scripts: kernel-doc: parse next structs/unions

There are several places within the Kernel tree with nested
structs/unions, like this one:

  struct ingenic_cgu_clk_info {
    const char *name;
    enum {
      CGU_CLK_NONE = 0,
      CGU_CLK_EXT = BIT(0),
      CGU_CLK_PLL = BIT(1),
      CGU_CLK_GATE = BIT(2),
      CGU_CLK_MUX = BIT(3),
      CGU_CLK_MUX_GLITCHFREE = BIT(4),
      CGU_CLK_DIV = BIT(5),
      CGU_CLK_FIXDIV = BIT(6),
      CGU_CLK_CUSTOM = BIT(7),
    } type;
    int parents[4];
    union {
      struct ingenic_cgu_pll_info pll;
      struct {
        struct ingenic_cgu_gate_info gate;
        struct ingenic_cgu_mux_info mux;
        struct ingenic_cgu_div_info div;
        struct ingenic_cgu_fixdiv_info fixdiv;
      };
      struct ingenic_cgu_custom_info custom;
    };
  };

Currently, such struct is documented as:

	**Definition**

	::
	struct ingenic_cgu_clk_info {
	    const char * name;
	};

	**Members**

	``name``
	  name of the clock

With is obvioulsy wrong. It also generates an error:
	drivers/clk/ingenic/cgu.h:169: warning: No description found for parameter 'enum'

However, there's nothing wrong with this kernel-doc markup: everything
is documented there.

It makes sense to document all fields there. So, add a
way for the core to parse those structs.

With this patch, all documented fields will properly generate
documentation.

Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/doc-guide/kernel-doc.rst

@@ -281,6 +281,52 @@ comment block.
 The kernel-doc data structure comments describe each member of the structure,
 in order, with the member descriptions.
 
+Nested structs/unions
+~~~~~~~~~~~~~~~~~~~~~
+
+It is possible to document nested structs unions, like::
+
+      /**
+       * struct nested_foobar - a struct with nested unions and structs
+       * @arg1: - first argument of anonymous union/anonymous struct
+       * @arg2: - second argument of anonymous union/anonymous struct
+       * @arg3: - third argument of anonymous union/anonymous struct
+       * @arg4: - fourth argument of anonymous union/anonymous struct
+       * @bar.st1.arg1 - first argument of struct st1 on union bar
+       * @bar.st1.arg2 - second argument of struct st1 on union bar
+       * @bar.st2.arg1 - first argument of struct st2 on union bar
+       * @bar.st2.arg2 - second argument of struct st2 on union bar
+      struct nested_foobar {
+        /* Anonymous union/struct*/
+        union {
+          struct {
+            int arg1;
+            int arg2;
+	  }
+          struct {
+            void *arg3;
+            int arg4;
+	  }
+	}
+	union {
+          struct {
+            int arg1;
+            int arg2;
+	  } st1;
+          struct {
+            void *arg1;
+            int arg2;
+	  } st2;
+	} bar;
+      };
+
+.. note::
+
+   #) When documenting nested structs or unions, if the struct/union ``foo``
+      is named, the argument ``bar`` inside it should be documented as
+      ``@foo.bar:``
+   #) When the nested struct/union is anonymous, the argument ``bar`` on it
+      should be documented as ``@bar:``
 
 Typedef documentation
 ---------------------

scripts/kernel-doc

@@ -211,7 +211,7 @@ my $anon_struct_union = 0;
 my $type_constant = '\b``([^\`]+)``\b';
 my $type_constant2 = '\%([-_\w]+)';
 my $type_func = '(\w+)\(\)';
-my $type_param = '\@(\w+(\.\.\.)?)';
+my $type_param = '\@(\w*(\.\w+)*(\.\.\.)?)';
 my $type_fp_param = '\@(\w+)\(\)';  # Special RST handling for func ptr params
 my $type_env = '(\$\w+)';
 my $type_enum = '\&(enum\s*([_\w]+))';
@@ -670,32 +670,12 @@ sub output_struct_man(%) {
     print ".SH NAME\n";
     print $args{'type'} . " " . $args{'struct'} . " \\- " . $args{'purpose'} . "\n";
 
+    my $declaration = $args{'definition'};
+    $declaration =~ s/\t/  /g;
+    $declaration =~ s/\n/"\n.br\n.BI \"/g;
     print ".SH SYNOPSIS\n";
     print $args{'type'} . " " . $args{'struct'} . " {\n.br\n";
-
-    foreach my $parameter (@{$args{'parameterlist'}}) {
-	if ($parameter =~ /^#/) {
-	    print ".BI \"$parameter\"\n.br\n";
-	    next;
-	}
-	my $parameter_name = $parameter;
-	$parameter_name =~ s/\[.*//;
-
-	($args{'parameterdescs'}{$parameter_name} ne $undescribed) || next;
-	$type = $args{'parametertypes'}{$parameter};
-	if ($type =~ m/([^\(]*\(\*)\s*\)\s*\(([^\)]*)\)/) {
-	    # pointer-to-function
-	    print ".BI \"    " . $1 . "\" " . $parameter . " \") (" . $2 . ")" . "\"\n;\n";
-	} elsif ($type =~ m/^(.*?)\s*(:.*)/) {
-	    # bitfield
-	    print ".BI \"    " . $1 . "\ \" " . $parameter . $2 . " \"" . "\"\n;\n";
-	} else {
-	    $type =~ s/([^\*])$/$1 /;
-	    print ".BI \"    " . $type . "\" " . $parameter . " \"" . "\"\n;\n";
-	}
-	print "\n.br\n";
-    }
-    print "};\n.br\n";
+    print ".BI \"$declaration\n};\n.br\n\n";
 
     print ".SH Members\n";
     foreach $parameter (@{$args{'parameterlist'}}) {
@@ -933,29 +913,9 @@ sub output_struct_rst(%) {
 
     print "**Definition**\n\n";
     print "::\n\n";
-    print "  " . $args{'type'} . " " . $args{'struct'} . " {\n";
-    foreach $parameter (@{$args{'parameterlist'}}) {
-	if ($parameter =~ /^#/) {
-	    print "  " . "$parameter\n";
-	    next;
-	}
-
-	my $parameter_name = $parameter;
-	$parameter_name =~ s/\[.*//;
-
-	($args{'parameterdescs'}{$parameter_name} ne $undescribed) || next;
-	$type = $args{'parametertypes'}{$parameter};
-	if ($type =~ m/([^\(]*\(\*)\s*\)\s*\(([^\)]*)\)/) {
-	    # pointer-to-function
-	    print "    $1 $parameter) ($2);\n";
-	} elsif ($type =~ m/^(.*?)\s*(:.*)/) {
-	    # bitfield
-	    print "    $1 $parameter$2;\n";
-	} else {
-	    print "    " . $type . " " . $parameter . ";\n";
-	}
-    }
-    print "  };\n\n";
+    my $declaration = $args{'definition'};
+    $declaration =~ s/\t/  /g;
+    print "  " . $args{'type'} . " " . $args{'struct'} . " {\n$declaration  };\n\n";
 
     print "**Members**\n\n";
     $lineprefix = "  ";
@@ -1050,16 +1010,11 @@ sub dump_struct($$) {
 	$declaration_name = $2;
 	my $members = $3;
 
-	# ignore embedded structs or unions
-	$members =~ s/({.*})//g;
-	$nested = $1;
-
 	# ignore members marked private:
 	$members =~ s/\/\*\s*private:.*?\/\*\s*public:.*?\*\///gosi;
 	$members =~ s/\/\*\s*private:.*//gosi;
 	# strip comments:
 	$members =~ s/\/\*.*?\*\///gos;
-	$nested =~ s/\/\*.*?\*\///gos;
 	# strip attributes
 	$members =~ s/__attribute__\s*\(\([a-z,_\*\s\(\)]*\)\)//i;
 	$members =~ s/__aligned\s*\([^;]*\)//gos;
@@ -1073,13 +1028,73 @@ sub dump_struct($$) {
 	# replace DECLARE_KFIFO_PTR
 	$members =~ s/DECLARE_KFIFO_PTR\s*\(([^,)]+),\s*([^,)]+)\)/$2 \*$1/gos;
 
+	my $declaration = $members;
+
+	# Split nested struct/union elements as newer ones
+	my $cont = 1;
+	while ($cont) {
+		$cont = 0;
+		while ($members =~ m/(struct|union)([^{};]+){([^{}]*)}([^{}\;]*)\;/) {
+			my $newmember = "$1 $4;";
+			my $id = $4;
+			my $content = $3;
+			$id =~ s/[:\[].*//;
+			$id =~ s/^\*+//;
+			foreach my $arg (split /;/, $content) {
+				next if ($arg =~ m/^\s*$/);
+				my $type = $arg;
+				my $name = $arg;
+				$type =~ s/\s\S+$//;
+				$name =~ s/.*\s//;
+				$name =~ s/[:\[].*//;
+				$name =~ s/^\*+//;
+				next if (($name =~ m/^\s*$/));
+				if ($id =~ m/^\s*$/) {
+					# anonymous struct/union
+					$newmember .= "$type $name;";
+				} else {
+					$newmember .= "$type $id.$name;";
+				}
+			}
+			$members =~ s/(struct|union)([^{};]+){([^{}]*)}([^{}\;]*)\;/$newmember/;
+			$cont = 1;
+		};
+	};
+
+	# Ignore other nested elements, like enums
+	$members =~ s/({[^\{\}]*})//g;
+	$nested = $decl_type;
+	$nested =~ s/\/\*.*?\*\///gos;
+
 	create_parameterlist($members, ';', $file);
 	check_sections($file, $declaration_name, $decl_type, $sectcheck, $struct_actual, $nested);
 
+	# Adjust declaration for better display
+	$declaration =~ s/([{;])/$1\n/g;
+	$declaration =~ s/}\s+;/};/g;
+	# Better handle inlined enums
+	do {} while ($declaration =~ s/(enum\s+{[^}]+),([^\n])/$1,\n$2/);
+
+	my @def_args = split /\n/, $declaration;
+	my $level = 1;
+	$declaration = "";
+	foreach my $clause (@def_args) {
+		$clause =~ s/^\s+//;
+		$clause =~ s/\s+$//;
+		$clause =~ s/\s+/ /;
+		next if (!$clause);
+		$level-- if ($clause =~ m/(})/ && $level > 1);
+		if (!($clause =~ m/^\s*#/)) {
+			$declaration .= "\t" x $level;
+		}
+		$declaration .= "\t" . $clause . "\n";
+		$level++ if ($clause =~ m/({)/ && !($clause =~m/}/));
+	}
 	output_declaration($declaration_name,
 			   'struct',
 			   {'struct' => $declaration_name,
 			    'module' => $modulename,
+			    'definition' => $declaration,
 			    'parameterlist' => \@parameterlist,
 			    'parameterdescs' => \%parameterdescs,
 			    'parametertypes' => \%parametertypes,