xnu-792.6.22.tar.gz

[apple/xnu.git] / iokit / IOKit / IOWorkLoop.h

/*
 * Copyright (c) 1998-2000 Apple Computer, Inc. All rights reserved.
 *
 * @APPLE_LICENSE_HEADER_START@
 * 
 * The contents of this file constitute Original Code as defined in and
 * are subject to the Apple Public Source License Version 1.1 (the
 * "License").  You may not use this file except in compliance with the
 * License.  Please obtain a copy of the License at
 * http://www.apple.com/publicsource and read it before using this file.
 * 
 * This Original Code and all software distributed under the License are
 * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT.  Please see the
 * License for the specific language governing rights and limitations
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 * @APPLE_LICENSE_HEADER_END@
 */
/*
Copyright (c) 1998 Apple Computer, Inc.	 All rights reserved.
HISTORY
    1998-7-13	Godfrey van der Linden(gvdl)
	Created.
    1998-10-30	Godfrey van der Linden(gvdl)
	Converted to C++
*/

#ifndef __IOKIT_IOWORKLOOP_H
#define __IOKIT_IOWORKLOOP_H

#include <libkern/c++/OSObject.h>
#include <IOKit/IOReturn.h>
#include <IOKit/IOLib.h>
#include <IOKit/IOLocks.h>

#include <IOKit/system.h>

class IOEventSource;
class IOTimerEventSource;
class IOCommandGate;

/*! @class IOWorkLoop
    @discussion An IOWorkLoop is a thread of control that is intended to be used to provide single threaded access to hardware.  This class has no knowledge of the nature and type of the events that it marshals and forwards.  When a device driver successfully starts (see IOService::start), it is expected to create the event sources it will need to receive events.  Then a work loop is initialized and the events are added to the work loop for monitoring.  In general this set up will be automated by the family superclass of the specific device.
<br><br>
	The thread main method walks the event source linked list and messages each one requesting a work check.  At this point each event source is expected to notify its registered owner that the event has occurred.  After each event has been walked and each indicates that another loop isn't required (by setting the 'more' flag to false) the thread will go to sleep on a signaling semaphore.
<br><br>
	When an event source is registered with a work loop it is informed of the semaphore to use to wake up the loop.
*/
class IOWorkLoop : public OSObject
{
    OSDeclareDefaultStructors(IOWorkLoop)

public:
/*!
    @typedef Action
    @discussion Type and arguments of callout C function that is used when
a runCommand is executed by a client.  Cast to this type when you want a C++
member function to be used.  Note the arg1 - arg3 parameters are straight pass
through from the runCommand to the action callout.
    @param target
	Target of the function, can be used as a refcon.  Note if a C++ function
was specified, this parameter is implicitly the first parameter in the target
member function's parameter list.
    @param arg0 Argument to action from run operation.
    @param arg1 Argument to action from run operation.
    @param arg2 Argument to action from run operation.
    @param arg3 Argument to action from run operation.
*/
    typedef IOReturn (*Action)(OSObject *target,
			       void *arg0, void *arg1,
			       void *arg2, void *arg3);

private:
/*! @function threadMainContinuation
    @abstract Static function that calls the threadMain function. 
*/
    static void threadMainContinuation(IOWorkLoop *self);

protected:

/*! @typedef maintCommandEnum
    @discussion Enumeration of commands that _maintCommand can deal with.  
    @constant mAddEvent Used to tag a Remove event source command.
    @constant mRemoveEvent Used to tag a Remove event source command. 
*/    
    typedef enum { mAddEvent, mRemoveEvent } maintCommandEnum;

/*! @var gateLock
    Mutual exclusion lock that is used by close and open Gate functions.  
*/
    IORecursiveLock *gateLock;

/*! @var eventChain 
    Pointer to first event source in linked list. 
*/
    IOEventSource *eventChain;

/*! @var controlG 
    Internal control gate to maintain event system.  
*/
    IOCommandGate *controlG;

/*! @var workSpinLock
    The spin lock that is used to guard the 'workToDo' variable. 
*/
    IOSimpleLock *workToDoLock;

/*! @var workThread 
    Work loop thread.	
*/
    IOThread workThread;

/*! @var workToDo
    Used to to indicate that an interrupt has fired and needs to be processed.
*/
    volatile bool workToDo;

/*! @var loopRestart
    Set if an event chain has been changed and the system has to be rechecked from start.  (Internal use only)  
*/
    bool loopRestart;

/*! @struct ExpansionData
    @discussion This structure will be used to expand the capablilties of the IOWorkLoop in the future.
*/    
    struct ExpansionData { };

/*! @var reserved
    Reserved for future use.  (Internal use only) 
*/
    ExpansionData *reserved;

/*! @function _maintRequest
    @abstract Synchronous implementation of addEventSource and removeEventSource functions. 
    @discussion This function implements the commands as defined in the maintCommandEnum.  It can be subclassed but it isn't an external API in the usual sense.  A subclass implementation of _maintRequest would be called synchronously with respect to the work loop and it should be implemented in the usual way that an ioctl would be.
    @return kIOReturnUnsupported if the command given is not implemented, kIOReturnSuccess otherwise.
*/
    virtual IOReturn _maintRequest(void *command, void *data, void *, void *);

/*! @function free
    @discussion Mandatory free of the object independent of the current retain count.  If the work loop is running, this method will not return until the thread has successfully terminated.  Each event source in the chain will be released and the working semaphore will be destroyed.
<br><br>
	If the client has some outstanding requests on an event they will never be informed of completion.  If an external thread is blocked on any of the event sources they will be awakened with a KERN_INTERUPTED status. 
*/
    virtual void free();

/*! @function threadMain
    @discussion Work loop threads main function.  This function consists of 3 loops: the outermost loop is the semaphore clear and wait loop, the middle loop terminates when there is no more work, and the inside loop walks the event list calling the checkForWork method in each event source.  If an event source has more work to do, it can set the more flag and the middle loop will repeat.  When no more work is outstanding the outermost will sleep until an event is signalled or the least wakeupTime, whichever occurs first.  If the event source does not require the semaphore wait to time out, it must set the provided wakeupTime parameter to zero.
*/
    virtual void threadMain();

public:

/*! @function workLoop
    @abstract Factory member function to constuct and intialize a work loop.
    @result Returns a workLoop instance if constructed successfully, 0 otherwise. 
*/
    static IOWorkLoop *workLoop();

/*! @function init
    @discussion Initializes an instance of the workloop.  This method creates and initialses the signaling semaphore and forks the thread that will continue executing.
    @result Returns true if initialized successfully, false otherwise. 
*/
    virtual bool init();

/*! @function getThread
    @abstract Gets the workThread.
    @result Returns workThread.
*/
    virtual IOThread getThread() const;

/*! @function onThread
    @abstract Is the current execution context on the work thread? 
    @result Returns true if IOThreadSelf() == workThread. 
*/
    virtual bool onThread() const;

/*! @function inGate
    @abstract Is the current execution context holding the work-loop's gate? 
    @result Returns true if IOThreadSelf() is gate holder.
*/
    virtual bool inGate() const;
    
/*! @function addEventSource
    @discussion Add an event source to be monitored by the work loop.  This function does not return until the work loop has acknowledged the arrival of the new event source.  When a new event has been added the threadMain will always restart its loop and check all outstanding events.  The event source is retained by the work loop.
    @param newEvent Pointer to IOEventSource subclass to add.
    @result Always returns kIOReturnSuccess. 
*/
    virtual IOReturn addEventSource(IOEventSource *newEvent);

/*! @function removeEventSource
    @discussion Remove an event source from the work loop.  This function does not return until the work loop has acknowledged the removal of the event source.  When an event has been removed the threadMain will always restart its loop and check all outstanding events.  The event source will be released before return.
    @param toRemove Pointer to IOEventSource subclass to remove.
    @result Returns kIOReturnSuccess if successful, kIOReturnBadArgument if toRemove couldn't be found. 
*/
    virtual IOReturn removeEventSource(IOEventSource *toRemove);

/*! @function enableAllEventSources
    @abstract Calls enable() in all event sources.
    @discussion For all event sources in eventChain, call enable() function.  See IOEventSource::enable().
*/
    virtual void enableAllEventSources() const;

/*! @function disableAllEventSources
    @abstract Calls disable() in all event sources.
    @discussion For all event sources in eventChain, call disable() function.  See IOEventSource::disable().
*/
    virtual void disableAllEventSources() const;

/*! @function enableAllInterrupts
    @abstract Calls enable() in all interrupt event sources.
    @discussion For all event sources (ES) for which IODynamicCast(IOInterruptEventSource, ES) is valid, in eventChain call enable() function.  See IOEventSource::enable().
*/
    virtual void enableAllInterrupts() const;

/*! @function disableAllInterrupts
    @abstract Calls disable() in all interrupt event sources.
    @discussion For all event sources (ES) for which IODynamicCast(IOInterruptEventSource, ES) is valid,  in eventChain call disable() function.  See IOEventSource::disable().
*/
    virtual void disableAllInterrupts() const;


protected:
    // Internal APIs used by event sources to control the thread
    friend class IOEventSource;
    friend class IOTimerEventSource;
    virtual void signalWorkAvailable();
    virtual void openGate();
    virtual void closeGate();
    virtual bool tryCloseGate();
    virtual int sleepGate(void *event, UInt32 interuptibleType);
    virtual void wakeupGate(void *event, bool oneThread);

public:
    /* methods available in Mac OS X 10.1 or later */

/*! @function runAction
    @abstract Single thread a call to an action with the work-loop.
    @discussion Client function that causes the given action to be called in
a single threaded manner.  Beware: the work-loop's gate is recursive and runAction can cause direct or indirect re-entrancy.  When executing on a client's thread, runAction will sleep until the work-loop's gate opens for
execution of client actions, the action is single threaded against all other work-loop event sources.
    @param action Pointer to function to be executed in work-loop context.
    @param arg0 Parameter for action parameter, defaults to 0.
    @param arg1 Parameter for action parameter, defaults to 0.
    @param arg2 Parameter for action parameter, defaults to 0.
    @param arg3 Parameter for action parameter, defaults to 0.
    @result Returns the value of the Action callout.
*/
    virtual IOReturn runAction(Action action, OSObject *target,
			       void *arg0 = 0, void *arg1 = 0,
			       void *arg2 = 0, void *arg3 = 0);

protected:
    OSMetaClassDeclareReservedUsed(IOWorkLoop, 0);

    OSMetaClassDeclareReservedUnused(IOWorkLoop, 1);
    OSMetaClassDeclareReservedUnused(IOWorkLoop, 2);
    OSMetaClassDeclareReservedUnused(IOWorkLoop, 3);
    OSMetaClassDeclareReservedUnused(IOWorkLoop, 4);
    OSMetaClassDeclareReservedUnused(IOWorkLoop, 5);
    OSMetaClassDeclareReservedUnused(IOWorkLoop, 6);
    OSMetaClassDeclareReservedUnused(IOWorkLoop, 7);
};

#endif /* !__IOKIT_IOWORKLOOP_H */