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 
23 static ssize_t
name_show(struct device * dev,struct device_attribute * attr,char * buf)24 name_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 }
29 static DEVICE_ATTR_RO(name);
30 
31 static ssize_t
date_show(struct device * dev,struct device_attribute * attr,char * buf)32 date_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 }
43 static DEVICE_ATTR_RO(date);
44 
45 static ssize_t
time_show(struct device * dev,struct device_attribute * attr,char * buf)46 time_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 }
57 static DEVICE_ATTR_RO(time);
58 
59 static ssize_t
since_epoch_show(struct device * dev,struct device_attribute * attr,char * buf)60 since_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 }
75 static DEVICE_ATTR_RO(since_epoch);
76 
77 static ssize_t
max_user_freq_show(struct device * dev,struct device_attribute * attr,char * buf)78 max_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 
83 static ssize_t
max_user_freq_store(struct device * dev,struct device_attribute * attr,const char * buf,size_t n)84 max_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 }
102 static 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  */
113 static ssize_t
hctosys_show(struct device * dev,struct device_attribute * attr,char * buf)114 hctosys_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 }
124 static DEVICE_ATTR_RO(hctosys);
125 
126 static ssize_t
wakealarm_show(struct device * dev,struct device_attribute * attr,char * buf)127 wakealarm_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 
150 static ssize_t
wakealarm_store(struct device * dev,struct device_attribute * attr,const char * buf,size_t n)151 wakealarm_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 }
215 static DEVICE_ATTR_RW(wakealarm);
216 
217 static ssize_t
offset_show(struct device * dev,struct device_attribute * attr,char * buf)218 offset_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 
230 static ssize_t
offset_store(struct device * dev,struct device_attribute * attr,const char * buf,size_t n)231 offset_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 }
243 static DEVICE_ATTR_RW(offset);
244 
245 static ssize_t
range_show(struct device * dev,struct device_attribute * attr,char * buf)246 range_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 }
251 static DEVICE_ATTR_RO(range);
252 
253 static 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  */
rtc_does_wakealarm(struct rtc_device * rtc)271 static 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 
rtc_attr_is_visible(struct kobject * kobj,struct attribute * attr,int n)279 static 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 
300 static struct attribute_group rtc_attr_group = {
301 	.is_visible	= rtc_attr_is_visible,
302 	.attrs		= rtc_attrs,
303 };
304 
305 static const struct attribute_group *rtc_attr_groups[] = {
306 	&rtc_attr_group,
307 	NULL
308 };
309 
rtc_get_dev_attribute_groups(void)310 const struct attribute_group **rtc_get_dev_attribute_groups(void)
311 {
312 	return rtc_attr_groups;
313 }
314 
rtc_add_groups(struct rtc_device * rtc,const struct attribute_group ** grps)315 int 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 }
346 EXPORT_SYMBOL(rtc_add_groups);
347 
rtc_add_group(struct rtc_device * rtc,const struct attribute_group * grp)348 int 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 }
354 EXPORT_SYMBOL(rtc_add_group);
355