Makefile: Add automatic dependency generation

.gitignore

@@ -2,3 +2,4 @@ aedrix-kernel.elf
 aedrix-kernel.img
 *.o
 *.swp
+*.d

Makefile

@@ -50,21 +50,27 @@ aedrix-kernel.img: aedrix-kernel.elf
 
 %.o: %.c
 	@echo '     CC   $@'
-	$(V)$(CC) $(KCFLAGS) -c -o $@ $<
+	$(V)$(CC) $(KCFLAGS) -MD -c -o $@ $<
+	@# Automatic dependency generation fixups (http://mad-scientist.net/make/autodep.html)
+	@cp $*.d $(*D)/.$(*F).d; \
+		sed -e 's/#.*//' -e 's/^[^:]*: *//' -e 's/ *\\$$//' \
+		-e '/^$$/ d' -e 's/$$/ :/' < $*.d >> $(*D)/.$(*F).d; \
+		rm -f $*.d
 
-# Assembly files without preprocessor directives
-%.o: %.s
-	@echo '     AS   $@'
-	$(V)$(AS) -o $@ $<
-
-# Assembly files with preprocessor directives
 %.o: %.S
 	@echo '     AS   $@'
-	$(V)$(AS) -o $@ $<
+	$(V)$(CC) $(KCFLAGS) -MD -c -o $@ $<
+	@# Automatic dependency generation fixups (http://mad-scientist.net/make/autodep.html)
+	@cp $*.d $(*D)/.$(*F).d; \
+		sed -e 's/#.*//' -e 's/^[^:]*: *//' -e 's/ *\\$$//' \
+		-e '/^$$/ d' -e 's/$$/ :/' < $*.d >> $(*D)/.$(*F).d; \
+		rm -f $*.d
 
 clean:
 	@echo '  CLEAN   *.o'
 	$(V)rm -f $(KOBJS)
+	@echo '  CLEAN   .*.d'
+	$(V)rm -f $(DEPENDENCY_FILES)
 	@echo '  CLEAN   aedrix-kernel.elf'
 	$(V)rm -f aedrix-kernel.elf
 	@echo '  CLEAN   aedrix-kernel.objdump'
@@ -76,3 +82,6 @@ boot: aedrix-kernel.img
 	$(V)qemu-system-arm -m 1024 -M vexpress-a9 -kernel aedrix-kernel.img -serial stdio
 boot-gdb: aedrix-kernel.img
 	$(V)qemu-system-arm -m 1024 -M vexpress-a9 -kernel aedrix-kernel.img -serial stdio -S -s
+
+DEPENDENCY_FILES = $(foreach file,$(KOBJS), $(dir $(file)).$(notdir $(basename $(file))).d)
+-include $(DEPENDENCY_FILES)