drivers/misc/dummy-irq.c

   1 /*
   2  * Dummy IRQ handler driver.
   3  *
   4  * This module only registers itself as a handler that is specified to it
   5  * by the 'irq' parameter.
   6  *
   7  * The sole purpose of this module is to help with debugging of systems on
   8  * which spurious IRQs would happen on disabled IRQ vector.
   9  *
  10  * Copyright (C) 2013 Jiri Kosina
  11  */
  12
  13 /*
  14  * This program is free software; you can redistribute it and/or modify it
  15  * under the terms of the GNU General Public License version 2 as published by
  16  * the Free Software Foundation.
  17  */
  18 #include <linux/module.h>
  19 #include <linux/irq.h>
  20 #include <linux/interrupt.h>
  21
  22 static int irq = -1;
  23
  24 static irqreturn_t dummy_interrupt(int irq, void *dev_id)
  25 {
  26         static int count = 0;
  27
  28         if (count == 0) {
  29                 printk(KERN_INFO "dummy-irq: interrupt occurred on IRQ %d\n",
  30                                 irq);
  31                 count++;
  32         }
  33
  34         return IRQ_NONE;
  35 }
  36
  37 static int __init dummy_irq_init(void)
  38 {
  39         if (irq < 0) {
  40                 printk(KERN_ERR "dummy-irq: no IRQ given.  Use irq=N\n");
  41                 return -EIO;
  42         }
  43         if (request_irq(irq, &dummy_interrupt, IRQF_SHARED, "dummy_irq", &irq)) {
  44                 printk(KERN_ERR "dummy-irq: cannot register IRQ %d\n", irq);
  45                 return -EIO;
  46         }
  47         printk(KERN_INFO "dummy-irq: registered for IRQ %d\n", irq);
  48         return 0;
  49 }
  50
  51 static void __exit dummy_irq_exit(void)
  52 {
  53         printk(KERN_INFO "dummy-irq unloaded\n");
  54         free_irq(irq, &irq);
  55 }
  56
  57 module_init(dummy_irq_init);
  58 module_exit(dummy_irq_exit);
  59
  60 MODULE_LICENSE("GPL");
  61 MODULE_AUTHOR("Jiri Kosina");
  62 module_param(irq, uint, 0444);
  63 MODULE_PARM_DESC(irq, "The IRQ to register for");
  64 MODULE_DESCRIPTION("Dummy IRQ handler driver");