linux/drivers/isdn/mISDN/clock.c
Thomas Gleixner 1802d0beec treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 174
Based on 1 normalized pattern(s):

  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

extracted by the scancode license scanner the SPDX license identifier

  GPL-2.0-only

has been chosen to replace the boilerplate/reference in 655 file(s).

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Allison Randal <allison@lohutok.net>
Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org>
Reviewed-by: Richard Fontana <rfontana@redhat.com>
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190527070034.575739538@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2019-05-30 11:26:41 -07:00

198 lines
5.6 KiB
C

// SPDX-License-Identifier: GPL-2.0-only
/*
* Copyright 2008 by Andreas Eversberg <andreas@eversberg.eu>
*
* 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/slab.h>
#include <linux/types.h>
#include <linux/stddef.h>
#include <linux/spinlock.h>
#include <linux/ktime.h>
#include <linux/mISDNif.h>
#include <linux/export.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 ktime_t iclock_timestamp; /* time stamp of last clock */
static int iclock_timestamp_valid; /* already received one timestamp */
static struct mISDNclock *iclock_current;
void
mISDN_init_clock(u_int *dp)
{
debug = dp;
iclock_timestamp = ktime_get();
}
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_timestamp_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, ktime_t *timestamp)
{
u_long flags;
ktime_t timestamp_now;
u16 delta;
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_timestamp_valid) {
/* increment sample counter by given samples */
iclock_count += samples;
if (timestamp) { /* timestamp must be set, if function call is delayed */
iclock_timestamp = *timestamp;
} else {
iclock_timestamp = ktime_get();
}
} else {
/* calc elapsed time by system clock */
if (timestamp) { /* timestamp must be set, if function call is delayed */
timestamp_now = *timestamp;
} else {
timestamp_now = ktime_get();
}
delta = ktime_divns(ktime_sub(timestamp_now, iclock_timestamp),
(NSEC_PER_SEC / 8000));
/* add elapsed time to counter and set new timestamp */
iclock_count += delta;
iclock_timestamp = timestamp_now;
iclock_timestamp_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;
ktime_t timestamp_now;
u16 delta;
u16 count;
read_lock_irqsave(&iclock_lock, flags);
/* calc elapsed time by system clock */
timestamp_now = ktime_get();
delta = ktime_divns(ktime_sub(timestamp_now, iclock_timestamp),
(NSEC_PER_SEC / 8000));
/* add elapsed time to counter */
count = iclock_count + delta;
read_unlock_irqrestore(&iclock_lock, flags);
return count;
}
EXPORT_SYMBOL(mISDN_clock_get);