On Tue, 28 Feb 2023 at 06:43, Linus Torvalds torvalds@linux-foundation.org wrote:
On Fri, Feb 24, 2023 at 5:45 PM David Gow davidgow@google.com wrote:
+# Some KUnit files (hooks.o) need to be built-in even when KUnit is a module, +# so we can't just use obj-$(CONFIG_KUNIT). +ifdef CONFIG_KUNIT +obj-y += kunit/ endif
We actually have a pattern for this, although I guess it's rare enough that "pattern" isn't necessarily the right word.
But you can find things like the Hyper-V drivers having similar issues, and so the driver Makefile has
obj-$(subst m,y,$(CONFIG_HYPERV)) += hv/See a few other cases with
git grep "subst m,y,"but I guess the "ifdef CONFIG_KUNIT" thing works too. I can only find one case of that (in arch/mips/Kbuild).
Another way of dealing with this - that is more common for individual object files rather than directories - is to just do
kunit-dir-$(CONFIG_KUNIT) := kunit/ obj-y += $(kunit-dir-y) $(kunit-dir-m)which admittedly is also not a hugely common pattern, but does exist in various places (see for example the 'sfp-bus.o' file and CONFIG_SFP in drivers/net/phy/Makefile.
That last pattern is probably most common in scripts/Makefile.lib, where we have things like
hostprogs += $(hostprogs-always-y) $(hostprogs-always-m)which is similar but not the exact same thing.
Anyway, I guess I'll just apply that patch as-is, I just wanted to point out that the particular pattern it uses may be simple, but we've generally tried to just do our Makefile evaluations with "arithmetic" rather than conditionals.
Linus
Thanks, Linus.
(And also thanks to Mikhail Gavrilov and Thorsten Leemhuis for testing this change as well.)
It's certainly been an educational experience!
Of those other options, personally I find the "subst m,y" one most obvious, but I'll probably leave it as the conditional for now, unless you think trying to make it more consistent is worth the extra churn.
Regardless, I'll look into adding a note about this to Documentation/kbuild/makefiles.rst.
Cheers, -- David