1 files changed, 36 insertions, 12 deletions

diff --git a/procfs_dir.h b/procfs_dir.h
index 4eb934e0..12e99d2a 100644
--- a/procfs_dir.h
+++ b/procfs_dir.h
@@ -1,20 +1,44 @@
+/* This module provides an abstraction layer for implementing simple
+   directories with (mostly) static contents.  The user defines the
+   contents of the directory by providing a table of entries and various
+   optional callback functions.  */
 
-/* Each entry associates a name with a callback function for creating new
-   nodes corresponding to that entry.  */
+/* These operations define how a given entry will behave.  Either can be
+   omitted, both from the entry-specific operations and from the
+   directory-wide defaults.  */
+struct procfs_dir_entry_ops
+{
+  /* Called when this entry is looked up to create a corresponding node.  */
+  struct node *(*make_node)(void *dir_hook, const void *entry_hook);
+  /* If this is provided and returns 0, this entry will be hidden.  */
+  int (*exists)(void *dir_hook, const void *entry_hook);
+};
+
+/* Describes an individual directory entry, associating a NAME with
+ * arbitrary HOOK data and node-specific OPS.  */
 struct procfs_dir_entry
 {
   const char *name;
-  struct node *(*make_node)(void *dir_hook, void *entry_hook);
-  void *hook;
+  const void *hook;
+  struct procfs_dir_entry_ops ops;
+};
+
+/* Describes a complete directory. ENTRIES is a table terminated by a
+   null NAME field. ENTRY_OPS provides default operations for the
+   entries which don't specify them.  The optional CLEANUP function
+   should release all the resources associated with the directory hook.  */
+struct procfs_dir_ops
+{
+  const struct procfs_dir_entry *entries;
+  void (*cleanup)(void *dir_hook);
+  struct procfs_dir_entry_ops entry_ops;
 };
 
-/* A simple directory is built from a table of entries.  The table is
-   terminated by a null NAME pointer.  The DIR_HOOK is passed the
-   MAKE_NODE callback function of looked up procfs_dir_entries, and to
-   the provided CLEANUP function when the directory is destroyed.
-   Returns the new directory node.  If not enough memory can be
-   allocated, CLEANUP is invoked immediately and NULL is returned.  */
+/* Create and return a new node for the directory described in OPS.
+   The DIR_HOOK is passed the MAKE_NODE callback function of looked up
+   entries, as well as to the CLEANUP callback when the node is
+   destroyed.  If not enough memory can be allocated, OPS->CLEANUP is
+   invoked immediately and NULL is returned.  */
 struct node *
-procfs_dir_make_node (const struct procfs_dir_entry *entries,
-		      void *dir_hook, void (*cleanup) (void *dir_hook));
+procfs_dir_make_node (const struct procfs_dir_ops *ops, void *dir_hook);