[PATCH RFC 1/2] Kernel-doc: Convention: Use a "Return" section to describe return values

[PATCH RFC 1/2] Kernel-doc: Convention: Use a "Return" section to describe return values

[Yacine Belkadi]

Non-void functions should describe their return values in their kernel-doc
comments. Currently, some don't, others do in various forms. For example:
   * Return the result.
   * Return: The result.
   * Returns the result.
   * Returns: the result.
   * Return Value: The result.
   * @return: the result.
   * This function returns the result.
   * It will return the result.

Defining a convention would improve consistency of kernel-doc comments. It
would also help scripts/kernel-doc identify the text describing the return
value of a function. Thus allowing additional checks on the comments, and
suitable highlighting in the generated docs (man pages, html, etc).

So, as a convention, use a section named "Return" to describe the return
value of a function.

Signed-off-by: Yacine Belkadi <yacine.belkadi.1@gmail.com>
---
 Documentation/kernel-doc-nano-HOWTO.txt |   13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/Documentation/kernel-doc-nano-HOWTO.txt b/Documentation/kernel-doc-nano-HOWTO.txt
index 3d8a977..99b57ab 100644
--- a/Documentation/kernel-doc-nano-HOWTO.txt
+++ b/Documentation/kernel-doc-nano-HOWTO.txt
@@ -64,6 +64,8 @@ Example kernel-doc function comment:
  * comment lines.
  *
  * The longer description can have multiple paragraphs.
+ *
+ * Return: Describe the return value of foobar.
  */
 
 The short description following the subject can span multiple lines
@@ -78,6 +80,8 @@ If a function parameter is "..." (varargs), it should be listed in
 kernel-doc notation as:
  * @...: description
 
+The return value, if any, should be described in a dedicated section
+named "Return".
 
 Example kernel-doc data structure comment.
 
@@ -222,6 +226,9 @@ only a "*").
 "section header:" names must be unique per function (or struct,
 union, typedef, enum).
 
+Use the section header "Return" for sections describing the return value
+of a function.
+
 Avoid putting a spurious blank line after the function name, or else the
 description will be repeated!
 
@@ -237,21 +244,21 @@ patterns, which are highlighted appropriately.
 NOTE 1:  The multi-line descriptive text you provide does *not* recognize
 line breaks, so if you try to format some text nicely, as in:
 
-  Return codes
+  Return:
     0 - cool
     1 - invalid arg
     2 - out of memory
 
 this will all run together and produce:
 
-  Return codes 0 - cool 1 - invalid arg 2 - out of memory
+  Return: 0 - cool 1 - invalid arg 2 - out of memory
 
 NOTE 2:  If the descriptive text you provide has lines that begin with
 some phrase followed by a colon, each of those phrases will be taken as
 a new section heading, which means you should similarly try to avoid text
 like:
 
-  Return codes:
+  Return:
     0: cool
     1: invalid arg
     2: out of memory
-- 
1.7.9.5

[PATCH RFC 2/2] scripts/kernel-doc: check that non-void fcts describe their return value

[Yacine Belkadi]

If a function has a return value, but its kernel-doc comment doesn't contain a
"Return" section, then emit the following warning:

   Warning(file.h:129): No description found for return value of 'fct'

Note: This check emits a lot of warnings at the moment, because many functions
don't have a 'Return' doc section. So until the number of warnings goes
sufficiently down, the check is only performed in verbose mode.

Signed-off-by: Yacine Belkadi <yacine.belkadi.1@gmail.com>
---
 scripts/kernel-doc |   34 ++++++++++++++++++++++++++++++++++
 1 file changed, 34 insertions(+)

diff --git a/scripts/kernel-doc b/scripts/kernel-doc
index 8fd107a..7f82aa8 100755
--- a/scripts/kernel-doc
+++ b/scripts/kernel-doc
@@ -130,6 +130,8 @@ use strict;
 # should document the "Context:" of the function, e.g. whether the functions
 # can be called form interrupts. Unlike other sections you can end it with an
 # empty line.
+# A non-void function should have a "Return:" section describing the return
+# value.
 # Example-sections should contain the string EXAMPLE so that they are marked
 # appropriately in DocBook.
 #
@@ -298,6 +300,7 @@ my $section_default = "Description";	# default section
 my $section_intro = "Introduction";
 my $section = $section_default;
 my $section_context = "Context";
+my $section_return = "Return";
 
 my $undescribed = "-- undescribed --";
 
@@ -1767,6 +1770,28 @@ sub check_sections($$$$$$) {
 }
 
 ##
+# Checks the section describing the return value of a function.
+sub check_return_section {
+        my $file = shift;
+        my $declaration_name = shift;
+        my $return_type = shift;
+
+        # Ignore an empty return type (It's a macro)
+        # Ignore functions with a "void" return type. (But don't ignore "void *")
+        if (($return_type eq "") || ($return_type =~ /void\s*\w*\s*$/)) {
+                return;
+        }
+
+        if (!defined($sections{$section_return}) ||
+            $sections{$section_return} eq "") {
+                print STDERR "Warning(${file}:$.): " .
+                "No description found for return value of " .
+                "'$declaration_name'\n";
+                ++$warnings;
+        }
+}
+
+##
 # takes a function prototype and the name of the current file being
 # processed and spits out all the details stored in the global
 # arrays/hashes.
@@ -1837,6 +1862,15 @@ sub dump_function($$) {
 	my $prms = join " ", @parameterlist;
 	check_sections($file, $declaration_name, "function", $sectcheck, $prms, "");
 
+        # This check emits a lot of warnings at the moment, because many
+        # functions don't have a 'Return' doc section. So until the number
+        # of warnings goes sufficiently down, the check is only performed in
+        # verbose mode.
+        # TODO: always perform the check.
+        if ($verbose) {
+                check_return_section($file, $declaration_name, $return_type);
+        }
+
     output_declaration($declaration_name,
 		       'function',
 		       {'function' => $declaration_name,
-- 
1.7.9.5