[PATCH] configfs: Convenience macros for attribute definition.

Sysfs has the _ATTR() and _ATTR_RO() macros to make defining extended
form attributes easier.  configfs should have something similiar.

- _CONFIGFS_ATTR() and _CONFIGFS_ATTR_RO() are the counterparts to the
  sysfs macros.
- CONFIGFS_ATTR_STRUCT() creates the extended form attribute structure.
- CONFIGFS_ATTR_OPS() defines the show_attribute()/store_attribute()
  operations that call the show()/store() operations of the extended
  form configfs_attributes.

Signed-off-by: Joel Becker <joel.becker@oracle.com>
Signed-off-by: Mark Fasheh <mfasheh@suse.com>

3 files changed, 471 insertions, 12 deletions

diff --git a/Documentation/filesystems/configfs/configfs.txt b/Documentation/filesystems/configfs/configfs.txt
index 44c97e6accb..fabcb0e00f2 100644
--- a/Documentation/filesystems/configfs/configfs.txt
+++ b/Documentation/filesystems/configfs/configfs.txt
@@ -311,9 +311,20 @@ 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.c  It
-shows a trivial object displaying and storing an attribute, and a simple
-group creating and destroying these 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.
 
 [Hierarchy Navigation and the Subsystem Mutex]
 
diff --git a/Documentation/filesystems/configfs/configfs_example.c b/Documentation/filesystems/configfs/configfs_example_explicit.c
index 03964879170..d428cc9f07f 100644
--- a/Documentation/filesystems/configfs/configfs_example.c
+++ b/Documentation/filesystems/configfs/configfs_example_explicit.c
@@ -1,8 +1,10 @@
 /*
  * vim: noexpandtab ts=8 sts=0 sw=8:
  *
- * configfs_example.c - This file is a demonstration module containing
- *      a number of configfs subsystems.
+ * 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
@@ -281,7 +283,6 @@ static struct config_item *simple_children_make_item(struct config_group *group,
         if (!simple_child)
                 return ERR_PTR(-ENOMEM);
 
-
         config_item_init_type_name(&simple_child->item, name,
                                    &simple_child_type);
 
@@ -302,8 +303,8 @@ static struct configfs_attribute *simple_children_attrs[] = {
 };
 
 static ssize_t simple_children_attr_show(struct config_item *item,
-                                         struct configfs_attribute *attr,
-                                         char *page)
+                                         struct configfs_attribute *attr,
+                                         char *page)
 {
         return sprintf(page,
 "[02-simple-children]\n"
@@ -318,7 +319,7 @@ static void simple_children_release(struct config_item *item)
 }
 
 static struct configfs_item_operations simple_children_item_ops = {
-        .release        = simple_children_release,
+        .release        = simple_children_release,
         .show_attribute = simple_children_attr_show,
 };
 
@@ -368,7 +369,6 @@ static struct config_group *group_children_make_group(struct config_group *group
         if (!simple_children)
                 return ERR_PTR(-ENOMEM);
 
-
         config_group_init_type_name(&simple_children->group, name,
                                     &simple_children_type);
 
@@ -387,8 +387,8 @@ static struct configfs_attribute *group_children_attrs[] = {
 };
 
 static ssize_t group_children_attr_show(struct config_item *item,
-                                        struct configfs_attribute *attr,
-                                        char *page)
+                                        struct configfs_attribute *attr,
+                                        char *page)
 {
         return sprintf(page,
 "[03-group-children]\n"
diff --git a/Documentation/filesystems/configfs/configfs_example_macros.c b/Documentation/filesystems/configfs/configfs_example_macros.c
new file mode 100644
index 00000000000..d8e30a0378a
--- /dev/null
+++ b/Documentation/filesystems/configfs/configfs_example_macros.c
@@ -0,0 +1,448 @@
+/*
+ * 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 >= 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");