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