clocksource: pass clocksource to read() callback

Pass clocksource pointer to the read() callback for clocksources.  This
allows us to share the callback between multiple instances.

[hugh@veritas.com: fix powerpc build of clocksource pass clocksource mods]
[akpm@linux-foundation.org: cleanup]
Signed-off-by: Magnus Damm <damm@igel.co.jp>
Acked-by: John Stultz <johnstul@us.ibm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/arch/x86/xen/time.c b/arch/x86/xen/time.c
index 14f2406..0a5aa44 100644
--- a/arch/x86/xen/time.c
+++ b/arch/x86/xen/time.c
@@ -213,6 +213,11 @@
 	return ret;
 }
 
+static cycle_t xen_clocksource_get_cycles(struct clocksource *cs)
+{
+	return xen_clocksource_read();
+}
+
 static void xen_read_wallclock(struct timespec *ts)
 {
 	struct shared_info *s = HYPERVISOR_shared_info;
@@ -241,7 +246,7 @@
 static struct clocksource xen_clocksource __read_mostly = {
 	.name = "xen",
 	.rating = 400,
-	.read = xen_clocksource_read,
+	.read = xen_clocksource_get_cycles,
 	.mask = ~0,
 	.mult = 1<<XEN_SHIFT,		/* time directly in nanoseconds */
 	.shift = XEN_SHIFT,