diff --git a/tools/aconfig/src/codegen.rs b/tools/aconfig/src/codegen.rs
new file mode 100644
index 0000000..b60ec51
--- /dev/null
+++ b/tools/aconfig/src/codegen.rs
@@ -0,0 +1,43 @@
+/*
+ * Copyright (C) 2023 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.
+ */
+
+pub fn is_valid_identifier(s: &str) -> bool {
+    // Identifiers must match [a-z][a-z0-9_]*
+    let mut chars = s.chars();
+    let Some(first) = chars.next() else {
+        return false;
+    };
+    if !first.is_ascii_lowercase() {
+        return false;
+    }
+    chars.all(|ch| ch.is_ascii_lowercase() || ch.is_ascii_digit() || ch == '_')
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_is_valid_identifier() {
+        assert!(is_valid_identifier("foo"));
+        assert!(is_valid_identifier("foo_bar_123"));
+
+        assert!(!is_valid_identifier(""));
+        assert!(!is_valid_identifier("123_foo"));
+        assert!(!is_valid_identifier("foo-bar"));
+        assert!(!is_valid_identifier("foo-b\u{00e5}r"));
+    }
+}