scripts: kernel-doc: make it more compatible with Sphinx 3.x

With Sphinx 3.x, the ".. c:type:" tag was changed to accept either:

	.. c:type:: typedef-like declaration
	.. c:type:: name

Using it for other types (including functions) don't work anymore.

So, there are newer tags for macro, enum, struct, union, and others,
which doesn't exist on older versions.

Add a check for the Sphinx version and change the produced tags
accordingly.
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

scripts/kernel-doc

@@ -271,6 +271,8 @@ if ($#ARGV == -1) {
 }
 
 my $kernelversion;
+my $sphinx_major;
+
 my $dohighlight = "";
 
 my $verbose = 0;
@@ -465,6 +467,43 @@ while ($ARGV[0] =~ m/^--?(.*)/) {
 
 # continue execution near EOF;
 
+# The C domain dialect changed on Sphinx 3. So, we need to check the
+# version in order to produce the right tags.
+sub findprog($)
+{
+	foreach(split(/:/, $ENV{PATH})) {
+		return "$_/$_[0]" if(-x "$_/$_[0]");
+	}
+}
+
+sub get_sphinx_version()
+{
+	my $ver;
+	my $major = 1;
+
+	my $cmd = "sphinx-build";
+	if (!findprog($cmd)) {
+		my $cmd = "sphinx-build3";
+		return $major if (!findprog($cmd));
+	}
+
+	open IN, "$cmd --version 2>&1 |";
+	while (<IN>) {
+		if (m/^\s*sphinx-build\s+([\d]+)\.([\d\.]+)(\+\/[\da-f]+)?$/) {
+			$major=$1;
+			last;
+		}
+		# Sphinx 1.2.x uses a different format
+		if (m/^\s*Sphinx.*\s+([\d]+)\.([\d\.]+)$/) {
+			$major=$1;
+			last;
+		}
+	}
+	close IN;
+
+	return $major;
+}
+
 # get kernel version from env
 sub get_kernel_version() {
     my $version = 'unknown kernel version';
@@ -848,7 +887,11 @@ sub output_function_rst(%) {
     my $start = "";
 
     if ($args{'typedef'}) {
-	print ".. c:type:: ". $args{'function'} . "\n\n";
+	if ($sphinx_major < 3) {
+	    print ".. c:type:: ". $args{'function'} . "\n\n";
+	} else {
+	    print ".. c:function:: ". $args{'function'} . "\n\n";
+	}
 	print_lineno($declaration_start_line);
 	print "   **Typedef**: ";
 	$lineprefix = "";
@@ -938,9 +981,14 @@ sub output_enum_rst(%) {
     my ($parameter);
     my $oldprefix = $lineprefix;
     my $count;
-    my $name = "enum " . $args{'enum'};
 
-    print "\n\n.. c:type:: " . $name . "\n\n";
+    if ($sphinx_major < 3) {
+	my $name = "enum " . $args{'enum'};
+	print "\n\n.. c:type:: " . $name . "\n\n";
+    } else {
+	my $name = $args{'enum'};
+	print "\n\n.. c:enum:: " . $name . "\n\n";
+    }
     print_lineno($declaration_start_line);
     $lineprefix = "   ";
     output_highlight_rst($args{'purpose'});
@@ -966,8 +1014,13 @@ sub output_typedef_rst(%) {
     my %args = %{$_[0]};
     my ($parameter);
     my $oldprefix = $lineprefix;
-    my $name = "typedef " . $args{'typedef'};
+    my $name;
 
+    if ($sphinx_major < 3) {
+	$name = "typedef " . $args{'typedef'};
+    } else {
+	$name = $args{'typedef'};
+    }
     print "\n\n.. c:type:: " . $name . "\n\n";
     print_lineno($declaration_start_line);
     $lineprefix = "   ";
@@ -982,9 +1035,14 @@ sub output_struct_rst(%) {
     my %args = %{$_[0]};
     my ($parameter);
     my $oldprefix = $lineprefix;
-    my $name = $args{'type'} . " " . $args{'struct'};
 
-    print "\n\n.. c:type:: " . $name . "\n\n";
+    if ($sphinx_major < 3) {
+	my $name = $args{'type'} . " " . $args{'struct'};
+	print "\n\n.. c:type:: " . $name . "\n\n";
+    } else {
+	my $name = $args{'struct'};
+	print "\n\n.. c:struct:: " . $name . "\n\n";
+    }
     print_lineno($declaration_start_line);
     $lineprefix = "   ";
     output_highlight_rst($args{'purpose'});
@@ -2242,6 +2300,7 @@ sub process_file($) {
 }
 
 
+$sphinx_major = get_sphinx_version();
 $kernelversion = get_kernel_version();
 
 # generate a sequence of code that will splice in highlighting information