aboutsummaryrefslogtreecommitdiffstats
path: root/arch/alpha/kernel/irq.c
blob: b6114f5c0d2bc6d820cde8171f04d27ecde424e9 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
/*
 *	linux/arch/alpha/kernel/irq.c
 *
 *	Copyright (C) 1995 Linus Torvalds
 *
 * This file contains the code used by various IRQ handling routines:
 * asking for different IRQ's should be done through these routines
 * instead of just grabbing them. Thus setups with different IRQ numbers
 * shouldn't result in any weird surprises, and installing new handlers
 * should be easier.
 */

#include <linux/config.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/errno.h>
#include <linux/kernel_stat.h>
#include <linux/signal.h>
#include <linux/sched.h>
#include <linux/ptrace.h>
#include <linux/interrupt.h>
#include <linux/slab.h>
#include <linux/random.h>
#include <linux/init.h>
#include <linux/irq.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <linux/profile.h>
#include <linux/bitops.h>

#include <asm/system.h>
#include <asm/io.h>
#include <asm/uaccess.h>

/*
 * Controller mappings for all interrupt sources:
 */
irq_desc_t irq_desc[NR_IRQS] __cacheline_aligned = {
	[0 ... NR_IRQS-1] = {
		.handler = &no_irq_type,
		.lock = SPIN_LOCK_UNLOCKED
	}
};

static void register_irq_proc(unsigned int irq);

volatile unsigned long irq_err_count;

/*
 * Special irq handlers.
 */

irqreturn_t no_action(int cpl, void *dev_id, struct pt_regs *regs)
{
	return IRQ_NONE;
}

/*
 * Generic no controller code
 */

static void no_irq_enable_disable(unsigned int irq) { }
static unsigned int no_irq_startup(unsigned int irq) { return 0; }

static void
no_irq_ack(unsigned int irq)
{
	irq_err_count++;
	printk(KERN_CRIT "Unexpected IRQ trap at vector %u\n", irq);
}

struct hw_interrupt_type no_irq_type = {
	.typename	= "none",
	.startup	= no_irq_startup,
	.shutdown	= no_irq_enable_disable,
	.enable		= no_irq_enable_disable,
	.disable	= no_irq_enable_disable,
	.ack		= no_irq_ack,
	.end		= no_irq_enable_disable,
};

int
handle_IRQ_event(unsigned int irq, struct pt_regs *regs,
		 struct irqaction *action)
{
	int status = 1;	/* Force the "do bottom halves" bit */
	int ret;

	do {
		if (!(action->flags & SA_INTERRUPT))
			local_irq_enable();
		else
			local_irq_disable();

		ret = action->handler(irq, action->dev_id, regs);
		if (ret == IRQ_HANDLED)
			status |= action->flags;
		action = action->next;
	} while (action);
	if (status & SA_SAMPLE_RANDOM)
		add_interrupt_randomness(irq);
	local_irq_disable();

	return status;
}

/*
 * Generic enable/disable code: this just calls
 * down into the PIC-specific version for the actual
 * hardware disable after having gotten the irq
 * controller lock. 
 */
void inline
disable_irq_nosync(unsigned int irq)
{
	irq_desc_t *desc = irq_desc + irq;
	unsigned long flags;

	spin_lock_irqsave(&desc->lock, flags);
	if (!desc->depth++) {
		desc->status |= IRQ_DISABLED;
		desc->handler->disable(irq);
	}
	spin_unlock_irqrestore(&desc->lock, flags);
}

/*
 * Synchronous version of the above, making sure the IRQ is
 * no longer running on any other IRQ..
 */
void
disable_irq(unsigned int irq)
{
	disable_irq_nosync(irq);
	synchronize_irq(irq);
}

void
enable_irq(unsigned int irq)
{
	irq_desc_t *desc = irq_desc + irq;
	unsigned long flags;

	spin_lock_irqsave(&desc->lock, flags);
	switch (desc->depth) {
	case 1: {
		unsigned int status = desc->status & ~IRQ_DISABLED;
		desc->status = status;
		if ((status & (IRQ_PENDING | IRQ_REPLAY)) == IRQ_PENDING) {
			desc->status = status | IRQ_REPLAY;
			hw_resend_irq(desc->handler,irq);
		}
		desc->handler->enable(irq);
		/* fall-through */
	}
	default:
		desc->depth--;
		break;
	case 0:
		printk(KERN_ERR "enable_irq() unbalanced from %p\n",
		       __builtin_return_address(0));
	}
	spin_unlock_irqrestore(&desc->lock, flags);
}

int
setup_irq(unsigned int irq, struct irqaction * new)
{
	int shared = 0;
	struct irqaction *old, **p;
	unsigned long flags;
	irq_desc_t *desc = irq_desc + irq;

        if (desc->handler == &no_irq_type)
		return -ENOSYS;

	/*
	 * 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|IRQ_AUTODETECT|IRQ_WAITING|IRQ_INPROGRESS);
		desc->handler->startup(irq);
	}
	spin_unlock_irqrestore(&desc->lock,flags);

	return 0;
}

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

#ifdef CONFIG_SMP 
static struct proc_dir_entry * smp_affinity_entry[NR_IRQS];
static char irq_user_affinity[NR_IRQS];
static cpumask_t irq_affinity[NR_IRQS] = { [0 ... NR_IRQS-1] = CPU_MASK_ALL };

static void
select_smp_affinity(int irq)
{
	static int last_cpu;
	int cpu = last_cpu + 1;

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

	while (!cpu_possible(cpu))
		cpu = (cpu < (NR_CPUS-1) ? cpu + 1 : 0);
	last_cpu = cpu;

	irq_affinity[irq] = cpumask_of_cpu(cpu);
	irq_desc[irq].handler->set_affinity(irq, cpumask_of_cpu(cpu));
}

static int
irq_affinity_read_proc (char *page, char **start, off_t off,
			int count, int *eof, void *data)
{
	int len = cpumask_scnprintf(page, count, irq_affinity[(long)data]);
	if (count - len < 2)
		return -EINVAL;
	len += sprintf(page + len, "\n");
	return len;
}

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

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

	err = cpumask_parse(buffer, count, new_value);

	/* The special value 0 means release control of the
	   affinity to kernel.  */
	cpus_and(new_value, new_value, cpu_online_map);
	if (cpus_empty(new_value)) {
		irq_user_affinity[irq] = 0;
		select_smp_affinity(irq);
	}
	/* 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.  */
	else {
		irq_affinity[irq] = new_value;
		irq_user_affinity[irq] = 1;
		irq_desc[irq].handler->set_affinity(irq, new_value);
	}

	return full_count;
}

#endif /* CONFIG_SMP */

#define MAX_NAMELEN 10

static void
register_irq_proc (unsigned int irq)
{
	char name [MAX_NAMELEN];

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

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

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

#ifdef CONFIG_SMP 
	if (irq_desc[irq].handler->set_affinity) {
		struct proc_dir_entry *entry;
		/* create /proc/irq/1234/smp_affinity */
		entry = create_proc_entry("smp_affinity", 0600, irq_dir[irq]);

		if (entry) {
			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;
	}
#endif
}

void
init_irq_proc (void)
{
	int i;

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

#ifdef CONFIG_SMP 
	/* create /proc/irq/prof_cpu_mask */
	create_prof_cpu_mask(root_irq_dir);
#endif

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

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

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

#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) && !dev_id) {
		printk(KERN_ERR
		       "Bad boy: %s (at %p) called us without a dev_id!\n",
		       devname, __builtin_return_address(0));
	}
#endif

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

	action->handler = handler;
	action->flags = irqflags;
	cpus_clear(action->mask);
	action->name = devname;
	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