diff --git a/README.md b/README.md
index d5a8cef..d99abcb 100644
--- a/README.md
+++ b/README.md
@@ -20,7 +20,40 @@
 * clone_proj.sh to clone a git project for the unbundled development workflows
 in instead of the whole Android repo.
 
-## Chnage Reports
+## Change Reports
+
+### change_report.py
+change_report.py creates a diff statistic CSV file from 2 versions of a codebase.
+This is useful when the git commit history is somehow not obtainable. What you
+need is to get 2 versions of a codebase downloaded on your disk first.
+
+* You can compare specific folders of concern for a quick result, or when
+there is a code patch change.
+* This skips all symlinks & ignores common repository metadata folders, e.g.
+.git, etc.
+* It can take a long time & generates a large CSV file for the whole Android
+codebase & especially if they are many changes. For example:
+  * Android 11 QPR1 vs QPR2 takes more than 8 min. & generates a 5MB CSV file.
+  * Android 10 QPR3 vs Android 11 QPR2 takes more than 11 min. & generates a
+  95MB CSV file.
+* To reduce time, you should always remove **out**, the build output folder first.
+* For example, to compare Android 11 QPR1 vs QPR2 AOSP codebases on your disk.
+
+```
+python3 change_report.py --old_dir ~/android/android11-qpr1-release \
+  --new_dir ~/android/android11-qpr2-release \
+  --csv_file ~/change_reports/change_report_android11-qpr1-release_android11-qpr2-release.csv
+```
+
+* An output example: [change_report-new_vs_old_codebase.csv](dev/resource/change_report-new_vs_old_codebase.csv)
+is the change report between **dev/resource/old_codebase** and
+**new_codebase**.
+* The **states** are:
+  * SAME = 0
+  * NEW = 1
+  * REMOVED = 2
+  * MODIFIED = 3
+  * INCOMPARABLE = 4
 
 ### sysui_oem_diff.sh
 sysui_oem_diff.sh generates a summary of code changes between 2 revisions.
@@ -31,7 +64,7 @@
 * For example, to generate the change report for Android 11 to 10 QPR3: [sysui_gcar_android10-qpr3-release_android11-release.txt](dev/resource/sysui_gcar_android10-qpr3-release_android11-release.txt)
 
 ```
-$ ./sysui_oem_diff.sh ~/Android/android11-release remotes/aosp/android10-qpr3-release remotes/aosp/android11-release > sysui_gcar_android10-qpr3-release_android11-release.txt
+./sysui_oem_diff.sh ~/Android/android11-release remotes/aosp/android10-qpr3-release remotes/aosp/android11-release > sysui_gcar_android10-qpr3-release_android11-release.txt
 ```
 
 ## System Performance Tuning
diff --git a/dev/change_report.py b/dev/change_report.py
new file mode 100644
index 0000000..f6437c0
--- /dev/null
+++ b/dev/change_report.py
@@ -0,0 +1,399 @@
+#!/usr/bin/python3
+#
+# Copyright (C) 2021 The Android Open Source Project
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+"""Utilities for comparing two version of a codebase."""
+
+import argparse
+import difflib
+import filecmp
+import os
+import pathlib
+import re
+
+
+class FileStat:
+  """File statistics class for a file."""
+
+  NON_TEXT = 0
+  TEXT = 1
+
+  def __init__(self, file_path):
+    """Initializes with a file path string."""
+    if file_path:
+      self.file_name = str(file_path)
+      self.size = file_path.stat().st_size
+    else:
+      self.file_name = ''
+      self.size = 0
+
+    self.line_cnt = 0
+    self.group_cnt = 0
+    self.add_line_cnt = 0
+    self.remove_line_cnt = 0
+    self.replace_line_cnt = 0
+
+  @staticmethod
+  def get_csv_header(prefix=None):
+    """Returns CSV header string."""
+    cols = ['file', 'size', 'line', 'group', 'add', 'remove', 'replace']
+    if prefix:
+      return ','.join('{0}_{1}'.format(prefix, c) for c in cols)
+    else:
+      return ','.join(c for c in cols)
+
+  def get_csv_str(self, strip_dir_len=0):
+    """Returns the file statistic CSV string."""
+    name = self.file_name[strip_dir_len:]
+    csv = [
+        FileStat.no_comma(name), self.size, self.line_cnt, self.group_cnt,
+        self.add_line_cnt, self.remove_line_cnt, self.replace_line_cnt
+    ]
+    return ','.join(str(i) for i in csv)
+
+  @staticmethod
+  def no_comma(astr):
+    """Replaces , with _."""
+    return astr.replace(',', '_')
+
+
+class DiffStat:
+  """Diff statistic class for 2 versions of a file."""
+
+  SAME = 0
+  NEW = 1
+  REMOVED = 2
+  MODIFIED = 3
+  INCOMPARABLE = 4
+
+  def __init__(self, common_name, old_file_stat, new_file_stat, state):
+    """Initializes with the common names & etc."""
+    self.old_file_stat = old_file_stat
+    self.new_file_stat = new_file_stat
+    self.name = common_name
+    self.ext = os.path.splitext(self.name)[1].lstrip('.')
+    self.state = state
+    self.file_type = FileStat.NON_TEXT
+
+  def add_diff_stat(self, diff_lines):
+    """Adds the statistic by the diff lines."""
+    # These align with https://github.com/python/cpython/blob/3.9/Lib/difflib.py
+    old_pattern = re.compile(r'\*{3} (.*)')
+    new_pattern = re.compile(r'-{3} (.*)')
+    group_separator = '***************'
+    old_group_header = re.compile(r'\*{3} (\d*),(\d*) \*{4}')
+    new_group_header = re.compile(r'-{3} (\d*),(\d*) -{4}')
+
+    # section 0 is old verion & 1 is new verion
+    section = -1
+    diff_stats = [self.old_file_stat, self.new_file_stat]
+    in_group = False
+
+    h1m = old_pattern.match(diff_lines[0])
+    if not h1m:
+      print('ERROR: wrong diff header line 1: %s' % diff_lines[0])
+      return
+
+    h2m = new_pattern.match(diff_lines[1])
+    if not h2m:
+      print('ERROR: wrong diff header line 2: %s' % diff_lines[1])
+      return
+
+    for line in diff_lines[2:]:
+      if in_group:
+        if line.startswith('  '):
+          # equal
+          continue
+        elif line.startswith('! '):
+          # replace
+          diff_stats[section].replace_line_cnt += 1
+          continue
+        elif line.startswith('+ '):
+          # add
+          diff_stats[section].add_line_cnt += 1
+          continue
+        elif line.startswith('- '):
+          # removed
+          diff_stats[section].remove_line_cnt += 1
+          continue
+
+      oghm = old_group_header.match(line)
+      if oghm:
+        section = 0
+        diff_stats[section].group_cnt += 1
+        continue
+
+      nghm = new_group_header.match(line)
+      if nghm:
+        section = 1
+        diff_stats[section].group_cnt += 1
+        continue
+
+      if line.startswith(group_separator):
+        in_group = True
+        continue
+
+
+class ChangeReport:
+  """Change report class for the diff statistics on 2 versions of a codebase.
+
+  Attributes:
+    old_dir: The old codebase dir path string.
+    new_dir: The new codebase dir path string.
+    dircmp: The dircmp object
+    group_cnt: How many diff groups.
+    add_line_cnt: How many lines are added.
+    remove_line_cnt: How many lines are removed.
+    replace_line_cnt: Hoe many lines are changed.
+  """
+
+  def __init__(self, old_dir, new_dir, ignores=None, state_filter=None):
+    """Initializes with old & new dir path strings."""
+    self.old_dir = os.path.abspath(old_dir)
+    self._old_dir_prefix_len = len(self.old_dir) + 1
+    self.new_dir = os.path.abspath(new_dir)
+    self._new_dir_prefix_len = len(self.new_dir) + 1
+    if ignores:
+      self._ignores = ignores.split(',')
+      self._ignores.extend(filecmp.DEFAULT_IGNORES)
+    else:
+      self._ignores = filecmp.DEFAULT_IGNORES
+
+    if state_filter:
+      self._state_filter = list(map(int, state_filter.split(',')))
+    else:
+      self._state_filter = [0, 1, 2, 3, 4]
+
+    self._do_same = DiffStat.SAME in self._state_filter
+    self._do_new = DiffStat.NEW in self._state_filter
+    self._do_removed = DiffStat.REMOVED in self._state_filter
+    self._do_moeified = DiffStat.MODIFIED in self._state_filter
+    self._do_incomparable = DiffStat.INCOMPARABLE in self._state_filter
+
+    self.dircmp = filecmp.dircmp(
+        self.old_dir, self.new_dir, ignore=self._ignores)
+    self._diff_stats = []
+    self._diff_stat_lines = []
+    self._diff_lines = []
+    self._processed_cnt = 0
+    self._common_dir_len = ChangeReport.get_common_path_len(
+        self.old_dir, self.new_dir)
+
+  @staticmethod
+  def get_common_path_len(dir1, dir2):
+    """Gets the length of the common path of old & new folders."""
+    sep = os.path.sep
+    last_sep_pos = 0
+    for i in range(len(dir1)):
+      if dir1[i] == sep:
+        last_sep_pos = i
+      if dir1[i] != dir2[i]:
+        break
+    return last_sep_pos + 1
+
+  @staticmethod
+  def get_diff_stat_header():
+    """Gets the diff statistic CSV header."""
+    return 'file,ext,text,state,{0},{1}\n'.format(
+        FileStat.get_csv_header('new'), FileStat.get_csv_header('old'))
+
+  def get_diff_stat_lines(self):
+    """Gets the diff statistic CSV lines."""
+    if self._processed_cnt < 1:
+      self._process_dircmp(self.dircmp)
+      self._processed_cnt += 1
+
+      self._diff_stat_lines = []
+      for diff_stat in self._diff_stats:
+        self._diff_stat_lines.append('{0},{1},{2},{3},{4},{5}\n'.format(
+            FileStat.no_comma(diff_stat.name), diff_stat.ext,
+            diff_stat.file_type, diff_stat.state,
+            diff_stat.new_file_stat.get_csv_str(self._common_dir_len),
+            diff_stat.old_file_stat.get_csv_str(self._common_dir_len)))
+
+    return self._diff_stat_lines
+
+  def get_diff_lines(self):
+    """Gets the diff output lines."""
+    if self._processed_cnt < 1:
+      self._process_dircmp(self.dircmp)
+      self._processed_cnt += 1
+    return self._diff_lines
+
+  def _process_dircmp(self, dircmp):
+    """Compare all files in a dircmp object for diff statstics & output."""
+    if self._do_moeified:
+      self._process_diff_files(dircmp)
+
+    for subdir_dircmp in dircmp.subdirs.values():
+      rp = pathlib.Path(subdir_dircmp.right)
+      lp = pathlib.Path(subdir_dircmp.left)
+      if rp.is_symlink() or lp.is_symlink():
+        print('SKIP: symlink: {0} or {1}'.format(subdir_dircmp.right,
+                                                 subdir_dircmp.left))
+        continue
+      self._process_dircmp(subdir_dircmp)
+
+    if self._do_new:
+      self._process_others(dircmp.right_only, dircmp.right,
+                           self._new_dir_prefix_len, DiffStat.NEW)
+    if self._do_same:
+      self._process_others(dircmp.same_files, dircmp.right,
+                           self._new_dir_prefix_len, DiffStat.SAME)
+    if self._do_incomparable:
+      self._process_others(dircmp.funny_files, dircmp.right,
+                           self._new_dir_prefix_len, DiffStat.INCOMPARABLE)
+    if self._do_removed:
+      self._process_others(dircmp.left_only, dircmp.left,
+                           self._old_dir_prefix_len, DiffStat.REMOVED)
+
+  def _process_others(self, files, adir, prefix_len, state):
+    """Processes files are not modified."""
+    empty_stat = FileStat(None)
+    for file in files:
+      file_path = pathlib.Path(adir, file)
+      if file_path.is_symlink():
+        print('SKIP: symlink: {0}, {1}'.format(state, file_path))
+        continue
+      elif file_path.is_dir():
+        flist = self._get_filtered_files(file_path)
+        self._process_others(flist, adir, prefix_len, state)
+      else:
+        file_stat = FileStat(file_path)
+        common_name = str(file_path)[prefix_len:]
+        if state == DiffStat.REMOVED:
+          diff_stat = DiffStat(common_name, file_stat, empty_stat, state)
+        else:
+          diff_stat = DiffStat(common_name, empty_stat, file_stat, state)
+        try:
+          with open(file_path, encoding='utf-8') as f:
+            lines = f.readlines()
+          file_stat.line_cnt = len(lines)
+          file_type = FileStat.TEXT
+        except UnicodeDecodeError:
+          file_type = FileStat.NON_TEXT
+
+        diff_stat.file_type = file_type
+        self._diff_stats.append(diff_stat)
+
+  def _process_diff_files(self, dircmp):
+    """Processes files are modified."""
+    for file in dircmp.diff_files:
+      old_file_path = pathlib.Path(dircmp.left, file)
+      new_file_path = pathlib.Path(dircmp.right, file)
+      self._diff_files(old_file_path, new_file_path)
+
+  def _diff_files(self, old_file_path, new_file_path):
+    """Diff old & new files."""
+    old_file_stat = FileStat(old_file_path)
+    new_file_stat = FileStat(new_file_path)
+    common_name = str(new_file_path)[self._new_dir_prefix_len:]
+    diff_stat = DiffStat(common_name, old_file_stat, new_file_stat,
+                         DiffStat.MODIFIED)
+
+    try:
+      with open(old_file_path, encoding='utf-8') as f1:
+        old_lines = f1.readlines()
+      old_file_stat.line_cnt = len(old_lines)
+      with open(new_file_path, encoding='utf-8') as f2:
+        new_lines = f2.readlines()
+      new_file_stat.line_cnt = len(new_lines)
+      diff_lines = list(
+          difflib.context_diff(old_lines, new_lines, old_file_path.name,
+                               new_file_path.name))
+      file_type = FileStat.TEXT
+      if diff_lines:
+        self._diff_lines.extend(diff_lines)
+        diff_stat.add_diff_stat(diff_lines)
+      else:
+        print('WARNING: no diff lines on {0} {1}'.format(
+            old_file_path, new_file_path))
+
+    except UnicodeDecodeError:
+      file_type = FileStat.NON_TEXT
+
+    diff_stat.file_type = file_type
+    self._diff_stats.append(diff_stat)
+
+  def _get_filtered_files(self, dir_path):
+    """Returns a filtered file list."""
+    flist = []
+    for f in dir_path.glob('*'):
+      if f.name not in self._ignores:
+        if f.is_symlink():
+          print('SKIP: symlink: %s' % f)
+          continue
+        else:
+          flist.append(f)
+    return flist
+
+
+def write_file(file, lines, header=None):
+  """Write lines into a file."""
+
+  with open(file, 'w') as f:
+    if header:
+      f.write(header)
+
+    f.writelines(lines)
+  print('OUTPUT: {0}, {1} lines'.format(file, len(lines)))
+
+
+def main():
+  parser = argparse.ArgumentParser(
+      'Generate a diff stat cvs file for 2 versions of a codebase')
+  parser.add_argument('--old_dir', help='the old version codebase dir')
+  parser.add_argument('--new_dir', help='the new version codebase dir')
+  parser.add_argument(
+      '--csv_file', required=False, help='the diff stat cvs file if to create')
+  parser.add_argument(
+      '--diff_output_file',
+      required=False,
+      help='the diff output file if to create')
+  parser.add_argument(
+      '--ignores',
+      required=False,
+      default='.repo,.git,.github,.idea,__MACOSX,.prebuilt_info',
+      help='names to ignore')
+  parser.add_argument(
+      '--state_filter',
+      required=False,
+      default='1,2,3',
+      help='csv diff states to process, 0:SAME, 1:NEW, 2:REMOVED, 3:MODIFIED, '
+      '4:INCOMPARABLE')
+
+  args = parser.parse_args()
+
+  if not os.path.isdir(args.old_dir):
+    print('ERROR: %s does not exist.' % args.old_dir)
+    exit()
+
+  if not os.path.isdir(args.new_dir):
+    print('ERROR: %s does not exist.' % args.new_dir)
+    exit()
+
+  change_report = ChangeReport(args.old_dir, args.new_dir, args.ignores,
+                               args.state_filter)
+  if args.csv_file:
+    write_file(
+        args.csv_file,
+        change_report.get_diff_stat_lines(),
+        header=ChangeReport.get_diff_stat_header())
+
+  if args.diff_output_file:
+    write_file(args.diff_output_file, change_report.get_diff_lines())
+
+
+if __name__ == '__main__':
+  main()
diff --git a/dev/change_report_test.py b/dev/change_report_test.py
new file mode 100644
index 0000000..20d6483
--- /dev/null
+++ b/dev/change_report_test.py
@@ -0,0 +1,104 @@
+#!/usr/bin/python3
+#
+# Copyright (C) 2021 The Android Open Source Project
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+"""Tests for change_report.py."""
+
+import os
+import pathlib
+import unittest
+
+import change_report
+
+
+class ChangeReportTest(unittest.TestCase):
+  """Tests for ChangeReport."""
+
+  def setUp(self):
+    super().setUp()
+    old_dir = str(ChangeReportTest.get_resrouce_path('old_codebase'))
+    new_dir = str(ChangeReportTest.get_resrouce_path('new_codebase'))
+    self.change_report = change_report.ChangeReport(
+        old_dir, new_dir, state_filter='0,1,2,3,4')
+
+  def test_get_diff_stat_lines(self):
+    """Tests if the diff stat of new & old_codebase matches change_report-new_vs_old_codebase.csv."""
+    diff_stat_lines = []
+    diff_stat_lines.append(change_report.ChangeReport.get_diff_stat_header())
+    diff_stat_lines.extend(self.change_report.get_diff_stat_lines())
+
+    expected_diff_stat_lines = ChangeReportTest.get_expected_lines(
+        'change_report-new_vs_old_codebase.csv')
+
+    offending_line_indexes = ChangeReportTest.diff_lines(
+        expected_diff_stat_lines, diff_stat_lines)
+    self.assertEqual(len(offending_line_indexes), 0)
+
+  def test_get_diff_lines(self):
+    """Tests if the diff stat of new & old_codebase matches change_report_diff-new_vs_old_codebase.txt."""
+    diff_lines = self.change_report.get_diff_lines()
+
+    expected_diff_lines = ChangeReportTest.get_expected_lines(
+        'change_report_diff-new_vs_old_codebase.txt')
+
+    offending_line_indexes = ChangeReportTest.diff_lines(
+        expected_diff_lines, diff_lines)
+    self.assertEqual(len(offending_line_indexes), 0)
+
+  @staticmethod
+  def get_resrouce_path(target):
+    # .../dev/change_report_test.py
+    this_path = pathlib.Path(os.path.abspath(__file__)).parents[0]
+    return pathlib.Path(this_path, 'resource', target)
+
+  @staticmethod
+  def get_expected_lines(target):
+    file = ChangeReportTest.get_resrouce_path(target)
+    with open(file, 'r') as f:
+      lines = f.readlines()
+    return lines
+
+  @staticmethod
+  def diff_lines(expected, actual):
+    expected_len = len(expected)
+    actual_len = len(actual)
+    offending_line_indexes = []
+
+    if actual_len < expected_len:
+      l = actual_len
+    else:
+      l = expected_len
+
+    for i in range(l):
+      if expected[i] != actual[i]:
+        print('ERROR: line %d is not as expected' % i)
+        print(expected[i])
+        print(actual[i])
+        offending_line_indexes.append(i)
+
+    if actual_len < expected_len:
+      print('ERROR: Missing %d lines' % (expected_len - actual_len))
+      for j in range(actual_len, expected_len):
+        print(expected[j])
+        offending_line_indexes.append(j)
+    elif actual_len > expected_len:
+      print('ERROR: Extra %d lines' % (actual_len - expected_len))
+      for k in range(expected_len, actual_len):
+        print(actual[k])
+        offending_line_indexes.append(k)
+    return offending_line_indexes
+
+
+if __name__ == '__main__':
+  unittest.main()
diff --git a/dev/resource/change_report-new_vs_old_codebase.csv b/dev/resource/change_report-new_vs_old_codebase.csv
new file mode 100644
index 0000000..63e8e0b
--- /dev/null
+++ b/dev/resource/change_report-new_vs_old_codebase.csv
@@ -0,0 +1,18 @@
+file,ext,text,state,new_file,new_size,new_line,new_group,new_add,new_remove,new_replace,old_file,old_size,old_line,old_group,old_add,old_remove,old_replace
+modified_comma_.txt,txt,1,3,new_codebase/modified_comma_.txt,300,103,3,3,0,3,old_codebase/modified_comma_.txt,299,101,3,0,2,2
+modified.png,png,0,3,new_codebase/modified.png,4065,0,0,0,0,0,old_codebase/modified.png,4044,0,0,0,0,0
+modified.txt,txt,1,3,new_codebase/modified.txt,300,103,3,3,0,3,old_codebase/modified.txt,299,101,3,0,2,2
+modified_sub_dir/modified.txt,txt,1,3,new_codebase/modified_sub_dir/modified.txt,300,103,3,3,0,3,old_codebase/modified_sub_dir/modified.txt,299,101,3,0,2,2
+modified_sub_dir/sub_sub_dir/modified.txt,txt,1,3,new_codebase/modified_sub_dir/sub_sub_dir/modified.txt,300,103,3,3,0,3,old_codebase/modified_sub_dir/sub_sub_dir/modified.txt,299,101,3,0,2,2
+same_sub_dir/sub_sub_dir/same.txt,txt,1,0,new_codebase/same_sub_dir/sub_sub_dir/same.txt,21,10,0,0,0,0,,0,0,0,0,0,0
+same_sub_dir/same.txt,txt,1,0,new_codebase/same_sub_dir/same.txt,21,10,0,0,0,0,,0,0,0,0,0,0
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diff --git a/dev/resource/change_report_diff-new_vs_old_codebase.txt b/dev/resource/change_report_diff-new_vs_old_codebase.txt
new file mode 100644
index 0000000..31c9fa7
--- /dev/null
+++ b/dev/resource/change_report_diff-new_vs_old_codebase.txt
@@ -0,0 +1,144 @@
+*** modified,comma,.txt
+--- modified,comma,.txt
+***************
+*** 1,3 ****
+--- 1,6 ----
++ -2
++ -1
++ 0
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+! 99
+! 100
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+--- modified.txt
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++ -1
++ 0
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+--- modified.txt
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++ -2
++ -1
++ 0
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+! 99
+! 100
+*** modified.txt
+--- modified.txt
+***************
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++ -2
++ -1
++ 0
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diff --git a/dev/resource/new_codebase/modified,comma,.txt b/dev/resource/new_codebase/modified,comma,.txt
new file mode 100644
index 0000000..a3e1e72
--- /dev/null
+++ b/dev/resource/new_codebase/modified,comma,.txt
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diff --git a/dev/resource/new_codebase/modified.png b/dev/resource/new_codebase/modified.png
new file mode 100644
index 0000000..6ca162a
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Binary files differ
diff --git a/dev/resource/new_codebase/modified.txt b/dev/resource/new_codebase/modified.txt
new file mode 100644
index 0000000..a3e1e72
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new file mode 100644
index 0000000..a3e1e72
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new file mode 100644
index 0000000..a3e1e72
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diff --git a/dev/resource/new_codebase/modified_sub_dir/sub_sub_dir/relative_symbolic_sub_dir b/dev/resource/new_codebase/modified_sub_dir/sub_sub_dir/relative_symbolic_sub_dir
new file mode 120000
index 0000000..a96aa0e
--- /dev/null
+++ b/dev/resource/new_codebase/modified_sub_dir/sub_sub_dir/relative_symbolic_sub_dir
@@ -0,0 +1 @@
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\ No newline at end of file
diff --git a/dev/resource/new_codebase/new.png b/dev/resource/new_codebase/new.png
new file mode 100644
index 0000000..82f73fe
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Binary files differ
diff --git a/dev/resource/new_codebase/new.txt b/dev/resource/new_codebase/new.txt
new file mode 100644
index 0000000..f00c965
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diff --git a/dev/resource/new_codebase/new_sub_dir/new.txt b/dev/resource/new_codebase/new_sub_dir/new.txt
new file mode 100644
index 0000000..f00c965
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new file mode 100644
index 0000000..f00c965
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diff --git a/dev/resource/new_codebase/new_sub_dir/sub_sub_dir/relative_symbolic_sub_dir b/dev/resource/new_codebase/new_sub_dir/sub_sub_dir/relative_symbolic_sub_dir
new file mode 120000
index 0000000..a96aa0e
--- /dev/null
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diff --git a/dev/resource/new_codebase/same.png b/dev/resource/new_codebase/same.png
new file mode 100644
index 0000000..57585da
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Binary files differ
diff --git a/dev/resource/new_codebase/same.txt b/dev/resource/new_codebase/same.txt
new file mode 100644
index 0000000..f00c965
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new file mode 100644
index 0000000..f00c965
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diff --git a/dev/resource/new_codebase/same_sub_dir/sub_sub_dir/relative_symbolic_sub_dir b/dev/resource/new_codebase/same_sub_dir/sub_sub_dir/relative_symbolic_sub_dir
new file mode 120000
index 0000000..a96aa0e
--- /dev/null
+++ b/dev/resource/new_codebase/same_sub_dir/sub_sub_dir/relative_symbolic_sub_dir
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diff --git a/dev/resource/new_codebase/same_sub_dir/sub_sub_dir/same.txt b/dev/resource/new_codebase/same_sub_dir/sub_sub_dir/same.txt
new file mode 100644
index 0000000..f00c965
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new file mode 100644
index 0000000..471fe15
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new file mode 100644
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Binary files differ
diff --git a/dev/resource/old_codebase/modified.txt b/dev/resource/old_codebase/modified.txt
new file mode 100644
index 0000000..471fe15
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new file mode 100644
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new file mode 100644
index 0000000..471fe15
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new file mode 120000
index 0000000..a96aa0e
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new file mode 100644
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new file mode 100644
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new file mode 100644
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new file mode 120000
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new file mode 100644
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+2
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diff --git a/dev/resource/old_codebase/same.png b/dev/resource/old_codebase/same.png
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diff --git a/dev/resource/old_codebase/same.txt b/dev/resource/old_codebase/same.txt
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diff --git a/dev/resource/old_codebase/same_sub_dir/sub_sub_dir/relative_symbolic_sub_dir b/dev/resource/old_codebase/same_sub_dir/sub_sub_dir/relative_symbolic_sub_dir
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+..
\ No newline at end of file
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diff --git a/validation/README.md b/validation/README.md
new file mode 100644
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--- /dev/null
+++ b/validation/README.md
@@ -0,0 +1,39 @@
+# Validation Tools
+This is a collection of validation tools for better development & integration
+productivity for AAOS devices.
+
+## Validating new app releases
+Incoming quality control is an important practice to prevent new technical debts
+added to risk the device development. These scripts illustrate a basic check for
+a new app bundle release against a known good virtual or physical device build.
+So that, you know what changed better & if they break any basic use cases.
+
+1. Prepare a new app release in a directory, a device under test reachable
+via adb & aapt is available in the shell environment.
+```
+appDir="/path/to/appDir"
+renameCsv="/path/to/renameCsvFile"
+```
+
+- As sometime mk file change the file name when copying XML files to the device at the build time, you can supply a CSV file to guide the script. The format is as:
+```
+name,newName
+privapp-permissions-in-app-release.xml,privapp-permissions-on-device.xml
+```
+
+2. batch_install_app.sh: find & install all APKs in a given directory to
+a device via adb. Launch their launchable activities if any & capture
+screenshots. To use:
+
+```
+./batch_install_app.sh ${appDir}
+```
+
+3. batch_check_permission.sh: find & diff permissions XML files in a given
+directory against those on a device via adb. To use:
+
+```
+./batch_check_permission.sh ${appDir} ${renameCsv}
+```
+
+4. test.sh has all the commands above to make is easier to use.
diff --git a/validation/batch_check_permission.sh b/validation/batch_check_permission.sh
new file mode 100755
index 0000000..5af4e91
--- /dev/null
+++ b/validation/batch_check_permission.sh
@@ -0,0 +1,117 @@
+#!/bin/bash
+
+# Copyright (C) 2021 The Android Open Source Project
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+readme() {
+  echo '''
+  check permissions xml from a apk bundle release aginast those on a device
+  ./batch_check_permission.sh ~/Downloads/apk_bundle_dir ~/Downloads/override.csv
+'''
+}
+
+SECONDS=0
+MY_NAME=$0
+SCRIPT_NAME="${MY_NAME##*/}"
+SCRIPT_DIR="${MY_NAME%/$SCRIPT_NAME}"
+echo Running from $SCRIPT_DIR
+
+if [[ -z $OUT_DIR ]]; then
+  OUT_DIR="${HOME}/Downloads"
+fi
+
+INPUT_DIR=$1
+if [[ -z "${INPUT_DIR}" ]]; then
+  readme
+  exit
+fi
+
+RENAME_CSV=$2
+# Read rename csv to create xmlRenameDic
+declare -A xmlRenameDic
+if [[ -f ${RENAME_CSV} ]]; then
+  while IFS=',' read -r name newName others || [ -n "${name}" ]; do
+    if [[ "${name}" == "name" ]]; then
+      # skip header
+      header="${name},${newName}"
+    else
+      xmlRenameDic["${name}"]="${newName}"
+    fi
+  done < $RENAME_CSV
+fi
+
+echo "LOG=${LOG}"
+log() {
+  if [[ -n ${LOG} ]]; then
+    echo $1
+  fi
+}
+
+echo "Listing xmls in ${INPUT_DIR}"
+declare -A relXmlDic
+
+declare -A relXmlDic="$(${SCRIPT_DIR}/get_file_dir.sh ${INPUT_DIR} xml)"
+echo "Found: ${#relXmlDic[@]} xmls"
+
+echo "Listing xmls in the device"
+declare -A deviceXmlDic
+deviceXmlList=$(adb shell "find / -name *.xml" 2>/dev/null)
+for xml in ${deviceXmlList}; do
+  file=${xml##*/}
+  fPath=${xml%/*}
+  fParentPathPostfix=${fPath:(-11)}
+  if [[ "permissions" == ${fParentPathPostfix} ]]; then
+    deviceXmlDic[${file}]=${xml}
+    log "${file} ${fPath} ${fParentPathPostfix}"
+  fi
+done
+echo "Found: ${#deviceXmlDic[@]} xmls"
+
+echo "Comparing xmls from ${INPUT_DIR} to those on the device."
+i=1
+for xml in "${!relXmlDic[@]}"; do
+  # relFile="...google/etc/permissions/privapp-permissions-car.xml"
+  relFile=${relXmlDic[$xml]}
+  # fPath="...google/etc/permissions"
+  fPath=${relFile%/*}
+  # fParentPathPostfix="permissions"
+  fParentPathPostfix=${fPath:(-11)}
+  log "${xml} ${fPath} ${fParentPathPostfix}"
+
+  # Only care about permissions
+  if [[ "permissions" == ${fParentPathPostfix} ]]; then
+    echo "$i Comparing permission file: $xml"
+
+    deviceFile=${deviceXmlDic[$xml]}
+    if [[ -z ${deviceFile} ]]; then
+      # Maybe it's renamed
+      newXml=${xmlRenameDic[$xml]}
+      log "Rename $xml to $newXml"
+      deviceFile=${deviceXmlDic[$newXml]}
+      if [[ -z ${deviceFile} ]]; then
+        echo "Error: no ${xml} on the device."
+        echo
+        i=$(($i + 1))
+        continue
+      fi
+    fi
+
+    # Pull the xml from device & diff
+    adb pull "${deviceFile}" "${OUT_DIR}/${xml}"
+    diff "${relXmlDic[$xml]}" "${OUT_DIR}/${xml}"
+    i=$(($i + 1))
+    echo
+  fi
+done
+echo "Took ${SECONDS} seconds"
diff --git a/validation/batch_install_app.sh b/validation/batch_install_app.sh
new file mode 100755
index 0000000..6e0cd97
--- /dev/null
+++ b/validation/batch_install_app.sh
@@ -0,0 +1,110 @@
+#!/bin/bash
+
+# Copyright (C) 2021 The Android Open Source Project
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+readme() {
+  echo '''
+Install apps in an app bundle release directory to the device via adb, e.g.
+./batch_install_app.sh /path/to/app_bundle /path/to/report
+
+Note: aapt is needed to get the metadata from APKs.
+'''
+}
+
+SECONDS=0
+MY_NAME=$0
+SCRIPT_NAME="${MY_NAME##*/}"
+SCRIPT_DIR="${MY_NAME%/$SCRIPT_NAME}"
+echo Running from $SCRIPT_DIR
+
+if [[ -z $OUT_DIR ]]; then
+  OUT_DIR="${HOME}/Downloads"
+fi
+
+INPUT_DIR=$1
+if [[ ! -d ${INPUT_DIR} ]]; then
+  echo "Error: ${INPUT_DIR} is not a directory."
+  readme
+  exit
+fi
+
+echo "LOG=${LOG}"
+log() {
+  if [[ -n ${LOG} ]]; then
+    echo $1
+  fi
+}
+
+# check an app/package version via adb, e.g.
+# checkAppVersion package_name
+checkAppVersion() {
+  pkg=$1
+  cmd="adb shell dumpsys package ${pkg}"
+  dump=$(${cmd})
+  log "$dump"
+  echo "${dump}" | grep versionName
+}
+
+echo "Process all APKs in ${INPUT_DIR}"
+# apkDic[apk_name]=apk_path
+declare -A apkDic="$(${SCRIPT_DIR}/get_file_dir.sh ${INPUT_DIR} apk)"
+echo "Found: ${#apkDic[@]} apks"
+
+screenshotDir="/data/local/tmp/screenshots"
+echo "Removig the following screenshots from the device"
+adb shell ls -l ${screenshotDir}
+adb shell rm -r ${screenshotDir}
+adb shell mkdir -p ${screenshotDir}
+
+# apkBadgingDic[apk_name]=aapt_badging_output_string
+declare -A apkBadgingDic
+# manifestDic[apk_name]=AndroidManifest_xml_content_string
+declare -A manifestDic
+i=1
+for apk in "${!apkDic[@]}"; do
+  path="${apkDic[${apk}]}"
+  badging=$(aapt dump badging ${path})
+  apkBadgingDic[${apk}]="\"${badging}\""
+  log "${apkBadgingDic[${apk}]}"
+
+  # Get package name from the aapt badging output string
+  # ... package: name='com.google.android.gsf' versionCode...
+  pkg0=${badging#package: name=\'}
+  pkg=${pkg0%\' versionCode*}
+
+  echo "$i,${pkg},${apk},${path}"
+  checkAppVersion ${pkg}
+  ${SCRIPT_DIR}/install_apk.sh ${path}
+  checkAppVersion ${pkg}
+  echo
+
+  # Get the 1st launchable activity
+  # ... launchable-activity: name='com.google.android.maps.MapsActivity'  label...
+  if [[ "$badging" == *"launchable-activity: name="* ]]; then
+    activity0=${badging#*launchable-activity: name=\'}
+    activity=${activity0%%\'  label=*}
+    echo "Launching an activity: ${activity}"
+    adb shell am start -n "${pkg}/${activity}"
+    sleep 5
+    adb shell screencap "${screenshotDir}/${pkg}.png"
+    echo "grep screen"
+  fi
+
+  i=$(($i + 1))
+done
+
+adb shell ls -l ${screenshotDir}
+adb pull ${screenshotDir} ${OUT_DIR}
+echo "Took ${SECONDS} seconds"
diff --git a/validation/get_file_dir.sh b/validation/get_file_dir.sh
new file mode 100755
index 0000000..58ee16d
--- /dev/null
+++ b/validation/get_file_dir.sh
@@ -0,0 +1,32 @@
+#!/bin/bash
+
+# Copyright (C) 2021 The Android Open Source Project
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# Get a dictionary of all the file_extension files in a directory, e.g.
+# declare -a aDic="$(.\get_file_dir.sh directory file_extension)"
+declare -A aDic
+
+dir=$1
+ext=$2
+if [[ -d ${dir} ]]; then
+  cd ${dir} && fList=$(find "${dir}" -name "*.${ext}")
+
+  echo '( \'
+  for f in ${fList}; do
+    fileName=${f##*/}
+    echo "[${fileName}]=\"$f\" \\"
+  done
+  echo ')'
+fi
diff --git a/validation/install_apk.sh b/validation/install_apk.sh
new file mode 100755
index 0000000..00a059c
--- /dev/null
+++ b/validation/install_apk.sh
@@ -0,0 +1,28 @@
+#!/bin/bash
+
+# Copyright (C) 2021 The Android Open Source Project
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# install an apk via adb, e.g.
+# ./install_app.sh apk_path
+declare -A aDic
+
+apk=$1
+if [[ -f ${apk} ]]; then
+  echo "Installing ${apk}"
+  cmd="adb install -r ${apk}"
+  eval "${cmd}"
+else
+  echo "Error: Can not find ${apk}"
+fi
diff --git a/validation/test.sh b/validation/test.sh
new file mode 100755
index 0000000..5a9bf61
--- /dev/null
+++ b/validation/test.sh
@@ -0,0 +1,28 @@
+#!/bin/bash
+
+# Copyright (C) 2021 The Android Open Source Project
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+echo test install new app release
+
+appDir=$1
+renameCsv=$2
+
+echo ${appDir}
+echo ${renameCsv}
+cat ${renameCsv}
+adb shell getprop | grep finger
+
+./batch_install_app.sh ${appDir}
+./batch_check_permission.sh ${appDir} ${renameCsv}