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>

diff --git a/Documentation/ABI/testing/sysfs-class-rtc b/Documentation/ABI/testing/sysfs-class-rtc
index 792a383..9598428 100644 (file)
--- a/Documentation/ABI/testing/sysfs-class-rtc
+++ b/Documentation/ABI/testing/sysfs-class-rtc
@@ -43,6 +43,14 @@ Contact:     linux-rtc@vger.kernel.org
 Description:
                (RO) The name of the RTC corresponding to this sysfs directory
 
+What:          /sys/class/rtc/rtcX/range
+Date:          January 2018
+KernelVersion: 4.16
+Contact:       linux-rtc@vger.kernel.org
+Description:
+               Valid time range for the RTC, as seconds from epoch, formatted
+               as [min, max]
+
 What:          /sys/class/rtc/rtcX/since_epoch
 Date:          March 2006
 KernelVersion: 2.6.17

diff --git a/drivers/rtc/interface.c b/drivers/rtc/interface.c
index 7e253be..c068dae 100644 (file)
--- a/drivers/rtc/interface.c
+++ b/drivers/rtc/interface.c
@@ -70,6 +70,13 @@ int rtc_set_time(struct rtc_device *rtc, struct rtc_time *tm)
        if (err != 0)
                return err;
 
+       if (rtc->range_min != rtc->range_max) {
+               time64_t time = rtc_tm_to_time64(tm);
+
+               if (time < rtc->range_min || time > rtc->range_max)
+                       return -ERANGE;
+       }
+
        err = mutex_lock_interruptible(&rtc->ops_lock);
        if (err)
                return err;
@@ -374,6 +381,13 @@ int rtc_set_alarm(struct rtc_device *rtc, struct rtc_wkalrm *alarm)
        if (err != 0)
                return err;
 
+       if (rtc->range_min != rtc->range_max) {
+               time64_t time = rtc_tm_to_time64(&alarm->time);
+
+               if (time < rtc->range_min || time > rtc->range_max)
+                       return -ERANGE;
+       }
+
        err = mutex_lock_interruptible(&rtc->ops_lock);
        if (err)
                return err;

diff --git a/drivers/rtc/rtc-sysfs.c b/drivers/rtc/rtc-sysfs.c
index 92ff2ed..454da38 100644 (file)
--- 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;

diff --git a/include/linux/rtc.h b/include/linux/rtc.h
index 3b65b20..c78528c 100644 (file)
--- a/include/linux/rtc.h
+++ b/include/linux/rtc.h
@@ -150,6 +150,9 @@ struct rtc_device {
        bool nvram_old_abi;
        struct bin_attribute *nvram;
 
+       time64_t range_min;
+       timeu64_t range_max;
+
 #ifdef CONFIG_RTC_INTF_DEV_UIE_EMUL
        struct work_struct uie_task;
        struct timer_list uie_timer;