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rtc: add boot_timesource sysfs attribute

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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: Matthew Garrett <mjg@redhat.com>
Acked-by: Alessandro Zummo <a.zummo@towertech.it>
Cc: Mark Brown <broonie@opensource.wolfsonmicro.com>
Cc: David Brownell <david-b@pacbell.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Matthew Garrett
2009-09-22 16:46:32 -07:00
committed by Linus Torvalds
parent ea3d1606fd
commit d8c1acb166
2 changed files with 16 additions and 0 deletions
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14
drivers/rtc/rtc-sysfs.c
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@ -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),
{ },
};