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 struct attribute *rtc_attrs[] = {
 126         &dev_attr_name.attr,
 127         &dev_attr_date.attr,
 128         &dev_attr_time.attr,
 129         &dev_attr_since_epoch.attr,
 130         &dev_attr_max_user_freq.attr,
 131         &dev_attr_hctosys.attr,
 132         NULL,
 133 };
 134 ATTRIBUTE_GROUPS(rtc);
 135
 136 static ssize_t
 137 rtc_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
 161 static ssize_t
 162 rtc_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         unsigned long push = 0;
 168         struct rtc_wkalrm alm;
 169         struct rtc_device *rtc = to_rtc_device(dev);
 170         char *buf_ptr;
 171         int adjust = 0;
 172
 173         /* Only request alarms that trigger in the future.  Disable them
 174          * by writing another time, e.g. 0 meaning Jan 1 1970 UTC.
 175          */
 176         retval = rtc_read_time(rtc, &alm.time);
 177         if (retval < 0)
 178                 return retval;
 179         rtc_tm_to_time(&alm.time, &now);
 180
 181         buf_ptr = (char *)buf;
 182         if (*buf_ptr == '+') {
 183                 buf_ptr++;
 184                 if (*buf_ptr == '=') {
 185                         buf_ptr++;
 186                         push = 1;
 187                 } else
 188                         adjust = 1;
 189         }
 190         alarm = simple_strtoul(buf_ptr, NULL, 0);
 191         if (adjust) {
 192                 alarm += now;
 193         }
 194         if (alarm > now || push) {
 195                 /* Avoid accidentally clobbering active alarms; we can't
 196                  * entirely prevent that here, without even the minimal
 197                  * locking from the /dev/rtcN api.
 198                  */
 199                 retval = rtc_read_alarm(rtc, &alm);
 200                 if (retval < 0)
 201                         return retval;
 202                 if (alm.enabled) {
 203                         if (push) {
 204                                 rtc_tm_to_time(&alm.time, &push);
 205                                 alarm += push;
 206                         } else
 207                                 return -EBUSY;
 208                 } else if (push)
 209                         return -EINVAL;
 210                 alm.enabled = 1;
 211         } else {
 212                 alm.enabled = 0;
 213
 214                 /* Provide a valid future alarm time.  Linux isn't EFI,
 215                  * this time won't be ignored when disabling the alarm.
 216                  */
 217                 alarm = now + 300;
 218         }
 219         rtc_time_to_tm(alarm, &alm.time);
 220
 221         retval = rtc_set_alarm(rtc, &alm);
 222         return (retval < 0) ? retval : n;
 223 }
 224 static DEVICE_ATTR(wakealarm, S_IRUGO | S_IWUSR,
 225                 rtc_sysfs_show_wakealarm, rtc_sysfs_set_wakealarm);
 226
 227
 228 /* The reason to trigger an alarm with no process watching it (via sysfs)
 229  * is its side effect:  waking from a system state like suspend-to-RAM or
 230  * suspend-to-disk.  So: no attribute unless that side effect is possible.
 231  * (Userspace may disable that mechanism later.)
 232  */
 233 static inline int rtc_does_wakealarm(struct rtc_device *rtc)
 234 {
 235         if (!device_can_wakeup(rtc->dev.parent))
 236                 return 0;
 237         return rtc->ops->set_alarm != NULL;
 238 }
 239
 240
 241 void rtc_sysfs_add_device(struct rtc_device *rtc)
 242 {
 243         int err;
 244
 245         /* not all RTCs support both alarms and wakeup */
 246         if (!rtc_does_wakealarm(rtc))
 247                 return;
 248
 249         err = device_create_file(&rtc->dev, &dev_attr_wakealarm);
 250         if (err)
 251                 dev_err(rtc->dev.parent,
 252                         "failed to create alarm attribute, %d\n", err);
 253 }
 254
 255 void rtc_sysfs_del_device(struct rtc_device *rtc)
 256 {
 257         /* REVISIT did we add it successfully? */
 258         if (rtc_does_wakealarm(rtc))
 259                 device_remove_file(&rtc->dev, &dev_attr_wakealarm);
 260 }
 261
 262 void __init rtc_sysfs_init(struct class *rtc_class)
 263 {
 264         rtc_class->dev_groups = rtc_groups;
 265 }