Commit 5495a415 authored by Joshua Clayton's avatar Joshua Clayton Committed by Alexandre Belloni

rtc: implement a sysfs interface for clock offset

clock offset may be set and read in decimal parts per billion
attribute is /sys/class/rtc/rtcN/offset
The attribute is only visible for rtcs that have set_offset implemented.
Signed-off-by: default avatarJoshua Clayton <stillcompiling@gmail.com>
Signed-off-by: default avatarAlexandre Belloni <alexandre.belloni@free-electrons.com>
parent b3967067
...@@ -157,6 +157,12 @@ wakealarm: The time at which the clock will generate a system wakeup ...@@ -157,6 +157,12 @@ wakealarm: The time at which the clock will generate a system wakeup
the epoch by default, or if there's a leading +, seconds in the the epoch by default, or if there's a leading +, seconds in the
future, or if there is a leading +=, seconds ahead of the current future, or if there is a leading +=, seconds ahead of the current
alarm. alarm.
offset: The amount which the rtc clock has been adjusted in firmware.
Visible only if the driver supports clock offset adjustment.
The unit is parts per billion, i.e. The number of clock ticks
which are added to or removed from the rtc's base clock per
billion ticks. A positive value makes a day pass more slowly,
longer, and a negative value makes a day pass more quickly.
IOCTL INTERFACE IOCTL INTERFACE
--------------- ---------------
......
...@@ -218,6 +218,34 @@ wakealarm_store(struct device *dev, struct device_attribute *attr, ...@@ -218,6 +218,34 @@ wakealarm_store(struct device *dev, struct device_attribute *attr,
} }
static DEVICE_ATTR_RW(wakealarm); static DEVICE_ATTR_RW(wakealarm);
static ssize_t
offset_show(struct device *dev, struct device_attribute *attr, char *buf)
{
ssize_t retval;
long offset;
retval = rtc_read_offset(to_rtc_device(dev), &offset);
if (retval == 0)
retval = sprintf(buf, "%ld\n", offset);
return retval;
}
static ssize_t
offset_store(struct device *dev, struct device_attribute *attr,
const char *buf, size_t n)
{
ssize_t retval;
long offset;
retval = kstrtol(buf, 10, &offset);
if (retval == 0)
retval = rtc_set_offset(to_rtc_device(dev), offset);
return (retval < 0) ? retval : n;
}
static DEVICE_ATTR_RW(offset);
static struct attribute *rtc_attrs[] = { static struct attribute *rtc_attrs[] = {
&dev_attr_name.attr, &dev_attr_name.attr,
&dev_attr_date.attr, &dev_attr_date.attr,
...@@ -226,6 +254,7 @@ static struct attribute *rtc_attrs[] = { ...@@ -226,6 +254,7 @@ static struct attribute *rtc_attrs[] = {
&dev_attr_max_user_freq.attr, &dev_attr_max_user_freq.attr,
&dev_attr_hctosys.attr, &dev_attr_hctosys.attr,
&dev_attr_wakealarm.attr, &dev_attr_wakealarm.attr,
&dev_attr_offset.attr,
NULL, NULL,
}; };
...@@ -249,9 +278,13 @@ static umode_t rtc_attr_is_visible(struct kobject *kobj, ...@@ -249,9 +278,13 @@ static umode_t rtc_attr_is_visible(struct kobject *kobj,
struct rtc_device *rtc = to_rtc_device(dev); struct rtc_device *rtc = to_rtc_device(dev);
umode_t mode = attr->mode; umode_t mode = attr->mode;
if (attr == &dev_attr_wakealarm.attr) if (attr == &dev_attr_wakealarm.attr) {
if (!rtc_does_wakealarm(rtc)) if (!rtc_does_wakealarm(rtc))
mode = 0; mode = 0;
} else if (attr == &dev_attr_offset.attr) {
if (!rtc->ops->set_offset)
mode = 0;
}
return mode; return mode;
} }
......
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