diff --git a/Documentation/filesystems/Makefile b/Documentation/filesystems/Makefile
index 13483d1..883010c 100644
--- a/Documentation/filesystems/Makefile
+++ b/Documentation/filesystems/Makefile
@@ -1,5 +1,3 @@
-subdir-y := configfs
-
 # List of programs to build
 hostprogs-y := dnotify_test
 
diff --git a/Documentation/filesystems/configfs/Makefile b/Documentation/filesystems/configfs/Makefile
deleted file mode 100644
index be7ec5e..0000000
--- a/Documentation/filesystems/configfs/Makefile
+++ /dev/null
@@ -1,3 +0,0 @@
-ifneq ($(CONFIG_CONFIGFS_FS),)
-obj-m += configfs_example_explicit.o configfs_example_macros.o
-endif
diff --git a/Documentation/filesystems/configfs/configfs.txt b/Documentation/filesystems/configfs/configfs.txt
index b40fec9..f51d04f 100644
--- a/Documentation/filesystems/configfs/configfs.txt
+++ b/Documentation/filesystems/configfs/configfs.txt
@@ -160,12 +160,6 @@ among other things.  For that, it needs a type.
 
 	struct configfs_item_operations {
 		void (*release)(struct config_item *);
-		ssize_t (*show_attribute)(struct config_item *,
-					  struct configfs_attribute *,
-					  char *);
-		ssize_t (*store_attribute)(struct config_item *,
-					   struct configfs_attribute *,
-					   const char *, size_t);
 		int (*allow_link)(struct config_item *src,
 				  struct config_item *target);
 		int (*drop_link)(struct config_item *src,
@@ -183,9 +177,7 @@ The most basic function of a config_item_type is to define what
 operations can be performed on a config_item.  All items that have been
 allocated dynamically will need to provide the ct_item_ops->release()
 method.  This method is called when the config_item's reference count
-reaches zero.  Items that wish to display an attribute need to provide
-the ct_item_ops->show_attribute() method.  Similarly, storing a new
-attribute value uses the store_attribute() method.
+reaches zero.
 
 [struct configfs_attribute]
 
@@ -193,6 +185,8 @@ attribute value uses the store_attribute() method.
 		char                    *ca_name;
 		struct module           *ca_owner;
 		umode_t                  ca_mode;
+		ssize_t (*show)(struct config_item *, char *);
+		ssize_t (*store)(struct config_item *, const char *, size_t);
 	};
 
 When a config_item wants an attribute to appear as a file in the item's
@@ -202,10 +196,15 @@ config_item_type->ct_attrs.  When the item appears in configfs, the
 attribute file will appear with the configfs_attribute->ca_name
 filename.  configfs_attribute->ca_mode specifies the file permissions.
 
-If an attribute is readable and the config_item provides a
-ct_item_ops->show_attribute() method, that method will be called
-whenever userspace asks for a read(2) on the attribute.  The converse
-will happen for write(2).
+Items that wish to display an attribute need to provide
+the ct_item_ops->show_attribute() method.  Similarly, storing a new
+attribute value uses the store_attribute() method.
+
+
+If an attribute is readable and provides a ->show method, that method will
+be called whenever userspace asks for a read(2) on the attribute.  If an
+attribute is writable and provides a ->store  method, that method will be
+be called whenever userspace asks for a write(2) on the attribute.
 
 [struct config_group]
 
@@ -311,20 +310,10 @@ the subsystem must be ready for it.
 [An Example]
 
 The best example of these basic concepts is the simple_children
-subsystem/group and the simple_child item in configfs_example_explicit.c
-and configfs_example_macros.c.  It shows a trivial object displaying and
-storing an attribute, and a simple group creating and destroying these
-children.
-
-The only difference between configfs_example_explicit.c and
-configfs_example_macros.c is how the attributes of the childless item
-are defined.  The childless item has extended attributes, each with
-their own show()/store() operation.  This follows a convention commonly
-used in sysfs.  configfs_example_explicit.c creates these attributes
-by explicitly defining the structures involved.  Conversely
-configfs_example_macros.c uses some convenience macros from configfs.h
-to define the attributes.  These macros are similar to their sysfs
-counterparts.
+subsystem/group and the simple_child item in
+samples/configfs/configfs_sample.c. It shows a trivial object displaying
+and storing an attribute, and a simple group creating and destroying
+these children.
 
 [Hierarchy Navigation and the Subsystem Mutex]
 
diff --git a/Documentation/filesystems/configfs/configfs_example_explicit.c b/Documentation/filesystems/configfs/configfs_example_explicit.c
deleted file mode 100644
index 1420233..0000000
--- a/Documentation/filesystems/configfs/configfs_example_explicit.c
+++ /dev/null
@@ -1,483 +0,0 @@
-/*
- * vim: noexpandtab ts=8 sts=0 sw=8:
- *
- * configfs_example_explicit.c - This file is a demonstration module
- *      containing a number of configfs subsystems.  It explicitly defines
- *      each structure without using the helper macros defined in
- *      configfs.h.
- *
- * This program is free software; you can redistribute it and/or
- * modify it under the terms of the GNU General Public
- * License as published by the Free Software Foundation; either
- * version 2 of the License, or (at your option) any later version.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
- * General Public License for more details.
- *
- * You should have received a copy of the GNU General Public
- * License along with this program; if not, write to the
- * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
- * Boston, MA 021110-1307, USA.
- *
- * Based on sysfs:
- * 	sysfs is Copyright (C) 2001, 2002, 2003 Patrick Mochel
- *
- * configfs Copyright (C) 2005 Oracle.  All rights reserved.
- */
-
-#include <linux/init.h>
-#include <linux/module.h>
-#include <linux/slab.h>
-
-#include <linux/configfs.h>
-
-
-
-/*
- * 01-childless
- *
- * This first example is a childless subsystem.  It cannot create
- * any config_items.  It just has attributes.
- *
- * Note that we are enclosing the configfs_subsystem inside a container.
- * This is not necessary if a subsystem has no attributes directly
- * on the subsystem.  See the next example, 02-simple-children, for
- * such a subsystem.
- */
-
-struct childless {
-	struct configfs_subsystem subsys;
-	int showme;
-	int storeme;
-};
-
-struct childless_attribute {
-	struct configfs_attribute attr;
-	ssize_t (*show)(struct childless *, char *);
-	ssize_t (*store)(struct childless *, const char *, size_t);
-};
-
-static inline struct childless *to_childless(struct config_item *item)
-{
-	return item ? container_of(to_configfs_subsystem(to_config_group(item)), struct childless, subsys) : NULL;
-}
-
-static ssize_t childless_showme_read(struct childless *childless,
-				     char *page)
-{
-	ssize_t pos;
-
-	pos = sprintf(page, "%d\n", childless->showme);
-	childless->showme++;
-
-	return pos;
-}
-
-static ssize_t childless_storeme_read(struct childless *childless,
-				      char *page)
-{
-	return sprintf(page, "%d\n", childless->storeme);
-}
-
-static ssize_t childless_storeme_write(struct childless *childless,
-				       const char *page,
-				       size_t count)
-{
-	unsigned long tmp;
-	char *p = (char *) page;
-
-	tmp = simple_strtoul(p, &p, 10);
-	if ((*p != '\0') && (*p != '\n'))
-		return -EINVAL;
-
-	if (tmp > INT_MAX)
-		return -ERANGE;
-
-	childless->storeme = tmp;
-
-	return count;
-}
-
-static ssize_t childless_description_read(struct childless *childless,
-					  char *page)
-{
-	return sprintf(page,
-"[01-childless]\n"
-"\n"
-"The childless subsystem is the simplest possible subsystem in\n"
-"configfs.  It does not support the creation of child config_items.\n"
-"It only has a few attributes.  In fact, it isn't much different\n"
-"than a directory in /proc.\n");
-}
-
-static struct childless_attribute childless_attr_showme = {
-	.attr	= { .ca_owner = THIS_MODULE, .ca_name = "showme", .ca_mode = S_IRUGO },
-	.show	= childless_showme_read,
-};
-static struct childless_attribute childless_attr_storeme = {
-	.attr	= { .ca_owner = THIS_MODULE, .ca_name = "storeme", .ca_mode = S_IRUGO | S_IWUSR },
-	.show	= childless_storeme_read,
-	.store	= childless_storeme_write,
-};
-static struct childless_attribute childless_attr_description = {
-	.attr = { .ca_owner = THIS_MODULE, .ca_name = "description", .ca_mode = S_IRUGO },
-	.show = childless_description_read,
-};
-
-static struct configfs_attribute *childless_attrs[] = {
-	&childless_attr_showme.attr,
-	&childless_attr_storeme.attr,
-	&childless_attr_description.attr,
-	NULL,
-};
-
-static ssize_t childless_attr_show(struct config_item *item,
-				   struct configfs_attribute *attr,
-				   char *page)
-{
-	struct childless *childless = to_childless(item);
-	struct childless_attribute *childless_attr =
-		container_of(attr, struct childless_attribute, attr);
-	ssize_t ret = 0;
-
-	if (childless_attr->show)
-		ret = childless_attr->show(childless, page);
-	return ret;
-}
-
-static ssize_t childless_attr_store(struct config_item *item,
-				    struct configfs_attribute *attr,
-				    const char *page, size_t count)
-{
-	struct childless *childless = to_childless(item);
-	struct childless_attribute *childless_attr =
-		container_of(attr, struct childless_attribute, attr);
-	ssize_t ret = -EINVAL;
-
-	if (childless_attr->store)
-		ret = childless_attr->store(childless, page, count);
-	return ret;
-}
-
-static struct configfs_item_operations childless_item_ops = {
-	.show_attribute		= childless_attr_show,
-	.store_attribute	= childless_attr_store,
-};
-
-static struct config_item_type childless_type = {
-	.ct_item_ops	= &childless_item_ops,
-	.ct_attrs	= childless_attrs,
-	.ct_owner	= THIS_MODULE,
-};
-
-static struct childless childless_subsys = {
-	.subsys = {
-		.su_group = {
-			.cg_item = {
-				.ci_namebuf = "01-childless",
-				.ci_type = &childless_type,
-			},
-		},
-	},
-};
-
-
-/* ----------------------------------------------------------------- */
-
-/*
- * 02-simple-children
- *
- * This example merely has a simple one-attribute child.  Note that
- * there is no extra attribute structure, as the child's attribute is
- * known from the get-go.  Also, there is no container for the
- * subsystem, as it has no attributes of its own.
- */
-
-struct simple_child {
-	struct config_item item;
-	int storeme;
-};
-
-static inline struct simple_child *to_simple_child(struct config_item *item)
-{
-	return item ? container_of(item, struct simple_child, item) : NULL;
-}
-
-static struct configfs_attribute simple_child_attr_storeme = {
-	.ca_owner = THIS_MODULE,
-	.ca_name = "storeme",
-	.ca_mode = S_IRUGO | S_IWUSR,
-};
-
-static struct configfs_attribute *simple_child_attrs[] = {
-	&simple_child_attr_storeme,
-	NULL,
-};
-
-static ssize_t simple_child_attr_show(struct config_item *item,
-				      struct configfs_attribute *attr,
-				      char *page)
-{
-	ssize_t count;
-	struct simple_child *simple_child = to_simple_child(item);
-
-	count = sprintf(page, "%d\n", simple_child->storeme);
-
-	return count;
-}
-
-static ssize_t simple_child_attr_store(struct config_item *item,
-				       struct configfs_attribute *attr,
-				       const char *page, size_t count)
-{
-	struct simple_child *simple_child = to_simple_child(item);
-	unsigned long tmp;
-	char *p = (char *) page;
-
-	tmp = simple_strtoul(p, &p, 10);
-	if (!p || (*p && (*p != '\n')))
-		return -EINVAL;
-
-	if (tmp > INT_MAX)
-		return -ERANGE;
-
-	simple_child->storeme = tmp;
-
-	return count;
-}
-
-static void simple_child_release(struct config_item *item)
-{
-	kfree(to_simple_child(item));
-}
-
-static struct configfs_item_operations simple_child_item_ops = {
-	.release		= simple_child_release,
-	.show_attribute		= simple_child_attr_show,
-	.store_attribute	= simple_child_attr_store,
-};
-
-static struct config_item_type simple_child_type = {
-	.ct_item_ops	= &simple_child_item_ops,
-	.ct_attrs	= simple_child_attrs,
-	.ct_owner	= THIS_MODULE,
-};
-
-
-struct simple_children {
-	struct config_group group;
-};
-
-static inline struct simple_children *to_simple_children(struct config_item *item)
-{
-	return item ? container_of(to_config_group(item), struct simple_children, group) : NULL;
-}
-
-static struct config_item *simple_children_make_item(struct config_group *group, const char *name)
-{
-	struct simple_child *simple_child;
-
-	simple_child = kzalloc(sizeof(struct simple_child), GFP_KERNEL);
-	if (!simple_child)
-		return ERR_PTR(-ENOMEM);
-
-	config_item_init_type_name(&simple_child->item, name,
-				   &simple_child_type);
-
-	simple_child->storeme = 0;
-
-	return &simple_child->item;
-}
-
-static struct configfs_attribute simple_children_attr_description = {
-	.ca_owner = THIS_MODULE,
-	.ca_name = "description",
-	.ca_mode = S_IRUGO,
-};
-
-static struct configfs_attribute *simple_children_attrs[] = {
-	&simple_children_attr_description,
-	NULL,
-};
-
-static ssize_t simple_children_attr_show(struct config_item *item,
-					 struct configfs_attribute *attr,
-					 char *page)
-{
-	return sprintf(page,
-"[02-simple-children]\n"
-"\n"
-"This subsystem allows the creation of child config_items.  These\n"
-"items have only one attribute that is readable and writeable.\n");
-}
-
-static void simple_children_release(struct config_item *item)
-{
-	kfree(to_simple_children(item));
-}
-
-static struct configfs_item_operations simple_children_item_ops = {
-	.release	= simple_children_release,
-	.show_attribute	= simple_children_attr_show,
-};
-
-/*
- * Note that, since no extra work is required on ->drop_item(),
- * no ->drop_item() is provided.
- */
-static struct configfs_group_operations simple_children_group_ops = {
-	.make_item	= simple_children_make_item,
-};
-
-static struct config_item_type simple_children_type = {
-	.ct_item_ops	= &simple_children_item_ops,
-	.ct_group_ops	= &simple_children_group_ops,
-	.ct_attrs	= simple_children_attrs,
-	.ct_owner	= THIS_MODULE,
-};
-
-static struct configfs_subsystem simple_children_subsys = {
-	.su_group = {
-		.cg_item = {
-			.ci_namebuf = "02-simple-children",
-			.ci_type = &simple_children_type,
-		},
-	},
-};
-
-
-/* ----------------------------------------------------------------- */
-
-/*
- * 03-group-children
- *
- * This example reuses the simple_children group from above.  However,
- * the simple_children group is not the subsystem itself, it is a
- * child of the subsystem.  Creation of a group in the subsystem creates
- * a new simple_children group.  That group can then have simple_child
- * children of its own.
- */
-
-static struct config_group *group_children_make_group(struct config_group *group, const char *name)
-{
-	struct simple_children *simple_children;
-
-	simple_children = kzalloc(sizeof(struct simple_children),
-				  GFP_KERNEL);
-	if (!simple_children)
-		return ERR_PTR(-ENOMEM);
-
-	config_group_init_type_name(&simple_children->group, name,
-				    &simple_children_type);
-
-	return &simple_children->group;
-}
-
-static struct configfs_attribute group_children_attr_description = {
-	.ca_owner = THIS_MODULE,
-	.ca_name = "description",
-	.ca_mode = S_IRUGO,
-};
-
-static struct configfs_attribute *group_children_attrs[] = {
-	&group_children_attr_description,
-	NULL,
-};
-
-static ssize_t group_children_attr_show(struct config_item *item,
-					struct configfs_attribute *attr,
-					char *page)
-{
-	return sprintf(page,
-"[03-group-children]\n"
-"\n"
-"This subsystem allows the creation of child config_groups.  These\n"
-"groups are like the subsystem simple-children.\n");
-}
-
-static struct configfs_item_operations group_children_item_ops = {
-	.show_attribute	= group_children_attr_show,
-};
-
-/*
- * Note that, since no extra work is required on ->drop_item(),
- * no ->drop_item() is provided.
- */
-static struct configfs_group_operations group_children_group_ops = {
-	.make_group	= group_children_make_group,
-};
-
-static struct config_item_type group_children_type = {
-	.ct_item_ops	= &group_children_item_ops,
-	.ct_group_ops	= &group_children_group_ops,
-	.ct_attrs	= group_children_attrs,
-	.ct_owner	= THIS_MODULE,
-};
-
-static struct configfs_subsystem group_children_subsys = {
-	.su_group = {
-		.cg_item = {
-			.ci_namebuf = "03-group-children",
-			.ci_type = &group_children_type,
-		},
-	},
-};
-
-/* ----------------------------------------------------------------- */
-
-/*
- * We're now done with our subsystem definitions.
- * For convenience in this module, here's a list of them all.  It
- * allows the init function to easily register them.  Most modules
- * will only have one subsystem, and will only call register_subsystem
- * on it directly.
- */
-static struct configfs_subsystem *example_subsys[] = {
-	&childless_subsys.subsys,
-	&simple_children_subsys,
-	&group_children_subsys,
-	NULL,
-};
-
-static int __init configfs_example_init(void)
-{
-	int ret;
-	int i;
-	struct configfs_subsystem *subsys;
-
-	for (i = 0; example_subsys[i]; i++) {
-		subsys = example_subsys[i];
-
-		config_group_init(&subsys->su_group);
-		mutex_init(&subsys->su_mutex);
-		ret = configfs_register_subsystem(subsys);
-		if (ret) {
-			printk(KERN_ERR "Error %d while registering subsystem %s\n",
-			       ret,
-			       subsys->su_group.cg_item.ci_namebuf);
-			goto out_unregister;
-		}
-	}
-
-	return 0;
-
-out_unregister:
-	for (i--; i >= 0; i--)
-		configfs_unregister_subsystem(example_subsys[i]);
-
-	return ret;
-}
-
-static void __exit configfs_example_exit(void)
-{
-	int i;
-
-	for (i = 0; example_subsys[i]; i++)
-		configfs_unregister_subsystem(example_subsys[i]);
-}
-
-module_init(configfs_example_init);
-module_exit(configfs_example_exit);
-MODULE_LICENSE("GPL");
diff --git a/Documentation/filesystems/configfs/configfs_example_macros.c b/Documentation/filesystems/configfs/configfs_example_macros.c
deleted file mode 100644
index 327dfbc..0000000
--- a/Documentation/filesystems/configfs/configfs_example_macros.c
+++ /dev/null
@@ -1,446 +0,0 @@
-/*
- * vim: noexpandtab ts=8 sts=0 sw=8:
- *
- * configfs_example_macros.c - This file is a demonstration module
- *      containing a number of configfs subsystems.  It uses the helper
- *      macros defined by configfs.h
- *
- * This program is free software; you can redistribute it and/or
- * modify it under the terms of the GNU General Public
- * License as published by the Free Software Foundation; either
- * version 2 of the License, or (at your option) any later version.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
- * General Public License for more details.
- *
- * You should have received a copy of the GNU General Public
- * License along with this program; if not, write to the
- * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
- * Boston, MA 021110-1307, USA.
- *
- * Based on sysfs:
- * 	sysfs is Copyright (C) 2001, 2002, 2003 Patrick Mochel
- *
- * configfs Copyright (C) 2005 Oracle.  All rights reserved.
- */
-
-#include <linux/init.h>
-#include <linux/module.h>
-#include <linux/slab.h>
-
-#include <linux/configfs.h>
-
-
-
-/*
- * 01-childless
- *
- * This first example is a childless subsystem.  It cannot create
- * any config_items.  It just has attributes.
- *
- * Note that we are enclosing the configfs_subsystem inside a container.
- * This is not necessary if a subsystem has no attributes directly
- * on the subsystem.  See the next example, 02-simple-children, for
- * such a subsystem.
- */
-
-struct childless {
-	struct configfs_subsystem subsys;
-	int showme;
-	int storeme;
-};
-
-static inline struct childless *to_childless(struct config_item *item)
-{
-	return item ? container_of(to_configfs_subsystem(to_config_group(item)), struct childless, subsys) : NULL;
-}
-
-CONFIGFS_ATTR_STRUCT(childless);
-#define CHILDLESS_ATTR(_name, _mode, _show, _store)	\
-struct childless_attribute childless_attr_##_name = __CONFIGFS_ATTR(_name, _mode, _show, _store)
-#define CHILDLESS_ATTR_RO(_name, _show)	\
-struct childless_attribute childless_attr_##_name = __CONFIGFS_ATTR_RO(_name, _show);
-
-static ssize_t childless_showme_read(struct childless *childless,
-				     char *page)
-{
-	ssize_t pos;
-
-	pos = sprintf(page, "%d\n", childless->showme);
-	childless->showme++;
-
-	return pos;
-}
-
-static ssize_t childless_storeme_read(struct childless *childless,
-				      char *page)
-{
-	return sprintf(page, "%d\n", childless->storeme);
-}
-
-static ssize_t childless_storeme_write(struct childless *childless,
-				       const char *page,
-				       size_t count)
-{
-	unsigned long tmp;
-	char *p = (char *) page;
-
-	tmp = simple_strtoul(p, &p, 10);
-	if (!p || (*p && (*p != '\n')))
-		return -EINVAL;
-
-	if (tmp > INT_MAX)
-		return -ERANGE;
-
-	childless->storeme = tmp;
-
-	return count;
-}
-
-static ssize_t childless_description_read(struct childless *childless,
-					  char *page)
-{
-	return sprintf(page,
-"[01-childless]\n"
-"\n"
-"The childless subsystem is the simplest possible subsystem in\n"
-"configfs.  It does not support the creation of child config_items.\n"
-"It only has a few attributes.  In fact, it isn't much different\n"
-"than a directory in /proc.\n");
-}
-
-CHILDLESS_ATTR_RO(showme, childless_showme_read);
-CHILDLESS_ATTR(storeme, S_IRUGO | S_IWUSR, childless_storeme_read,
-	       childless_storeme_write);
-CHILDLESS_ATTR_RO(description, childless_description_read);
-
-static struct configfs_attribute *childless_attrs[] = {
-	&childless_attr_showme.attr,
-	&childless_attr_storeme.attr,
-	&childless_attr_description.attr,
-	NULL,
-};
-
-CONFIGFS_ATTR_OPS(childless);
-static struct configfs_item_operations childless_item_ops = {
-	.show_attribute		= childless_attr_show,
-	.store_attribute	= childless_attr_store,
-};
-
-static struct config_item_type childless_type = {
-	.ct_item_ops	= &childless_item_ops,
-	.ct_attrs	= childless_attrs,
-	.ct_owner	= THIS_MODULE,
-};
-
-static struct childless childless_subsys = {
-	.subsys = {
-		.su_group = {
-			.cg_item = {
-				.ci_namebuf = "01-childless",
-				.ci_type = &childless_type,
-			},
-		},
-	},
-};
-
-
-/* ----------------------------------------------------------------- */
-
-/*
- * 02-simple-children
- *
- * This example merely has a simple one-attribute child.  Note that
- * there is no extra attribute structure, as the child's attribute is
- * known from the get-go.  Also, there is no container for the
- * subsystem, as it has no attributes of its own.
- */
-
-struct simple_child {
-	struct config_item item;
-	int storeme;
-};
-
-static inline struct simple_child *to_simple_child(struct config_item *item)
-{
-	return item ? container_of(item, struct simple_child, item) : NULL;
-}
-
-static struct configfs_attribute simple_child_attr_storeme = {
-	.ca_owner = THIS_MODULE,
-	.ca_name = "storeme",
-	.ca_mode = S_IRUGO | S_IWUSR,
-};
-
-static struct configfs_attribute *simple_child_attrs[] = {
-	&simple_child_attr_storeme,
-	NULL,
-};
-
-static ssize_t simple_child_attr_show(struct config_item *item,
-				      struct configfs_attribute *attr,
-				      char *page)
-{
-	ssize_t count;
-	struct simple_child *simple_child = to_simple_child(item);
-
-	count = sprintf(page, "%d\n", simple_child->storeme);
-
-	return count;
-}
-
-static ssize_t simple_child_attr_store(struct config_item *item,
-				       struct configfs_attribute *attr,
-				       const char *page, size_t count)
-{
-	struct simple_child *simple_child = to_simple_child(item);
-	unsigned long tmp;
-	char *p = (char *) page;
-
-	tmp = simple_strtoul(p, &p, 10);
-	if (!p || (*p && (*p != '\n')))
-		return -EINVAL;
-
-	if (tmp > INT_MAX)
-		return -ERANGE;
-
-	simple_child->storeme = tmp;
-
-	return count;
-}
-
-static void simple_child_release(struct config_item *item)
-{
-	kfree(to_simple_child(item));
-}
-
-static struct configfs_item_operations simple_child_item_ops = {
-	.release		= simple_child_release,
-	.show_attribute		= simple_child_attr_show,
-	.store_attribute	= simple_child_attr_store,
-};
-
-static struct config_item_type simple_child_type = {
-	.ct_item_ops	= &simple_child_item_ops,
-	.ct_attrs	= simple_child_attrs,
-	.ct_owner	= THIS_MODULE,
-};
-
-
-struct simple_children {
-	struct config_group group;
-};
-
-static inline struct simple_children *to_simple_children(struct config_item *item)
-{
-	return item ? container_of(to_config_group(item), struct simple_children, group) : NULL;
-}
-
-static struct config_item *simple_children_make_item(struct config_group *group, const char *name)
-{
-	struct simple_child *simple_child;
-
-	simple_child = kzalloc(sizeof(struct simple_child), GFP_KERNEL);
-	if (!simple_child)
-		return ERR_PTR(-ENOMEM);
-
-	config_item_init_type_name(&simple_child->item, name,
-				   &simple_child_type);
-
-	simple_child->storeme = 0;
-
-	return &simple_child->item;
-}
-
-static struct configfs_attribute simple_children_attr_description = {
-	.ca_owner = THIS_MODULE,
-	.ca_name = "description",
-	.ca_mode = S_IRUGO,
-};
-
-static struct configfs_attribute *simple_children_attrs[] = {
-	&simple_children_attr_description,
-	NULL,
-};
-
-static ssize_t simple_children_attr_show(struct config_item *item,
-					 struct configfs_attribute *attr,
-					 char *page)
-{
-	return sprintf(page,
-"[02-simple-children]\n"
-"\n"
-"This subsystem allows the creation of child config_items.  These\n"
-"items have only one attribute that is readable and writeable.\n");
-}
-
-static void simple_children_release(struct config_item *item)
-{
-	kfree(to_simple_children(item));
-}
-
-static struct configfs_item_operations simple_children_item_ops = {
-	.release	= simple_children_release,
-	.show_attribute	= simple_children_attr_show,
-};
-
-/*
- * Note that, since no extra work is required on ->drop_item(),
- * no ->drop_item() is provided.
- */
-static struct configfs_group_operations simple_children_group_ops = {
-	.make_item	= simple_children_make_item,
-};
-
-static struct config_item_type simple_children_type = {
-	.ct_item_ops	= &simple_children_item_ops,
-	.ct_group_ops	= &simple_children_group_ops,
-	.ct_attrs	= simple_children_attrs,
-	.ct_owner	= THIS_MODULE,
-};
-
-static struct configfs_subsystem simple_children_subsys = {
-	.su_group = {
-		.cg_item = {
-			.ci_namebuf = "02-simple-children",
-			.ci_type = &simple_children_type,
-		},
-	},
-};
-
-
-/* ----------------------------------------------------------------- */
-
-/*
- * 03-group-children
- *
- * This example reuses the simple_children group from above.  However,
- * the simple_children group is not the subsystem itself, it is a
- * child of the subsystem.  Creation of a group in the subsystem creates
- * a new simple_children group.  That group can then have simple_child
- * children of its own.
- */
-
-static struct config_group *group_children_make_group(struct config_group *group, const char *name)
-{
-	struct simple_children *simple_children;
-
-	simple_children = kzalloc(sizeof(struct simple_children),
-				  GFP_KERNEL);
-	if (!simple_children)
-		return ERR_PTR(-ENOMEM);
-
-	config_group_init_type_name(&simple_children->group, name,
-				    &simple_children_type);
-
-	return &simple_children->group;
-}
-
-static struct configfs_attribute group_children_attr_description = {
-	.ca_owner = THIS_MODULE,
-	.ca_name = "description",
-	.ca_mode = S_IRUGO,
-};
-
-static struct configfs_attribute *group_children_attrs[] = {
-	&group_children_attr_description,
-	NULL,
-};
-
-static ssize_t group_children_attr_show(struct config_item *item,
-					struct configfs_attribute *attr,
-					char *page)
-{
-	return sprintf(page,
-"[03-group-children]\n"
-"\n"
-"This subsystem allows the creation of child config_groups.  These\n"
-"groups are like the subsystem simple-children.\n");
-}
-
-static struct configfs_item_operations group_children_item_ops = {
-	.show_attribute	= group_children_attr_show,
-};
-
-/*
- * Note that, since no extra work is required on ->drop_item(),
- * no ->drop_item() is provided.
- */
-static struct configfs_group_operations group_children_group_ops = {
-	.make_group	= group_children_make_group,
-};
-
-static struct config_item_type group_children_type = {
-	.ct_item_ops	= &group_children_item_ops,
-	.ct_group_ops	= &group_children_group_ops,
-	.ct_attrs	= group_children_attrs,
-	.ct_owner	= THIS_MODULE,
-};
-
-static struct configfs_subsystem group_children_subsys = {
-	.su_group = {
-		.cg_item = {
-			.ci_namebuf = "03-group-children",
-			.ci_type = &group_children_type,
-		},
-	},
-};
-
-/* ----------------------------------------------------------------- */
-
-/*
- * We're now done with our subsystem definitions.
- * For convenience in this module, here's a list of them all.  It
- * allows the init function to easily register them.  Most modules
- * will only have one subsystem, and will only call register_subsystem
- * on it directly.
- */
-static struct configfs_subsystem *example_subsys[] = {
-	&childless_subsys.subsys,
-	&simple_children_subsys,
-	&group_children_subsys,
-	NULL,
-};
-
-static int __init configfs_example_init(void)
-{
-	int ret;
-	int i;
-	struct configfs_subsystem *subsys;
-
-	for (i = 0; example_subsys[i]; i++) {
-		subsys = example_subsys[i];
-
-		config_group_init(&subsys->su_group);
-		mutex_init(&subsys->su_mutex);
-		ret = configfs_register_subsystem(subsys);
-		if (ret) {
-			printk(KERN_ERR "Error %d while registering subsystem %s\n",
-			       ret,
-			       subsys->su_group.cg_item.ci_namebuf);
-			goto out_unregister;
-		}
-	}
-
-	return 0;
-
-out_unregister:
-	for (i--; i >= 0; i--)
-		configfs_unregister_subsystem(example_subsys[i]);
-
-	return ret;
-}
-
-static void __exit configfs_example_exit(void)
-{
-	int i;
-
-	for (i = 0; example_subsys[i]; i++)
-		configfs_unregister_subsystem(example_subsys[i]);
-}
-
-module_init(configfs_example_init);
-module_exit(configfs_example_exit);
-MODULE_LICENSE("GPL");
diff --git a/fs/configfs/file.c b/fs/configfs/file.c
index 106ca58..d39099e 100644
--- a/fs/configfs/file.c
+++ b/fs/configfs/file.c
@@ -65,7 +65,6 @@ static int fill_read_buffer(struct dentry * dentry, struct configfs_buffer * buf
 {
 	struct configfs_attribute * attr = to_attr(dentry);
 	struct config_item * item = to_item(dentry->d_parent);
-	struct configfs_item_operations * ops = buffer->ops;
 	int ret = 0;
 	ssize_t count;
 
@@ -74,10 +73,7 @@ static int fill_read_buffer(struct dentry * dentry, struct configfs_buffer * buf
 	if (!buffer->page)
 		return -ENOMEM;
 
-	if (ops->show_attribute)
-		count = ops->show_attribute(item, attr, buffer->page);
-	else
-		count = attr->show(item, buffer->page);
+	count = attr->show(item, buffer->page);
 
 	buffer->needs_read_fill = 0;
 	BUG_ON(count > (ssize_t)SIMPLE_ATTR_SIZE);
@@ -175,10 +171,7 @@ flush_write_buffer(struct dentry * dentry, struct configfs_buffer * buffer, size
 {
 	struct configfs_attribute * attr = to_attr(dentry);
 	struct config_item * item = to_item(dentry->d_parent);
-	struct configfs_item_operations * ops = buffer->ops;
 
-	if (ops->store_attribute)
-		return ops->store_attribute(item, attr, buffer->page, count);
 	return attr->store(item, buffer->page, count);
 }
 
@@ -243,8 +236,7 @@ static int check_perm(struct inode * inode, struct file * file)
 	 * and we must have a store method.
 	 */
 	if (file->f_mode & FMODE_WRITE) {
-		if (!(inode->i_mode & S_IWUGO) ||
-		    (!ops->store_attribute && !attr->store))
+		if (!(inode->i_mode & S_IWUGO) || !attr->store)
 			goto Eaccess;
 
 	}
@@ -254,8 +246,7 @@ static int check_perm(struct inode * inode, struct file * file)
 	 * must be a show method for it.
 	 */
 	if (file->f_mode & FMODE_READ) {
-		if (!(inode->i_mode & S_IRUGO) ||
-		    (!ops->show_attribute && !attr->show))
+		if (!(inode->i_mode & S_IRUGO) || !attr->show)
 			goto Eaccess;
 	}
 
diff --git a/include/linux/configfs.h b/include/linux/configfs.h
index 85e9956..a8a335b 100644
--- a/include/linux/configfs.h
+++ b/include/linux/configfs.h
@@ -155,86 +155,6 @@ static struct configfs_attribute _pfx##attr_##_name = {	\
 }
 
 /*
- * Users often need to create attribute structures for their configurable
- * attributes, containing a configfs_attribute member and function pointers
- * for the show() and store() operations on that attribute. If they don't
- * need anything else on the extended attribute structure, they can use
- * this macro to define it  The argument _item is the name of the
- * config_item structure.
- */
-#define CONFIGFS_ATTR_STRUCT(_item)					\
-struct _item##_attribute {						\
-	struct configfs_attribute attr;					\
-	ssize_t (*show)(struct _item *, char *);			\
-	ssize_t (*store)(struct _item *, const char *, size_t);		\
-}
-
-/*
- * With the extended attribute structure, users can use this macro
- * (similar to sysfs' __ATTR) to make defining attributes easier.
- * An example:
- * #define MYITEM_ATTR(_name, _mode, _show, _store)	\
- * struct myitem_attribute childless_attr_##_name =	\
- *         __CONFIGFS_ATTR(_name, _mode, _show, _store)
- */
-#define __CONFIGFS_ATTR(_name, _mode, _show, _store)			\
-{									\
-	.attr	= {							\
-			.ca_name = __stringify(_name),			\
-			.ca_mode = _mode,				\
-			.ca_owner = THIS_MODULE,			\
-	},								\
-	.show	= _show,						\
-	.store	= _store,						\
-}
-/* Here is a readonly version, only requiring a show() operation */
-#define __CONFIGFS_ATTR_RO(_name, _show)				\
-{									\
-	.attr	= {							\
-			.ca_name = __stringify(_name),			\
-			.ca_mode = 0444,				\
-			.ca_owner = THIS_MODULE,			\
-	},								\
-	.show	= _show,						\
-}
-
-/*
- * With these extended attributes, the simple show_attribute() and
- * store_attribute() operations need to call the show() and store() of the
- * attributes.  This is a common pattern, so we provide a macro to define
- * them.  The argument _item is the name of the config_item structure.
- * This macro expects the attributes to be named "struct <name>_attribute"
- * and the function to_<name>() to exist;
- */
-#define CONFIGFS_ATTR_OPS(_item)					\
-static ssize_t _item##_attr_show(struct config_item *item,		\
-				 struct configfs_attribute *attr,	\
-				 char *page)				\
-{									\
-	struct _item *_item = to_##_item(item);				\
-	struct _item##_attribute *_item##_attr =			\
-		container_of(attr, struct _item##_attribute, attr);	\
-	ssize_t ret = 0;						\
-									\
-	if (_item##_attr->show)						\
-		ret = _item##_attr->show(_item, page);			\
-	return ret;							\
-}									\
-static ssize_t _item##_attr_store(struct config_item *item,		\
-				  struct configfs_attribute *attr,	\
-				  const char *page, size_t count)	\
-{									\
-	struct _item *_item = to_##_item(item);				\
-	struct _item##_attribute *_item##_attr =			\
-		container_of(attr, struct _item##_attribute, attr);	\
-	ssize_t ret = -EINVAL;						\
-									\
-	if (_item##_attr->store)					\
-		ret = _item##_attr->store(_item, page, count);		\
-	return ret;							\
-}
-
-/*
  * If allow_link() exists, the item can symlink(2) out to other
  * items.  If the item is a group, it may support mkdir(2).
  * Groups supply one of make_group() and make_item().  If the
@@ -250,8 +170,6 @@ static ssize_t _item##_attr_store(struct config_item *item,		\
  */
 struct configfs_item_operations {
 	void (*release)(struct config_item *);
-	ssize_t	(*show_attribute)(struct config_item *, struct configfs_attribute *,char *);
-	ssize_t	(*store_attribute)(struct config_item *,struct configfs_attribute *,const char *, size_t);
 	int (*allow_link)(struct config_item *src, struct config_item *target);
 	int (*drop_link)(struct config_item *src, struct config_item *target);
 };
diff --git a/samples/Makefile b/samples/Makefile
index f00257b..48001d7 100644
--- a/samples/Makefile
+++ b/samples/Makefile
@@ -1,4 +1,5 @@
 # Makefile for Linux samples code
 
 obj-$(CONFIG_SAMPLES)	+= kobject/ kprobes/ trace_events/ livepatch/ \
-			   hw_breakpoint/ kfifo/ kdb/ hidraw/ rpmsg/ seccomp/
+			   hw_breakpoint/ kfifo/ kdb/ hidraw/ rpmsg/ seccomp/ \
+			   configfs/
diff --git a/samples/configfs/Makefile b/samples/configfs/Makefile
new file mode 100644
index 0000000..4d3c8b6
--- /dev/null
+++ b/samples/configfs/Makefile
@@ -0,0 +1,2 @@
+
+obj-m += configfs_sample.o
diff --git a/samples/configfs/configfs_sample.c b/samples/configfs/configfs_sample.c
new file mode 100644
index 0000000..1ea3311
--- /dev/null
+++ b/samples/configfs/configfs_sample.c
@@ -0,0 +1,404 @@
+/*
+ * vim: noexpandtab ts=8 sts=0 sw=8:
+ *
+ * configfs_example_macros.c - This file is a demonstration module
+ *      containing a number of configfs subsystems.  It uses the helper
+ *      macros defined by configfs.h
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public
+ * License along with this program; if not, write to the
+ * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ * Boston, MA 021110-1307, USA.
+ *
+ * Based on sysfs:
+ * 	sysfs is Copyright (C) 2001, 2002, 2003 Patrick Mochel
+ *
+ * configfs Copyright (C) 2005 Oracle.  All rights reserved.
+ */
+
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+
+#include <linux/configfs.h>
+
+
+
+/*
+ * 01-childless
+ *
+ * This first example is a childless subsystem.  It cannot create
+ * any config_items.  It just has attributes.
+ *
+ * Note that we are enclosing the configfs_subsystem inside a container.
+ * This is not necessary if a subsystem has no attributes directly
+ * on the subsystem.  See the next example, 02-simple-children, for
+ * such a subsystem.
+ */
+
+struct childless {
+	struct configfs_subsystem subsys;
+	int showme;
+	int storeme;
+};
+
+static inline struct childless *to_childless(struct config_item *item)
+{
+	return item ? container_of(to_configfs_subsystem(to_config_group(item)),
+			struct childless, subsys) : NULL;
+}
+
+static ssize_t childless_showme_show(struct config_item *item, char *page)
+{
+	struct childless *childless = to_childless(item);
+	ssize_t pos;
+
+	pos = sprintf(page, "%d\n", childless->showme);
+	childless->showme++;
+
+	return pos;
+}
+
+static ssize_t childless_storeme_show(struct config_item *item, char *page)
+{
+	return sprintf(page, "%d\n", to_childless(item)->storeme);
+}
+
+static ssize_t childless_storeme_store(struct config_item *item,
+		const char *page, size_t count)
+{
+	struct childless *childless = to_childless(item);
+	unsigned long tmp;
+	char *p = (char *) page;
+
+	tmp = simple_strtoul(p, &p, 10);
+	if (!p || (*p && (*p != '\n')))
+		return -EINVAL;
+
+	if (tmp > INT_MAX)
+		return -ERANGE;
+
+	childless->storeme = tmp;
+
+	return count;
+}
+
+static ssize_t childless_description_show(struct config_item *item, char *page)
+{
+	return sprintf(page,
+"[01-childless]\n"
+"\n"
+"The childless subsystem is the simplest possible subsystem in\n"
+"configfs.  It does not support the creation of child config_items.\n"
+"It only has a few attributes.  In fact, it isn't much different\n"
+"than a directory in /proc.\n");
+}
+
+CONFIGFS_ATTR_RO(childless_, showme);
+CONFIGFS_ATTR(childless_, storeme);
+CONFIGFS_ATTR_RO(childless_, description);
+
+static struct configfs_attribute *childless_attrs[] = {
+	&childless_attr_showme,
+	&childless_attr_storeme,
+	&childless_attr_description,
+	NULL,
+};
+
+static struct config_item_type childless_type = {
+	.ct_attrs	= childless_attrs,
+	.ct_owner	= THIS_MODULE,
+};
+
+static struct childless childless_subsys = {
+	.subsys = {
+		.su_group = {
+			.cg_item = {
+				.ci_namebuf = "01-childless",
+				.ci_type = &childless_type,
+			},
+		},
+	},
+};
+
+
+/* ----------------------------------------------------------------- */
+
+/*
+ * 02-simple-children
+ *
+ * This example merely has a simple one-attribute child.  Note that
+ * there is no extra attribute structure, as the child's attribute is
+ * known from the get-go.  Also, there is no container for the
+ * subsystem, as it has no attributes of its own.
+ */
+
+struct simple_child {
+	struct config_item item;
+	int storeme;
+};
+
+static inline struct simple_child *to_simple_child(struct config_item *item)
+{
+	return item ? container_of(item, struct simple_child, item) : NULL;
+}
+
+static ssize_t simple_child_storeme_show(struct config_item *item, char *page)
+{
+	return sprintf(page, "%d\n", to_simple_child(item)->storeme);
+}
+
+static ssize_t simple_child_storeme_store(struct config_item *item,
+		const char *page, size_t count)
+{
+	struct simple_child *simple_child = to_simple_child(item);
+	unsigned long tmp;
+	char *p = (char *) page;
+
+	tmp = simple_strtoul(p, &p, 10);
+	if (!p || (*p && (*p != '\n')))
+		return -EINVAL;
+
+	if (tmp > INT_MAX)
+		return -ERANGE;
+
+	simple_child->storeme = tmp;
+
+	return count;
+}
+
+CONFIGFS_ATTR(simple_child_, storeme);
+
+static struct configfs_attribute *simple_child_attrs[] = {
+	&simple_child_attr_storeme,
+	NULL,
+};
+
+static void simple_child_release(struct config_item *item)
+{
+	kfree(to_simple_child(item));
+}
+
+static struct configfs_item_operations simple_child_item_ops = {
+	.release		= simple_child_release,
+};
+
+static struct config_item_type simple_child_type = {
+	.ct_item_ops	= &simple_child_item_ops,
+	.ct_attrs	= simple_child_attrs,
+	.ct_owner	= THIS_MODULE,
+};
+
+
+struct simple_children {
+	struct config_group group;
+};
+
+static inline struct simple_children *to_simple_children(struct config_item *item)
+{
+	return item ? container_of(to_config_group(item),
+			struct simple_children, group) : NULL;
+}
+
+static struct config_item *simple_children_make_item(struct config_group *group,
+		const char *name)
+{
+	struct simple_child *simple_child;
+
+	simple_child = kzalloc(sizeof(struct simple_child), GFP_KERNEL);
+	if (!simple_child)
+		return ERR_PTR(-ENOMEM);
+
+	config_item_init_type_name(&simple_child->item, name,
+				   &simple_child_type);
+
+	simple_child->storeme = 0;
+
+	return &simple_child->item;
+}
+
+static ssize_t simple_children_description_show(struct config_item *item,
+		char *page)
+{
+	return sprintf(page,
+"[02-simple-children]\n"
+"\n"
+"This subsystem allows the creation of child config_items.  These\n"
+"items have only one attribute that is readable and writeable.\n");
+}
+
+CONFIGFS_ATTR_RO(simple_children_, description);
+
+static struct configfs_attribute *simple_children_attrs[] = {
+	&simple_children_attr_description,
+	NULL,
+};
+
+static void simple_children_release(struct config_item *item)
+{
+	kfree(to_simple_children(item));
+}
+
+static struct configfs_item_operations simple_children_item_ops = {
+	.release	= simple_children_release,
+};
+
+/*
+ * Note that, since no extra work is required on ->drop_item(),
+ * no ->drop_item() is provided.
+ */
+static struct configfs_group_operations simple_children_group_ops = {
+	.make_item	= simple_children_make_item,
+};
+
+static struct config_item_type simple_children_type = {
+	.ct_item_ops	= &simple_children_item_ops,
+	.ct_group_ops	= &simple_children_group_ops,
+	.ct_attrs	= simple_children_attrs,
+	.ct_owner	= THIS_MODULE,
+};
+
+static struct configfs_subsystem simple_children_subsys = {
+	.su_group = {
+		.cg_item = {
+			.ci_namebuf = "02-simple-children",
+			.ci_type = &simple_children_type,
+		},
+	},
+};
+
+
+/* ----------------------------------------------------------------- */
+
+/*
+ * 03-group-children
+ *
+ * This example reuses the simple_children group from above.  However,
+ * the simple_children group is not the subsystem itself, it is a
+ * child of the subsystem.  Creation of a group in the subsystem creates
+ * a new simple_children group.  That group can then have simple_child
+ * children of its own.
+ */
+
+static struct config_group *group_children_make_group(
+		struct config_group *group, const char *name)
+{
+	struct simple_children *simple_children;
+
+	simple_children = kzalloc(sizeof(struct simple_children),
+				  GFP_KERNEL);
+	if (!simple_children)
+		return ERR_PTR(-ENOMEM);
+
+	config_group_init_type_name(&simple_children->group, name,
+				    &simple_children_type);
+
+	return &simple_children->group;
+}
+
+static ssize_t group_children_description_show(struct config_item *item,
+		char *page)
+{
+	return sprintf(page,
+"[03-group-children]\n"
+"\n"
+"This subsystem allows the creation of child config_groups.  These\n"
+"groups are like the subsystem simple-children.\n");
+}
+
+CONFIGFS_ATTR_RO(group_children_, description);
+
+static struct configfs_attribute *group_children_attrs[] = {
+	&group_children_attr_description,
+	NULL,
+};
+
+/*
+ * Note that, since no extra work is required on ->drop_item(),
+ * no ->drop_item() is provided.
+ */
+static struct configfs_group_operations group_children_group_ops = {
+	.make_group	= group_children_make_group,
+};
+
+static struct config_item_type group_children_type = {
+	.ct_group_ops	= &group_children_group_ops,
+	.ct_attrs	= group_children_attrs,
+	.ct_owner	= THIS_MODULE,
+};
+
+static struct configfs_subsystem group_children_subsys = {
+	.su_group = {
+		.cg_item = {
+			.ci_namebuf = "03-group-children",
+			.ci_type = &group_children_type,
+		},
+	},
+};
+
+/* ----------------------------------------------------------------- */
+
+/*
+ * We're now done with our subsystem definitions.
+ * For convenience in this module, here's a list of them all.  It
+ * allows the init function to easily register them.  Most modules
+ * will only have one subsystem, and will only call register_subsystem
+ * on it directly.
+ */
+static struct configfs_subsystem *example_subsys[] = {
+	&childless_subsys.subsys,
+	&simple_children_subsys,
+	&group_children_subsys,
+	NULL,
+};
+
+static int __init configfs_example_init(void)
+{
+	int ret;
+	int i;
+	struct configfs_subsystem *subsys;
+
+	for (i = 0; example_subsys[i]; i++) {
+		subsys = example_subsys[i];
+
+		config_group_init(&subsys->su_group);
+		mutex_init(&subsys->su_mutex);
+		ret = configfs_register_subsystem(subsys);
+		if (ret) {
+			printk(KERN_ERR "Error %d while registering subsystem %s\n",
+			       ret,
+			       subsys->su_group.cg_item.ci_namebuf);
+			goto out_unregister;
+		}
+	}
+
+	return 0;
+
+out_unregister:
+	for (i--; i >= 0; i--)
+		configfs_unregister_subsystem(example_subsys[i]);
+
+	return ret;
+}
+
+static void __exit configfs_example_exit(void)
+{
+	int i;
+
+	for (i = 0; example_subsys[i]; i++)
+		configfs_unregister_subsystem(example_subsys[i]);
+}
+
+module_init(configfs_example_init);
+module_exit(configfs_example_exit);
+MODULE_LICENSE("GPL");
-- 
1.9.1
