[PATCH 2/2] [RTC] : Add the support for alarm time relative to current time in sysfs

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Subject: RTC: Add the support for alarm time relative to current time in sysfs
>From : Zhao Yakui <yakui.zhao@xxxxxxxxx>

In current kernel if we want to set the alarm time, the absolute time
the seconds relative to 1970-01-01 00:00:00) should be written into 
/sys/class/rtc/rtc0/wakealarm. It is not convenient.

It is more reasonable to add the support for the alarm time 
relative to current RTC time.(the unit is second)
For example: 
If the RTC is required to generate alarm after 2 minutes, the following will
be OK.
	echo +120 > /sys/class/rtc/rtc0/wakealarm
or      echo +0x78 > /sys/class/rtc/rtc0/wakealarm


Signed-off-by: Zhao Yakui <yakui.zhao@xxxxxxxxx>
Signed-off-by: Zhang Rui  <rui.zhang@xxxxxxxxx>

---
 drivers/rtc/rtc-sysfs.c |   12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

Index: linux-2.6/drivers/rtc/rtc-sysfs.c
===================================================================
--- linux-2.6.orig/drivers/rtc/rtc-sysfs.c
+++ linux-2.6/drivers/rtc/rtc-sysfs.c
@@ -145,6 +145,8 @@ rtc_sysfs_set_wakealarm(struct device *d
 	unsigned long now, alarm;
 	struct rtc_wkalrm alm;
 	struct rtc_device *rtc = to_rtc_device(dev);
+	char *buf_ptr;
+	int adjust = 0;
 
 	/* Only request alarms that trigger in the future.  Disable them
 	 * by writing another time, e.g. 0 meaning Jan 1 1970 UTC.
@@ -154,7 +156,15 @@ rtc_sysfs_set_wakealarm(struct device *d
 		return retval;
 	rtc_tm_to_time(&alm.time, &now);
 
-	alarm = simple_strtoul(buf, NULL, 0);
+	buf_ptr = (char *)buf;
+	if (*buf_ptr == '+') {
+		buf_ptr++;
+		adjust = 1;
+	}
+	alarm = simple_strtoul(buf_ptr, NULL, 0);
+	if (adjust) {
+		alarm += now;
+	}
 	if (alarm > now) {
 		/* Avoid accidentally clobbering active alarms; we can't
 		 * entirely prevent that here, without even the minimal


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