sysfs: Document struct attribute_group

Document variables defined in struct attribute_group to ensure
correct usage.
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Vivien Didelot <vivien.didelot@savoirfairelinux.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

include/linux/sysfs.h

@@ -57,6 +57,21 @@ do {							\
 #define sysfs_attr_init(attr) do {} while (0)
 #endif
 
+/**
+ * struct attribute_group - data structure used to declare an attribute group.
+ * @name:	Optional: Attribute group name
+ *		If specified, the attribute group will be created in
+ *		a new subdirectory with this name.
+ * @is_visible:	Optional: Function to return permissions associated with an
+ *		attribute of the group. Will be called repeatedly for each
+ *		attribute in the group. Only read/write permissions as well as
+ *		SYSFS_PREALLOC are accepted. Must return 0 if an attribute is
+ *		not visible. The returned value will replace static permissions
+ *		defined in struct attribute or struct bin_attribute.
+ * @attrs:	Pointer to NULL terminated list of attributes.
+ * @bin_attrs:	Pointer to NULL terminated list of binary attributes.
+ *		Either attrs or bin_attrs or both must be provided.
+ */
 struct attribute_group {
 	const char		*name;
 	umode_t			(*is_visible)(struct kobject *,