docs: kdoc: consolidate the stripping of private struct/union members

There were two locations duplicating the logic of stripping private members
and associated comments; coalesce them into one, and add some comments
describing what's going on.

Output change: we now no longer add extraneous white space around macro
definitions.

Reviewed-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Link: https://lore.kernel.org/r/20250807211639.47286-2-corbet@lwn.net

scripts/lib/kdoc/kdoc_parser.py

@@ -81,6 +81,21 @@ multi_space = KernRe(r'\s\s+')
 def trim_whitespace(s):
     return multi_space.sub(' ', s.strip())
 
+#
+# Remove struct/enum members that have been marked "private".
+#
+def trim_private_members(text):
+    #
+    # First look for a "public:" block that ends a private region, then
+    # handle the "private until the end" case.
+    #
+    text = KernRe(r'/\*\s*private:.*?/\*\s*public:.*?\*/', flags=re.S).sub('', text)
+    text = KernRe(r'/\*\s*private:.*', flags=re.S).sub('', text)
+    #
+    # We needed the comments to do the above, but now we can take them out.
+    #
+    return KernRe(r'\s*/\*.*?\*/\s*', flags=re.S).sub('', text).strip()
+
 class state:
     """
     State machine enums
@@ -568,12 +583,6 @@ class KernelDoc:
         args_pattern = r'([^,)]+)'
 
         sub_prefixes = [
-            (KernRe(r'\/\*\s*private:.*?\/\*\s*public:.*?\*\/', re.S | re.I), ''),
-            (KernRe(r'\/\*\s*private:.*', re.S | re.I), ''),
-
-            # Strip comments
-            (KernRe(r'\/\*.*?\*\/', re.S), ''),
-
             # Strip attributes
             (attribute, ' '),
             (KernRe(r'\s*__aligned\s*\([^;]*\)', re.S), ' '),
@@ -648,6 +657,7 @@ class KernelDoc:
             (re.compile(r'\bSTRUCT_GROUP\('), r'\1'),
         ]
 
+        members = trim_private_members(members)
         for search, sub in sub_prefixes:
             members = search.sub(sub, members)
 
@@ -797,24 +807,18 @@ class KernelDoc:
         """
         Stores an enum inside self.entries array.
         """
-
-        # Ignore members marked private
-        proto = KernRe(r'\/\*\s*private:.*?\/\*\s*public:.*?\*\/', flags=re.S).sub('', proto)
-        proto = KernRe(r'\/\*\s*private:.*}', flags=re.S).sub('}', proto)
-
-        # Strip comments
-        proto = KernRe(r'\/\*.*?\*\/', flags=re.S).sub('', proto)
-
-        # Strip #define macros inside enums
+        #
+        # Strip preprocessor directives.  Note that this depends on the
+        # trailing semicolon we added in process_proto_type().
+        #
         proto = KernRe(r'#\s*((define|ifdef|if)\s+|endif)[^;]*;', flags=re.S).sub('', proto)
-
         #
         # Parse out the name and members of the enum.  Typedef form first.
         #
         r = KernRe(r'typedef\s+enum\s*\{(.*)\}\s*(\w*)\s*;')
         if r.search(proto):
             declaration_name = r.group(2)
-            members = r.group(1).rstrip()
+            members = trim_private_members(r.group(1))
         #
         # Failing that, look for a straight enum
         #
@@ -822,7 +826,7 @@ class KernelDoc:
             r = KernRe(r'enum\s+(\w*)\s*\{(.*)\}')
             if r.match(proto):
                 declaration_name = r.group(1)
-                members = r.group(2).rstrip()
+                members = trim_private_members(r.group(2))
         #
         # OK, this isn't going to work.
         #