irq.c

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{
	irq_desc_t *desc = irq_desc + irq;
	int cpu = smp_processor_id();

	kstat.irqs[cpu][irq]++;

	desc->handler->ack(irq);
	handle_IRQ_event(irq, regs, desc->action);
	desc->handler->end(irq);
}

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

	kstat.irqs[cpu][irq]++;
	spin_lock(&desc->lock);
	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 do_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))
			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);

	return 1;
}

int request_irq(unsigned int irq, 
		void (*handler)(int, void *, struct pt_regs *),
		unsigned long irqflags, 
		const char * devname,
		void *dev_id)
{
	int retval;
	struct irqaction * action;

#if 1
	/*
	 * Sanity-check: shared interrupts should REALLY pass in
	 * a real dev-ID, otherwise we'll have trouble later trying
	 * to figure out which interrupt is which (messes up the
	 * interrupt freeing logic etc).
	 */
	if (irqflags & SA_SHIRQ) {
		if (!dev_id)
			printk("Bad boy: %s (at 0x%x) called us without a dev_id!\n", devname, (&irq)[-1]);
	}
#endif

	if (irq >= NR_IRQS)
		return -EINVAL;
	if (!handler)
		return -EINVAL;

	action = (struct irqaction *)
			kmalloc(sizeof(struct irqaction), GFP_KERNEL);
	if (!action)
		return -ENOMEM;

	action->handler = handler;
	action->flags = irqflags;
	action->mask = 0;
	action->name = devname;
	action->next = NULL;
	action->dev_id = dev_id;

	retval = setup_irq(irq, action);
	if (retval)
		kfree(action);
	return retval;
}
		
void free_irq(unsigned int irq, void *dev_id)
{
	irq_desc_t *desc;
	struct irqaction **p;
	unsigned long flags;

	if (irq >= NR_IRQS)
		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 it - 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("Trying to free free IRQ%d\n",irq);
		spin_unlock_irqrestore(&desc->lock,flags);
		return;
	}
}

/*
 * 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)
{
	unsigned int i;
	irq_desc_t *desc;
	unsigned long val;
	unsigned long delay;

	/* 
	 * 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 */ synchronize_irq();

	/*
	 * enable any unassigned irqs
	 * (we must startup again here because if a longstanding irq
	 * happened in the previous stage, it may have masked itself)
	 */
	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 */ synchronize_irq();

	/*
	 * 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;
}

/*
 * 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 < 16; 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))
				mask |= 1 << i;

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

	return mask & val;
}

/*
 * Return the one interrupt that triggered (this can
 * handle any interrupt source)
 */
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;
}

/* this was setup_x86_irq but it seems pretty generic */
int setup_irq(unsigned int irq, struct irqaction * new)
{
	int shared = 0;
	unsigned long flags;
	struct irqaction *old, **p;
	irq_desc_t *desc = irq_desc + irq;

	/*
	 * Some drivers like serial.c use request_irq() heavily,
	 * so we have to be careful not to interfere with a
	 * running system.
	 */
	if (new->flags & SA_SAMPLE_RANDOM) {
		/*
		 * This function might sleep, we want to call it first,
		 * outside of the atomic block.
		 * Yes, this might clear the entropy pool if the wrong
		 * driver is attempted to be loaded, without actually
		 * installing a new handler, but is this really a problem,
		 * only the sysadmin is able to do this.
		 */
		rand_initialize_irq(irq);
	}

	/*
	 * The following block of code has to be executed atomically
	 */
	spin_lock_irqsave(&desc->lock,flags);
	p = &desc->action;
	if ((old = *p) != NULL) {
		/* Can't share interrupts unless both agree to */
		if (!(old->flags & new->flags & SA_SHIRQ)) {
			spin_unlock_irqrestore(&desc->lock,flags);
			return -EBUSY;
		}

		/* add new interrupt at end of irq queue */
		do {
			p = &old->next;
			old = *p;
		} while (old);
		shared = 1;
	}

	*p = new;

	if (!shared) {
		desc->depth = 0;
		desc->status &= ~IRQ_DISABLED;
		desc->handler->startup(irq);
	}
	spin_unlock_irqrestore(&desc->lock,flags);

	register_irq_proc(irq);
	return 0;
}

static struct proc_dir_entry * root_irq_dir;
static struct proc_dir_entry * irq_dir [NR_IRQS];
static struct proc_dir_entry * smp_affinity_entry [NR_IRQS];

static unsigned long irq_affinity [NR_IRQS] = { [0 ... NR_IRQS-1] = ~0UL };

#define HEX_DIGITS 8

static int irq_affinity_read_proc (char *page, char **start, off_t off,
			int count, int *eof, void *data)
{
	if (count < HEX_DIGITS+1)
		return -EINVAL;
	return sprintf (page, "%08lx\n", irq_affinity[(long)data]);
}

static unsigned int parse_hex_value (const char *buffer,
		unsigned long count, unsigned long *ret)
{
	unsigned char hexnum [HEX_DIGITS];
	unsigned long value;
	int i;

	if (!count)
		return -EINVAL;
	if (count > HEX_DIGITS)
		count = HEX_DIGITS;
	if (copy_from_user(hexnum, buffer, count))
		return -EFAULT;

	/*
	 * Parse the first 8 characters as a hex string, any non-hex char
	 * is end-of-string. '00e1', 'e1', '00E1', 'E1' are all the same.
	 */
	value = 0;

	for (i = 0; i < count; i++) {
		unsigned int c = hexnum[i];

		switch (c) {
			case '0' ... '9': c -= '0'; break;
			case 'a' ... 'f': c -= 'a'-10; break;
			case 'A' ... 'F': c -= 'A'-10; break;
		default:
			goto out;
		}
		value = (value << 4) | c;
	}
out:
	*ret = value;
	return 0;
}

static int irq_affinity_write_proc (struct file *file, const char *buffer,
					unsigned long count, void *data)
{
	int irq = (long) data, full_count = count, err;
	unsigned long new_value;

	if (!irq_desc[irq].handler->set_affinity)
		return -EIO;

	err = parse_hex_value(buffer, count, &new_value);

#if CONFIG_SMP
	/*
	 * Do not allow disabling IRQs completely - it's a too easy
	 * way to make the system unusable accidentally :-) At least
	 * one online CPU still has to be targeted.
	 */
	if (!(new_value & cpu_online_map))
		return -EINVAL;
#endif

	irq_affinity[irq] = new_value;
	irq_desc[irq].handler->set_affinity(irq, new_value);

	return full_count;
}

static int prof_cpu_mask_read_proc (char *page, char **start, off_t off,
			int count, int *eof, void *data)
{
	unsigned long *mask = (unsigned long *) data;
	if (count < HEX_DIGITS+1)
		return -EINVAL;
	return sprintf (page, "%08lx\n", *mask);
}

static int prof_cpu_mask_write_proc (struct file *file, const char *buffer,
					unsigned long count, void *data)
{
	unsigned long *mask = (unsigned long *) data, full_count = count, err;
	unsigned long new_value;

	err = parse_hex_value(buffer, count, &new_value);
	if (err)
		return err;

	*mask = new_value;
	return full_count;
}

#define MAX_NAMELEN 10

static void register_irq_proc (unsigned int irq)
{
	struct proc_dir_entry *entry;
	char name [MAX_NAMELEN];

	if (!root_irq_dir || (irq_desc[irq].handler == &no_irq_type))
		return;

	memset(name, 0, MAX_NAMELEN);
	sprintf(name, "%d", irq);

	/* create /proc/irq/1234 */
	irq_dir[irq] = proc_mkdir(name, root_irq_dir);

	/* create /proc/irq/1234/smp_affinity */
	entry = create_proc_entry("smp_affinity", 0600, irq_dir[irq]);

	entry->nlink = 1;
	entry->data = (void *)(long)irq;
	entry->read_proc = irq_affinity_read_proc;
	entry->write_proc = irq_affinity_write_proc;

	smp_affinity_entry[irq] = entry;
}

unsigned long prof_cpu_mask = -1;

void init_irq_proc (void)
{
	struct proc_dir_entry *entry;
	int i;

	/* create /proc/irq */
	root_irq_dir = proc_mkdir("irq", 0);

	/* create /proc/irq/prof_cpu_mask */
	entry = create_proc_entry("prof_cpu_mask", 0600, root_irq_dir);

	entry->nlink = 1;
	entry->data = (void *)&prof_cpu_mask;
	entry->read_proc = prof_cpu_mask_read_proc;
	entry->write_proc = prof_cpu_mask_write_proc;

	/*
	 * Create entries for all existing IRQs.
	 */
	for (i = 0; i < NR_IRQS; i++) {
		if (irq_desc[i].handler == &no_irq_type)
			continue;
		register_irq_proc(i);
	}
}