docs: Only regenerate vswitch.pic when the schema really changes.

[openvswitch] / vswitchd / automake.mk

diff --git a/vswitchd/automake.mk b/vswitchd/automake.mk
index 6ef776349e233f59c63b916273ae849c80ff9d1b..4c3c07622e5c490aac578f96ffe63dfed2815e18 100644 (file)
--- a/vswitchd/automake.mk
+++ b/vswitchd/automake.mk
@@ -49,19 +49,36 @@ vswitchd/vswitch-idl.ovsidl: $(VSWITCH_IDL_FILES)
        mv $@.tmp $@
 
 # vswitch E-R diagram
-if BUILD_ER_DIAGRAMS
-$(srcdir)/vswitchd/vswitch.pic: ovsdb/ovsdb-dot.in ovsdb/dot2pic \
-                                vswitchd/vswitch.ovsschema
-       $(OVSDB_DOT) $(srcdir)/vswitchd/vswitch.ovsschema \
-               | dot -T plain \
-               | $(srcdir)/ovsdb/dot2pic \
-               > $@.tmp
-       mv $@.tmp $@
+#
+# There are two complications here.  First, if "python" or "dot" is not
+# available, then we have to just use the existing diagram.  Second, different
+# "dot" versions produce slightly different output for the same input, but we
+# don't want to gratuitously change vswitch.pic if someone tweaks the schema in
+# some minor way that doesn't affect the table structure.  To avoid that we
+# store a checksum of vswitch.gv in vswitch.pic and only regenerate vswitch.pic
+# if vswitch.gv actually changes.
+$(srcdir)/vswitchd/vswitch.gv: ovsdb/ovsdb-dot.in vswitchd/vswitch.ovsschema
+if HAVE_PYTHON
+       $(OVSDB_DOT) $(srcdir)/vswitchd/vswitch.ovsschema > $@
+else
+       touch $@
+endif
+$(srcdir)/vswitchd/vswitch.pic: $(srcdir)/vswitchd/vswitch.gv ovsdb/dot2pic
+if HAVE_DOT
+       sum=`cksum < $(srcdir)/vswitchd/vswitch.gv`;                    \
+       if grep "$$sum" $@ >/dev/null 2>&1; then                        \
+         echo "vswitch.gv unchanged, not regenerating vswitch.pic";    \
+         touch $@;                                                     \
+       else                                                            \
+         echo "regenerating vswitch.pic";                              \
+         (echo ".\\\" Generated from vswitch.gv with cksum \"$$sum\""; \
+          dot -T plain < $(srcdir)/vswitchd/vswitch.gv                 \
+           | $(srcdir)/ovsdb/dot2pic) > $@;                            \
+       fi
 else
-$(srcdir)/vswitchd/vswitch.pic: ovsdb/ovsdb-dot.in vswitchd/vswitch.ovsschema
        touch $@
 endif
-EXTRA_DIST += vswitchd/vswitch.pic
+EXTRA_DIST += vswitchd/vswitch.gv vswitchd/vswitch.pic
 
 # vswitch schema documentation
 EXTRA_DIST += vswitchd/vswitch.xml