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