linux/drivers/rtc/sysfs.c
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   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
  23static ssize_t
  24name_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}
  29static DEVICE_ATTR_RO(name);
  30
  31static ssize_t
  32date_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}
  43static DEVICE_ATTR_RO(date);
  44
  45static ssize_t
  46time_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}
  57static DEVICE_ATTR_RO(time);
  58
  59static ssize_t
  60since_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}
  75static DEVICE_ATTR_RO(since_epoch);
  76
  77static ssize_t
  78max_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
  83static ssize_t
  84max_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}
 102static DEVICE_ATTR_RW(max_user_freq);
 103
 104/**
 105 * hctosys_show - 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 */
 113static ssize_t
 114hctosys_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}
 124static DEVICE_ATTR_RO(hctosys);
 125
 126static ssize_t
 127wakealarm_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
 150static ssize_t
 151wakealarm_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}
 215static DEVICE_ATTR_RW(wakealarm);
 216
 217static ssize_t
 218offset_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
 230static ssize_t
 231offset_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}
 243static DEVICE_ATTR_RW(offset);
 244
 245static ssize_t
 246range_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}
 251static DEVICE_ATTR_RO(range);
 252
 253static 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 */
 271static bool rtc_does_wakealarm(struct rtc_device *rtc)
 272{
 273        if (!device_can_wakeup(rtc->dev.parent))
 274                return false;
 275
 276        return !!test_bit(RTC_FEATURE_ALARM, rtc->features);
 277}
 278
 279static 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
 300static struct attribute_group rtc_attr_group = {
 301        .is_visible     = rtc_attr_is_visible,
 302        .attrs          = rtc_attrs,
 303};
 304
 305static const struct attribute_group *rtc_attr_groups[] = {
 306        &rtc_attr_group,
 307        NULL
 308};
 309
 310const struct attribute_group **rtc_get_dev_attribute_groups(void)
 311{
 312        return rtc_attr_groups;
 313}
 314
 315int 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 (!grps)
 321                return -EINVAL;
 322
 323        groups = rtc->dev.groups;
 324        if (groups)
 325                for (; *groups; groups++)
 326                        old_cnt++;
 327
 328        for (groups = grps; *groups; groups++)
 329                add_cnt++;
 330
 331        new_cnt = old_cnt + add_cnt + 1;
 332        groups = devm_kcalloc(&rtc->dev, new_cnt, sizeof(*groups), GFP_KERNEL);
 333        if (!groups)
 334                return -ENOMEM;
 335        memcpy(groups, rtc->dev.groups, old_cnt * sizeof(*groups));
 336        memcpy(groups + old_cnt, grps, add_cnt * sizeof(*groups));
 337        groups[old_cnt + add_cnt] = NULL;
 338
 339        old = rtc->dev.groups;
 340        rtc->dev.groups = groups;
 341        if (old && old != rtc_attr_groups)
 342                devm_kfree(&rtc->dev, old);
 343
 344        return 0;
 345}
 346EXPORT_SYMBOL(rtc_add_groups);
 347
 348int rtc_add_group(struct rtc_device *rtc, const struct attribute_group *grp)
 349{
 350        const struct attribute_group *groups[] = { grp, NULL };
 351
 352        return rtc_add_groups(rtc, groups);
 353}
 354EXPORT_SYMBOL(rtc_add_group);
 355