Add a script to generate Coccinelle semantic patch
removing all pointless QOM cast macro uses.

Suggested-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
---
 MAINTAINERS                               |  1 +
 scripts/qom-cast-macro-clean-cocci-gen.py | 49 +++++++++++++++++++++++
 2 files changed, 50 insertions(+)
 create mode 100644 scripts/qom-cast-macro-clean-cocci-gen.py

diff --git a/MAINTAINERS b/MAINTAINERS
index 4b025a7b63..37a2412011 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -3044,6 +3044,7 @@ F: include/qom/
 F: qapi/qom.json
 F: qapi/qdev.json
 F: scripts/coccinelle/qom-parent-type.cocci
+F: scripts/qom-cast-macro-clean-cocci-gen.py
 F: softmmu/qdev-monitor.c
 F: stubs/qdev.c
 F: qom/
diff --git a/scripts/qom-cast-macro-clean-cocci-gen.py b/scripts/qom-cast-macro-clean-cocci-gen.py
new file mode 100644
index 0000000000..2fa8438a14
--- /dev/null
+++ b/scripts/qom-cast-macro-clean-cocci-gen.py
@@ -0,0 +1,49 @@
+#!/usr/bin/env python3
+#
+# Generate a Coccinelle semantic patch to remove pointless QOM cast.
+#
+# Usage:
+#
+# $ qom-cast-macro-clean-cocci-gen.py $(git ls-files) > qom_pointless_cast.cocci
+# $ spatch \
+#           --macro-file scripts/cocci-macro-file.h \
+#           --sp-file qom_pointless_cast.cocci \
+#           --keep-comments \
+#           --use-gitgrep \
+#           --in-place \
+#           --dir .
+#
+# SPDX-FileContributor: Philippe Mathieu-Daudé <philmd@linaro.org>
+# SPDX-FileCopyrightText: 2023 Linaro Ltd.
+# SPDX-License-Identifier: GPL-2.0-or-later
+
+import re
+import sys
+
+assert len(sys.argv) > 0
+
+def print_cocci_rule(qom_typedef, qom_cast_macro):
+    print(f'''@@
+typedef {qom_typedef};
+{qom_typedef} *obj;
+@@
+-    {qom_cast_macro}(obj)
++    obj
+''')
+
+patterns = [
+    r'DECLARE_INSTANCE_CHECKER\((\w+),\W*(\w+),\W*TYPE_\w+\)',
+    r'DECLARE_OBJ_CHECKERS\((\w+),\W*\w+,\W*(\w+),\W*TYPE_\w+\)',
+    r'OBJECT_DECLARE_TYPE\((\w+),\W*\w+,\W*(\w+)\)',
+    r'OBJECT_DECLARE_SIMPLE_TYPE\((\w+),\W*(\w+)\)',
+    r'INTERFACE_CHECK\((\w+),\W*\(\w+\),\W*TYPE_(\w+)\)',
+]
+
+for fn in sys.argv[1:]:
+    try:
+        content = open(fn, 'rt').read()
+    except:
+        continue
+    for pattern in patterns:
+        for match in re.findall(pattern, content):
+            print_cocci_rule(match[0], match[1])
-- 
2.38.1