rtc.c

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/*
 *	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.
 */

#define RTC_VERSION		"1.10e"

#define RTC_IO_EXTENT	0x10	/* Only really two ports, but...	*/

/*
 *	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/config.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/spinlock.h>

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

#ifdef __sparc__
#include <asm/ebus.h>
#ifdef __sparc_v9__
#include <asm/isa.h>
#endif

static unsigned long rtc_port;
static int rtc_irq = PCI_IRQ_NONE;
#endif

static int rtc_has_irq = 1;

/*
 *	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);

static struct timer_list rtc_irq_timer;

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

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

#if RTC_IRQ
static unsigned int rtc_poll(struct file *file, poll_table *wait);
#endif

static void get_rtc_time (struct rtc_time *rtc_tm);
static void get_rtc_alm_time (struct rtc_time *alm_tm);
#if RTC_IRQ
static void rtc_dropped_irq(unsigned long data);

static void set_rtc_irq_bit(unsigned char bit);
static void mask_rtc_irq_bit(unsigned char bit);
#endif

static inline unsigned char rtc_is_updating(void);

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

/*
 *	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 big kernel 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 = 0;	/* bitmapped status byte.	*/
static unsigned long rtc_freq = 0;	/* Current periodic IRQ rate	*/
static unsigned long rtc_irq_data = 0;	/* our output to the world	*/

/*
 *	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};

#if RTC_IRQ
/*
 *	A very tiny interrupt handler. It runs with SA_INTERRUPT 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 serializes
 *	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 void rtc_interrupt(int irq, void *dev_id, struct pt_regs *regs)
{
	/*
	 *	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;
	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 */
	wake_up_interruptible(&rtc_wait);	

	kill_fasync (&rtc_async_queue, SIGIO, POLL_IN);
}
#endif

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

static ssize_t rtc_read(struct file *file, char *buf,
			size_t count, loff_t *ppos)
{
#if !RTC_IRQ
	return -EIO;
#else
	DECLARE_WAITQUEUE(wait, current);
	unsigned long data;
	ssize_t retval;
	
	if (rtc_has_irq == 0)
		return -EIO;

	if (count < sizeof(unsigned long))
		return -EINVAL;

	add_wait_queue(&rtc_wait, &wait);

	current->state = TASK_INTERRUPTIBLE;
		
	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. */
		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);

	retval = put_user(data, (unsigned long *)buf); 
	if (!retval)
		retval = sizeof(unsigned long); 
 out:
	current->state = TASK_RUNNING;
	remove_wait_queue(&rtc_wait, &wait);

	return retval;
#endif
}

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

#if 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) {
#if 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	*/
	{
		mask_rtc_irq_bit(RTC_PIE);
		if (rtc_status & RTC_TIMER_ON) {
			spin_lock_irq (&rtc_lock);
			rtc_status &= ~RTC_TIMER_ON;
			del_timer(&rtc_irq_timer);
			spin_unlock_irq (&rtc_lock);
		}
		return 0;
	}
	case RTC_PIE_ON:	/* Allow periodic ints		*/
	{

		/*
		 * We don't really want Joe User enabling more
		 * than 64Hz of interrupts on a multi-user machine.
		 */
		if ((rtc_freq > 64) && (!capable(CAP_SYS_RESOURCE)))
			return -EACCES;

		if (!(rtc_status & RTC_TIMER_ON)) {
			spin_lock_irq (&rtc_lock);
			rtc_irq_timer.expires = jiffies + HZ/rtc_freq + 2*HZ/100;
			add_timer(&rtc_irq_timer);
			rtc_status |= RTC_TIMER_ON;
			spin_unlock_irq (&rtc_lock);
		}
		set_rtc_irq_bit(RTC_PIE);
		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.
		 */

		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*)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 >= 60)
			sec = 0xff;

		spin_lock_irq(&rtc_lock);
		if (!(CMOS_READ(RTC_CONTROL) & RTC_DM_BINARY) ||
		    RTC_ALWAYS_BCD)
		{
			BIN_TO_BCD(sec);
			BIN_TO_BCD(min);
			BIN_TO_BCD(hrs);
		}
		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	*/
	{
		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_DECSTATION
		unsigned int real_yrs;
#endif

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

		if (copy_from_user(&rtc_tm, (struct rtc_time*)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;

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

		spin_lock_irq(&rtc_lock);
#ifdef CONFIG_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 independant 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) {
			BIN_TO_BCD(sec);
			BIN_TO_BCD(min);
			BIN_TO_BCD(hrs);
			BIN_TO_BCD(day);
			BIN_TO_BCD(mon);
			BIN_TO_BCD(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_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;
	}
#if RTC_IRQ
	case RTC_IRQP_READ:	/* Read the periodic IRQ rate.	*/
	{
		return put_user(rtc_freq, (unsigned long *)arg);
	}
	case RTC_IRQP_SET:	/* Set periodic IRQ rate.	*/
	{
		int tmp = 0;
		unsigned char val;

		/* 
		 * 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 ((arg > 64) && (!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;

		spin_lock_irq(&rtc_lock);
		rtc_freq = arg;

		val = CMOS_READ(RTC_FREQ_SELECT) & 0xf0;
		val |= (16 - tmp);
		CMOS_WRITE(val, RTC_FREQ_SELECT);
		spin_unlock_irq(&rtc_lock);
		return 0;
	}
#endif
	case RTC_EPOCH_READ:	/* Read the epoch.	*/
	{
		return put_user (epoch, (unsigned long *)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 -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.
 */

/* We use rtc_lock to protect against concurrent opens. So the BKL is not
 * needed here. Or anywhere else in this driver. */
static int rtc_open(struct inode *inode, struct file *file)
{
	spin_lock_irq (&rtc_lock);

	if(rtc_status & RTC_IS_OPEN)