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 struct device_attribute rtc_attrs[] = {
  77         __ATTR(name, S_IRUGO, rtc_sysfs_show_name, NULL),
  78         __ATTR(date, S_IRUGO, rtc_sysfs_show_date, NULL),
  79         __ATTR(time, S_IRUGO, rtc_sysfs_show_time, NULL),
  80         __ATTR(since_epoch, S_IRUGO, rtc_sysfs_show_since_epoch, NULL),
  81         { },
  82 };
  83
  84 static ssize_t
  85 rtc_sysfs_show_wakealarm(struct device *dev, struct device_attribute *attr,
  86                 char *buf)
  87 {
  88         ssize_t retval;
  89         unsigned long alarm;
  90         struct rtc_wkalrm alm;
  91
  92         /* Don't show disabled alarms; but the RTC could leave the
  93          * alarm enabled after it's already triggered.  Alarms are
  94          * conceptually one-shot, even though some common hardware
  95          * (PCs) doesn't actually work that way.
  96          *
  97          * REVISIT maybe we should require RTC implementations to
  98          * disable the RTC alarm after it triggers, for uniformity.
  99          */
 100         retval = rtc_read_alarm(to_rtc_device(dev), &alm);
 101         if (retval == 0 && alm.enabled) {
 102                 rtc_tm_to_time(&alm.time, &alarm);
 103                 retval = sprintf(buf, "%lu\n", alarm);
 104         }
 105
 106         return retval;
 107 }
 108
 109 static ssize_t
 110 rtc_sysfs_set_wakealarm(struct device *dev, struct device_attribute *attr,
 111                 const char *buf, size_t n)
 112 {
 113         ssize_t retval;
 114         unsigned long now, alarm;
 115         struct rtc_wkalrm alm;
 116         struct rtc_device *rtc = to_rtc_device(dev);
 117
 118         /* Only request alarms that trigger in the future.  Disable them
 119          * by writing another time, e.g. 0 meaning Jan 1 1970 UTC.
 120          */
 121         retval = rtc_read_time(rtc, &alm.time);
 122         if (retval < 0)
 123                 return retval;
 124         rtc_tm_to_time(&alm.time, &now);
 125
 126         alarm = simple_strtoul(buf, NULL, 0);
 127         if (alarm > now) {
 128                 /* Avoid accidentally clobbering active alarms; we can't
 129                  * entirely prevent that here, without even the minimal
 130                  * locking from the /dev/rtcN api.
 131                  */
 132                 retval = rtc_read_alarm(rtc, &alm);
 133                 if (retval < 0)
 134                         return retval;
 135                 if (alm.enabled)
 136                         return -EBUSY;
 137
 138                 alm.enabled = 1;
 139         } else {
 140                 alm.enabled = 0;
 141
 142                 /* Provide a valid future alarm time.  Linux isn't EFI,
 143                  * this time won't be ignored when disabling the alarm.
 144                  */
 145                 alarm = now + 300;
 146         }
 147         rtc_time_to_tm(alarm, &alm.time);
 148
 149         retval = rtc_set_alarm(rtc, &alm);
 150         return (retval < 0) ? retval : n;
 151 }
 152 static DEVICE_ATTR(wakealarm, S_IRUGO | S_IWUSR,
 153                 rtc_sysfs_show_wakealarm, rtc_sysfs_set_wakealarm);
 154
 155
 156 /* The reason to trigger an alarm with no process watching it (via sysfs)
 157  * is its side effect:  waking from a system state like suspend-to-RAM or
 158  * suspend-to-disk.  So: no attribute unless that side effect is possible.
 159  * (Userspace may disable that mechanism later.)
 160  */
 161 static inline int rtc_does_wakealarm(struct rtc_device *rtc)
 162 {
 163         if (!device_can_wakeup(rtc->dev.parent))
 164                 return 0;
 165         return rtc->ops->set_alarm != NULL;
 166 }
 167
 168
 169 void rtc_sysfs_add_device(struct rtc_device *rtc)
 170 {
 171         int err;
 172
 173         /* not all RTCs support both alarms and wakeup */
 174         if (!rtc_does_wakealarm(rtc))
 175                 return;
 176
 177         err = device_create_file(&rtc->dev, &dev_attr_wakealarm);
 178         if (err)
 179                 dev_err(rtc->dev.parent, "failed to create "
 180                                 "alarm attribute, %d",
 181                                 err);
 182 }
 183
 184 void rtc_sysfs_del_device(struct rtc_device *rtc)
 185 {
 186         /* REVISIT did we add it successfully? */
 187         if (rtc_does_wakealarm(rtc))
 188                 device_remove_file(&rtc->dev, &dev_attr_wakealarm);
 189 }
 190
 191 void __init rtc_sysfs_init(struct class *rtc_class)
 192 {
 193         rtc_class->dev_attrs = rtc_attrs;
 194 }