linux-kernel - [PATCH v2] alarmtimer: check RTC features instead of ops

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Date:   Tue, 11 May 2021 03:45:16 +0200
From:   Alexandre Belloni <alexandre.belloni@...tlin.com>
To:     John Stultz <john.stultz@...aro.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Stephen Boyd <sboyd@...nel.org>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>
Cc:     linux-kernel@...r.kernel.org
Subject: [PATCH v2] 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@...tlin.com>
---
 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 bea9d08b1698..5897828b9d7e 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;
-- 
2.31.1