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Subject[PATCH 10/12] clocksource: add block notifier
Adds a call back interface for register/rating change events. This is also used
later in this series to signal other interesting events.


Signed-Off-By: Daniel Walker <dwalker@mvista.com>

---
include/linux/clocksource.h | 37 +++++++++++++++++++++++++++++++++++++
include/linux/timekeeping.h | 3 +++
kernel/time/clocksource.c | 10 ++++++++++
3 files changed, 50 insertions(+)
Index: linux-2.6.19/include/linux/clocksource.h
===================================================================
--- linux-2.6.19.orig/include/linux/clocksource.h
+++ linux-2.6.19/include/linux/clocksource.h
@@ -14,6 +14,7 @@
#include <linux/list.h>
#include <linux/plist.h>
#include <linux/sysdev.h>
+#include <linux/notifier.h>

#include <asm/div64.h>
#include <asm/io.h>
@@ -24,6 +25,42 @@ typedef u64 cycle_t;
/* XXX - Would like a better way for initializing curr_clocksource */
extern struct clocksource clocksource_jiffies;

+/*
+ * Allows inlined calling for notifier routines.
+ */
+extern struct atomic_notifier_head clocksource_list_notifier;
+
+/*
+ * Block notifier flags.
+ */
+#define CLOCKSOURCE_NOTIFY_REGISTER 1
+#define CLOCKSOURCE_NOTIFY_RATING 2
+#define CLOCKSOURCE_NOTIFY_FREQ 4
+
+/**
+ * clocksource_notifier_register - Registers a list change notifier
+ * @nb: pointer to a notifier block
+ *
+ * Returns zero always.
+ */
+static inline int clocksource_notifier_register(struct notifier_block *nb)
+{
+ return atomic_notifier_chain_register(&clocksource_list_notifier, nb);
+}
+
+/**
+ * clocksource_freq_change - Allows notification of dynamic frequency changes.
+ *
+ * Signals that a clocksource is dynamically changing it's frequency.
+ * This could happen if a clocksource becomes more/less stable.
+ */
+static inline void clocksource_freq_change(struct clocksource *c)
+{
+ atomic_notifier_call_chain(&clocksource_list_notifier,
+ CLOCKSOURCE_NOTIFY_FREQ, c);
+}
+
+
/**
* struct clocksource - hardware abstraction for a free running counter
* Provides mostly state-free accessors to the underlying hardware.
Index: linux-2.6.19/include/linux/timekeeping.h
===================================================================
--- linux-2.6.19.orig/include/linux/timekeeping.h
+++ linux-2.6.19/include/linux/timekeeping.h
@@ -14,6 +14,9 @@ static inline int change_clocksource(voi
{
return 0;
}
+
+static inline void change_clocksource(void) { }
+
#endif /* !CONFIG_GENERIC_TIME */

#endif /* _LINUX_TIMEKEEPING_H */
Index: linux-2.6.19/kernel/time/clocksource.c
===================================================================
--- linux-2.6.19.orig/kernel/time/clocksource.c
+++ linux-2.6.19/kernel/time/clocksource.c
@@ -49,6 +49,8 @@ static DEFINE_SPINLOCK(clocksource_lock)
static char override_name[32];
static int finished_booting;

+ATOMIC_NOTIFIER_HEAD(clocksource_list_notifier);
+
/* clocksource_done_booting - Called near the end of bootup
*
* Hack to avoid lots of clocksource churn at boot time
@@ -196,6 +198,10 @@ int clocksource_register(struct clocksou
next_clocksource = select_clocksource();
}
spin_unlock_irqrestore(&clocksource_lock, flags);
+
+ atomic_notifier_call_chain(&clocksource_list_notifier,
+ CLOCKSOURCE_NOTIFY_REGISTER, c);
+
return ret;
}
EXPORT_SYMBOL(clocksource_register);
@@ -224,6 +230,10 @@ void clocksource_rating_change(struct cl

next_clocksource = select_clocksource();
spin_unlock_irqrestore(&clocksource_lock, flags);
+
+ atomic_notifier_call_chain(&clocksource_list_notifier,
+ CLOCKSOURCE_NOTIFY_RATING, c);
+
}
EXPORT_SYMBOL(clocksource_rating_change);

--
-
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