drivers/rtc/dev.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * RTC subsystem, dev interface
   4  *
   5  * Copyright (C) 2005 Tower Technologies
   6  * Author: Alessandro Zummo <a.zummo@towertech.it>
   7  *
   8  * based on arch/arm/common/rtctime.c
   9  */
  10
  11 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  12
  13 #include <linux/module.h>
  14 #include <linux/rtc.h>
  15 #include <linux/sched/signal.h>
  16 #include "rtc-core.h"
  17
  18 static dev_t rtc_devt;
  19
  20 #define RTC_DEV_MAX 16 /* 16 RTCs should be enough for everyone... */
  21
  22 static int rtc_dev_open(struct inode *inode, struct file *file)
  23 {
  24         struct rtc_device *rtc = container_of(inode->i_cdev,
  25                                         struct rtc_device, char_dev);
  26
  27         if (test_and_set_bit_lock(RTC_DEV_BUSY, &rtc->flags))
  28                 return -EBUSY;
  29
  30         file->private_data = rtc;
  31
  32         spin_lock_irq(&rtc->irq_lock);
  33         rtc->irq_data = 0;
  34         spin_unlock_irq(&rtc->irq_lock);
  35
  36         return 0;
  37 }
  38
  39 #ifdef CONFIG_RTC_INTF_DEV_UIE_EMUL
  40 /*
  41  * Routine to poll RTC seconds field for change as often as possible,
  42  * after first RTC_UIE use timer to reduce polling
  43  */
  44 static void rtc_uie_task(struct work_struct *work)
  45 {
  46         struct rtc_device *rtc =
  47                 container_of(work, struct rtc_device, uie_task);
  48         struct rtc_time tm;
  49         int num = 0;
  50         int err;
  51
  52         err = rtc_read_time(rtc, &tm);
  53
  54         spin_lock_irq(&rtc->irq_lock);
  55         if (rtc->stop_uie_polling || err) {
  56                 rtc->uie_task_active = 0;
  57         } else if (rtc->oldsecs != tm.tm_sec) {
  58                 num = (tm.tm_sec + 60 - rtc->oldsecs) % 60;
  59                 rtc->oldsecs = tm.tm_sec;
  60                 rtc->uie_timer.expires = jiffies + HZ - (HZ / 10);
  61                 rtc->uie_timer_active = 1;
  62                 rtc->uie_task_active = 0;
  63                 add_timer(&rtc->uie_timer);
  64         } else if (schedule_work(&rtc->uie_task) == 0) {
  65                 rtc->uie_task_active = 0;
  66         }
  67         spin_unlock_irq(&rtc->irq_lock);
  68         if (num)
  69                 rtc_handle_legacy_irq(rtc, num, RTC_UF);
  70 }
  71
  72 static void rtc_uie_timer(struct timer_list *t)
  73 {
  74         struct rtc_device *rtc = from_timer(rtc, t, uie_timer);
  75         unsigned long flags;
  76
  77         spin_lock_irqsave(&rtc->irq_lock, flags);
  78         rtc->uie_timer_active = 0;
  79         rtc->uie_task_active = 1;
  80         if ((schedule_work(&rtc->uie_task) == 0))
  81                 rtc->uie_task_active = 0;
  82         spin_unlock_irqrestore(&rtc->irq_lock, flags);
  83 }
  84
  85 static int clear_uie(struct rtc_device *rtc)
  86 {
  87         spin_lock_irq(&rtc->irq_lock);
  88         if (rtc->uie_irq_active) {
  89                 rtc->stop_uie_polling = 1;
  90                 if (rtc->uie_timer_active) {
  91                         spin_unlock_irq(&rtc->irq_lock);
  92                         del_timer_sync(&rtc->uie_timer);
  93                         spin_lock_irq(&rtc->irq_lock);
  94                         rtc->uie_timer_active = 0;
  95                 }
  96                 if (rtc->uie_task_active) {
  97                         spin_unlock_irq(&rtc->irq_lock);
  98                         flush_scheduled_work();
  99                         spin_lock_irq(&rtc->irq_lock);
 100                 }
 101                 rtc->uie_irq_active = 0;
 102         }
 103         spin_unlock_irq(&rtc->irq_lock);
 104         return 0;
 105 }
 106
 107 static int set_uie(struct rtc_device *rtc)
 108 {
 109         struct rtc_time tm;
 110         int err;
 111
 112         err = rtc_read_time(rtc, &tm);
 113         if (err)
 114                 return err;
 115         spin_lock_irq(&rtc->irq_lock);
 116         if (!rtc->uie_irq_active) {
 117                 rtc->uie_irq_active = 1;
 118                 rtc->stop_uie_polling = 0;
 119                 rtc->oldsecs = tm.tm_sec;
 120                 rtc->uie_task_active = 1;
 121                 if (schedule_work(&rtc->uie_task) == 0)
 122                         rtc->uie_task_active = 0;
 123         }
 124         rtc->irq_data = 0;
 125         spin_unlock_irq(&rtc->irq_lock);
 126         return 0;
 127 }
 128
 129 int rtc_dev_update_irq_enable_emul(struct rtc_device *rtc, unsigned int enabled)
 130 {
 131         if (enabled)
 132                 return set_uie(rtc);
 133         else
 134                 return clear_uie(rtc);
 135 }
 136 EXPORT_SYMBOL(rtc_dev_update_irq_enable_emul);
 137
 138 #endif /* CONFIG_RTC_INTF_DEV_UIE_EMUL */
 139
 140 static ssize_t
 141 rtc_dev_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
 142 {
 143         struct rtc_device *rtc = file->private_data;
 144
 145         DECLARE_WAITQUEUE(wait, current);
 146         unsigned long data;
 147         ssize_t ret;
 148
 149         if (count != sizeof(unsigned int) && count < sizeof(unsigned long))
 150                 return -EINVAL;
 151
 152         add_wait_queue(&rtc->irq_queue, &wait);
 153         do {
 154                 __set_current_state(TASK_INTERRUPTIBLE);
 155
 156                 spin_lock_irq(&rtc->irq_lock);
 157                 data = rtc->irq_data;
 158                 rtc->irq_data = 0;
 159                 spin_unlock_irq(&rtc->irq_lock);
 160
 161                 if (data != 0) {
 162                         ret = 0;
 163                         break;
 164                 }
 165                 if (file->f_flags & O_NONBLOCK) {
 166                         ret = -EAGAIN;
 167                         break;
 168                 }
 169                 if (signal_pending(current)) {
 170                         ret = -ERESTARTSYS;
 171                         break;
 172                 }
 173                 schedule();
 174         } while (1);
 175         set_current_state(TASK_RUNNING);
 176         remove_wait_queue(&rtc->irq_queue, &wait);
 177
 178         if (ret == 0) {
 179                 if (sizeof(int) != sizeof(long) &&
 180                     count == sizeof(unsigned int))
 181                         ret = put_user(data, (unsigned int __user *)buf) ?:
 182                                 sizeof(unsigned int);
 183                 else
 184                         ret = put_user(data, (unsigned long __user *)buf) ?:
 185                                 sizeof(unsigned long);
 186         }
 187         return ret;
 188 }
 189
 190 static __poll_t rtc_dev_poll(struct file *file, poll_table *wait)
 191 {
 192         struct rtc_device *rtc = file->private_data;
 193         unsigned long data;
 194
 195         poll_wait(file, &rtc->irq_queue, wait);
 196
 197         data = rtc->irq_data;
 198
 199         return (data != 0) ? (EPOLLIN | EPOLLRDNORM) : 0;
 200 }
 201
 202 static long rtc_dev_ioctl(struct file *file,
 203                           unsigned int cmd, unsigned long arg)
 204 {
 205         int err = 0;
 206         struct rtc_device *rtc = file->private_data;
 207         const struct rtc_class_ops *ops = rtc->ops;
 208         struct rtc_time tm;
 209         struct rtc_wkalrm alarm;
 210         void __user *uarg = (void __user *)arg;
 211
 212         err = mutex_lock_interruptible(&rtc->ops_lock);
 213         if (err)
 214                 return err;
 215
 216         /* check that the calling task has appropriate permissions
 217          * for certain ioctls. doing this check here is useful
 218          * to avoid duplicate code in each driver.
 219          */
 220         switch (cmd) {
 221         case RTC_EPOCH_SET:
 222         case RTC_SET_TIME:
 223                 if (!capable(CAP_SYS_TIME))
 224                         err = -EACCES;
 225                 break;
 226
 227         case RTC_IRQP_SET:
 228                 if (arg > rtc->max_user_freq && !capable(CAP_SYS_RESOURCE))
 229                         err = -EACCES;
 230                 break;
 231
 232         case RTC_PIE_ON:
 233                 if (rtc->irq_freq > rtc->max_user_freq &&
 234                     !capable(CAP_SYS_RESOURCE))
 235                         err = -EACCES;
 236                 break;
 237         }
 238
 239         if (err)
 240                 goto done;
 241
 242         /*
 243          * Drivers *SHOULD NOT* provide ioctl implementations
 244          * for these requests.  Instead, provide methods to
 245          * support the following code, so that the RTC's main
 246          * features are accessible without using ioctls.
 247          *
 248          * RTC and alarm times will be in UTC, by preference,
 249          * but dual-booting with MS-Windows implies RTCs must
 250          * use the local wall clock time.
 251          */
 252
 253         switch (cmd) {
 254         case RTC_ALM_READ:
 255                 mutex_unlock(&rtc->ops_lock);
 256
 257                 err = rtc_read_alarm(rtc, &alarm);
 258                 if (err < 0)
 259                         return err;
 260
 261                 if (copy_to_user(uarg, &alarm.time, sizeof(tm)))
 262                         err = -EFAULT;
 263                 return err;
 264
 265         case RTC_ALM_SET:
 266                 mutex_unlock(&rtc->ops_lock);
 267
 268                 if (copy_from_user(&alarm.time, uarg, sizeof(tm)))
 269                         return -EFAULT;
 270
 271                 alarm.enabled = 0;
 272                 alarm.pending = 0;
 273                 alarm.time.tm_wday = -1;
 274                 alarm.time.tm_yday = -1;
 275                 alarm.time.tm_isdst = -1;
 276
 277                 /* RTC_ALM_SET alarms may be up to 24 hours in the future.
 278                  * Rather than expecting every RTC to implement "don't care"
 279                  * for day/month/year fields, just force the alarm to have
 280                  * the right values for those fields.
 281                  *
 282                  * RTC_WKALM_SET should be used instead.  Not only does it
 283                  * eliminate the need for a separate RTC_AIE_ON call, it
 284                  * doesn't have the "alarm 23:59:59 in the future" race.
 285                  *
 286                  * NOTE:  some legacy code may have used invalid fields as
 287                  * wildcards, exposing hardware "periodic alarm" capabilities.
 288                  * Not supported here.
 289                  */
 290                 {
 291                         time64_t now, then;
 292
 293                         err = rtc_read_time(rtc, &tm);
 294                         if (err < 0)
 295                                 return err;
 296                         now = rtc_tm_to_time64(&tm);
 297
 298                         alarm.time.tm_mday = tm.tm_mday;
 299                         alarm.time.tm_mon = tm.tm_mon;
 300                         alarm.time.tm_year = tm.tm_year;
 301                         err  = rtc_valid_tm(&alarm.time);
 302                         if (err < 0)
 303                                 return err;
 304                         then = rtc_tm_to_time64(&alarm.time);
 305
 306                         /* alarm may need to wrap into tomorrow */
 307                         if (then < now) {
 308                                 rtc_time64_to_tm(now + 24 * 60 * 60, &tm);
 309                                 alarm.time.tm_mday = tm.tm_mday;
 310                                 alarm.time.tm_mon = tm.tm_mon;
 311                                 alarm.time.tm_year = tm.tm_year;
 312                         }
 313                 }
 314
 315                 return rtc_set_alarm(rtc, &alarm);
 316
 317         case RTC_RD_TIME:
 318                 mutex_unlock(&rtc->ops_lock);
 319
 320                 err = rtc_read_time(rtc, &tm);
 321                 if (err < 0)
 322                         return err;
 323
 324                 if (copy_to_user(uarg, &tm, sizeof(tm)))
 325                         err = -EFAULT;
 326                 return err;
 327
 328         case RTC_SET_TIME:
 329                 mutex_unlock(&rtc->ops_lock);
 330
 331                 if (copy_from_user(&tm, uarg, sizeof(tm)))
 332                         return -EFAULT;
 333
 334                 return rtc_set_time(rtc, &tm);
 335
 336         case RTC_PIE_ON:
 337                 err = rtc_irq_set_state(rtc, 1);
 338                 break;
 339
 340         case RTC_PIE_OFF:
 341                 err = rtc_irq_set_state(rtc, 0);
 342                 break;
 343
 344         case RTC_AIE_ON:
 345                 mutex_unlock(&rtc->ops_lock);
 346                 return rtc_alarm_irq_enable(rtc, 1);
 347
 348         case RTC_AIE_OFF:
 349                 mutex_unlock(&rtc->ops_lock);
 350                 return rtc_alarm_irq_enable(rtc, 0);
 351
 352         case RTC_UIE_ON:
 353                 mutex_unlock(&rtc->ops_lock);
 354                 return rtc_update_irq_enable(rtc, 1);
 355
 356         case RTC_UIE_OFF:
 357                 mutex_unlock(&rtc->ops_lock);
 358                 return rtc_update_irq_enable(rtc, 0);
 359
 360         case RTC_IRQP_SET:
 361                 err = rtc_irq_set_freq(rtc, arg);
 362                 break;
 363
 364         case RTC_IRQP_READ:
 365                 err = put_user(rtc->irq_freq, (unsigned long __user *)uarg);
 366                 break;
 367
 368         case RTC_WKALM_SET:
 369                 mutex_unlock(&rtc->ops_lock);
 370                 if (copy_from_user(&alarm, uarg, sizeof(alarm)))
 371                         return -EFAULT;
 372
 373                 return rtc_set_alarm(rtc, &alarm);
 374
 375         case RTC_WKALM_RD:
 376                 mutex_unlock(&rtc->ops_lock);
 377                 err = rtc_read_alarm(rtc, &alarm);
 378                 if (err < 0)
 379                         return err;
 380
 381                 if (copy_to_user(uarg, &alarm, sizeof(alarm)))
 382                         err = -EFAULT;
 383                 return err;
 384
 385         default:
 386                 /* Finally try the driver's ioctl interface */
 387                 if (ops->ioctl) {
 388                         err = ops->ioctl(rtc->dev.parent, cmd, arg);
 389                         if (err == -ENOIOCTLCMD)
 390                                 err = -ENOTTY;
 391                 } else {
 392                         err = -ENOTTY;
 393                 }
 394                 break;
 395         }
 396
 397 done:
 398         mutex_unlock(&rtc->ops_lock);
 399         return err;
 400 }
 401
 402 static int rtc_dev_fasync(int fd, struct file *file, int on)
 403 {
 404         struct rtc_device *rtc = file->private_data;
 405
 406         return fasync_helper(fd, file, on, &rtc->async_queue);
 407 }
 408
 409 static int rtc_dev_release(struct inode *inode, struct file *file)
 410 {
 411         struct rtc_device *rtc = file->private_data;
 412
 413         /* We shut down the repeating IRQs that userspace enabled,
 414          * since nothing is listening to them.
 415          *  - Update (UIE) ... currently only managed through ioctls
 416          *  - Periodic (PIE) ... also used through rtc_*() interface calls
 417          *
 418          * Leave the alarm alone; it may be set to trigger a system wakeup
 419          * later, or be used by kernel code, and is a one-shot event anyway.
 420          */
 421
 422         /* Keep ioctl until all drivers are converted */
 423         rtc_dev_ioctl(file, RTC_UIE_OFF, 0);
 424         rtc_update_irq_enable(rtc, 0);
 425         rtc_irq_set_state(rtc, 0);
 426
 427         clear_bit_unlock(RTC_DEV_BUSY, &rtc->flags);
 428         return 0;
 429 }
 430
 431 static const struct file_operations rtc_dev_fops = {
 432         .owner          = THIS_MODULE,
 433         .llseek         = no_llseek,
 434         .read           = rtc_dev_read,
 435         .poll           = rtc_dev_poll,
 436         .unlocked_ioctl = rtc_dev_ioctl,
 437         .open           = rtc_dev_open,
 438         .release        = rtc_dev_release,
 439         .fasync         = rtc_dev_fasync,
 440 };
 441
 442 /* insertion/removal hooks */
 443
 444 void rtc_dev_prepare(struct rtc_device *rtc)
 445 {
 446         if (!rtc_devt)
 447                 return;
 448
 449         if (rtc->id >= RTC_DEV_MAX) {
 450                 dev_dbg(&rtc->dev, "too many RTC devices\n");
 451                 return;
 452         }
 453
 454         rtc->dev.devt = MKDEV(MAJOR(rtc_devt), rtc->id);
 455
 456 #ifdef CONFIG_RTC_INTF_DEV_UIE_EMUL
 457         INIT_WORK(&rtc->uie_task, rtc_uie_task);
 458         timer_setup(&rtc->uie_timer, rtc_uie_timer, 0);
 459 #endif
 460
 461         cdev_init(&rtc->char_dev, &rtc_dev_fops);
 462         rtc->char_dev.owner = rtc->owner;
 463 }
 464
 465 void __init rtc_dev_init(void)
 466 {
 467         int err;
 468
 469         err = alloc_chrdev_region(&rtc_devt, 0, RTC_DEV_MAX, "rtc");
 470         if (err < 0)
 471                 pr_err("failed to allocate char dev region\n");
 472 }
 473
 474 void __exit rtc_dev_exit(void)
 475 {
 476         if (rtc_devt)
 477                 unregister_chrdev_region(rtc_devt, RTC_DEV_MAX);
 478 }