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/kstrtox.h>
 10#include <linux/module.h>
 11#include <linux/rtc.h>
 12
 13#include "rtc-core.h"
 14
 15/* device attributes */
 16
 17/*
 18 * NOTE:  RTC times displayed in sysfs use the RTC's timezone.  That's
 19 * ideally UTC.  However, PCs that also boot to MS-Windows normally use
 20 * the local time and change to match daylight savings time.  That affects
 21 * attributes including date, time, since_epoch, and wakealarm.
 22 */
 23
 24static ssize_t
 25name_show(struct device *dev, struct device_attribute *attr, char *buf)
 26{
 27	return sprintf(buf, "%s %s\n", dev_driver_string(dev->parent),
 28		       dev_name(dev->parent));
 29}
 30static DEVICE_ATTR_RO(name);
 31
 32static ssize_t
 33date_show(struct device *dev, struct device_attribute *attr, char *buf)
 34{
 35	ssize_t retval;
 36	struct rtc_time tm;
 37
 38	retval = rtc_read_time(to_rtc_device(dev), &tm);
 39	if (retval)
 40		return retval;
 41
 42	return sprintf(buf, "%ptRd\n", &tm);
 43}
 44static DEVICE_ATTR_RO(date);
 45
 46static ssize_t
 47time_show(struct device *dev, struct device_attribute *attr, char *buf)
 48{
 49	ssize_t retval;
 50	struct rtc_time tm;
 51
 52	retval = rtc_read_time(to_rtc_device(dev), &tm);
 53	if (retval)
 54		return retval;
 55
 56	return sprintf(buf, "%ptRt\n", &tm);
 57}
 58static DEVICE_ATTR_RO(time);
 59
 60static ssize_t
 61since_epoch_show(struct device *dev, struct device_attribute *attr, char *buf)
 62{
 63	ssize_t retval;
 64	struct rtc_time tm;
 65
 66	retval = rtc_read_time(to_rtc_device(dev), &tm);
 67	if (retval == 0) {
 68		time64_t time;
 69
 70		time = rtc_tm_to_time64(&tm);
 71		retval = sprintf(buf, "%lld\n", time);
 72	}
 73
 74	return retval;
 75}
 76static DEVICE_ATTR_RO(since_epoch);
 77
 78static ssize_t
 79max_user_freq_show(struct device *dev, struct device_attribute *attr, char *buf)
 80{
 81	return sprintf(buf, "%d\n", to_rtc_device(dev)->max_user_freq);
 82}
 83
 84static ssize_t
 85max_user_freq_store(struct device *dev, struct device_attribute *attr,
 86		    const char *buf, size_t n)
 87{
 88	struct rtc_device *rtc = to_rtc_device(dev);
 89	unsigned long val;
 90	int err;
 91
 92	err = kstrtoul(buf, 0, &val);
 93	if (err)
 94		return err;
 95
 96	if (val >= 4096 || val == 0)
 97		return -EINVAL;
 98
 99	rtc->max_user_freq = (int)val;
100
101	return n;
102}
103static DEVICE_ATTR_RW(max_user_freq);
104
105/**
106 * hctosys_show - indicate if the given RTC set the system time
107 * @dev: The device that the attribute belongs to.
108 * @attr: The attribute being read.
109 * @buf: The result buffer.
110 *
111 * buf is "1" if the system clock was set by this RTC at the last
112 * boot or resume event.
113 */
114static ssize_t
115hctosys_show(struct device *dev, struct device_attribute *attr, char *buf)
116{
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");
122#endif
123	return sprintf(buf, "0\n");
124}
125static DEVICE_ATTR_RO(hctosys);
126
127static ssize_t
128wakealarm_show(struct device *dev, struct device_attribute *attr, char *buf)
129{
130	ssize_t retval;
131	time64_t alarm;
132	struct rtc_wkalrm alm;
133
134	/* Don't show disabled alarms.  For uniformity, RTC alarms are
135	 * conceptually one-shot, even though some common RTCs (on PCs)
136	 * don't actually work that way.
137	 *
138	 * NOTE: RTC implementations where the alarm doesn't match an
139	 * exact YYYY-MM-DD HH:MM[:SS] date *must* disable their RTC
140	 * alarms after they trigger, to ensure one-shot semantics.
141	 */
142	retval = rtc_read_alarm(to_rtc_device(dev), &alm);
143	if (retval == 0 && alm.enabled) {
144		alarm = rtc_tm_to_time64(&alm.time);
145		retval = sprintf(buf, "%lld\n", alarm);
146	}
147
148	return retval;
149}
150
151static ssize_t
152wakealarm_store(struct device *dev, struct device_attribute *attr,
153		const char *buf, size_t n)
154{
155	ssize_t retval;
156	time64_t now, alarm;
157	time64_t push = 0;
158	struct rtc_wkalrm alm;
159	struct rtc_device *rtc = to_rtc_device(dev);
160	const char *buf_ptr;
161	int adjust = 0;
162
163	/* Only request alarms that trigger in the future.  Disable them
164	 * by writing another time, e.g. 0 meaning Jan 1 1970 UTC.
165	 */
166	retval = rtc_read_time(rtc, &alm.time);
167	if (retval < 0)
168		return retval;
169	now = rtc_tm_to_time64(&alm.time);
170
171	buf_ptr = buf;
172	if (*buf_ptr == '+') {
173		buf_ptr++;
174		if (*buf_ptr == '=') {
175			buf_ptr++;
176			push = 1;
177		} else {
178			adjust = 1;
179		}
180	}
181	retval = kstrtos64(buf_ptr, 0, &alarm);
182	if (retval)
183		return retval;
184	if (adjust)
185		alarm += now;
186	if (alarm > now || push) {
187		/* Avoid accidentally clobbering active alarms; we can't
188		 * entirely prevent that here, without even the minimal
189		 * locking from the /dev/rtcN api.
190		 */
191		retval = rtc_read_alarm(rtc, &alm);
192		if (retval < 0)
193			return retval;
194		if (alm.enabled) {
195			if (push) {
196				push = rtc_tm_to_time64(&alm.time);
197				alarm += push;
198			} else
199				return -EBUSY;
200		} else if (push)
201			return -EINVAL;
202		alm.enabled = 1;
203	} else {
204		alm.enabled = 0;
205
206		/* Provide a valid future alarm time.  Linux isn't EFI,
207		 * this time won't be ignored when disabling the alarm.
208		 */
209		alarm = now + 300;
210	}
211	rtc_time64_to_tm(alarm, &alm.time);
212
213	retval = rtc_set_alarm(rtc, &alm);
214	return (retval < 0) ? retval : n;
215}
216static DEVICE_ATTR_RW(wakealarm);
217
218static ssize_t
219offset_show(struct device *dev, struct device_attribute *attr, char *buf)
220{
221	ssize_t retval;
222	long offset;
223
224	retval = rtc_read_offset(to_rtc_device(dev), &offset);
225	if (retval == 0)
226		retval = sprintf(buf, "%ld\n", offset);
227
228	return retval;
229}
230
231static ssize_t
232offset_store(struct device *dev, struct device_attribute *attr,
233	     const char *buf, size_t n)
234{
235	ssize_t retval;
236	long offset;
237
238	retval = kstrtol(buf, 10, &offset);
239	if (retval == 0)
240		retval = rtc_set_offset(to_rtc_device(dev), offset);
241
242	return (retval < 0) ? retval : n;
243}
244static DEVICE_ATTR_RW(offset);
245
246static ssize_t
247range_show(struct device *dev, struct device_attribute *attr, char *buf)
248{
249	return sprintf(buf, "[%lld,%llu]\n", to_rtc_device(dev)->range_min,
250		       to_rtc_device(dev)->range_max);
251}
252static DEVICE_ATTR_RO(range);
253
254static struct attribute *rtc_attrs[] = {
255	&dev_attr_name.attr,
256	&dev_attr_date.attr,
257	&dev_attr_time.attr,
258	&dev_attr_since_epoch.attr,
259	&dev_attr_max_user_freq.attr,
260	&dev_attr_hctosys.attr,
261	&dev_attr_wakealarm.attr,
262	&dev_attr_offset.attr,
263	&dev_attr_range.attr,
264	NULL,
265};
266
267/* The reason to trigger an alarm with no process watching it (via sysfs)
268 * is its side effect:  waking from a system state like suspend-to-RAM or
269 * suspend-to-disk.  So: no attribute unless that side effect is possible.
270 * (Userspace may disable that mechanism later.)
271 */
272static bool rtc_does_wakealarm(struct rtc_device *rtc)
273{
274	if (!device_can_wakeup(rtc->dev.parent))
275		return false;
276
277	return !!test_bit(RTC_FEATURE_ALARM, rtc->features);
278}
279
280static umode_t rtc_attr_is_visible(struct kobject *kobj,
281				   struct attribute *attr, int n)
282{
283	struct device *dev = kobj_to_dev(kobj);
284	struct rtc_device *rtc = to_rtc_device(dev);
285	umode_t mode = attr->mode;
286
287	if (attr == &dev_attr_wakealarm.attr) {
288		if (!rtc_does_wakealarm(rtc))
289			mode = 0;
290	} else if (attr == &dev_attr_offset.attr) {
291		if (!rtc->ops->set_offset)
292			mode = 0;
293	} else if (attr == &dev_attr_range.attr) {
294		if (!(rtc->range_max - rtc->range_min))
295			mode = 0;
296	}
297
298	return mode;
299}
300
301static struct attribute_group rtc_attr_group = {
302	.is_visible	= rtc_attr_is_visible,
303	.attrs		= rtc_attrs,
304};
305
306static const struct attribute_group *rtc_attr_groups[] = {
307	&rtc_attr_group,
308	NULL
309};
310
311const struct attribute_group **rtc_get_dev_attribute_groups(void)
312{
313	return rtc_attr_groups;
314}
315
316int rtc_add_groups(struct rtc_device *rtc, const struct attribute_group **grps)
317{
318	size_t old_cnt = 0, add_cnt = 0, new_cnt;
319	const struct attribute_group **groups, **old;
320
321	if (!grps)
322		return -EINVAL;
323
324	groups = rtc->dev.groups;
325	if (groups)
326		for (; *groups; groups++)
327			old_cnt++;
328
329	for (groups = grps; *groups; groups++)
330		add_cnt++;
331
332	new_cnt = old_cnt + add_cnt + 1;
333	groups = devm_kcalloc(&rtc->dev, new_cnt, sizeof(*groups), GFP_KERNEL);
334	if (!groups)
335		return -ENOMEM;
336	memcpy(groups, rtc->dev.groups, old_cnt * sizeof(*groups));
337	memcpy(groups + old_cnt, grps, add_cnt * sizeof(*groups));
338	groups[old_cnt + add_cnt] = NULL;
339
340	old = rtc->dev.groups;
341	rtc->dev.groups = groups;
342	if (old && old != rtc_attr_groups)
343		devm_kfree(&rtc->dev, old);
344
345	return 0;
346}
347EXPORT_SYMBOL(rtc_add_groups);
348
349int rtc_add_group(struct rtc_device *rtc, const struct attribute_group *grp)
350{
351	const struct attribute_group *groups[] = { grp, NULL };
352
353	return rtc_add_groups(rtc, groups);
354}
355EXPORT_SYMBOL(rtc_add_group);