Overview

Abstract class for all work-loop event sources.

Discussion

The IOEventSource declares the abstract super class that all event sources must inherit from if an IOWorkLoop is to receive events from them.

An event source can represent any event that should cause the work-loop of a device to wake up and perform work. Two examples of event sources are the IOInterruptEventSource which delivers interrupt notifications and IOCommandGate which delivers command requests.

A kernel module can always use the work-loop model for serialising access to anything at all. The IOEventSource is used for communicating events to the work-loop, and the chain of event sources should be used to walk the possible event sources and demultipex them. Note a particular instance of an event source may only be a member of 1 linked list chain. If you need to move it between chains than make sure it is removed from the original chain before attempting to move it.

The IOEventSource makes no attempt to maintain the consitency of it's internal data across multi-threading. It is assumed that the user of these basic tools will protect the data that these objects represent in some sort of device wide instance lock. For example the IOWorkLoop maintains the event chain by handing off change request to its own thread and thus single threading access to its state.

All subclasses of the IOEventSource are expected to implement the checkForWork() member function.

checkForWork() is the key method in this class. It is called by some work-loop when convienient and is expected to evaluate it's internal state and determine if an event has occurred since the last call. In the case of an event having occurred then the instance defined target(owner)/action will be called. The action is stored as an ordinary C function pointer but the first parameter is always the owner. This means that a C++ member function can be used as an action function though this depends on the ABI.

Although the eventChainNext variable contains a reference to the next event source in the chain this reference is not retained. The list 'owner' i.e. the client that creates the event, not the work-loop, is expected to retain the source.

Functions

checkForWork

Pure Virtual member function used by IOWorkLoop for work scheduling.

disable

Disable event source.

enable

Enable event source.

getAction

Get'ter for $link action variable.

getNext

Get'ter for $link eventChainNext variable.

getWorkLoop

Get'ter for $link workLoop variable.

init

Primary initialiser for the IOEventSource class.

isEnabled

Get'ter for $link enable variable.

onThread

Convenience function for workLoop->onThread.

setAction

Set'ter for $link action variable.

setNext

Set'ter for $link eventChainNext variable.

setWorkLoop

Set'ter for $link workLoop variable.

Pure Virtual member function used by IOWorkLoop for work scheduling.

protected

virtual bool checkForWork() = 0; 

Return Value

Return true if this function needs to be called again before all its outstanding events have been processed.

Discussion

This function will be called to request a subclass to check it's internal state for any work to do and then to call out the owner/action.

Disable event source.

public

virtual void disable(); 

Discussion

A subclass implementation is expected to respect the enabled state when checkForWork is called.

Enable event source.

public

virtual void enable(); 

Discussion

A subclass implementation is expected to respect the enabled state when checkForWork is called. Calling this function will cause the work-loop to be signalled so that a checkForWork is performed.

Get'ter for $link action variable.

public

virtual IOEventSource::Action getAction() const; 

Return Value

value of action.

Get'ter for $link eventChainNext variable.

protected

virtual IOEventSource *getNext() const; 

Return Value

value of eventChainNext.

Get'ter for $link workLoop variable.

public

virtual IOWorkLoop *getWorkLoop() const; 

Return Value

value of workLoop.

Primary initialiser for the IOEventSource class.

protected

virtual bool init(
    OSObject *owner,
    IOEventSource::Action action = 0); 

Parameters

Return Value

true if the inherited classes and this instance initialise successfully.

Get'ter for $link enable variable.

public

virtual bool isEnabled() const; 

Return Value

true if enabled.

Convenience function for workLoop->onThread.

public

virtual bool onThread() const; 

Return Value

true if called on the work-loop thread.

Set'ter for $link action variable.

public

virtual void setAction(
    IOEventSource::Action action); 

Parameters

Set'ter for $link eventChainNext variable.

protected

virtual void setNext(
    IOEventSource *next); 

Parameters

Set'ter for $link workLoop variable.

protected

virtual void setWorkLoop(
    IOWorkLoop *workLoop); 

Parameters

Typedefs

Action

public

typedef void ( *Action)(
    OSObject *owner,
    ...); 

Fields

Discussion

Placeholder type for C++ function overloading discrimination. As the all event sources require an action and it has to be stored somewhere and be of some type, this is that type.

Structs and Unions

ExpansionData

protected

struct ExpansionData {
}; 

Discussion

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

Member Data

action

enabled

eventChainNext

owner

refcon

reserved

workLoop

protected

Action action; 

Discussion

The action method called when an event has been delivered

protected

bool enabled; 

Discussion

Is this event source enabled to deliver requests to the work-loop.

protected

IOEventSource *eventChainNext; 

Discussion

The next event source in the event chain. nil at end of chain.

protected

OSObject *owner; 

Discussion

The owner object called when an event has been delivered.

protected

void *refcon; 

Discussion

What ever the client wants to do, see $link setRefcon.

protected

ExpansionData *reserved; 

Discussion

Reserved for future use. (Internal use only)

protected

IOWorkLoop *workLoop; 

Discussion

What is the work-loop for this event source.

Macro Definitions

IOEventSourceAction

#define IOEventSourceAction IOEventSource::Action 

Discussion

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

Last Updated: 2010-07-29