add a make target to generate man pages from kernel-doc

Hi Jon,

Please ingore the first version. It was done on the top of a past implementation. That's the right one ;-)

Currently, generation of manpages is hacky: one needs to run kernel-doc over c source files and then use an extra script to split results.

The new kernel-doc tool supports multiple files and even dirs, so there's no need to use git ls-files anymore.

Yet, it produces a single output. Change the logic to add, instead a target to docs Makefile to produce them, moving the split and build logic to sphinx-build-wrapper.

That allows honoring SPHINXDIRS when they point to a subdir, while scanning all files by default.

This series comes after:

    https://lore.kernel.org/linux-doc/[email protected]/T/#t

-

It should be noticed that, while Sphinx does have a man pages builder, it requires a completely different set of ReST entries that would need to be designed specially for that:

- for each man page, an entry at conf.py is required;
- the ReST page should be in a format closer to a real man page.

This is completely different from the approach we take where we have, where kernel-doc direcly generates groff output formated data.

So, yeah, this is still a little bit hackish, but to avoid that we would need a completely different setup with, frankly, would be a headache to setup and maintain.

With that in mind, there are a couple of possible alternatives:

1. change kernel-doc to produce one file per man page;
2. make sphinx-build-wrapper do that for us;
3. have a man pages Sphinx extension that would be filling man_pages and calling kernel-doc in the background.

(3) is probably doable, and could eventually bring some advantages, as we could have man pages for pages that are only in ReST format, but it will require some extra development. Not sure if it worth the efforts.

I opted for (2), as it means that ones needing to generate docs can benefit from SPHINXDIRS. By doing that, we can later improve the man pages logic without needing to touch anything else.

There are two points to consider:

- when SPHINXDIRS=. (the default), it searches fror all files treewide, which is aligned with the procedure defined at the current documentation;

- when SHINXDIRS=subdirs, it searches only for the files that come just after kernel-doc, excluding the files and filter logic that could be just at the at the kernel-doc options.

---

v2:
- no actual changes, but it was rebased on the top of the actual pacth series, in order to apply cleanly.

Mauro Carvalho Chehab (1):
docs: add support to build manpages from kerneldoc output

 Documentation/Makefile                 |  3 +-
 Documentation/doc-guide/kernel-doc.rst | 19 ++-----
 Makefile                               |  2 +-
 scripts/split-man.pl                   | 28 ---------
 tools/docs/sphinx-build-wrapper        | 78 ++++++++++++++++++++++++--
 5 files changed, 81 insertions(+), 49 deletions(-)
 delete mode 100755 scripts/split-man.pl

2.51.0

Generating man files currently requires running a separate script. The target also doesn't appear at the docs Makefile.

Add support for mandocs at the Makefile, adding the build logic inside sphinx-build-wrapper, updating documentation and dropping the ancillary script.

---
 Documentation/Makefile                 |  3 +-
 Documentation/doc-guide/kernel-doc.rst | 19 ++-----
 Makefile                               |  2 +-
 scripts/split-man.pl                   | 28 ---------
 tools/docs/sphinx-build-wrapper        | 78 ++++++++++++++++++++++++--
 5 files changed, 81 insertions(+), 49 deletions(-)
 delete mode 100755 scripts/split-man.pl

index 3e1cb44a5fbb..22e39e5ed07d 100644
@@ -53,7 +53,7 @@ ifeq ($(HAVE_SPHINX),0)
 else # HAVE_SPHINX
 
 # Common documentation targets
-infodocs texinfodocs latexdocs epubdocs xmldocs pdfdocs linkcheckdocs:
+mandocs infodocs texinfodocs latexdocs epubdocs xmldocs pdfdocs linkcheckdocs:
 	$(Q)@$(srctree)/tools/docs/sphinx-pre-install --version-check
 	+$(Q)$(PYTHON3) $(BUILD_WRAPPER) $@ \
 		--sphinxdirs="$(SPHINXDIRS)" --conf=$(SPHINX_CONF) \

@@ -104,6 +104,7 @@ dochelp:
 	@echo  '  htmldocs        - HTML'
 	@echo  '  texinfodocs     - Texinfo'
 	@echo  '  infodocs        - Info'
+	@echo  '  mandocs         - Man pages'
 	@echo  '  latexdocs       - LaTeX'
 	@echo  '  pdfdocs         - PDF'
 	@echo  '  epubdocs        - EPUB'

index af9697e60165..d85dcb08c87d 100644
@@ -579,20 +579,9 @@ source.
 How to use kernel-doc to generate man pages
 -------------------------------------------
 
-If you just want to use kernel-doc to generate man pages you can do this
-from the kernel git tree::
+Generating man pages is a makefile target. Just run::
 
-  $ scripts/kernel-doc -man \
-    $(git grep -l '/\*\*' -- :^Documentation :^tools) \
-    | scripts/split-man.pl /tmp/man
+  $ make mandocs
 
-Some older versions of git do not support some of the variants of syntax for
-path exclusion.  One of the following commands may work for those versions::
-
-  $ scripts/kernel-doc -man \
-    $(git grep -l '/\*\*' -- . ':!Documentation' ':!tools') \
-    | scripts/split-man.pl /tmp/man
-
-  $ scripts/kernel-doc -man \
-    $(git grep -l '/\*\*' -- . ":(exclude)Documentation" ":(exclude)tools") \
-    | scripts/split-man.pl /tmp/man
+The output will be at ``/man`` directory inside the output directory
+(by default: ``Documentation/output``).

index 6bfe776bf3c5..9bd44afeda26 100644
@@ -1800,7 +1800,7 @@ $(help-board-dirs): help-%:
 # Documentation targets
 # ---------------------------------------------------------------------------
 DOC_TARGETS := xmldocs latexdocs pdfdocs htmldocs epubdocs cleandocs \
-	       linkcheckdocs dochelp refcheckdocs texinfodocs infodocs
+	       linkcheckdocs dochelp refcheckdocs texinfodocs infodocs mandocs
 PHONY += $(DOC_TARGETS)
 $(DOC_TARGETS):
 	$(Q)$(MAKE) $(build)=Documentation $@

deleted file mode 100755
index 96bd99dc977a..000000000000
@@ -1,28 +0,0 @@
-#!/usr/bin/env perl
-# SPDX-License-Identifier: GPL-2.0
-#
-# Author: Mauro Carvalho Chehab <[email protected]>
-#
-# Produce manpages from kernel-doc.
-# See Documentation/doc-guide/kernel-doc.rst for instructions
-
-if ($#ARGV < 0) {
-   die "where do I put the results?\n";
-}
-
-mkdir $ARGV[0],0777;
-$state = 0;
-while (<STDIN>) {
-    if (/^\.TH \"[^\"]*\" 9 \"([^\"]*)\"/) {
-	if ($state == 1) { close OUT }
-	$state = 1;
-	$fn = "$ARGV[0]/$1.9";
-	print STDERR "Creating $fn\n";
-	open OUT, ">$fn" or die "can't open $fn: $!\n";
-	print OUT $_;
-    } elsif ($state != 0) {
-	print OUT $_;
-    }
-}
-
-close OUT;

2.51.0