tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
1/*
2 * RTC subsystem, sysfs interface
3 *
4 * Copyright (C) 2005 Tower Technologies
5 * Author: Alessandro Zummo <a.zummo@towertech.it>
6 *
7 * This program is free software; you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License version 2 as
9 * published by the Free Software Foundation.
10*/
11
12#include <linux/module.h>
13#include <linux/rtc.h>
14
15#include "rtc-core.h"
16
17
18/* device attributes */
19
20/*
21 * NOTE: RTC times displayed in sysfs use the RTC's timezone. That's
22 * ideally UTC. However, PCs that also boot to MS-Windows normally use
23 * the local time and change to match daylight savings time. That affects
24 * attributes including date, time, since_epoch, and wakealarm.
25 */
26
27static ssize_t
28rtc_sysfs_show_name(struct device *dev, struct device_attribute *attr,
29 char *buf)
30{
31 return sprintf(buf, "%s\n", to_rtc_device(dev)->name);
32}
33
34static ssize_t
35rtc_sysfs_show_date(struct device *dev, struct device_attribute *attr,
36 char *buf)
37{
38 ssize_t retval;
39 struct rtc_time tm;
40
41 retval = rtc_read_time(to_rtc_device(dev), &tm);
42 if (retval == 0) {
43 retval = sprintf(buf, "%04d-%02d-%02d\n",
44 tm.tm_year + 1900, tm.tm_mon + 1, tm.tm_mday);
45 }
46
47 return retval;
48}
49
50static ssize_t
51rtc_sysfs_show_time(struct device *dev, struct device_attribute *attr,
52 char *buf)
53{
54 ssize_t retval;
55 struct rtc_time tm;
56
57 retval = rtc_read_time(to_rtc_device(dev), &tm);
58 if (retval == 0) {
59 retval = sprintf(buf, "%02d:%02d:%02d\n",
60 tm.tm_hour, tm.tm_min, tm.tm_sec);
61 }
62
63 return retval;
64}
65
66static ssize_t
67rtc_sysfs_show_since_epoch(struct device *dev, struct device_attribute *attr,
68 char *buf)
69{
70 ssize_t retval;
71 struct rtc_time tm;
72
73 retval = rtc_read_time(to_rtc_device(dev), &tm);
74 if (retval == 0) {
75 unsigned long time;
76 rtc_tm_to_time(&tm, &time);
77 retval = sprintf(buf, "%lu\n", time);
78 }
79
80 return retval;
81}
82
83static ssize_t
84rtc_sysfs_show_max_user_freq(struct device *dev, struct device_attribute *attr,
85 char *buf)
86{
87 return sprintf(buf, "%d\n", to_rtc_device(dev)->max_user_freq);
88}
89
90static ssize_t
91rtc_sysfs_set_max_user_freq(struct device *dev, struct device_attribute *attr,
92 const char *buf, size_t n)
93{
94 struct rtc_device *rtc = to_rtc_device(dev);
95 unsigned long val = simple_strtoul(buf, NULL, 0);
96
97 if (val >= 4096 || val == 0)
98 return -EINVAL;
99
100 rtc->max_user_freq = (int)val;
101
102 return n;
103}
104
105/**
106 * rtc_sysfs_show_hctosys - indicate if the given RTC set the system time
107 *
108 * Returns 1 if the system clock was set by this RTC at the last
109 * boot or resume event.
110 */
111static ssize_t
112rtc_sysfs_show_hctosys(struct device *dev, struct device_attribute *attr,
113 char *buf)
114{
115#ifdef CONFIG_RTC_HCTOSYS_DEVICE
116 if (rtc_hctosys_ret == 0 &&
117 strcmp(dev_name(&to_rtc_device(dev)->dev),
118 CONFIG_RTC_HCTOSYS_DEVICE) == 0)
119 return sprintf(buf, "1\n");
120 else
121#endif
122 return sprintf(buf, "0\n");
123}
124
125static struct device_attribute rtc_attrs[] = {
126 __ATTR(name, S_IRUGO, rtc_sysfs_show_name, NULL),
127 __ATTR(date, S_IRUGO, rtc_sysfs_show_date, NULL),
128 __ATTR(time, S_IRUGO, rtc_sysfs_show_time, NULL),
129 __ATTR(since_epoch, S_IRUGO, rtc_sysfs_show_since_epoch, NULL),
130 __ATTR(max_user_freq, S_IRUGO | S_IWUSR, rtc_sysfs_show_max_user_freq,
131 rtc_sysfs_set_max_user_freq),
132 __ATTR(hctosys, S_IRUGO, rtc_sysfs_show_hctosys, NULL),
133 { },
134};
135
136static ssize_t
137rtc_sysfs_show_wakealarm(struct device *dev, struct device_attribute *attr,
138 char *buf)
139{
140 ssize_t retval;
141 unsigned long alarm;
142 struct rtc_wkalrm alm;
143
144 /* Don't show disabled alarms. For uniformity, RTC alarms are
145 * conceptually one-shot, even though some common RTCs (on PCs)
146 * don't actually work that way.
147 *
148 * NOTE: RTC implementations where the alarm doesn't match an
149 * exact YYYY-MM-DD HH:MM[:SS] date *must* disable their RTC
150 * alarms after they trigger, to ensure one-shot semantics.
151 */
152 retval = rtc_read_alarm(to_rtc_device(dev), &alm);
153 if (retval == 0 && alm.enabled) {
154 rtc_tm_to_time(&alm.time, &alarm);
155 retval = sprintf(buf, "%lu\n", alarm);
156 }
157
158 return retval;
159}
160
161static ssize_t
162rtc_sysfs_set_wakealarm(struct device *dev, struct device_attribute *attr,
163 const char *buf, size_t n)
164{
165 ssize_t retval;
166 unsigned long now, alarm;
167 struct rtc_wkalrm alm;
168 struct rtc_device *rtc = to_rtc_device(dev);
169 char *buf_ptr;
170 int adjust = 0;
171
172 /* Only request alarms that trigger in the future. Disable them
173 * by writing another time, e.g. 0 meaning Jan 1 1970 UTC.
174 */
175 retval = rtc_read_time(rtc, &alm.time);
176 if (retval < 0)
177 return retval;
178 rtc_tm_to_time(&alm.time, &now);
179
180 buf_ptr = (char *)buf;
181 if (*buf_ptr == '+') {
182 buf_ptr++;
183 adjust = 1;
184 }
185 alarm = simple_strtoul(buf_ptr, NULL, 0);
186 if (adjust) {
187 alarm += now;
188 }
189 if (alarm > now) {
190 /* Avoid accidentally clobbering active alarms; we can't
191 * entirely prevent that here, without even the minimal
192 * locking from the /dev/rtcN api.
193 */
194 retval = rtc_read_alarm(rtc, &alm);
195 if (retval < 0)
196 return retval;
197 if (alm.enabled)
198 return -EBUSY;
199
200 alm.enabled = 1;
201 } else {
202 alm.enabled = 0;
203
204 /* Provide a valid future alarm time. Linux isn't EFI,
205 * this time won't be ignored when disabling the alarm.
206 */
207 alarm = now + 300;
208 }
209 rtc_time_to_tm(alarm, &alm.time);
210
211 retval = rtc_set_alarm(rtc, &alm);
212 return (retval < 0) ? retval : n;
213}
214static DEVICE_ATTR(wakealarm, S_IRUGO | S_IWUSR,
215 rtc_sysfs_show_wakealarm, rtc_sysfs_set_wakealarm);
216
217
218/* The reason to trigger an alarm with no process watching it (via sysfs)
219 * is its side effect: waking from a system state like suspend-to-RAM or
220 * suspend-to-disk. So: no attribute unless that side effect is possible.
221 * (Userspace may disable that mechanism later.)
222 */
223static inline int rtc_does_wakealarm(struct rtc_device *rtc)
224{
225 if (!device_can_wakeup(rtc->dev.parent))
226 return 0;
227 return rtc->ops->set_alarm != NULL;
228}
229
230
231void rtc_sysfs_add_device(struct rtc_device *rtc)
232{
233 int err;
234
235 /* not all RTCs support both alarms and wakeup */
236 if (!rtc_does_wakealarm(rtc))
237 return;
238
239 err = device_create_file(&rtc->dev, &dev_attr_wakealarm);
240 if (err)
241 dev_err(rtc->dev.parent,
242 "failed to create alarm attribute, %d\n", err);
243}
244
245void rtc_sysfs_del_device(struct rtc_device *rtc)
246{
247 /* REVISIT did we add it successfully? */
248 if (rtc_does_wakealarm(rtc))
249 device_remove_file(&rtc->dev, &dev_attr_wakealarm);
250}
251
252void __init rtc_sysfs_init(struct class *rtc_class)
253{
254 rtc_class->dev_attrs = rtc_attrs;
255}