timer.c

linux 内核源代码

			if (timer->flags & SNDRV_TIMER_FLG_CHANGE) {
				timer->flags &= ~SNDRV_TIMER_FLG_CHANGE;
				timer->hw.start(timer);
			}
		}
	}
	if (!keep_flag)
		timeri->flags &=
			~(SNDRV_TIMER_IFLG_RUNNING | SNDRV_TIMER_IFLG_START);
	spin_unlock_irqrestore(&timer->lock, flags);
      __end:
	if (event != SNDRV_TIMER_EVENT_RESOLUTION)
		snd_timer_notify1(timeri, event);
	return 0;
}

/*
 * stop the timer instance.
 *
 * do not call this from the timer callback!
 */
int snd_timer_stop(struct snd_timer_instance *timeri)
{
	struct snd_timer *timer;
	unsigned long flags;
	int err;

	err = _snd_timer_stop(timeri, 0, SNDRV_TIMER_EVENT_STOP);
	if (err < 0)
		return err;
	timer = timeri->timer;
	spin_lock_irqsave(&timer->lock, flags);
	timeri->cticks = timeri->ticks;
	timeri->pticks = 0;
	spin_unlock_irqrestore(&timer->lock, flags);
	return 0;
}

/*
 * start again..  the tick is kept.
 */
int snd_timer_continue(struct snd_timer_instance *timeri)
{
	struct snd_timer *timer;
	int result = -EINVAL;
	unsigned long flags;

	if (timeri == NULL)
		return result;
	if (timeri->flags & SNDRV_TIMER_IFLG_SLAVE)
		return snd_timer_start_slave(timeri);
	timer = timeri->timer;
	if (! timer)
		return -EINVAL;
	spin_lock_irqsave(&timer->lock, flags);
	if (!timeri->cticks)
		timeri->cticks = 1;
	timeri->pticks = 0;
	result = snd_timer_start1(timer, timeri, timer->sticks);
	spin_unlock_irqrestore(&timer->lock, flags);
	snd_timer_notify1(timeri, SNDRV_TIMER_EVENT_CONTINUE);
	return result;
}

/*
 * pause.. remember the ticks left
 */
int snd_timer_pause(struct snd_timer_instance * timeri)
{
	return _snd_timer_stop(timeri, 0, SNDRV_TIMER_EVENT_PAUSE);
}

/*
 * reschedule the timer
 *
 * start pending instances and check the scheduling ticks.
 * when the scheduling ticks is changed set CHANGE flag to reprogram the timer.
 */
static void snd_timer_reschedule(struct snd_timer * timer, unsigned long ticks_left)
{
	struct snd_timer_instance *ti;
	unsigned long ticks = ~0UL;

	list_for_each_entry(ti, &timer->active_list_head, active_list) {
		if (ti->flags & SNDRV_TIMER_IFLG_START) {
			ti->flags &= ~SNDRV_TIMER_IFLG_START;
			ti->flags |= SNDRV_TIMER_IFLG_RUNNING;
			timer->running++;
		}
		if (ti->flags & SNDRV_TIMER_IFLG_RUNNING) {
			if (ticks > ti->cticks)
				ticks = ti->cticks;
		}
	}
	if (ticks == ~0UL) {
		timer->flags &= ~SNDRV_TIMER_FLG_RESCHED;
		return;
	}
	if (ticks > timer->hw.ticks)
		ticks = timer->hw.ticks;
	if (ticks_left != ticks)
		timer->flags |= SNDRV_TIMER_FLG_CHANGE;
	timer->sticks = ticks;
}

/*
 * timer tasklet
 *
 */
static void snd_timer_tasklet(unsigned long arg)
{
	struct snd_timer *timer = (struct snd_timer *) arg;
	struct snd_timer_instance *ti;
	struct list_head *p;
	unsigned long resolution, ticks;
	unsigned long flags;

	spin_lock_irqsave(&timer->lock, flags);
	/* now process all callbacks */
	while (!list_empty(&timer->sack_list_head)) {
		p = timer->sack_list_head.next;		/* get first item */
		ti = list_entry(p, struct snd_timer_instance, ack_list);

		/* remove from ack_list and make empty */
		list_del_init(p);

		ticks = ti->pticks;
		ti->pticks = 0;
		resolution = ti->resolution;

		ti->flags |= SNDRV_TIMER_IFLG_CALLBACK;
		spin_unlock(&timer->lock);
		if (ti->callback)
			ti->callback(ti, resolution, ticks);
		spin_lock(&timer->lock);
		ti->flags &= ~SNDRV_TIMER_IFLG_CALLBACK;
	}
	spin_unlock_irqrestore(&timer->lock, flags);
}

/*
 * timer interrupt
 *
 * ticks_left is usually equal to timer->sticks.
 *
 */
void snd_timer_interrupt(struct snd_timer * timer, unsigned long ticks_left)
{
	struct snd_timer_instance *ti, *ts, *tmp;
	unsigned long resolution, ticks;
	struct list_head *p, *ack_list_head;
	unsigned long flags;
	int use_tasklet = 0;

	if (timer == NULL)
		return;

	spin_lock_irqsave(&timer->lock, flags);

	/* remember the current resolution */
	if (timer->hw.c_resolution)
		resolution = timer->hw.c_resolution(timer);
	else
		resolution = timer->hw.resolution;

	/* loop for all active instances
	 * Here we cannot use list_for_each_entry because the active_list of a
	 * processed instance is relinked to done_list_head before the callback
	 * is called.
	 */
	list_for_each_entry_safe(ti, tmp, &timer->active_list_head,
				 active_list) {
		if (!(ti->flags & SNDRV_TIMER_IFLG_RUNNING))
			continue;
		ti->pticks += ticks_left;
		ti->resolution = resolution;
		if (ti->cticks < ticks_left)
			ti->cticks = 0;
		else
			ti->cticks -= ticks_left;
		if (ti->cticks) /* not expired */
			continue;
		if (ti->flags & SNDRV_TIMER_IFLG_AUTO) {
			ti->cticks = ti->ticks;
		} else {
			ti->flags &= ~SNDRV_TIMER_IFLG_RUNNING;
			if (--timer->running)
				list_del(&ti->active_list);
		}
		if ((timer->hw.flags & SNDRV_TIMER_HW_TASKLET) ||
		    (ti->flags & SNDRV_TIMER_IFLG_FAST))
			ack_list_head = &timer->ack_list_head;
		else
			ack_list_head = &timer->sack_list_head;
		if (list_empty(&ti->ack_list))
			list_add_tail(&ti->ack_list, ack_list_head);
		list_for_each_entry(ts, &ti->slave_active_head, active_list) {
			ts->pticks = ti->pticks;
			ts->resolution = resolution;
			if (list_empty(&ts->ack_list))
				list_add_tail(&ts->ack_list, ack_list_head);
		}
	}
	if (timer->flags & SNDRV_TIMER_FLG_RESCHED)
		snd_timer_reschedule(timer, timer->sticks);
	if (timer->running) {
		if (timer->hw.flags & SNDRV_TIMER_HW_STOP) {
			timer->hw.stop(timer);
			timer->flags |= SNDRV_TIMER_FLG_CHANGE;
		}
		if (!(timer->hw.flags & SNDRV_TIMER_HW_AUTO) ||
		    (timer->flags & SNDRV_TIMER_FLG_CHANGE)) {
			/* restart timer */
			timer->flags &= ~SNDRV_TIMER_FLG_CHANGE;
			timer->hw.start(timer);
		}
	} else {
		timer->hw.stop(timer);
	}

	/* now process all fast callbacks */
	while (!list_empty(&timer->ack_list_head)) {
		p = timer->ack_list_head.next;		/* get first item */
		ti = list_entry(p, struct snd_timer_instance, ack_list);

		/* remove from ack_list and make empty */
		list_del_init(p);

		ticks = ti->pticks;
		ti->pticks = 0;

		ti->flags |= SNDRV_TIMER_IFLG_CALLBACK;
		spin_unlock(&timer->lock);
		if (ti->callback)
			ti->callback(ti, resolution, ticks);
		spin_lock(&timer->lock);
		ti->flags &= ~SNDRV_TIMER_IFLG_CALLBACK;
	}

	/* do we have any slow callbacks? */
	use_tasklet = !list_empty(&timer->sack_list_head);
	spin_unlock_irqrestore(&timer->lock, flags);

	if (use_tasklet)
		tasklet_hi_schedule(&timer->task_queue);
}

/*

 */

int snd_timer_new(struct snd_card *card, char *id, struct snd_timer_id *tid,
		  struct snd_timer **rtimer)
{
	struct snd_timer *timer;
	int err;
	static struct snd_device_ops ops = {
		.dev_free = snd_timer_dev_free,
		.dev_register = snd_timer_dev_register,
		.dev_disconnect = snd_timer_dev_disconnect,
	};

	snd_assert(tid != NULL, return -EINVAL);
	snd_assert(rtimer != NULL, return -EINVAL);
	*rtimer = NULL;
	timer = kzalloc(sizeof(*timer), GFP_KERNEL);
	if (timer == NULL) {
		snd_printk(KERN_ERR "timer: cannot allocate\n");
		return -ENOMEM;
	}
	timer->tmr_class = tid->dev_class;
	timer->card = card;
	timer->tmr_device = tid->device;
	timer->tmr_subdevice = tid->subdevice;
	if (id)
		strlcpy(timer->id, id, sizeof(timer->id));
	INIT_LIST_HEAD(&timer->device_list);
	INIT_LIST_HEAD(&timer->open_list_head);
	INIT_LIST_HEAD(&timer->active_list_head);
	INIT_LIST_HEAD(&timer->ack_list_head);
	INIT_LIST_HEAD(&timer->sack_list_head);
	spin_lock_init(&timer->lock);
	tasklet_init(&timer->task_queue, snd_timer_tasklet,
		     (unsigned long)timer);
	if (card != NULL) {
		timer->module = card->module;
		err = snd_device_new(card, SNDRV_DEV_TIMER, timer, &ops);
		if (err < 0) {
			snd_timer_free(timer);
			return err;
		}
	}
	*rtimer = timer;
	return 0;
}

static int snd_timer_free(struct snd_timer *timer)
{
	snd_assert(timer != NULL, return -ENXIO);

	mutex_lock(&register_mutex);
	if (! list_empty(&timer->open_list_head)) {
		struct list_head *p, *n;
		struct snd_timer_instance *ti;
		snd_printk(KERN_WARNING "timer %p is busy?\n", timer);
		list_for_each_safe(p, n, &timer->open_list_head) {
			list_del_init(p);
			ti = list_entry(p, struct snd_timer_instance, open_list);
			ti->timer = NULL;
		}
	}
	list_del(&timer->device_list);
	mutex_unlock(&register_mutex);

	if (timer->private_free)
		timer->private_free(timer);
	kfree(timer);
	return 0;
}

static int snd_timer_dev_free(struct snd_device *device)
{
	struct snd_timer *timer = device->device_data;
	return snd_timer_free(timer);
}

static int snd_timer_dev_register(struct snd_device *dev)
{
	struct snd_timer *timer = dev->device_data;
	struct snd_timer *timer1;

	snd_assert(timer != NULL && timer->hw.start != NULL &&
		   timer->hw.stop != NULL, return -ENXIO);
	if (!(timer->hw.flags & SNDRV_TIMER_HW_SLAVE) &&
	    !timer->hw.resolution && timer->hw.c_resolution == NULL)
	    	return -EINVAL;

	mutex_lock(&register_mutex);
	list_for_each_entry(timer1, &snd_timer_list, device_list) {
		if (timer1->tmr_class > timer->tmr_class)
			break;
		if (timer1->tmr_class < timer->tmr_class)
			continue;
		if (timer1->card && timer->card) {
			if (timer1->card->number > timer->card->number)
				break;
			if (timer1->card->number < timer->card->number)
				continue;
		}
		if (timer1->tmr_device > timer->tmr_device)
			break;
		if (timer1->tmr_device < timer->tmr_device)
			continue;
		if (timer1->tmr_subdevice > timer->tmr_subdevice)
			break;
		if (timer1->tmr_subdevice < timer->tmr_subdevice)
			continue;
		/* conflicts.. */
		mutex_unlock(&register_mutex);
		return -EBUSY;
	}
	list_add_tail(&timer->device_list, &timer1->device_list);
	mutex_unlock(&register_mutex);
	return 0;
}

static int snd_timer_dev_disconnect(struct snd_device *device)
{
	struct snd_timer *timer = device->device_data;
	mutex_lock(&register_mutex);
	list_del_init(&timer->device_list);
	mutex_unlock(&register_mutex);
	return 0;
}

void snd_timer_notify(struct snd_timer *timer, int event, struct timespec *tstamp)
{
	unsigned long flags;
	unsigned long resolution = 0;
	struct snd_timer_instance *ti, *ts;

	if (! (timer->hw.flags & SNDRV_TIMER_HW_SLAVE))
		return;
	snd_assert(event >= SNDRV_TIMER_EVENT_MSTART &&
		   event <= SNDRV_TIMER_EVENT_MRESUME, return);
	spin_lock_irqsave(&timer->lock, flags);
	if (event == SNDRV_TIMER_EVENT_MSTART ||
	    event == SNDRV_TIMER_EVENT_MCONTINUE ||
	    event == SNDRV_TIMER_EVENT_MRESUME) {
		if (timer->hw.c_resolution)
			resolution = timer->hw.c_resolution(timer);
		else
			resolution = timer->hw.resolution;
	}
	list_for_each_entry(ti, &timer->active_list_head, active_list) {
		if (ti->ccallback)
			ti->ccallback(ti, event, tstamp, resolution);
		list_for_each_entry(ts, &ti->slave_active_head, active_list)
			if (ts->ccallback)
				ts->ccallback(ts, event, tstamp, resolution);
	}
	spin_unlock_irqrestore(&timer->lock, flags);
}

/*
 * exported functions for global timers
 */
int snd_timer_global_new(char *id, int device, struct snd_timer **rtimer)
{
	struct snd_timer_id tid;

	tid.dev_class = SNDRV_TIMER_CLASS_GLOBAL;
	tid.dev_sclass = SNDRV_TIMER_SCLASS_NONE;
	tid.card = -1;
	tid.device = device;
	tid.subdevice = 0;
	return snd_timer_new(NULL, id, &tid, rtimer);
}

int snd_timer_global_free(struct snd_timer *timer)
{
	return snd_timer_free(timer);
}

int snd_timer_global_register(struct snd_timer *timer)
{
	struct snd_device dev;

	memset(&dev, 0, sizeof(dev));
	dev.device_data = timer;
	return snd_timer_dev_register(&dev);
}

/*
 *  System timer
 */

struct snd_timer_system_private {
	struct timer_list tlist;
	unsigned long last_expires;
	unsigned long last_jiffies;
	unsigned long correction;
};

static void snd_timer_s_function(unsigned long data)
{
	struct snd_timer *timer = (struct snd_timer *)data;
	struct snd_timer_system_private *priv = timer->private_data;
	unsigned long jiff = jiffies;
	if (time_after(jiff, priv->last_expires))
		priv->correction += (long)jiff - (long)priv->last_expires;
	snd_timer_interrupt(timer, (long)jiff - (long)priv->last_jiffies);
}

static int snd_timer_s_start(struct snd_timer * timer)
{
	struct snd_timer_system_private *priv;
	unsigned long njiff;

	priv = (struct snd_timer_system_private *) timer->private_data;
	njiff = (priv->last_jiffies = jiffies);
	if (priv->correction > timer->sticks - 1) {
		priv->correction -= timer->sticks - 1;
		njiff++;
	} else {
		njiff += timer->sticks - priv->correction;
		priv->correction = 0;
	}
	priv->last_expires = priv->tlist.expires = njiff;
	add_timer(&priv->tlist);
	return 0;
}

static int snd_timer_s_stop(struct snd_timer * timer)
{
	struct snd_timer_system_private *priv;
	unsigned long jiff;

	priv = (struct snd_timer_system_private *) timer->private_data;
	del_timer(&priv->tlist);
	jiff = jiffies;
	if (time_before(jiff, priv->last_expires))
		timer->sticks = priv->last_expires - jiff;
	else
		timer->sticks = 1;
	priv->correction = 0;
	return 0;
}

static struct snd_timer_hardware snd_timer_system =
{
	.flags =	SNDRV_TIMER_HW_FIRST | SNDRV_TIMER_HW_TASKLET,
	.resolution =	1000000000L / HZ,
	.ticks =	10000000L,
	.start =	snd_timer_s_start,