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 name_show(struct device *dev, struct device_attribute *attr, char *buf)
30 return sprintf(buf, "%s\n", to_rtc_device(dev)->name);
32 static DEVICE_ATTR_RO(name);
35 date_show(struct device *dev, struct device_attribute *attr, char *buf)
40 retval = rtc_read_time(to_rtc_device(dev), &tm);
42 retval = sprintf(buf, "%04d-%02d-%02d\n",
43 tm.tm_year + 1900, tm.tm_mon + 1, tm.tm_mday);
48 static DEVICE_ATTR_RO(date);
51 time_show(struct device *dev, struct device_attribute *attr, char *buf)
56 retval = rtc_read_time(to_rtc_device(dev), &tm);
58 retval = sprintf(buf, "%02d:%02d:%02d\n",
59 tm.tm_hour, tm.tm_min, tm.tm_sec);
64 static DEVICE_ATTR_RO(time);
67 since_epoch_show(struct device *dev, struct device_attribute *attr, char *buf)
72 retval = rtc_read_time(to_rtc_device(dev), &tm);
75 rtc_tm_to_time(&tm, &time);
76 retval = sprintf(buf, "%lu\n", time);
81 static DEVICE_ATTR_RO(since_epoch);
84 max_user_freq_show(struct device *dev, struct device_attribute *attr, char *buf)
86 return sprintf(buf, "%d\n", to_rtc_device(dev)->max_user_freq);
90 max_user_freq_store(struct device *dev, struct device_attribute *attr,
91 const char *buf, size_t n)
93 struct rtc_device *rtc = to_rtc_device(dev);
94 unsigned long val = simple_strtoul(buf, NULL, 0);
96 if (val >= 4096 || val == 0)
99 rtc->max_user_freq = (int)val;
103 static DEVICE_ATTR_RW(max_user_freq);
106 * rtc_sysfs_show_hctosys - indicate if the given RTC set the system time
108 * Returns 1 if the system clock was set by this RTC at the last
109 * boot or resume event.
112 hctosys_show(struct device *dev, struct device_attribute *attr, char *buf)
114 #ifdef CONFIG_RTC_HCTOSYS_DEVICE
115 if (rtc_hctosys_ret == 0 &&
116 strcmp(dev_name(&to_rtc_device(dev)->dev),
117 CONFIG_RTC_HCTOSYS_DEVICE) == 0)
118 return sprintf(buf, "1\n");
121 return sprintf(buf, "0\n");
123 static DEVICE_ATTR_RO(hctosys);
125 static struct attribute *rtc_attrs[] = {
129 &dev_attr_since_epoch.attr,
130 &dev_attr_max_user_freq.attr,
131 &dev_attr_hctosys.attr,
134 ATTRIBUTE_GROUPS(rtc);
137 rtc_sysfs_show_wakealarm(struct device *dev, struct device_attribute *attr,
142 struct rtc_wkalrm alm;
144 /* Don't show disabled alarms. For uniformity, RTC alarms are
145 * conceptually one-shot, even though some common RTCs (on PCs)
146 * don't actually work that way.
148 * NOTE: RTC implementations where the alarm doesn't match an
149 * exact YYYY-MM-DD HH:MM[:SS] date *must* disable their RTC
150 * alarms after they trigger, to ensure one-shot semantics.
152 retval = rtc_read_alarm(to_rtc_device(dev), &alm);
153 if (retval == 0 && alm.enabled) {
154 rtc_tm_to_time(&alm.time, &alarm);
155 retval = sprintf(buf, "%lu\n", alarm);
162 rtc_sysfs_set_wakealarm(struct device *dev, struct device_attribute *attr,
163 const char *buf, size_t n)
166 unsigned long now, alarm;
167 unsigned long push = 0;
168 struct rtc_wkalrm alm;
169 struct rtc_device *rtc = to_rtc_device(dev);
173 /* Only request alarms that trigger in the future. Disable them
174 * by writing another time, e.g. 0 meaning Jan 1 1970 UTC.
176 retval = rtc_read_time(rtc, &alm.time);
179 rtc_tm_to_time(&alm.time, &now);
181 buf_ptr = (char *)buf;
182 if (*buf_ptr == '+') {
184 if (*buf_ptr == '=') {
190 alarm = simple_strtoul(buf_ptr, NULL, 0);
194 if (alarm > now || push) {
195 /* Avoid accidentally clobbering active alarms; we can't
196 * entirely prevent that here, without even the minimal
197 * locking from the /dev/rtcN api.
199 retval = rtc_read_alarm(rtc, &alm);
204 rtc_tm_to_time(&alm.time, &push);
214 /* Provide a valid future alarm time. Linux isn't EFI,
215 * this time won't be ignored when disabling the alarm.
219 rtc_time_to_tm(alarm, &alm.time);
221 retval = rtc_set_alarm(rtc, &alm);
222 return (retval < 0) ? retval : n;
224 static DEVICE_ATTR(wakealarm, S_IRUGO | S_IWUSR,
225 rtc_sysfs_show_wakealarm, rtc_sysfs_set_wakealarm);
228 /* The reason to trigger an alarm with no process watching it (via sysfs)
229 * is its side effect: waking from a system state like suspend-to-RAM or
230 * suspend-to-disk. So: no attribute unless that side effect is possible.
231 * (Userspace may disable that mechanism later.)
233 static inline int rtc_does_wakealarm(struct rtc_device *rtc)
235 if (!device_can_wakeup(rtc->dev.parent))
237 return rtc->ops->set_alarm != NULL;
241 void rtc_sysfs_add_device(struct rtc_device *rtc)
245 /* not all RTCs support both alarms and wakeup */
246 if (!rtc_does_wakealarm(rtc))
249 err = device_create_file(&rtc->dev, &dev_attr_wakealarm);
251 dev_err(rtc->dev.parent,
252 "failed to create alarm attribute, %d\n", err);
255 void rtc_sysfs_del_device(struct rtc_device *rtc)
257 /* REVISIT did we add it successfully? */
258 if (rtc_does_wakealarm(rtc))
259 device_remove_file(&rtc->dev, &dev_attr_wakealarm);
262 void __init rtc_sysfs_init(struct class *rtc_class)
264 rtc_class->dev_groups = rtc_groups;