drivers/rtc/interface.c

   1 /*
   2  * RTC subsystem, interface functions
   3  *
   4  * Copyright (C) 2005 Tower Technologies
   5  * Author: Alessandro Zummo <a.zummo@towertech.it>
   6  *
   7  * based on arch/arm/common/rtctime.c
   8  *
   9  * This program is free software; you can redistribute it and/or modify
  10  * it under the terms of the GNU General Public License version 2 as
  11  * published by the Free Software Foundation.
  12 */
  13
  14 #include <linux/rtc.h>
  15 #include <linux/log2.h>
  16
  17 int rtc_read_time(struct rtc_device *rtc, struct rtc_time *tm)
  18 {
  19         int err;
  20
  21         err = mutex_lock_interruptible(&rtc->ops_lock);
  22         if (err)
  23                 return -EBUSY;
  24
  25         if (!rtc->ops)
  26                 err = -ENODEV;
  27         else if (!rtc->ops->read_time)
  28                 err = -EINVAL;
  29         else {
  30                 memset(tm, 0, sizeof(struct rtc_time));
  31                 err = rtc->ops->read_time(rtc->dev.parent, tm);
  32         }
  33
  34         mutex_unlock(&rtc->ops_lock);
  35         return err;
  36 }
  37 EXPORT_SYMBOL_GPL(rtc_read_time);
  38
  39 int rtc_set_time(struct rtc_device *rtc, struct rtc_time *tm)
  40 {
  41         int err;
  42
  43         err = rtc_valid_tm(tm);
  44         if (err != 0)
  45                 return err;
  46
  47         err = mutex_lock_interruptible(&rtc->ops_lock);
  48         if (err)
  49                 return -EBUSY;
  50
  51         if (!rtc->ops)
  52                 err = -ENODEV;
  53         else if (!rtc->ops->set_time)
  54                 err = -EINVAL;
  55         else
  56                 err = rtc->ops->set_time(rtc->dev.parent, tm);
  57
  58         mutex_unlock(&rtc->ops_lock);
  59         return err;
  60 }
  61 EXPORT_SYMBOL_GPL(rtc_set_time);
  62
  63 int rtc_set_mmss(struct rtc_device *rtc, unsigned long secs)
  64 {
  65         int err;
  66
  67         err = mutex_lock_interruptible(&rtc->ops_lock);
  68         if (err)
  69                 return -EBUSY;
  70
  71         if (!rtc->ops)
  72                 err = -ENODEV;
  73         else if (rtc->ops->set_mmss)
  74                 err = rtc->ops->set_mmss(rtc->dev.parent, secs);
  75         else if (rtc->ops->read_time && rtc->ops->set_time) {
  76                 struct rtc_time new, old;
  77
  78                 err = rtc->ops->read_time(rtc->dev.parent, &old);
  79                 if (err == 0) {
  80                         rtc_time_to_tm(secs, &new);
  81
  82                         /*
  83                          * avoid writing when we're going to change the day of
  84                          * the month. We will retry in the next minute. This
  85                          * basically means that if the RTC must not drift
  86                          * by more than 1 minute in 11 minutes.
  87                          */
  88                         if (!((old.tm_hour == 23 && old.tm_min == 59) ||
  89                                 (new.tm_hour == 23 && new.tm_min == 59)))
  90                                 err = rtc->ops->set_time(rtc->dev.parent,
  91                                                 &new);
  92                 }
  93         }
  94         else
  95                 err = -EINVAL;
  96
  97         mutex_unlock(&rtc->ops_lock);
  98
  99         return err;
 100 }
 101 EXPORT_SYMBOL_GPL(rtc_set_mmss);
 102
 103 static int rtc_read_alarm_internal(struct rtc_device *rtc, struct rtc_wkalrm *alarm)
 104 {
 105         int err;
 106
 107         err = mutex_lock_interruptible(&rtc->ops_lock);
 108         if (err)
 109                 return -EBUSY;
 110
 111         if (rtc->ops == NULL)
 112                 err = -ENODEV;
 113         else if (!rtc->ops->read_alarm)
 114                 err = -EINVAL;
 115         else {
 116                 memset(alarm, 0, sizeof(struct rtc_wkalrm));
 117                 err = rtc->ops->read_alarm(rtc->dev.parent, alarm);
 118         }
 119
 120         mutex_unlock(&rtc->ops_lock);
 121         return err;
 122 }
 123
 124 int rtc_read_alarm(struct rtc_device *rtc, struct rtc_wkalrm *alarm)
 125 {
 126         int err;
 127         struct rtc_time before, now;
 128         int first_time = 1;
 129         unsigned long t_now, t_alm;
 130         enum { none, day, month, year } missing = none;
 131         unsigned days;
 132
 133         /* The lower level RTC driver may return -1 in some fields,
 134          * creating invalid alarm->time values, for reasons like:
 135          *
 136          *   - The hardware may not be capable of filling them in;
 137          *     many alarms match only on time-of-day fields, not
 138          *     day/month/year calendar data.
 139          *
 140          *   - Some hardware uses illegal values as "wildcard" match
 141          *     values, which non-Linux firmware (like a BIOS) may try
 142          *     to set up as e.g. "alarm 15 minutes after each hour".
 143          *     Linux uses only oneshot alarms.
 144          *
 145          * When we see that here, we deal with it by using values from
 146          * a current RTC timestamp for any missing (-1) values.  The
 147          * RTC driver prevents "periodic alarm" modes.
 148          *
 149          * But this can be racey, because some fields of the RTC timestamp
 150          * may have wrapped in the interval since we read the RTC alarm,
 151          * which would lead to us inserting inconsistent values in place
 152          * of the -1 fields.
 153          *
 154          * Reading the alarm and timestamp in the reverse sequence
 155          * would have the same race condition, and not solve the issue.
 156          *
 157          * So, we must first read the RTC timestamp,
 158          * then read the RTC alarm value,
 159          * and then read a second RTC timestamp.
 160          *
 161          * If any fields of the second timestamp have changed
 162          * when compared with the first timestamp, then we know
 163          * our timestamp may be inconsistent with that used by
 164          * the low-level rtc_read_alarm_internal() function.
 165          *
 166          * So, when the two timestamps disagree, we just loop and do
 167          * the process again to get a fully consistent set of values.
 168          *
 169          * This could all instead be done in the lower level driver,
 170          * but since more than one lower level RTC implementation needs it,
 171          * then it's probably best best to do it here instead of there..
 172          */
 173
 174         /* Get the "before" timestamp */
 175         err = rtc_read_time(rtc, &before);
 176         if (err < 0)
 177                 return err;
 178         do {
 179                 if (!first_time)
 180                         memcpy(&before, &now, sizeof(struct rtc_time));
 181                 first_time = 0;
 182
 183                 /* get the RTC alarm values, which may be incomplete */
 184                 err = rtc_read_alarm_internal(rtc, alarm);
 185                 if (err)
 186                         return err;
 187                 if (!alarm->enabled)
 188                         return 0;
 189
 190                 /* full-function RTCs won't have such missing fields */
 191                 if (rtc_valid_tm(&alarm->time) == 0)
 192                         return 0;
 193
 194                 /* get the "after" timestamp, to detect wrapped fields */
 195                 err = rtc_read_time(rtc, &now);
 196                 if (err < 0)
 197                         return err;
 198
 199                 /* note that tm_sec is a "don't care" value here: */
 200         } while (   before.tm_min   != now.tm_min
 201                  || before.tm_hour  != now.tm_hour
 202                  || before.tm_mon   != now.tm_mon
 203                  || before.tm_year  != now.tm_year);
 204
 205         /* Fill in the missing alarm fields using the timestamp; we
 206          * know there's at least one since alarm->time is invalid.
 207          */
 208         if (alarm->time.tm_sec == -1)
 209                 alarm->time.tm_sec = now.tm_sec;
 210         if (alarm->time.tm_min == -1)
 211                 alarm->time.tm_min = now.tm_min;
 212         if (alarm->time.tm_hour == -1)
 213                 alarm->time.tm_hour = now.tm_hour;
 214
 215         /* For simplicity, only support date rollover for now */
 216         if (alarm->time.tm_mday == -1) {
 217                 alarm->time.tm_mday = now.tm_mday;
 218                 missing = day;
 219         }
 220         if (alarm->time.tm_mon == -1) {
 221                 alarm->time.tm_mon = now.tm_mon;
 222                 if (missing == none)
 223                         missing = month;
 224         }
 225         if (alarm->time.tm_year == -1) {
 226                 alarm->time.tm_year = now.tm_year;
 227                 if (missing == none)
 228                         missing = year;
 229         }
 230
 231         /* with luck, no rollover is needed */
 232         rtc_tm_to_time(&now, &t_now);
 233         rtc_tm_to_time(&alarm->time, &t_alm);
 234         if (t_now < t_alm)
 235                 goto done;
 236
 237         switch (missing) {
 238
 239         /* 24 hour rollover ... if it's now 10am Monday, an alarm that
 240          * that will trigger at 5am will do so at 5am Tuesday, which
 241          * could also be in the next month or year.  This is a common
 242          * case, especially for PCs.
 243          */
 244         case day:
 245                 dev_dbg(&rtc->dev, "alarm rollover: %s\n", "day");
 246                 t_alm += 24 * 60 * 60;
 247                 rtc_time_to_tm(t_alm, &alarm->time);
 248                 break;
 249
 250         /* Month rollover ... if it's the 31th, an alarm on the 3rd will
 251          * be next month.  An alarm matching on the 30th, 29th, or 28th
 252          * may end up in the month after that!  Many newer PCs support
 253          * this type of alarm.
 254          */
 255         case month:
 256                 dev_dbg(&rtc->dev, "alarm rollover: %s\n", "month");
 257                 do {
 258                         if (alarm->time.tm_mon < 11)
 259                                 alarm->time.tm_mon++;
 260                         else {
 261                                 alarm->time.tm_mon = 0;
 262                                 alarm->time.tm_year++;
 263                         }
 264                         days = rtc_month_days(alarm->time.tm_mon,
 265                                         alarm->time.tm_year);
 266                 } while (days < alarm->time.tm_mday);
 267                 break;
 268
 269         /* Year rollover ... easy except for leap years! */
 270         case year:
 271                 dev_dbg(&rtc->dev, "alarm rollover: %s\n", "year");
 272                 do {
 273                         alarm->time.tm_year++;
 274                 } while (!rtc_valid_tm(&alarm->time));
 275                 break;
 276
 277         default:
 278                 dev_warn(&rtc->dev, "alarm rollover not handled\n");
 279         }
 280
 281 done:
 282         return 0;
 283 }
 284 EXPORT_SYMBOL_GPL(rtc_read_alarm);
 285
 286 int rtc_set_alarm(struct rtc_device *rtc, struct rtc_wkalrm *alarm)
 287 {
 288         int err;
 289
 290         err = rtc_valid_tm(&alarm->time);
 291         if (err != 0)
 292                 return err;
 293
 294         err = mutex_lock_interruptible(&rtc->ops_lock);
 295         if (err)
 296                 return -EBUSY;
 297
 298         if (!rtc->ops)
 299                 err = -ENODEV;
 300         else if (!rtc->ops->set_alarm)
 301                 err = -EINVAL;
 302         else
 303                 err = rtc->ops->set_alarm(rtc->dev.parent, alarm);
 304
 305         mutex_unlock(&rtc->ops_lock);
 306         return err;
 307 }
 308 EXPORT_SYMBOL_GPL(rtc_set_alarm);
 309
 310 /**
 311  * rtc_update_irq - report RTC periodic, alarm, and/or update irqs
 312  * @rtc: the rtc device
 313  * @num: how many irqs are being reported (usually one)
 314  * @events: mask of RTC_IRQF with one or more of RTC_PF, RTC_AF, RTC_UF
 315  * Context: in_interrupt(), irqs blocked
 316  */
 317 void rtc_update_irq(struct rtc_device *rtc,
 318                 unsigned long num, unsigned long events)
 319 {
 320         spin_lock(&rtc->irq_lock);
 321         rtc->irq_data = (rtc->irq_data + (num << 8)) | events;
 322         spin_unlock(&rtc->irq_lock);
 323
 324         spin_lock(&rtc->irq_task_lock);
 325         if (rtc->irq_task)
 326                 rtc->irq_task->func(rtc->irq_task->private_data);
 327         spin_unlock(&rtc->irq_task_lock);
 328
 329         wake_up_interruptible(&rtc->irq_queue);
 330         kill_fasync(&rtc->async_queue, SIGIO, POLL_IN);
 331 }
 332 EXPORT_SYMBOL_GPL(rtc_update_irq);
 333
 334 static int __rtc_match(struct device *dev, void *data)
 335 {
 336         char *name = (char *)data;
 337
 338         if (strncmp(dev->bus_id, name, BUS_ID_SIZE) == 0)
 339                 return 1;
 340         return 0;
 341 }
 342
 343 struct rtc_device *rtc_class_open(char *name)
 344 {
 345         struct device *dev;
 346         struct rtc_device *rtc = NULL;
 347
 348         dev = class_find_device(rtc_class, name, __rtc_match);
 349         if (dev)
 350                 rtc = to_rtc_device(dev);
 351
 352         if (rtc) {
 353                 if (!try_module_get(rtc->owner)) {
 354                         put_device(dev);
 355                         rtc = NULL;
 356                 }
 357         }
 358
 359         return rtc;
 360 }
 361 EXPORT_SYMBOL_GPL(rtc_class_open);
 362
 363 void rtc_class_close(struct rtc_device *rtc)
 364 {
 365         module_put(rtc->owner);
 366         put_device(&rtc->dev);
 367 }
 368 EXPORT_SYMBOL_GPL(rtc_class_close);
 369
 370 int rtc_irq_register(struct rtc_device *rtc, struct rtc_task *task)
 371 {
 372         int retval = -EBUSY;
 373
 374         if (task == NULL || task->func == NULL)
 375                 return -EINVAL;
 376
 377         /* Cannot register while the char dev is in use */
 378         if (test_and_set_bit_lock(RTC_DEV_BUSY, &rtc->flags))
 379                 return -EBUSY;
 380
 381         spin_lock_irq(&rtc->irq_task_lock);
 382         if (rtc->irq_task == NULL) {
 383                 rtc->irq_task = task;
 384                 retval = 0;
 385         }
 386         spin_unlock_irq(&rtc->irq_task_lock);
 387
 388         clear_bit_unlock(RTC_DEV_BUSY, &rtc->flags);
 389
 390         return retval;
 391 }
 392 EXPORT_SYMBOL_GPL(rtc_irq_register);
 393
 394 void rtc_irq_unregister(struct rtc_device *rtc, struct rtc_task *task)
 395 {
 396         spin_lock_irq(&rtc->irq_task_lock);
 397         if (rtc->irq_task == task)
 398                 rtc->irq_task = NULL;
 399         spin_unlock_irq(&rtc->irq_task_lock);
 400 }
 401 EXPORT_SYMBOL_GPL(rtc_irq_unregister);
 402
 403 /**
 404  * rtc_irq_set_state - enable/disable 2^N Hz periodic IRQs
 405  * @rtc: the rtc device
 406  * @task: currently registered with rtc_irq_register()
 407  * @enabled: true to enable periodic IRQs
 408  * Context: any
 409  *
 410  * Note that rtc_irq_set_freq() should previously have been used to
 411  * specify the desired frequency of periodic IRQ task->func() callbacks.
 412  */
 413 int rtc_irq_set_state(struct rtc_device *rtc, struct rtc_task *task, int enabled)
 414 {
 415         int err = 0;
 416         unsigned long flags;
 417
 418         if (rtc->ops->irq_set_state == NULL)
 419                 return -ENXIO;
 420
 421         spin_lock_irqsave(&rtc->irq_task_lock, flags);
 422         if (rtc->irq_task != NULL && task == NULL)
 423                 err = -EBUSY;
 424         if (rtc->irq_task != task)
 425                 err = -EACCES;
 426         spin_unlock_irqrestore(&rtc->irq_task_lock, flags);
 427
 428         if (err == 0)
 429                 err = rtc->ops->irq_set_state(rtc->dev.parent, enabled);
 430
 431         return err;
 432 }
 433 EXPORT_SYMBOL_GPL(rtc_irq_set_state);
 434
 435 /**
 436  * rtc_irq_set_freq - set 2^N Hz periodic IRQ frequency for IRQ
 437  * @rtc: the rtc device
 438  * @task: currently registered with rtc_irq_register()
 439  * @freq: positive frequency with which task->func() will be called
 440  * Context: any
 441  *
 442  * Note that rtc_irq_set_state() is used to enable or disable the
 443  * periodic IRQs.
 444  */
 445 int rtc_irq_set_freq(struct rtc_device *rtc, struct rtc_task *task, int freq)
 446 {
 447         int err = 0;
 448         unsigned long flags;
 449
 450         if (rtc->ops->irq_set_freq == NULL)
 451                 return -ENXIO;
 452
 453         if (!is_power_of_2(freq))
 454                 return -EINVAL;
 455
 456         spin_lock_irqsave(&rtc->irq_task_lock, flags);
 457         if (rtc->irq_task != NULL && task == NULL)
 458                 err = -EBUSY;
 459         if (rtc->irq_task != task)
 460                 err = -EACCES;
 461         spin_unlock_irqrestore(&rtc->irq_task_lock, flags);
 462
 463         if (err == 0) {
 464                 err = rtc->ops->irq_set_freq(rtc->dev.parent, freq);
 465                 if (err == 0)
 466                         rtc->irq_freq = freq;
 467         }
 468         return err;
 469 }
 470 EXPORT_SYMBOL_GPL(rtc_irq_set_freq);