drivers/rtc/sysfs.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * RTC subsystem, sysfs interface
   4  *
   5  * Copyright (C) 2005 Tower Technologies
   6  * Author: Alessandro Zummo <a.zummo@towertech.it>
   7  */
   8
   9 #include <linux/module.h>
  10 #include <linux/rtc.h>
  11
  12 #include "rtc-core.h"
  13
  14 /* device attributes */
  15
  16 /*
  17  * NOTE:  RTC times displayed in sysfs use the RTC's timezone.  That's
  18  * ideally UTC.  However, PCs that also boot to MS-Windows normally use
  19  * the local time and change to match daylight savings time.  That affects
  20  * attributes including date, time, since_epoch, and wakealarm.
  21  */
  22
  23 static ssize_t
  24 name_show(struct device *dev, struct device_attribute *attr, char *buf)
  25 {
  26         return sprintf(buf, "%s %s\n", dev_driver_string(dev->parent),
  27                        dev_name(dev->parent));
  28 }
  29 static DEVICE_ATTR_RO(name);
  30
  31 static ssize_t
  32 date_show(struct device *dev, struct device_attribute *attr, char *buf)
  33 {
  34         ssize_t retval;
  35         struct rtc_time tm;
  36
  37         retval = rtc_read_time(to_rtc_device(dev), &tm);
  38         if (retval)
  39                 return retval;
  40
  41         return sprintf(buf, "%ptRd\n", &tm);
  42 }
  43 static DEVICE_ATTR_RO(date);
  44
  45 static ssize_t
  46 time_show(struct device *dev, struct device_attribute *attr, char *buf)
  47 {
  48         ssize_t retval;
  49         struct rtc_time tm;
  50
  51         retval = rtc_read_time(to_rtc_device(dev), &tm);
  52         if (retval)
  53                 return retval;
  54
  55         return sprintf(buf, "%ptRt\n", &tm);
  56 }
  57 static DEVICE_ATTR_RO(time);
  58
  59 static ssize_t
  60 since_epoch_show(struct device *dev, struct device_attribute *attr, char *buf)
  61 {
  62         ssize_t retval;
  63         struct rtc_time tm;
  64
  65         retval = rtc_read_time(to_rtc_device(dev), &tm);
  66         if (retval == 0) {
  67                 time64_t time;
  68
  69                 time = rtc_tm_to_time64(&tm);
  70                 retval = sprintf(buf, "%lld\n", time);
  71         }
  72
  73         return retval;
  74 }
  75 static DEVICE_ATTR_RO(since_epoch);
  76
  77 static ssize_t
  78 max_user_freq_show(struct device *dev, struct device_attribute *attr, char *buf)
  79 {
  80         return sprintf(buf, "%d\n", to_rtc_device(dev)->max_user_freq);
  81 }
  82
  83 static ssize_t
  84 max_user_freq_store(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;
  89         int err;
  90
  91         err = kstrtoul(buf, 0, &val);
  92         if (err)
  93                 return err;
  94
  95         if (val >= 4096 || val == 0)
  96                 return -EINVAL;
  97
  98         rtc->max_user_freq = (int)val;
  99
 100         return n;
 101 }
 102 static DEVICE_ATTR_RW(max_user_freq);
 103
 104 /**
 105  * rtc_sysfs_show_hctosys - indicate if the given RTC set the system time
 106  * @dev: The device that the attribute belongs to.
 107  * @attr: The attribute being read.
 108  * @buf: The result buffer.
 109  *
 110  * buf is "1" if the system clock was set by this RTC at the last
 111  * boot or resume event.
 112  */
 113 static ssize_t
 114 hctosys_show(struct device *dev, struct device_attribute *attr, char *buf)
 115 {
 116 #ifdef CONFIG_RTC_HCTOSYS_DEVICE
 117         if (rtc_hctosys_ret == 0 &&
 118             strcmp(dev_name(&to_rtc_device(dev)->dev),
 119                    CONFIG_RTC_HCTOSYS_DEVICE) == 0)
 120                 return sprintf(buf, "1\n");
 121 #endif
 122         return sprintf(buf, "0\n");
 123 }
 124 static DEVICE_ATTR_RO(hctosys);
 125
 126 static ssize_t
 127 wakealarm_show(struct device *dev, struct device_attribute *attr, char *buf)
 128 {
 129         ssize_t retval;
 130         time64_t alarm;
 131         struct rtc_wkalrm alm;
 132
 133         /* Don't show disabled alarms.  For uniformity, RTC alarms are
 134          * conceptually one-shot, even though some common RTCs (on PCs)
 135          * don't actually work that way.
 136          *
 137          * NOTE: RTC implementations where the alarm doesn't match an
 138          * exact YYYY-MM-DD HH:MM[:SS] date *must* disable their RTC
 139          * alarms after they trigger, to ensure one-shot semantics.
 140          */
 141         retval = rtc_read_alarm(to_rtc_device(dev), &alm);
 142         if (retval == 0 && alm.enabled) {
 143                 alarm = rtc_tm_to_time64(&alm.time);
 144                 retval = sprintf(buf, "%lld\n", alarm);
 145         }
 146
 147         return retval;
 148 }
 149
 150 static ssize_t
 151 wakealarm_store(struct device *dev, struct device_attribute *attr,
 152                 const char *buf, size_t n)
 153 {
 154         ssize_t retval;
 155         time64_t now, alarm;
 156         time64_t push = 0;
 157         struct rtc_wkalrm alm;
 158         struct rtc_device *rtc = to_rtc_device(dev);
 159         const char *buf_ptr;
 160         int adjust = 0;
 161
 162         /* Only request alarms that trigger in the future.  Disable them
 163          * by writing another time, e.g. 0 meaning Jan 1 1970 UTC.
 164          */
 165         retval = rtc_read_time(rtc, &alm.time);
 166         if (retval < 0)
 167                 return retval;
 168         now = rtc_tm_to_time64(&alm.time);
 169
 170         buf_ptr = buf;
 171         if (*buf_ptr == '+') {
 172                 buf_ptr++;
 173                 if (*buf_ptr == '=') {
 174                         buf_ptr++;
 175                         push = 1;
 176                 } else {
 177                         adjust = 1;
 178                 }
 179         }
 180         retval = kstrtos64(buf_ptr, 0, &alarm);
 181         if (retval)
 182                 return retval;
 183         if (adjust)
 184                 alarm += now;
 185         if (alarm > now || push) {
 186                 /* Avoid accidentally clobbering active alarms; we can't
 187                  * entirely prevent that here, without even the minimal
 188                  * locking from the /dev/rtcN api.
 189                  */
 190                 retval = rtc_read_alarm(rtc, &alm);
 191                 if (retval < 0)
 192                         return retval;
 193                 if (alm.enabled) {
 194                         if (push) {
 195                                 push = rtc_tm_to_time64(&alm.time);
 196                                 alarm += push;
 197                         } else
 198                                 return -EBUSY;
 199                 } else if (push)
 200                         return -EINVAL;
 201                 alm.enabled = 1;
 202         } else {
 203                 alm.enabled = 0;
 204
 205                 /* Provide a valid future alarm time.  Linux isn't EFI,
 206                  * this time won't be ignored when disabling the alarm.
 207                  */
 208                 alarm = now + 300;
 209         }
 210         rtc_time64_to_tm(alarm, &alm.time);
 211
 212         retval = rtc_set_alarm(rtc, &alm);
 213         return (retval < 0) ? retval : n;
 214 }
 215 static DEVICE_ATTR_RW(wakealarm);
 216
 217 static ssize_t
 218 offset_show(struct device *dev, struct device_attribute *attr, char *buf)
 219 {
 220         ssize_t retval;
 221         long offset;
 222
 223         retval = rtc_read_offset(to_rtc_device(dev), &offset);
 224         if (retval == 0)
 225                 retval = sprintf(buf, "%ld\n", offset);
 226
 227         return retval;
 228 }
 229
 230 static ssize_t
 231 offset_store(struct device *dev, struct device_attribute *attr,
 232              const char *buf, size_t n)
 233 {
 234         ssize_t retval;
 235         long offset;
 236
 237         retval = kstrtol(buf, 10, &offset);
 238         if (retval == 0)
 239                 retval = rtc_set_offset(to_rtc_device(dev), offset);
 240
 241         return (retval < 0) ? retval : n;
 242 }
 243 static DEVICE_ATTR_RW(offset);
 244
 245 static ssize_t
 246 range_show(struct device *dev, struct device_attribute *attr, char *buf)
 247 {
 248         return sprintf(buf, "[%lld,%llu]\n", to_rtc_device(dev)->range_min,
 249                        to_rtc_device(dev)->range_max);
 250 }
 251 static DEVICE_ATTR_RO(range);
 252
 253 static struct attribute *rtc_attrs[] = {
 254         &dev_attr_name.attr,
 255         &dev_attr_date.attr,
 256         &dev_attr_time.attr,
 257         &dev_attr_since_epoch.attr,
 258         &dev_attr_max_user_freq.attr,
 259         &dev_attr_hctosys.attr,
 260         &dev_attr_wakealarm.attr,
 261         &dev_attr_offset.attr,
 262         &dev_attr_range.attr,
 263         NULL,
 264 };
 265
 266 /* The reason to trigger an alarm with no process watching it (via sysfs)
 267  * is its side effect:  waking from a system state like suspend-to-RAM or
 268  * suspend-to-disk.  So: no attribute unless that side effect is possible.
 269  * (Userspace may disable that mechanism later.)
 270  */
 271 static bool rtc_does_wakealarm(struct rtc_device *rtc)
 272 {
 273         if (!device_can_wakeup(rtc->dev.parent))
 274                 return false;
 275
 276         return rtc->ops->set_alarm != NULL;
 277 }
 278
 279 static umode_t rtc_attr_is_visible(struct kobject *kobj,
 280                                    struct attribute *attr, int n)
 281 {
 282         struct device *dev = kobj_to_dev(kobj);
 283         struct rtc_device *rtc = to_rtc_device(dev);
 284         umode_t mode = attr->mode;
 285
 286         if (attr == &dev_attr_wakealarm.attr) {
 287                 if (!rtc_does_wakealarm(rtc))
 288                         mode = 0;
 289         } else if (attr == &dev_attr_offset.attr) {
 290                 if (!rtc->ops->set_offset)
 291                         mode = 0;
 292         } else if (attr == &dev_attr_range.attr) {
 293                 if (!(rtc->range_max - rtc->range_min))
 294                         mode = 0;
 295         }
 296
 297         return mode;
 298 }
 299
 300 static struct attribute_group rtc_attr_group = {
 301         .is_visible     = rtc_attr_is_visible,
 302         .attrs          = rtc_attrs,
 303 };
 304
 305 static const struct attribute_group *rtc_attr_groups[] = {
 306         &rtc_attr_group,
 307         NULL
 308 };
 309
 310 const struct attribute_group **rtc_get_dev_attribute_groups(void)
 311 {
 312         return rtc_attr_groups;
 313 }
 314
 315 int rtc_add_groups(struct rtc_device *rtc, const struct attribute_group **grps)
 316 {
 317         size_t old_cnt = 0, add_cnt = 0, new_cnt;
 318         const struct attribute_group **groups, **old;
 319
 320         if (rtc->registered)
 321                 return -EINVAL;
 322         if (!grps)
 323                 return -EINVAL;
 324
 325         groups = rtc->dev.groups;
 326         if (groups)
 327                 for (; *groups; groups++)
 328                         old_cnt++;
 329
 330         for (groups = grps; *groups; groups++)
 331                 add_cnt++;
 332
 333         new_cnt = old_cnt + add_cnt + 1;
 334         groups = devm_kcalloc(&rtc->dev, new_cnt, sizeof(*groups), GFP_KERNEL);
 335         if (!groups)
 336                 return -ENOMEM;
 337         memcpy(groups, rtc->dev.groups, old_cnt * sizeof(*groups));
 338         memcpy(groups + old_cnt, grps, add_cnt * sizeof(*groups));
 339         groups[old_cnt + add_cnt] = NULL;
 340
 341         old = rtc->dev.groups;
 342         rtc->dev.groups = groups;
 343         if (old && old != rtc_attr_groups)
 344                 devm_kfree(&rtc->dev, old);
 345
 346         return 0;
 347 }
 348 EXPORT_SYMBOL(rtc_add_groups);
 349
 350 int rtc_add_group(struct rtc_device *rtc, const struct attribute_group *grp)
 351 {
 352         const struct attribute_group *groups[] = { grp, NULL };
 353
 354         return rtc_add_groups(rtc, groups);
 355 }
 356 EXPORT_SYMBOL(rtc_add_group);