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 /* device attributes */
  16
  17 static ssize_t rtc_sysfs_show_name(struct class_device *dev, char *buf)
  18 {
  19         return sprintf(buf, "%s\n", to_rtc_device(dev)->name);
  20 }
  21 static CLASS_DEVICE_ATTR(name, S_IRUGO, rtc_sysfs_show_name, NULL);
  22
  23 static ssize_t rtc_sysfs_show_date(struct class_device *dev, char *buf)
  24 {
  25         ssize_t retval;
  26         struct rtc_time tm;
  27
  28         retval = rtc_read_time(dev, &tm);
  29         if (retval == 0) {
  30                 retval = sprintf(buf, "%04d-%02d-%02d\n",
  31                         tm.tm_year + 1900, tm.tm_mon + 1, tm.tm_mday);
  32         }
  33
  34         return retval;
  35 }
  36 static CLASS_DEVICE_ATTR(date, S_IRUGO, rtc_sysfs_show_date, NULL);
  37
  38 static ssize_t rtc_sysfs_show_time(struct class_device *dev, char *buf)
  39 {
  40         ssize_t retval;
  41         struct rtc_time tm;
  42
  43         retval = rtc_read_time(dev, &tm);
  44         if (retval == 0) {
  45                 retval = sprintf(buf, "%02d:%02d:%02d\n",
  46                         tm.tm_hour, tm.tm_min, tm.tm_sec);
  47         }
  48
  49         return retval;
  50 }
  51 static CLASS_DEVICE_ATTR(time, S_IRUGO, rtc_sysfs_show_time, NULL);
  52
  53 static ssize_t rtc_sysfs_show_since_epoch(struct class_device *dev, char *buf)
  54 {
  55         ssize_t retval;
  56         struct rtc_time tm;
  57
  58         retval = rtc_read_time(dev, &tm);
  59         if (retval == 0) {
  60                 unsigned long time;
  61                 rtc_tm_to_time(&tm, &time);
  62                 retval = sprintf(buf, "%lu\n", time);
  63         }
  64
  65         return retval;
  66 }
  67 static CLASS_DEVICE_ATTR(since_epoch, S_IRUGO, rtc_sysfs_show_since_epoch, NULL);
  68
  69 static struct attribute *rtc_attrs[] = {
  70         &class_device_attr_name.attr,
  71         &class_device_attr_date.attr,
  72         &class_device_attr_time.attr,
  73         &class_device_attr_since_epoch.attr,
  74         NULL,
  75 };
  76
  77 static struct attribute_group rtc_attr_group = {
  78         .attrs = rtc_attrs,
  79 };
  80
  81
  82 static ssize_t
  83 rtc_sysfs_show_wakealarm(struct class_device *dev, char *buf)
  84 {
  85         ssize_t retval;
  86         unsigned long alarm;
  87         struct rtc_wkalrm alm;
  88
  89         /* Don't show disabled alarms; but the RTC could leave the
  90          * alarm enabled after it's already triggered.  Alarms are
  91          * conceptually one-shot, even though some common hardware
  92          * (PCs) doesn't actually work that way.
  93          *
  94          * REVISIT maybe we should require RTC implementations to
  95          * disable the RTC alarm after it triggers, for uniformity.
  96          */
  97         retval = rtc_read_alarm(dev, &alm);
  98         if (retval == 0 && alm.enabled) {
  99                 rtc_tm_to_time(&alm.time, &alarm);
 100                 retval = sprintf(buf, "%lu\n", alarm);
 101         }
 102
 103         return retval;
 104 }
 105
 106 static ssize_t
 107 rtc_sysfs_set_wakealarm(struct class_device *dev, const char *buf, size_t n)
 108 {
 109         ssize_t retval;
 110         unsigned long now, alarm;
 111         struct rtc_wkalrm alm;
 112
 113         /* Only request alarms that trigger in the future.  Disable them
 114          * by writing another time, e.g. 0 meaning Jan 1 1970 UTC.
 115          */
 116         retval = rtc_read_time(dev, &alm.time);
 117         if (retval < 0)
 118                 return retval;
 119         rtc_tm_to_time(&alm.time, &now);
 120
 121         alarm = simple_strtoul(buf, NULL, 0);
 122         if (alarm > now) {
 123                 /* Avoid accidentally clobbering active alarms; we can't
 124                  * entirely prevent that here, without even the minimal
 125                  * locking from the /dev/rtcN api.
 126                  */
 127                 retval = rtc_read_alarm(dev, &alm);
 128                 if (retval < 0)
 129                         return retval;
 130                 if (alm.enabled)
 131                         return -EBUSY;
 132
 133                 alm.enabled = 1;
 134         } else {
 135                 alm.enabled = 0;
 136
 137                 /* Provide a valid future alarm time.  Linux isn't EFI,
 138                  * this time won't be ignored when disabling the alarm.
 139                  */
 140                 alarm = now + 300;
 141         }
 142         rtc_time_to_tm(alarm, &alm.time);
 143
 144         retval = rtc_set_alarm(dev, &alm);
 145         return (retval < 0) ? retval : n;
 146 }
 147 static const CLASS_DEVICE_ATTR(wakealarm, S_IRUGO | S_IWUSR,
 148                 rtc_sysfs_show_wakealarm, rtc_sysfs_set_wakealarm);
 149
 150
 151 /* The reason to trigger an alarm with no process watching it (via sysfs)
 152  * is its side effect:  waking from a system state like suspend-to-RAM or
 153  * suspend-to-disk.  So: no attribute unless that side effect is possible.
 154  * (Userspace may disable that mechanism later.)
 155  */
 156 static inline int rtc_does_wakealarm(struct class_device *class_dev)
 157 {
 158         struct rtc_device *rtc;
 159
 160         if (!device_can_wakeup(class_dev->dev))
 161                 return 0;
 162         rtc = to_rtc_device(class_dev);
 163         return rtc->ops->set_alarm != NULL;
 164 }
 165
 166
 167 static int rtc_sysfs_add_device(struct class_device *class_dev,
 168                                         struct class_interface *class_intf)
 169 {
 170         int err;
 171
 172         dev_dbg(class_dev->dev, "rtc intf: sysfs\n");
 173
 174         err = sysfs_create_group(&class_dev->kobj, &rtc_attr_group);
 175         if (err)
 176                 dev_err(class_dev->dev, "failed to create %s\n",
 177                                 "sysfs attributes");
 178         else if (rtc_does_wakealarm(class_dev)) {
 179                 /* not all RTCs support both alarms and wakeup */
 180                 err = class_device_create_file(class_dev,
 181                                         &class_device_attr_wakealarm);
 182                 if (err) {
 183                         dev_err(class_dev->dev, "failed to create %s\n",
 184                                         "alarm attribute");
 185                         sysfs_remove_group(&class_dev->kobj, &rtc_attr_group);
 186                 }
 187         }
 188
 189         return err;
 190 }
 191
 192 static void rtc_sysfs_remove_device(struct class_device *class_dev,
 193                                 struct class_interface *class_intf)
 194 {
 195         if (rtc_does_wakealarm(class_dev))
 196                 class_device_remove_file(class_dev,
 197                                 &class_device_attr_wakealarm);
 198         sysfs_remove_group(&class_dev->kobj, &rtc_attr_group);
 199 }
 200
 201 /* interface registration */
 202
 203 static struct class_interface rtc_sysfs_interface = {
 204         .add = &rtc_sysfs_add_device,
 205         .remove = &rtc_sysfs_remove_device,
 206 };
 207
 208 static int __init rtc_sysfs_init(void)
 209 {
 210         return rtc_interface_register(&rtc_sysfs_interface);
 211 }
 212
 213 static void __exit rtc_sysfs_exit(void)
 214 {
 215         class_interface_unregister(&rtc_sysfs_interface);
 216 }
 217
 218 subsys_initcall(rtc_sysfs_init);
 219 module_exit(rtc_sysfs_exit);
 220
 221 MODULE_AUTHOR("Alessandro Zummo <a.zummo@towertech.it>");
 222 MODULE_DESCRIPTION("RTC class sysfs interface");
 223 MODULE_LICENSE("GPL");