[tip: timers/urgent] alarmtimer: Check RTC features instead of ops

[tip-bot2 for Alexandre Belloni]

The following commit has been merged into the timers/urgent branch of tip:

Commit-ID:     e09784a8a751e539dffc94d43bc917b0ac1e934a
Gitweb:        https://git.kernel.org/tip/e09784a8a751e539dffc94d43bc917b0ac1e934a
Author:        Alexandre Belloni <alexandre.belloni@xxxxxxxxxxx>
AuthorDate:    Tue, 11 May 2021 03:45:16 +02:00
Committer:     Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitterDate: Tue, 11 May 2021 21:28:04 +02:00

alarmtimer: Check RTC features instead of ops

RTC drivers used to leave .set_alarm() NULL in order to signal the RTC
device doesn't support alarms. The drivers are now clearing the
RTC_FEATURE_ALARM bit for that purpose in order to keep the rtc_class_ops
structure const. So now, .set_alarm() is set unconditionally and this
possibly causes the alarmtimer code to select an RTC device that doesn't
support alarms.

Test RTC_FEATURE_ALARM instead of relying on ops->set_alarm to determine
whether alarms are available.

Fixes: 7ae41220ef58 ("rtc: introduce features bitfield")
Signed-off-by: Alexandre Belloni <alexandre.belloni@xxxxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Link: https://lore.kernel.org/r/20210511014516.563031-1-alexandre.belloni@xxxxxxxxxxx

---
 kernel/time/alarmtimer.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/time/alarmtimer.c b/kernel/time/alarmtimer.c
index bea9d08..5897828 100644
--- a/kernel/time/alarmtimer.c
+++ b/kernel/time/alarmtimer.c
@@ -92,7 +92,7 @@ static int alarmtimer_rtc_add_device(struct device *dev,
 	if (rtcdev)
 		return -EBUSY;
 
-	if (!rtc->ops->set_alarm)
+	if (!test_bit(RTC_FEATURE_ALARM, rtc->features))
 		return -1;
 	if (!device_may_wakeup(rtc->dev.parent))
 		return -1;