2 * RTC subsystem, sysfs interface
4 * Copyright (C) 2005 Tower Technologies
5 * Author: Alessandro Zummo <a.zummo@towertech.it>
7 * This program is free software; you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License version 2 as
9 * published by the Free Software Foundation.
12 #include <linux/module.h>
13 #include <linux/rtc.h>
18 /* device attributes */
21 * NOTE: RTC times displayed in sysfs use the RTC's timezone. That's
22 * ideally UTC. However, PCs that also boot to MS-Windows normally use
23 * the local time and change to match daylight savings time. That affects
24 * attributes including date, time, since_epoch, and wakealarm.
28 rtc_sysfs_show_name(struct device *dev, struct device_attribute *attr,
31 return sprintf(buf, "%s\n", to_rtc_device(dev)->name);
35 rtc_sysfs_show_date(struct device *dev, struct device_attribute *attr,
41 retval = rtc_read_time(to_rtc_device(dev), &tm);
43 retval = sprintf(buf, "%04d-%02d-%02d\n",
44 tm.tm_year + 1900, tm.tm_mon + 1, tm.tm_mday);
51 rtc_sysfs_show_time(struct device *dev, struct device_attribute *attr,
57 retval = rtc_read_time(to_rtc_device(dev), &tm);
59 retval = sprintf(buf, "%02d:%02d:%02d\n",
60 tm.tm_hour, tm.tm_min, tm.tm_sec);
67 rtc_sysfs_show_since_epoch(struct device *dev, struct device_attribute *attr,
73 retval = rtc_read_time(to_rtc_device(dev), &tm);
76 rtc_tm_to_time(&tm, &time);
77 retval = sprintf(buf, "%lu\n", time);
84 rtc_sysfs_show_max_user_freq(struct device *dev, struct device_attribute *attr,
87 return sprintf(buf, "%d\n", to_rtc_device(dev)->max_user_freq);
91 rtc_sysfs_set_max_user_freq(struct device *dev, struct device_attribute *attr,
92 const char *buf, size_t n)
94 struct rtc_device *rtc = to_rtc_device(dev);
95 unsigned long val = simple_strtoul(buf, NULL, 0);
97 if (val >= 4096 || val == 0)
100 rtc->max_user_freq = (int)val;
105 static struct device_attribute rtc_attrs[] = {
106 __ATTR(name, S_IRUGO, rtc_sysfs_show_name, NULL),
107 __ATTR(date, S_IRUGO, rtc_sysfs_show_date, NULL),
108 __ATTR(time, S_IRUGO, rtc_sysfs_show_time, NULL),
109 __ATTR(since_epoch, S_IRUGO, rtc_sysfs_show_since_epoch, NULL),
110 __ATTR(max_user_freq, S_IRUGO | S_IWUSR, rtc_sysfs_show_max_user_freq,
111 rtc_sysfs_set_max_user_freq),
116 rtc_sysfs_show_wakealarm(struct device *dev, struct device_attribute *attr,
121 struct rtc_wkalrm alm;
123 /* Don't show disabled alarms. For uniformity, RTC alarms are
124 * conceptually one-shot, even though some common RTCs (on PCs)
125 * don't actually work that way.
127 * NOTE: RTC implementations where the alarm doesn't match an
128 * exact YYYY-MM-DD HH:MM[:SS] date *must* disable their RTC
129 * alarms after they trigger, to ensure one-shot semantics.
131 retval = rtc_read_alarm(to_rtc_device(dev), &alm);
132 if (retval == 0 && alm.enabled) {
133 rtc_tm_to_time(&alm.time, &alarm);
134 retval = sprintf(buf, "%lu\n", alarm);
141 rtc_sysfs_set_wakealarm(struct device *dev, struct device_attribute *attr,
142 const char *buf, size_t n)
145 unsigned long now, alarm;
146 struct rtc_wkalrm alm;
147 struct rtc_device *rtc = to_rtc_device(dev);
151 /* Only request alarms that trigger in the future. Disable them
152 * by writing another time, e.g. 0 meaning Jan 1 1970 UTC.
154 retval = rtc_read_time(rtc, &alm.time);
157 rtc_tm_to_time(&alm.time, &now);
159 buf_ptr = (char *)buf;
160 if (*buf_ptr == '+') {
164 alarm = simple_strtoul(buf_ptr, NULL, 0);
169 /* Avoid accidentally clobbering active alarms; we can't
170 * entirely prevent that here, without even the minimal
171 * locking from the /dev/rtcN api.
173 retval = rtc_read_alarm(rtc, &alm);
183 /* Provide a valid future alarm time. Linux isn't EFI,
184 * this time won't be ignored when disabling the alarm.
188 rtc_time_to_tm(alarm, &alm.time);
190 retval = rtc_set_alarm(rtc, &alm);
191 return (retval < 0) ? retval : n;
193 static DEVICE_ATTR(wakealarm, S_IRUGO | S_IWUSR,
194 rtc_sysfs_show_wakealarm, rtc_sysfs_set_wakealarm);
197 /* The reason to trigger an alarm with no process watching it (via sysfs)
198 * is its side effect: waking from a system state like suspend-to-RAM or
199 * suspend-to-disk. So: no attribute unless that side effect is possible.
200 * (Userspace may disable that mechanism later.)
202 static inline int rtc_does_wakealarm(struct rtc_device *rtc)
204 if (!device_can_wakeup(rtc->dev.parent))
206 return rtc->ops->set_alarm != NULL;
210 void rtc_sysfs_add_device(struct rtc_device *rtc)
214 /* not all RTCs support both alarms and wakeup */
215 if (!rtc_does_wakealarm(rtc))
218 err = device_create_file(&rtc->dev, &dev_attr_wakealarm);
220 dev_err(rtc->dev.parent,
221 "failed to create alarm attribute, %d\n", err);
224 void rtc_sysfs_del_device(struct rtc_device *rtc)
226 /* REVISIT did we add it successfully? */
227 if (rtc_does_wakealarm(rtc))
228 device_remove_file(&rtc->dev, &dev_attr_wakealarm);
231 void __init rtc_sysfs_init(struct class *rtc_class)
233 rtc_class->dev_attrs = rtc_attrs;