/*
* Copyright 2008 by Andreas Eversberg <andreas@eversberg.eu>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* Quick API description:
*
* A clock source registers using mISDN_register_clock:
* name = text string to name clock source
* priority = value to priorize clock sources (0 = default)
* ctl = callback function to enable/disable clock source
* priv = private pointer of clock source
* return = pointer to clock source structure;
*
* Note: Callback 'ctl' can be called before mISDN_register_clock returns!
* Also it can be called during mISDN_unregister_clock.
*
* A clock source calls mISDN_clock_update with given samples elapsed, if
* enabled. If function call is delayed, tv must be set with the timestamp
* of the actual event.
*
* A clock source unregisters using mISDN_unregister_clock.
*
* To get current clock, call mISDN_clock_get. The signed short value
* counts the number of samples since. Time since last clock event is added.
*
*/
#include <linux/types.h>
#include <linux/stddef.h>
#include <linux/spinlock.h>
#include <linux/mISDNif.h>
#include "core.h"
static u_int *debug;
static LIST_HEAD(iclock_list);
static DEFINE_RWLOCK(iclock_lock);
static u16 iclock_count; /* counter of last clock */
static struct timeval iclock_tv; /* time stamp of last clock */
static int iclock_tv_valid; /* already received one timestamp */
static struct mISDNclock *iclock_current;
void
mISDN_init_clock(u_int *dp)
{
debug = dp;
do_gettimeofday(&iclock_tv);
}
static void
select_iclock(void)
{
struct mISDNclock *iclock, *bestclock = NULL, *lastclock = NULL;
int pri = -128;
list_for_each_entry(iclock, &iclock_list, list) {
if (iclock->pri > pri) {
pri = iclock->pri;
bestclock = iclock;
}
if (iclock_current == iclock)
lastclock = iclock;
}
if (lastclock && bestclock != lastclock) {
/* last used clock source still exists but changes, disable */
if (*debug & DEBUG_CLOCK)
printk(KERN_DEBUG "Old clock source '%s' disable.\n",
lastclock->name);
lastclock->ctl(lastclock->priv, 0);
}
if (bestclock && bestclock != iclock_current) {
/* new clock source selected, enable */
if (*debug & DEBUG_CLOCK)
printk(KERN_DEBUG "New clock source '%s' enable.\n",
bestclock->name);
bestclock->ctl(bestclock->priv, 1);
}
if (bestclock != iclock_current) {
/* no clock received yet */
iclock_tv_valid = 0;
}
iclock_current = bestclock;
}
struct mISDNclock
*mISDN_register_clock(char *name, int pri, clockctl_func_t *ctl, void *priv)
{
u_long flags;
struct mISDNclock *iclock;
if (*debug & (DEBUG_CORE | DEBUG_CLOCK))
printk(KERN_DEBUG "%s: %s %d\n", __func__, name, pri);
iclock = kzalloc(sizeof(struct mISDNclock), GFP_ATOMIC);
if (!iclock) {
printk(KERN_ERR "%s: No memory for clock entry.\n", __func__);
return NULL;
}
strncpy(iclock->name, name, sizeof(iclock->name)-1);
iclock->pri = pri;
iclock->priv = priv;
iclock->ctl = ctl;
write_lock_irqsave(&iclock_lock, flags);
list_add_tail(&iclock->list, &iclock_list);
select_iclock();
write_unlock_irqrestore(&iclock_lock, flags);
return iclock;
}
EXPORT_SYMBOL(mISDN_register_clock);
void
mISDN_unregister_clock(struct mISDNclock *iclock)
{
u_long flags;
if (*debug & (DEBUG_CORE | DEBUG_CLOCK))
printk(KERN_DEBUG "%s: %s %d\n", __func__, iclock->name,
iclock->pri);
write_lock_irqsave(&iclock_lock, flags);
if (iclock_current == iclock) {
if (*debug & DEBUG_CLOCK)
printk(KERN_DEBUG
"Current clock source '%s' unregisters.\n",
iclock->name);
iclock->ctl(iclock->priv, 0);
}
list_del(&iclock->list);
select_iclock();
write_unlock_irqrestore(&iclock_lock, flags);
}
EXPORT_SYMBOL(mISDN_unregister_clock);
void
mISDN_clock_update(struct mISDNclock *iclock, int samples, struct timeval *tv)
{
u_long flags;
struct timeval tv_now;
time_t elapsed_sec;
int elapsed_8000th;
write_lock_irqsave(&iclock_lock, flags);
if (iclock_current != iclock) {
printk(KERN_ERR "%s: '%s' sends us clock updates, but we do "
"listen to '%s'. This is a bug!\n", __func__,
iclock->name,
iclock_current ? iclock_current->name : "nothing");
iclock->ctl(iclock->priv, 0);
write_unlock_irqrestore(&iclock_lock, flags);
return;
}
if (iclock_tv_valid) {
/* increment sample counter by given samples */
iclock_count += samples;
if (tv) { /* tv must be set, if function call is delayed */
iclock_tv.tv_sec = tv->tv_sec;
iclock_tv.tv_usec = tv->tv_usec;
} else
do_gettimeofday(&iclock_tv);
} else {
/* calc elapsed time by system clock */
if (tv) { /* tv must be set, if function call is delayed */
tv_now.tv_sec = tv->tv_sec;
tv_now.tv_usec = tv->tv_usec;
} else
do_gettimeofday(&tv_now);
elapsed_sec = tv_now.tv_sec - iclock_tv.tv_sec;
elapsed_8000th = (tv_now.tv_usec / 125)
- (iclock_tv.tv_usec / 125);
if (elapsed_8000th < 0) {
elapsed_sec -= 1;
elapsed_8000th += 8000;
}
/* add elapsed time to counter and set new timestamp */
iclock_count += elapsed_sec * 8000 + elapsed_8000th;
iclock_tv.tv_sec = tv_now.tv_sec;
iclock_tv.tv_usec = tv_now.tv_usec;
iclock_tv_valid = 1;
if (*debug & DEBUG_CLOCK)
printk("Received first clock from source '%s'.\n",
iclock_current ? iclock_current->name : "nothing");
}
write_unlock_irqrestore(&iclock_lock, flags);
}
EXPORT_SYMBOL(mISDN_clock_update);
unsigned short
mISDN_clock_get(void)
{
u_long flags;
struct timeval tv_now;
time_t elapsed_sec;
int elapsed_8000th;
u16 count;
read_lock_irqsave(&iclock_lock, flags);
/* calc elapsed time by system clock */
do_gettimeofday(&tv_now);
elapsed_sec = tv_now.tv_sec - iclock_tv.tv_sec;
elapsed_8000th = (tv_now.tv_usec / 125) - (iclock_tv.tv_usec / 125);
if (elapsed_8000th < 0) {
elapsed_sec -= 1;
elapsed_8000th += 8000;
}
/* add elapsed time to counter */
count = iclock_count + elapsed_sec * 8000 + elapsed_8000th;
read_unlock_irqrestore(&iclock_lock, flags);
return count;
}
EXPORT_SYMBOL(mISDN_clock_get);
