/*
 * Copyright (c) 2000 Apple Computer, Inc. All rights reserved.
 *
 * @APPLE_LICENSE_OSREFERENCE_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_LICENSE_OSREFERENCE_HEADER_END@
 */

/*
 *
 *	Copyright (c) 2000 Apple Computer, Inc.  All rights reserved.
 *
 *	HISTORY
 *
 *	2001-01-18 gvdl	Made the primary queue pointer public, to be used when
 *			Ownership is clear.
 *	11/13/2000 CJS	Created IOCommand class and implementation
 *
 */

/*!
 * @header IOCommand
 * @abstract
 * This header contains the IOCommand class definition.
 */

#ifndef _IOKIT_IO_COMMAND_H_
#define _IOKIT_IO_COMMAND_H_

/*
 * Kernel
 */

#if defined(KERNEL) && defined(__cplusplus)

#include <kern/queue.h>
#include <libkern/c++/OSObject.h>

/*!
 * @class IOCommand
 * @abstract
 * This class is an abstract class which represents an I/O command.
 * @discussion
 * This class is an abstract class which represents an I/O command passed
 * from a device driver to a controller. All controller commands (e.g. IOATACommand)
 * should inherit from this class.
 */
 
class IOCommand : public OSObject
{
    OSDeclareDefaultStructors(IOCommand)
    
public:
    virtual bool init(void);
    
/*! @var fCommandChain
    This variable is used by the current 'owner' to queue the command.  During the life cycle of a command it moves through a series of queues.  This is the queue pointer for it.  Only valid while 'ownership' is clear.  For instance a IOCommandPool uses this pointer to maintain its list of free commands.  May be manipulated using the kern/queue.h macros */
    queue_chain_t fCommandChain;	/* used to queue commands */
};

#endif /* defined(KERNEL) && defined(__cplusplus) */

#endif	/* _IOKIT_IO_COMMAND_H_ */
