sysfs.c

  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 sysfs_emit(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 sysfs_emit(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 sysfs_emit(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)
 68		return retval;
 69
 70	return sysfs_emit(buf, "%lld\n", rtc_tm_to_time64(&tm));
 71}
 72static DEVICE_ATTR_RO(since_epoch);
 73
 74static ssize_t
 75max_user_freq_show(struct device *dev, struct device_attribute *attr, char *buf)
 76{
 77	return sysfs_emit(buf, "%d\n", to_rtc_device(dev)->max_user_freq);
 78}
 79
 80static ssize_t
 81max_user_freq_store(struct device *dev, struct device_attribute *attr,
 82		    const char *buf, size_t n)
 83{
 84	struct rtc_device *rtc = to_rtc_device(dev);
 85	unsigned long val;
 86	int err;
 87
 88	err = kstrtoul(buf, 0, &val);
 89	if (err)
 90		return err;
 91
 92	if (val >= 4096 || val == 0)
 93		return -EINVAL;
 94
 95	rtc->max_user_freq = (int)val;
 96
 97	return n;
 98}
 99static DEVICE_ATTR_RW(max_user_freq);
100
101/**
102 * hctosys_show - indicate if the given RTC set the system time
103 * @dev: The device that the attribute belongs to.
104 * @attr: The attribute being read.
105 * @buf: The result buffer.
106 *
107 * buf is "1" if the system clock was set by this RTC at the last
108 * boot or resume event.
109 */
110static ssize_t
111hctosys_show(struct device *dev, struct device_attribute *attr, char *buf)
112{
113#ifdef CONFIG_RTC_HCTOSYS_DEVICE
114	if (rtc_hctosys_ret == 0 &&
115	    strcmp(dev_name(&to_rtc_device(dev)->dev),
116		   CONFIG_RTC_HCTOSYS_DEVICE) == 0)
117		return sysfs_emit(buf, "1\n");
118#endif
119	return sysfs_emit(buf, "0\n");
120}
121static DEVICE_ATTR_RO(hctosys);
122
123static ssize_t
124wakealarm_show(struct device *dev, struct device_attribute *attr, char *buf)
125{
126	ssize_t retval;
127	struct rtc_wkalrm alm;
128
129	/* Don't show disabled alarms.  For uniformity, RTC alarms are
130	 * conceptually one-shot, even though some common RTCs (on PCs)
131	 * don't actually work that way.
132	 *
133	 * NOTE: RTC implementations where the alarm doesn't match an
134	 * exact YYYY-MM-DD HH:MM[:SS] date *must* disable their RTC
135	 * alarms after they trigger, to ensure one-shot semantics.
136	 */
137	retval = rtc_read_alarm(to_rtc_device(dev), &alm);
138	if (retval)
139		return retval;
140
141	if (alm.enabled)
142		return sysfs_emit(buf, "%lld\n", rtc_tm_to_time64(&alm.time));
143
144	return 0;
145}
146
147static ssize_t
148wakealarm_store(struct device *dev, struct device_attribute *attr,
149		const char *buf, size_t n)
150{
151	ssize_t retval;
152	time64_t now, alarm;
153	time64_t push = 0;
154	struct rtc_wkalrm alm;
155	struct rtc_device *rtc = to_rtc_device(dev);
156	const char *buf_ptr;
157	int adjust = 0;
158
159	/* Only request alarms that trigger in the future.  Disable them
160	 * by writing another time, e.g. 0 meaning Jan 1 1970 UTC.
161	 */
162	retval = rtc_read_time(rtc, &alm.time);
163	if (retval < 0)
164		return retval;
165	now = rtc_tm_to_time64(&alm.time);
166
167	buf_ptr = buf;
168	if (*buf_ptr == '+') {
169		buf_ptr++;
170		if (*buf_ptr == '=') {
171			buf_ptr++;
172			push = 1;
173		} else {
174			adjust = 1;
175		}
176	}
177	retval = kstrtos64(buf_ptr, 0, &alarm);
178	if (retval)
179		return retval;
180	if (adjust)
181		alarm += now;
182	if (alarm > now || push) {
183		/* Avoid accidentally clobbering active alarms; we can't
184		 * entirely prevent that here, without even the minimal
185		 * locking from the /dev/rtcN api.
186		 */
187		retval = rtc_read_alarm(rtc, &alm);
188		if (retval < 0)
189			return retval;
190		if (alm.enabled) {
191			if (push) {
192				push = rtc_tm_to_time64(&alm.time);
193				alarm += push;
194			} else
195				return -EBUSY;
196		} else if (push)
197			return -EINVAL;
198		alm.enabled = 1;
199	} else {
200		alm.enabled = 0;
201
202		/* Provide a valid future alarm time.  Linux isn't EFI,
203		 * this time won't be ignored when disabling the alarm.
204		 */
205		alarm = now + 300;
206	}
207	rtc_time64_to_tm(alarm, &alm.time);
208
209	retval = rtc_set_alarm(rtc, &alm);
210	return (retval < 0) ? retval : n;
211}
212static DEVICE_ATTR_RW(wakealarm);
213
214static ssize_t
215offset_show(struct device *dev, struct device_attribute *attr, char *buf)
216{
217	ssize_t retval;
218	long offset;
219
220	retval = rtc_read_offset(to_rtc_device(dev), &offset);
221	if (retval)
222		return retval;
223
224	return sysfs_emit(buf, "%ld\n", offset);
225}
226
227static ssize_t
228offset_store(struct device *dev, struct device_attribute *attr,
229	     const char *buf, size_t n)
230{
231	ssize_t retval;
232	long offset;
233
234	retval = kstrtol(buf, 10, &offset);
235	if (retval == 0)
236		retval = rtc_set_offset(to_rtc_device(dev), offset);
237
238	return (retval < 0) ? retval : n;
239}
240static DEVICE_ATTR_RW(offset);
241
242static ssize_t
243range_show(struct device *dev, struct device_attribute *attr, char *buf)
244{
245	return sysfs_emit(buf, "[%lld,%llu]\n", to_rtc_device(dev)->range_min,
246			  to_rtc_device(dev)->range_max);
247}
248static DEVICE_ATTR_RO(range);
249
250static struct attribute *rtc_attrs[] = {
251	&dev_attr_name.attr,
252	&dev_attr_date.attr,
253	&dev_attr_time.attr,
254	&dev_attr_since_epoch.attr,
255	&dev_attr_max_user_freq.attr,
256	&dev_attr_hctosys.attr,
257	&dev_attr_wakealarm.attr,
258	&dev_attr_offset.attr,
259	&dev_attr_range.attr,
260	NULL,
261};
262
263/* The reason to trigger an alarm with no process watching it (via sysfs)
264 * is its side effect:  waking from a system state like suspend-to-RAM or
265 * suspend-to-disk.  So: no attribute unless that side effect is possible.
266 * (Userspace may disable that mechanism later.)
267 */
268static bool rtc_does_wakealarm(struct rtc_device *rtc)
269{
270	if (!device_can_wakeup(rtc->dev.parent))
271		return false;
272
273	return !!test_bit(RTC_FEATURE_ALARM, rtc->features);
274}
275
276static umode_t rtc_attr_is_visible(struct kobject *kobj,
277				   struct attribute *attr, int n)
278{
279	struct device *dev = kobj_to_dev(kobj);
280	struct rtc_device *rtc = to_rtc_device(dev);
281	umode_t mode = attr->mode;
282
283	if (attr == &dev_attr_wakealarm.attr) {
284		if (!rtc_does_wakealarm(rtc))
285			mode = 0;
286	} else if (attr == &dev_attr_offset.attr) {
287		if (!rtc->ops->set_offset)
288			mode = 0;
289	} else if (attr == &dev_attr_range.attr) {
290		if (!(rtc->range_max - rtc->range_min))
291			mode = 0;
292	}
293
294	return mode;
295}
296
297static struct attribute_group rtc_attr_group = {
298	.is_visible	= rtc_attr_is_visible,
299	.attrs		= rtc_attrs,
300};
301__ATTRIBUTE_GROUPS(rtc_attr);
302
303const struct attribute_group **rtc_get_dev_attribute_groups(void)
304{
305	return rtc_attr_groups;
306}
307
308int rtc_add_groups(struct rtc_device *rtc, const struct attribute_group **grps)
309{
310	size_t old_cnt = 0, add_cnt = 0, new_cnt;
311	const struct attribute_group **groups, **old;
312
313	if (grps) {
314		for (groups = grps; *groups; groups++)
315			add_cnt++;
316		/* No need to modify current groups if nothing new is provided */
317		if (add_cnt == 0)
318			return 0;
319	} else {
320		return -EINVAL;
321	}
322
323	groups = rtc->dev.groups;
324	if (groups)
325		for (; *groups; groups++)
326			old_cnt++;
327
328	new_cnt = old_cnt + add_cnt + 1;
329	groups = devm_kcalloc(&rtc->dev, new_cnt, sizeof(*groups), GFP_KERNEL);
330	if (!groups)
331		return -ENOMEM;
332	memcpy(groups, rtc->dev.groups, old_cnt * sizeof(*groups));
333	memcpy(groups + old_cnt, grps, add_cnt * sizeof(*groups));
334	groups[old_cnt + add_cnt] = NULL;
335
336	old = rtc->dev.groups;
337	rtc->dev.groups = groups;
338	if (old && old != rtc_attr_groups)
339		devm_kfree(&rtc->dev, old);
340
341	return 0;
342}
343EXPORT_SYMBOL(rtc_add_groups);
344
345int rtc_add_group(struct rtc_device *rtc, const struct attribute_group *grp)
346{
347	const struct attribute_group *groups[] = { grp, NULL };
348
349	return rtc_add_groups(rtc, groups);
350}
351EXPORT_SYMBOL(rtc_add_group);