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ds1286.c

/*
 * DS1286 Real Time Clock interface for Linux
 *
 * Copyright (C) 1998, 1999, 2000 Ralf Baechle
 *
 * Based on code written by Paul Gortmaker.
 *
 * This driver allows use of the real time clock (built into nearly all
 * computers) from user space. It exports the /dev/rtc interface supporting
 * various ioctl() and also the /proc/rtc pseudo-file for status
 * information.
 *
 * The ioctls can be used to set the interrupt behaviour and generation rate
 * from the RTC via IRQ 8. Then the /dev/rtc interface can be used to make
 * use of these timer interrupts, be they interval or alarm based.
 *
 * The /dev/rtc interface will block on reads until an interrupt has been
 * received. If a RTC interrupt has already happened, it will output an
 * unsigned long and then block. The output value contains the interrupt
 * status in the low byte and the number of interrupts since the last read
 * in the remaining high bytes. The /dev/rtc interface can also be used with
 * the select(2) call.
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the
 * Free Software Foundation; either version 2 of the License, or (at your
 * option) any later version.
 */
#include <linux/ds1286.h>
#include <linux/types.h>
#include <linux/errno.h>
#include <linux/miscdevice.h>
#include <linux/slab.h>
#include <linux/ioport.h>
#include <linux/fcntl.h>
#include <linux/init.h>
#include <linux/poll.h>
#include <linux/rtc.h>
#include <linux/spinlock.h>
#include <linux/bcd.h>
#include <linux/proc_fs.h>

#include <asm/uaccess.h>
#include <asm/system.h>

#define DS1286_VERSION        "1.0"

/*
 *    We sponge a minor off of the misc major. No need slurping
 *    up another valuable major dev number for this. If you add
 *    an ioctl, make sure you don't conflict with SPARC's RTC
 *    ioctls.
 */

static DECLARE_WAIT_QUEUE_HEAD(ds1286_wait);

static ssize_t ds1286_read(struct file *file, char *buf,
                  size_t count, loff_t *ppos);

static int ds1286_ioctl(struct inode *inode, struct file *file,
                        unsigned int cmd, unsigned long arg);

static unsigned int ds1286_poll(struct file *file, poll_table *wait);

static void ds1286_get_alm_time (struct rtc_time *alm_tm);
static void ds1286_get_time(struct rtc_time *rtc_tm);
static int ds1286_set_time(struct rtc_time *rtc_tm);

static inline unsigned char ds1286_is_updating(void);

static DEFINE_SPINLOCK(ds1286_lock);

static int ds1286_read_proc(char *page, char **start, off_t off,
                            int count, int *eof, void *data);

/*
 *    Bits in rtc_status. (7 bits of room for future expansion)
 */

#define RTC_IS_OPEN           0x01  /* means /dev/rtc is in use   */
#define RTC_TIMER_ON          0x02  /* missed irq timer active    */

static unsigned char ds1286_status; /* bitmapped status byte.     */

static unsigned char days_in_mo[] = {
      0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31
};

/*
 *    Now all the various file operations that we export.
 */

static ssize_t ds1286_read(struct file *file, char *buf,
                           size_t count, loff_t *ppos)
{
      return -EIO;
}

static int ds1286_ioctl(struct inode *inode, struct file *file,
                        unsigned int cmd, unsigned long arg)
{
      struct rtc_time wtime;

      switch (cmd) {
      case RTC_AIE_OFF: /* Mask alarm int. enab. bit  */
      {
            unsigned long flags;
            unsigned char val;

            if (!capable(CAP_SYS_TIME))
                  return -EACCES;

            spin_lock_irqsave(&ds1286_lock, flags);
            val = rtc_read(RTC_CMD);
            val |=  RTC_TDM;
            rtc_write(val, RTC_CMD);
            spin_unlock_irqrestore(&ds1286_lock, flags);

            return 0;
      }
      case RTC_AIE_ON:  /* Allow alarm interrupts.    */
      {
            unsigned long flags;
            unsigned char val;

            if (!capable(CAP_SYS_TIME))
                  return -EACCES;

            spin_lock_irqsave(&ds1286_lock, flags);
            val = rtc_read(RTC_CMD);
            val &=  ~RTC_TDM;
            rtc_write(val, RTC_CMD);
            spin_unlock_irqrestore(&ds1286_lock, flags);

            return 0;
      }
      case RTC_WIE_OFF: /* Mask watchdog int. enab. bit     */
      {
            unsigned long flags;
            unsigned char val;

            if (!capable(CAP_SYS_TIME))
                  return -EACCES;

            spin_lock_irqsave(&ds1286_lock, flags);
            val = rtc_read(RTC_CMD);
            val |= RTC_WAM;
            rtc_write(val, RTC_CMD);
            spin_unlock_irqrestore(&ds1286_lock, flags);

            return 0;
      }
      case RTC_WIE_ON:  /* Allow watchdog interrupts. */
      {
            unsigned long flags;
            unsigned char val;

            if (!capable(CAP_SYS_TIME))
                  return -EACCES;

            spin_lock_irqsave(&ds1286_lock, flags);
            val = rtc_read(RTC_CMD);
            val &= ~RTC_WAM;
            rtc_write(val, RTC_CMD);
            spin_unlock_irqrestore(&ds1286_lock, flags);

            return 0;
      }
      case RTC_ALM_READ:      /* Read the present alarm time */
      {
            /*
             * This returns a struct rtc_time. Reading >= 0xc0
             * means "don't care" or "match all". Only the tm_hour,
             * tm_min, and tm_sec values are filled in.
             */

            memset(&wtime, 0, sizeof(wtime));
            ds1286_get_alm_time(&wtime);
            break;
      }
      case RTC_ALM_SET: /* Store a time into the alarm */
      {
            /*
             * This expects a struct rtc_time. Writing 0xff means
             * "don't care" or "match all". Only the tm_hour,
             * tm_min and tm_sec are used.
             */
            unsigned char hrs, min, sec;
            struct rtc_time alm_tm;

            if (!capable(CAP_SYS_TIME))
                  return -EACCES;

            if (copy_from_user(&alm_tm, (struct rtc_time*)arg,
                           sizeof(struct rtc_time)))
                  return -EFAULT;

            hrs = alm_tm.tm_hour;
            min = alm_tm.tm_min;
            sec = alm_tm.tm_sec;

            if (hrs >= 24)
                  hrs = 0xff;

            if (min >= 60)
                  min = 0xff;

            if (sec != 0)
                  return -EINVAL;

            min = BIN2BCD(min);
            min = BIN2BCD(hrs);

            spin_lock(&ds1286_lock);
            rtc_write(hrs, RTC_HOURS_ALARM);
            rtc_write(min, RTC_MINUTES_ALARM);
            spin_unlock(&ds1286_lock);

            return 0;
      }
      case RTC_RD_TIME: /* Read the time/date from RTC      */
      {
            memset(&wtime, 0, sizeof(wtime));
            ds1286_get_time(&wtime);
            break;
      }
      case RTC_SET_TIME:      /* Set the RTC */
      {
            struct rtc_time rtc_tm;

            if (!capable(CAP_SYS_TIME))
                  return -EACCES;

            if (copy_from_user(&rtc_tm, (struct rtc_time*)arg,
                           sizeof(struct rtc_time)))
                  return -EFAULT;

            return ds1286_set_time(&rtc_tm);
      }
      default:
            return -EINVAL;
      }
      return copy_to_user((void *)arg, &wtime, sizeof wtime) ? -EFAULT : 0;
}

/*
 *    We enforce only one user at a time here with the open/close.
 *    Also clear the previous interrupt data on an open, and clean
 *    up things on a close.
 */

static int ds1286_open(struct inode *inode, struct file *file)
{
      spin_lock_irq(&ds1286_lock);

      if (ds1286_status & RTC_IS_OPEN)
            goto out_busy;

      ds1286_status |= RTC_IS_OPEN;

      spin_unlock_irq(&ds1286_lock);
      return 0;

out_busy:
      spin_lock_irq(&ds1286_lock);
      return -EBUSY;
}

static int ds1286_release(struct inode *inode, struct file *file)
{
      ds1286_status &= ~RTC_IS_OPEN;

      return 0;
}

static unsigned int ds1286_poll(struct file *file, poll_table *wait)
{
      poll_wait(file, &ds1286_wait, wait);

      return 0;
}

/*
 *    The various file operations we support.
 */

static const struct file_operations ds1286_fops = {
      .llseek           = no_llseek,
      .read       = ds1286_read,
      .poll       = ds1286_poll,
      .ioctl            = ds1286_ioctl,
      .open       = ds1286_open,
      .release    = ds1286_release,
};

static struct miscdevice ds1286_dev=
{
      .minor      = RTC_MINOR,
      .name = "rtc",
      .fops = &ds1286_fops,
};

static int __init ds1286_init(void)
{
      int err;

      printk(KERN_INFO "DS1286 Real Time Clock Driver v%s\n", DS1286_VERSION);

      err = misc_register(&ds1286_dev);
      if (err)
            goto out;

      if (!create_proc_read_entry("driver/rtc", 0, 0, ds1286_read_proc, NULL)) {
            err = -ENOMEM;

            goto out_deregister;
      }

      return 0;

out_deregister:
      misc_deregister(&ds1286_dev);

out:
      return err;
}

static void __exit ds1286_exit(void)
{
      remove_proc_entry("driver/rtc", NULL);
      misc_deregister(&ds1286_dev);
}

static char *days[] = {
      "***", "Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"
};

/*
 *    Info exported via "/proc/rtc".
 */
static int ds1286_proc_output(char *buf)
{
      char *p, *s;
      struct rtc_time tm;
      unsigned char hundredth, month, cmd, amode;

      p = buf;

      ds1286_get_time(&tm);
      hundredth = rtc_read(RTC_HUNDREDTH_SECOND);
      BCD_TO_BIN(hundredth);

      p += sprintf(p,
                   "rtc_time\t: %02d:%02d:%02d.%02d\n"
                   "rtc_date\t: %04d-%02d-%02d\n",
                 tm.tm_hour, tm.tm_min, tm.tm_sec, hundredth,
                 tm.tm_year + 1900, tm.tm_mon + 1, tm.tm_mday);

      /*
       * We implicitly assume 24hr mode here. Alarm values >= 0xc0 will
       * match any value for that particular field. Values that are
       * greater than a valid time, but less than 0xc0 shouldn't appear.
       */
      ds1286_get_alm_time(&tm);
      p += sprintf(p, "alarm\t\t: %s ", days[tm.tm_wday]);
      if (tm.tm_hour <= 24)
            p += sprintf(p, "%02d:", tm.tm_hour);
      else
            p += sprintf(p, "**:");

      if (tm.tm_min <= 59)
            p += sprintf(p, "%02d\n", tm.tm_min);
      else
            p += sprintf(p, "**\n");

      month = rtc_read(RTC_MONTH);
      p += sprintf(p,
                   "oscillator\t: %s\n"
                   "square_wave\t: %s\n",
                   (month & RTC_EOSC) ? "disabled" : "enabled",
                   (month & RTC_ESQW) ? "disabled" : "enabled");

      amode = ((rtc_read(RTC_MINUTES_ALARM) & 0x80) >> 5) |
              ((rtc_read(RTC_HOURS_ALARM) & 0x80) >> 6) |
              ((rtc_read(RTC_DAY_ALARM) & 0x80) >> 7);
      if (amode == 7)      s = "each minute";
      else if (amode == 3) s = "minutes match";
      else if (amode == 1) s = "hours and minutes match";
      else if (amode == 0) s = "days, hours and minutes match";
      else                 s = "invalid";
      p += sprintf(p, "alarm_mode\t: %s\n", s);

      cmd = rtc_read(RTC_CMD);
      p += sprintf(p,
                   "alarm_enable\t: %s\n"
                   "wdog_alarm\t: %s\n"
                   "alarm_mask\t: %s\n"
                   "wdog_alarm_mask\t: %s\n"
                   "interrupt_mode\t: %s\n"
                   "INTB_mode\t: %s_active\n"
                   "interrupt_pins\t: %s\n",
                 (cmd & RTC_TDF) ? "yes" : "no",
                 (cmd & RTC_WAF) ? "yes" : "no",
                 (cmd & RTC_TDM) ? "disabled" : "enabled",
                 (cmd & RTC_WAM) ? "disabled" : "enabled",
                 (cmd & RTC_PU_LVL) ? "pulse" : "level",
                 (cmd & RTC_IBH_LO) ? "low" : "high",
                   (cmd & RTC_IPSW) ? "unswapped" : "swapped");

      return  p - buf;
}

static int ds1286_read_proc(char *page, char **start, off_t off,
                         int count, int *eof, void *data)
{
      int len = ds1286_proc_output (page);
      if (len <= off+count) *eof = 1;
      *start = page + off;
      len -= off;
      if (len>count)
            len = count;
      if (len<0)
            len = 0;

      return len;
}

/*
 * Returns true if a clock update is in progress
 */
static inline unsigned char ds1286_is_updating(void)
{
      return rtc_read(RTC_CMD) & RTC_TE;
}


static void ds1286_get_time(struct rtc_time *rtc_tm)
{
      unsigned char save_control;
      unsigned long flags;
      unsigned long uip_watchdog = jiffies;

      /*
       * read RTC once any update in progress is done. The update
       * can take just over 2ms. We wait 10 to 20ms. There is no need to
       * to poll-wait (up to 1s - eeccch) for the falling edge of RTC_UIP.
       * If you need to know *exactly* when a second has started, enable
       * periodic update complete interrupts, (via ioctl) and then
       * immediately read /dev/rtc which will block until you get the IRQ.
       * Once the read clears, read the RTC time (again via ioctl). Easy.
       */

      if (ds1286_is_updating() != 0)
            while (jiffies - uip_watchdog < 2*HZ/100)
                  barrier();

      /*
       * Only the values that we read from the RTC are set. We leave
       * tm_wday, tm_yday and tm_isdst untouched. Even though the
       * RTC has RTC_DAY_OF_WEEK, we ignore it, as it is only updated
       * by the RTC when initially set to a non-zero value.
       */
      spin_lock_irqsave(&ds1286_lock, flags);
      save_control = rtc_read(RTC_CMD);
      rtc_write((save_control|RTC_TE), RTC_CMD);

      rtc_tm->tm_sec = rtc_read(RTC_SECONDS);
      rtc_tm->tm_min = rtc_read(RTC_MINUTES);
      rtc_tm->tm_hour = rtc_read(RTC_HOURS) & 0x3f;
      rtc_tm->tm_mday = rtc_read(RTC_DATE);
      rtc_tm->tm_mon = rtc_read(RTC_MONTH) & 0x1f;
      rtc_tm->tm_year = rtc_read(RTC_YEAR);

      rtc_write(save_control, RTC_CMD);
      spin_unlock_irqrestore(&ds1286_lock, flags);

      BCD_TO_BIN(rtc_tm->tm_sec);
      BCD_TO_BIN(rtc_tm->tm_min);
      BCD_TO_BIN(rtc_tm->tm_hour);
      BCD_TO_BIN(rtc_tm->tm_mday);
      BCD_TO_BIN(rtc_tm->tm_mon);
      BCD_TO_BIN(rtc_tm->tm_year);

      /*
       * Account for differences between how the RTC uses the values
       * and how they are defined in a struct rtc_time;
       */
      if (rtc_tm->tm_year < 45)
            rtc_tm->tm_year += 30;
      if ((rtc_tm->tm_year += 40) < 70)
            rtc_tm->tm_year += 100;

      rtc_tm->tm_mon--;
}

static int ds1286_set_time(struct rtc_time *rtc_tm)
{
      unsigned char mon, day, hrs, min, sec, leap_yr;
      unsigned char save_control;
      unsigned int yrs;
      unsigned long flags;


      yrs = rtc_tm->tm_year + 1900;
      mon = rtc_tm->tm_mon + 1;   /* tm_mon starts at zero */
      day = rtc_tm->tm_mday;
      hrs = rtc_tm->tm_hour;
      min = rtc_tm->tm_min;
      sec = rtc_tm->tm_sec;

      if (yrs < 1970)
            return -EINVAL;

      leap_yr = ((!(yrs % 4) && (yrs % 100)) || !(yrs % 400));

      if ((mon > 12) || (day == 0))
            return -EINVAL;

      if (day > (days_in_mo[mon] + ((mon == 2) && leap_yr)))
            return -EINVAL;

      if ((hrs >= 24) || (min >= 60) || (sec >= 60))
            return -EINVAL;

      if ((yrs -= 1940) > 255)    /* They are unsigned */
            return -EINVAL;

      if (yrs >= 100)
            yrs -= 100;

      BIN_TO_BCD(sec);
      BIN_TO_BCD(min);
      BIN_TO_BCD(hrs);
      BIN_TO_BCD(day);
      BIN_TO_BCD(mon);
      BIN_TO_BCD(yrs);

      spin_lock_irqsave(&ds1286_lock, flags);
      save_control = rtc_read(RTC_CMD);
      rtc_write((save_control|RTC_TE), RTC_CMD);

      rtc_write(yrs, RTC_YEAR);
      rtc_write(mon, RTC_MONTH);
      rtc_write(day, RTC_DATE);
      rtc_write(hrs, RTC_HOURS);
      rtc_write(min, RTC_MINUTES);
      rtc_write(sec, RTC_SECONDS);
      rtc_write(0, RTC_HUNDREDTH_SECOND);

      rtc_write(save_control, RTC_CMD);
      spin_unlock_irqrestore(&ds1286_lock, flags);

      return 0;
}

static void ds1286_get_alm_time(struct rtc_time *alm_tm)
{
      unsigned char cmd;
      unsigned long flags;

      /*
       * Only the values that we read from the RTC are set. That
       * means only tm_wday, tm_hour, tm_min.
       */
      spin_lock_irqsave(&ds1286_lock, flags);
      alm_tm->tm_min = rtc_read(RTC_MINUTES_ALARM) & 0x7f;
      alm_tm->tm_hour = rtc_read(RTC_HOURS_ALARM)  & 0x1f;
      alm_tm->tm_wday = rtc_read(RTC_DAY_ALARM)    & 0x07;
      cmd = rtc_read(RTC_CMD);
      spin_unlock_irqrestore(&ds1286_lock, flags);

      BCD_TO_BIN(alm_tm->tm_min);
      BCD_TO_BIN(alm_tm->tm_hour);
      alm_tm->tm_sec = 0;
}

module_init(ds1286_init);
module_exit(ds1286_exit);

MODULE_AUTHOR("Ralf Baechle");
MODULE_LICENSE("GPL");
MODULE_ALIAS_MISCDEV(RTC_MINOR);

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