javax.usb

Interface UsbServices

All Known Implementing Classes:

AbstractUsbServices, LinuxUsbServices, WindowsUsbServices

public interface UsbServices

Interface for a javax.usb implementation.

This is instantiated by the UsbHostManager. The implementation must include a no-parameter constructor.

Author:

Dan Streetman, E. Michael Maximilien

Method Summary

Methods

Modifier and Type	Method and Description
void	addUsbServicesListener(UsbServicesListener listener) Add UsbServicesListener.
String	getApiVersion() Get the (minimum) version number of the javax.usb API that this UsbServices implements.
String	getImpDescription() Get a description of this UsbServices implementation.
String	getImpVersion() Get the version number of the UsbServices implementation.
UsbHub	getRootUsbHub() Get the virtual UsbHub to which all physical Host Controller UsbHubs are attached.
void	removeUsbServicesListener(UsbServicesListener listener) Remove UsbServicesListener.

Method Detail

getRootUsbHub

UsbHub getRootUsbHub()
                     throws UsbException,
                            SecurityException

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.

Returns:

The virtual UsbHub object.

Throws:

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

SecurityException - If current client not configured to access javax.usb.

addUsbServicesListener

void addUsbServicesListener(UsbServicesListener listener)

Add UsbServicesListener.

Parameters:

listener - The UsbServicesListener.

removeUsbServicesListener

void removeUsbServicesListener(UsbServicesListener listener)

Remove UsbServicesListener.

Parameters:

listener - The UsbServicesListener.

getApiVersion

String getApiVersion()

Get the (minimum) version number of the javax.usb API that this UsbServices implements.

This should correspond to the output of (some version of) the javax.usb.Version.

Returns:

the version number of the minimum API version.

getImpVersion

String getImpVersion()

Get the version number of the UsbServices implementation.

The format should be ..

Returns:

the version number of the UsbServices implementation.

getImpDescription

String getImpDescription()

Get a description of this UsbServices implementation.

The format is implementation-specific, but should include at least the following:

• The company or individual author(s).
• The license, or license header.
• Contact information.
• The minimum or expected version of Java.
• The Operating System(s) supported (usually one per implementation).
• Any other useful information.

Returns:

a description of the implementation.