perf Documentation: Support for asciidoctor

The asciidoc package seems behind the recent big wave of python3
conversion, and we were advised to switch to asciidoctor instead. It's
almost compatible but some extensions used for perf documentation don't
work with it. Here is the patch to cover them, and add the proper
support for asciidoctor.

Pass USE_ASCIIDOCTOR=yes to make for using asciidoctor instead of
asciidoc. The man source and manual attributes are passed via command
options. The support for these attributes have been fixed in the
latest asciidoctor code.

Since asciidoctor can covert to a man page and an HTML directly, we
can omit the dependency on xmlto when USE_ASCIIDOCTOR is set.

Signed-off-by: Takashi Iwai <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/Documentation/Makefile

···
 man7dir=$(mandir)/man7
 
 ASCIIDOC=asciidoc
-ASCIIDOC_EXTRA = --unsafe
+ASCIIDOC_EXTRA = --unsafe -f asciidoc.conf
+ASCIIDOC_HTML = xhtml11
 MANPAGE_XSL = manpage-normal.xsl
 XMLTO_EXTRA =
 INSTALL?=install
 RM ?= rm -f
 DOC_REF = origin/man
 HTML_REF = origin/html
+
+ifdef USE_ASCIIDOCTOR
+ASCIIDOC = asciidoctor
+ASCIIDOC_EXTRA = -a compat-mode
+ASCIIDOC_EXTRA += -I. -rasciidoctor-extensions
+ASCIIDOC_EXTRA += -a mansource="perf" -a manmanual="perf Manual"
+ASCIIDOC_HTML = xhtml5
+endif
 
 infodir?=$(prefix)/share/info
 MAKEINFO=makeinfo
···
 	missing_tools = $(ASCIIDOC)
 endif
 
+ifndef USE_ASCIIDOCTOR
 _tmp_tool_path := $(call get-executable,$(XMLTO))
 ifeq ($(_tmp_tool_path),)
 	missing_tools += $(XMLTO)
+endif
 endif
 
 #
···
 
 $(MAN_HTML): $(OUTPUT)%.html : %.txt
 	$(QUIET_ASCIIDOC)$(RM) $@+ $@ && \
-	$(ASCIIDOC) -b xhtml11 -d manpage -f asciidoc.conf \
+	$(ASCIIDOC) -b $(ASCIIDOC_HTML) -d manpage \
 		$(ASCIIDOC_EXTRA) -aperf_version=$(PERF_VERSION) -o $@+ $< && \
 	mv $@+ $@
+
+ifdef USE_ASCIIDOCTOR
+$(OUTPUT)%.1 $(OUTPUT)%.5 $(OUTPUT)%.7 : $(OUTPUT)%.txt
+	$(QUIET_ASCIIDOC)$(RM) $@+ $@ && \
+	$(ASCIIDOC) -b manpage -d manpage \
+		$(ASCIIDOC_EXTRA) -aperf_version=$(PERF_VERSION) -o $@+ $< && \
+	mv $@+ $@
+endif
 
 $(OUTPUT)%.1 $(OUTPUT)%.5 $(OUTPUT)%.7 : $(OUTPUT)%.xml
 	$(QUIET_XMLTO)$(RM) $@ && \
···
 
 $(OUTPUT)%.xml : %.txt
 	$(QUIET_ASCIIDOC)$(RM) $@+ $@ && \
-	$(ASCIIDOC) -b docbook -d manpage -f asciidoc.conf \
+	$(ASCIIDOC) -b docbook -d manpage \
 		$(ASCIIDOC_EXTRA) -aperf_version=$(PERF_VERSION) -o $@+ $< && \
 	mv $@+ $@
 
···
 	mv $@+ $@
 
 $(patsubst %,%.html,$(ARTICLES)) : %.html : %.txt
-	$(QUIET_ASCIIDOC)$(ASCIIDOC) -b xhtml11 $*.txt
+	$(QUIET_ASCIIDOC)$(ASCIIDOC) -b $(ASCIIDOC_HTML) $*.txt
 
 WEBDOC_DEST = /pub/software/tools/perf/docs
 
 $(patsubst %.txt,%.html,$(wildcard howto/*.txt)): %.html : %.txt
 	$(QUIET_ASCIIDOC)$(RM) $@+ $@ && \
-	sed -e '1,/^$$/d' $< | $(ASCIIDOC) -b xhtml11 - >$@+ && \
+	sed -e '1,/^$$/d' $< | $(ASCIIDOC) -b $(ASCIIDOC_HTML) - >$@+ && \
 	mv $@+ $@
 
 # UNIMPLEMENTED

tools/perf/Documentation/asciidoctor-extensions.rb

···
+require 'asciidoctor'
+require 'asciidoctor/extensions'
+
+module Perf
+  module Documentation
+    class LinkPerfProcessor < Asciidoctor::Extensions::InlineMacroProcessor
+      use_dsl
+
+      named :chrome
+
+      def process(parent, target, attrs)
+        if parent.document.basebackend? 'html'
+          %(<a href="#{target}.html">#{target}(#{attrs[1]})</a>\n)
+        elsif parent.document.basebackend? 'manpage'
+          "#{target}(#{attrs[1]})"
+        elsif parent.document.basebackend? 'docbook'
+          "<citerefentry>\n" \
+            "<refentrytitle>#{target}</refentrytitle>" \
+            "<manvolnum>#{attrs[1]}</manvolnum>\n" \
+          "</citerefentry>\n"
+        end
+      end
+    end
+  end
+end
+
+Asciidoctor::Extensions.register do
+  inline_macro Perf::Documentation::LinkPerfProcessor, :linkperf
+end