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/include/linux/clocksource.h b/include/linux/clocksource.h
index 573819ef..0d96cde 100644
--- a/include/linux/clocksource.h
+++ b/include/linux/clocksource.h
@@ -143,7 +143,7 @@
  *			400-499: Perfect
  *				The ideal clocksource. A must-use where
  *				available.
- * @read:		returns a cycle value
+ * @read:		returns a cycle value, passes clocksource as argument
  * @mask:		bitmask for two's complement
  *			subtraction of non 64 bit counters
  * @mult:		cycle to nanosecond multiplier (adjusted by NTP)
@@ -162,7 +162,7 @@
 	char *name;
 	struct list_head list;
 	int rating;
-	cycle_t (*read)(void);
+	cycle_t (*read)(struct clocksource *cs);
 	cycle_t mask;
 	u32 mult;
 	u32 mult_orig;
@@ -271,7 +271,7 @@
  */
 static inline cycle_t clocksource_read(struct clocksource *cs)
 {
-	return cs->read();
+	return cs->read(cs);
 }
 
 /**