On Mon, 21 Mar 2022, Christophe Leroy wrote:

Le 21/03/2022 à 05:30, Finn Thain a écrit :

quoted

drivers/macintosh/via-pmu-event.o: In function `via_pmu_event':
via-pmu-event.c:(.text+0x44): undefined reference to `input_event'
via-pmu-event.c:(.text+0x68): undefined reference to `input_event'
via-pmu-event.c:(.text+0x94): undefined reference to `input_event'
via-pmu-event.c:(.text+0xb8): undefined reference to `input_event'
drivers/macintosh/via-pmu-event.o: In function `via_pmu_event_init':
via-pmu-event.c:(.init.text+0x20): undefined reference to `input_allocate_device'
via-pmu-event.c:(.init.text+0xc4): undefined reference to `input_register_device'
via-pmu-event.c:(.init.text+0xd4): undefined reference to `input_free_device'
make[1]: *** [Makefile:1155: vmlinux] Error 1
make: *** [Makefile:350: __build_one_by_one] Error 2

Don't call into the input subsystem unless CONFIG_INPUT is built-in.

Reported-by: kernel test robot <redacted>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Randy Dunlap <redacted>
Signed-off-by: Finn Thain <fthain@linux-m68k.org>
---
This is equivalent to the patch I sent a couple of days ago. This one
is slightly longer and adds a new symbol so that Kconfig logic can been
used instead of Makefile logic in case reviewers prefer that.
---
  drivers/macintosh/Kconfig   | 5 +++++
  drivers/macintosh/Makefile  | 3 ++-
  drivers/macintosh/via-pmu.c | 2 ++
  3 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/drivers/macintosh/Kconfig b/drivers/macintosh/Kconfig
index 5cdc361da37c..b9102f051bbb 100644
--- a/drivers/macintosh/Kconfig
+++ b/drivers/macintosh/Kconfig

@@ -67,6 +67,11 @@ config ADB_PMU
  	  this device; you should do so if your machine is one of those
  	  mentioned above.
  
+config ADB_PMU_EVENT
+	bool
+	depends on ADB_PMU && INPUT=y
+	default y

Could be reduced to

config ADB_PMU_EVENT
	def_bool y if ADB_PMU && INPUT=y

That's great but my question remains unanswered: why the aversion to 
conditionals in Makefiles, when that would be simpler (no new symbol)?