From c455b1eeb36b1a93be28265dd3b68c646fc6a06d Mon Sep 17 00:00:00 2001
From: Aaron Lindsay <aaron@aclindsay.com>
Date: Wed, 26 Sep 2012 15:35:52 -0400
Subject: [PATCH] Makefile: refactor subdirectory makefiles

---
 Makefile             | 12 ++++++++----
 boot/Makefile.inc    |  3 ---
 boot/kernel.mk       | 10 ++++++++++
 devices/Makefile.inc |  5 -----
 devices/kernel.mk    | 12 ++++++++++++
 footer.mk            | 12 ++++++++++++
 header.mk            | 13 +++++++++++++
 kernel/Makefile.inc  | 11 -----------
 kernel/kernel.mk     | 19 +++++++++++++++++++
 9 files changed, 74 insertions(+), 23 deletions(-)
 delete mode 100644 boot/Makefile.inc
 create mode 100644 boot/kernel.mk
 delete mode 100644 devices/Makefile.inc
 create mode 100644 devices/kernel.mk
 create mode 100644 footer.mk
 create mode 100644 header.mk
 delete mode 100644 kernel/Makefile.inc
 create mode 100644 kernel/kernel.mk

diff --git a/Makefile b/Makefile
index 769086a..ec118d1 100644
--- a/Makefile
+++ b/Makefile
@@ -22,11 +22,15 @@ KCFLAGS = -g -Wall -Wextra -Werror -nostdlib -nostartfiles -fno-builtin -std=gnu
 KLDFLAGS = -T link.ld -L /usr/lib/gcc/arm-elf/4.7.0/
 EXTRA_LIBS = -lgcc
 
-KOBJS =
+# Define KOBJS as a 'simply expanded' variable
+KOBJS :=
 
-include boot/Makefile.inc
-include kernel/Makefile.inc
-include devices/Makefile.inc
+# Initialize sub-directory Makefile inclusion
+BASEDIR = $(shell pwd)
+SUBDIRS := boot kernel devices
+ifneq (,$(SUBDIRS))
+	include $(patsubst %,%/kernel.mk,$(SUBDIRS))
+endif
 
 .PHONY: all clean boot boot-gdb
 
diff --git a/boot/Makefile.inc b/boot/Makefile.inc
deleted file mode 100644
index d9df028..0000000
--- a/boot/Makefile.inc
+++ /dev/null
@@ -1,3 +0,0 @@
-BOOT_PREFIX = boot
-
-KOBJS += $(BOOT_PREFIX)/start.o
diff --git a/boot/kernel.mk b/boot/kernel.mk
new file mode 100644
index 0000000..b4f1b32
--- /dev/null
+++ b/boot/kernel.mk
@@ -0,0 +1,10 @@
+DIRNAME := boot
+SUBDIRS :=
+
+include $(BASEDIR)/header.mk
+
+OBJS_$(d) := $(d)/start.o
+
+KOBJS += $(OBJS_$(d))
+
+include $(BASEDIR)/footer.mk
diff --git a/devices/Makefile.inc b/devices/Makefile.inc
deleted file mode 100644
index 4e19edb..0000000
--- a/devices/Makefile.inc
+++ /dev/null
@@ -1,5 +0,0 @@
-DEVICES_PREFIX = devices
-
-KOBJS += $(DEVICES_PREFIX)/pl011.o
-KOBJS += $(DEVICES_PREFIX)/pl110.o
-KOBJS += $(DEVICES_PREFIX)/pl111.o
diff --git a/devices/kernel.mk b/devices/kernel.mk
new file mode 100644
index 0000000..a0451c7
--- /dev/null
+++ b/devices/kernel.mk
@@ -0,0 +1,12 @@
+DIRNAME := devices
+SUBDIRS :=
+
+include $(BASEDIR)/header.mk
+
+OBJS_$(d) := $(d)/pl011.o \
+	$(d)/pl110.o \
+	$(d)/pl111.o
+
+KOBJS += $(OBJS_$(d))
+
+include $(BASEDIR)/footer.mk
diff --git a/footer.mk b/footer.mk
new file mode 100644
index 0000000..15077d7
--- /dev/null
+++ b/footer.mk
@@ -0,0 +1,12 @@
+# Included at the bottom of each subdirectory Makefile
+
+# Include any subdirectory Makefiles
+ifneq (,$(SUBDIRS))
+	include $(patsubst %,$(d)/%/kernel.mk,$(SUBDIRS))
+endif
+
+# Pop the previous directory off the 'stack' 
+d := $(dirstack_$(sp))
+sp := $(basename $(sp))
+# Clear SUBDIRS so that it defaults to empty for the next directory
+SUBDIRS :=
diff --git a/header.mk b/header.mk
new file mode 100644
index 0000000..95dceb5
--- /dev/null
+++ b/header.mk
@@ -0,0 +1,13 @@
+# Included at the top of each subdirectory Makefile, immediately
+# following the local re-definition of DIRNAME
+
+# Push the previous directory onto the 'stack'
+sp := $(sp).x
+dirstack_$(sp) := $(d)
+
+# Update $(d) to be the current directory
+ifneq (,$(d))
+	d := $(d)/$(DIRNAME)
+else
+	d := $(DIRNAME)
+endif
diff --git a/kernel/Makefile.inc b/kernel/Makefile.inc
deleted file mode 100644
index 8870cbd..0000000
--- a/kernel/Makefile.inc
+++ /dev/null
@@ -1,11 +0,0 @@
-KERNEL_PREFIX = kernel
-
-KOBJS += $(KERNEL_PREFIX)/atags.o
-KOBJS += $(KERNEL_PREFIX)/console.o
-KOBJS += $(KERNEL_PREFIX)/font.o
-KOBJS += $(KERNEL_PREFIX)/framebuffer.o
-KOBJS += $(KERNEL_PREFIX)/list.o
-KOBJS += $(KERNEL_PREFIX)/mm.o
-KOBJS += $(KERNEL_PREFIX)/mmu.o
-KOBJS += $(KERNEL_PREFIX)/print.o
-KOBJS += $(KERNEL_PREFIX)/start_kernel.o
diff --git a/kernel/kernel.mk b/kernel/kernel.mk
new file mode 100644
index 0000000..1e0f065
--- /dev/null
+++ b/kernel/kernel.mk
@@ -0,0 +1,19 @@
+DIRNAME := kernel
+SUBDIRS :=
+
+include $(BASEDIR)/header.mk
+
+OBJS_$(d) := $(d)/atags.o \
+	$(d)/console.o \
+	$(d)/font.o \
+	$(d)/framebuffer.o \
+	$(d)/kmalloc.o \
+	$(d)/list.o \
+	$(d)/mm.o \
+	$(d)/mmu.o \
+	$(d)/print.o \
+	$(d)/start_kernel.o
+
+KOBJS += $(OBJS_$(d))
+
+include $(BASEDIR)/footer.mk