Adjust dependency rules to permit per-file flags

The dependency rules are currently done in a shell 'for' loop. This does not
permit Makefile variables to adjust preprocessor flags as is done with normal
compile flags, using the CFLAGS_path/file.o syntax.

This change moves the dependency generation into the Makefile itself, and
permits a CPPFLAGS_path/file.o to adjust preprocessor flags on a file or
directory basis.

The CPPFLAGS_... variable is also folded into CFLAGS during the build.

Signed-off-by: Simon Glass <sjg@chromium.org>

.gitignore

@@ -40,7 +40,7 @@
 # Generated files
 #
 
-*.depend
+*.depend*
 /LOG
 /errlog
 /reloc_off

Makefile

@@ -955,7 +955,7 @@ clean:
 		| xargs rm -f
 
 clobber:	clean
-	@find $(OBJTREE) -type f \( -name '*.depend' \
+	@find $(OBJTREE) -type f \( -name '*.depend*' \
 		-o -name '*.srec' -o -name '*.bin' -o -name u-boot.img \) \
 		-print0 \
 		| xargs -0 rm -f

config.mk

@@ -277,6 +277,13 @@ export	CONFIG_SYS_TEXT_BASE PLATFORM_CPPFLAGS PLATFORM_RELFLAGS CPPFLAGS CFLAGS
 BCURDIR = $(subst $(SRCTREE)/,,$(CURDIR:$(obj)%=%))
 ALL_AFLAGS = $(AFLAGS) $(AFLAGS_$(BCURDIR)/$(@F)) $(AFLAGS_$(BCURDIR))
 ALL_CFLAGS = $(CFLAGS) $(CFLAGS_$(BCURDIR)/$(@F)) $(CFLAGS_$(BCURDIR))
+EXTRA_CPPFLAGS = $(CPPFLAGS_$(BCURDIR)/$(@F)) $(CPPFLAGS_$(BCURDIR))
+ALL_CFLAGS += $(EXTRA_CPPFLAGS)
+
+# The _DEP version uses the $< file target (for dependency generation)
+# See rules.mk
+EXTRA_CPPFLAGS_DEP = $(CPPFLAGS_$(BCURDIR)/$(addsuffix .o,$(basename $<))) \
+		$(CPPFLAGS_$(BCURDIR))
 $(obj)%.s:	%.S
 	$(CPP) $(ALL_AFLAGS) -o $@ $<
 $(obj)%.o:	%.S

rules.mk

@@ -25,17 +25,39 @@
 
 _depend:	$(obj).depend
 
-$(obj).depend:	$(src)Makefile $(TOPDIR)/config.mk $(SRCS) $(HOSTSRCS)
-		@rm -f $@
-		@touch $@
-		@for f in $(SRCS); do \
-			g=`basename $$f | sed -e 's/\(.*\)\.[[:alnum:]_]/\1.o/'`; \
-			$(CC) -M $(CPPFLAGS) -MQ $(obj)$$g $$f >> $@ ; \
-		done
-		@for f in $(HOSTSRCS); do \
-			g=`basename $$f | sed -e 's/\(.*\)\.[[:alnum:]_]/\1.o/'`; \
-			$(HOSTCC) -M $(HOSTCPPFLAGS) -MQ $(obj)$$g $$f >> $@ ; \
-		done
+# Split the source files into two camps: those in the current directory, and
+# those somewhere else. For the first camp we want to support CPPFLAGS_<fname>
+# and for the second we don't / can't.
+PWD_SRCS := $(filter $(notdir $(SRCS)),$(SRCS))
+OTHER_SRCS := $(filter-out $(notdir $(SRCS)),$(SRCS))
+
+# This is a list of dependency files to generate
+DEPS := $(basename $(patsubst %,$(obj).depend.%,$(PWD_SRCS)))
+
+# Join all the dependencies into a single file, in three parts
+#	1 .Concatenate all the generated depend files together
+#	2. Add in the deps from OTHER_SRCS which we couldn't process
+#	3. Add in the HOSTSRCS
+$(obj).depend:	$(src)Makefile $(TOPDIR)/config.mk $(DEPS) $(HOSTSRCS)
+	cat /dev/null $(DEPS) >$@
+	@for f in $(OTHER_SRCS); do \
+		g=`basename $$f | sed -e 's/\(.*\)\.[[:alnum:]_]/\1.o/'`; \
+		$(CC) -M $(CPPFLAGS) -MQ $(obj)$$g $$f >> $@ ; \
+	done
+	@for f in $(HOSTSRCS); do \
+		g=`basename $$f | sed -e 's/\(.*\)\.[[:alnum:]_]/\1.o/'`; \
+		$(HOSTCC) -M $(HOSTCPPFLAGS) -MQ $(obj)$$g $$f >> $@ ; \
+	done
+
+MAKE_DEPEND = $(CC) -M $(CPPFLAGS) $(EXTRA_CPPFLAGS_DEP) \
+		-MQ $(addsuffix .o,$(obj)$(basename $<)) $< >$@
+
+
+$(obj).depend.%:	%.c
+	$(MAKE_DEPEND)
+
+$(obj).depend.%:	%.S
+	$(MAKE_DEPEND)
 
 $(HOSTOBJS): $(obj)%.o: %.c
 	$(HOSTCC) $(HOSTCFLAGS) $(HOSTCFLAGS_$(@F)) $(HOSTCFLAGS_$(BCURDIR)) -o $@ $< -c