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configfs_example.c

/*
 * vim: noexpandtab ts=8 sts=0 sw=8:
 *
 * configfs_example.c - This file is a demonstration module containing
 *      a number of configfs subsystems.
 *
 * 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 || (*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");
}

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 NULL;


      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 NULL;


      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 >= 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");

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