/*
 * $Header: /home/wistrand/cvs/knopflerfish.org/osgi/bundles/device/device/src/org/osgi/service/device/Driver.java,v 1.1.1.1 2004/03/05 20:35:06 wistrand Exp $
 *
 * Copyright (c) The Open Services Gateway Initiative (2000, 2002).
 * All Rights Reserved.
 *
 * Implementation of certain elements of the Open Services Gateway Initiative
 * (OSGI) Specification may be subject to third party intellectual property
 * rights, including without limitation, patent rights (such a third party may
 * or may not be a member of OSGi). OSGi is not responsible and shall not be
 * held responsible in any manner for identifying or failing to identify any or
 * all such third party intellectual property rights.
 *
 * This document and the information contained herein are provided on an "AS
 * IS" basis and OSGI DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
 * BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL
 * NOT INFRINGE ANY RIGHTS AND ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR
 * FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT WILL OSGI BE LIABLE FOR ANY
 * LOSS OF PROFITS, LOSS OF BUSINESS, LOSS OF USE OF DATA, INTERRUPTION OF
 * BUSINESS, OR FOR DIRECT, INDIRECT, SPECIAL OR EXEMPLARY, INCIDENTIAL,
 * PUNITIVE OR CONSEQUENTIAL DAMAGES OF ANY KIND IN CONNECTION WITH THIS
 * DOCUMENT OR THE INFORMATION CONTAINED HEREIN, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH LOSS OR DAMAGE.
 *
 * All Company, brand and product names may be trademarks that are the sole
 * property of their respective owners. All rights reserved.
 */

package org.osgi.service.device;

import org.osgi.framework.ServiceReference;

/**
 * A <tt>Driver</tt> service object must be registered by each Driver bundle
 * wishing to attach to Device services provided by other drivers.
 * For each newly discovered {@link Device} object, the device manager
 * enters a bidding phase. The <tt>Driver</tt> object whose
 * {@link #match} method bids the highest for a particular
 * <tt>Device</tt> object will be instructed by the device manager to attach to
 * the <tt>Device</tt> object.
 *
 * @version $Revision: 1.1.1.1 $
 * @author Open Services Gateway Initiative
 * @see Device
 * @see DriverLocator
 */

public abstract interface Driver
{
   /**
	 * Checks whether this Driver service can be attached to the Device service.
	 *
     * The Device service is represented by the given {@link ServiceReference} and returns a value
     * indicating how well this driver can support the given Device service,
     * or {@link Device#MATCH_NONE} if it cannot support the given
     * Device service at all.
     *
     * <p>The return value must be one of the possible match values defined
     * in the device category definition for the given Device service, or
     * <tt>Device.MATCH_NONE</tt> if the category of the Device service is not
     * recognized.
     *
     * <p>In order to make its decision, this Driver service may examine
     * the properties associated with the given Device service, or may get
     * the referenced service object (representing the actual
     * physical device) to talk to it, as long as it ungets the
     * service and returns the physical device to a normal state
     * before this method returns.
     *
     * <p>A Driver service must always return the same match code whenever it
     * is presented with the same Device service.
     *
     * <p>The match function is called by the device manager during
     * the matching process.
     *
     * @param reference the <tt>ServiceReference</tt> object of the device to match
     *
     * @return value indicating how well this driver can support the
     * given Device service, or <tt>Device.MATCH_NONE</tt> if it cannot support the
     * Device service at all
     *
     * @exception java.lang.Exception if this Driver service cannot
     * examine the Device service
     */
    public abstract int match(ServiceReference reference)
    throws Exception;

    /**
     * Attaches this Driver service to the Device service represented by the given
     * <tt>ServiceReference</tt> object.
     *
     * <p>A return value of <tt>null</tt> indicates that this Driver service has
     * successfully attached to the given Device service. If this Driver service is
     * unable to attach to the given Device service, but knows of a more
     * suitable Driver service, it must return the <tt>DRIVER_ID</tt> of that Driver service. This
     * allows for the implementation of referring drivers whose only
     * purpose is to refer to other drivers capable of handling a
     * given Device service.
     *
     * <p>After having attached to the Device service, this driver may
     * register the underlying device as a new service exposing driver-specific
     * functionality.
     *
     * <p>This method is called by the device manager.
     *
     * @param reference the <tt>ServiceReference</tt> object of the device to attach to
     *
     * @return <tt>null</tt> if this Driver service has successfully attached to
     * the given Device service, or the <tt>DRIVER_ID</tt> of a more suitable driver
     *
     * @exception java.lang.Exception if the driver cannot attach to the
     * given device and does not know of a more suitable driver
     */
    public abstract String attach(ServiceReference reference)
    throws Exception;
}