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 static ssize_t
  21 rtc_sysfs_show_name(struct device *dev, struct device_attribute *attr,
  22                 char *buf)
  23 {
  24         return sprintf(buf, "%s\n", to_rtc_device(dev)->name);
  25 }
  26
  27 static ssize_t
  28 rtc_sysfs_show_date(struct device *dev, struct device_attribute *attr,
  29                 char *buf)
  30 {
  31         ssize_t retval;
  32         struct rtc_time tm;
  33
  34         retval = rtc_read_time(to_rtc_device(dev), &tm);
  35         if (retval == 0) {
  36                 retval = sprintf(buf, "%04d-%02d-%02d\n",
  37                         tm.tm_year + 1900, tm.tm_mon + 1, tm.tm_mday);
  38         }
  39
  40         return retval;
  41 }
  42
  43 static ssize_t
  44 rtc_sysfs_show_time(struct device *dev, struct device_attribute *attr,
  45                 char *buf)
  46 {
  47         ssize_t retval;
  48         struct rtc_time tm;
  49
  50         retval = rtc_read_time(to_rtc_device(dev), &tm);
  51         if (retval == 0) {
  52                 retval = sprintf(buf, "%02d:%02d:%02d\n",
  53                         tm.tm_hour, tm.tm_min, tm.tm_sec);
  54         }
  55
  56         return retval;
  57 }
  58
  59 static ssize_t
  60 rtc_sysfs_show_since_epoch(struct device *dev, struct device_attribute *attr,
  61                 char *buf)
  62 {
  63         ssize_t retval;
  64         struct rtc_time tm;
  65
  66         retval = rtc_read_time(to_rtc_device(dev), &tm);
  67         if (retval == 0) {
  68                 unsigned long time;
  69                 rtc_tm_to_time(&tm, &time);
  70                 retval = sprintf(buf, "%lu\n", time);
  71         }
  72
  73         return retval;
  74 }
  75
  76 static ssize_t
  77 rtc_sysfs_show_max_user_freq(struct device *dev, struct device_attribute *attr,
  78                 char *buf)
  79 {
  80         return sprintf(buf, "%d\n", to_rtc_device(dev)->max_user_freq);
  81 }
  82
  83 static ssize_t
  84 rtc_sysfs_set_max_user_freq(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 = simple_strtoul(buf, NULL, 0);
  89
  90         if (val >= 4096 || val == 0)
  91                 return -EINVAL;
  92
  93         rtc->max_user_freq = (int)val;
  94
  95         return n;
  96 }
  97
  98 static struct device_attribute rtc_attrs[] = {
  99         __ATTR(name, S_IRUGO, rtc_sysfs_show_name, NULL),
 100         __ATTR(date, S_IRUGO, rtc_sysfs_show_date, NULL),
 101         __ATTR(time, S_IRUGO, rtc_sysfs_show_time, NULL),
 102         __ATTR(since_epoch, S_IRUGO, rtc_sysfs_show_since_epoch, NULL),
 103         __ATTR(max_user_freq, S_IRUGO | S_IWUSR, rtc_sysfs_show_max_user_freq,
 104                         rtc_sysfs_set_max_user_freq),
 105         { },
 106 };
 107
 108 static ssize_t
 109 rtc_sysfs_show_wakealarm(struct device *dev, struct device_attribute *attr,
 110                 char *buf)
 111 {
 112         ssize_t retval;
 113         unsigned long alarm;
 114         struct rtc_wkalrm alm;
 115
 116         /* Don't show disabled alarms; but the RTC could leave the
 117          * alarm enabled after it's already triggered.  Alarms are
 118          * conceptually one-shot, even though some common hardware
 119          * (PCs) doesn't actually work that way.
 120          *
 121          * REVISIT maybe we should require RTC implementations to
 122          * disable the RTC alarm after it triggers, for uniformity.
 123          */
 124         retval = rtc_read_alarm(to_rtc_device(dev), &alm);
 125         if (retval == 0 && alm.enabled) {
 126                 rtc_tm_to_time(&alm.time, &alarm);
 127                 retval = sprintf(buf, "%lu\n", alarm);
 128         }
 129
 130         return retval;
 131 }
 132
 133 static ssize_t
 134 rtc_sysfs_set_wakealarm(struct device *dev, struct device_attribute *attr,
 135                 const char *buf, size_t n)
 136 {
 137         ssize_t retval;
 138         unsigned long now, alarm;
 139         struct rtc_wkalrm alm;
 140         struct rtc_device *rtc = to_rtc_device(dev);
 141
 142         /* Only request alarms that trigger in the future.  Disable them
 143          * by writing another time, e.g. 0 meaning Jan 1 1970 UTC.
 144          */
 145         retval = rtc_read_time(rtc, &alm.time);
 146         if (retval < 0)
 147                 return retval;
 148         rtc_tm_to_time(&alm.time, &now);
 149
 150         alarm = simple_strtoul(buf, NULL, 0);
 151         if (alarm > now) {
 152                 /* Avoid accidentally clobbering active alarms; we can't
 153                  * entirely prevent that here, without even the minimal
 154                  * locking from the /dev/rtcN api.
 155                  */
 156                 retval = rtc_read_alarm(rtc, &alm);
 157                 if (retval < 0)
 158                         return retval;
 159                 if (alm.enabled)
 160                         return -EBUSY;
 161
 162                 alm.enabled = 1;
 163         } else {
 164                 alm.enabled = 0;
 165
 166                 /* Provide a valid future alarm time.  Linux isn't EFI,
 167                  * this time won't be ignored when disabling the alarm.
 168                  */
 169                 alarm = now + 300;
 170         }
 171         rtc_time_to_tm(alarm, &alm.time);
 172
 173         retval = rtc_set_alarm(rtc, &alm);
 174         return (retval < 0) ? retval : n;
 175 }
 176 static DEVICE_ATTR(wakealarm, S_IRUGO | S_IWUSR,
 177                 rtc_sysfs_show_wakealarm, rtc_sysfs_set_wakealarm);
 178
 179
 180 /* The reason to trigger an alarm with no process watching it (via sysfs)
 181  * is its side effect:  waking from a system state like suspend-to-RAM or
 182  * suspend-to-disk.  So: no attribute unless that side effect is possible.
 183  * (Userspace may disable that mechanism later.)
 184  */
 185 static inline int rtc_does_wakealarm(struct rtc_device *rtc)
 186 {
 187         if (!device_can_wakeup(rtc->dev.parent))
 188                 return 0;
 189         return rtc->ops->set_alarm != NULL;
 190 }
 191
 192
 193 void rtc_sysfs_add_device(struct rtc_device *rtc)
 194 {
 195         int err;
 196
 197         /* not all RTCs support both alarms and wakeup */
 198         if (!rtc_does_wakealarm(rtc))
 199                 return;
 200
 201         err = device_create_file(&rtc->dev, &dev_attr_wakealarm);
 202         if (err)
 203                 dev_err(rtc->dev.parent,
 204                         "failed to create alarm attribute, %d\n", err);
 205 }
 206
 207 void rtc_sysfs_del_device(struct rtc_device *rtc)
 208 {
 209         /* REVISIT did we add it successfully? */
 210         if (rtc_does_wakealarm(rtc))
 211                 device_remove_file(&rtc->dev, &dev_attr_wakealarm);
 212 }
 213
 214 void __init rtc_sysfs_init(struct class *rtc_class)
 215 {
 216         rtc_class->dev_attrs = rtc_attrs;
 217 }