IOFilterInterruptEventSource

Overview

Filtering varient of the $link IOInterruptEventSource.

Discussion

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.

Functions

disableInterruptOccurred

Override $link IOInterruptEventSource::disableInterruptOccurred to make a filter callout.

filterInterruptEventSource

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

getFilterAction

Get'ter for filterAction variable.

init

Primary initialiser for the IOFilterInterruptEventSource class.

normalInterruptOccurred

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

signalInterrupt

Cause the work loop to schedule the action.

Override $link IOInterruptEventSource::disableInterruptOccurred to make a filter callout.

public

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

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

public

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

Parameters

Return Value

a new event source if succesful, 0 otherwise.

Get'ter for filterAction variable.

public

virtual Filter getFilterAction() const; 

Return Value

value of filterAction.

Primary initialiser for the IOFilterInterruptEventSource class.

public

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

Parameters

Return Value

true if the inherited classes and this instance initialise successfully.

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

public

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

Cause the work loop to schedule the action.

public

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

Typedefs

Filter

public

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

Parameters

Return Value

false if this interrupt can be ignored.

Discussion

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

Structs and Unions

ExpansionData

protected

struct ExpansionData {
}; 

Discussion

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

Member Data

filterAction

reserved

protected

Filter filterAction; 

Discussion

Filter callout

protected

ExpansionData *reserved; 

Discussion

Reserved for future use. (Internal use only)

Macro Definitions

IOFilterInterruptAction

#define IOFilterInterruptAction IOFilterInterruptEventSource::Filter 

Discussion

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

Last Updated: 2009-10-14