drivers/char/mips_rtc.c

/*
 *	A simple generic Real Time Clock interface for Linux/MIPS
 *
 *	Copyright (C) 1996 Paul Gortmaker
 *
 *	Copyright (C) 2001 Monta Vista Software
 *	Author Jun Sun, jsun@mvista.com or jsun@junsun.net
 *
 *	This is a simple generic RTC driver for MIPS boards configured 
 *	with CONFIG_NEW_TIME_C.  For now, it makes use of the two
 *	abstract kernel RTC functions introduced in include/asm-mips/time.h:
 *
 *		extern unsigned long (*rtc_get_time)(void);
 *		extern int (*rtc_set_time)(unsigned long);
 *
 *	It uses the same protocol as the original drivers/char/rtc.c driver,
 *	but only implements two ioctls: RTC_RD_TIME and RTC_SET_TIME.
 *
 * 	TODO :
 *
 * 	1. we can extend the null rtc ops defined in arch/mips/time.c to
 * 	   at least record the elapsed time (by recording/checking jiffies)
 * 	   This way RTC_RD_TIME and RTC_SET_TIME will make more sense.
 * 	   (Maybe not.  A machine without a real RTC is broken anymore.
 * 	   Just a thought.)
 *
 * 	2. If we make use of timer bh, we can emulate many RTC functions
 * 	   such as RTC alarm interrupt, periodic interrupts, etc.
 *
 * 	3. It is possible to extend the kernel RTC abstractions to more
 * 	   than two functions, so that perhaps we can implement more
 * 	   full-featured RTC driver and also have a better abstraction
 * 	   to support more RTC hardware than the original RTC driver.
 * 	   It needs to be done very carefully.
 *
 * Change Log :
 * 	v1.0	- [jsun] initial version
 */

#define RTC_VERSION		"1.0"

#include <linux/config.h>
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/types.h>
#include <linux/miscdevice.h>
#include <linux/fcntl.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>

/*
 * Check machine
 */
#if !defined(CONFIG_MIPS) || !defined(CONFIG_NEW_TIME_C)
#error "This driver is for MIPS machines with CONFIG_NEW_TIME_C defined"
#endif

#include <asm/time.h>

static unsigned long rtc_status = 0;	/* bitmapped status byte.       */

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


#define RTC_IS_OPEN             0x01	/* means /dev/rtc is in use     */

static spinlock_t rtc_lock;

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

	switch (cmd) {
	case RTC_RD_TIME:	/* Read the time/date from RTC  */
		memset(&rtc_tm, 0, sizeof(struct rtc_time));
		curr_time = rtc_get_time();
		to_tm(curr_time, &rtc_tm);
		rtc_tm.tm_year -= 1900;
		return copy_to_user((void *) arg, &rtc_tm, sizeof(rtc_tm)) ? 
			-EFAULT : 0;
	case RTC_SET_TIME:	/* Set the RTC */
		if (!capable(CAP_SYS_TIME))
			return -EACCES;

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

		curr_time = mktime(rtc_tm.tm_year + 1900,
				   rtc_tm.tm_mon + 1, /* tm_mon starts from 0 */
				   rtc_tm.tm_mday,
				   rtc_tm.tm_hour,
				   rtc_tm.tm_min, 
				   rtc_tm.tm_sec);
		return rtc_set_time(curr_time);
	default:
		return -EINVAL;
	}
}

/* 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) {
		spin_unlock_irq(&rtc_lock);
		return -EBUSY;
	}

	rtc_status |= RTC_IS_OPEN;

	spin_unlock_irq(&rtc_lock);
	return 0;
}

static int rtc_release(struct inode *inode, struct file *file)
{
	spin_lock_irq(&rtc_lock);
	rtc_status &= ~RTC_IS_OPEN;
	spin_unlock_irq(&rtc_lock);
	return 0;
}

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

static struct file_operations rtc_fops = {
	owner:THIS_MODULE,
	llseek:no_llseek,
	ioctl:rtc_ioctl,
	open:rtc_open,
	release:rtc_release,
};

static struct miscdevice rtc_dev = {
	RTC_MINOR,
	"rtc",
	&rtc_fops
};

static int __init rtc_init(void)
{

	misc_register(&rtc_dev);
	create_proc_read_entry("driver/rtc", 0, 0, rtc_read_proc, NULL);

	printk(KERN_INFO "Generic MIPS RTC Driver v" RTC_VERSION "\n");

	return 0;
}

static void __exit rtc_exit(void)
{
	remove_proc_entry("driver/rtc", NULL);
	misc_deregister(&rtc_dev);

}

module_init(rtc_init);
module_exit(rtc_exit);
EXPORT_NO_SYMBOLS;

/*
 *	Info exported via "/proc/driver/rtc".
 */

static int rtc_proc_output(char *buf)
{
	char *p;
	struct rtc_time tm;
	unsigned long curr_time;

	curr_time = rtc_get_time();
	to_tm(curr_time, &tm);

	p = buf;

	/*
	 * 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.
	 */
	p += sprintf(p,
		     "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, tm.tm_mon + 1, tm.tm_mday, 0L);

	return p - buf;
}

static int rtc_read_proc(char *page, char **start, off_t off,
			 int count, int *eof, void *data)
{
	int len = rtc_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;
}

MODULE_AUTHOR("Jun Sun");
MODULE_LICENSE("GPL");