Dear Robert P. J. Day,

On Wednesday, November 14, 2012 4:35:15 PM, Robert P. J. Day wrote:

i'm sure there's a trivial explanation for this that i'm missing but i'm looking at this snippet from arch/arm/cpu/armv7/omap3/Makefile:

... snip ... COBJS += board.o COBJS += clock.o COBJS += mem.o COBJS += sys_info.o ifdef CONFIG_SPL_BUILD COBJS-$(CONFIG_SPL_OMAP3_ID_NAND) += spl_id_nand.o endif

COBJS-$(CONFIG_DRIVER_TI_EMAC) += emac.o COBJS-$(CONFIG_EMIF4) += emif4.o COBJS-$(CONFIG_SDRC) += sdrc.o <--- this line, eg.

SRCS := $(SOBJS:.o=.S) $(COBJS:.o=.c) OBJS := $(addprefix $(obj),$(COBJS) $(COBJS-y) $(SOBJS)) ... snip ...

how does the fact that the beagle that i'm building for, which defines:

include/configs/omap3_beagle.h:#define CONFIG_SDRC

translate that simple #define into a value that can be used by the Makefile to select sdrc.o to be compiled?

i'm used to the linux kernel config process which explicitly sets the variables to the string "y", so that, in the above, the variable $(COBJS-y) would pick up those conditional compilations.

but what is happening here? i'm sure it's simple, i just don't see where it's happening in the config and build process. thanks.

Take a look at the following rule in the main Makefile: $(obj)include/autoconf.mk: $(obj)include/config.h

Best regards, Benoît