diff --git a/site_utils/control_file_preprocessor.py b/site_utils/control_file_preprocessor.py
new file mode 100755
index 0000000..a039486
--- /dev/null
+++ b/site_utils/control_file_preprocessor.py
@@ -0,0 +1,67 @@
+#!/usr/bin/python
+#
+# Copyright (c) 20123 The Chromium OS Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+"""Tool for preprocessing control files to build a suite to control files map.
+
+Given an autotest root directory, this tool will bucket tests accroding to
+their suite.Data will be written to stdout (or, optionally a file), eg:
+
+{'suite1': ['path/to/test1/control', 'path/to/test2/control'],
+ 'suite2': ['path/to/test4/control', 'path/to/test5/control']}
+
+This is intended for use only with Chrome OS test suites that leverage the
+dynamic suite infrastructure in server/cros/dynamic_suite.py. It is invoked
+at build time to generate said suite to control files map, which dynamic_suite
+consults at run time to determine which tests belong to a suite.
+"""
+
+
+import collections, json, os, sys
+
+import common
+from autotest_lib.server.cros.dynamic_suite import suite
+from autotest_lib.site_utils import suite_preprocessor
+
+
+def get_suite_control_files(autotest_dir):
+    """
+    Partition all control files in autotest_dir based on suite.
+
+    @param autotest_dir: Directory to walk looking for control files.
+    @return suite_control_files: A dictionary mapping suite->[control files]
+                                 as described in this files docstring.
+    @raise ValueError: If autotest_dir doesn't exist.
+    """
+    if not os.path.exists(autotest_dir):
+      raise ValueError('Could not find directory: %s, failed to map suites to'
+                       ' their control files.' % autotest_dir)
+
+    autotest_dir = autotest_dir.rstrip('/')
+    suite_control_files = collections.defaultdict(list)
+
+    for test in suite_preprocessor.get_all_suite_control_files(autotest_dir):
+        for suite_name in suite.Suite.parse_tag(test.suite):
+            suite_control_files[suite_name].append(
+                test.path.replace('%s/' % autotest_dir, ''))
+    return suite_control_files
+
+
+def main():
+    """
+    Main function.
+    """
+    options = suite_preprocessor.parse_options()
+
+    suite_control_files = get_suite_control_files(options.autotest_dir)
+    if options.output_file:
+        with open(options.output_file, 'w') as file_obj:
+            json.dump(suite_control_files, file_obj)
+    else:
+        print suite_control_files
+
+
+if __name__ == '__main__':
+    sys.exit(main())
diff --git a/site_utils/suite_preprocessor.py b/site_utils/suite_preprocessor.py
index 82ae668..d2a2131 100755
--- a/site_utils/suite_preprocessor.py
+++ b/site_utils/suite_preprocessor.py
@@ -28,6 +28,7 @@
 
 
 def parse_options():
+    """Parse command line arguments."""
     parser = optparse.OptionParser()
     parser.add_option('-a', '--autotest_dir', dest='autotest_dir',
                       default=os.path.abspath(
@@ -42,6 +43,18 @@
     return options
 
 
+def get_all_suite_control_files(autotest_dir):
+    """Find all control files in autotest_dir that have 'SUITE='
+
+    @param autotest_dir: The directory to search for control files.
+    @return: All control files in autotest_dir that have a suite attribute.
+    """
+    fs_getter = Suite.create_fs_getter(autotest_dir)
+    predicate = lambda t: hasattr(t, 'suite')
+    return Suite.find_and_parse_tests(fs_getter, predicate,
+                                      add_experimental=True)
+
+
 def calculate_dependencies(autotest_dir):
     """
     Traverse through the autotest directory and gather together the information
@@ -51,10 +64,8 @@
     @param autotest_dir The path to the autotest directory to examine for tests
     @return A dictionary of the form {suite: {test: [dep, dep]}}.
     """
-    fs_getter = Suite.create_fs_getter(autotest_dir)
-    predicate = lambda t: hasattr(t, 'suite')
     test_deps = {}  #  Format will be {suite: {test: [dep, dep]}}.
-    for test in Suite.find_and_parse_tests(fs_getter, predicate, True):
+    for test in get_all_suite_control_files(autotest_dir):
         for suite in Suite.parse_tag(test.suite):
             suite_deps = test_deps.setdefault(suite, {})
             # Force this to a list so that we can parse it later with
@@ -67,13 +78,14 @@
 
 
 def main():
+    """Main function."""
     options = parse_options()
 
     test_deps = calculate_dependencies(options.autotest_dir)
 
     if options.output_file:
-        with open(options.output_file, 'w+') as fd:
-            fd.write('%r' % test_deps)
+        with open(options.output_file, 'w') as file_obj:
+            file_obj.write('%r' % test_deps)
     else:
         print '%r' % test_deps