Commit d8c1acb1 authored by Matthew Garrett's avatar Matthew Garrett Committed by Linus Torvalds

rtc: add boot_timesource sysfs attribute

CONFIG_RTC_HCTOSYS allows the kernel to read the system time from the RTC
at boot and resume, avoiding the need for userspace to do so.
Unfortunately userspace currently has no way to know whether this
configuration option is enabled and thus cannot sensibly choose whether to
run hwclock itself or not.  Add a hctosys sysfs attribute which indicates
whether a given RTC set the system clock.
Signed-off-by: default avatarMatthew Garrett <mjg@redhat.com>
Acked-by: default avatarAlessandro Zummo <a.zummo@towertech.it>
Cc: Mark Brown <broonie@opensource.wolfsonmicro.com>
Cc: David Brownell <david-b@pacbell.net>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent ea3d1606
......@@ -143,6 +143,8 @@ rtc attributes without requiring the use of ioctls. All dates and times
are in the RTC's timezone, rather than in system time.
date: RTC-provided date
hctosys: 1 if the RTC provided the system time at boot via the
CONFIG_RTC_HCTOSYS kernel option, 0 otherwise
max_user_freq: The maximum interrupt rate an unprivileged user may request
from this RTC.
name: The name of the RTC corresponding to this sysfs directory
......
......@@ -102,6 +102,19 @@ rtc_sysfs_set_max_user_freq(struct device *dev, struct device_attribute *attr,
return n;
}
static ssize_t
rtc_sysfs_show_hctosys(struct device *dev, struct device_attribute *attr,
char *buf)
{
#ifdef CONFIG_RTC_HCTOSYS_DEVICE
if (strcmp(dev_name(&to_rtc_device(dev)->dev),
CONFIG_RTC_HCTOSYS_DEVICE) == 0)
return sprintf(buf, "1\n");
else
#endif
return sprintf(buf, "0\n");
}
static struct device_attribute rtc_attrs[] = {
__ATTR(name, S_IRUGO, rtc_sysfs_show_name, NULL),
__ATTR(date, S_IRUGO, rtc_sysfs_show_date, NULL),
......@@ -109,6 +122,7 @@ static struct device_attribute rtc_attrs[] = {
__ATTR(since_epoch, S_IRUGO, rtc_sysfs_show_since_epoch, NULL),
__ATTR(max_user_freq, S_IRUGO | S_IWUSR, rtc_sysfs_show_max_user_freq,
rtc_sysfs_set_max_user_freq),
__ATTR(hctosys, S_IRUGO, rtc_sysfs_show_hctosys, NULL),
{ },
};
......
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