x86: Add i8042 pre-detection hook to x86_platform_ops

Some x86 platforms like Intel MID platforms don't have i8042 controllers,
and i8042 driver's probe to some legacy IO ports may hang the MID
processor. With this hook, i8042 driver can runtime check and skip the
probe when the pretection fail which also saves some probe time

[ hpa note: this is currently a compile-time check, which breaks the
  i386 allyesconfig build.  This patch series thus does fix a regression. ]

Signed-off-by: Feng Tang <feng.tang@intel.com>
LKML-Reference: <1278342202-10973-2-git-send-email-feng.tang@intel.com>
Acked-by: Dmitry Torokhov <dtor@mail.ru>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
diff --git a/arch/x86/kernel/x86_init.c b/arch/x86/kernel/x86_init.c
index ebfb8e4..cd6da6b 100644
--- a/arch/x86/kernel/x86_init.c
+++ b/arch/x86/kernel/x86_init.c
@@ -86,6 +86,7 @@
 };
 
 static void default_nmi_init(void) { };
+static int default_i8042_detect(void) { return 1; };
 
 struct x86_platform_ops x86_platform = {
 	.calibrate_tsc			= native_calibrate_tsc,
@@ -93,7 +94,8 @@
 	.set_wallclock			= mach_set_rtc_mmss,
 	.iommu_shutdown			= iommu_shutdown_noop,
 	.is_untracked_pat_range		= is_ISA_range,
-	.nmi_init			= default_nmi_init
+	.nmi_init			= default_nmi_init,
+	.i8042_detect			= default_i8042_detect
 };
 
 EXPORT_SYMBOL_GPL(x86_platform);