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 rtc_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
  34 static ssize_t
  35 rtc_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
  50 static ssize_t
  51 rtc_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
  66 static ssize_t
  67 rtc_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
  83 static ssize_t
  84 rtc_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
  90 static ssize_t
  91 rtc_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 static struct device_attribute rtc_attrs[] = {
 106         __ATTR(name, S_IRUGO, rtc_sysfs_show_name, NULL),
 107         __ATTR(date, S_IRUGO, rtc_sysfs_show_date, NULL),
 108         __ATTR(time, S_IRUGO, rtc_sysfs_show_time, NULL),
 109         __ATTR(since_epoch, S_IRUGO, rtc_sysfs_show_since_epoch, NULL),
 110         __ATTR(max_user_freq, S_IRUGO | S_IWUSR, rtc_sysfs_show_max_user_freq,
 111                         rtc_sysfs_set_max_user_freq),
 112         { },
 113 };
 114
 115 static ssize_t
 116 rtc_sysfs_show_wakealarm(struct device *dev, struct device_attribute *attr,
 117                 char *buf)
 118 {
 119         ssize_t retval;
 120         unsigned long alarm;
 121         struct rtc_wkalrm alm;
 122
 123         /* Don't show disabled alarms.  For uniformity, RTC alarms are
 124          * conceptually one-shot, even though some common RTCs (on PCs)
 125          * don't actually work that way.
 126          *
 127          * NOTE: RTC implementations where the alarm doesn't match an
 128          * exact YYYY-MM-DD HH:MM[:SS] date *must* disable their RTC
 129          * alarms after they trigger, to ensure one-shot semantics.
 130          */
 131         retval = rtc_read_alarm(to_rtc_device(dev), &alm);
 132         if (retval == 0 && alm.enabled) {
 133                 rtc_tm_to_time(&alm.time, &alarm);
 134                 retval = sprintf(buf, "%lu\n", alarm);
 135         }
 136
 137         return retval;
 138 }
 139
 140 static ssize_t
 141 rtc_sysfs_set_wakealarm(struct device *dev, struct device_attribute *attr,
 142                 const char *buf, size_t n)
 143 {
 144         ssize_t retval;
 145         unsigned long now, alarm;
 146         struct rtc_wkalrm alm;
 147         struct rtc_device *rtc = to_rtc_device(dev);
 148
 149         /* Only request alarms that trigger in the future.  Disable them
 150          * by writing another time, e.g. 0 meaning Jan 1 1970 UTC.
 151          */
 152         retval = rtc_read_time(rtc, &alm.time);
 153         if (retval < 0)
 154                 return retval;
 155         rtc_tm_to_time(&alm.time, &now);
 156
 157         alarm = simple_strtoul(buf, NULL, 0);
 158         if (alarm > now) {
 159                 /* Avoid accidentally clobbering active alarms; we can't
 160                  * entirely prevent that here, without even the minimal
 161                  * locking from the /dev/rtcN api.
 162                  */
 163                 retval = rtc_read_alarm(rtc, &alm);
 164                 if (retval < 0)
 165                         return retval;
 166                 if (alm.enabled)
 167                         return -EBUSY;
 168
 169                 alm.enabled = 1;
 170         } else {
 171                 alm.enabled = 0;
 172
 173                 /* Provide a valid future alarm time.  Linux isn't EFI,
 174                  * this time won't be ignored when disabling the alarm.
 175                  */
 176                 alarm = now + 300;
 177         }
 178         rtc_time_to_tm(alarm, &alm.time);
 179
 180         retval = rtc_set_alarm(rtc, &alm);
 181         return (retval < 0) ? retval : n;
 182 }
 183 static DEVICE_ATTR(wakealarm, S_IRUGO | S_IWUSR,
 184                 rtc_sysfs_show_wakealarm, rtc_sysfs_set_wakealarm);
 185
 186
 187 /* The reason to trigger an alarm with no process watching it (via sysfs)
 188  * is its side effect:  waking from a system state like suspend-to-RAM or
 189  * suspend-to-disk.  So: no attribute unless that side effect is possible.
 190  * (Userspace may disable that mechanism later.)
 191  */
 192 static inline int rtc_does_wakealarm(struct rtc_device *rtc)
 193 {
 194         if (!device_can_wakeup(rtc->dev.parent))
 195                 return 0;
 196         return rtc->ops->set_alarm != NULL;
 197 }
 198
 199
 200 void rtc_sysfs_add_device(struct rtc_device *rtc)
 201 {
 202         int err;
 203
 204         /* not all RTCs support both alarms and wakeup */
 205         if (!rtc_does_wakealarm(rtc))
 206                 return;
 207
 208         err = device_create_file(&rtc->dev, &dev_attr_wakealarm);
 209         if (err)
 210                 dev_err(rtc->dev.parent,
 211                         "failed to create alarm attribute, %d\n", err);
 212 }
 213
 214 void rtc_sysfs_del_device(struct rtc_device *rtc)
 215 {
 216         /* REVISIT did we add it successfully? */
 217         if (rtc_does_wakealarm(rtc))
 218                 device_remove_file(&rtc->dev, &dev_attr_wakealarm);
 219 }
 220
 221 void __init rtc_sysfs_init(struct class *rtc_class)
 222 {
 223         rtc_class->dev_attrs = rtc_attrs;
 224 }