Makefile, configure: Support building rST documentation

Add support to our configure and makefile machinery for building
our rST docs into HTML files.

Building the documentation now requires that sphinx-build is
available; this seems better than allowing half the docs to
be built if it is not present but having half of them missing.
(In particular it means that assuming that distros configured with
--enable-docs they'll get a helpful error from configure telling
them the new build dependency.)

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Tested-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Acked-by: Aleksandar Markovic <amarkovic@wavecomp.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20190305172139.32662-10-peter.maydell@linaro.org
Message-id: 20190228145624.24885-10-peter.maydell@linaro.org

.gitignore

@@ -1,3 +1,4 @@
+/.doctrees
 /config-devices.*
 /config-all-devices.*
 /config-all-disas.*

Makefile

@@ -388,7 +388,7 @@ dummy := $(call unnest-vars,, \
 
 include $(SRC_PATH)/tests/Makefile.include
 
-all: $(DOCS) $(TOOLS) $(HELPERS-y) recurse-all modules
+all: $(DOCS) $(if $(BUILD_DOCS),sphinxdocs) $(TOOLS) $(HELPERS-y) recurse-all modules
 
 qemu-version.h: FORCE
 	$(call quiet-command, \
@@ -637,6 +637,14 @@ dist: qemu-$(VERSION).tar.bz2
 qemu-%.tar.bz2:
 	$(SRC_PATH)/scripts/make-release "$(SRC_PATH)" "$(patsubst qemu-%.tar.bz2,%,$@)"
 
+# Note that these commands assume that there are no HTML files in
+# the docs subdir in the source tree! If there are then this will
+# blow them away for an in-source-tree 'make clean'.
+define clean-manual =
+rm -rf docs/$1/_static
+rm -f docs/$1/objects.inv docs/$1/searchindex.js docs/$1/*.html
+endef
+
 distclean: clean
 	rm -f config-host.mak config-host.h* config-host.ld $(DOCS) qemu-options.texi qemu-img-cmds.texi qemu-monitor.texi qemu-monitor-info.texi
 	rm -f config-all-devices.mak config-all-disas.mak config.status
@@ -657,6 +665,9 @@ distclean: clean
 	rm -f docs/interop/qemu-qmp-ref.html docs/interop/qemu-ga-ref.html
 	rm -f docs/qemu-block-drivers.7
 	rm -f docs/qemu-cpu-models.7
+	rm -f .doctrees
+	$(call clean-manual,devel)
+	$(call clean-manual,interop)
 	for d in $(TARGET_DIRS); do \
 	rm -rf $$d || exit 1 ; \
         done
@@ -690,7 +701,18 @@ else
 BLOBS=
 endif
 
-install-doc: $(DOCS)
+define install-manual =
+for d in $$(cd docs && find $1 -type d); do $(INSTALL_DIR) "$(DESTDIR)$(qemu_docdir)/$$d"; done
+for f in $$(cd docs && find $1 -type f); do $(INSTALL_DATA) "docs/$$f" "$(DESTDIR)$(qemu_docdir)/$$f"; done
+endef
+
+# Note that we deliberately do not install the "devel" manual: it is
+# for QEMU developers, and not interesting to our users.
+.PHONY: install-sphinxdocs
+install-sphinxdocs: sphinxdocs
+	$(call install-manual,interop)
+
+install-doc: $(DOCS) install-sphinxdocs
 	$(INSTALL_DIR) "$(DESTDIR)$(qemu_docdir)"
 	$(INSTALL_DATA) qemu-doc.html "$(DESTDIR)$(qemu_docdir)"
 	$(INSTALL_DATA) qemu-doc.txt "$(DESTDIR)$(qemu_docdir)"
@@ -841,6 +863,23 @@ docs/version.texi: $(SRC_PATH)/VERSION
 %.pdf: %.texi docs/version.texi
 	$(call quiet-command,texi2pdf $(TEXI2PDFFLAGS) $< -o $@,"GEN","$@")
 
+# Sphinx builds all its documentation at once in one invocation
+# and handles "don't rebuild things unless necessary" itself.
+# The '.doctrees' files are cached information to speed this up.
+.PHONY: sphinxdocs
+sphinxdocs: docs/devel/index.html docs/interop/index.html
+
+# Canned command to build a single manual
+build-manual = $(call quiet-command,sphinx-build $(if $(V),,-q) -b html -d .doctrees/$1 $(SRC_PATH)/docs/$1 docs/$1 ,"SPHINX","docs/$1")
+# We assume all RST files in the manual's directory are used in it
+manual-deps = $(wildcard $(SRC_PATH)/docs/$1/*.rst) $(SRC_PATH)/docs/$1/conf.py $(SRC_PATH)/docs/conf.py
+
+docs/devel/index.html: $(call manual-deps,devel)
+	$(call build-manual,devel)
+
+docs/interop/index.html: $(call manual-deps,interop)
+	$(call build-manual,interop)
+
 qemu-options.texi: $(SRC_PATH)/qemu-options.hx $(SRC_PATH)/scripts/hxtool
 	$(call quiet-command,sh $(SRC_PATH)/scripts/hxtool -t < $< > $@,"GEN","$@")
 
@@ -869,7 +908,7 @@ docs/qemu-block-drivers.7: docs/qemu-block-drivers.texi
 docs/qemu-cpu-models.7: docs/qemu-cpu-models.texi
 scripts/qemu-trace-stap.1: scripts/qemu-trace-stap.texi
 
-html: qemu-doc.html docs/interop/qemu-qmp-ref.html docs/interop/qemu-ga-ref.html
+html: qemu-doc.html docs/interop/qemu-qmp-ref.html docs/interop/qemu-ga-ref.html sphinxdocs
 info: qemu-doc.info docs/interop/qemu-qmp-ref.info docs/interop/qemu-ga-ref.info
 pdf: qemu-doc.pdf docs/interop/qemu-qmp-ref.pdf docs/interop/qemu-ga-ref.pdf
 txt: qemu-doc.txt docs/interop/qemu-qmp-ref.txt docs/interop/qemu-ga-ref.txt

configure

@@ -4589,13 +4589,24 @@ if compile_prog "" "" ; then
   syncfs=yes
 fi
 
+# Check we have a new enough version of sphinx-build
+has_sphinx_build() {
+    # This is a bit awkward but works: create a trivial document and
+    # try to run it with our configuration file (which enforces a
+    # version requirement). This will fail if either
+    # sphinx-build doesn't exist at all or if it is too old.
+    mkdir -p "$TMPDIR1/sphinx"
+    touch "$TMPDIR1/sphinx/index.rst"
+    sphinx-build -c "$source_path/docs" -b html "$TMPDIR1/sphinx" "$TMPDIR1/sphinx/out" >/dev/null 2>&1
+}
+
 # Check if tools are available to build documentation.
 if test "$docs" != "no" ; then
-  if has makeinfo && has pod2man; then
+  if has makeinfo && has pod2man && has_sphinx_build; then
     docs=yes
   else
     if test "$docs" = "yes" ; then
-      feature_not_found "docs" "Install texinfo and Perl/perl-podlators"
+      feature_not_found "docs" "Install texinfo, Perl/perl-podlators and python-sphinx"
     fi
     docs=no
   fi