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