rtc: Add RTC range

Add a way for drivers to inform the core of the supported date/time range.
The core can then check whether the date/time or alarm is in the range
before calling ->set_time, ->set_mmss or ->set_alarm. It returns -ERANGE
when the time is out of range.

Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

1 files changed, 12 insertions, 0 deletions

diff --git a/drivers/rtc/rtc-sysfs.c b/drivers/rtc/rtc-sysfs.c
index 92ff2edb86a6..454da38c6012 100644
--- a/drivers/rtc/rtc-sysfs.c
+++ b/drivers/rtc/rtc-sysfs.c
@@ -248,6 +248,14 @@ offset_store(struct device *dev, struct device_attribute *attr,
 }
 static DEVICE_ATTR_RW(offset);
 
+static ssize_t
+range_show(struct device *dev, struct device_attribute *attr, char *buf)
+{
+        return sprintf(buf, "[%lld,%llu]\n", to_rtc_device(dev)->range_min,
+                       to_rtc_device(dev)->range_max);
+}
+static DEVICE_ATTR_RO(range);
+
 static struct attribute *rtc_attrs[] = {
         &dev_attr_name.attr,
         &dev_attr_date.attr,
@@ -257,6 +265,7 @@ static struct attribute *rtc_attrs[] = {
         &dev_attr_hctosys.attr,
         &dev_attr_wakealarm.attr,
         &dev_attr_offset.attr,
+        &dev_attr_range.attr,
         NULL,
 };
 
@@ -286,6 +295,9 @@ static umode_t rtc_attr_is_visible(struct kobject *kobj,
         } else if (attr == &dev_attr_offset.attr) {
                 if (!rtc->ops->set_offset)
                         mode = 0;
+        } else if (attr == &dev_attr_range.attr) {
+                if (!(rtc->range_max - rtc->range_min))
+                        mode = 0;
         }
 
         return mode;