Add simple config system for both #ifdef's and conditional compilation

.gitignore

@@ -1,5 +1,7 @@
 aedrix-kernel.elf
 aedrix-kernel.img
+config
+config.h
 *.o
 *.swp
 *.d

Makefile

@@ -18,10 +18,13 @@ OBJDUMP = $(TOOL_PREFIX)objdump
 
 # Define the flags we'll need for our tools
 INCLUDES = -I include
-KCFLAGS = -g -Wall -Wextra -Werror -nostdlib -nostartfiles -fno-builtin -std=gnu99 $(INCLUDES)
+KCFLAGS = -g -Wall -Wextra -Werror -nostdlib -nostartfiles -fno-builtin -std=gnu99 -include config.h $(INCLUDES)
 KLDFLAGS = -T link.ld -L /usr/lib/gcc/arm-elf/4.7.0/
 EXTRA_LIBS = -lgcc
 
+# Include the config file so we don't compile/link unnecessary objects
+include config
+
 # Define KOBJS as a 'simply expanded' variable
 KOBJS :=
 
@@ -48,7 +51,7 @@ aedrix-kernel.img: aedrix-kernel.elf
 	@echo 'OBJCOPY   $@'
 	$(V)$(OBJCOPY) $< -O binary $@
 
-%.o: %.c
+%.o: %.c config.h
 	@echo '     CC   $@'
 	$(V)$(CC) $(KCFLAGS) -MD -c -o $@ $<
 	@# Automatic dependency generation fixups (http://mad-scientist.net/make/autodep.html)
@@ -57,7 +60,7 @@ aedrix-kernel.img: aedrix-kernel.elf
 		-e '/^$$/ d' -e 's/$$/ :/' < $*.d >> $(*D)/.$(*F).d; \
 		rm -f $*.d
 
-%.o: %.S
+%.o: %.S config.h
 	@echo '     AS   $@'
 	$(V)$(CC) $(KCFLAGS) -MD -c -o $@ $<
 	@# Automatic dependency generation fixups (http://mad-scientist.net/make/autodep.html)
@@ -66,7 +69,16 @@ aedrix-kernel.img: aedrix-kernel.elf
 		-e '/^$$/ d' -e 's/$$/ :/' < $*.d >> $(*D)/.$(*F).d; \
 		rm -f $*.d
 
+config.h: config
+	@echo ' CONFIG   config.h'
+	@cp config config.h
+	@sed -i '/^\w*#/d' config.h
+	@sed -i '/^\s*\(CONFIG_[A-Z0-9_]\+\)\s*=\s*[nN]/d' config.h
+	@sed -i 's/^\s*\(CONFIG_[A-Z0-9_]\+\)\s*=\s*[yY]/#define \1/g' config.h
+
 clean:
+	@echo '  CLEAN   config.h'
+	$(V)rm -f config.h
 	@echo '  CLEAN   *.o'
 	$(V)rm -f $(KOBJS)
 	@echo '  CLEAN   .*.d'

config_example

@@ -0,0 +1,3 @@
+CONFIG_RPI = y
+#CONFIG_VEXPRESS_A9 = y
+#CONFIG_INTEGRATOR_CP = n

devices/kernel.mk

@@ -3,13 +3,18 @@ SUBDIRS :=
 
 include $(BASEDIR)/header.mk
 
-OBJS_$(d) := $(d)/pl011.o \
+OBJS_$(d)_$(CONFIG_VEXPRESS_A9) := \
+	$(d)/pl011.o \
+	$(d)/pl111.o
+
+OBJS_$(d)_$(CONFIG_INTEGRATOR_CP) := \
 	$(d)/pl110.o \
-	$(d)/pl111.o \
+
+OBJS_$(d)_$(CONFIG_RPI) := \
 	$(d)/pi_mini_uart.o \
 	$(d)/bcm2835_mailbox.o \
 	$(d)/bcm2835_videocore.o
 
-KOBJS += $(OBJS_$(d))
+KOBJS += $(OBJS_$(d)_y)
 
 include $(BASEDIR)/footer.mk

kernel/start_kernel.c

@@ -23,12 +23,19 @@
 #include <mmu.h>
 #include <mm.h>
 #include <print.h>
-#include <devices/pi_mini_uart.h>
-
-#include <devices/bcm2835_videocore.h>
 #include <framebuffer.h>
 #include <console.h>
 
+#ifdef CONFIG_VEXPRESS_A9
+#include <devices/pl011.h>
+#include <devices/pl111.h>
+#endif
+
+#ifdef CONFIG_RPI
+#include <devices/pi_mini_uart.h>
+#include <devices/bcm2835_videocore.h>
+#endif
+
 struct fb myfb;
 
 void print_console_logo() {
@@ -41,7 +48,12 @@ void print_console_logo() {
 }
 
 void video_init(void) {
+#ifdef CONFIG_VEXPRESS_A9
+	pl111_init(&myfb, 16);
+#endif
+#ifdef CONFIG_RPI
 	bcm2835_videocore_init(&myfb, 16);
+#endif
 }
 
 void test_mm() {
@@ -124,8 +136,13 @@ int main(void) {
 	mmu_reinit();
 
 	//initialize the serial console
+#ifdef CONFIG_VEXPRESS_A9
+	print_init(&pl011_putc);
+#endif
+#ifdef CONFIG_RPI
 	mini_uart_init();
 	print_init(&mini_uart_putc);
+#endif
 
 	//setup memory
 	mm_init();