Documentation/sphinx: add Sphinx kernel-doc directive extension

Add an extension to handle kernel-doc directives, to call kernel-doc
according to the arguments and parameters given to the reStructuredText
directive.

The syntax for the kernel-doc directive is:

.. kernel-doc:: FILENAME
   :export:
   :internal:
   :functions: FUNCTION [FUNCTION ...]
   :doc: SECTION TITLE

Of the directive options export, internal, functions, and doc, currently
only one option may be given at a time.

The FILENAME is relative from the kernel source tree root.

The extension notifies Sphinx about the document dependency on FILENAME,
causing the document to be rebuilt when the file has been changed.
Signed-off-by: NJani Nikula <jani.nikula@intel.com>

Documentation/sphinx/kernel-doc.py

+# coding=utf-8
+#
+# Copyright © 2016 Intel Corporation
+#
+# Permission is hereby granted, free of charge, to any person obtaining a
+# copy of this software and associated documentation files (the "Software"),
+# to deal in the Software without restriction, including without limitation
+# the rights to use, copy, modify, merge, publish, distribute, sublicense,
+# and/or sell copies of the Software, and to permit persons to whom the
+# Software is furnished to do so, subject to the following conditions:
+#
+# The above copyright notice and this permission notice (including the next
+# paragraph) shall be included in all copies or substantial portions of the
+# Software.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+# THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+# FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+# IN THE SOFTWARE.
+#
+# Authors:
+#    Jani Nikula <jani.nikula@intel.com>
+
+import os
+import subprocess
+import sys
+
+from docutils import nodes, statemachine
+from docutils.parsers.rst import directives
+from sphinx.util.compat import Directive
+
+class KernelDocDirective(Directive):
+    """Extract kernel-doc comments from the specified file"""
+    required_argument = 1
+    optional_arguments = 4
+    option_spec = {
+        'doc': directives.unchanged_required,
+        'functions': directives.unchanged_required,
+        'export': directives.flag,
+        'internal': directives.flag,
+    }
+    has_content = False
+
+    def run(self):
+        env = self.state.document.settings.env
+        cmd = [env.config.kerneldoc_bin, '-rst']
+
+        filename = env.config.kerneldoc_srctree + '/' + self.arguments[0]
+
+        # Tell sphinx of the dependency
+        env.note_dependency(os.path.abspath(filename))
+
+        tab_width = self.options.get('tab-width', self.state.document.settings.tab_width)
+        source = self.state_machine.input_lines.source(self.lineno - self.state_machine.input_offset - 1)
+
+        # FIXME: make this nicer and more robust against errors
+        if 'export' in self.options:
+            cmd += ['-export']
+        elif 'internal' in self.options:
+            cmd += ['-internal']
+        elif 'doc' in self.options:
+            cmd += ['-function', str(self.options.get('doc'))]
+        elif 'functions' in self.options:
+            for f in str(self.options.get('functions')).split(' '):
+                cmd += ['-function', f]
+
+        cmd += [filename]
+
+        try:
+            env.app.verbose('calling kernel-doc \'%s\'' % (" ".join(cmd)))
+
+            p = subprocess.Popen(cmd, stdout=subprocess.PIPE, stderr=subprocess.PIPE, universal_newlines=True)
+            out, err = p.communicate()
+
+            # assume the kernel sources are utf-8
+            out, err = unicode(out, 'utf-8'), unicode(err, 'utf-8')
+
+            if p.returncode != 0:
+                sys.stderr.write(err)
+
+                env.app.warn('kernel-doc \'%s\' failed with return code %d' % (" ".join(cmd), p.returncode))
+                return [nodes.error(None, nodes.paragraph(text = "kernel-doc missing"))]
+            elif env.config.kerneldoc_verbosity > 0:
+                sys.stderr.write(err)
+
+            lines = statemachine.string2lines(out, tab_width, convert_whitespace=True)
+            self.state_machine.insert_input(lines, source)
+            return []
+        except Exception as e:
+            env.app.warn('kernel-doc \'%s\' processing failed with: %s' %
+                         (" ".join(cmd), str(e)))
+            return [nodes.error(None, nodes.paragraph(text = "kernel-doc missing"))]
+
+def setup(app):
+    app.add_config_value('kerneldoc_bin', None, 'env')
+    app.add_config_value('kerneldoc_srctree', None, 'env')
+    app.add_config_value('kerneldoc_verbosity', 1, 'env')
+
+    app.add_directive('kernel-doc', KernelDocDirective)