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.
 *	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
 */

#define RTC_VERSION		"1.12ac"

/*
 *	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/sysctl.h>
#include <linux/wait.h>
#include <linux/bcd.h>
#include <linux/delay.h>

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

#ifdef CONFIG_X86
#include <asm/hpet.h>
#endif

#ifdef CONFIG_SPARC32
#include <linux/pci.h>
#include <asm/ebus.h>

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

#ifdef	CONFIG_HPET_RTC_IRQ
#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
#ifdef RTC_IRQ
static irqreturn_t hpet_rtc_interrupt(int irq, void *dev_id)
{
	return 0;
}
#endif
#else
extern irqreturn_t hpet_rtc_interrupt(int irq, void *dev_id);
#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 int rtc_ioctl(struct inode *inode, struct file *file,
		     unsigned int cmd, unsigned long arg);

#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 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	*/
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 = NULL;
#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.)
 */

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	*/
	{
		unsigned long flags; /* can be called from isr via rtc_control() */
		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		*/
	{
		unsigned long flags; /* can be called from isr via rtc_control() */
		/*
		 * 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);