diff --git a/tools/releasetools/add_img_to_target_files.py b/tools/releasetools/add_img_to_target_files.py
index 9e44263..02e940e 100755
--- a/tools/releasetools/add_img_to_target_files.py
+++ b/tools/releasetools/add_img_to_target_files.py
@@ -184,11 +184,9 @@
     print "userdata.img already exists in %s, no need to rebuild..." % (prefix,)
     return
 
+  # Skip userdata.img if no size.
   image_props = build_image.ImagePropFromGlobalDict(OPTIONS.info_dict, "data")
-  # We only allow yaffs to have a 0/missing partition_size.
-  # Extfs, f2fs must have a size. Skip userdata.img if no size.
-  if (not image_props.get("fs_type", "").startswith("yaffs") and
-      not image_props.get("partition_size")):
+  if not image_props.get("partition_size"):
     return
 
   print "creating userdata.img..."
diff --git a/tools/releasetools/build_image.py b/tools/releasetools/build_image.py
index abb23d1..69b1ba8 100755
--- a/tools/releasetools/build_image.py
+++ b/tools/releasetools/build_image.py
@@ -390,14 +390,8 @@
     build_command = ["mkf2fsuserimg.sh"]
     build_command.extend([out_file, prop_dict["partition_size"]])
   else:
-    build_command = ["mkyaffs2image", "-f"]
-    if prop_dict.get("mkyaffs2_extra_flags", None):
-      build_command.extend(prop_dict["mkyaffs2_extra_flags"].split())
-    build_command.append(in_dir)
-    build_command.append(out_file)
-    if "selinux_fc" in prop_dict:
-      build_command.append(prop_dict["selinux_fc"])
-      build_command.append(prop_dict["mount_point"])
+    print("Error: unknown filesystem type '%s'" % (fs_type))
+    return False
 
   if in_dir != origin_in:
     # Construct a staging directory of the root file system.
@@ -501,7 +495,6 @@
   common_props = (
       "extfs_sparse_flag",
       "squashfs_sparse_flag",
-      "mkyaffs2_extra_flags",
       "selinux_fc",
       "skip_fsck",
       "verity",
diff --git a/tools/releasetools/common.py b/tools/releasetools/common.py
index 92af547..9d080d9 100644
--- a/tools/releasetools/common.py
+++ b/tools/releasetools/common.py
@@ -128,14 +128,6 @@
   # files.  Look for them, in case we're processing an old
   # target_files zip.
 
-  if "mkyaffs2_extra_flags" not in d:
-    try:
-      d["mkyaffs2_extra_flags"] = read_helper(
-          "META/mkyaffs2-extra-flags.txt").strip()
-    except KeyError:
-      # ok if flags don't exist
-      pass
-
   if "recovery_api_version" not in d:
     try:
       d["recovery_api_version"] = read_helper(
@@ -816,10 +808,6 @@
   if not fs_type or not limit:
     return
 
-  if fs_type == "yaffs2":
-    # image size should be increased by 1/64th to account for the
-    # spare area (64 bytes per 2k page)
-    limit = limit / 2048 * (2048+64)
   size = len(data)
   pct = float(size) * 100.0 / limit
   msg = "%s size (%d) is %.2f%% of limit (%d)" % (target, size, pct, limit)
@@ -1615,8 +1603,6 @@
 
 # map recovery.fstab's fs_types to mount/format "partition types"
 PARTITION_TYPES = {
-    "yaffs2": "MTD",
-    "mtd": "MTD",
     "ext4": "EMMC",
     "emmc": "EMMC",
     "f2fs": "EMMC",
diff --git a/tools/releasetools/edify_generator.py b/tools/releasetools/edify_generator.py
index ecdc167..5c67ba1 100644
--- a/tools/releasetools/edify_generator.py
+++ b/tools/releasetools/edify_generator.py
@@ -167,7 +167,7 @@
     self.script.append("set_progress(%f);" % (frac,))
 
   def PatchCheck(self, filename, *sha1):
-    """Check that the given file (or MTD reference) has one of the
+    """Check that the given file has one of the
     given *sha1 hashes, checking the version saved in cache if the
     file does not match."""
     self.script.append(
@@ -176,7 +176,7 @@
         ') || abort("\\"%s\\" has unexpected contents.");' % (filename,))
 
   def Verify(self, filename):
-    """Check that the given file (or MTD reference) has one of the
+    """Check that the given file has one of the
     given hashes (encoded in the filename)."""
     self.script.append(
         'apply_patch_check("{filename}") && '
@@ -185,7 +185,7 @@
             filename=filename))
 
   def FileCheck(self, filename, *sha1):
-    """Check that the given file (or MTD reference) has one of the
+    """Check that the given file has one of the
     given *sha1 hashes."""
     self.script.append('assert(sha1_check(read_file("%s")' % (filename,) +
                        "".join([', "%s"' % (i,) for i in sha1]) +
@@ -322,11 +322,7 @@
       p = fstab[mount_point]
       partition_type = common.PARTITION_TYPES[p.fs_type]
       args = {'device': p.device, 'fn': fn}
-      if partition_type == "MTD":
-        self.script.append(
-            'write_raw_image(package_extract_file("%(fn)s"), "%(device)s");'
-            % args)
-      elif partition_type == "EMMC":
+      if partition_type == "EMMC":
         if mapfn:
           args["map"] = mapfn
           self.script.append(