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.

Always provide the enum definitions.

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]>
Signed-off-by: Thomas Gleixner <[email protected]>
Acked-by: Arnd Bergmann <[email protected]>
Link: https://patch.msgid.link/[email protected]

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

include/vdso/clocksource.h

@@ -4,13 +4,11 @@
 
 #include <vdso/limits.h>
 
-#ifdef CONFIG_GENERIC_GETTIMEOFDAY
 #include <asm/vdso/clocksource.h>
-#endif /* CONFIG_GENERIC_GETTIMEOFDAY */
 
 enum vdso_clock_mode {
 	VDSO_CLOCKMODE_NONE,
-#ifdef CONFIG_GENERIC_GETTIMEOFDAY
+#ifdef VDSO_ARCH_CLOCKMODES
 	VDSO_ARCH_CLOCKMODES,
 #endif
 	VDSO_CLOCKMODE_MAX,