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