smttimer.c

这个linux源代码是很全面的~基本完整了~使用c编译的~由于时间问题我没有亲自测试~但就算用来做参考资料也是非常好的

/******************************************************************************
 *
 *	(C)Copyright 1998,1999 SysKonnect,
 *	a business unit of Schneider & Koch & Co. Datensysteme GmbH.
 *
 *	See the file "skfddi.c" for further information.
 *
 *	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.
 *
 *	The information in this file is provided "AS IS" without warranty.
 *
 ******************************************************************************/

/*
	SMT timer
*/

#include "h/types.h"
#include "h/fddi.h"
#include "h/smc.h"

#ifndef	lint
static const char ID_sccs[] = "@(#)smttimer.c	2.4 97/08/04 (C) SK " ;
#endif

/*
 * external function declarations
 */
extern u_long hwt_read() ;
extern void hwt_stop() ;
extern void hwt_start() ;

static void timer_done() ;


void smt_timer_init(smc)
struct s_smc *smc ;
{
	smc->t.st_queue = 0 ;
	smc->t.st_fast.tm_active = FALSE ;
	smc->t.st_fast.tm_next = 0 ;
	hwt_init(smc) ;
}

void smt_timer_stop(smc,timer)
struct s_smc *smc ;
struct smt_timer *timer ;
{
	struct smt_timer	**prev ;
	struct smt_timer	*tm ;

	/*
	 * remove timer from queue
	 */
	timer->tm_active = FALSE ;
	if (smc->t.st_queue == timer && !timer->tm_next) {
		hwt_stop(smc) ;
	}
	for (prev = &smc->t.st_queue ; (tm = *prev) ; prev = &tm->tm_next ) {
		if (tm == timer) {
			*prev = tm->tm_next ;
			if (tm->tm_next) {
				tm->tm_next->tm_delta += tm->tm_delta ;
			}
			return ;
		}
	}
}

void smt_timer_start(smc,timer,time,token)
struct s_smc *smc ;
struct smt_timer *timer ;
u_long		time ;
u_long		token ;
{
	struct smt_timer	**prev ;
	struct smt_timer	*tm ;
	u_long			delta = 0 ;

	time /= 16 ;		/* input is uS, clock ticks are 16uS */
	if (!time)
		time = 1 ;
	smt_timer_stop(smc,timer) ;
	timer->tm_smc = smc ;
	timer->tm_token = token ;
	timer->tm_active = TRUE ;
	if (!smc->t.st_queue) {
		smc->t.st_queue = timer ;
		timer->tm_next = 0 ;
		timer->tm_delta = time ;
		hwt_start(smc,time) ;
		return ;
	}
	/*
	 * timer correction
	 */
	timer_done(smc,0) ;

	/*
	 * find position in queue
	 */
	delta = 0 ;
	for (prev = &smc->t.st_queue ; (tm = *prev) ; prev = &tm->tm_next ) {
		if (delta + tm->tm_delta > time) {
			break ;
		}
		delta += tm->tm_delta ;
	}
	/* insert in queue */
	*prev = timer ;
	timer->tm_next = tm ;
	timer->tm_delta = time - delta ;
	if (tm)
		tm->tm_delta -= timer->tm_delta ;
	/*
	 * start new with first
	 */
	hwt_start(smc,smc->t.st_queue->tm_delta) ;
}

void smt_force_irq(smc)
struct s_smc *smc ;
{
	smt_timer_start(smc,&smc->t.st_fast,32L, EV_TOKEN(EVENT_SMT,SM_FAST)); 
}

void smt_timer_done(smc)
struct s_smc *smc ;
{
	timer_done(smc,1) ;
}

static void timer_done(smc,restart)
struct s_smc *smc ;
int restart ;
{
	u_long			delta ;
	struct smt_timer	*tm ;
	struct smt_timer	*next ;
	struct smt_timer	**last ;
	int			done = 0 ;

	delta = hwt_read(smc) ;
	last = &smc->t.st_queue ;
	tm = smc->t.st_queue ;
	while (tm && !done) {
		if (delta >= tm->tm_delta) {
			tm->tm_active = FALSE ;
			delta -= tm->tm_delta ;
			last = &tm->tm_next ;
			tm = tm->tm_next ;
		}
		else {
			tm->tm_delta -= delta ;
			delta = 0 ;
			done = 1 ;
		}
	}
	*last = 0 ;
	next = smc->t.st_queue ;
	smc->t.st_queue = tm ;

	for ( tm = next ; tm ; tm = next) {
		next = tm->tm_next ;
		timer_event(smc,tm->tm_token) ;
	}

	if (restart && smc->t.st_queue)
		hwt_start(smc,smc->t.st_queue->tm_delta) ;
}