doc: Cope with the deprecation of AutoReporter

AutoReporter is going away; recent versions of sphinx emit a warning like:

  Documentation/sphinx/kerneldoc.py:125:
      RemovedInSphinx20Warning: AutodocReporter is now deprecated.
      Use sphinx.util.docutils.switch_source_input() instead.

Make the switch.  But switch_source_input() only showed up in 1.7, so we
have to do ugly version checks to keep things working in older versions.

Cc: stable@vger.kernel.org
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/sphinx/kerneldoc.py

@@ -37,7 +37,17 @@ import glob
 from docutils import nodes, statemachine
 from docutils.statemachine import ViewList
 from docutils.parsers.rst import directives, Directive
-from sphinx.ext.autodoc import AutodocReporter
+
+#
+# AutodocReporter is only good up to Sphinx 1.7
+#
+import sphinx
+
+Use_SSI = sphinx.__version__[:3] >= '1.7'
+if Use_SSI:
+    from sphinx.util.docutils import switch_source_input
+else:
+    from sphinx.ext.autodoc import AutodocReporter
 
 import kernellog
 
@@ -125,13 +135,7 @@ class KernelDocDirective(Directive):
                     lineoffset += 1
 
             node = nodes.section()
-            buf = self.state.memo.title_styles, self.state.memo.section_level, self.state.memo.reporter
-            self.state.memo.reporter = AutodocReporter(result, self.state.memo.reporter)
-            self.state.memo.title_styles, self.state.memo.section_level = [], 0
-            try:
-                self.state.nested_parse(result, 0, node, match_titles=1)
-            finally:
-                self.state.memo.title_styles, self.state.memo.section_level, self.state.memo.reporter = buf
+            self.do_parse(result, node)
 
             return node.children
 
@@ -140,6 +144,20 @@ class KernelDocDirective(Directive):
                            (" ".join(cmd), str(e)))
             return [nodes.error(None, nodes.paragraph(text = "kernel-doc missing"))]
 
+    def do_parse(self, result, node):
+        if Use_SSI:
+            with switch_source_input(self.state, result):
+                self.state.nested_parse(result, 0, node, match_titles=1)
+        else:
+            save = self.state.memo.title_styles, self.state.memo.section_level, self.state.memo.reporter
+            self.state.memo.reporter = AutodocReporter(result, self.state.memo.reporter)
+            self.state.memo.title_styles, self.state.memo.section_level = [], 0
+            try:
+                self.state.nested_parse(result, 0, node, match_titles=1)
+            finally:
+                self.state.memo.title_styles, self.state.memo.section_level, self.state.memo.reporter = save
+
+
 def setup(app):
     app.add_config_value('kerneldoc_bin', None, 'env')
     app.add_config_value('kerneldoc_srctree', None, 'env')