irq.c

底层驱动开发

	action->next = NULL;
	action->dev_id = dev_id;

#ifdef CONFIG_SMP
	select_smp_affinity(irq);
#endif

	retval = setup_irq(irq, action);
	if (retval)
		kfree(action);
	return retval;
}

EXPORT_SYMBOL(request_irq);

void
free_irq(unsigned int irq, void *dev_id)
{
	irq_desc_t *desc;
	struct irqaction **p;
	unsigned long flags;

	if (irq >= ACTUAL_NR_IRQS) {
		printk(KERN_CRIT "Trying to free IRQ%d\n", irq);
		return;
	}

	desc = irq_desc + irq;
	spin_lock_irqsave(&desc->lock,flags);
	p = &desc->action;
	for (;;) {
		struct irqaction * action = *p;
		if (action) {
			struct irqaction **pp = p;
			p = &action->next;
			if (action->dev_id != dev_id)
				continue;

			/* Found - now remove it from the list of entries.  */
			*pp = action->next;
			if (!desc->action) {
				desc->status |= IRQ_DISABLED;
				desc->handler->shutdown(irq);
			}
			spin_unlock_irqrestore(&desc->lock,flags);

#ifdef CONFIG_SMP
			/* Wait to make sure it's not being used on
			   another CPU.  */
			while (desc->status & IRQ_INPROGRESS)
				barrier();
#endif
			kfree(action);
			return;
		}
		printk(KERN_ERR "Trying to free free IRQ%d\n",irq);
		spin_unlock_irqrestore(&desc->lock,flags);
		return;
	}
}

EXPORT_SYMBOL(free_irq);

int
show_interrupts(struct seq_file *p, void *v)
{
#ifdef CONFIG_SMP
	int j;
#endif
	int i = *(loff_t *) v;
	struct irqaction * action;
	unsigned long flags;

#ifdef CONFIG_SMP
	if (i == 0) {
		seq_puts(p, "           ");
		for (i = 0; i < NR_CPUS; i++)
			if (cpu_online(i))
				seq_printf(p, "CPU%d       ", i);
		seq_putc(p, '\n');
	}
#endif

	if (i < ACTUAL_NR_IRQS) {
		spin_lock_irqsave(&irq_desc[i].lock, flags);
		action = irq_desc[i].action;
		if (!action) 
			goto unlock;
		seq_printf(p, "%3d: ",i);
#ifndef CONFIG_SMP
		seq_printf(p, "%10u ", kstat_irqs(i));
#else
		for (j = 0; j < NR_CPUS; j++)
			if (cpu_online(j))
				seq_printf(p, "%10u ", kstat_cpu(j).irqs[i]);
#endif
		seq_printf(p, " %14s", irq_desc[i].handler->typename);
		seq_printf(p, "  %c%s",
			(action->flags & SA_INTERRUPT)?'+':' ',
			action->name);

		for (action=action->next; action; action = action->next) {
			seq_printf(p, ", %c%s",
				  (action->flags & SA_INTERRUPT)?'+':' ',
				   action->name);
		}

		seq_putc(p, '\n');
unlock:
		spin_unlock_irqrestore(&irq_desc[i].lock, flags);
	} else if (i == ACTUAL_NR_IRQS) {
#ifdef CONFIG_SMP
		seq_puts(p, "IPI: ");
		for (i = 0; i < NR_CPUS; i++)
			if (cpu_online(i))
				seq_printf(p, "%10lu ", cpu_data[i].ipi_count);
		seq_putc(p, '\n');
#endif
		seq_printf(p, "ERR: %10lu\n", irq_err_count);
	}
	return 0;
}


/*
 * handle_irq handles all normal device IRQ's (the special
 * SMP cross-CPU interrupts have their own specific
 * handlers).
 */

#define MAX_ILLEGAL_IRQS 16

void
handle_irq(int irq, struct pt_regs * regs)
{	
	/* 
	 * We ack quickly, we don't want the irq controller
	 * thinking we're snobs just because some other CPU has
	 * disabled global interrupts (we have already done the
	 * INT_ACK cycles, it's too late to try to pretend to the
	 * controller that we aren't taking the interrupt).
	 *
	 * 0 return value means that this irq is already being
	 * handled by some other CPU. (or is disabled)
	 */
	int cpu = smp_processor_id();
	irq_desc_t *desc = irq_desc + irq;
	struct irqaction * action;
	unsigned int status;
	static unsigned int illegal_count=0;
	
	if ((unsigned) irq > ACTUAL_NR_IRQS && illegal_count < MAX_ILLEGAL_IRQS ) {
		irq_err_count++;
		illegal_count++;
		printk(KERN_CRIT "device_interrupt: invalid interrupt %d\n",
		       irq);
		return;
	}

	irq_enter();
	kstat_cpu(cpu).irqs[irq]++;
	spin_lock_irq(&desc->lock); /* mask also the higher prio events */
	desc->handler->ack(irq);
	/*
	 * REPLAY is when Linux resends an IRQ that was dropped earlier.
	 * WAITING is used by probe to mark irqs that are being tested.
	 */
	status = desc->status & ~(IRQ_REPLAY | IRQ_WAITING);
	status |= IRQ_PENDING; /* we _want_ to handle it */

	/*
	 * If the IRQ is disabled for whatever reason, we cannot
	 * use the action we have.
	 */
	action = NULL;
	if (!(status & (IRQ_DISABLED | IRQ_INPROGRESS))) {
		action = desc->action;
		status &= ~IRQ_PENDING; /* we commit to handling */
		status |= IRQ_INPROGRESS; /* we are handling it */
	}
	desc->status = status;

	/*
	 * If there is no IRQ handler or it was disabled, exit early.
	 * Since we set PENDING, if another processor is handling
	 * a different instance of this same irq, the other processor
	 * will take care of it.
	 */
	if (!action)
		goto out;

	/*
	 * Edge triggered interrupts need to remember pending events.
	 * This applies to any hw interrupts that allow a second
	 * instance of the same irq to arrive while we are in handle_irq
	 * or in the handler. But the code here only handles the _second_
	 * instance of the irq, not the third or fourth. So it is mostly
	 * useful for irq hardware that does not mask cleanly in an
	 * SMP environment.
	 */
	for (;;) {
		spin_unlock(&desc->lock);
		handle_IRQ_event(irq, regs, action);
		spin_lock(&desc->lock);
		
		if (!(desc->status & IRQ_PENDING)
		    || (desc->status & IRQ_LEVEL))
			break;
		desc->status &= ~IRQ_PENDING;
	}
	desc->status &= ~IRQ_INPROGRESS;
out:
	/*
	 * The ->end() handler has to deal with interrupts which got
	 * disabled while the handler was running.
	 */
	desc->handler->end(irq);
	spin_unlock(&desc->lock);

	irq_exit();
}

/*
 * IRQ autodetection code..
 *
 * This depends on the fact that any interrupt that
 * comes in on to an unassigned handler will get stuck
 * with "IRQ_WAITING" cleared and the interrupt
 * disabled.
 */
unsigned long
probe_irq_on(void)
{
	int i;
	irq_desc_t *desc;
	unsigned long delay;
	unsigned long val;

	/* Something may have generated an irq long ago and we want to
	   flush such a longstanding irq before considering it as spurious. */
	for (i = NR_IRQS-1; i >= 0; i--) {
		desc = irq_desc + i;

		spin_lock_irq(&desc->lock);
		if (!irq_desc[i].action) 
			irq_desc[i].handler->startup(i);
		spin_unlock_irq(&desc->lock);
	}

	/* Wait for longstanding interrupts to trigger. */
	for (delay = jiffies + HZ/50; time_after(delay, jiffies); )
		/* about 20ms delay */ barrier();

	/* enable any unassigned irqs (we must startup again here because
	   if a longstanding irq happened in the previous stage, it may have
	   masked itself) first, enable any unassigned irqs. */
	for (i = NR_IRQS-1; i >= 0; i--) {
		desc = irq_desc + i;

		spin_lock_irq(&desc->lock);
		if (!desc->action) {
			desc->status |= IRQ_AUTODETECT | IRQ_WAITING;
			if (desc->handler->startup(i))
				desc->status |= IRQ_PENDING;
		}
		spin_unlock_irq(&desc->lock);
	}

	/*
	 * Wait for spurious interrupts to trigger
	 */
	for (delay = jiffies + HZ/10; time_after(delay, jiffies); )
		/* about 100ms delay */ barrier();

	/*
	 * Now filter out any obviously spurious interrupts
	 */
	val = 0;
	for (i=0; i<NR_IRQS; i++) {
		irq_desc_t *desc = irq_desc + i;
		unsigned int status;

		spin_lock_irq(&desc->lock);
		status = desc->status;

		if (status & IRQ_AUTODETECT) {
			/* It triggered already - consider it spurious. */
			if (!(status & IRQ_WAITING)) {
				desc->status = status & ~IRQ_AUTODETECT;
				desc->handler->shutdown(i);
			} else
				if (i < 32)
					val |= 1 << i;
		}
		spin_unlock_irq(&desc->lock);
	}

	return val;
}

EXPORT_SYMBOL(probe_irq_on);

/*
 * Return a mask of triggered interrupts (this
 * can handle only legacy ISA interrupts).
 */
unsigned int
probe_irq_mask(unsigned long val)
{
	int i;
	unsigned int mask;

	mask = 0;
	for (i = 0; i < NR_IRQS; i++) {
		irq_desc_t *desc = irq_desc + i;
		unsigned int status;

		spin_lock_irq(&desc->lock);
		status = desc->status;

		if (status & IRQ_AUTODETECT) {
			/* We only react to ISA interrupts */
			if (!(status & IRQ_WAITING)) {
				if (i < 16)
					mask |= 1 << i;
			}

			desc->status = status & ~IRQ_AUTODETECT;
			desc->handler->shutdown(i);
		}
		spin_unlock_irq(&desc->lock);
	}

	return mask & val;
}

/*
 * Get the result of the IRQ probe.. A negative result means that
 * we have several candidates (but we return the lowest-numbered
 * one).
 */

int
probe_irq_off(unsigned long val)
{
	int i, irq_found, nr_irqs;

	nr_irqs = 0;
	irq_found = 0;
	for (i=0; i<NR_IRQS; i++) {
		irq_desc_t *desc = irq_desc + i;
		unsigned int status;

		spin_lock_irq(&desc->lock);
		status = desc->status;

		if (status & IRQ_AUTODETECT) {
			if (!(status & IRQ_WAITING)) {
				if (!nr_irqs)
					irq_found = i;
				nr_irqs++;
			}
			desc->status = status & ~IRQ_AUTODETECT;
			desc->handler->shutdown(i);
		}
		spin_unlock_irq(&desc->lock);
	}

	if (nr_irqs > 1)
		irq_found = -irq_found;
	return irq_found;
}

EXPORT_SYMBOL(probe_irq_off);

#ifdef CONFIG_SMP
void synchronize_irq(unsigned int irq)
{
        /* is there anything to synchronize with? */
	if (!irq_desc[irq].action)
		return;

	while (irq_desc[irq].status & IRQ_INPROGRESS)
		barrier();
}
#endif