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   1 /*
   2  *      linux/arch/alpha/kernel/irq.c
   3  *
   4  *      Copyright (C) 1995 Linus Torvalds
   5  *
   6  * This file contains the code used by various IRQ handling routines:
   7  * asking for different IRQ's should be done through these routines
   8  * instead of just grabbing them. Thus setups with different IRQ numbers
   9  * shouldn't result in any weird surprises, and installing new handlers
  10  * should be easier.
  11  */
  12
  13 #include <linux/config.h>
  14 #include <linux/kernel.h>
  15 #include <linux/module.h>
  16 #include <linux/errno.h>
  17 #include <linux/kernel_stat.h>
  18 #include <linux/signal.h>
  19 #include <linux/sched.h>
  20 #include <linux/ptrace.h>
  21 #include <linux/interrupt.h>
  22 #include <linux/slab.h>
  23 #include <linux/random.h>
  24 #include <linux/init.h>
  25 #include <linux/irq.h>
  26 #include <linux/proc_fs.h>
  27 #include <linux/seq_file.h>
  28 #include <linux/profile.h>
  29 #include <linux/bitops.h>
  30
  31 #include <asm/system.h>
  32 #include <asm/io.h>
  33 #include <asm/uaccess.h>
  34
  35 /*
  36  * Controller mappings for all interrupt sources:
  37  */
  38 irq_desc_t irq_desc[NR_IRQS] __cacheline_aligned = {
  39         [0 ... NR_IRQS-1] = {
  40                 .handler = &no_irq_type,
  41                 .lock = SPIN_LOCK_UNLOCKED
  42         }
  43 };
  44
  45 static void register_irq_proc(unsigned int irq);
  46
  47 volatile unsigned long irq_err_count;
  48
  49 /*
  50  * Special irq handlers.
  51  */
  52
  53 irqreturn_t no_action(int cpl, void *dev_id, struct pt_regs *regs)
  54 {
  55         return IRQ_NONE;
  56 }
  57
  58 /*
  59  * Generic no controller code
  60  */
  61
  62 static void no_irq_enable_disable(unsigned int irq) { }
  63 static unsigned int no_irq_startup(unsigned int irq) { return 0; }
  64
  65 static void
  66 no_irq_ack(unsigned int irq)
  67 {
  68         irq_err_count++;
  69         printk(KERN_CRIT "Unexpected IRQ trap at vector %u\n", irq);
  70 }
  71
  72 struct hw_interrupt_type no_irq_type = {
  73         .typename       = "none",
  74         .startup        = no_irq_startup,
  75         .shutdown       = no_irq_enable_disable,
  76         .enable         = no_irq_enable_disable,
  77         .disable        = no_irq_enable_disable,
  78         .ack            = no_irq_ack,
  79         .end            = no_irq_enable_disable,
  80 };
  81
  82 int
  83 handle_IRQ_event(unsigned int irq, struct pt_regs *regs,
  84                  struct irqaction *action)
  85 {
  86         int status = 1; /* Force the "do bottom halves" bit */
  87         int ret;
  88
  89         do {
  90                 if (!(action->flags & SA_INTERRUPT))
  91                         local_irq_enable();
  92                 else
  93                         local_irq_disable();
  94
  95                 ret = action->handler(irq, action->dev_id, regs);
  96                 if (ret == IRQ_HANDLED)
  97                         status |= action->flags;
  98                 action = action->next;
  99         } while (action);
 100         if (status & SA_SAMPLE_RANDOM)
 101                 add_interrupt_randomness(irq);
 102         local_irq_disable();
 103
 104         return status;
 105 }
 106
 107 /*
 108  * Generic enable/disable code: this just calls
 109  * down into the PIC-specific version for the actual
 110  * hardware disable after having gotten the irq
 111  * controller lock.
 112  */
 113 void inline
 114 disable_irq_nosync(unsigned int irq)
 115 {
 116         irq_desc_t *desc = irq_desc + irq;
 117         unsigned long flags;
 118
 119         spin_lock_irqsave(&desc->lock, flags);
 120         if (!desc->depth++) {
 121                 desc->status |= IRQ_DISABLED;
 122                 desc->handler->disable(irq);
 123         }
 124         spin_unlock_irqrestore(&desc->lock, flags);
 125 }
 126
 127 /*
 128  * Synchronous version of the above, making sure the IRQ is
 129  * no longer running on any other IRQ..
 130  */
 131 void
 132 disable_irq(unsigned int irq)
 133 {
 134         disable_irq_nosync(irq);
 135         synchronize_irq(irq);
 136 }
 137
 138 void
 139 enable_irq(unsigned int irq)
 140 {
 141         irq_desc_t *desc = irq_desc + irq;
 142         unsigned long flags;
 143
 144         spin_lock_irqsave(&desc->lock, flags);
 145         switch (desc->depth) {
 146         case 1: {
 147                 unsigned int status = desc->status & ~IRQ_DISABLED;
 148                 desc->status = status;
 149                 if ((status & (IRQ_PENDING | IRQ_REPLAY)) == IRQ_PENDING) {
 150                         desc->status = status | IRQ_REPLAY;
 151                         hw_resend_irq(desc->handler,irq);
 152                 }
 153                 desc->handler->enable(irq);
 154                 /* fall-through */
 155         }
 156         default:
 157                 desc->depth--;
 158                 break;
 159         case 0:
 160                 printk(KERN_ERR "enable_irq() unbalanced from %p\n",
 161                        __builtin_return_address(0));
 162         }
 163         spin_unlock_irqrestore(&desc->lock, flags);
 164 }
 165
 166 int
 167 setup_irq(unsigned int irq, struct irqaction * new)
 168 {
 169         int shared = 0;
 170         struct irqaction *old, **p;
 171         unsigned long flags;
 172         irq_desc_t *desc = irq_desc + irq;
 173
 174         if (desc->handler == &no_irq_type)
 175                 return -ENOSYS;
 176
 177         /*
 178          * Some drivers like serial.c use request_irq() heavily,
 179          * so we have to be careful not to interfere with a
 180          * running system.
 181          */
 182         if (new->flags & SA_SAMPLE_RANDOM) {
 183                 /*
 184                  * This function might sleep, we want to call it first,
 185                  * outside of the atomic block.
 186                  * Yes, this might clear the entropy pool if the wrong
 187                  * driver is attempted to be loaded, without actually
 188                  * installing a new handler, but is this really a problem,
 189                  * only the sysadmin is able to do this.
 190                  */
 191                 rand_initialize_irq(irq);
 192         }
 193
 194         /*
 195          * The following block of code has to be executed atomically
 196          */
 197         spin_lock_irqsave(&desc->lock,flags);
 198         p = &desc->action;
 199         if ((old = *p) != NULL) {
 200                 /* Can't share interrupts unless both agree to */
 201                 if (!(old->flags & new->flags & SA_SHIRQ)) {
 202                         spin_unlock_irqrestore(&desc->lock,flags);
 203                         return -EBUSY;
 204                 }
 205
 206                 /* add new interrupt at end of irq queue */
 207                 do {
 208                         p = &old->next;
 209                         old = *p;
 210                 } while (old);
 211                 shared = 1;
 212         }
 213
 214         *p = new;
 215
 216         if (!shared) {
 217                 desc->depth = 0;
 218                 desc->status &=
 219                     ~(IRQ_DISABLED|IRQ_AUTODETECT|IRQ_WAITING|IRQ_INPROGRESS);
 220                 desc->handler->startup(irq);
 221         }
 222         spin_unlock_irqrestore(&desc->lock,flags);
 223
 224         return 0;
 225 }
 226
 227 static struct proc_dir_entry * root_irq_dir;
 228 static struct proc_dir_entry * irq_dir[NR_IRQS];
 229
 230 #ifdef CONFIG_SMP
 231 static struct proc_dir_entry * smp_affinity_entry[NR_IRQS];
 232 static char irq_user_affinity[NR_IRQS];
 233 static cpumask_t irq_affinity[NR_IRQS] = { [0 ... NR_IRQS-1] = CPU_MASK_ALL };
 234
 235 static void
 236 select_smp_affinity(int irq)
 237 {
 238         static int last_cpu;
 239         int cpu = last_cpu + 1;
 240
 241         if (! irq_desc[irq].handler->set_affinity || irq_user_affinity[irq])
 242                 return;
 243
 244         while (!cpu_possible(cpu))
 245                 cpu = (cpu < (NR_CPUS-1) ? cpu + 1 : 0);
 246         last_cpu = cpu;
 247
 248         irq_affinity[irq] = cpumask_of_cpu(cpu);
 249         irq_desc[irq].handler->set_affinity(irq, cpumask_of_cpu(cpu));
 250 }
 251
 252 static int
 253 irq_affinity_read_proc (char *page, char **start, off_t off,
 254                         int count, int *eof, void *data)
 255 {
 256         int len = cpumask_scnprintf(page, count, irq_affinity[(long)data]);
 257         if (count - len < 2)
 258                 return -EINVAL;
 259         len += sprintf(page + len, "\n");
 260         return len;
 261 }
 262
 263 static int
 264 irq_affinity_write_proc(struct file *file, const char __user *buffer,
 265                         unsigned long count, void *data)
 266 {
 267         int irq = (long) data, full_count = count, err;
 268         cpumask_t new_value;
 269
 270         if (!irq_desc[irq].handler->set_affinity)
 271                 return -EIO;
 272
 273         err = cpumask_parse(buffer, count, new_value);
 274
 275         /* The special value 0 means release control of the
 276            affinity to kernel.  */
 277         cpus_and(new_value, new_value, cpu_online_map);
 278         if (cpus_empty(new_value)) {
 279                 irq_user_affinity[irq] = 0;
 280                 select_smp_affinity(irq);
 281         }
 282         /* Do not allow disabling IRQs completely - it's a too easy
 283            way to make the system unusable accidentally :-) At least
 284            one online CPU still has to be targeted.  */
 285         else {
 286                 irq_affinity[irq] = new_value;
 287                 irq_user_affinity[irq] = 1;
 288                 irq_desc[irq].handler->set_affinity(irq, new_value);
 289         }
 290
 291         return full_count;
 292 }
 293
 294 #endif /* CONFIG_SMP */
 295
 296 #define MAX_NAMELEN 10
 297
 298 static void
 299 register_irq_proc (unsigned int irq)
 300 {
 301         char name [MAX_NAMELEN];
 302
 303         if (!root_irq_dir || (irq_desc[irq].handler == &no_irq_type) ||
 304             irq_dir[irq])
 305                 return;
 306
 307         memset(name, 0, MAX_NAMELEN);
 308         sprintf(name, "%d", irq);
 309
 310         /* create /proc/irq/1234 */
 311         irq_dir[irq] = proc_mkdir(name, root_irq_dir);
 312
 313 #ifdef CONFIG_SMP
 314         if (irq_desc[irq].handler->set_affinity) {
 315                 struct proc_dir_entry *entry;
 316                 /* create /proc/irq/1234/smp_affinity */
 317                 entry = create_proc_entry("smp_affinity", 0600, irq_dir[irq]);
 318
 319                 if (entry) {
 320                         entry->nlink = 1;
 321                         entry->data = (void *)(long)irq;
 322                         entry->read_proc = irq_affinity_read_proc;
 323                         entry->write_proc = irq_affinity_write_proc;
 324                 }
 325
 326                 smp_affinity_entry[irq] = entry;
 327         }
 328 #endif
 329 }
 330
 331 void
 332 init_irq_proc (void)
 333 {
 334         int i;
 335
 336         /* create /proc/irq */
 337         root_irq_dir = proc_mkdir("irq", NULL);
 338
 339 #ifdef CONFIG_SMP
 340         /* create /proc/irq/prof_cpu_mask */
 341         create_prof_cpu_mask(root_irq_dir);
 342 #endif
 343
 344         /*
 345          * Create entries for all existing IRQs.
 346          */
 347         for (i = 0; i < ACTUAL_NR_IRQS; i++) {
 348                 if (irq_desc[i].handler == &no_irq_type)
 349                         continue;
 350                 register_irq_proc(i);
 351         }
 352 }
 353
 354 int
 355 request_irq(unsigned int irq, irqreturn_t (*handler)(int, void *, struct pt_regs *),
 356             unsigned long irqflags, const char * devname, void *dev_id)
 357 {
 358         int retval;
 359         struct irqaction * action;
 360
 361         if (irq >= ACTUAL_NR_IRQS)
 362                 return -EINVAL;
 363         if (!handler)
 364                 return -EINVAL;
 365
 366 #if 1
 367         /*
 368          * Sanity-check: shared interrupts should REALLY pass in
 369          * a real dev-ID, otherwise we'll have trouble later trying
 370          * to figure out which interrupt is which (messes up the
 371          * interrupt freeing logic etc).
 372          */
 373         if ((irqflags & SA_SHIRQ) && !dev_id) {
 374                 printk(KERN_ERR
 375                        "Bad boy: %s (at %p) called us without a dev_id!\n",
 376                        devname, __builtin_return_address(0));
 377         }
 378 #endif
 379
 380         action = (struct irqaction *)
 381                         kmalloc(sizeof(struct irqaction), GFP_KERNEL);
 382         if (!action)
 383                 return -ENOMEM;
 384
 385         action->handler = handler;
 386         action->flags = irqflags;
 387         cpus_clear(action->mask);
 388         action->name = devname;
 389         action->next = NULL;
 390         action->dev_id = dev_id;
 391
 392 #ifdef CONFIG_SMP
 393         select_smp_affinity(irq);
 394 #endif
 395
 396         retval = setup_irq(irq, action);
 397         if (retval)
 398                 kfree(action);
 399         return retval;
 400 }
 401
 402 EXPORT_SYMBOL(request_irq);
 403
 404 void
 405 free_irq(unsigned int irq, void *dev_id)
 406 {
 407         irq_desc_t *desc;
 408         struct irqaction **p;
 409         unsigned long flags;
 410
 411         if (irq >= ACTUAL_NR_IRQS) {
 412                 printk(KERN_CRIT "Trying to free IRQ%d\n", irq);
 413                 return;
 414         }
 415
 416         desc = irq_desc + irq;
 417         spin_lock_irqsave(&desc->lock,flags);
 418         p = &desc->action;
 419         for (;;) {
 420                 struct irqaction * action = *p;
 421                 if (action) {
 422                         struct irqaction **pp = p;
 423                         p = &action->next;
 424                         if (action->dev_id != dev_id)
 425                                 continue;
 426
 427                         /* Found - now remove it from the list of entries.  */
 428                         *pp = action->next;
 429                         if (!desc->action) {
 430                                 desc->status |= IRQ_DISABLED;
 431                                 desc->handler->shutdown(irq);
 432                         }
 433                         spin_unlock_irqrestore(&desc->lock,flags);
 434
 435 #ifdef CONFIG_SMP
 436                         /* Wait to make sure it's not being used on
 437                            another CPU.  */
 438                         while (desc->status & IRQ_INPROGRESS)
 439                                 barrier();
 440 #endif
 441                         kfree(action);
 442                         return;
 443                 }
 444                 printk(KERN_ERR "Trying to free free IRQ%d\n",irq);
 445                 spin_unlock_irqrestore(&desc->lock,flags);
 446                 return;
 447         }
 448 }
 449
 450 EXPORT_SYMBOL(free_irq);
 451
 452 int
 453 show_interrupts(struct seq_file *p, void *v)
 454 {
 455 #ifdef CONFIG_SMP
 456         int j;
 457 #endif
 458         int i = *(loff_t *) v;
 459         struct irqaction * action;
 460         unsigned long flags;
 461
 462 #ifdef CONFIG_SMP
 463         if (i == 0) {
 464                 seq_puts(p, "           ");
 465                 for (i = 0; i < NR_CPUS; i++)
 466                         if (cpu_online(i))
 467                                 seq_printf(p, "CPU%d       ", i);
 468                 seq_putc(p, '\n');
 469         }
 470 #endif
 471
 472         if (i < ACTUAL_NR_IRQS) {
 473                 spin_lock_irqsave(&irq_desc[i].lock, flags);
 474                 action = irq_desc[i].action;
 475                 if (!action)
 476                         goto unlock;
 477                 seq_printf(p, "%3d: ",i);
 478 #ifndef CONFIG_SMP
 479                 seq_printf(p, "%10u ", kstat_irqs(i));
 480 #else
 481                 for (j = 0; j < NR_CPUS; j++)
 482                         if (cpu_online(j))
 483                                 seq_printf(p, "%10u ", kstat_cpu(j).irqs[i]);
 484 #endif
 485                 seq_printf(p, " %14s", irq_desc[i].handler->typename);
 486                 seq_printf(p, "  %c%s",
 487                         (action->flags & SA_INTERRUPT)?'+':' ',
 488                         action->name);
 489
 490                 for (action=action->next; action; action = action->next) {
 491                         seq_printf(p, ", %c%s",
 492                                   (action->flags & SA_INTERRUPT)?'+':' ',
 493                                    action->name);
 494                 }
 495
 496                 seq_putc(p, '\n');
 497 unlock:
 498                 spin_unlock_irqrestore(&irq_desc[i].lock, flags);
 499         } else if (i == ACTUAL_NR_IRQS) {
 500 #ifdef CONFIG_SMP
 501                 seq_puts(p, "IPI: ");
 502                 for (i = 0; i < NR_CPUS; i++)
 503                         if (cpu_online(i))
 504                                 seq_printf(p, "%10lu ", cpu_data[i].ipi_count);
 505                 seq_putc(p, '\n');
 506 #endif
 507                 seq_printf(p, "ERR: %10lu\n", irq_err_count);
 508         }
 509         return 0;
 510 }
 511
 512
 513 /*
 514  * handle_irq handles all normal device IRQ's (the special
 515  * SMP cross-CPU interrupts have their own specific
 516  * handlers).
 517  */
 518
 519 #define MAX_ILLEGAL_IRQS 16
 520
 521 void
 522 handle_irq(int irq, struct pt_regs * regs)
 523 {
 524         /*
 525          * We ack quickly, we don't want the irq controller
 526          * thinking we're snobs just because some other CPU has
 527          * disabled global interrupts (we have already done the
 528          * INT_ACK cycles, it's too late to try to pretend to the
 529          * controller that we aren't taking the interrupt).
 530          *
 531          * 0 return value means that this irq is already being
 532          * handled by some other CPU. (or is disabled)
 533          */
 534         int cpu = smp_processor_id();
 535         irq_desc_t *desc = irq_desc + irq;
 536         struct irqaction * action;
 537         unsigned int status;
 538         static unsigned int illegal_count=0;
 539
 540         if ((unsigned) irq > ACTUAL_NR_IRQS && illegal_count < MAX_ILLEGAL_IRQS ) {
 541                 irq_err_count++;
 542                 illegal_count++;
 543                 printk(KERN_CRIT "device_interrupt: invalid interrupt %d\n",
 544                        irq);
 545                 return;
 546         }
 547
 548         irq_enter();
 549         kstat_cpu(cpu).irqs[irq]++;
 550         spin_lock_irq(&desc->lock); /* mask also the higher prio events */
 551         desc->handler->ack(irq);
 552         /*
 553          * REPLAY is when Linux resends an IRQ that was dropped earlier.
 554          * WAITING is used by probe to mark irqs that are being tested.
 555          */
 556         status = desc->status & ~(IRQ_REPLAY | IRQ_WAITING);
 557         status |= IRQ_PENDING; /* we _want_ to handle it */
 558
 559         /*
 560          * If the IRQ is disabled for whatever reason, we cannot
 561          * use the action we have.
 562          */
 563         action = NULL;
 564         if (!(status & (IRQ_DISABLED | IRQ_INPROGRESS))) {
 565                 action = desc->action;
 566                 status &= ~IRQ_PENDING; /* we commit to handling */
 567                 status |= IRQ_INPROGRESS; /* we are handling it */
 568         }
 569         desc->status = status;
 570
 571         /*
 572          * If there is no IRQ handler or it was disabled, exit early.
 573          * Since we set PENDING, if another processor is handling
 574          * a different instance of this same irq, the other processor
 575          * will take care of it.
 576          */
 577         if (!action)
 578                 goto out;
 579
 580         /*
 581          * Edge triggered interrupts need to remember pending events.
 582          * This applies to any hw interrupts that allow a second
 583          * instance of the same irq to arrive while we are in handle_irq
 584          * or in the handler. But the code here only handles the _second_
 585          * instance of the irq, not the third or fourth. So it is mostly
 586          * useful for irq hardware that does not mask cleanly in an
 587          * SMP environment.
 588          */
 589         for (;;) {
 590                 spin_unlock(&desc->lock);
 591                 handle_IRQ_event(irq, regs, action);
 592                 spin_lock(&desc->lock);
 593
 594                 if (!(desc->status & IRQ_PENDING)
 595                     || (desc->status & IRQ_LEVEL))
 596                         break;
 597                 desc->status &= ~IRQ_PENDING;
 598         }
 599         desc->status &= ~IRQ_INPROGRESS;
 600 out:
 601         /*
 602          * The ->end() handler has to deal with interrupts which got
 603          * disabled while the handler was running.
 604          */
 605         desc->handler->end(irq);
 606         spin_unlock(&desc->lock);
 607
 608         irq_exit();
 609 }
 610
 611 /*
 612  * IRQ autodetection code..
 613  *
 614  * This depends on the fact that any interrupt that
 615  * comes in on to an unassigned handler will get stuck
 616  * with "IRQ_WAITING" cleared and the interrupt
 617  * disabled.
 618  */
 619 unsigned long
 620 probe_irq_on(void)
 621 {
 622         int i;
 623         irq_desc_t *desc;
 624         unsigned long delay;
 625         unsigned long val;
 626
 627         /* Something may have generated an irq long ago and we want to
 628            flush such a longstanding irq before considering it as spurious. */
 629         for (i = NR_IRQS-1; i >= 0; i--) {
 630                 desc = irq_desc + i;
 631
 632                 spin_lock_irq(&desc->lock);
 633                 if (!irq_desc[i].action)
 634                         irq_desc[i].handler->startup(i);
 635                 spin_unlock_irq(&desc->lock);
 636         }
 637
 638         /* Wait for longstanding interrupts to trigger. */
 639         for (delay = jiffies + HZ/50; time_after(delay, jiffies); )
 640                 /* about 20ms delay */ barrier();
 641
 642         /* enable any unassigned irqs (we must startup again here because
 643            if a longstanding irq happened in the previous stage, it may have
 644            masked itself) first, enable any unassigned irqs. */
 645         for (i = NR_IRQS-1; i >= 0; i--) {
 646                 desc = irq_desc + i;
 647
 648                 spin_lock_irq(&desc->lock);
 649                 if (!desc->action) {
 650                         desc->status |= IRQ_AUTODETECT | IRQ_WAITING;
 651                         if (desc->handler->startup(i))
 652                                 desc->status |= IRQ_PENDING;
 653                 }
 654                 spin_unlock_irq(&desc->lock);
 655         }
 656
 657         /*
 658          * Wait for spurious interrupts to trigger
 659          */
 660         for (delay = jiffies + HZ/10; time_after(delay, jiffies); )
 661                 /* about 100ms delay */ barrier();
 662
 663         /*
 664          * Now filter out any obviously spurious interrupts
 665          */
 666         val = 0;
 667         for (i=0; i<NR_IRQS; i++) {
 668                 irq_desc_t *desc = irq_desc + i;
 669                 unsigned int status;
 670
 671                 spin_lock_irq(&desc->lock);
 672                 status = desc->status;
 673
 674                 if (status & IRQ_AUTODETECT) {
 675                         /* It triggered already - consider it spurious. */
 676                         if (!(status & IRQ_WAITING)) {
 677                                 desc->status = status & ~IRQ_AUTODETECT;
 678                                 desc->handler->shutdown(i);
 679                         } else
 680                                 if (i < 32)
 681                                         val |= 1 << i;
 682                 }
 683                 spin_unlock_irq(&desc->lock);
 684         }
 685
 686         return val;
 687 }
 688
 689 EXPORT_SYMBOL(probe_irq_on);
 690
 691 /*
 692  * Return a mask of triggered interrupts (this
 693  * can handle only legacy ISA interrupts).
 694  */
 695 unsigned int
 696 probe_irq_mask(unsigned long val)
 697 {
 698         int i;
 699         unsigned int mask;
 700
 701         mask = 0;
 702         for (i = 0; i < NR_IRQS; i++) {
 703                 irq_desc_t *desc = irq_desc + i;
 704                 unsigned int status;
 705
 706                 spin_lock_irq(&desc->lock);
 707                 status = desc->status;
 708
 709                 if (status & IRQ_AUTODETECT) {
 710                         /* We only react to ISA interrupts */
 711                         if (!(status & IRQ_WAITING)) {
 712                                 if (i < 16)
 713                                         mask |= 1 << i;
 714                         }
 715
 716                         desc->status = status & ~IRQ_AUTODETECT;
 717                         desc->handler->shutdown(i);
 718                 }
 719                 spin_unlock_irq(&desc->lock);
 720         }
 721
 722         return mask & val;
 723 }
 724
 725 /*
 726  * Get the result of the IRQ probe.. A negative result means that
 727  * we have several candidates (but we return the lowest-numbered
 728  * one).
 729  */
 730
 731 int
 732 probe_irq_off(unsigned long val)
 733 {
 734         int i, irq_found, nr_irqs;
 735
 736         nr_irqs = 0;
 737         irq_found = 0;
 738         for (i=0; i<NR_IRQS; i++) {
 739                 irq_desc_t *desc = irq_desc + i;
 740                 unsigned int status;
 741
 742                 spin_lock_irq(&desc->lock);
 743                 status = desc->status;
 744
 745                 if (status & IRQ_AUTODETECT) {
 746                         if (!(status & IRQ_WAITING)) {
 747                                 if (!nr_irqs)
 748                                         irq_found = i;
 749                                 nr_irqs++;
 750                         }
 751                         desc->status = status & ~IRQ_AUTODETECT;
 752                         desc->handler->shutdown(i);
 753                 }
 754                 spin_unlock_irq(&desc->lock);
 755         }
 756
 757         if (nr_irqs > 1)
 758                 irq_found = -irq_found;
 759         return irq_found;
 760 }
 761
 762 EXPORT_SYMBOL(probe_irq_off);
 763
 764 #ifdef CONFIG_SMP
 765 void synchronize_irq(unsigned int irq)
 766 {
 767         /* is there anything to synchronize with? */
 768         if (!irq_desc[irq].action)
 769                 return;
 770
 771         while (irq_desc[irq].status & IRQ_INPROGRESS)
 772                 barrier();
 773 }
 774 #endif