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authorMatthew Garrett <mjg59@srcf.ucam.org>2009-09-23 03:46:32 +0400
committerLinus Torvalds <torvalds@linux-foundation.org>2009-09-23 18:39:46 +0400
commitd8c1acb1664d17dd995e34507533321e986d9215 (patch)
tree5c8c8a60bc0da9f16a748c6ef8c3cb98f33d21be
parentea3d1606fd32059461309099e8856c6652888a79 (diff)
downloadlinux-d8c1acb1664d17dd995e34507533321e986d9215.tar.xz
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: 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>
-rw-r--r--Documentation/rtc.txt2
-rw-r--r--drivers/rtc/rtc-sysfs.c14
2 files changed, 16 insertions, 0 deletions
diff --git a/Documentation/rtc.txt b/Documentation/rtc.txt
index 2745e8197fde..9104c1062084 100644
--- a/Documentation/rtc.txt
+++ b/Documentation/rtc.txt
@@ -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
diff --git a/drivers/rtc/rtc-sysfs.c b/drivers/rtc/rtc-sysfs.c
index 2531ce4c9db0..7dd23a6fc825 100644
--- a/drivers/rtc/rtc-sysfs.c
+++ b/drivers/rtc/rtc-sysfs.c
@@ -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),
{ },
};