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

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

Documentation/rtc.txt

+2 −0
Original line number Diff line number Diff line
@@ -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

drivers/rtc/rtc-sysfs.c

+14 −0
Original line number Diff line number Diff line
@@ -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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