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Subject[PATCH 1/2] rtc: Add RTC range
Date
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>
---
Documentation/ABI/testing/sysfs-class-rtc | 8 ++++++++
drivers/rtc/interface.c | 14 ++++++++++++++
drivers/rtc/rtc-sysfs.c | 12 ++++++++++++
include/linux/rtc.h | 3 +++
4 files changed, 37 insertions(+)

diff --git a/Documentation/ABI/testing/sysfs-class-rtc b/Documentation/ABI/testing/sysfs-class-rtc
index 792a38300336..95984289a4ee 100644
--- 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 7e253be19ba7..c068daebeec2 100644
--- 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 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;
diff --git a/include/linux/rtc.h b/include/linux/rtc.h
index 3b65b201169c..c78528c394e5 100644
--- 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;
--
2.16.2
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