clockevents: Implement unbind functionality

Provide a sysfs interface to allow unbinding of clockevent
devices. The device is unbound if it is unused or if there is a
replacement device available. Unbinding of broadcast devices is not
supported as we don't want to foster that nonsense. If no replacement
device is available the unbind returns -EBUSY. Unbind is available
from the kernel and through sysfs, which is necessary to drop the
module refcount.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Magnus Damm <magnus.damm@gmail.com>
Link: http://lkml.kernel.org/r/20130425143436.499216659@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 5 insertions, 4 deletions

diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c
index 31b90332f47b..6d05b00410cc 100644
--- a/kernel/time/clocksource.c
+++ b/kernel/time/clocksource.c
@@ -31,6 +31,8 @@
 #include <linux/tick.h>
 #include <linux/kthread.h>
 
+#include "tick-internal.h"
+
 void timecounter_init(struct timecounter *tc,
 		      const struct cyclecounter *cc,
 		      u64 start_tstamp)
@@ -174,7 +176,6 @@ clocks_calc_mult_shift(u32 *mult, u32 *shift, u32 from, u32 to, u32 maxsec)
 static struct clocksource *curr_clocksource;
 static LIST_HEAD(clocksource_list);
 static DEFINE_MUTEX(clocksource_mutex);
-#define CS_NAME_LEN		32
 static char override_name[CS_NAME_LEN];
 static int finished_booting;
 
@@ -864,7 +865,7 @@ sysfs_show_current_clocksources(struct device *dev,
 	return count;
 }
 
-static size_t clocksource_get_uname(const char *buf, char *dst, size_t cnt)
+size_t sysfs_get_uname(const char *buf, char *dst, size_t cnt)
 {
 	size_t ret = cnt;
 
@@ -899,7 +900,7 @@ static ssize_t sysfs_override_clocksource(struct device *dev,
 
 	mutex_lock(&clocksource_mutex);
 
-	ret = clocksource_get_uname(buf, override_name, count);
+	ret = sysfs_get_uname(buf, override_name, count);
 	if (ret >= 0)
 		clocksource_select();
 
@@ -925,7 +926,7 @@ static ssize_t sysfs_unbind_clocksource(struct device *dev,
 	char name[CS_NAME_LEN];
 	size_t ret;
 
-	ret = clocksource_get_uname(buf, name, count);
+	ret = sysfs_get_uname(buf, name, count);
 	if (ret < 0)
 		return ret;