com.ibm.jusb.os

Class AbstractUsbServices

java.lang.Object

com.ibm.jusb.os.AbstractUsbServices

All Implemented Interfaces:

UsbServices

Direct Known Subclasses:

LinuxUsbServices, WindowsUsbServices

public abstract class AbstractUsbServices
extends Object
implements UsbServices

Abstract implementation of UsbServices.

Author:

Dan Streetman

Field Summary

Fields

Modifier and Type	Field and Description
protected UsbServicesListenerImp	listenerImp

Constructor Summary

Constructors

Constructor and Description
AbstractUsbServices()

Method Summary

Methods

Modifier and Type	Method and Description
void	addUsbServicesListener(UsbServicesListener listener) Add UsbServicesListener.
UsbHub	getRootUsbHub() Get the virtual UsbHub to which all physical Host Controller UsbHubs are attached.
UsbHubImp	getRootUsbHubImp()
void	removeUsbServicesListener(UsbServicesListener listener) Remove UsbServicesListener.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface javax.usb.UsbServices

getApiVersion, getImpDescription, getImpVersion

Field Detail

listenerImp

protected UsbServicesListenerImp listenerImp

Constructor Detail

AbstractUsbServices

public AbstractUsbServices()

Method Detail

getRootUsbHub

public UsbHub getRootUsbHub()
                     throws UsbException

Description copied from interface: UsbServices

Get the virtual UsbHub to which all physical Host Controller UsbHubs are attached.

The USB root hub is a special hub at the top of the topology tree. The USB 1.1 specification mentions root hubs in sec 5.2.3, where it states that 'the host includes an embedded hub called the root hub'. The implication of this seems to be that the (hardware) Host Controller device is the root hub, since the Host Controller device 'emulates' a USB hub, and in systems with only one physical Host Controller device, its emulated hub is in effect the root hub. However when multiple Host Controller devices are considered, there are two (2) options that were considered:

1. Have an array or list of the available topology trees, with each physical Host Controller's emulated root hub as the root UsbHub of that particular topology tree. This configuration could be compared to the MS-DOS/Windows decision to assign drive letters to different physical drives (partitions).
2. Have a 'virtual' root hub, which is completely virtual (not associated with any physical device) and is created and managed solely by the javax.usb implementation. This configuration could be compared to the UNIX descision to put all physical drives on 'mount points' under a single 'root' (/) directory filesystem.

The first configuration results in having to maintain a list of different and completely unconnected device topologies. This means a search for a particular device must be performed on all the device topologies. Since a UsbHub already has a list of UsbDevices, and a UsbHub is a UsbDevice, introducing a new, different list is not a desirable action, since it introduces extra unnecessary steps in performing actions, like searching.

As an example, a recursive search for a certain device in the first configuration involves getting the first root UsbHub, getting all its attached UsbDevices, and checking each device; any of those devices which are UsbHubs can be also searched recursively. Then, the entire operation must be performed on the next root UsbHub, and this is repeated for all the root UsbHubs in the array/list. In the second configuration, the virtual root UsbHub is recursively searched in a single operation.

The second configuration is what is used in this API. The implementation is responsible for creating a single root UsbHub which is completely virtual (and available through the UsbServices object). Every UsbHub attached to this virtual root UsbHub corresponds to a physical Host Controller's emulated hub. I.e., the first level of UsbDevices under the virtual root UsbHub are all UsbHubs corresponding to a particular Host Controller on the system. Note that since the root UsbHub is a virtual hub, the number of ports is not posible to specify; so all that is guaranteed is the number of ports is at least equal to the number of UsbHubs attached to the root UsbHub. The number of ports on the virtual root UsbHub may change if UsbHubs are attached or detached (e.g., if a Host Controller is physically hot-removed from the system or hot-plugged, or if its driver is dynamically loaded, or for any other reason a top-level Host Controller's hub is attached/detached). This API specification suggests that the number of ports for the root UsbHub equal the number of directly attached UsbHubs.

Specified by:

getRootUsbHub in interface UsbServices

Returns:

The root UsbHub.

Throws:

UsbException - If there is an error accessing javax.usb.

getRootUsbHubImp

public UsbHubImp getRootUsbHubImp()

Returns:

The root UsbHubImp.

addUsbServicesListener

public void addUsbServicesListener(UsbServicesListener listener)

Description copied from interface: UsbServices

Add UsbServicesListener.

Specified by:

addUsbServicesListener in interface UsbServices

Parameters:

listener - The listener to add.

removeUsbServicesListener

public void removeUsbServicesListener(UsbServicesListener listener)

Description copied from interface: UsbServices

Remove UsbServicesListener.

Specified by:

removeUsbServicesListener in interface UsbServices

Parameters:

listener - The listener to remove.