diff options
| -rw-r--r-- | drivers/rtc/rtc-sysfs.c | 103 |
1 files changed, 101 insertions, 2 deletions
diff --git a/drivers/rtc/rtc-sysfs.c b/drivers/rtc/rtc-sysfs.c index 2ddd0cf0714..899ab8c514f 100644 --- a/drivers/rtc/rtc-sysfs.c +++ b/drivers/rtc/rtc-sysfs.c @@ -78,6 +78,92 @@ static struct attribute_group rtc_attr_group = { .attrs = rtc_attrs, }; + +static ssize_t +rtc_sysfs_show_wakealarm(struct class_device *dev, char *buf) +{ + ssize_t retval; + unsigned long alarm; + struct rtc_wkalrm alm; + + /* Don't show disabled alarms; but the RTC could leave the + * alarm enabled after it's already triggered. Alarms are + * conceptually one-shot, even though some common hardware + * (PCs) doesn't actually work that way. + * + * REVISIT maybe we should require RTC implementations to + * disable the RTC alarm after it triggers, for uniformity. + */ + retval = rtc_read_alarm(dev, &alm); + if (retval == 0 && alm.enabled) { + rtc_tm_to_time(&alm.time, &alarm); + retval = sprintf(buf, "%lu\n", alarm); + } + + return retval; +} + +static ssize_t +rtc_sysfs_set_wakealarm(struct class_device *dev, const char *buf, size_t n) +{ + ssize_t retval; + unsigned long now, alarm; + struct rtc_wkalrm alm; + + /* Only request alarms that trigger in the future. Disable them + * by writing another time, e.g. 0 meaning Jan 1 1970 UTC. + */ + retval = rtc_read_time(dev, &alm.time); + if (retval < 0) + return retval; + rtc_tm_to_time(&alm.time, &now); + + alarm = simple_strtoul(buf, NULL, 0); + if (alarm > now) { + /* Avoid accidentally clobbering active alarms; we can't + * entirely prevent that here, without even the minimal + * locking from the /dev/rtcN api. + */ + retval = rtc_read_alarm(dev, &alm); + if (retval < 0) + return retval; + if (alm.enabled) + return -EBUSY; + + alm.enabled = 1; + } else { + alm.enabled = 0; + + /* Provide a valid future alarm time. Linux isn't EFI, + * this time won't be ignored when disabling the alarm. + */ + alarm = now + 300; + } + rtc_time_to_tm(alarm, &alm.time); + + retval = rtc_set_alarm(dev, &alm); + return (retval < 0) ? retval : n; +} +static const CLASS_DEVICE_ATTR(wakealarm, S_IRUGO | S_IWUSR, + rtc_sysfs_show_wakealarm, rtc_sysfs_set_wakealarm); + + +/* The reason to trigger an alarm with no process watching it (via sysfs) + * is its side effect: waking from a system state like suspend-to-RAM or + * suspend-to-disk. So: no attribute unless that side effect is possible. + * (Userspace may disable that mechanism later.) + */ +static inline int rtc_does_wakealarm(struct class_device *class_dev) +{ + struct rtc_device *rtc; + + if (!device_can_wakeup(class_dev->dev)) + return 0; + rtc = to_rtc_device(class_dev); + return rtc->ops->set_alarm != NULL; +} + + static int rtc_sysfs_add_device(struct class_device *class_dev, struct class_interface *class_intf) { @@ -87,8 +173,18 @@ static int rtc_sysfs_add_device(struct class_device *class_dev, err = sysfs_create_group(&class_dev->kobj, &rtc_attr_group); if (err) - dev_err(class_dev->dev, - "failed to create sysfs attributes\n"); + dev_err(class_dev->dev, "failed to create %s\n", + "sysfs attributes"); + else if (rtc_does_wakealarm(class_dev)) { + /* not all RTCs support both alarms and wakeup */ + err = class_device_create_file(class_dev, + &class_device_attr_wakealarm); + if (err) { + dev_err(class_dev->dev, "failed to create %s\n", + "alarm attribute"); + sysfs_remove_group(&class_dev->kobj, &rtc_attr_group); + } + } return err; } @@ -96,6 +192,9 @@ static int rtc_sysfs_add_device(struct class_device *class_dev, static void rtc_sysfs_remove_device(struct class_device *class_dev, struct class_interface *class_intf) { + if (rtc_does_wakealarm(class_dev)) + class_device_remove_file(class_dev, + &class_device_attr_wakealarm); sysfs_remove_group(&class_dev->kobj, &rtc_attr_group); } |