diff --git a/Documentation/doc-guide/kernel-doc.rst b/Documentation/doc-guide/kernel-doc.rst
index 80383b1a574a..8db53cdc225f 100644
--- a/Documentation/doc-guide/kernel-doc.rst
+++ b/Documentation/doc-guide/kernel-doc.rst
@@ -488,14 +488,19 @@ doc: *title*
     .. kernel-doc:: drivers/gpu/drm/i915/intel_audio.c
        :doc: High Definition Audio over HDMI and Display Port
 
-functions: *function* *[...]*
+functions: *[ function ...]*
   Include documentation for each *function* in *source*.
+  If no *function* if specified, the documentaion for all functions
+  and types in the *source* will be included.
 
-  Example::
+  Examples::
 
     .. kernel-doc:: lib/bitmap.c
        :functions: bitmap_parselist bitmap_parselist_user
 
+    .. kernel-doc:: lib/idr.c
+       :functions:
+
 Without options, the kernel-doc directive includes all documentation comments
 from the source file.
 
diff --git a/Documentation/sphinx/kerneldoc.py b/Documentation/sphinx/kerneldoc.py
index fbedcc39460b..9d0a7f08f93b 100644
--- a/Documentation/sphinx/kerneldoc.py
+++ b/Documentation/sphinx/kerneldoc.py
@@ -47,7 +47,7 @@ class KernelDocDirective(Directive):
     optional_arguments = 4
     option_spec = {
         'doc': directives.unchanged_required,
-        'functions': directives.unchanged_required,
+        'functions': directives.unchanged,
         'export': directives.unchanged,
         'internal': directives.unchanged,
     }
@@ -75,8 +75,12 @@ class KernelDocDirective(Directive):
         elif 'doc' in self.options:
             cmd += ['-function', str(self.options.get('doc'))]
         elif 'functions' in self.options:
-            for f in str(self.options.get('functions')).split():
-                cmd += ['-function', f]
+            functions = self.options.get('functions').split()
+            if functions:
+                for f in functions:
+                    cmd += ['-function', f]
+            else:
+                cmd += ['-no-doc-sections']
 
         for pattern in export_file_patterns:
             for f in glob.glob(env.config.kerneldoc_srctree + '/' + pattern):