drivers/rtc/rtc-sysfs.c

   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
  27 static ssize_t
  28 name_show(struct device *dev, struct device_attribute *attr, char *buf)
  29 {
  30         return sprintf(buf, "%s\n", to_rtc_device(dev)->name);
  31 }
  32 static DEVICE_ATTR_RO(name);
  33
  34 static ssize_t
  35 date_show(struct device *dev, struct device_attribute *attr, char *buf)
  36 {
  37         ssize_t retval;
  38         struct rtc_time tm;
  39
  40         retval = rtc_read_time(to_rtc_device(dev), &tm);
  41         if (retval == 0) {
  42                 retval = sprintf(buf, "%04d-%02d-%02d\n",
  43                         tm.tm_year + 1900, tm.tm_mon + 1, tm.tm_mday);
  44         }
  45
  46         return retval;
  47 }
  48 static DEVICE_ATTR_RO(date);
  49
  50 static ssize_t
  51 time_show(struct device *dev, struct device_attribute *attr, char *buf)
  52 {
  53         ssize_t retval;
  54         struct rtc_time tm;
  55
  56         retval = rtc_read_time(to_rtc_device(dev), &tm);
  57         if (retval == 0) {
  58                 retval = sprintf(buf, "%02d:%02d:%02d\n",
  59                         tm.tm_hour, tm.tm_min, tm.tm_sec);
  60         }
  61
  62         return retval;
  63 }
  64 static DEVICE_ATTR_RO(time);
  65
  66 static ssize_t
  67 since_epoch_show(struct device *dev, struct device_attribute *attr, char *buf)
  68 {
  69         ssize_t retval;
  70         struct rtc_time tm;
  71
  72         retval = rtc_read_time(to_rtc_device(dev), &tm);
  73         if (retval == 0) {
  74                 unsigned long time;
  75                 rtc_tm_to_time(&tm, &time);
  76                 retval = sprintf(buf, "%lu\n", time);
  77         }
  78
  79         return retval;
  80 }
  81 static DEVICE_ATTR_RO(since_epoch);
  82
  83 static ssize_t
  84 max_user_freq_show(struct device *dev, struct device_attribute *attr, char *buf)
  85 {
  86         return sprintf(buf, "%d\n", to_rtc_device(dev)->max_user_freq);
  87 }
  88
  89 static ssize_t
  90 max_user_freq_store(struct device *dev, struct device_attribute *attr,
  91                 const char *buf, size_t n)
  92 {
  93         struct rtc_device *rtc = to_rtc_device(dev);
  94         unsigned long val = simple_strtoul(buf, NULL, 0);
  95
  96         if (val >= 4096 || val == 0)
  97                 return -EINVAL;
  98
  99         rtc->max_user_freq = (int)val;
 100
 101         return n;
 102 }
 103 static DEVICE_ATTR_RW(max_user_freq);
 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  */
 111 static ssize_t
 112 hctosys_show(struct device *dev, struct device_attribute *attr, char *buf)
 113 {
 114 #ifdef CONFIG_RTC_HCTOSYS_DEVICE
 115         if (rtc_hctosys_ret == 0 &&
 116                         strcmp(dev_name(&to_rtc_device(dev)->dev),
 117                                 CONFIG_RTC_HCTOSYS_DEVICE) == 0)
 118                 return sprintf(buf, "1\n");
 119         else
 120 #endif
 121                 return sprintf(buf, "0\n");
 122 }
 123 static DEVICE_ATTR_RO(hctosys);
 124
 125 static ssize_t
 126 wakealarm_show(struct device *dev, struct device_attribute *attr, char *buf)
 127 {
 128         ssize_t retval;
 129         unsigned long alarm;
 130         struct rtc_wkalrm alm;
 131
 132         /* Don't show disabled alarms.  For uniformity, RTC alarms are
 133          * conceptually one-shot, even though some common RTCs (on PCs)
 134          * don't actually work that way.
 135          *
 136          * NOTE: RTC implementations where the alarm doesn't match an
 137          * exact YYYY-MM-DD HH:MM[:SS] date *must* disable their RTC
 138          * alarms after they trigger, to ensure one-shot semantics.
 139          */
 140         retval = rtc_read_alarm(to_rtc_device(dev), &alm);
 141         if (retval == 0 && alm.enabled) {
 142                 rtc_tm_to_time(&alm.time, &alarm);
 143                 retval = sprintf(buf, "%lu\n", alarm);
 144         }
 145
 146         return retval;
 147 }
 148
 149 static ssize_t
 150 wakealarm_store(struct device *dev, struct device_attribute *attr,
 151                 const char *buf, size_t n)
 152 {
 153         ssize_t retval;
 154         unsigned long now, alarm;
 155         unsigned long push = 0;
 156         struct rtc_wkalrm alm;
 157         struct rtc_device *rtc = to_rtc_device(dev);
 158         char *buf_ptr;
 159         int adjust = 0;
 160
 161         /* Only request alarms that trigger in the future.  Disable them
 162          * by writing another time, e.g. 0 meaning Jan 1 1970 UTC.
 163          */
 164         retval = rtc_read_time(rtc, &alm.time);
 165         if (retval < 0)
 166                 return retval;
 167         rtc_tm_to_time(&alm.time, &now);
 168
 169         buf_ptr = (char *)buf;
 170         if (*buf_ptr == '+') {
 171                 buf_ptr++;
 172                 if (*buf_ptr == '=') {
 173                         buf_ptr++;
 174                         push = 1;
 175                 } else
 176                         adjust = 1;
 177         }
 178         alarm = simple_strtoul(buf_ptr, NULL, 0);
 179         if (adjust) {
 180                 alarm += now;
 181         }
 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                                 rtc_tm_to_time(&alm.time, &push);
 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_time_to_tm(alarm, &alm.time);
 208
 209         retval = rtc_set_alarm(rtc, &alm);
 210         return (retval < 0) ? retval : n;
 211 }
 212 static DEVICE_ATTR_RW(wakealarm);
 213
 214 static struct attribute *rtc_attrs[] = {
 215         &dev_attr_name.attr,
 216         &dev_attr_date.attr,
 217         &dev_attr_time.attr,
 218         &dev_attr_since_epoch.attr,
 219         &dev_attr_max_user_freq.attr,
 220         &dev_attr_hctosys.attr,
 221         &dev_attr_wakealarm.attr,
 222         NULL,
 223 };
 224
 225 /* The reason to trigger an alarm with no process watching it (via sysfs)
 226  * is its side effect:  waking from a system state like suspend-to-RAM or
 227  * suspend-to-disk.  So: no attribute unless that side effect is possible.
 228  * (Userspace may disable that mechanism later.)
 229  */
 230 static bool rtc_does_wakealarm(struct rtc_device *rtc)
 231 {
 232         if (!device_can_wakeup(rtc->dev.parent))
 233                 return false;
 234
 235         return rtc->ops->set_alarm != NULL;
 236 }
 237
 238 static umode_t rtc_attr_is_visible(struct kobject *kobj,
 239                                    struct attribute *attr, int n)
 240 {
 241         struct device *dev = container_of(kobj, struct device, kobj);
 242         struct rtc_device *rtc = to_rtc_device(dev);
 243         umode_t mode = attr->mode;
 244
 245         if (attr == &dev_attr_wakealarm.attr)
 246                 if (!rtc_does_wakealarm(rtc))
 247                         mode = 0;
 248
 249         return mode;
 250 }
 251
 252 static struct attribute_group rtc_attr_group = {
 253         .is_visible     = rtc_attr_is_visible,
 254         .attrs          = rtc_attrs,
 255 };
 256
 257 static const struct attribute_group *rtc_attr_groups[] = {
 258         &rtc_attr_group,
 259         NULL
 260 };
 261
 262 const struct attribute_group **rtc_get_dev_attribute_groups(void)
 263 {
 264         return rtc_attr_groups;
 265 }