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IOFilterInterruptEventSource Class Reference

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IOFilterInterruptEventSource

Filtering varient of the $link IOInterruptEventSource.

An interrupt event source that calls the client to determine if a interrupt event needs to be scheduled on the work loop. A filter interrupt event source call's the client in the primary interrupt context, the client can then interrogate its hardware and determine if the interrupt needs to be processed yet.

As the routine is called in the primary interrupt context great care must be taken in the writing of this routine. In general none of the generic IOKit environment is safe to call in this context. We intend this routine to be used by hardware that can interrogate its registers without destroying state. Primarily this variant of event sources will be used by drivers that share interrupts. The filter routine will determine if the interrupt is a real interrupt or a ghost and thus optimise the work thread context switch away.

If you are implementing 'SoftDMA' (or pseudo-DMA), you may not want the I/O Kit to automatically start your interrupt handler routine on your work loop when your filter routine returns true. In this case, you may choose to have your filter routine schedule the work on the work loop itself and then return false. If you do this, the interrupt will not be disabled in hardware and you could receive additional primary interrupts before your work loop–level service routine completes. Because this scheme has implications for synchronization between your filter routine and your interrupt service routine, you should avoid doing this unless your driver requires SoftDMA.

CAUTION: Called in primary interrupt context, if you need to disable interrupt to guard you registers against an unexpected call then it is better to use a straight IOInterruptEventSource and its secondary interrupt delivery mechanism.

Inheritance


Not Applicable

Conforms To


Not Applicable

Import Statement


Not Applicable

Objective-C

@import Kernel;

Availability


Available in OS X v10.0 and later.
  • Override $link IOInterruptEventSource::disableInterruptOccurred to make a filter callout.

    Declaration

    C++

    virtual void disableInterruptOccurred( void *self, IOService *prov, int ind);

  • Factor method to create and initialise an IOFilterInterruptEventSource. See $link init.

    Declaration

    C++

    static IOFilterInterruptEventSource * filterInterruptEventSource( OSObject *owner, IOInterruptEventSource::Action action, Filter filter, IOService *provider, int intIndex = 0);

    Parameters

    owner

    Owner/client of this event source.

    action

    'C' Function to call when something happens.

    filter

    'C' Function to call when interrupt occurs.

    provider

    Service that provides interrupts.

    intIndex

    Defaults to 0.

    Return Value

    a new event source if succesful, 0 otherwise.

  • Get'ter for filterAction variable.

    Declaration

    C++

    virtual Filter getFilterAction() const;

    Return Value

    value of filterAction.

  • Primary initialiser for the IOFilterInterruptEventSource class.

    Declaration

    C++

    virtual bool init( OSObject *owner, IOInterruptEventSource::Action action, Filter filter, IOService *provider, int intIndex = 0);

    Parameters

    owner

    Owner/client of this event source.

    action

    'C' Function to call when something happens.

    filter

    'C' Function to call in primary interrupt context.

    provider

    Service that provides interrupts.

    intIndex

    Interrupt source within provider. Defaults to 0.

    Return Value

    true if the inherited classes and this instance initialise successfully.

  • Override $link IOInterruptEventSource::normalInterruptOccured to make a filter callout.

    Declaration

    C++

    virtual void normalInterruptOccurred( void *self, IOService *prov, int ind);

  • Cause the work loop to schedule the action.

    Declaration

    C++

    virtual void signalInterrupt();

    Discussion

    Cause the work loop to schedule the interrupt action even if the filter routine returns 'false'. Note well the interrupting condition MUST be cleared from the hardware otherwise an infinite process interrupt loop will occur. Use this function when SoftDMA is desired. See $link IOFilterInterruptSource::Filter

Callbacks

  • Declaration

    C++

    typedef bool ( * Filter )( OSObject *, IOFilterInterruptEventSource *);

    Parameters

    owner

    Pointer to the owning/client instance.

    sender

    Where is the interrupt comming from.

    Return Value

    false if this interrupt can be ignored.

    Discussion

    C Function pointer to a routine to call when an interrupt occurs.

    Import Statement

    Objective-C

    #include <IOFilterInterruptEventSource.h>;

    Availability

    Available in OS X v10.0 through OS X v10.5.

Constants

  • Declaration

    CPlusPlus

    #define IOFilterInterruptAction IOFilterInterruptEventSource::Filter

    Constants

    • IOFilterInterruptAction

      IOFilterInterruptAction

      Backward compatibilty define for the old non-class scoped type definition. See $link IOFilterInterruptSource::Filter

      Available in OS X v10.0 and later.

  • Data Types

    • Declaration

      C++

      struct ExpansionData { };

      Discussion

      This structure will be used to expand the capablilties of the IOWorkLoop in the future.

    Instance Variables

    • Reserved for future use. (Internal use only)

      Declaration

      C++

      ExpansionData *reserved;

    • Filter callout

      Declaration

      C++

      Filter filterAction;