1// SPDX-License-Identifier: GPL-2.0
  2/*
  3 * RTC subsystem, sysfs interface
  4 *
  5 * Copyright (C) 2005 Tower Technologies
  6 * Author: Alessandro Zummo <a.zummo@towertech.it>
  7 */
  8
  9#include <linux/module.h>
 10#include <linux/rtc.h>
 11
 12#include "rtc-core.h"
 13
 14/* device attributes */
 15
 16/*
 17 * NOTE:  RTC times displayed in sysfs use the RTC's timezone.  That's
 18 * ideally UTC.  However, PCs that also boot to MS-Windows normally use
 19 * the local time and change to match daylight savings time.  That affects
 20 * attributes including date, time, since_epoch, and wakealarm.
 21 */
 22
 23static ssize_t
 24name_show(struct device *dev, struct device_attribute *attr, char *buf)
 25{
 26	return sprintf(buf, "%s %s\n", dev_driver_string(dev->parent),
 27		       dev_name(dev->parent));
 28}
 29static DEVICE_ATTR_RO(name);
 30
 31static ssize_t
 32date_show(struct device *dev, struct device_attribute *attr, char *buf)
 33{
 34	ssize_t retval;
 35	struct rtc_time tm;
 36
 37	retval = rtc_read_time(to_rtc_device(dev), &tm);
 38	if (retval)
 39		return retval;
 40
 41	return sprintf(buf, "%ptRd\n", &tm);
 42}
 43static DEVICE_ATTR_RO(date);
 44
 45static ssize_t
 46time_show(struct device *dev, struct device_attribute *attr, char *buf)
 47{
 48	ssize_t retval;
 49	struct rtc_time tm;
 50
 51	retval = rtc_read_time(to_rtc_device(dev), &tm);
 52	if (retval)
 53		return retval;
 54
 55	return sprintf(buf, "%ptRt\n", &tm);
 56}
 57static DEVICE_ATTR_RO(time);
 58
 59static ssize_t
 60since_epoch_show(struct device *dev, struct device_attribute *attr, char *buf)
 61{
 62	ssize_t retval;
 63	struct rtc_time tm;
 64
 65	retval = rtc_read_time(to_rtc_device(dev), &tm);
 66	if (retval == 0) {
 67		time64_t time;
 68
 69		time = rtc_tm_to_time64(&tm);
 70		retval = sprintf(buf, "%lld\n", time);
 71	}
 72
 73	return retval;
 74}
 75static DEVICE_ATTR_RO(since_epoch);
 76
 77static ssize_t
 78max_user_freq_show(struct device *dev, struct device_attribute *attr, char *buf)
 79{
 80	return sprintf(buf, "%d\n", to_rtc_device(dev)->max_user_freq);
 81}
 82
 83static ssize_t
 84max_user_freq_store(struct device *dev, struct device_attribute *attr,
 85		    const char *buf, size_t n)
 86{
 87	struct rtc_device *rtc = to_rtc_device(dev);
 88	unsigned long val;
 89	int err;
 90
 91	err = kstrtoul(buf, 0, &val);
 92	if (err)
 93		return err;
 94
 95	if (val >= 4096 || val == 0)
 96		return -EINVAL;
 97
 98	rtc->max_user_freq = (int)val;
 99
100	return n;
101}
102static DEVICE_ATTR_RW(max_user_freq);
103
104/**
105 * hctosys_show - indicate if the given RTC set the system time
106 * @dev: The device that the attribute belongs to.
107 * @attr: The attribute being read.
108 * @buf: The result buffer.
109 *
110 * buf is "1" if the system clock was set by this RTC at the last
111 * boot or resume event.
112 */
113static ssize_t
114hctosys_show(struct device *dev, struct device_attribute *attr, char *buf)
115{
116#ifdef CONFIG_RTC_HCTOSYS_DEVICE
117	if (rtc_hctosys_ret == 0 &&
118	    strcmp(dev_name(&to_rtc_device(dev)->dev),
119		   CONFIG_RTC_HCTOSYS_DEVICE) == 0)
120		return sprintf(buf, "1\n");
121#endif
122	return sprintf(buf, "0\n");
123}
124static DEVICE_ATTR_RO(hctosys);
125
126static ssize_t
127wakealarm_show(struct device *dev, struct device_attribute *attr, char *buf)
128{
129	ssize_t retval;
130	time64_t alarm;
131	struct rtc_wkalrm alm;
132
133	/* Don't show disabled alarms.  For uniformity, RTC alarms are
134	 * conceptually one-shot, even though some common RTCs (on PCs)
135	 * don't actually work that way.
136	 *
137	 * NOTE: RTC implementations where the alarm doesn't match an
138	 * exact YYYY-MM-DD HH:MM[:SS] date *must* disable their RTC
139	 * alarms after they trigger, to ensure one-shot semantics.
140	 */
141	retval = rtc_read_alarm(to_rtc_device(dev), &alm);
142	if (retval == 0 && alm.enabled) {
143		alarm = rtc_tm_to_time64(&alm.time);
144		retval = sprintf(buf, "%lld\n", alarm);
145	}
146
147	return retval;
148}
149
150static ssize_t
151wakealarm_store(struct device *dev, struct device_attribute *attr,
152		const char *buf, size_t n)
153{
154	ssize_t retval;
155	time64_t now, alarm;
156	time64_t push = 0;
157	struct rtc_wkalrm alm;
158	struct rtc_device *rtc = to_rtc_device(dev);
159	const char *buf_ptr;
160	int adjust = 0;
161
162	/* Only request alarms that trigger in the future.  Disable them
163	 * by writing another time, e.g. 0 meaning Jan 1 1970 UTC.
164	 */
165	retval = rtc_read_time(rtc, &alm.time);
166	if (retval < 0)
167		return retval;
168	now = rtc_tm_to_time64(&alm.time);
169
170	buf_ptr = buf;
171	if (*buf_ptr == '+') {
172		buf_ptr++;
173		if (*buf_ptr == '=') {
174			buf_ptr++;
175			push = 1;
176		} else {
177			adjust = 1;
178		}
179	}
180	retval = kstrtos64(buf_ptr, 0, &alarm);
181	if (retval)
182		return retval;
183	if (adjust)
184		alarm += now;
185	if (alarm > now || push) {
186		/* Avoid accidentally clobbering active alarms; we can't
187		 * entirely prevent that here, without even the minimal
188		 * locking from the /dev/rtcN api.
189		 */
190		retval = rtc_read_alarm(rtc, &alm);
191		if (retval < 0)
192			return retval;
193		if (alm.enabled) {
194			if (push) {
195				push = rtc_tm_to_time64(&alm.time);
196				alarm += push;
197			} else
198				return -EBUSY;
199		} else if (push)
200			return -EINVAL;
201		alm.enabled = 1;
202	} else {
203		alm.enabled = 0;
204
205		/* Provide a valid future alarm time.  Linux isn't EFI,
206		 * this time won't be ignored when disabling the alarm.
207		 */
208		alarm = now + 300;
209	}
210	rtc_time64_to_tm(alarm, &alm.time);
211
212	retval = rtc_set_alarm(rtc, &alm);
213	return (retval < 0) ? retval : n;
214}
215static DEVICE_ATTR_RW(wakealarm);
216
217static ssize_t
218offset_show(struct device *dev, struct device_attribute *attr, char *buf)
219{
220	ssize_t retval;
221	long offset;
222
223	retval = rtc_read_offset(to_rtc_device(dev), &offset);
224	if (retval == 0)
225		retval = sprintf(buf, "%ld\n", offset);
226
227	return retval;
228}
229
230static ssize_t
231offset_store(struct device *dev, struct device_attribute *attr,
232	     const char *buf, size_t n)
233{
234	ssize_t retval;
235	long offset;
236
237	retval = kstrtol(buf, 10, &offset);
238	if (retval == 0)
239		retval = rtc_set_offset(to_rtc_device(dev), offset);
240
241	return (retval < 0) ? retval : n;
242}
243static DEVICE_ATTR_RW(offset);
244
245static ssize_t
246range_show(struct device *dev, struct device_attribute *attr, char *buf)
247{
248	return sprintf(buf, "[%lld,%llu]\n", to_rtc_device(dev)->range_min,
249		       to_rtc_device(dev)->range_max);
250}
251static DEVICE_ATTR_RO(range);
252
253static struct attribute *rtc_attrs[] = {
254	&dev_attr_name.attr,
255	&dev_attr_date.attr,
256	&dev_attr_time.attr,
257	&dev_attr_since_epoch.attr,
258	&dev_attr_max_user_freq.attr,
259	&dev_attr_hctosys.attr,
260	&dev_attr_wakealarm.attr,
261	&dev_attr_offset.attr,
262	&dev_attr_range.attr,
263	NULL,
264};
265
266/* The reason to trigger an alarm with no process watching it (via sysfs)
267 * is its side effect:  waking from a system state like suspend-to-RAM or
268 * suspend-to-disk.  So: no attribute unless that side effect is possible.
269 * (Userspace may disable that mechanism later.)
270 */
271static bool rtc_does_wakealarm(struct rtc_device *rtc)
272{
273	if (!device_can_wakeup(rtc->dev.parent))
274		return false;
275
276	return !!test_bit(RTC_FEATURE_ALARM, rtc->features);
277}
278
279static umode_t rtc_attr_is_visible(struct kobject *kobj,
280				   struct attribute *attr, int n)
281{
282	struct device *dev = kobj_to_dev(kobj);
283	struct rtc_device *rtc = to_rtc_device(dev);
284	umode_t mode = attr->mode;
285
286	if (attr == &dev_attr_wakealarm.attr) {
287		if (!rtc_does_wakealarm(rtc))
288			mode = 0;
289	} else if (attr == &dev_attr_offset.attr) {
290		if (!rtc->ops->set_offset)
291			mode = 0;
292	} else if (attr == &dev_attr_range.attr) {
293		if (!(rtc->range_max - rtc->range_min))
294			mode = 0;
295	}
296
297	return mode;
298}
299
300static struct attribute_group rtc_attr_group = {
301	.is_visible	= rtc_attr_is_visible,
302	.attrs		= rtc_attrs,
303};
304
305static const struct attribute_group *rtc_attr_groups[] = {
306	&rtc_attr_group,
307	NULL
308};
309
310const struct attribute_group **rtc_get_dev_attribute_groups(void)
311{
312	return rtc_attr_groups;
313}
314
315int rtc_add_groups(struct rtc_device *rtc, const struct attribute_group **grps)
316{
317	size_t old_cnt = 0, add_cnt = 0, new_cnt;
318	const struct attribute_group **groups, **old;
319
320	if (!grps)
321		return -EINVAL;
322
323	groups = rtc->dev.groups;
324	if (groups)
325		for (; *groups; groups++)
326			old_cnt++;
327
328	for (groups = grps; *groups; groups++)
329		add_cnt++;
330
331	new_cnt = old_cnt + add_cnt + 1;
332	groups = devm_kcalloc(&rtc->dev, new_cnt, sizeof(*groups), GFP_KERNEL);
333	if (!groups)
334		return -ENOMEM;
335	memcpy(groups, rtc->dev.groups, old_cnt * sizeof(*groups));
336	memcpy(groups + old_cnt, grps, add_cnt * sizeof(*groups));
337	groups[old_cnt + add_cnt] = NULL;
338
339	old = rtc->dev.groups;
340	rtc->dev.groups = groups;
341	if (old && old != rtc_attr_groups)
342		devm_kfree(&rtc->dev, old);
343
344	return 0;
345}
346EXPORT_SYMBOL(rtc_add_groups);
347
348int rtc_add_group(struct rtc_device *rtc, const struct attribute_group *grp)
349{
350	const struct attribute_group *groups[] = { grp, NULL };
351
352	return rtc_add_groups(rtc, groups);
353}
354EXPORT_SYMBOL(rtc_add_group);