rtc: cmos: Do not export alarm rtc_ops when we do not support alarms

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[ Upstream commit fbb974ba69 ]

When there is no IRQ configured for the RTC, the rtc-cmos code does not
support alarms, all alarm rtc_ops fail with -EIO / -EINVAL.

The rtc-core expects a rtc driver which does not support rtc alarms to
not have alarm ops at all. Otherwise the wakealarm sysfs attr will read
as empty rather then returning an error, making it impossible for
userspace to find out beforehand if alarms are supported.

A system without an IRQ for the RTC before this patch:
[root@localhost ~]# cat /sys/class/rtc/rtc0/wakealarm
[root@localhost ~]#

After this patch:
[root@localhost ~]# cat /sys/class/rtc/rtc0/wakealarm
cat: /sys/class/rtc/rtc0/wakealarm: No such file or directory
[root@localhost ~]#

This fixes gnome-session + systemd trying to use suspend-then-hibernate,
which causes systemd to abort the suspend when writing the RTC alarm fails.

BugLink: https://github.com/systemd/systemd/issues/9988
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

...

This commit is contained in:

Hans de Goede 2018-09-04 16:51:29 +02:00 • committed by Greg Kroah-Hartman

parent 121f89dd70

commit b411f9463a

1 changed files with 12 additions and 4 deletions

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drivers/rtc/rtc-cmos.c

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