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
 130         /* The lower level RTC driver may not be capable of filling
 131          * in all fields of the rtc_time struct (eg. rtc-cmos),
 132          * and so might instead return -1 in some fields.
 133          * We deal with that here by grabbing a current RTC timestamp
 134          * and using values from that for any missing (-1) values.
 135          *
 136          * But this can be racey, because some fields of the RTC timestamp
 137          * may have wrapped in the interval since we read the RTC alarm,
 138          * which would lead to us inserting inconsistent values in place
 139          * of the -1 fields.
 140          *
 141          * Reading the alarm and timestamp in the reverse sequence
 142          * would have the same race condition, and not solve the issue.
 143          *
 144          * So, we must first read the RTC timestamp,
 145          * then read the RTC alarm value,
 146          * and then read a second RTC timestamp.
 147          *
 148          * If any fields of the second timestamp have changed
 149          * when compared with the first timestamp, then we know
 150          * our timestamp may be inconsistent with that used by
 151          * the low-level rtc_read_alarm_internal() function.
 152          *
 153          * So, when the two timestamps disagree, we just loop and do
 154          * the process again to get a fully consistent set of values.
 155          *
 156          * This could all instead be done in the lower level driver,
 157          * but since more than one lower level RTC implementation needs it,
 158          * then it's probably best best to do it here instead of there..
 159          */
 160
 161         /* Get the "before" timestamp */
 162         err = rtc_read_time(rtc, &before);
 163         if (err < 0)
 164                 return err;
 165         do {
 166                 if (!first_time)
 167                         memcpy(&before, &now, sizeof(struct rtc_time));
 168                 first_time = 0;
 169
 170                 /* get the RTC alarm values, which may be incomplete */
 171                 err = rtc_read_alarm_internal(rtc, alarm);
 172                 if (err)
 173                         return err;
 174                 if (!alarm->enabled)
 175                         return 0;
 176
 177                 /* get the "after" timestamp, to detect wrapped fields */
 178                 err = rtc_read_time(rtc, &now);
 179                 if (err < 0)
 180                         return err;
 181
 182                 /* note that tm_sec is a "don't care" value here: */
 183         } while (   before.tm_min   != now.tm_min
 184                  || before.tm_hour  != now.tm_hour
 185                  || before.tm_mon   != now.tm_mon
 186                  || before.tm_year  != now.tm_year
 187                  || before.tm_isdst != now.tm_isdst);
 188
 189         /* Fill in any missing alarm fields using the timestamp */
 190         if (alarm->time.tm_sec == -1)
 191                 alarm->time.tm_sec = now.tm_sec;
 192         if (alarm->time.tm_min == -1)
 193                 alarm->time.tm_min = now.tm_min;
 194         if (alarm->time.tm_hour == -1)
 195                 alarm->time.tm_hour = now.tm_hour;
 196         if (alarm->time.tm_mday == -1)
 197                 alarm->time.tm_mday = now.tm_mday;
 198         if (alarm->time.tm_mon == -1)
 199                 alarm->time.tm_mon = now.tm_mon;
 200         if (alarm->time.tm_year == -1)
 201                 alarm->time.tm_year = now.tm_year;
 202         return 0;
 203 }
 204 EXPORT_SYMBOL_GPL(rtc_read_alarm);
 205
 206 int rtc_set_alarm(struct rtc_device *rtc, struct rtc_wkalrm *alarm)
 207 {
 208         int err;
 209
 210         err = rtc_valid_tm(&alarm->time);
 211         if (err != 0)
 212                 return err;
 213
 214         err = mutex_lock_interruptible(&rtc->ops_lock);
 215         if (err)
 216                 return -EBUSY;
 217
 218         if (!rtc->ops)
 219                 err = -ENODEV;
 220         else if (!rtc->ops->set_alarm)
 221                 err = -EINVAL;
 222         else
 223                 err = rtc->ops->set_alarm(rtc->dev.parent, alarm);
 224
 225         mutex_unlock(&rtc->ops_lock);
 226         return err;
 227 }
 228 EXPORT_SYMBOL_GPL(rtc_set_alarm);
 229
 230 /**
 231  * rtc_update_irq - report RTC periodic, alarm, and/or update irqs
 232  * @rtc: the rtc device
 233  * @num: how many irqs are being reported (usually one)
 234  * @events: mask of RTC_IRQF with one or more of RTC_PF, RTC_AF, RTC_UF
 235  * Context: in_interrupt(), irqs blocked
 236  */
 237 void rtc_update_irq(struct rtc_device *rtc,
 238                 unsigned long num, unsigned long events)
 239 {
 240         spin_lock(&rtc->irq_lock);
 241         rtc->irq_data = (rtc->irq_data + (num << 8)) | events;
 242         spin_unlock(&rtc->irq_lock);
 243
 244         spin_lock(&rtc->irq_task_lock);
 245         if (rtc->irq_task)
 246                 rtc->irq_task->func(rtc->irq_task->private_data);
 247         spin_unlock(&rtc->irq_task_lock);
 248
 249         wake_up_interruptible(&rtc->irq_queue);
 250         kill_fasync(&rtc->async_queue, SIGIO, POLL_IN);
 251 }
 252 EXPORT_SYMBOL_GPL(rtc_update_irq);
 253
 254 struct rtc_device *rtc_class_open(char *name)
 255 {
 256         struct device *dev;
 257         struct rtc_device *rtc = NULL;
 258
 259         down(&rtc_class->sem);
 260         list_for_each_entry(dev, &rtc_class->devices, node) {
 261                 if (strncmp(dev->bus_id, name, BUS_ID_SIZE) == 0) {
 262                         dev = get_device(dev);
 263                         if (dev)
 264                                 rtc = to_rtc_device(dev);
 265                         break;
 266                 }
 267         }
 268
 269         if (rtc) {
 270                 if (!try_module_get(rtc->owner)) {
 271                         put_device(dev);
 272                         rtc = NULL;
 273                 }
 274         }
 275         up(&rtc_class->sem);
 276
 277         return rtc;
 278 }
 279 EXPORT_SYMBOL_GPL(rtc_class_open);
 280
 281 void rtc_class_close(struct rtc_device *rtc)
 282 {
 283         module_put(rtc->owner);
 284         put_device(&rtc->dev);
 285 }
 286 EXPORT_SYMBOL_GPL(rtc_class_close);
 287
 288 int rtc_irq_register(struct rtc_device *rtc, struct rtc_task *task)
 289 {
 290         int retval = -EBUSY;
 291
 292         if (task == NULL || task->func == NULL)
 293                 return -EINVAL;
 294
 295         /* Cannot register while the char dev is in use */
 296         if (!(mutex_trylock(&rtc->char_lock)))
 297                 return -EBUSY;
 298
 299         spin_lock_irq(&rtc->irq_task_lock);
 300         if (rtc->irq_task == NULL) {
 301                 rtc->irq_task = task;
 302                 retval = 0;
 303         }
 304         spin_unlock_irq(&rtc->irq_task_lock);
 305
 306         mutex_unlock(&rtc->char_lock);
 307
 308         return retval;
 309 }
 310 EXPORT_SYMBOL_GPL(rtc_irq_register);
 311
 312 void rtc_irq_unregister(struct rtc_device *rtc, struct rtc_task *task)
 313 {
 314         spin_lock_irq(&rtc->irq_task_lock);
 315         if (rtc->irq_task == task)
 316                 rtc->irq_task = NULL;
 317         spin_unlock_irq(&rtc->irq_task_lock);
 318 }
 319 EXPORT_SYMBOL_GPL(rtc_irq_unregister);
 320
 321 /**
 322  * rtc_irq_set_state - enable/disable 2^N Hz periodic IRQs
 323  * @rtc: the rtc device
 324  * @task: currently registered with rtc_irq_register()
 325  * @enabled: true to enable periodic IRQs
 326  * Context: any
 327  *
 328  * Note that rtc_irq_set_freq() should previously have been used to
 329  * specify the desired frequency of periodic IRQ task->func() callbacks.
 330  */
 331 int rtc_irq_set_state(struct rtc_device *rtc, struct rtc_task *task, int enabled)
 332 {
 333         int err = 0;
 334         unsigned long flags;
 335
 336         if (rtc->ops->irq_set_state == NULL)
 337                 return -ENXIO;
 338
 339         spin_lock_irqsave(&rtc->irq_task_lock, flags);
 340         if (rtc->irq_task != NULL && task == NULL)
 341                 err = -EBUSY;
 342         if (rtc->irq_task != task)
 343                 err = -EACCES;
 344         spin_unlock_irqrestore(&rtc->irq_task_lock, flags);
 345
 346         if (err == 0)
 347                 err = rtc->ops->irq_set_state(rtc->dev.parent, enabled);
 348
 349         return err;
 350 }
 351 EXPORT_SYMBOL_GPL(rtc_irq_set_state);
 352
 353 /**
 354  * rtc_irq_set_freq - set 2^N Hz periodic IRQ frequency for IRQ
 355  * @rtc: the rtc device
 356  * @task: currently registered with rtc_irq_register()
 357  * @freq: positive frequency with which task->func() will be called
 358  * Context: any
 359  *
 360  * Note that rtc_irq_set_state() is used to enable or disable the
 361  * periodic IRQs.
 362  */
 363 int rtc_irq_set_freq(struct rtc_device *rtc, struct rtc_task *task, int freq)
 364 {
 365         int err = 0;
 366         unsigned long flags;
 367
 368         if (rtc->ops->irq_set_freq == NULL)
 369                 return -ENXIO;
 370
 371         if (!is_power_of_2(freq))
 372                 return -EINVAL;
 373
 374         spin_lock_irqsave(&rtc->irq_task_lock, flags);
 375         if (rtc->irq_task != NULL && task == NULL)
 376                 err = -EBUSY;
 377         if (rtc->irq_task != task)
 378                 err = -EACCES;
 379         spin_unlock_irqrestore(&rtc->irq_task_lock, flags);
 380
 381         if (err == 0) {
 382                 err = rtc->ops->irq_set_freq(rtc->dev.parent, freq);
 383                 if (err == 0)
 384                         rtc->irq_freq = freq;
 385         }
 386         return err;
 387 }
 388 EXPORT_SYMBOL_GPL(rtc_irq_set_freq);