Version:  2.6.24 2.6.25 2.6.26 2.6.27 2.6.28 2.6.29 2.6.30 2.6.31 2.6.32 2.6.33-rc7

Architecture:  x86 arm avr32 blackfin m68k m68knommu microblaze mips powerpc sh

   /*
    *      Real Time Clock interface for Linux
    *
    *      Copyright (C) 1996 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/driver/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.
   *
   *      Based on other minimal char device drivers, like Alan's
   *      watchdog, Ted's random, etc. etc.
   *
   *      1.07    Paul Gortmaker.
   *      1.08    Miquel van Smoorenburg: disallow certain things on the
   *              DEC Alpha as the CMOS clock is also used for other things.
   *      1.09    Nikita Schmidt: epoch support and some Alpha cleanup.
   *      1.09a   Pete Zaitcev: Sun SPARC
   *      1.09b   Jeff Garzik: Modularize, init cleanup
   *      1.09c   Jeff Garzik: SMP cleanup
   *      1.10    Paul Barton-Davis: add support for async I/O
   *      1.10a   Andrea Arcangeli: Alpha updates
   *      1.10b   Andrew Morton: SMP lock fix
   *      1.10c   Cesar Barros: SMP locking fixes and cleanup
   *      1.10d   Paul Gortmaker: delete paranoia check in rtc_exit
   *      1.10e   Maciej W. Rozycki: Handle DECstation's year weirdness.
   *      1.11    Takashi Iwai: Kernel access functions
   *                            rtc_register/rtc_unregister/rtc_control
   *      1.11a   Daniele Bellucci: Audit create_proc_read_entry in rtc_init
   *      1.12    Venkatesh Pallipadi: Hooks for emulating rtc on HPET base-timer
   *              CONFIG_HPET_EMULATE_RTC
   *      1.12a   Maciej W. Rozycki: Handle memory-mapped chips properly.
   *      1.12ac  Alan Cox: Allow read access to the day of week register
   *      1.12b   David John: Remove calls to the BKL.
   */
  
  #define RTC_VERSION             "1.12b"
  
  /*
   *      Note that *all* calls to CMOS_READ and CMOS_WRITE are done with
   *      interrupts disabled. Due to the index-port/data-port (0x70/0x71)
   *      design of the RTC, we don't want two different things trying to
   *      get to it at once. (e.g. the periodic 11 min sync from time.c vs.
   *      this driver.)
   */
  
  #include <linux/interrupt.h>
  #include <linux/module.h>
  #include <linux/kernel.h>
  #include <linux/types.h>
  #include <linux/miscdevice.h>
  #include <linux/ioport.h>
  #include <linux/fcntl.h>
  #include <linux/mc146818rtc.h>
  #include <linux/init.h>
  #include <linux/poll.h>
  #include <linux/proc_fs.h>
  #include <linux/seq_file.h>
  #include <linux/spinlock.h>
  #include <linux/sched.h>
  #include <linux/sysctl.h>
  #include <linux/wait.h>
  #include <linux/bcd.h>
  #include <linux/delay.h>
  #include <linux/uaccess.h>
  
  #include <asm/current.h>
  #include <asm/system.h>
  
  #ifdef CONFIG_X86
  #include <asm/hpet.h>
  #endif
  
  #ifdef CONFIG_SPARC32
  #include <linux/of.h>
  #include <linux/of_device.h>
  #include <asm/io.h>
  
  static unsigned long rtc_port;
  static int rtc_irq;
  #endif
  
 #ifdef  CONFIG_HPET_EMULATE_RTC
 #undef  RTC_IRQ
 #endif
 
 #ifdef RTC_IRQ
 static int rtc_has_irq = 1;
 #endif
 
 #ifndef CONFIG_HPET_EMULATE_RTC
 #define is_hpet_enabled()                       0
 #define hpet_set_alarm_time(hrs, min, sec)      0
 #define hpet_set_periodic_freq(arg)             0
 #define hpet_mask_rtc_irq_bit(arg)              0
 #define hpet_set_rtc_irq_bit(arg)               0
 #define hpet_rtc_timer_init()                   do { } while (0)
 #define hpet_rtc_dropped_irq()                  0
 #define hpet_register_irq_handler(h)            ({ 0; })
 #define hpet_unregister_irq_handler(h)          ({ 0; })
 #ifdef RTC_IRQ
 static irqreturn_t hpet_rtc_interrupt(int irq, void *dev_id)
 {
         return 0;
 }
 #endif
 #endif
 
 /*
  *      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 struct fasync_struct *rtc_async_queue;
 
 static DECLARE_WAIT_QUEUE_HEAD(rtc_wait);
 
 #ifdef RTC_IRQ
 static void rtc_dropped_irq(unsigned long data);
 
 static DEFINE_TIMER(rtc_irq_timer, rtc_dropped_irq, 0, 0);
 #endif
 
 static ssize_t rtc_read(struct file *file, char __user *buf,
                         size_t count, loff_t *ppos);
 
 static long rtc_ioctl(struct file *file, unsigned int cmd, unsigned long arg);
 static void rtc_get_rtc_time(struct rtc_time *rtc_tm);
 
 #ifdef RTC_IRQ
 static unsigned int rtc_poll(struct file *file, poll_table *wait);
 #endif
 
 static void get_rtc_alm_time(struct rtc_time *alm_tm);
 #ifdef RTC_IRQ
 static void set_rtc_irq_bit_locked(unsigned char bit);
 static void mask_rtc_irq_bit_locked(unsigned char bit);
 
 static inline void set_rtc_irq_bit(unsigned char bit)
 {
         spin_lock_irq(&rtc_lock);
         set_rtc_irq_bit_locked(bit);
         spin_unlock_irq(&rtc_lock);
 }
 
 static void mask_rtc_irq_bit(unsigned char bit)
 {
         spin_lock_irq(&rtc_lock);
         mask_rtc_irq_bit_locked(bit);
         spin_unlock_irq(&rtc_lock);
 }
 #endif
 
 #ifdef CONFIG_PROC_FS
 static int rtc_proc_open(struct inode *inode, struct file *file);
 #endif
 
 /*
  *      Bits in rtc_status. (6 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      */
 
 /*
  * rtc_status is never changed by rtc_interrupt, and ioctl/open/close is
  * protected by the spin lock rtc_lock. However, ioctl can still disable the
  * timer in rtc_status and then with del_timer after the interrupt has read
  * rtc_status but before mod_timer is called, which would then reenable the
  * timer (but you would need to have an awful timing before you'd trip on it)
  */
 static unsigned long rtc_status;        /* bitmapped status byte.       */
 static unsigned long rtc_freq;          /* Current periodic IRQ rate    */
 static unsigned long rtc_irq_data;      /* our output to the world      */
 static unsigned long rtc_max_user_freq = 64; /* > this, need CAP_SYS_RESOURCE */
 
 #ifdef RTC_IRQ
 /*
  * rtc_task_lock nests inside rtc_lock.
  */
 static DEFINE_SPINLOCK(rtc_task_lock);
 static rtc_task_t *rtc_callback;
 #endif
 
 /*
  *      If this driver ever becomes modularised, it will be really nice
  *      to make the epoch retain its value across module reload...
  */
 
 static unsigned long epoch = 1900;      /* year corresponding to 0x00   */
 
 static const unsigned char days_in_mo[] =
 {0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
 
 /*
  * Returns true if a clock update is in progress
  */
 static inline unsigned char rtc_is_updating(void)
 {
         unsigned long flags;
         unsigned char uip;
 
         spin_lock_irqsave(&rtc_lock, flags);
         uip = (CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP);
         spin_unlock_irqrestore(&rtc_lock, flags);
         return uip;
 }
 
 #ifdef RTC_IRQ
 /*
  *      A very tiny interrupt handler. It runs with IRQF_DISABLED set,
  *      but there is possibility of conflicting with the set_rtc_mmss()
  *      call (the rtc irq and the timer irq can easily run at the same
  *      time in two different CPUs). So we need to serialize
  *      accesses to the chip with the rtc_lock spinlock that each
  *      architecture should implement in the timer code.
  *      (See ./arch/XXXX/kernel/time.c for the set_rtc_mmss() function.)
  */
 
 static irqreturn_t rtc_interrupt(int irq, void *dev_id)
 {
         /*
          *      Can be an alarm interrupt, update complete interrupt,
          *      or a periodic interrupt. We store the status in the
          *      low byte and the number of interrupts received since
          *      the last read in the remainder of rtc_irq_data.
          */
 
         spin_lock(&rtc_lock);
         rtc_irq_data += 0x100;
         rtc_irq_data &= ~0xff;
         if (is_hpet_enabled()) {
                 /*
                  * In this case it is HPET RTC interrupt handler
                  * calling us, with the interrupt information
                  * passed as arg1, instead of irq.
                  */
                 rtc_irq_data |= (unsigned long)irq & 0xF0;
         } else {
                 rtc_irq_data |= (CMOS_READ(RTC_INTR_FLAGS) & 0xF0);
         }
 
         if (rtc_status & RTC_TIMER_ON)
                 mod_timer(&rtc_irq_timer, jiffies + HZ/rtc_freq + 2*HZ/100);
 
         spin_unlock(&rtc_lock);
 
         /* Now do the rest of the actions */
         spin_lock(&rtc_task_lock);
         if (rtc_callback)
                 rtc_callback->func(rtc_callback->private_data);
         spin_unlock(&rtc_task_lock);
         wake_up_interruptible(&rtc_wait);
 
         kill_fasync(&rtc_async_queue, SIGIO, POLL_IN);
 
         return IRQ_HANDLED;
 }
 #endif
 
 /*
  * sysctl-tuning infrastructure.
  */
 static ctl_table rtc_table[] = {
         {
                 .ctl_name       = CTL_UNNUMBERED,
                 .procname       = "max-user-freq",
                 .data           = &rtc_max_user_freq,
                 .maxlen         = sizeof(int),
                 .mode           = 0644,
                 .proc_handler   = &proc_dointvec,
         },
         { .ctl_name = 0 }
 };
 
 static ctl_table rtc_root[] = {
         {
                 .ctl_name       = CTL_UNNUMBERED,
                 .procname       = "rtc",
                 .mode           = 0555,
                 .child          = rtc_table,
         },
         { .ctl_name = 0 }
 };
 
 static ctl_table dev_root[] = {
         {
                 .ctl_name       = CTL_DEV,
                 .procname       = "dev",
                 .mode           = 0555,
                 .child          = rtc_root,
         },
         { .ctl_name = 0 }
 };
 
 static struct ctl_table_header *sysctl_header;
 
 static int __init init_sysctl(void)
 {
     sysctl_header = register_sysctl_table(dev_root);
     return 0;
 }
 
 static void __exit cleanup_sysctl(void)
 {
     unregister_sysctl_table(sysctl_header);
 }
 
 /*
  *      Now all the various file operations that we export.
  */
 
 static ssize_t rtc_read(struct file *file, char __user *buf,
                         size_t count, loff_t *ppos)
 {
 #ifndef RTC_IRQ
         return -EIO;
 #else
         DECLARE_WAITQUEUE(wait, current);
         unsigned long data;
         ssize_t retval;
 
         if (rtc_has_irq == 0)
                 return -EIO;
 
         /*
          * Historically this function used to assume that sizeof(unsigned long)
          * is the same in userspace and kernelspace.  This lead to problems
          * for configurations with multiple ABIs such a the MIPS o32 and 64
          * ABIs supported on the same kernel.  So now we support read of both
          * 4 and 8 bytes and assume that's the sizeof(unsigned long) in the
          * userspace ABI.
          */
         if (count != sizeof(unsigned int) && count !=  sizeof(unsigned long))
                 return -EINVAL;
 
         add_wait_queue(&rtc_wait, &wait);
 
         do {
                 /* First make it right. Then make it fast. Putting this whole
                  * block within the parentheses of a while would be too
                  * confusing. And no, xchg() is not the answer. */
 
                 __set_current_state(TASK_INTERRUPTIBLE);
 
                 spin_lock_irq(&rtc_lock);
                 data = rtc_irq_data;
                 rtc_irq_data = 0;
                 spin_unlock_irq(&rtc_lock);
 
                 if (data != 0)
                         break;
 
                 if (file->f_flags & O_NONBLOCK) {
                         retval = -EAGAIN;
                         goto out;
                 }
                 if (signal_pending(current)) {
                         retval = -ERESTARTSYS;
                         goto out;
                 }
                 schedule();
         } while (1);
 
         if (count == sizeof(unsigned int)) {
                 retval = put_user(data,
                                   (unsigned int __user *)buf) ?: sizeof(int);
         } else {
                 retval = put_user(data,
                                   (unsigned long __user *)buf) ?: sizeof(long);
         }
         if (!retval)
                 retval = count;
  out:
         __set_current_state(TASK_RUNNING);
         remove_wait_queue(&rtc_wait, &wait);
 
         return retval;
 #endif
 }
 
 static int rtc_do_ioctl(unsigned int cmd, unsigned long arg, int kernel)
 {
         struct rtc_time wtime;
 
 #ifdef RTC_IRQ
         if (rtc_has_irq == 0) {
                 switch (cmd) {
                 case RTC_AIE_OFF:
                 case RTC_AIE_ON:
                 case RTC_PIE_OFF:
                 case RTC_PIE_ON:
                 case RTC_UIE_OFF:
                 case RTC_UIE_ON:
                 case RTC_IRQP_READ:
                 case RTC_IRQP_SET:
                         return -EINVAL;
                 };
         }
 #endif
 
         switch (cmd) {
 #ifdef RTC_IRQ
         case RTC_AIE_OFF:       /* Mask alarm int. enab. bit    */
         {
                 mask_rtc_irq_bit(RTC_AIE);
                 return 0;
         }
         case RTC_AIE_ON:        /* Allow alarm interrupts.      */
         {
                 set_rtc_irq_bit(RTC_AIE);
                 return 0;
         }
         case RTC_PIE_OFF:       /* Mask periodic int. enab. bit */
         {
                 /* can be called from isr via rtc_control() */
                 unsigned long flags;
 
                 spin_lock_irqsave(&rtc_lock, flags);
                 mask_rtc_irq_bit_locked(RTC_PIE);
                 if (rtc_status & RTC_TIMER_ON) {
                         rtc_status &= ~RTC_TIMER_ON;
                         del_timer(&rtc_irq_timer);
                 }
                 spin_unlock_irqrestore(&rtc_lock, flags);
 
                 return 0;
         }
         case RTC_PIE_ON:        /* Allow periodic ints          */
         {
                 /* can be called from isr via rtc_control() */
                 unsigned long flags;
 
                 /*
                  * We don't really want Joe User enabling more
                  * than 64Hz of interrupts on a multi-user machine.
                  */
                 if (!kernel && (rtc_freq > rtc_max_user_freq) &&
                                                 (!capable(CAP_SYS_RESOURCE)))
                         return -EACCES;
 
                 spin_lock_irqsave(&rtc_lock, flags);
                 if (!(rtc_status & RTC_TIMER_ON)) {
                         mod_timer(&rtc_irq_timer, jiffies + HZ/rtc_freq +
                                         2*HZ/100);
                         rtc_status |= RTC_TIMER_ON;
                 }
                 set_rtc_irq_bit_locked(RTC_PIE);
                 spin_unlock_irqrestore(&rtc_lock, flags);
 
                 return 0;
         }
         case RTC_UIE_OFF:       /* Mask ints from RTC updates.  */
         {
                 mask_rtc_irq_bit(RTC_UIE);
                 return 0;
         }
         case RTC_UIE_ON:        /* Allow ints for RTC updates.  */
         {
                 set_rtc_irq_bit(RTC_UIE);
                 return 0;
         }
 #endif
         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(struct rtc_time));
                 get_rtc_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 (copy_from_user(&alm_tm, (struct rtc_time __user *)arg,
                                    sizeof(struct rtc_time)))
                         return -EFAULT;
 
                 hrs = alm_tm.tm_hour;
                 min = alm_tm.tm_min;
                 sec = alm_tm.tm_sec;
 
                 spin_lock_irq(&rtc_lock);
                 if (hpet_set_alarm_time(hrs, min, sec)) {
                         /*
                          * Fallthru and set alarm time in CMOS too,
                          * so that we will get proper value in RTC_ALM_READ
                          */
                 }
                 if (!(CMOS_READ(RTC_CONTROL) & RTC_DM_BINARY) ||
                                                         RTC_ALWAYS_BCD) {
                         if (sec < 60)
                                 sec = bin2bcd(sec);
                         else
                                 sec = 0xff;
 
                         if (min < 60)
                                 min = bin2bcd(min);
                         else
                                 min = 0xff;
 
                         if (hrs < 24)
                                 hrs = bin2bcd(hrs);
                         else
                                 hrs = 0xff;
                 }
                 CMOS_WRITE(hrs, RTC_HOURS_ALARM);
                 CMOS_WRITE(min, RTC_MINUTES_ALARM);
                 CMOS_WRITE(sec, RTC_SECONDS_ALARM);
                 spin_unlock_irq(&rtc_lock);
 
                 return 0;
         }
         case RTC_RD_TIME:       /* Read the time/date from RTC  */
         {
                 memset(&wtime, 0, sizeof(struct rtc_time));
                 rtc_get_rtc_time(&wtime);
                 break;
         }
         case RTC_SET_TIME:      /* Set the RTC */
         {
                 struct rtc_time rtc_tm;
                 unsigned char mon, day, hrs, min, sec, leap_yr;
                 unsigned char save_control, save_freq_select;
                 unsigned int yrs;
 #ifdef CONFIG_MACH_DECSTATION
                 unsigned int real_yrs;
 #endif
 
                 if (!capable(CAP_SYS_TIME))
                         return -EACCES;
 
                 if (copy_from_user(&rtc_tm, (struct rtc_time __user *)arg,
                                    sizeof(struct rtc_time)))
                         return -EFAULT;
 
                 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;
 
                 yrs -= epoch;
                 if (yrs > 255)          /* They are unsigned */
                         return -EINVAL;
 
                 spin_lock_irq(&rtc_lock);
 #ifdef CONFIG_MACH_DECSTATION
                 real_yrs = yrs;
                 yrs = 72;
 
                 /*
                  * We want to keep the year set to 73 until March
                  * for non-leap years, so that Feb, 29th is handled
                  * correctly.
                  */
                 if (!leap_yr && mon < 3) {
                         real_yrs--;
                         yrs = 73;
                 }
 #endif
                 /* These limits and adjustments are independent of
                  * whether the chip is in binary mode or not.
                  */
                 if (yrs > 169) {
                         spin_unlock_irq(&rtc_lock);
                         return -EINVAL;
                 }
                 if (yrs >= 100)
                         yrs -= 100;
 
                 if (!(CMOS_READ(RTC_CONTROL) & RTC_DM_BINARY)
                     || RTC_ALWAYS_BCD) {
                         sec = bin2bcd(sec);
                         min = bin2bcd(min);
                         hrs = bin2bcd(hrs);
                         day = bin2bcd(day);
                         mon = bin2bcd(mon);
                         yrs = bin2bcd(yrs);
                 }
 
                 save_control = CMOS_READ(RTC_CONTROL);
                 CMOS_WRITE((save_control|RTC_SET), RTC_CONTROL);
                 save_freq_select = CMOS_READ(RTC_FREQ_SELECT);
                 CMOS_WRITE((save_freq_select|RTC_DIV_RESET2), RTC_FREQ_SELECT);
 
 #ifdef CONFIG_MACH_DECSTATION
                 CMOS_WRITE(real_yrs, RTC_DEC_YEAR);
 #endif
                 CMOS_WRITE(yrs, RTC_YEAR);
                 CMOS_WRITE(mon, RTC_MONTH);
                 CMOS_WRITE(day, RTC_DAY_OF_MONTH);
                 CMOS_WRITE(hrs, RTC_HOURS);
                 CMOS_WRITE(min, RTC_MINUTES);
                 CMOS_WRITE(sec, RTC_SECONDS);
 
                 CMOS_WRITE(save_control, RTC_CONTROL);
                 CMOS_WRITE(save_freq_select, RTC_FREQ_SELECT);
 
                 spin_unlock_irq(&rtc_lock);
                 return 0;
         }
 #ifdef RTC_IRQ
         case RTC_IRQP_READ:     /* Read the periodic IRQ rate.  */
         {
                 return put_user(rtc_freq, (unsigned long __user *)arg);
         }
         case RTC_IRQP_SET:      /* Set periodic IRQ rate.       */
         {
                 int tmp = 0;
                 unsigned char val;
                 /* can be called from isr via rtc_control() */
                 unsigned long flags;
 
                 /*
                  * The max we can do is 8192Hz.
                  */
                 if ((arg < 2) || (arg > 8192))
                         return -EINVAL;
                 /*
                  * We don't really want Joe User generating more
                  * than 64Hz of interrupts on a multi-user machine.
                  */
                 if (!kernel && (arg > rtc_max_user_freq) &&
                                         !capable(CAP_SYS_RESOURCE))
                         return -EACCES;
 
                 while (arg > (1<<tmp))
                         tmp++;
 
                 /*
                  * Check that the input was really a power of 2.
                  */
                 if (arg != (1<<tmp))
                         return -EINVAL;
 
                 rtc_freq = arg;
 
                 spin_lock_irqsave(&rtc_lock, flags);
                 if (hpet_set_periodic_freq(arg)) {
                         spin_unlock_irqrestore(&rtc_lock, flags);
                         return 0;
                 }
 
                 val = CMOS_READ(RTC_FREQ_SELECT) & 0xf0;
                 val |= (16 - tmp);
                 CMOS_WRITE(val, RTC_FREQ_SELECT);
                 spin_unlock_irqrestore(&rtc_lock, flags);
                 return 0;
         }
 #endif
         case RTC_EPOCH_READ:    /* Read the epoch.      */
         {
                 return put_user(epoch, (unsigned long __user *)arg);
         }
         case RTC_EPOCH_SET:     /* Set the epoch.       */
         {
                 /*
                  * There were no RTC clocks before 1900.
                  */
                 if (arg < 1900)
                         return -EINVAL;
 
                 if (!capable(CAP_SYS_TIME))
                         return -EACCES;
 
                 epoch = arg;
                 return 0;
         }
         default:
                 return -ENOTTY;
         }
         return copy_to_user((void __user *)arg,
                             &wtime, sizeof wtime) ? -EFAULT : 0;
 }
 
 static long rtc_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 {
         long ret;
         ret = rtc_do_ioctl(cmd, arg, 0);
         return ret;
 }
 
 /*
  *      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 rtc_open(struct inode *inode, struct file *file)
 {
         spin_lock_irq(&rtc_lock);
 
         if (rtc_status & RTC_IS_OPEN)
                 goto out_busy;
 
         rtc_status |= RTC_IS_OPEN;
 
         rtc_irq_data = 0;
         spin_unlock_irq(&rtc_lock);
         return 0;
 
 out_busy:
         spin_unlock_irq(&rtc_lock);
         return -EBUSY;
 }
 
 static int rtc_fasync(int fd, struct file *filp, int on)
 {
         return fasync_helper(fd, filp, on, &rtc_async_queue);
 }
 
 static int rtc_release(struct inode *inode, struct file *file)
 {
 #ifdef RTC_IRQ
         unsigned char tmp;
 
         if (rtc_has_irq == 0)
                 goto no_irq;
 
         /*
          * Turn off all interrupts once the device is no longer
          * in use, and clear the data.
          */
 
         spin_lock_irq(&rtc_lock);
         if (!hpet_mask_rtc_irq_bit(RTC_PIE | RTC_AIE | RTC_UIE)) {
                 tmp = CMOS_READ(RTC_CONTROL);
                 tmp &=  ~RTC_PIE;
                 tmp &=  ~RTC_AIE;
                 tmp &=  ~RTC_UIE;
                 CMOS_WRITE(tmp, RTC_CONTROL);
                 CMOS_READ(RTC_INTR_FLAGS);
         }
         if (rtc_status & RTC_TIMER_ON) {
                 rtc_status &= ~RTC_TIMER_ON;
                 del_timer(&rtc_irq_timer);
         }
         spin_unlock_irq(&rtc_lock);
 
 no_irq:
 #endif
 
         spin_lock_irq(&rtc_lock);
         rtc_irq_data = 0;
         rtc_status &= ~RTC_IS_OPEN;
         spin_unlock_irq(&rtc_lock);
 
         return 0;
 }
 
 #ifdef RTC_IRQ
 static unsigned int rtc_poll(struct file *file, poll_table *wait)
 {
         unsigned long l;
 
         if (rtc_has_irq == 0)
                 return 0;
 
         poll_wait(file, &rtc_wait, wait);
 
         spin_lock_irq(&rtc_lock);
         l = rtc_irq_data;
         spin_unlock_irq(&rtc_lock);
 
         if (l != 0)
                 return POLLIN | POLLRDNORM;
         return 0;
 }
 #endif
 
 int rtc_register(rtc_task_t *task)
 {
 #ifndef RTC_IRQ
         return -EIO;
 #else
         if (task == NULL || task->func == NULL)
                 return -EINVAL;
         spin_lock_irq(&rtc_lock);
         if (rtc_status & RTC_IS_OPEN) {
                 spin_unlock_irq(&rtc_lock);
                 return -EBUSY;
         }
         spin_lock(&rtc_task_lock);
         if (rtc_callback) {
                 spin_unlock(&rtc_task_lock);
                 spin_unlock_irq(&rtc_lock);
                 return -EBUSY;
         }
         rtc_status |= RTC_IS_OPEN;
         rtc_callback = task;
         spin_unlock(&rtc_task_lock);
         spin_unlock_irq(&rtc_lock);
         return 0;
 #endif
 }
 EXPORT_SYMBOL(rtc_register);
 
 int rtc_unregister(rtc_task_t *task)
 {
 #ifndef RTC_IRQ
         return -EIO;
 #else
         unsigned char tmp;
 
         spin_lock_irq(&rtc_lock);
         spin_lock(&rtc_task_lock);
         if (rtc_callback != task) {
                 spin_unlock(&rtc_task_lock);
                 spin_unlock_irq(&rtc_lock);
                 return -ENXIO;
         }
         rtc_callback = NULL;
 
         /* disable controls */
         if (!hpet_mask_rtc_irq_bit(RTC_PIE | RTC_AIE | RTC_UIE)) {
                 tmp = CMOS_READ(RTC_CONTROL);
                 tmp &= ~RTC_PIE;
                 tmp &= ~RTC_AIE;
                 tmp &= ~RTC_UIE;
                 CMOS_WRITE(tmp, RTC_CONTROL);
                 CMOS_READ(RTC_INTR_FLAGS);
         }
         if (rtc_status & RTC_TIMER_ON) {
                 rtc_status &= ~RTC_TIMER_ON;
                 del_timer(&rtc_irq_timer);
         }
         rtc_status &= ~RTC_IS_OPEN;
         spin_unlock(&rtc_task_lock);
         spin_unlock_irq(&rtc_lock);
         return 0;
 #endif
 }
 EXPORT_SYMBOL(rtc_unregister);
 
 int rtc_control(rtc_task_t *task, unsigned int cmd, unsigned long arg)
 {
 #ifndef RTC_IRQ
         return -EIO;
 #else
         unsigned long flags;
         if (cmd != RTC_PIE_ON && cmd != RTC_PIE_OFF && cmd != RTC_IRQP_SET)
                 return -EINVAL;
         spin_lock_irqsave(&rtc_task_lock, flags);
         if (rtc_callback != task) {
                 spin_unlock_irqrestore(&rtc_task_lock, flags);
                 return -ENXIO;
         }
         spin_unlock_irqrestore(&rtc_task_lock, flags);
         return rtc_do_ioctl(cmd, arg, 1);
 #endif
 }
 EXPORT_SYMBOL(rtc_control);
 
 /*
  *      The various file operations we support.
  */
 
 static const struct file_operations rtc_fops = {
         .owner          = THIS_MODULE,
         .llseek         = no_llseek,
         .read           = rtc_read,
 #ifdef RTC_IRQ
         .poll           = rtc_poll,
 #endif
         .unlocked_ioctl = rtc_ioctl,
         .open           = rtc_open,
         .release        = rtc_release,
         .fasync         = rtc_fasync,
 };
 
 static struct miscdevice rtc_dev = {
         .minor          = RTC_MINOR,
         .name           = "rtc",
         .fops           = &rtc_fops,
 };
 
 #ifdef CONFIG_PROC_FS
 static const struct file_operations rtc_proc_fops = {
         .owner          = THIS_MODULE,
         .open           = rtc_proc_open,
         .read           = seq_read,
         .llseek         = seq_lseek,
         .release        = single_release,
 };
 #endif
 
 static resource_size_t rtc_size;
 
 static struct resource * __init rtc_request_region(resource_size_t size)
 {
         struct resource *r;
 
         if (RTC_IOMAPPED)
                 r = request_region(RTC_PORT(0), size, "rtc");
         else
                 r = request_mem_region(RTC_PORT(0), size, "rtc");
 
         if (r)
                 rtc_size = size;
 
         return r;
 }
 
 static void rtc_release_region(void)
 {
         if (RTC_IOMAPPED)
                 release_region(RTC_PORT(0), rtc_size);
         else
                 release_mem_region(RTC_PORT(0), rtc_size);
 }
 
 static int __init rtc_init(void)
 {
 #ifdef CONFIG_PROC_FS
         struct proc_dir_entry *ent;
 #endif
 #if defined(__alpha__) || defined(__mips__)
         unsigned int year, ctrl;
         char *guess = NULL;
 #endif
 #ifdef CONFIG_SPARC32
         struct device_node *ebus_dp;
         struct of_device *op;
 #else
         void *r;
 #ifdef RTC_IRQ
         irq_handler_t rtc_int_handler_ptr;
 #endif
 #endif
 
 #ifdef CONFIG_SPARC32
         for_each_node_by_name(ebus_dp, "ebus") {
                 struct device_node *dp;
                 for (dp = ebus_dp; dp; dp = dp->sibling) {
                         if (!strcmp(dp->name, "rtc")) {
                                 op = of_find_device_by_node(dp);
                                 if (op) {
                                         rtc_port = op->resource[0].start;
                                         rtc_irq = op->irqs[0];
                                         goto found;
                                 }
                         }
                 }
         }
         rtc_has_irq = 0;
         printk(KERN_ERR "rtc_init: no PC rtc found\n");
         return -EIO;
 
 found:
         if (!rtc_irq) {
                 rtc_has_irq = 0;
                 goto no_irq;
         }
 
         /*
          * XXX Interrupt pin #7 in Espresso is shared between RTC and
          * PCI Slot 2 INTA# (and some INTx# in Slot 1).
          */
         if (request_irq(rtc_irq, rtc_interrupt, IRQF_SHARED, "rtc",
                         (void *)&rtc_port)) {
                 rtc_has_irq = 0;
                 printk(KERN_ERR "rtc: cannot register IRQ %d\n", rtc_irq);
                 return -EIO;
         }
 no_irq:
 #else
         r = rtc_request_region(RTC_IO_EXTENT);
 
         /*
          * If we've already requested a smaller range (for example, because
          * PNPBIOS or ACPI told us how the device is configured), the request
          * above might fail because it's too big.
          *
          * If so, request just the range we actually use.
          */
         if (!r)
                 r = rtc_request_region(RTC_IO_EXTENT_USED);
         if (!r) {
 #ifdef RTC_IRQ
                 rtc_has_irq = 0;
 #endif
                 printk(KERN_ERR "rtc: I/O resource %lx is not free.\n",
                        (long)(RTC_PORT(0)));
                 return -EIO;
         }
 
 #ifdef RTC_IRQ
         if (is_hpet_enabled()) {
                 int err;
 
                 rtc_int_handler_ptr = hpet_rtc_interrupt;
                 err = hpet_register_irq_handler(rtc_interrupt);
                 if (err != 0) {
                         printk(KERN_WARNING "hpet_register_irq_handler failed "
                                         "in rtc_init().");
                         return err;
                 }
         } else {
                 rtc_int_handler_ptr = rtc_interrupt;
         }
 
         if (request_irq(RTC_IRQ, rtc_int_handler_ptr, IRQF_DISABLED,
                         "rtc", NULL)) {
                 /* Yeah right, seeing as irq 8 doesn't even hit the bus. */
                 rtc_has_irq = 0;
                 printk(KERN_ERR "rtc: IRQ %d is not free.\n", RTC_IRQ);
                 rtc_release_region();
 
                 return -EIO;
         }
         hpet_rtc_timer_init();
 
 #endif
 
 #endif /* CONFIG_SPARC32 vs. others */
 
         if (misc_register(&rtc_dev)) {
 #ifdef RTC_IRQ
                 free_irq(RTC_IRQ, NULL);
                 hpet_unregister_irq_handler(rtc_interrupt);
                 rtc_has_irq = 0;
 #endif
                 rtc_release_region();
                 return -ENODEV;
         }
 
 #ifdef CONFIG_PROC_FS
         ent = proc_create("driver/rtc", 0, NULL, &rtc_proc_fops);
         if (!ent)
                 printk(KERN_WARNING "rtc: Failed to register with procfs.\n");
 #endif
 
 #if defined(__alpha__) || defined(__mips__)
         rtc_freq = HZ;
 
         /* Each operating system on an Alpha uses its own epoch.
            Let's try to guess which one we are using now. */
 
         if (rtc_is_updating() != 0)
                 msleep(20);
 
         spin_lock_irq(&rtc_lock);
         year = CMOS_READ(RTC_YEAR);
         ctrl = CMOS_READ(RTC_CONTROL);
         spin_unlock_irq(&rtc_lock);
 
         if (!(ctrl & RTC_DM_BINARY) || RTC_ALWAYS_BCD)
                 year = bcd2bin(year);       /* This should never happen... */
 
         if (year < 20) {
                 epoch = 2000;
                 guess = "SRM (post-2000)";
         } else if (year >= 20 && year < 48) {
                 epoch = 1980;
                 guess = "ARC console";
         } else if (year >= 48 && year < 72) {
                 epoch = 1952;
                 guess = "Digital UNIX";
 #if defined(__mips__)
         } else if (year >= 72 && year < 74) {
                 epoch = 2000;
                 guess = "Digital DECstation";
 #else
         } else if (year >= 70) {
                 epoch = 1900;
                 guess = "Standard PC (1900)";
 #endif
         }
         if (guess)
                 printk(KERN_INFO "rtc: %s epoch (%lu) detected\n",
                         guess, epoch);
 #endif
 #ifdef RTC_IRQ
         if (rtc_has_irq == 0)
                 goto no_irq2;
 
         spin_lock_irq(&rtc_lock);
         rtc_freq = 1024;
         if (!hpet_set_periodic_freq(rtc_freq)) {
                 /*
                  * Initialize periodic frequency to CMOS reset default,
                  * which is 1024Hz
                  */
                 CMOS_WRITE(((CMOS_READ(RTC_FREQ_SELECT) & 0xF0) | 0x06),
                            RTC_FREQ_SELECT);
         }
         spin_unlock_irq(&rtc_lock);
 no_irq2:
 #endif
 
         (void) init_sysctl();
 
         printk(KERN_INFO "Real Time Clock Driver v" RTC_VERSION "\n");
 
         return 0;
 }
 
 static void __exit rtc_exit(void)
 {
         cleanup_sysctl();
         remove_proc_entry("driver/rtc", NULL);
         misc_deregister(&rtc_dev);
 
 #ifdef CONFIG_SPARC32
         if (rtc_has_irq)
                 free_irq(rtc_irq, &rtc_port);
 #else
         rtc_release_region();
 #ifdef RTC_IRQ
         if (rtc_has_irq) {
                 free_irq(RTC_IRQ, NULL);
                 hpet_unregister_irq_handler(hpet_rtc_interrupt);
         }
 #endif
 #endif /* CONFIG_SPARC32 */
 }
 
 module_init(rtc_init);
 module_exit(rtc_exit);
 
 #ifdef RTC_IRQ
 /*
  *      At IRQ rates >= 4096Hz, an interrupt may get lost altogether.
  *      (usually during an IDE disk interrupt, with IRQ unmasking off)
  *      Since the interrupt handler doesn't get called, the IRQ status
  *      byte doesn't get read, and the RTC stops generating interrupts.
  *      A timer is set, and will call this function if/when that happens.
  *      To get it out of this stalled state, we just read the status.
  *      At least a jiffy of interrupts (rtc_freq/HZ) will have been lost.
  *      (You *really* shouldn't be trying to use a non-realtime system
  *      for something that requires a steady > 1KHz signal anyways.)
  */
 
 static void rtc_dropped_irq(unsigned long data)
 {
         unsigned long freq;
 
         spin_lock_irq(&rtc_lock);
 
         if (hpet_rtc_dropped_irq()) {
                 spin_unlock_irq(&rtc_lock);
                 return;
         }
 
         /* Just in case someone disabled the timer from behind our back... */
         if (rtc_status & RTC_TIMER_ON)
                 mod_timer(&rtc_irq_timer, jiffies + HZ/rtc_freq + 2*HZ/100);
 
         rtc_irq_data += ((rtc_freq/HZ)<<8);
         rtc_irq_data &= ~0xff;
         rtc_irq_data |= (CMOS_READ(RTC_INTR_FLAGS) & 0xF0);     /* restart */
 
         freq = rtc_freq;
 
         spin_unlock_irq(&rtc_lock);
 
         if (printk_ratelimit()) {
                 printk(KERN_WARNING "rtc: lost some interrupts at %ldHz.\n",
                         freq);
         }
 
         /* Now we have new data */
         wake_up_interruptible(&rtc_wait);
 
         kill_fasync(&rtc_async_queue, SIGIO, POLL_IN);
 }
 #endif
 
 #ifdef CONFIG_PROC_FS
 /*
  *      Info exported via "/proc/driver/rtc".
  */
 
 static int rtc_proc_show(struct seq_file *seq, void *v)
 {
 #define YN(bit) ((ctrl & bit) ? "yes" : "no")
 #define NY(bit) ((ctrl & bit) ? "no" : "yes")
         struct rtc_time tm;
         unsigned char batt, ctrl;
         unsigned long freq;
 
         spin_lock_irq(&rtc_lock);
         batt = CMOS_READ(RTC_VALID) & RTC_VRT;
         ctrl = CMOS_READ(RTC_CONTROL);
         freq = rtc_freq;
         spin_unlock_irq(&rtc_lock);
 
 
         rtc_get_rtc_time(&tm);
 
         /*
          * There is no way to tell if the luser has the RTC set for local
          * time or for Universal Standard Time (GMT). Probably local though.
          */
         seq_printf(seq,
                    "rtc_time\t: %02d:%02d:%02d\n"
                    "rtc_date\t: %04d-%02d-%02d\n"
                    "rtc_epoch\t: %04lu\n",
                    tm.tm_hour, tm.tm_min, tm.tm_sec,
                    tm.tm_year + 1900, tm.tm_mon + 1, tm.tm_mday, epoch);
 
         get_rtc_alm_time(&tm);
 
         /*
          * 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.
          */
         seq_puts(seq, "alarm\t\t: ");
         if (tm.tm_hour <= 24)
                 seq_printf(seq, "%02d:", tm.tm_hour);
         else
                 seq_puts(seq, "**:");
 
         if (tm.tm_min <= 59)
                 seq_printf(seq, "%02d:", tm.tm_min);
         else
                 seq_puts(seq, "**:");
 
         if (tm.tm_sec <= 59)
                 seq_printf(seq, "%02d\n", tm.tm_sec);
         else
                 seq_puts(seq, "**\n");
 
         seq_printf(seq,
                    "DST_enable\t: %s\n"
                    "BCD\t\t: %s\n"
                    "24hr\t\t: %s\n"
                    "square_wave\t: %s\n"
                    "alarm_IRQ\t: %s\n"
                    "update_IRQ\t: %s\n"
                    "periodic_IRQ\t: %s\n"
                    "periodic_freq\t: %ld\n"
                    "batt_status\t: %s\n",
                    YN(RTC_DST_EN),
                    NY(RTC_DM_BINARY),
                    YN(RTC_24H),
                    YN(RTC_SQWE),
                    YN(RTC_AIE),
                    YN(RTC_UIE),
                    YN(RTC_PIE),
                    freq,
                    batt ? "okay" : "dead");
 
         return  0;
 #undef YN
 #undef NY
 }
 
 static int rtc_proc_open(struct inode *inode, struct file *file)
 {
         return single_open(file, rtc_proc_show, NULL);
 }
 #endif
 
 static void rtc_get_rtc_time(struct rtc_time *rtc_tm)
 {
         unsigned long uip_watchdog = jiffies, flags;
         unsigned char ctrl;
 #ifdef CONFIG_MACH_DECSTATION
         unsigned int real_year;
 #endif
 
         /*
          * read RTC once any update in progress is done. The update
          * can take just over 2ms. We wait 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.
          */
 
         while (rtc_is_updating() != 0 &&
                time_before(jiffies, uip_watchdog + 2*HZ/100))
                 cpu_relax();
 
         /*
          * Only the values that we read from the RTC are set. We leave
          * tm_wday, tm_yday and tm_isdst untouched. Note that while the
          * RTC has RTC_DAY_OF_WEEK, we should usually ignore it, as it is
          * only updated by the RTC when initially set to a non-zero value.
          */
         spin_lock_irqsave(&rtc_lock, flags);
         rtc_tm->tm_sec = CMOS_READ(RTC_SECONDS);
         rtc_tm->tm_min = CMOS_READ(RTC_MINUTES);
         rtc_tm->tm_hour = CMOS_READ(RTC_HOURS);
         rtc_tm->tm_mday = CMOS_READ(RTC_DAY_OF_MONTH);
         rtc_tm->tm_mon = CMOS_READ(RTC_MONTH);
         rtc_tm->tm_year = CMOS_READ(RTC_YEAR);
         /* Only set from 2.6.16 onwards */
         rtc_tm->tm_wday = CMOS_READ(RTC_DAY_OF_WEEK);
 
 #ifdef CONFIG_MACH_DECSTATION
         real_year = CMOS_READ(RTC_DEC_YEAR);
 #endif
         ctrl = CMOS_READ(RTC_CONTROL);
         spin_unlock_irqrestore(&rtc_lock, flags);
 
         if (!(ctrl & RTC_DM_BINARY) || RTC_ALWAYS_BCD) {
                 rtc_tm->tm_sec = bcd2bin(rtc_tm->tm_sec);
                 rtc_tm->tm_min = bcd2bin(rtc_tm->tm_min);
                 rtc_tm->tm_hour = bcd2bin(rtc_tm->tm_hour);
                 rtc_tm->tm_mday = bcd2bin(rtc_tm->tm_mday);
                 rtc_tm->tm_mon = bcd2bin(rtc_tm->tm_mon);
                 rtc_tm->tm_year = bcd2bin(rtc_tm->tm_year);
                 rtc_tm->tm_wday = bcd2bin(rtc_tm->tm_wday);
         }
 
 #ifdef CONFIG_MACH_DECSTATION
         rtc_tm->tm_year += real_year - 72;
 #endif
 
         /*
          * Account for differences between how the RTC uses the values
          * and how they are defined in a struct rtc_time;
          */
         rtc_tm->tm_year += epoch - 1900;
         if (rtc_tm->tm_year <= 69)
                 rtc_tm->tm_year += 100;
 
         rtc_tm->tm_mon--;
 }
 
 static void get_rtc_alm_time(struct rtc_time *alm_tm)
 {
         unsigned char ctrl;
 
         /*
          * Only the values that we read from the RTC are set. That
          * means only tm_hour, tm_min, and tm_sec.
          */
         spin_lock_irq(&rtc_lock);
         alm_tm->tm_sec = CMOS_READ(RTC_SECONDS_ALARM);
         alm_tm->tm_min = CMOS_READ(RTC_MINUTES_ALARM);
         alm_tm->tm_hour = CMOS_READ(RTC_HOURS_ALARM);
         ctrl = CMOS_READ(RTC_CONTROL);
         spin_unlock_irq(&rtc_lock);
 
         if (!(ctrl & RTC_DM_BINARY) || RTC_ALWAYS_BCD) {
                 alm_tm->tm_sec = bcd2bin(alm_tm->tm_sec);
                 alm_tm->tm_min = bcd2bin(alm_tm->tm_min);
                 alm_tm->tm_hour = bcd2bin(alm_tm->tm_hour);
         }
 }
 
 #ifdef RTC_IRQ
 /*
  * Used to disable/enable interrupts for any one of UIE, AIE, PIE.
  * Rumour has it that if you frob the interrupt enable/disable
  * bits in RTC_CONTROL, you should read RTC_INTR_FLAGS, to
  * ensure you actually start getting interrupts. Probably for
  * compatibility with older/broken chipset RTC implementations.
  * We also clear out any old irq data after an ioctl() that
  * meddles with the interrupt enable/disable bits.
  */
 
 static void mask_rtc_irq_bit_locked(unsigned char bit)
 {
         unsigned char val;
 
         if (hpet_mask_rtc_irq_bit(bit))
                 return;
         val = CMOS_READ(RTC_CONTROL);
         val &=  ~bit;
         CMOS_WRITE(val, RTC_CONTROL);
         CMOS_READ(RTC_INTR_FLAGS);
 
         rtc_irq_data = 0;
 }
 
 static void set_rtc_irq_bit_locked(unsigned char bit)
 {
         unsigned char val;
 
         if (hpet_set_rtc_irq_bit(bit))
                 return;
         val = CMOS_READ(RTC_CONTROL);
         val |= bit;
         CMOS_WRITE(val, RTC_CONTROL);
         CMOS_READ(RTC_INTR_FLAGS);
 
         rtc_irq_data = 0;
 }
 #endif
 
 MODULE_AUTHOR("Paul Gortmaker");
 MODULE_LICENSE("GPL");
 MODULE_ALIAS_MISCDEV(RTC_MINOR);
 

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