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 %s\n", dev_driver_string(dev->parent),
  31                        dev_name(dev->parent));
  32 }
  33 static DEVICE_ATTR_RO(name);
  34
  35 static ssize_t
  36 date_show(struct device *dev, struct device_attribute *attr, 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 static DEVICE_ATTR_RO(date);
  50
  51 static ssize_t
  52 time_show(struct device *dev, struct device_attribute *attr, 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 static DEVICE_ATTR_RO(time);
  66
  67 static ssize_t
  68 since_epoch_show(struct device *dev, struct device_attribute *attr, 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                 time64_t time;
  76
  77                 time = rtc_tm_to_time64(&tm);
  78                 retval = sprintf(buf, "%lld\n", time);
  79         }
  80
  81         return retval;
  82 }
  83 static DEVICE_ATTR_RO(since_epoch);
  84
  85 static ssize_t
  86 max_user_freq_show(struct device *dev, struct device_attribute *attr, char *buf)
  87 {
  88         return sprintf(buf, "%d\n", to_rtc_device(dev)->max_user_freq);
  89 }
  90
  91 static ssize_t
  92 max_user_freq_store(struct device *dev, struct device_attribute *attr,
  93                 const char *buf, size_t n)
  94 {
  95         struct rtc_device *rtc = to_rtc_device(dev);
  96         unsigned long val;
  97         int err;
  98
  99         err = kstrtoul(buf, 0, &val);
 100         if (err)
 101                 return err;
 102
 103         if (val >= 4096 || val == 0)
 104                 return -EINVAL;
 105
 106         rtc->max_user_freq = (int)val;
 107
 108         return n;
 109 }
 110 static DEVICE_ATTR_RW(max_user_freq);
 111
 112 /**
 113  * rtc_sysfs_show_hctosys - indicate if the given RTC set the system time
 114  *
 115  * Returns 1 if the system clock was set by this RTC at the last
 116  * boot or resume event.
 117  */
 118 static ssize_t
 119 hctosys_show(struct device *dev, struct device_attribute *attr, char *buf)
 120 {
 121 #ifdef CONFIG_RTC_HCTOSYS_DEVICE
 122         if (rtc_hctosys_ret == 0 &&
 123                         strcmp(dev_name(&to_rtc_device(dev)->dev),
 124                                 CONFIG_RTC_HCTOSYS_DEVICE) == 0)
 125                 return sprintf(buf, "1\n");
 126         else
 127 #endif
 128                 return sprintf(buf, "0\n");
 129 }
 130 static DEVICE_ATTR_RO(hctosys);
 131
 132 static ssize_t
 133 wakealarm_show(struct device *dev, struct device_attribute *attr, char *buf)
 134 {
 135         ssize_t retval;
 136         time64_t alarm;
 137         struct rtc_wkalrm alm;
 138
 139         /* Don't show disabled alarms.  For uniformity, RTC alarms are
 140          * conceptually one-shot, even though some common RTCs (on PCs)
 141          * don't actually work that way.
 142          *
 143          * NOTE: RTC implementations where the alarm doesn't match an
 144          * exact YYYY-MM-DD HH:MM[:SS] date *must* disable their RTC
 145          * alarms after they trigger, to ensure one-shot semantics.
 146          */
 147         retval = rtc_read_alarm(to_rtc_device(dev), &alm);
 148         if (retval == 0 && alm.enabled) {
 149                 alarm = rtc_tm_to_time64(&alm.time);
 150                 retval = sprintf(buf, "%lld\n", alarm);
 151         }
 152
 153         return retval;
 154 }
 155
 156 static ssize_t
 157 wakealarm_store(struct device *dev, struct device_attribute *attr,
 158                 const char *buf, size_t n)
 159 {
 160         ssize_t retval;
 161         time64_t now, alarm;
 162         time64_t push = 0;
 163         struct rtc_wkalrm alm;
 164         struct rtc_device *rtc = to_rtc_device(dev);
 165         const char *buf_ptr;
 166         int adjust = 0;
 167
 168         /* Only request alarms that trigger in the future.  Disable them
 169          * by writing another time, e.g. 0 meaning Jan 1 1970 UTC.
 170          */
 171         retval = rtc_read_time(rtc, &alm.time);
 172         if (retval < 0)
 173                 return retval;
 174         now = rtc_tm_to_time64(&alm.time);
 175
 176         buf_ptr = buf;
 177         if (*buf_ptr == '+') {
 178                 buf_ptr++;
 179                 if (*buf_ptr == '=') {
 180                         buf_ptr++;
 181                         push = 1;
 182                 } else
 183                         adjust = 1;
 184         }
 185         retval = kstrtos64(buf_ptr, 0, &alarm);
 186         if (retval)
 187                 return retval;
 188         if (adjust) {
 189                 alarm += now;
 190         }
 191         if (alarm > now || push) {
 192                 /* Avoid accidentally clobbering active alarms; we can't
 193                  * entirely prevent that here, without even the minimal
 194                  * locking from the /dev/rtcN api.
 195                  */
 196                 retval = rtc_read_alarm(rtc, &alm);
 197                 if (retval < 0)
 198                         return retval;
 199                 if (alm.enabled) {
 200                         if (push) {
 201                                 push = rtc_tm_to_time64(&alm.time);
 202                                 alarm += push;
 203                         } else
 204                                 return -EBUSY;
 205                 } else if (push)
 206                         return -EINVAL;
 207                 alm.enabled = 1;
 208         } else {
 209                 alm.enabled = 0;
 210
 211                 /* Provide a valid future alarm time.  Linux isn't EFI,
 212                  * this time won't be ignored when disabling the alarm.
 213                  */
 214                 alarm = now + 300;
 215         }
 216         rtc_time64_to_tm(alarm, &alm.time);
 217
 218         retval = rtc_set_alarm(rtc, &alm);
 219         return (retval < 0) ? retval : n;
 220 }
 221 static DEVICE_ATTR_RW(wakealarm);
 222
 223 static ssize_t
 224 offset_show(struct device *dev, struct device_attribute *attr, char *buf)
 225 {
 226         ssize_t retval;
 227         long offset;
 228
 229         retval = rtc_read_offset(to_rtc_device(dev), &offset);
 230         if (retval == 0)
 231                 retval = sprintf(buf, "%ld\n", offset);
 232
 233         return retval;
 234 }
 235
 236 static ssize_t
 237 offset_store(struct device *dev, struct device_attribute *attr,
 238              const char *buf, size_t n)
 239 {
 240         ssize_t retval;
 241         long offset;
 242
 243         retval = kstrtol(buf, 10, &offset);
 244         if (retval == 0)
 245                 retval = rtc_set_offset(to_rtc_device(dev), offset);
 246
 247         return (retval < 0) ? retval : n;
 248 }
 249 static DEVICE_ATTR_RW(offset);
 250
 251 static struct attribute *rtc_attrs[] = {
 252         &dev_attr_name.attr,
 253         &dev_attr_date.attr,
 254         &dev_attr_time.attr,
 255         &dev_attr_since_epoch.attr,
 256         &dev_attr_max_user_freq.attr,
 257         &dev_attr_hctosys.attr,
 258         &dev_attr_wakealarm.attr,
 259         &dev_attr_offset.attr,
 260         NULL,
 261 };
 262
 263 /* The reason to trigger an alarm with no process watching it (via sysfs)
 264  * is its side effect:  waking from a system state like suspend-to-RAM or
 265  * suspend-to-disk.  So: no attribute unless that side effect is possible.
 266  * (Userspace may disable that mechanism later.)
 267  */
 268 static bool rtc_does_wakealarm(struct rtc_device *rtc)
 269 {
 270         if (!device_can_wakeup(rtc->dev.parent))
 271                 return false;
 272
 273         return rtc->ops->set_alarm != NULL;
 274 }
 275
 276 static umode_t rtc_attr_is_visible(struct kobject *kobj,
 277                                    struct attribute *attr, int n)
 278 {
 279         struct device *dev = container_of(kobj, struct device, kobj);
 280         struct rtc_device *rtc = to_rtc_device(dev);
 281         umode_t mode = attr->mode;
 282
 283         if (attr == &dev_attr_wakealarm.attr) {
 284                 if (!rtc_does_wakealarm(rtc))
 285                         mode = 0;
 286         } else if (attr == &dev_attr_offset.attr) {
 287                 if (!rtc->ops->set_offset)
 288                         mode = 0;
 289         }
 290
 291         return mode;
 292 }
 293
 294 static struct attribute_group rtc_attr_group = {
 295         .is_visible     = rtc_attr_is_visible,
 296         .attrs          = rtc_attrs,
 297 };
 298
 299 static const struct attribute_group *rtc_attr_groups[] = {
 300         &rtc_attr_group,
 301         NULL
 302 };
 303
 304 const struct attribute_group **rtc_get_dev_attribute_groups(void)
 305 {
 306         return rtc_attr_groups;
 307 }