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