ofwbus: only allow unit number zero

[mhorne]

Summary

ofwbus has always been the root of attachment for OFW/FDT platforms. It
may have simplebus children, but we expect only one instance of the
ofwbus driver, added directly by nexus. We may as well ensure this
remains the case.

sys/dev/ofw/ofwbus.c

 
 .else
 
-# Look for ${PATCH_WRKSRC}/.../*.orig files, and (re-)create
-# ${FILEDIR}/patch-* files from them.
+# Look for files named "*.orig" under ${PATCH_WRKSRC} and (re-)generate
+# ${FILESDIR}/patch-* files from them.  By popular demand, we currently
+# use '_' (underscore) to replace path separators in patch file names.
+#
+# If a file name happens to contain character which is also a separator
+# replacement character, it will be doubled in the resulting patch name.
+#
+# To minimize gratuitous patch renames, newly generated patches will be
+# written under existing file names when they use any of the previously
+# common path separators ([-+_]) or legacy double underscore (__).
 
 .if !target(makepatch)
+PATCH_PATH_SEPARATOR=   _
 makepatch:
         @${MKDIR} ${FILESDIR}
         @(cd ${PATCH_WRKSRC}; \
-                for f in `${FIND} . -type f -name '*.orig'`; do \
+                for f in `${FIND} -s . -type f -name '*.orig'`; do \
                         ORIG=$${f#./}; \
                         NEW=$${ORIG%.orig}; \
                         cmp -s $${ORIG} $${NEW} && continue; \
-                        PATCH=`${ECHO} $${NEW} | ${SED} -e 's|/|__|g'`; \
+                        ! for _lps in `${ECHO} _ - + | ${SED} -e \
+                                's|${PATCH_PATH_SEPARATOR}|__|'`; do \
+                                        PATCH=`${ECHO} $${NEW} | ${SED} -e "s|/|$${_lps}|g"`; \
+                                        test -f "${FILESDIR}/patch-$${PATCH}" && break; \
+                        done || ${ECHO} $${_SEEN} | ${GREP} -q /$${PATCH} && { \
+                                PATCH=`${ECHO} $${NEW} | ${SED} -e \
+                                        's|${PATCH_PATH_SEPARATOR}|&&|g' -e \
+                                        's|/|${PATCH_PATH_SEPARATOR}|g'`; \
+                                _SEEN=$${_SEEN}/$${PATCH}; \
+                        }; \
                         OUT=${FILESDIR}/patch-$${PATCH}; \
-                        ${ECHO} ${DIFF} -ud $${ORIG} $${NEW} '>' $${OUT}; \
-                        TZ=UTC ${DIFF} -ud $${ORIG} $${NEW} | ${SED} -e \
+                        ${ECHO} ${DIFF} -udp $${ORIG} $${NEW} '>' $${OUT}; \
+                        TZ=UTC ${DIFF} -udp $${ORIG} $${NEW} | ${SED} -e \
                                 '/^---/s|\.[0-9]* +0000$$| UTC|' -e \
                                 '/^+++/s|\([[:blank:]][-0-9:.+]*\)*$$||' \
                                         > $${OUT} || ${TRUE}; \