On Fri, 19 Aug 2011, Arnaud Lacombe wrote: > Hi folks, > > The attached patch modify Kbuild to allow to directly re-use code in multiple > directory without having to go through a copy. Technically, it changes Kbuild to > use by default the VPATH feature of GNU make and provides accessors for Makefile > to change it indirectly. > > Considering: > > arch/foo/lib: > fancy.c > > We want to be able to build it with -DPANTS=32 in the kernel, but the > bootloader requires -DPANTS_SIZE=30. > > Currently we would do, either: > > arch/foo/lib/Makefile > LDFLAGS_fancy.o := -DPANTS=32 > obj-y += fancy.o > > and, either: > > arch/foo/boot/Makefile: > LDFLAGS_fancy.o := -DPANTS=30 > obj-y += fancy.o > $(obj)/fancy.c: $(srctree)/arch/foo/lib/fancy.c > $(call cmd,shipped) > > or > > arch/foo/boot/Makefile: > LDFLAGS_fancy.o := -DPANTS=30 > obj-y += fancy.o > $(obj)/fancy.o: $(srctree)/arch/foo/lib/fancy.c > $(call cmd,cc_c_o) > > The former implies an extra copy of the source file, the latter expose Kbuild > internal function. > > With the attached patch, we would do: > > arch/foo/boot/Makefile: > LDFLAGS_fancy.o := -DPANTS=30 > obj-y += fancy.o > vpath-y += $(srctree)/arch/foo/lib > > and let GNU make do the job. > > Comments welcome, It doesn't work. Whatever I do to arch/arm/boot/compressed/Makefile (which admittedly looks a bit hairy and could benefit from a shave) in order to remove the $(call cmd,shipped) used with lib1funcs.S, I always end up with: make[2]: *** No rule to make target `arch/arm/boot/compressed/lib1funcs.S', needed by `arch/arm/boot/compressed/lib1funcs.o'. Stop. Obviously, restoring the explicit dependency with a $(call cmd,as_o_S) does make it work, but this is rather against the point of your patch. Do you have an example of how arch/arm/boot/compressed/Makefile should be changed to benefit from your patch? Nicolas -- To unsubscribe from this list: send the line "unsubscribe linux-kbuild" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
