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 %s\n", dev_driver_string(dev->parent),
31 dev_name(dev->parent));
33 static DEVICE_ATTR_RO(name);
36 date_show(struct device *dev, struct device_attribute *attr, char *buf)
41 retval = rtc_read_time(to_rtc_device(dev), &tm);
45 return sprintf(buf, "%ptRd\n", &tm);
47 static DEVICE_ATTR_RO(date);
50 time_show(struct device *dev, struct device_attribute *attr, char *buf)
55 retval = rtc_read_time(to_rtc_device(dev), &tm);
59 return sprintf(buf, "%ptRt\n", &tm);
61 static DEVICE_ATTR_RO(time);
64 since_epoch_show(struct device *dev, struct device_attribute *attr, char *buf)
69 retval = rtc_read_time(to_rtc_device(dev), &tm);
73 time = rtc_tm_to_time64(&tm);
74 retval = sprintf(buf, "%lld\n", time);
79 static DEVICE_ATTR_RO(since_epoch);
82 max_user_freq_show(struct device *dev, struct device_attribute *attr, char *buf)
84 return sprintf(buf, "%d\n", to_rtc_device(dev)->max_user_freq);
88 max_user_freq_store(struct device *dev, struct device_attribute *attr,
89 const char *buf, size_t n)
91 struct rtc_device *rtc = to_rtc_device(dev);
95 err = kstrtoul(buf, 0, &val);
99 if (val >= 4096 || val == 0)
102 rtc->max_user_freq = (int)val;
106 static DEVICE_ATTR_RW(max_user_freq);
109 * rtc_sysfs_show_hctosys - indicate if the given RTC set the system time
111 * Returns 1 if the system clock was set by this RTC at the last
112 * boot or resume event.
115 hctosys_show(struct device *dev, struct device_attribute *attr, char *buf)
117 #ifdef CONFIG_RTC_HCTOSYS_DEVICE
118 if (rtc_hctosys_ret == 0 &&
119 strcmp(dev_name(&to_rtc_device(dev)->dev),
120 CONFIG_RTC_HCTOSYS_DEVICE) == 0)
121 return sprintf(buf, "1\n");
124 return sprintf(buf, "0\n");
126 static DEVICE_ATTR_RO(hctosys);
129 wakealarm_show(struct device *dev, struct device_attribute *attr, char *buf)
133 struct rtc_wkalrm alm;
135 /* Don't show disabled alarms. For uniformity, RTC alarms are
136 * conceptually one-shot, even though some common RTCs (on PCs)
137 * don't actually work that way.
139 * NOTE: RTC implementations where the alarm doesn't match an
140 * exact YYYY-MM-DD HH:MM[:SS] date *must* disable their RTC
141 * alarms after they trigger, to ensure one-shot semantics.
143 retval = rtc_read_alarm(to_rtc_device(dev), &alm);
144 if (retval == 0 && alm.enabled) {
145 alarm = rtc_tm_to_time64(&alm.time);
146 retval = sprintf(buf, "%lld\n", alarm);
153 wakealarm_store(struct device *dev, struct device_attribute *attr,
154 const char *buf, size_t n)
159 struct rtc_wkalrm alm;
160 struct rtc_device *rtc = to_rtc_device(dev);
164 /* Only request alarms that trigger in the future. Disable them
165 * by writing another time, e.g. 0 meaning Jan 1 1970 UTC.
167 retval = rtc_read_time(rtc, &alm.time);
170 now = rtc_tm_to_time64(&alm.time);
173 if (*buf_ptr == '+') {
175 if (*buf_ptr == '=') {
181 retval = kstrtos64(buf_ptr, 0, &alarm);
187 if (alarm > now || push) {
188 /* Avoid accidentally clobbering active alarms; we can't
189 * entirely prevent that here, without even the minimal
190 * locking from the /dev/rtcN api.
192 retval = rtc_read_alarm(rtc, &alm);
197 push = rtc_tm_to_time64(&alm.time);
207 /* Provide a valid future alarm time. Linux isn't EFI,
208 * this time won't be ignored when disabling the alarm.
212 rtc_time64_to_tm(alarm, &alm.time);
214 retval = rtc_set_alarm(rtc, &alm);
215 return (retval < 0) ? retval : n;
217 static DEVICE_ATTR_RW(wakealarm);
220 offset_show(struct device *dev, struct device_attribute *attr, char *buf)
225 retval = rtc_read_offset(to_rtc_device(dev), &offset);
227 retval = sprintf(buf, "%ld\n", offset);
233 offset_store(struct device *dev, struct device_attribute *attr,
234 const char *buf, size_t n)
239 retval = kstrtol(buf, 10, &offset);
241 retval = rtc_set_offset(to_rtc_device(dev), offset);
243 return (retval < 0) ? retval : n;
245 static DEVICE_ATTR_RW(offset);
248 range_show(struct device *dev, struct device_attribute *attr, char *buf)
250 return sprintf(buf, "[%lld,%llu]\n", to_rtc_device(dev)->range_min,
251 to_rtc_device(dev)->range_max);
253 static DEVICE_ATTR_RO(range);
255 static struct attribute *rtc_attrs[] = {
259 &dev_attr_since_epoch.attr,
260 &dev_attr_max_user_freq.attr,
261 &dev_attr_hctosys.attr,
262 &dev_attr_wakealarm.attr,
263 &dev_attr_offset.attr,
264 &dev_attr_range.attr,
268 /* The reason to trigger an alarm with no process watching it (via sysfs)
269 * is its side effect: waking from a system state like suspend-to-RAM or
270 * suspend-to-disk. So: no attribute unless that side effect is possible.
271 * (Userspace may disable that mechanism later.)
273 static bool rtc_does_wakealarm(struct rtc_device *rtc)
275 if (!device_can_wakeup(rtc->dev.parent))
278 return rtc->ops->set_alarm != NULL;
281 static umode_t rtc_attr_is_visible(struct kobject *kobj,
282 struct attribute *attr, int n)
284 struct device *dev = container_of(kobj, struct device, kobj);
285 struct rtc_device *rtc = to_rtc_device(dev);
286 umode_t mode = attr->mode;
288 if (attr == &dev_attr_wakealarm.attr) {
289 if (!rtc_does_wakealarm(rtc))
291 } else if (attr == &dev_attr_offset.attr) {
292 if (!rtc->ops->set_offset)
294 } else if (attr == &dev_attr_range.attr) {
295 if (!(rtc->range_max - rtc->range_min))
302 static struct attribute_group rtc_attr_group = {
303 .is_visible = rtc_attr_is_visible,
307 static const struct attribute_group *rtc_attr_groups[] = {
312 const struct attribute_group **rtc_get_dev_attribute_groups(void)
314 return rtc_attr_groups;
317 int rtc_add_groups(struct rtc_device *rtc, const struct attribute_group **grps)
319 size_t old_cnt = 0, add_cnt = 0, new_cnt;
320 const struct attribute_group **groups, **old;
327 groups = rtc->dev.groups;
329 for (; *groups; groups++)
332 for (groups = grps; *groups; groups++)
335 new_cnt = old_cnt + add_cnt + 1;
336 groups = devm_kcalloc(&rtc->dev, new_cnt, sizeof(*groups), GFP_KERNEL);
339 memcpy(groups, rtc->dev.groups, old_cnt * sizeof(*groups));
340 memcpy(groups + old_cnt, grps, add_cnt * sizeof(*groups));
341 groups[old_cnt + add_cnt] = NULL;
343 old = rtc->dev.groups;
344 rtc->dev.groups = groups;
345 if (old && old != rtc_attr_groups)
346 devm_kfree(&rtc->dev, old);
350 EXPORT_SYMBOL(rtc_add_groups);
352 int rtc_add_group(struct rtc_device *rtc, const struct attribute_group *grp)
354 const struct attribute_group *groups[] = { grp, NULL };
356 return rtc_add_groups(rtc, groups);
358 EXPORT_SYMBOL(rtc_add_group);