clocksource: Split out user string input

Split out the user string input for clocksource override. Preparatory
patch for unbind.

[ jstultz: Fix an off by one error ]

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/20130425143435.895851338@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 23 insertions, 14 deletions

diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c
index 9782997cb6cf..d7f1a45c2fa5 100644
--- a/kernel/time/clocksource.c
+++ b/kernel/time/clocksource.c
@@ -174,7 +174,8 @@ 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);
-static char override_name[32];
+#define CS_NAME_LEN             32
+static char override_name[CS_NAME_LEN];
 static int finished_booting;
 
 #ifdef CONFIG_CLOCKSOURCE_WATCHDOG
@@ -838,6 +839,23 @@ 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 ret = cnt;
+
+        /* strings from sysfs write are not 0 terminated! */
+        if (!cnt || cnt >= CS_NAME_LEN)
+                return -EINVAL;
+
+        /* strip of \n: */
+        if (buf[cnt-1] == '\n')
+                cnt--;
+        if (cnt > 0)
+                memcpy(dst, buf, cnt);
+        dst[cnt] = 0;
+        return ret;
+}
+
 /**
  * sysfs_override_clocksource - interface for manually overriding clocksource
  * @dev:        unused
@@ -852,22 +870,13 @@ static ssize_t sysfs_override_clocksource(struct device *dev,
                                           struct device_attribute *attr,
                                           const char *buf, size_t count)
 {
-        size_t ret = count;
-
-        /* strings from sysfs write are not 0 terminated! */
-        if (count >= sizeof(override_name))
-                return -EINVAL;
-
-        /* strip of \n: */
-        if (buf[count-1] == '\n')
-                count--;
+        size_t ret;
 
         mutex_lock(&clocksource_mutex);
 
-        if (count > 0)
-                memcpy(override_name, buf, count);
-        override_name[count] = 0;
-        clocksource_select();
+        ret = clocksource_get_uname(buf, override_name, count);
+        if (ret >= 0)
+                clocksource_select();
 
         mutex_unlock(&clocksource_mutex);