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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org,
        Alexandre Belloni <alexandre.belloni@bootlin.com>,
        Thomas Gleixner <tglx@linutronix.de>
Subject: [PATCH 5.12 327/363] alarmtimer: Check RTC features instead of ops
Date:   Mon, 17 May 2021 16:03:13 +0200
Message-Id: <20210517140313.662801818@linuxfoundation.org>
In-Reply-To: <20210517140302.508966430@linuxfoundation.org>
References: <20210517140302.508966430@linuxfoundation.org>
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From: Alexandre Belloni <alexandre.belloni@bootlin.com>

commit e09784a8a751e539dffc94d43bc917b0ac1e934a upstream.

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@bootlin.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20210511014516.563031-1-alexandre.belloni@bootlin.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 kernel/time/alarmtimer.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/kernel/time/alarmtimer.c
+++ b/kernel/time/alarmtimer.c
@@ -92,7 +92,7 @@ static int alarmtimer_rtc_add_device(str
 	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;