kernel/irq/manage.c

   1 /*
   2  * linux/kernel/irq/manage.c
   3  *
   4  * Copyright (C) 1992, 1998-2006 Linus Torvalds, Ingo Molnar
   5  * Copyright (C) 2005-2006 Thomas Gleixner
   6  *
   7  * This file contains driver APIs to the irq subsystem.
   8  */
   9
  10 #include <linux/irq.h>
  11 #include <linux/module.h>
  12 #include <linux/random.h>
  13 #include <linux/interrupt.h>
  14 #include <linux/slab.h>
  15
  16 #include "internals.h"
  17
  18 #if defined(CONFIG_SMP) && defined(CONFIG_GENERIC_HARDIRQS)
  19 cpumask_var_t irq_default_affinity;
  20
  21 /**
  22  *      synchronize_irq - wait for pending IRQ handlers (on other CPUs)
  23  *      @irq: interrupt number to wait for
  24  *
  25  *      This function waits for any pending IRQ handlers for this interrupt
  26  *      to complete before returning. If you use this function while
  27  *      holding a resource the IRQ handler may need you will deadlock.
  28  *
  29  *      This function may be called - with care - from IRQ context.
  30  */
  31 void synchronize_irq(unsigned int irq)
  32 {
  33         struct irq_desc *desc = irq_to_desc(irq);
  34         unsigned int status;
  35
  36         if (!desc)
  37                 return;
  38
  39         do {
  40                 unsigned long flags;
  41
  42                 /*
  43                  * Wait until we're out of the critical section.  This might
  44                  * give the wrong answer due to the lack of memory barriers.
  45                  */
  46                 while (desc->status & IRQ_INPROGRESS)
  47                         cpu_relax();
  48
  49                 /* Ok, that indicated we're done: double-check carefully. */
  50                 spin_lock_irqsave(&desc->lock, flags);
  51                 status = desc->status;
  52                 spin_unlock_irqrestore(&desc->lock, flags);
  53
  54                 /* Oops, that failed? */
  55         } while (status & IRQ_INPROGRESS);
  56 }
  57 EXPORT_SYMBOL(synchronize_irq);
  58
  59 /**
  60  *      irq_can_set_affinity - Check if the affinity of a given irq can be set
  61  *      @irq:           Interrupt to check
  62  *
  63  */
  64 int irq_can_set_affinity(unsigned int irq)
  65 {
  66         struct irq_desc *desc = irq_to_desc(irq);
  67
  68         if (CHECK_IRQ_PER_CPU(desc->status) || !desc->chip ||
  69             !desc->chip->set_affinity)
  70                 return 0;
  71
  72         return 1;
  73 }
  74
  75 /**
  76  *      irq_set_affinity - Set the irq affinity of a given irq
  77  *      @irq:           Interrupt to set affinity
  78  *      @cpumask:       cpumask
  79  *
  80  */
  81 int irq_set_affinity(unsigned int irq, const struct cpumask *cpumask)
  82 {
  83         struct irq_desc *desc = irq_to_desc(irq);
  84         unsigned long flags;
  85
  86         if (!desc->chip->set_affinity)
  87                 return -EINVAL;
  88
  89         spin_lock_irqsave(&desc->lock, flags);
  90
  91 #ifdef CONFIG_GENERIC_PENDING_IRQ
  92         if (desc->status & IRQ_MOVE_PCNTXT || desc->status & IRQ_DISABLED) {
  93                 cpumask_copy(desc->affinity, cpumask);
  94                 desc->chip->set_affinity(irq, cpumask);
  95         } else {
  96                 desc->status |= IRQ_MOVE_PENDING;
  97                 cpumask_copy(desc->pending_mask, cpumask);
  98         }
  99 #else
 100         cpumask_copy(desc->affinity, cpumask);
 101         desc->chip->set_affinity(irq, cpumask);
 102 #endif
 103         desc->status |= IRQ_AFFINITY_SET;
 104         spin_unlock_irqrestore(&desc->lock, flags);
 105         return 0;
 106 }
 107
 108 #ifndef CONFIG_AUTO_IRQ_AFFINITY
 109 /*
 110  * Generic version of the affinity autoselector.
 111  */
 112 static int setup_affinity(unsigned int irq, struct irq_desc *desc)
 113 {
 114         if (!irq_can_set_affinity(irq))
 115                 return 0;
 116
 117         /*
 118          * Preserve an userspace affinity setup, but make sure that
 119          * one of the targets is online.
 120          */
 121         if (desc->status & (IRQ_AFFINITY_SET | IRQ_NO_BALANCING)) {
 122                 if (cpumask_any_and(desc->affinity, cpu_online_mask)
 123                     < nr_cpu_ids)
 124                         goto set_affinity;
 125                 else
 126                         desc->status &= ~IRQ_AFFINITY_SET;
 127         }
 128
 129         cpumask_and(desc->affinity, cpu_online_mask, irq_default_affinity);
 130 set_affinity:
 131         desc->chip->set_affinity(irq, desc->affinity);
 132
 133         return 0;
 134 }
 135 #else
 136 static inline int setup_affinity(unsigned int irq, struct irq_desc *d)
 137 {
 138         return irq_select_affinity(irq);
 139 }
 140 #endif
 141
 142 /*
 143  * Called when affinity is set via /proc/irq
 144  */
 145 int irq_select_affinity_usr(unsigned int irq)
 146 {
 147         struct irq_desc *desc = irq_to_desc(irq);
 148         unsigned long flags;
 149         int ret;
 150
 151         spin_lock_irqsave(&desc->lock, flags);
 152         ret = setup_affinity(irq, desc);
 153         spin_unlock_irqrestore(&desc->lock, flags);
 154
 155         return ret;
 156 }
 157
 158 #else
 159 static inline int setup_affinity(unsigned int irq, struct irq_desc *desc)
 160 {
 161         return 0;
 162 }
 163 #endif
 164
 165 void __disable_irq(struct irq_desc *desc, unsigned int irq, bool suspend)
 166 {
 167         if (suspend) {
 168                 if (!desc->action || (desc->action->flags & IRQF_TIMER))
 169                         return;
 170                 desc->status |= IRQ_SUSPENDED;
 171         }
 172
 173         if (!desc->depth++) {
 174                 desc->status |= IRQ_DISABLED;
 175                 desc->chip->disable(irq);
 176         }
 177 }
 178
 179 /**
 180  *      disable_irq_nosync - disable an irq without waiting
 181  *      @irq: Interrupt to disable
 182  *
 183  *      Disable the selected interrupt line.  Disables and Enables are
 184  *      nested.
 185  *      Unlike disable_irq(), this function does not ensure existing
 186  *      instances of the IRQ handler have completed before returning.
 187  *
 188  *      This function may be called from IRQ context.
 189  */
 190 void disable_irq_nosync(unsigned int irq)
 191 {
 192         struct irq_desc *desc = irq_to_desc(irq);
 193         unsigned long flags;
 194
 195         if (!desc)
 196                 return;
 197
 198         spin_lock_irqsave(&desc->lock, flags);
 199         __disable_irq(desc, irq, false);
 200         spin_unlock_irqrestore(&desc->lock, flags);
 201 }
 202 EXPORT_SYMBOL(disable_irq_nosync);
 203
 204 /**
 205  *      disable_irq - disable an irq and wait for completion
 206  *      @irq: Interrupt to disable
 207  *
 208  *      Disable the selected interrupt line.  Enables and Disables are
 209  *      nested.
 210  *      This function waits for any pending IRQ handlers for this interrupt
 211  *      to complete before returning. If you use this function while
 212  *      holding a resource the IRQ handler may need you will deadlock.
 213  *
 214  *      This function may be called - with care - from IRQ context.
 215  */
 216 void disable_irq(unsigned int irq)
 217 {
 218         struct irq_desc *desc = irq_to_desc(irq);
 219
 220         if (!desc)
 221                 return;
 222
 223         disable_irq_nosync(irq);
 224         if (desc->action)
 225                 synchronize_irq(irq);
 226 }
 227 EXPORT_SYMBOL(disable_irq);
 228
 229 void __enable_irq(struct irq_desc *desc, unsigned int irq, bool resume)
 230 {
 231         if (resume)
 232                 desc->status &= ~IRQ_SUSPENDED;
 233
 234         switch (desc->depth) {
 235         case 0:
 236  err_out:
 237                 WARN(1, KERN_WARNING "Unbalanced enable for IRQ %d\n", irq);
 238                 break;
 239         case 1: {
 240                 unsigned int status = desc->status & ~IRQ_DISABLED;
 241
 242                 if (desc->status & IRQ_SUSPENDED)
 243                         goto err_out;
 244                 /* Prevent probing on this irq: */
 245                 desc->status = status | IRQ_NOPROBE;
 246                 check_irq_resend(desc, irq);
 247                 /* fall-through */
 248         }
 249         default:
 250                 desc->depth--;
 251         }
 252 }
 253
 254 /**
 255  *      enable_irq - enable handling of an irq
 256  *      @irq: Interrupt to enable
 257  *
 258  *      Undoes the effect of one call to disable_irq().  If this
 259  *      matches the last disable, processing of interrupts on this
 260  *      IRQ line is re-enabled.
 261  *
 262  *      This function may be called from IRQ context.
 263  */
 264 void enable_irq(unsigned int irq)
 265 {
 266         struct irq_desc *desc = irq_to_desc(irq);
 267         unsigned long flags;
 268
 269         if (!desc)
 270                 return;
 271
 272         spin_lock_irqsave(&desc->lock, flags);
 273         __enable_irq(desc, irq, false);
 274         spin_unlock_irqrestore(&desc->lock, flags);
 275 }
 276 EXPORT_SYMBOL(enable_irq);
 277
 278 static int set_irq_wake_real(unsigned int irq, unsigned int on)
 279 {
 280         struct irq_desc *desc = irq_to_desc(irq);
 281         int ret = -ENXIO;
 282
 283         if (desc->chip->set_wake)
 284                 ret = desc->chip->set_wake(irq, on);
 285
 286         return ret;
 287 }
 288
 289 /**
 290  *      set_irq_wake - control irq power management wakeup
 291  *      @irq:   interrupt to control
 292  *      @on:    enable/disable power management wakeup
 293  *
 294  *      Enable/disable power management wakeup mode, which is
 295  *      disabled by default.  Enables and disables must match,
 296  *      just as they match for non-wakeup mode support.
 297  *
 298  *      Wakeup mode lets this IRQ wake the system from sleep
 299  *      states like "suspend to RAM".
 300  */
 301 int set_irq_wake(unsigned int irq, unsigned int on)
 302 {
 303         struct irq_desc *desc = irq_to_desc(irq);
 304         unsigned long flags;
 305         int ret = 0;
 306
 307         /* wakeup-capable irqs can be shared between drivers that
 308          * don't need to have the same sleep mode behaviors.
 309          */
 310         spin_lock_irqsave(&desc->lock, flags);
 311         if (on) {
 312                 if (desc->wake_depth++ == 0) {
 313                         ret = set_irq_wake_real(irq, on);
 314                         if (ret)
 315                                 desc->wake_depth = 0;
 316                         else
 317                                 desc->status |= IRQ_WAKEUP;
 318                 }
 319         } else {
 320                 if (desc->wake_depth == 0) {
 321                         WARN(1, "Unbalanced IRQ %d wake disable\n", irq);
 322                 } else if (--desc->wake_depth == 0) {
 323                         ret = set_irq_wake_real(irq, on);
 324                         if (ret)
 325                                 desc->wake_depth = 1;
 326                         else
 327                                 desc->status &= ~IRQ_WAKEUP;
 328                 }
 329         }
 330
 331         spin_unlock_irqrestore(&desc->lock, flags);
 332         return ret;
 333 }
 334 EXPORT_SYMBOL(set_irq_wake);
 335
 336 /*
 337  * Internal function that tells the architecture code whether a
 338  * particular irq has been exclusively allocated or is available
 339  * for driver use.
 340  */
 341 int can_request_irq(unsigned int irq, unsigned long irqflags)
 342 {
 343         struct irq_desc *desc = irq_to_desc(irq);
 344         struct irqaction *action;
 345
 346         if (!desc)
 347                 return 0;
 348
 349         if (desc->status & IRQ_NOREQUEST)
 350                 return 0;
 351
 352         action = desc->action;
 353         if (action)
 354                 if (irqflags & action->flags & IRQF_SHARED)
 355                         action = NULL;
 356
 357         return !action;
 358 }
 359
 360 void compat_irq_chip_set_default_handler(struct irq_desc *desc)
 361 {
 362         /*
 363          * If the architecture still has not overriden
 364          * the flow handler then zap the default. This
 365          * should catch incorrect flow-type setting.
 366          */
 367         if (desc->handle_irq == &handle_bad_irq)
 368                 desc->handle_irq = NULL;
 369 }
 370
 371 int __irq_set_trigger(struct irq_desc *desc, unsigned int irq,
 372                 unsigned long flags)
 373 {
 374         int ret;
 375         struct irq_chip *chip = desc->chip;
 376
 377         if (!chip || !chip->set_type) {
 378                 /*
 379                  * IRQF_TRIGGER_* but the PIC does not support multiple
 380                  * flow-types?
 381                  */
 382                 pr_debug("No set_type function for IRQ %d (%s)\n", irq,
 383                                 chip ? (chip->name ? : "unknown") : "unknown");
 384                 return 0;
 385         }
 386
 387         /* caller masked out all except trigger mode flags */
 388         ret = chip->set_type(irq, flags);
 389
 390         if (ret)
 391                 pr_err("setting trigger mode %d for irq %u failed (%pF)\n",
 392                                 (int)flags, irq, chip->set_type);
 393         else {
 394                 if (flags & (IRQ_TYPE_LEVEL_LOW | IRQ_TYPE_LEVEL_HIGH))
 395                         flags |= IRQ_LEVEL;
 396                 /* note that IRQF_TRIGGER_MASK == IRQ_TYPE_SENSE_MASK */
 397                 desc->status &= ~(IRQ_LEVEL | IRQ_TYPE_SENSE_MASK);
 398                 desc->status |= flags;
 399         }
 400
 401         return ret;
 402 }
 403
 404 /*
 405  * Internal function to register an irqaction - typically used to
 406  * allocate special interrupts that are part of the architecture.
 407  */
 408 static int
 409 __setup_irq(unsigned int irq, struct irq_desc *desc, struct irqaction *new)
 410 {
 411         struct irqaction *old, **old_ptr;
 412         const char *old_name = NULL;
 413         unsigned long flags;
 414         int shared = 0;
 415         int ret;
 416
 417         if (!desc)
 418                 return -EINVAL;
 419
 420         if (desc->chip == &no_irq_chip)
 421                 return -ENOSYS;
 422         /*
 423          * Some drivers like serial.c use request_irq() heavily,
 424          * so we have to be careful not to interfere with a
 425          * running system.
 426          */
 427         if (new->flags & IRQF_SAMPLE_RANDOM) {
 428                 /*
 429                  * This function might sleep, we want to call it first,
 430                  * outside of the atomic block.
 431                  * Yes, this might clear the entropy pool if the wrong
 432                  * driver is attempted to be loaded, without actually
 433                  * installing a new handler, but is this really a problem,
 434                  * only the sysadmin is able to do this.
 435                  */
 436                 rand_initialize_irq(irq);
 437         }
 438
 439         /*
 440          * The following block of code has to be executed atomically
 441          */
 442         spin_lock_irqsave(&desc->lock, flags);
 443         old_ptr = &desc->action;
 444         old = *old_ptr;
 445         if (old) {
 446                 /*
 447                  * Can't share interrupts unless both agree to and are
 448                  * the same type (level, edge, polarity). So both flag
 449                  * fields must have IRQF_SHARED set and the bits which
 450                  * set the trigger type must match.
 451                  */
 452                 if (!((old->flags & new->flags) & IRQF_SHARED) ||
 453                     ((old->flags ^ new->flags) & IRQF_TRIGGER_MASK)) {
 454                         old_name = old->name;
 455                         goto mismatch;
 456                 }
 457
 458 #if defined(CONFIG_IRQ_PER_CPU)
 459                 /* All handlers must agree on per-cpuness */
 460                 if ((old->flags & IRQF_PERCPU) !=
 461                     (new->flags & IRQF_PERCPU))
 462                         goto mismatch;
 463 #endif
 464
 465                 /* add new interrupt at end of irq queue */
 466                 do {
 467                         old_ptr = &old->next;
 468                         old = *old_ptr;
 469                 } while (old);
 470                 shared = 1;
 471         }
 472
 473         if (!shared) {
 474                 irq_chip_set_defaults(desc->chip);
 475
 476                 /* Setup the type (level, edge polarity) if configured: */
 477                 if (new->flags & IRQF_TRIGGER_MASK) {
 478                         ret = __irq_set_trigger(desc, irq,
 479                                         new->flags & IRQF_TRIGGER_MASK);
 480
 481                         if (ret) {
 482                                 spin_unlock_irqrestore(&desc->lock, flags);
 483                                 return ret;
 484                         }
 485                 } else
 486                         compat_irq_chip_set_default_handler(desc);
 487 #if defined(CONFIG_IRQ_PER_CPU)
 488                 if (new->flags & IRQF_PERCPU)
 489                         desc->status |= IRQ_PER_CPU;
 490 #endif
 491
 492                 desc->status &= ~(IRQ_AUTODETECT | IRQ_WAITING |
 493                                   IRQ_INPROGRESS | IRQ_SPURIOUS_DISABLED);
 494
 495                 if (!(desc->status & IRQ_NOAUTOEN)) {
 496                         desc->depth = 0;
 497                         desc->status &= ~IRQ_DISABLED;
 498                         desc->chip->startup(irq);
 499                 } else
 500                         /* Undo nested disables: */
 501                         desc->depth = 1;
 502
 503                 /* Exclude IRQ from balancing if requested */
 504                 if (new->flags & IRQF_NOBALANCING)
 505                         desc->status |= IRQ_NO_BALANCING;
 506
 507                 /* Set default affinity mask once everything is setup */
 508                 setup_affinity(irq, desc);
 509
 510         } else if ((new->flags & IRQF_TRIGGER_MASK)
 511                         && (new->flags & IRQF_TRIGGER_MASK)
 512                                 != (desc->status & IRQ_TYPE_SENSE_MASK)) {
 513                 /* hope the handler works with the actual trigger mode... */
 514                 pr_warning("IRQ %d uses trigger mode %d; requested %d\n",
 515                                 irq, (int)(desc->status & IRQ_TYPE_SENSE_MASK),
 516                                 (int)(new->flags & IRQF_TRIGGER_MASK));
 517         }
 518
 519         *old_ptr = new;
 520
 521         /* Reset broken irq detection when installing new handler */
 522         desc->irq_count = 0;
 523         desc->irqs_unhandled = 0;
 524
 525         /*
 526          * Check whether we disabled the irq via the spurious handler
 527          * before. Reenable it and give it another chance.
 528          */
 529         if (shared && (desc->status & IRQ_SPURIOUS_DISABLED)) {
 530                 desc->status &= ~IRQ_SPURIOUS_DISABLED;
 531                 __enable_irq(desc, irq, false);
 532         }
 533
 534         spin_unlock_irqrestore(&desc->lock, flags);
 535
 536         new->irq = irq;
 537         register_irq_proc(irq, desc);
 538         new->dir = NULL;
 539         register_handler_proc(irq, new);
 540
 541         return 0;
 542
 543 mismatch:
 544 #ifdef CONFIG_DEBUG_SHIRQ
 545         if (!(new->flags & IRQF_PROBE_SHARED)) {
 546                 printk(KERN_ERR "IRQ handler type mismatch for IRQ %d\n", irq);
 547                 if (old_name)
 548                         printk(KERN_ERR "current handler: %s\n", old_name);
 549                 dump_stack();
 550         }
 551 #endif
 552         spin_unlock_irqrestore(&desc->lock, flags);
 553         return -EBUSY;
 554 }
 555
 556 /**
 557  *      setup_irq - setup an interrupt
 558  *      @irq: Interrupt line to setup
 559  *      @act: irqaction for the interrupt
 560  *
 561  * Used to statically setup interrupts in the early boot process.
 562  */
 563 int setup_irq(unsigned int irq, struct irqaction *act)
 564 {
 565         struct irq_desc *desc = irq_to_desc(irq);
 566
 567         return __setup_irq(irq, desc, act);
 568 }
 569 EXPORT_SYMBOL_GPL(setup_irq);
 570
 571  /*
 572  * Internal function to unregister an irqaction - used to free
 573  * regular and special interrupts that are part of the architecture.
 574  */
 575 static struct irqaction *__free_irq(unsigned int irq, void *dev_id)
 576 {
 577         struct irq_desc *desc = irq_to_desc(irq);
 578         struct irqaction *action, **action_ptr;
 579         unsigned long flags;
 580
 581         WARN(in_interrupt(), "Trying to free IRQ %d from IRQ context!\n", irq);
 582
 583         if (!desc)
 584                 return NULL;
 585
 586         spin_lock_irqsave(&desc->lock, flags);
 587
 588         /*
 589          * There can be multiple actions per IRQ descriptor, find the right
 590          * one based on the dev_id:
 591          */
 592         action_ptr = &desc->action;
 593         for (;;) {
 594                 action = *action_ptr;
 595
 596                 if (!action) {
 597                         WARN(1, "Trying to free already-free IRQ %d\n", irq);
 598                         spin_unlock_irqrestore(&desc->lock, flags);
 599
 600                         return NULL;
 601                 }
 602
 603                 if (action->dev_id == dev_id)
 604                         break;
 605                 action_ptr = &action->next;
 606         }
 607
 608         /* Found it - now remove it from the list of entries: */
 609         *action_ptr = action->next;
 610
 611         /* Currently used only by UML, might disappear one day: */
 612 #ifdef CONFIG_IRQ_RELEASE_METHOD
 613         if (desc->chip->release)
 614                 desc->chip->release(irq, dev_id);
 615 #endif
 616
 617         /* If this was the last handler, shut down the IRQ line: */
 618         if (!desc->action) {
 619                 desc->status |= IRQ_DISABLED;
 620                 if (desc->chip->shutdown)
 621                         desc->chip->shutdown(irq);
 622                 else
 623                         desc->chip->disable(irq);
 624         }
 625         spin_unlock_irqrestore(&desc->lock, flags);
 626
 627         unregister_handler_proc(irq, action);
 628
 629         /* Make sure it's not being used on another CPU: */
 630         synchronize_irq(irq);
 631
 632 #ifdef CONFIG_DEBUG_SHIRQ
 633         /*
 634          * It's a shared IRQ -- the driver ought to be prepared for an IRQ
 635          * event to happen even now it's being freed, so let's make sure that
 636          * is so by doing an extra call to the handler ....
 637          *
 638          * ( We do this after actually deregistering it, to make sure that a
 639          *   'real' IRQ doesn't run in * parallel with our fake. )
 640          */
 641         if (action->flags & IRQF_SHARED) {
 642                 local_irq_save(flags);
 643                 action->handler(irq, dev_id);
 644                 local_irq_restore(flags);
 645         }
 646 #endif
 647         return action;
 648 }
 649
 650 /**
 651  *      remove_irq - free an interrupt
 652  *      @irq: Interrupt line to free
 653  *      @act: irqaction for the interrupt
 654  *
 655  * Used to remove interrupts statically setup by the early boot process.
 656  */
 657 void remove_irq(unsigned int irq, struct irqaction *act)
 658 {
 659         __free_irq(irq, act->dev_id);
 660 }
 661 EXPORT_SYMBOL_GPL(remove_irq);
 662
 663 /**
 664  *      free_irq - free an interrupt allocated with request_irq
 665  *      @irq: Interrupt line to free
 666  *      @dev_id: Device identity to free
 667  *
 668  *      Remove an interrupt handler. The handler is removed and if the
 669  *      interrupt line is no longer in use by any driver it is disabled.
 670  *      On a shared IRQ the caller must ensure the interrupt is disabled
 671  *      on the card it drives before calling this function. The function
 672  *      does not return until any executing interrupts for this IRQ
 673  *      have completed.
 674  *
 675  *      This function must not be called from interrupt context.
 676  */
 677 void free_irq(unsigned int irq, void *dev_id)
 678 {
 679         kfree(__free_irq(irq, dev_id));
 680 }
 681 EXPORT_SYMBOL(free_irq);
 682
 683 /**
 684  *      request_irq - allocate an interrupt line
 685  *      @irq: Interrupt line to allocate
 686  *      @handler: Function to be called when the IRQ occurs
 687  *      @irqflags: Interrupt type flags
 688  *      @devname: An ascii name for the claiming device
 689  *      @dev_id: A cookie passed back to the handler function
 690  *
 691  *      This call allocates interrupt resources and enables the
 692  *      interrupt line and IRQ handling. From the point this
 693  *      call is made your handler function may be invoked. Since
 694  *      your handler function must clear any interrupt the board
 695  *      raises, you must take care both to initialise your hardware
 696  *      and to set up the interrupt handler in the right order.
 697  *
 698  *      Dev_id must be globally unique. Normally the address of the
 699  *      device data structure is used as the cookie. Since the handler
 700  *      receives this value it makes sense to use it.
 701  *
 702  *      If your interrupt is shared you must pass a non NULL dev_id
 703  *      as this is required when freeing the interrupt.
 704  *
 705  *      Flags:
 706  *
 707  *      IRQF_SHARED             Interrupt is shared
 708  *      IRQF_DISABLED   Disable local interrupts while processing
 709  *      IRQF_SAMPLE_RANDOM      The interrupt can be used for entropy
 710  *      IRQF_TRIGGER_*          Specify active edge(s) or level
 711  *
 712  */
 713 int request_irq(unsigned int irq, irq_handler_t handler,
 714                 unsigned long irqflags, const char *devname, void *dev_id)
 715 {
 716         struct irqaction *action;
 717         struct irq_desc *desc;
 718         int retval;
 719
 720         /*
 721          * handle_IRQ_event() always ignores IRQF_DISABLED except for
 722          * the _first_ irqaction (sigh).  That can cause oopsing, but
 723          * the behavior is classified as "will not fix" so we need to
 724          * start nudging drivers away from using that idiom.
 725          */
 726         if ((irqflags & (IRQF_SHARED|IRQF_DISABLED)) ==
 727                                         (IRQF_SHARED|IRQF_DISABLED)) {
 728                 pr_warning(
 729                   "IRQ %d/%s: IRQF_DISABLED is not guaranteed on shared IRQs\n",
 730                         irq, devname);
 731         }
 732
 733 #ifdef CONFIG_LOCKDEP
 734         /*
 735          * Lockdep wants atomic interrupt handlers:
 736          */
 737         irqflags |= IRQF_DISABLED;
 738 #endif
 739         /*
 740          * Sanity-check: shared interrupts must pass in a real dev-ID,
 741          * otherwise we'll have trouble later trying to figure out
 742          * which interrupt is which (messes up the interrupt freeing
 743          * logic etc).
 744          */
 745         if ((irqflags & IRQF_SHARED) && !dev_id)
 746                 return -EINVAL;
 747
 748         desc = irq_to_desc(irq);
 749         if (!desc)
 750                 return -EINVAL;
 751
 752         if (desc->status & IRQ_NOREQUEST)
 753                 return -EINVAL;
 754         if (!handler)
 755                 return -EINVAL;
 756
 757         action = kzalloc(sizeof(struct irqaction), GFP_KERNEL);
 758         if (!action)
 759                 return -ENOMEM;
 760
 761         action->handler = handler;
 762         action->flags = irqflags;
 763         action->name = devname;
 764         action->dev_id = dev_id;
 765
 766         retval = __setup_irq(irq, desc, action);
 767         if (retval)
 768                 kfree(action);
 769
 770 #ifdef CONFIG_DEBUG_SHIRQ
 771         if (!retval && (irqflags & IRQF_SHARED)) {
 772                 /*
 773                  * It's a shared IRQ -- the driver ought to be prepared for it
 774                  * to happen immediately, so let's make sure....
 775                  * We disable the irq to make sure that a 'real' IRQ doesn't
 776                  * run in parallel with our fake.
 777                  */
 778                 unsigned long flags;
 779
 780                 disable_irq(irq);
 781                 local_irq_save(flags);
 782
 783                 handler(irq, dev_id);
 784
 785                 local_irq_restore(flags);
 786                 enable_irq(irq);
 787         }
 788 #endif
 789         return retval;
 790 }
 791 EXPORT_SYMBOL(request_irq);