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;
  95         int err;
  96
  97         err = kstrtoul(buf, 0, &val);
  98         if (err)
  99                 return err;
 100
 101         if (val >= 4096 || val == 0)
 102                 return -EINVAL;
 103
 104         rtc->max_user_freq = (int)val;
 105
 106         return n;
 107 }
 108 static DEVICE_ATTR_RW(max_user_freq);
 109
 110 /**
 111  * rtc_sysfs_show_hctosys - indicate if the given RTC set the system time
 112  *
 113  * Returns 1 if the system clock was set by this RTC at the last
 114  * boot or resume event.
 115  */
 116 static ssize_t
 117 hctosys_show(struct device *dev, struct device_attribute *attr, char *buf)
 118 {
 119 #ifdef CONFIG_RTC_HCTOSYS_DEVICE
 120         if (rtc_hctosys_ret == 0 &&
 121                         strcmp(dev_name(&to_rtc_device(dev)->dev),
 122                                 CONFIG_RTC_HCTOSYS_DEVICE) == 0)
 123                 return sprintf(buf, "1\n");
 124         else
 125 #endif
 126                 return sprintf(buf, "0\n");
 127 }
 128 static DEVICE_ATTR_RO(hctosys);
 129
 130 static ssize_t
 131 wakealarm_show(struct device *dev, struct device_attribute *attr, char *buf)
 132 {
 133         ssize_t retval;
 134         unsigned long alarm;
 135         struct rtc_wkalrm alm;
 136
 137         /* Don't show disabled alarms.  For uniformity, RTC alarms are
 138          * conceptually one-shot, even though some common RTCs (on PCs)
 139          * don't actually work that way.
 140          *
 141          * NOTE: RTC implementations where the alarm doesn't match an
 142          * exact YYYY-MM-DD HH:MM[:SS] date *must* disable their RTC
 143          * alarms after they trigger, to ensure one-shot semantics.
 144          */
 145         retval = rtc_read_alarm(to_rtc_device(dev), &alm);
 146         if (retval == 0 && alm.enabled) {
 147                 rtc_tm_to_time(&alm.time, &alarm);
 148                 retval = sprintf(buf, "%lu\n", alarm);
 149         }
 150
 151         return retval;
 152 }
 153
 154 static ssize_t
 155 wakealarm_store(struct device *dev, struct device_attribute *attr,
 156                 const char *buf, size_t n)
 157 {
 158         ssize_t retval;
 159         unsigned long now, alarm;
 160         unsigned long push = 0;
 161         struct rtc_wkalrm alm;
 162         struct rtc_device *rtc = to_rtc_device(dev);
 163         char *buf_ptr;
 164         int adjust = 0;
 165
 166         /* Only request alarms that trigger in the future.  Disable them
 167          * by writing another time, e.g. 0 meaning Jan 1 1970 UTC.
 168          */
 169         retval = rtc_read_time(rtc, &alm.time);
 170         if (retval < 0)
 171                 return retval;
 172         rtc_tm_to_time(&alm.time, &now);
 173
 174         buf_ptr = (char *)buf;
 175         if (*buf_ptr == '+') {
 176                 buf_ptr++;
 177                 if (*buf_ptr == '=') {
 178                         buf_ptr++;
 179                         push = 1;
 180                 } else
 181                         adjust = 1;
 182         }
 183         retval = kstrtoul(buf_ptr, 0, &alarm);
 184         if (retval)
 185                 return retval;
 186         if (adjust) {
 187                 alarm += now;
 188         }
 189         if (alarm > now || push) {
 190                 /* Avoid accidentally clobbering active alarms; we can't
 191                  * entirely prevent that here, without even the minimal
 192                  * locking from the /dev/rtcN api.
 193                  */
 194                 retval = rtc_read_alarm(rtc, &alm);
 195                 if (retval < 0)
 196                         return retval;
 197                 if (alm.enabled) {
 198                         if (push) {
 199                                 rtc_tm_to_time(&alm.time, &push);
 200                                 alarm += push;
 201                         } else
 202                                 return -EBUSY;
 203                 } else if (push)
 204                         return -EINVAL;
 205                 alm.enabled = 1;
 206         } else {
 207                 alm.enabled = 0;
 208
 209                 /* Provide a valid future alarm time.  Linux isn't EFI,
 210                  * this time won't be ignored when disabling the alarm.
 211                  */
 212                 alarm = now + 300;
 213         }
 214         rtc_time_to_tm(alarm, &alm.time);
 215
 216         retval = rtc_set_alarm(rtc, &alm);
 217         return (retval < 0) ? retval : n;
 218 }
 219 static DEVICE_ATTR_RW(wakealarm);
 220
 221 static ssize_t
 222 offset_show(struct device *dev, struct device_attribute *attr, char *buf)
 223 {
 224         ssize_t retval;
 225         long offset;
 226
 227         retval = rtc_read_offset(to_rtc_device(dev), &offset);
 228         if (retval == 0)
 229                 retval = sprintf(buf, "%ld\n", offset);
 230
 231         return retval;
 232 }
 233
 234 static ssize_t
 235 offset_store(struct device *dev, struct device_attribute *attr,
 236              const char *buf, size_t n)
 237 {
 238         ssize_t retval;
 239         long offset;
 240
 241         retval = kstrtol(buf, 10, &offset);
 242         if (retval == 0)
 243                 retval = rtc_set_offset(to_rtc_device(dev), offset);
 244
 245         return (retval < 0) ? retval : n;
 246 }
 247 static DEVICE_ATTR_RW(offset);
 248
 249 static struct attribute *rtc_attrs[] = {
 250         &dev_attr_name.attr,
 251         &dev_attr_date.attr,
 252         &dev_attr_time.attr,
 253         &dev_attr_since_epoch.attr,
 254         &dev_attr_max_user_freq.attr,
 255         &dev_attr_hctosys.attr,
 256         &dev_attr_wakealarm.attr,
 257         &dev_attr_offset.attr,
 258         NULL,
 259 };
 260
 261 /* The reason to trigger an alarm with no process watching it (via sysfs)
 262  * is its side effect:  waking from a system state like suspend-to-RAM or
 263  * suspend-to-disk.  So: no attribute unless that side effect is possible.
 264  * (Userspace may disable that mechanism later.)
 265  */
 266 static bool rtc_does_wakealarm(struct rtc_device *rtc)
 267 {
 268         if (!device_can_wakeup(rtc->dev.parent))
 269                 return false;
 270
 271         return rtc->ops->set_alarm != NULL;
 272 }
 273
 274 static umode_t rtc_attr_is_visible(struct kobject *kobj,
 275                                    struct attribute *attr, int n)
 276 {
 277         struct device *dev = container_of(kobj, struct device, kobj);
 278         struct rtc_device *rtc = to_rtc_device(dev);
 279         umode_t mode = attr->mode;
 280
 281         if (attr == &dev_attr_wakealarm.attr) {
 282                 if (!rtc_does_wakealarm(rtc))
 283                         mode = 0;
 284         } else if (attr == &dev_attr_offset.attr) {
 285                 if (!rtc->ops->set_offset)
 286                         mode = 0;
 287         }
 288
 289         return mode;
 290 }
 291
 292 static struct attribute_group rtc_attr_group = {
 293         .is_visible     = rtc_attr_is_visible,
 294         .attrs          = rtc_attrs,
 295 };
 296
 297 static const struct attribute_group *rtc_attr_groups[] = {
 298         &rtc_attr_group,
 299         NULL
 300 };
 301
 302 const struct attribute_group **rtc_get_dev_attribute_groups(void)
 303 {
 304         return rtc_attr_groups;
 305 }