[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>
diff --git a/Documentation/filesystems/configfs/configfs.txt b/Documentation/filesystems/configfs/configfs.txt
index 44c97e6..fabcb0e 100644
--- a/Documentation/filesystems/configfs/configfs.txt
+++ b/Documentation/filesystems/configfs/configfs.txt
@@ -311,9 +311,20 @@
[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
similarity index 96%
rename from Documentation/filesystems/configfs/configfs_example.c
rename to Documentation/filesystems/configfs/configfs_example_explicit.c
index 03964879..d428cc9 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 @@
if (!simple_child)
return ERR_PTR(-ENOMEM);
-
config_item_init_type_name(&simple_child->item, name,
&simple_child_type);
@@ -302,8 +303,8 @@
};
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 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 @@
if (!simple_children)
return ERR_PTR(-ENOMEM);
-
config_group_init_type_name(&simple_children->group, name,
&simple_children_type);
@@ -387,8 +387,8 @@
};
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.c b/Documentation/filesystems/configfs/configfs_example_macros.c
similarity index 84%
copy from Documentation/filesystems/configfs/configfs_example.c
copy to Documentation/filesystems/configfs/configfs_example_macros.c
index 03964879..d8e30a0 100644
--- a/Documentation/filesystems/configfs/configfs_example.c
+++ b/Documentation/filesystems/configfs/configfs_example_macros.c
@@ -1,8 +1,9 @@
/*
* 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_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
@@ -51,17 +52,17 @@
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;
}
+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)
{
@@ -110,19 +111,10 @@
"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,
-};
+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,
@@ -131,34 +123,7 @@
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;
-}
-
+CONFIGFS_ATTR_OPS(childless);
static struct configfs_item_operations childless_item_ops = {
.show_attribute = childless_attr_show,
.store_attribute = childless_attr_store,
@@ -281,7 +246,6 @@
if (!simple_child)
return ERR_PTR(-ENOMEM);
-
config_item_init_type_name(&simple_child->item, name,
&simple_child_type);
@@ -302,8 +266,8 @@
};
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 +282,7 @@
}
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 +332,6 @@
if (!simple_children)
return ERR_PTR(-ENOMEM);
-
config_group_init_type_name(&simple_children->group, name,
&simple_children_type);
@@ -387,8 +350,8 @@
};
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/include/linux/configfs.h b/include/linux/configfs.h
index 0a5491b..7f62777 100644
--- a/include/linux/configfs.h
+++ b/include/linux/configfs.h
@@ -130,8 +130,25 @@
/*
* 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. They can use
- * this macro (similar to sysfs' __ATTR) to make defining attributes easier.
+ * 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) \
{ \
@@ -143,6 +160,52 @@
.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
