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/kstrtox.h>
  10 #include <linux/module.h>
  11 #include <linux/rtc.h>
  12
  13 #include "rtc-core.h"
  14
  15 /* device attributes */
  16
  17 /*
  18  * NOTE:  RTC times displayed in sysfs use the RTC's timezone.  That's
  19  * ideally UTC.  However, PCs that also boot to MS-Windows normally use
  20  * the local time and change to match daylight savings time.  That affects
  21  * attributes including date, time, since_epoch, and wakealarm.
  22  */
  23
  24 static ssize_t
  25 name_show(struct device *dev, struct device_attribute *attr, char *buf)
  26 {
  27         return sprintf(buf, "%s %s\n", dev_driver_string(dev->parent),
  28                        dev_name(dev->parent));
  29 }
  30 static DEVICE_ATTR_RO(name);
  31
  32 static ssize_t
  33 date_show(struct device *dev, struct device_attribute *attr, char *buf)
  34 {
  35         ssize_t retval;
  36         struct rtc_time tm;
  37
  38         retval = rtc_read_time(to_rtc_device(dev), &tm);
  39         if (retval)
  40                 return retval;
  41
  42         return sprintf(buf, "%ptRd\n", &tm);
  43 }
  44 static DEVICE_ATTR_RO(date);
  45
  46 static ssize_t
  47 time_show(struct device *dev, struct device_attribute *attr, char *buf)
  48 {
  49         ssize_t retval;
  50         struct rtc_time tm;
  51
  52         retval = rtc_read_time(to_rtc_device(dev), &tm);
  53         if (retval)
  54                 return retval;
  55
  56         return sprintf(buf, "%ptRt\n", &tm);
  57 }
  58 static DEVICE_ATTR_RO(time);
  59
  60 static ssize_t
  61 since_epoch_show(struct device *dev, struct device_attribute *attr, 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                 time64_t time;
  69
  70                 time = rtc_tm_to_time64(&tm);
  71                 retval = sprintf(buf, "%lld\n", time);
  72         }
  73
  74         return retval;
  75 }
  76 static DEVICE_ATTR_RO(since_epoch);
  77
  78 static ssize_t
  79 max_user_freq_show(struct device *dev, struct device_attribute *attr, char *buf)
  80 {
  81         return sprintf(buf, "%d\n", to_rtc_device(dev)->max_user_freq);
  82 }
  83
  84 static ssize_t
  85 max_user_freq_store(struct device *dev, struct device_attribute *attr,
  86                     const char *buf, size_t n)
  87 {
  88         struct rtc_device *rtc = to_rtc_device(dev);
  89         unsigned long val;
  90         int err;
  91
  92         err = kstrtoul(buf, 0, &val);
  93         if (err)
  94                 return err;
  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  * hctosys_show - indicate if the given RTC set the system time
 107  * @dev: The device that the attribute belongs to.
 108  * @attr: The attribute being read.
 109  * @buf: The result buffer.
 110  *
 111  * buf is "1" if the system clock was set by this RTC at the last
 112  * boot or resume event.
 113  */
 114 static ssize_t
 115 hctosys_show(struct device *dev, struct device_attribute *attr, char *buf)
 116 {
 117 #ifdef CONFIG_RTC_HCTOSYS_DEVICE
 118         if (rtc_hctosys_ret == 0 &&
 119             strcmp(dev_name(&to_rtc_device(dev)->dev),
 120                    CONFIG_RTC_HCTOSYS_DEVICE) == 0)
 121                 return sprintf(buf, "1\n");
 122 #endif
 123         return sprintf(buf, "0\n");
 124 }
 125 static DEVICE_ATTR_RO(hctosys);
 126
 127 static ssize_t
 128 wakealarm_show(struct device *dev, struct device_attribute *attr, char *buf)
 129 {
 130         ssize_t retval;
 131         time64_t alarm;
 132         struct rtc_wkalrm alm;
 133
 134         /* Don't show disabled alarms.  For uniformity, RTC alarms are
 135          * conceptually one-shot, even though some common RTCs (on PCs)
 136          * don't actually work that way.
 137          *
 138          * NOTE: RTC implementations where the alarm doesn't match an
 139          * exact YYYY-MM-DD HH:MM[:SS] date *must* disable their RTC
 140          * alarms after they trigger, to ensure one-shot semantics.
 141          */
 142         retval = rtc_read_alarm(to_rtc_device(dev), &alm);
 143         if (retval == 0 && alm.enabled) {
 144                 alarm = rtc_tm_to_time64(&alm.time);
 145                 retval = sprintf(buf, "%lld\n", alarm);
 146         }
 147
 148         return retval;
 149 }
 150
 151 static ssize_t
 152 wakealarm_store(struct device *dev, struct device_attribute *attr,
 153                 const char *buf, size_t n)
 154 {
 155         ssize_t retval;
 156         time64_t now, alarm;
 157         time64_t push = 0;
 158         struct rtc_wkalrm alm;
 159         struct rtc_device *rtc = to_rtc_device(dev);
 160         const char *buf_ptr;
 161         int adjust = 0;
 162
 163         /* Only request alarms that trigger in the future.  Disable them
 164          * by writing another time, e.g. 0 meaning Jan 1 1970 UTC.
 165          */
 166         retval = rtc_read_time(rtc, &alm.time);
 167         if (retval < 0)
 168                 return retval;
 169         now = rtc_tm_to_time64(&alm.time);
 170
 171         buf_ptr = buf;
 172         if (*buf_ptr == '+') {
 173                 buf_ptr++;
 174                 if (*buf_ptr == '=') {
 175                         buf_ptr++;
 176                         push = 1;
 177                 } else {
 178                         adjust = 1;
 179                 }
 180         }
 181         retval = kstrtos64(buf_ptr, 0, &alarm);
 182         if (retval)
 183                 return retval;
 184         if (adjust)
 185                 alarm += now;
 186         if (alarm > now || push) {
 187                 /* Avoid accidentally clobbering active alarms; we can't
 188                  * entirely prevent that here, without even the minimal
 189                  * locking from the /dev/rtcN api.
 190                  */
 191                 retval = rtc_read_alarm(rtc, &alm);
 192                 if (retval < 0)
 193                         return retval;
 194                 if (alm.enabled) {
 195                         if (push) {
 196                                 push = rtc_tm_to_time64(&alm.time);
 197                                 alarm += push;
 198                         } else
 199                                 return -EBUSY;
 200                 } else if (push)
 201                         return -EINVAL;
 202                 alm.enabled = 1;
 203         } else {
 204                 alm.enabled = 0;
 205
 206                 /* Provide a valid future alarm time.  Linux isn't EFI,
 207                  * this time won't be ignored when disabling the alarm.
 208                  */
 209                 alarm = now + 300;
 210         }
 211         rtc_time64_to_tm(alarm, &alm.time);
 212
 213         retval = rtc_set_alarm(rtc, &alm);
 214         return (retval < 0) ? retval : n;
 215 }
 216 static DEVICE_ATTR_RW(wakealarm);
 217
 218 static ssize_t
 219 offset_show(struct device *dev, struct device_attribute *attr, char *buf)
 220 {
 221         ssize_t retval;
 222         long offset;
 223
 224         retval = rtc_read_offset(to_rtc_device(dev), &offset);
 225         if (retval == 0)
 226                 retval = sprintf(buf, "%ld\n", offset);
 227
 228         return retval;
 229 }
 230
 231 static ssize_t
 232 offset_store(struct device *dev, struct device_attribute *attr,
 233              const char *buf, size_t n)
 234 {
 235         ssize_t retval;
 236         long offset;
 237
 238         retval = kstrtol(buf, 10, &offset);
 239         if (retval == 0)
 240                 retval = rtc_set_offset(to_rtc_device(dev), offset);
 241
 242         return (retval < 0) ? retval : n;
 243 }
 244 static DEVICE_ATTR_RW(offset);
 245
 246 static ssize_t
 247 range_show(struct device *dev, struct device_attribute *attr, char *buf)
 248 {
 249         return sprintf(buf, "[%lld,%llu]\n", to_rtc_device(dev)->range_min,
 250                        to_rtc_device(dev)->range_max);
 251 }
 252 static DEVICE_ATTR_RO(range);
 253
 254 static struct attribute *rtc_attrs[] = {
 255         &dev_attr_name.attr,
 256         &dev_attr_date.attr,
 257         &dev_attr_time.attr,
 258         &dev_attr_since_epoch.attr,
 259         &dev_attr_max_user_freq.attr,
 260         &dev_attr_hctosys.attr,
 261         &dev_attr_wakealarm.attr,
 262         &dev_attr_offset.attr,
 263         &dev_attr_range.attr,
 264         NULL,
 265 };
 266
 267 /* The reason to trigger an alarm with no process watching it (via sysfs)
 268  * is its side effect:  waking from a system state like suspend-to-RAM or
 269  * suspend-to-disk.  So: no attribute unless that side effect is possible.
 270  * (Userspace may disable that mechanism later.)
 271  */
 272 static bool rtc_does_wakealarm(struct rtc_device *rtc)
 273 {
 274         if (!device_can_wakeup(rtc->dev.parent))
 275                 return false;
 276
 277         return !!test_bit(RTC_FEATURE_ALARM, rtc->features);
 278 }
 279
 280 static umode_t rtc_attr_is_visible(struct kobject *kobj,
 281                                    struct attribute *attr, int n)
 282 {
 283         struct device *dev = kobj_to_dev(kobj);
 284         struct rtc_device *rtc = to_rtc_device(dev);
 285         umode_t mode = attr->mode;
 286
 287         if (attr == &dev_attr_wakealarm.attr) {
 288                 if (!rtc_does_wakealarm(rtc))
 289                         mode = 0;
 290         } else if (attr == &dev_attr_offset.attr) {
 291                 if (!rtc->ops->set_offset)
 292                         mode = 0;
 293         } else if (attr == &dev_attr_range.attr) {
 294                 if (!(rtc->range_max - rtc->range_min))
 295                         mode = 0;
 296         }
 297
 298         return mode;
 299 }
 300
 301 static struct attribute_group rtc_attr_group = {
 302         .is_visible     = rtc_attr_is_visible,
 303         .attrs          = rtc_attrs,
 304 };
 305
 306 static const struct attribute_group *rtc_attr_groups[] = {
 307         &rtc_attr_group,
 308         NULL
 309 };
 310
 311 const struct attribute_group **rtc_get_dev_attribute_groups(void)
 312 {
 313         return rtc_attr_groups;
 314 }
 315
 316 int rtc_add_groups(struct rtc_device *rtc, const struct attribute_group **grps)
 317 {
 318         size_t old_cnt = 0, add_cnt = 0, new_cnt;
 319         const struct attribute_group **groups, **old;
 320
 321         if (!grps)
 322                 return -EINVAL;
 323
 324         groups = rtc->dev.groups;
 325         if (groups)
 326                 for (; *groups; groups++)
 327                         old_cnt++;
 328
 329         for (groups = grps; *groups; groups++)
 330                 add_cnt++;
 331
 332         new_cnt = old_cnt + add_cnt + 1;
 333         groups = devm_kcalloc(&rtc->dev, new_cnt, sizeof(*groups), GFP_KERNEL);
 334         if (!groups)
 335                 return -ENOMEM;
 336         memcpy(groups, rtc->dev.groups, old_cnt * sizeof(*groups));
 337         memcpy(groups + old_cnt, grps, add_cnt * sizeof(*groups));
 338         groups[old_cnt + add_cnt] = NULL;
 339
 340         old = rtc->dev.groups;
 341         rtc->dev.groups = groups;
 342         if (old && old != rtc_attr_groups)
 343                 devm_kfree(&rtc->dev, old);
 344
 345         return 0;
 346 }
 347 EXPORT_SYMBOL(rtc_add_groups);
 348
 349 int rtc_add_group(struct rtc_device *rtc, const struct attribute_group *grp)
 350 {
 351         const struct attribute_group *groups[] = { grp, NULL };
 352
 353         return rtc_add_groups(rtc, groups);
 354 }
 355 EXPORT_SYMBOL(rtc_add_group);