[PATCH 2/7] vDSO: Make clockmode constants available without CONFIG_GENERIC_GETTIMEOFDAY

Some code, for example clocksource drivers, may want to use the vDSO
clockmode constants even when CONFIG_GENERIC_GETTIMEOFDAY=n.
But the symbols are completely hidden in that case, making ugly
ifdeffery necessary.

Provide unlinkable dummy definitions. These can be used with
IS_ENABLED(CONFIG_GENERIC_GETTIMEOFDAY).

As not all architectures provide asm/vdso/clocksource.h,
provide an empty stub in asm-generic for it.

Signed-off-by: Thomas Weißschuh <[email protected]>
---
 include/asm-generic/Kbuild             | 1 +
 include/asm-generic/vdso/clocksource.h | 0
 include/vdso/clocksource.h             | 7 +++++--
 3 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/include/asm-generic/Kbuild b/include/asm-generic/Kbuild
index 15df9dcb42a5..2bc00c67dc54 100644
--- a/include/asm-generic/Kbuild
+++ b/include/asm-generic/Kbuild
@@ -62,6 +62,7 @@ mandatory-y += topology.h
 mandatory-y += trace_clock.h
 mandatory-y += uaccess.h
 mandatory-y += unwind_user.h
+mandatory-y += vdso/clocksource.h
 mandatory-y += vermagic.h
 mandatory-y += vga.h
 mandatory-y += video.h
diff --git a/include/asm-generic/vdso/clocksource.h b/include/asm-generic/vdso/clocksource.h
new file mode 100644
index 000000000000..e69de29bb2d1
diff --git a/include/vdso/clocksource.h b/include/vdso/clocksource.h
index c682e7c60273..63ee8c4ea15c 100644
--- a/include/vdso/clocksource.h
+++ b/include/vdso/clocksource.h
@@ -4,9 +4,12 @@
 
 #include <vdso/limits.h>
 
-#ifdef CONFIG_GENERIC_GETTIMEOFDAY
 #include <asm/vdso/clocksource.h>
-#endif /* CONFIG_GENERIC_GETTIMEOFDAY */
+
+#if !IS_ENABLED(CONFIG_GENERIC_GETTIMEOFDAY) && defined(VDSO_ARCH_CLOCKMODES)
+/* Unlinkable dummy stubs */
+extern int VDSO_ARCH_CLOCKMODES;
+#endif
 
 enum vdso_clock_mode {
 	VDSO_CLOCKMODE_NONE,

-- 
2.55.0