Kbuild test robot reports the following problem on ARM:
for 'xen_setup_callback_vector' [-Wmissing-prototypes]drivers/xen/events/events_base.c:1664:6: warning: no previous prototype
1664 | void xen_setup_callback_vector(void) {}
| ^~~~~~~~~~~~~~~~~~~~~~~~~
The problem is that xen_setup_callback_vector is a x86 only thing, its
definition is present in arch/x86/xen/xen-ops.h but not on ARM. In
events_base.c we have a stub for !CONFIG_XEN_PVHVM but it is not
declared as 'static'.
On x86 the situation is hardly better: drivers/xen/events/events_base.c
doesn't include 'xen-ops.h' from arch/x86/xen/, it includes its namesake
from include/xen/ so we also get the 'no previous prototype' warning.
Currently, xen_setup_callback_vector() has two call sites: one in
drivers/xen/events_base.c and another in arch/x86/xen/suspend_hvm.c. The
former is placed under #ifdef CONFIG_X86 and the later is only compiled
in when CONFIG_XEN_PVHVM.
Resolve the issue by moving xen_setup_callback_vector() declaration to
arch neutral 'include/xen/hvm.h' as the implementation lives in arch
neutral drivers/xen/events/events_base.c.
Reported-by: kbuild test robot <lkp@xxxxxxxxx>
Signed-off-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>