Docs: An initial automarkup extension for sphinx

# Add any Sphinx extension module names here, as strings. They can be

# extensions coming with Sphinx (named 'sphinx.ext.*') or your custom

# ones.

extensions = ['kerneldoc', 'rstFlatTable', 'kernel_include', 'cdomain', 'kfigure', 'sphinx.ext.ifconfig']

extensions = ['kerneldoc', 'rstFlatTable', 'kernel_include', 'cdomain',

              'kfigure', 'sphinx.ext.ifconfig', 'automarkup']

# The name of the math extension changed on Sphinx 1.4

if (major == 1 and minor > 3) or (major > 1):

# SPDX-License-Identifier: GPL-2.0

# Copyright 2019 Jonathan Corbet <corbet@lwn.net>

#

# Apply kernel-specific tweaks after the initial document processing

# has been done.

#

from docutils import nodes

from sphinx import addnodes

import re

#

# Regex nastiness.  Of course.

# Try to identify "function()" that's not already marked up some

# other way.  Sphinx doesn't like a lot of stuff right after a

# :c:func: block (i.e. ":c:func:`mmap()`s" flakes out), so the last

# bit tries to restrict matches to things that won't create trouble.

#

RE_function = re.compile(r'([\w_][\w\d_]+\(\))')

#

# Many places in the docs refer to common system calls.  It is

# pointless to try to cross-reference them and, as has been known

# to happen, somebody defining a function by these names can lead

# to the creation of incorrect and confusing cross references.  So

# just don't even try with these names.

#

Skipfuncs = [ 'open', 'close', 'read', 'write', 'fcntl', 'mmap'

              'select', 'poll', 'fork', 'execve', 'clone', 'ioctl']

#

# Find all occurrences of function() and try to replace them with

# appropriate cross references.

#

def markup_funcs(docname, app, node):

    cdom = app.env.domains['c']

    t = node.astext()

    done = 0

    repl = [ ]

    for m in RE_function.finditer(t):

        #

        # Include any text prior to function() as a normal text node.

        #

        if m.start() > done:

            repl.append(nodes.Text(t[done:m.start()]))

        #

        # Go through the dance of getting an xref out of the C domain

        #

        target = m.group(1)[:-2]

        target_text = nodes.Text(target + '()')

        xref = None

        if target not in Skipfuncs:

            lit_text = nodes.literal(classes=['xref', 'c', 'c-func'])

            lit_text += target_text

            pxref = addnodes.pending_xref('', refdomain = 'c',

                                          reftype = 'function',

                                          reftarget = target, modname = None,

                                          classname = None)

            xref = cdom.resolve_xref(app.env, docname, app.builder,

                                     'function', target, pxref, lit_text)

        #

        # Toss the xref into the list if we got it; otherwise just put

        # the function text.

        #

        if xref:

            repl.append(xref)

        else:

            repl.append(target_text)

        done = m.end()

    if done < len(t):

        repl.append(nodes.Text(t[done:]))

    return repl

def auto_markup(app, doctree, name):

    #

    # This loop could eventually be improved on.  Someday maybe we

    # want a proper tree traversal with a lot of awareness of which

    # kinds of nodes to prune.  But this works well for now.

    #

    # The nodes.literal test catches ``literal text``, its purpose is to

    # avoid adding cross-references to functions that have been explicitly

    # marked with cc:func:.

    #

    for para in doctree.traverse(nodes.paragraph):

        for node in para.traverse(nodes.Text):

            if not isinstance(node.parent, nodes.literal):

                node.parent.replace(node, markup_funcs(name, app, node))

def setup(app):

    app.connect('doctree-resolved', auto_markup)

    return {

        'parallel_read_safe': True,

        'parallel_write_safe': True,

        }