DESCRIPTION

  Usage
     probe_irq_on() turns on IRQ detection.  It operates by  ena-
     bling  all  interrupts which have no handlers, while keeping
     the handlers for those interrupts NULL.  The  kernel's  gen-
     eric interrupt handling routine will disable these IRQs when
     an interrupt is received on them. probe_irq_on()  adds  each
     of  these  IRQ numbers to a vector which it will return.  It
     waits approximately 100ms for any spurious  interrupts  that
     may  occur, and masks these from its vector; it then returns
     this vector to its caller.

     probe_irq_off() tests  an  internal  list  of  enabled  IRQs
     against  its  irqs  parameter,  which  should  be  the value
     returned by the last probe_irq_on().   This  function  basi-
     cally  detects  which  IRQs have been switched off, and thus
     which ones have received interrupts.

  Example
     This explanation may seem a bit confusing,  so  here  is  an
     example  of code the mythical FUBAR 2000 driver could use to
     probe for IRQs:

          unsigned long irqs;
          int irq;

          irqs = probe_irq_on();

          outb(FB2K_GIVE_ME_AN_INTERRUPT_OR_GIVE_ME_DEATH,
               FB2K_CONTROL_PORT);
            /* the interrupt could take a while to occur */
          udelay(1000);

          irq = probe_irq_off(irqs);

          if (irq == 0) {
               printk("fb2k: could not detect IRQ.\n");
               printk("fb2k: Installation failed.\n");
          } else if (irq == -1) {
               printk("fb2k: multiple IRQs detected.\n");
               printk("fb2k: Installation failed.\n");
          } else {
               fb2k_dev->irq = irq;
               printk("fb2k: using probed IRQ %d.\n", irq);
          }

RETURN VALUE

     probe_irq_on()  returns  a  bitmap  of  all  unhandled  IRQs
     (except  those  which  are  receiving  spurious interrupts).
     This value should only be used as a parameter  to  the  next
     call to probe_irq_off().

     probe_irq_off() returns the IRQ number of  whichever  unhan-
     dled  interrupt  has occurred since the last probe_irq_on().
     If no interrupts have occurred on any of the marked IRQs,  0
     is returned; if interrupts have occurred on more than one of
     these IRQs, -1 is returned.

AVAILABILITY

     Linux 1.2+.  These functions are not available on m68k-based
     machines.

SEE ALSO

     request_irq(9)

     arch/*/kernel/irq.c

AUTHOR

     Neil Moore <amethyst@maxwell.ml.org>

BUGS

     As mentioned above, these functions  are  not  available  on
     m68k-based machines.

     This manpage is way too confusing.