Documentation / filesystems / configfs / configfs_example_explicit.c

Based on kernel version 4.3. Page generated on 2015-11-02 12:49 EST.

	/*
	 * 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");

• [ configfs ]
• configfs.txt
• configfs_example_explicit.c
• configfs_example_macros.c
• Makefile
•  

---