linux/drivers/rtc/rtc-sysfs.c
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   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
  27static ssize_t
  28rtc_sysfs_show_name(struct device *dev, struct device_attribute *attr,
  29                char *buf)
  30{
  31        return sprintf(buf, "%s\n", to_rtc_device(dev)->name);
  32}
  33
  34static ssize_t
  35rtc_sysfs_show_date(struct device *dev, struct device_attribute *attr,
  36                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
  50static ssize_t
  51rtc_sysfs_show_time(struct device *dev, struct device_attribute *attr,
  52                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
  66static ssize_t
  67rtc_sysfs_show_since_epoch(struct device *dev, struct device_attribute *attr,
  68                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                unsigned long time;
  76                rtc_tm_to_time(&tm, &time);
  77                retval = sprintf(buf, "%lu\n", time);
  78        }
  79
  80        return retval;
  81}
  82
  83static ssize_t
  84rtc_sysfs_show_max_user_freq(struct device *dev, struct device_attribute *attr,
  85                char *buf)
  86{
  87        return sprintf(buf, "%d\n", to_rtc_device(dev)->max_user_freq);
  88}
  89
  90static ssize_t
  91rtc_sysfs_set_max_user_freq(struct device *dev, struct device_attribute *attr,
  92                const char *buf, size_t n)
  93{
  94        struct rtc_device *rtc = to_rtc_device(dev);
  95        unsigned long val = simple_strtoul(buf, NULL, 0);
  96
  97        if (val >= 4096 || val == 0)
  98                return -EINVAL;
  99
 100        rtc->max_user_freq = (int)val;
 101
 102        return n;
 103}
 104
 105static ssize_t
 106rtc_sysfs_show_hctosys(struct device *dev, struct device_attribute *attr,
 107                char *buf)
 108{
 109#ifdef CONFIG_RTC_HCTOSYS_DEVICE
 110        if (rtc_hctosys_ret == 0 &&
 111                        strcmp(dev_name(&to_rtc_device(dev)->dev),
 112                                CONFIG_RTC_HCTOSYS_DEVICE) == 0)
 113                return sprintf(buf, "1\n");
 114        else
 115#endif
 116                return sprintf(buf, "0\n");
 117}
 118
 119static struct device_attribute rtc_attrs[] = {
 120        __ATTR(name, S_IRUGO, rtc_sysfs_show_name, NULL),
 121        __ATTR(date, S_IRUGO, rtc_sysfs_show_date, NULL),
 122        __ATTR(time, S_IRUGO, rtc_sysfs_show_time, NULL),
 123        __ATTR(since_epoch, S_IRUGO, rtc_sysfs_show_since_epoch, NULL),
 124        __ATTR(max_user_freq, S_IRUGO | S_IWUSR, rtc_sysfs_show_max_user_freq,
 125                        rtc_sysfs_set_max_user_freq),
 126        __ATTR(hctosys, S_IRUGO, rtc_sysfs_show_hctosys, NULL),
 127        { },
 128};
 129
 130static ssize_t
 131rtc_sysfs_show_wakealarm(struct device *dev, struct device_attribute *attr,
 132                char *buf)
 133{
 134        ssize_t retval;
 135        unsigned long alarm;
 136        struct rtc_wkalrm alm;
 137
 138        /* Don't show disabled alarms.  For uniformity, RTC alarms are
 139         * conceptually one-shot, even though some common RTCs (on PCs)
 140         * don't actually work that way.
 141         *
 142         * NOTE: RTC implementations where the alarm doesn't match an
 143         * exact YYYY-MM-DD HH:MM[:SS] date *must* disable their RTC
 144         * alarms after they trigger, to ensure one-shot semantics.
 145         */
 146        retval = rtc_read_alarm(to_rtc_device(dev), &alm);
 147        if (retval == 0 && alm.enabled) {
 148                rtc_tm_to_time(&alm.time, &alarm);
 149                retval = sprintf(buf, "%lu\n", alarm);
 150        }
 151
 152        return retval;
 153}
 154
 155static ssize_t
 156rtc_sysfs_set_wakealarm(struct device *dev, struct device_attribute *attr,
 157                const char *buf, size_t n)
 158{
 159        ssize_t retval;
 160        unsigned long now, alarm;
 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                adjust = 1;
 178        }
 179        alarm = simple_strtoul(buf_ptr, NULL, 0);
 180        if (adjust) {
 181                alarm += now;
 182        }
 183        if (alarm > now) {
 184                /* Avoid accidentally clobbering active alarms; we can't
 185                 * entirely prevent that here, without even the minimal
 186                 * locking from the /dev/rtcN api.
 187                 */
 188                retval = rtc_read_alarm(rtc, &alm);
 189                if (retval < 0)
 190                        return retval;
 191                if (alm.enabled)
 192                        return -EBUSY;
 193
 194                alm.enabled = 1;
 195        } else {
 196                alm.enabled = 0;
 197
 198                /* Provide a valid future alarm time.  Linux isn't EFI,
 199                 * this time won't be ignored when disabling the alarm.
 200                 */
 201                alarm = now + 300;
 202        }
 203        rtc_time_to_tm(alarm, &alm.time);
 204
 205        retval = rtc_set_alarm(rtc, &alm);
 206        return (retval < 0) ? retval : n;
 207}
 208static DEVICE_ATTR(wakealarm, S_IRUGO | S_IWUSR,
 209                rtc_sysfs_show_wakealarm, rtc_sysfs_set_wakealarm);
 210
 211
 212/* The reason to trigger an alarm with no process watching it (via sysfs)
 213 * is its side effect:  waking from a system state like suspend-to-RAM or
 214 * suspend-to-disk.  So: no attribute unless that side effect is possible.
 215 * (Userspace may disable that mechanism later.)
 216 */
 217static inline int rtc_does_wakealarm(struct rtc_device *rtc)
 218{
 219        if (!device_can_wakeup(rtc->dev.parent))
 220                return 0;
 221        return rtc->ops->set_alarm != NULL;
 222}
 223
 224
 225void rtc_sysfs_add_device(struct rtc_device *rtc)
 226{
 227        int err;
 228
 229        /* not all RTCs support both alarms and wakeup */
 230        if (!rtc_does_wakealarm(rtc))
 231                return;
 232
 233        err = device_create_file(&rtc->dev, &dev_attr_wakealarm);
 234        if (err)
 235                dev_err(rtc->dev.parent,
 236                        "failed to create alarm attribute, %d\n", err);
 237}
 238
 239void rtc_sysfs_del_device(struct rtc_device *rtc)
 240{
 241        /* REVISIT did we add it successfully? */
 242        if (rtc_does_wakealarm(rtc))
 243                device_remove_file(&rtc->dev, &dev_attr_wakealarm);
 244}
 245
 246void __init rtc_sysfs_init(struct class *rtc_class)
 247{
 248        rtc_class->dev_attrs = rtc_attrs;
 249}
 250
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