[PATCH v3 06/33] scripts/kernel-doc.py: properly handle struct_group macros

Mauro Carvalho Chehab
2025-04-08T10:09:56Z

Handing nested parenthesis with regular expressions is not an
easy task. It is even harder with Python's re module, as it
has a limited subset of regular expressions, missing more
advanced features.

We might use instead Python regex module, but still the
regular expressions are very hard to understand. So, instead,
add a logic to properly match delimiters.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
---
scripts/kernel-doc.py | 220 ++++++++++++++++++++++++++++++++++++++++--
1 file changed, 213 insertions(+), 7 deletions(-)

diff --git a/scripts/kernel-doc.py b/scripts/kernel-doc.py
index 90808d538de7..fb96d42d287c 100755
--- a/scripts/kernel-doc.py
+++ b/scripts/kernel-doc.py
@@ -167,6 +167,172 @@ class Re:
def group(self, num):
return self.last_match.group(num)

+class NestedMatch:
+ """
+ Finding nested delimiters is hard with regular expressions. It is
+ even harder on Python with its normal re module, as there are several
+ advanced regular expressions that are missing.
+
+ This is the case of this pattern:
+
+ '\\bSTRUCT_GROUP(\\(((?:(?>[^)(]+)|(?1))*)\\))[^;]*;'
+
+ which is used to properly match open/close parenthesis of the
+ string search STRUCT_GROUP(),
+
+ Add a class that counts pairs of delimiters, using it to match and
+ replace nested expressions.
+
+ The original approach was suggested by:
+ https://stackoverflow.com/questions/5454322/python-how-to-match-nested-parentheses-with-regex
+
+ Although I re-implemented it to make it more generic and match 3 types
+ of delimiters. The logic checks if delimiters are paired. If not, it
+ will ignore the search string.
+ """
+
+ # TODO:
+ # Right now, regular expressions to match it are defined only up to
+ # the start delimiter, e.g.:
+ #
+ # \bSTRUCT_GROUP\(
+ #
+ # is similar to: STRUCT_GROUP\((.*)\)
+ # except that the content inside the match group is delimiter's aligned.
+ #
+ # The content inside parenthesis are converted into a single replace
+ # group (e.g. r`\1').
+ #
+ # It would be nice to change such definition to support multiple
+ # match groups, allowing a regex equivalent to.
+ #
+ # FOO\((.*), (.*), (.*)\)
+ #
+ # it is probably easier to define it not as a regular expression, but
+ # with some lexical definition like:
+ #
+ # FOO(arg1, arg2, arg3)
+
+
+ DELIMITER_PAIRS = {
+ '{': '}',
+ '(': ')',
+ '[': ']',
+ }
+
+ RE_DELIM = re.compile(r'[\{\}\[\]\(\)]')
+
+ def _search(self, regex, line):
+ """
+ Finds paired blocks for a regex that ends with a delimiter.
+
+ The suggestion of using finditer to match pairs came from:
+ https://stackoverflow.com/questions/5454322/python-how-to-match-nested-parentheses-with-regex
+ but I ended using a different implementation to align all three types
+ of delimiters and seek for an initial regular expression.
+
+ The algorithm seeks for open/close paired delimiters and place them
+ into a stack, yielding a start/stop position of each match when the
+ stack is zeroed.
+
+ The algorithm shoud work fine for properly paired lines, but will
+ silently ignore end delimiters that preceeds an start delimiter.
+ This should be OK for kernel-doc parser, as unaligned delimiters
+ would cause compilation errors. So, we don't need to rise exceptions
+ to cover such issues.
+ """
+
+ stack = []
+
+ for match_re in regex.finditer(line):
+ start = match_re.start()
+ offset = match_re.end()
+
+ d = line[offset -1]
+ if d not in self.DELIMITER_PAIRS:
+ continue
+
+ end = self.DELIMITER_PAIRS[d]
+ stack.append(end)
+
+ for match in self.RE_DELIM.finditer(line[offset:]):
+ pos = match.start() + offset
+
+ d = line[pos]
+
+ if d in self.DELIMITER_PAIRS:
+ end = self.DELIMITER_PAIRS[d]
+
+ stack.append(end)
+ continue
+
+ # Does the end delimiter match what it is expected?
+ if stack and d == stack[-1]:
+ stack.pop()
+
+ if not stack:
+ yield start, offset, pos + 1
+ break
+
+ def search(self, regex, line):
+ """
+ This is similar to re.search:
+
+ It matches a regex that it is followed by a delimiter,
+ returning occurrences only if all delimiters are paired.
+ """
+
+ for t in self._search(regex, line):
+
+ yield line[t[0]:t[2]]
+
+ def sub(self, regex, sub, line, count=0):
+ """
+ This is similar to re.sub:
+
+ It matches a regex that it is followed by a delimiter,
+ replacing occurrences only if all delimiters are paired.
+
+ if r'\1' is used, it works just like re: it places there the
+ matched paired data with the delimiter stripped.
+
+ If count is different than zero, it will replace at most count
+ items.
+ """
+ out = ""
+
+ cur_pos = 0
+ n = 0
+
+ found = False
+ for start, end, pos in self._search(regex, line):
+ out += line[cur_pos:start]
+
+ # Value, ignoring start/end delimiters
+ value = line[end:pos - 1]
+
+ # replaces \1 at the sub string, if \1 is used there
+ new_sub = sub
+ new_sub = new_sub.replace(r'\1', value)
+
+ out += new_sub
+
+ # Drop end ';' if any
+ if line[pos] == ';':
+ pos += 1
+
+ cur_pos = pos
+ n += 1
+
+ if count and count >= n:
+ break
+
+ # Append the remaining string
+ l = len(line)
+ out += line[cur_pos:l]
+
+ return out
+
#
# Regular expressions used to parse kernel-doc markups at KernelDoc class.
#
@@ -738,22 +904,49 @@ class KernelDoc:
(Re(r'\s*____cacheline_aligned_in_smp', re.S), ' '),
(Re(r'\s*____cacheline_aligned', re.S), ' '),

- # Unwrap struct_group() based on this definition:
+ # Unwrap struct_group macros based on this definition:
# __struct_group(TAG, NAME, ATTRS, MEMBERS...)
# which has variants like: struct_group(NAME, MEMBERS...)
+ # Only MEMBERS arguments require documentation.
+ #
+ # Parsing them happens on two steps:
+ #
+ # 1. drop struct group arguments that aren't at MEMBERS,
+ # storing them as STRUCT_GROUP(MEMBERS)
+ #
+ # 2. remove STRUCT_GROUP() ancillary macro.
+ #
+ # The original logic used to remove STRUCT_GROUP() using an
+ # advanced regex:
+ #
+ # \bSTRUCT_GROUP(\(((?:(?>[^)(]+)|(?1))*)\))[^;]*;
+ #
+ # with two patterns that are incompatible with
+ # Python re module, as it has:
+ #
+ # - a recursive pattern: (?1)
+ # - an atomic grouping: (?>...)
+ #
+ # I tried a simpler version: but it didn't work either:
+ # \bSTRUCT_GROUP\(([^\)]+)\)[^;]*;
+ #
+ # As it doesn't properly match the end parenthesis on some cases.
+ #
+ # So, a better solution was crafted: there's now a NestedMatch
+ # class that ensures that delimiters after a search are properly
+ # matched. So, the implementation to drop STRUCT_GROUP() will be
+ # handled in separate.

(Re(r'\bstruct_group\s*\(([^,]*,)', re.S), r'STRUCT_GROUP('),
(Re(r'\bstruct_group_attr\s*\(([^,]*,){2}', re.S), r'STRUCT_GROUP('),
(Re(r'\bstruct_group_tagged\s*\(([^,]*),([^,]*),', re.S), r'struct \1 \2; STRUCT_GROUP('),
(Re(r'\b__struct_group\s*\(([^,]*,){3}', re.S), r'STRUCT_GROUP('),

- # This is incompatible with Python re, as it uses:
- # recursive patterns ((?1)) and atomic grouping ((?>...)):
- # '\bSTRUCT_GROUP(\(((?:(?>[^)(]+)|(?1))*)\))[^;]*;'
- # Let's see if this works instead:
- (Re(r'\bSTRUCT_GROUP\(([^\)]+)\)[^;]*;', re.S), r'\1'),
-
# Replace macros
+ #
+ # TODO: it is better to also move those to the NestedMatch logic,
+ # to ensure that parenthesis will be properly matched.
+
(Re(r'__ETHTOOL_DECLARE_LINK_MODE_MASK\s*\(([^\)]+)\)', re.S), r'DECLARE_BITMAP(\1, __ETHTOOL_LINK_MODE_MASK_NBITS)'),
(Re(r'DECLARE_PHY_INTERFACE_MASK\s*\(([^\)]+)\)', re.S), r'DECLARE_BITMAP(\1, PHY_INTERFACE_MODE_MAX)'),
(Re(r'DECLARE_BITMAP\s*\(' + args_pattern + r',\s*' + args_pattern + r'\)', re.S), r'unsigned long \1[BITS_TO_LONGS(\2)]'),
@@ -765,9 +958,22 @@ class KernelDoc:
(Re(r'DEFINE_DMA_UNMAP_LEN\s*\(' + args_pattern + r'\)', re.S), r'__u32 \1'),
]

+ # Regexes here are guaranteed to have the end limiter matching
+ # the start delimiter. Yet, right now, only one replace group
+ # is allowed.
+
+ sub_nested_prefixes = [
+ (re.compile(r'\bSTRUCT_GROUP\('), r'\1'),
+ ]
+
for search, sub in sub_prefixes:
members = search.sub(sub, members)

+ nested = NestedMatch()
+
+ for search, sub in sub_nested_prefixes:
+ members = nested.sub(search, sub, members)
+
# Keeps the original declaration as-is
declaration = members

--
2.49.0