This is xnu-8019. See this file in:
/*
 * Copyright (c) 1998-2019 Apple Inc. All rights reserved.
 *
 * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
 *
 * This file contains Original Code and/or Modifications of Original Code
 * as defined in and that are subject to the Apple Public Source License
 * Version 2.0 (the 'License'). You may not use this file except in
 * compliance with the License. The rights granted to you under the License
 * may not be used to create, or enable the creation or redistribution of,
 * unlawful or unlicensed copies of an Apple operating system, or to
 * circumvent, violate, or enable the circumvention or violation of, any
 * terms of an Apple operating system software license agreement.
 *
 * Please obtain a copy of the License at
 * http://www.opensource.apple.com/apsl/ and read it before using this file.
 *
 * The 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, QUIET ENJOYMENT OR NON-INFRINGEMENT.
 * Please see the License for the specific language governing rights and
 * limitations under the License.
 *
 * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
 */

#ifndef _IOKIT_IOSERVICESTATENOTIFICATIONEVENTSOURCE_H
#define _IOKIT_IOSERVICESTATENOTIFICATIONEVENTSOURCE_H

#include <libkern/c++/OSPtr.h>
#include <IOKit/IOEventSource.h>

class IOService;


/*! @class IOServiceStateNotificationEventSource : public IOEventSource
 *   @abstract Event source for IOService state notification delivery to work-loop based drivers.
 *   @discussion For use with the IOService.iig IOService::StateNotification* APIs.
 */

class IOServiceStateNotificationEventSource : public IOEventSource
{
	OSDeclareDefaultStructors(IOServiceStateNotificationEventSource);

public:
	typedef void (^ActionBlock)();

protected:
	IOService                    * fStateNotification;
	IOStateNotificationListenerRef fListener;
	bool                           fEnable;
	bool                           fArmed;

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

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

/*! @function free
 *   @abstract Sub-class implementation of free method, disconnects from the interrupt source. */
	virtual void free() APPLE_KEXT_OVERRIDE;

/*! @function checkForWork
 *   @abstract Pure Virtual member function used by IOWorkLoop for issueing a client calls.
 *   @discussion This function called when the work-loop is ready to check for any work to do and then to call out the owner/action.
 *   @result Return true if this function needs to be called again before all its outstanding events have been processed. */
	virtual bool checkForWork() APPLE_KEXT_OVERRIDE;

/*! @function setWorkLoop
 *   @abstract Sub-class implementation of setWorkLoop method. */
	virtual void setWorkLoop(IOWorkLoop *inWorkLoop) APPLE_KEXT_OVERRIDE;

public:

	/*!
	 * @brief       Create an IOServiceStateNotificationEventSource for notification of IOService state events sent by the StateNotificationSet() api.
	 * @param       service The object hosting state, typically returned by IOService::CopySystemStateNotificationService().
	 * @param       items Array of state item names to be notified about.
	 * @param       action Handler block to be invoked on the event source workloop when the notification fires.
	 * @return      IOServiceStateNotificationEventSource with +1 retain, or NULL on failure.
	 */
	static OSPtr<IOServiceStateNotificationEventSource>
	serviceStateNotificationEventSource(IOService *service,
	    OSArray * items,
	    ActionBlock action);

/*! @function enable
 *   @abstract Enable event source.
 *   @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. */
	virtual void enable() APPLE_KEXT_OVERRIDE;

/*! @function disable
 *   @abstract Disable event source.
 *   @discussion A subclass implementation is expected to respect the enabled
 *  state when checkForWork is called. */
	virtual void disable() APPLE_KEXT_OVERRIDE;

private:
	OSMetaClassDeclareReservedUnused(IOServiceStateNotificationEventSource, 0);
	OSMetaClassDeclareReservedUnused(IOServiceStateNotificationEventSource, 1);
	OSMetaClassDeclareReservedUnused(IOServiceStateNotificationEventSource, 2);
	OSMetaClassDeclareReservedUnused(IOServiceStateNotificationEventSource, 3);
	OSMetaClassDeclareReservedUnused(IOServiceStateNotificationEventSource, 4);
	OSMetaClassDeclareReservedUnused(IOServiceStateNotificationEventSource, 5);
	OSMetaClassDeclareReservedUnused(IOServiceStateNotificationEventSource, 6);
	OSMetaClassDeclareReservedUnused(IOServiceStateNotificationEventSource, 7);
};

#endif /* !_IOKIT_IOSERVICESTATENOTIFICATIONEVENTSOURCE_H */