configfs_example_explicit.c

Go to the documentation of this file.

/*
 * 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");