Merge tag 'docs-6.16' of git://git.lwn.net/linux

Pull documentation updates from Jonathan Corbet:
 "A moderately busy cycle for documentation this time around:

   - The most significant change is the replacement of the old
     kernel-doc script (a monstrous collection of Perl regexes that
     predates the Git era) with a Python reimplementation. That, too, is
     a horrifying collection of regexes, but in a much cleaner and more
     maintainable structure that integrates far better with the Sphinx
     build system.

     This change has been in linux-next for the full 6.15 cycle; the
     small number of problems that turned up have been addressed,
     seemingly to everybody's satisfaction. The Perl kernel-doc script
     remains in tree (as scripts/kernel-doc.pl) and can be used with a
     command-line option if need be. Unless some reason to keep it
     around materializes, it will probably go away in 6.17.

     Credit goes to Mauro Carvalho Chehab for doing all this work.

   - Some RTLA documentation updates

   - A handful of Chinese translations

   - The usual collection of typo fixes, general updates, etc"

* tag 'docs-6.16' of git://git.lwn.net/linux: (85 commits)
  Docs: doc-guide: update sphinx.rst Sphinx version number
  docs: doc-guide: clarify latest theme usage
  Documentation/scheduler: Fix typo in sched-stats domain field description
  scripts: kernel-doc: prevent a KeyError when checking output
  docs: kerneldoc.py: simplify exception handling logic
  MAINTAINERS: update linux-doc entry to cover new Python scripts
  docs: align with scripts/syscall.tbl migration
  Documentation: NTB: Fix typo
  Documentation: ioctl-number: Update table intro
  docs: conf.py: drop backward support for old Sphinx versions
  Docs: driver-api/basics: add kobject_event interfaces
  Docs: relay: editing cleanups
  docs: fix "incase" typo in coresight/panic.rst
  Fix spelling error for 'parallel'
  docs: admin-guide: fix typos in reporting-issues.rst
  docs: dmaengine: add explanation for DMA_ASYNC_TX capability
  Documentation: leds: improve readibility of multicolor doc
  docs: fix typo in firmware-related section
  docs: Makefile: Inherit PYTHONPYCACHEPREFIX setting as env variable
  Documentation: ioctl-number: Update outdated submission info
  ...

1 files changed, 273 insertions, 0 deletions

diff --git a/scripts/lib/kdoc/kdoc_re.py b/scripts/lib/kdoc/kdoc_re.py
new file mode 100644
index 000000000000..e81695b273bf
--- /dev/null
+++ b/scripts/lib/kdoc/kdoc_re.py
@@ -0,0 +1,273 @@
+#!/usr/bin/env python3
+# SPDX-License-Identifier: GPL-2.0
+# Copyright(c) 2025: Mauro Carvalho Chehab <mchehab@kernel.org>.
+
+"""
+Regular expression ancillary classes.
+
+Those help caching regular expressions and do matching for kernel-doc.
+"""
+
+import re
+
+# Local cache for regular expressions
+re_cache = {}
+
+
+class KernRe:
+    """
+    Helper class to simplify regex declaration and usage,
+
+    It calls re.compile for a given pattern. It also allows adding
+    regular expressions and define sub at class init time.
+
+    Regular expressions can be cached via an argument, helping to speedup
+    searches.
+    """
+
+    def _add_regex(self, string, flags):
+        """
+        Adds a new regex or re-use it from the cache.
+        """
+
+        if string in re_cache:
+            self.regex = re_cache[string]
+        else:
+            self.regex = re.compile(string, flags=flags)
+
+            if self.cache:
+                re_cache[string] = self.regex
+
+    def __init__(self, string, cache=True, flags=0):
+        """
+        Compile a regular expression and initialize internal vars.
+        """
+
+        self.cache = cache
+        self.last_match = None
+
+        self._add_regex(string, flags)
+
+    def __str__(self):
+        """
+        Return the regular expression pattern.
+        """
+        return self.regex.pattern
+
+    def __add__(self, other):
+        """
+        Allows adding two regular expressions into one.
+        """
+
+        return KernRe(str(self) + str(other), cache=self.cache or other.cache,
+                  flags=self.regex.flags | other.regex.flags)
+
+    def match(self, string):
+        """
+        Handles a re.match storing its results
+        """
+
+        self.last_match = self.regex.match(string)
+        return self.last_match
+
+    def search(self, string):
+        """
+        Handles a re.search storing its results
+        """
+
+        self.last_match = self.regex.search(string)
+        return self.last_match
+
+    def findall(self, string):
+        """
+        Alias to re.findall
+        """
+
+        return self.regex.findall(string)
+
+    def split(self, string):
+        """
+        Alias to re.split
+        """
+
+        return self.regex.split(string)
+
+    def sub(self, sub, string, count=0):
+        """
+        Alias to re.sub
+        """
+
+        return self.regex.sub(sub, string, count=count)
+
+    def group(self, num):
+        """
+        Returns the group results of the last match
+        """
+
+        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: make NestedMatch handle multiple match groups
+    #
+    # 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
+
+        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