System Administration Guide: Devices and File Systems

Chapter 7 Using USB Devices (Overview)

This chapter provides an overview of Universal Serial Bus (USB) devices in the Solaris OS.

This is a list of the overview information in this chapter.

For recent information about USB devices, go to the following site:

For general information about USB devices, go to the following site:

For step-by-step instructions on using USB devices in the Solaris OS, see Chapter 8, Using USB Devices (Tasks).

For general information about dynamic reconfiguration and hot-plugging, see Chapter 6, Dynamically Configuring Devices (Tasks).

For information on configuring USB printers, see System Administration Guide: Solaris Printing.

What's New in USB Devices?

The following section describes new USB features in the Solaris release.

USB Interface Association Descriptor Support

Solaris Express Developer Edition 5/07: A USB device node type, IA node, is created for Interface Association Descriptor (IAD) support. This feature means that a driver might support multiple interfaces for the same device, such as the video and audio interfaces of a webcam. If no driver is found for an IA node, a nexus driver, usb_ia, is bound to the IA node to create the interface nodes. For more information, see usb_ia(7D).

EHCI Isochronous Transfer Support

Solaris Express Developer Edition 5/07: USB EHCI host controller driver provides isochronous transfer support for USB 2.0 or high-speed isochronous devices. For more information, see usb_isoc_request(9S).

Support for CDC ACM Devices

Solaris Express Developer Edition 5/07: Support for CDC ACM devices is provided in this release. For more information, see USB Driver Enhancements.

Changed USB Device Hotpluggable Behavior

Solaris Express 6/06: This feature information has been revised in the Solaris Express 10/06 release.

This Solaris release introduces a new device attribute, hotpluggable, to identify those devices that can be connected or disconnected without rebooting the system and configured or unconfigured automatically without user intervention. All USB and 1394 devices are identified as hotpluggable devices to gain those benefits described in Using USB Mass Storage Devices. In addition, non-removable media USB and 1394 devices are no longer identified as removable-media devices and no longer have a removable-media attribute.

The changes are primarily made at the kernel level to improve support for non-removable media USB and 1394 devices, and improve the performance for those devices. However, theses changes do not impact the use of these devices. For example, the responsibility of mounting and unmounting these devices is controlled by rmvolmgr. From a user's perspective, the only visible changes are the hotpluggable and removable-media attributes of a device.

For more information, see USB and 1394 (FireWire) Support Enhancements.

ZFS Support on USB Devices

Solaris Express 6/06: This information has been revised in the Solaris Express 10/06 release.

You can create and mount ZFS file systems on USB mass storage devices. For information about using USB mass storage devices, see Using USB Mass Storage Devices.

For information about creating and mounting ZFS file systems, see zfs(1M) and zpool(1M).

Support for Prolific and Keyspan Serial Adapters

Solaris Express 1/06: Support for Prolific and Keyspan serial adapters is provided in this release. For more information, see USB Driver Enhancements.

USB Power Budgeting

Solaris Express 1/06: This Solaris release includes power budgeting of USB devices to better manage the power that is distributed to USB devices. Power budget control helps prevent over-current conditions from occurring and generally makes using USB devices safer. For more information about Solaris USB power budgeting limitations, see Bus-Powered Devices.

x86: Support for USB CDs and DVDs in GRUB-Based Booting

Solaris Express 6/05: You can use the following USB features in the GRUB-based booting environment:

For more information about GRUB-based booting, see Chapter 9, Shutting Down and Booting a System (Overview), in System Administration Guide: Basic Administration.

USB Virtual Keyboard and Mouse Support

Solaris Express 6/05: USB virtual keyboard and mouse support enables you to hook up multiple keyboards and multiple mice, where the set of keyboards or mice behave as one virtual keyboard or mouse. This means that the input of each physical device is coalesced into a single input stream. For example, if you type SHIFT on one keyboard and A on another, the character echoed is an uppercase A.

Also supported is the ability to add a USB keyboard or mouse to a laptop and have these devices work as one device with the laptop's PS/2 keyboard and pad.

In addition, support for barcode readers is provided by the virtual keyboard and mouse feature.

For more information, refer to virtualkm(7D).

vold Provides Awareness of Hot-Plugged USB Devices

Solaris Express 12/06: The vold features are removed in this release. For information about managing removable media with vold in the Solaris 10 releases, see System Administration Guide: Devices and File Systems.

For information about new removable media management services in the Solaris Express release, see Changes and Improvements to Removable Media Management.

Solaris Express 6/05: The removable media manager (vold) is now hotplug aware. There is no need to restart this daemon to mount a USB mass storage device that has been hot-inserted. However, for some devices, it might still be necessary to manually mount the devices as vold is not always successful. In the case where vold fails to automatically mount a USB device, stop vold, like this:

# /etc/init.d/volmgt stop

For information about manually mounting a USB mass storage device, see How to Mount or Unmount a USB Mass Storage Device.

Solaris Support for USB Devices

Use the following table to identify Solaris support information for specific USB 1.1 and USB 2.0 devices.


Solaris 8 HW 5/03 and Later Releases 

Solaris 9 Releases 

Solaris 10 Releases 

Solaris Express Releases 

General USB 1.1 device support

SPARC and x86 

SPARC and x86 

SPARC and x86 

SPARC and x86 

General USB 2.0 device support

SPARC only 

SPARC and x86 (Solaris 9 4/04) 

SPARC and x86 

SPARC and x86 

Specific USB 1.1 and USB 2.0 device support


audio devices (See notes below.) 

USB 1.1 only:

Not supported on a USB 2.0 hub 

USB 1.1 only:

Not supported on a USB 2.0 hub 

USB 1.1 only:

Supported on a USB 2.0 hub 

USB 1.1 only:

Supported on a USB 2.0 hub 

generic USB driver (ugen(7D))

SPARC only 

SPARC and x86 

SPARC and x86 

SPARC and x86 

hid devices (keyboard and mouse devices, hid(7D))

SPARC and x86 

SPARC and x86 

SPARC and x86 

SPARC and x86 

hubs (hubd(7D))

SPARC and x86 

SPARC and x86 

SPARC and x86 

SPARC and x86 


SPARC and x86 

SPARC and x86 

SPARC and x86 

SPARC and x86 

serial devices (Edgeport (usbser_edge(7D)), Prolific (usbsprl(7D)), Keyspan (usbsksp(7D))

SPARC and x86 

SPARC and x86 

SPARC and x86 

SPARC and x86 

storage devices (scsa2usb(7D))

SPARC and x86 

SPARC and x86 

SPARC and x86 

SPARC and x86 

user-space USB device management library (libusb(3LIB))

Not supported  

Not supported  

SPARC and x86 

SPARC and x86 


For task information associated with mass storage devices, see Chapter 8, Using USB Devices (Tasks).

For more information about ugen, see USB Driver Enhancements.

Overview of USB Devices

Universal Serial Bus (USB) was developed by the PC industry to provide a low-cost solution for attaching peripheral devices, such as keyboards, mouse devices, and printers, to a system.

USB connectors are designed to fit only one type of cable, in one way. The primary design motivation for USB was to alleviate the need for multiple connector types for different devices. This design reduces the clutter on the back panel of a system.

Devices connect to USB ports on external USB hubs, or on a root hub that is located on the computer itself. Since hubs have several ports, several branches of a device tree can stem from a hub.

For more information, see usba(7D) or go to the following site:

Commonly Used USB Acronyms

The following table describes the USB acronyms that are used in the Solaris OS. For a complete description of USB components and acronyms, go to:



For More Information 


USB generic driver 



Universal Serial Bus 



Universal Serial Bus Architecture (Solaris) 



USBA Client Driver Interface (Solaris) 



USB host controller driver 



Enhanced Host Controller Interface 



Open Host Controller Interface 



Universal Host Controller Interface 


USB Bus Description

The USB specification is openly available and free of royalties. The specification defines the electrical and mechanical interfaces of the bus and the connectors.

USB employs a topology in which hubs provide attachment points for USB devices. The host controller contains the root hub, which is the origin of all USB ports in the system. For more information about hubs, see USB Host Controller and Hubs.

Figure 7–1 USB Physical Device Hierarchy

Diagram shows a system with three active USB ports that
includes a compound device (hub and printer) and composite device (keyboard
and mouse).

Figure 7–1 shows a system with three active USB ports. The first USB port connects a USB memory stick. The second USB port connects an external hub, which in turn, connects a cdrw device and a composite keyboard/mouse device. As a composite device, this keyboard contains a USB controller, which operates both the keyboard and an attached mouse. The keyboard and the mouse share a common USB bus address because they are directed by the same USB controller.

Figure 7–1 also shows an example of a hub and a printer as a compound device. The hub is an external hub that is enclosed in the same casing as the printer. The printer is permanently connected to the hub. The hub and printer have separate USB bus addresses.

The device tree path name for some of the devices that are displayed in Figure 7–1 are listed here.

Memory stick






cdrw device




USB Devices and Drivers

USB devices with similar attributes and services are grouped into device classes. Each device class has a corresponding driver. Devices within a class are managed by the same device driver pair. However, the USB specification also allows for vendor-specific devices that are not part of a specific class.

The Human Interface Device (HID) class contains devices that are user-controlled such as the following devices:

The Communication Device class includes the following devices:

Other device classes include the following classes:

Each USB device contains descriptors that reflect the class of the device. A device class specifies how its members should behave in configuration and data transfer. You can obtain additional class information from:

For more information about USB devices supported in the Solaris release, see usb(7D).

USB Driver Enhancements

The following USB driver enhancements are included.

The EHCI, OHCI, and UHCI Drivers

Features of the EHCI driver include:

Use the prtconf command output to identify whether your system supports USB 1.1 or USB 2.0 devices. For example:

# prtconf  -D | egrep "ehci|ohci|uhci"

If your prtconf output identifies an EHCI controller, your system supports USB 2.0 devices.

If your prtconf output identifies an OHCI or UHCI controller, your system supports USB 1.1 devices.

Solaris USB Architecture (USBA)

USB devices can be represented as two levels of device tree nodes. A device node represents the entire USB device. One or more child interface nodes represent the individual USB interfaces on the device.

Driver binding is achieved by using the compatible name properties. For more information, refer to of the IEEE 1275 USB binding and Writing Device Drivers. A driver can either bind to the entire device and control all the interfaces, or can bind to just one interface. If no vendor or class driver claims the entire device, a generic USB multi-interface driver is bound to the device-level node. This driver attempts to bind drivers to each interface by using compatible names properties, as defined in section of the IEEE 1275 binding specification.

The Solaris USB Architecture (USBA) adheres to the USB 1.1 and USB 2.0 specifications and is part of the Solaris Device Driver Interface (DDI). The USBA model is similar to Sun Common SCSI Architecture (SCSA). As the following figure shows, the USBA is a thin layer that provides a generic USB transport-layer abstraction to client drivers, providing them with services that implement core generic USB functionality.

Figure 7–2 Solaris USB Architecture (USBA)

Diagram shows the relationship between client drivers,
USBA framework, host controller drivers, and the device bus.

About USB in the Solaris OS

This section describes information you should know about USB in the Solaris OS.

USB 2.0 Features

The following USB 2.0 features are included:

For a description of USB devices and terminology, see Overview of USB Devices.

USB 2.0 Device Features and Compatibility Issues

USB 2.0 devices are defined as high-speed devices that follow the USB 2.0 specification. You can refer to the USB 2.0 specification at

To identify the speed of your USB device in the Solaris 10 releases, check the /var/adm/messages file for messages similar to the following:

Dec 13 17:05:57 mysystem usba: [ID 912658] USB 2.0 device
(usb50d,249) operating at hi speed (USB 2.x) on USB 2.0 external hub:
storage@4, scsa2usb0 at bus address 4

Here are some of the USB devices that are supported in this Solaris release:

For a full listing of USB devices that have been verified on the Solaris release, go to:

Additional storage devices might work by modifying the scsa2usb.conf file. For more information, see scsa2usb(7D).

Solaris USB 2.0 device support includes the following features:

For more information on USB 2.0 device support, see ehci(7D) and usba(7D).

Bus-Powered Devices

Bus-powered hubs use power from the USB bus to which they are connected, to power devices connected to them. Special care must be taken to not overload these hubs, because the power these hubs offer to their downstream devices is limited.

Starting in the Solaris Express release, power budgeting is implemented for USB devices. This feature has the following limitations:

USB Keyboards and Mouse Devices

Keep the following issues in mind when using USB keyboards and mouse devices:

USB Wheel Mouse Support

Starting in the Solaris 9 9/04 release, the following wheel mouse features are supported:

USB Host Controller and Hubs

A USB hub is responsible for the following:

The USB host controller has an embedded hub called the root hub. The ports that are visible at the system's back panel are the ports of the root hub. The USB host controller is responsible for the following:

USB Hub Devices

SPARC: USB Power Management

Suspending and resuming USB devices is fully supported on SPARC systems. However, do not suspend a device that is busy and never remove a device when the system is powered off under a suspend shutdown.

The USB framework makes a best effort to power manage all devices on SPARC based systems with power management enabled. Power managing a USB device means that the hub driver suspends the port to which the device is connected. Devices that support remote wake up can notify the system to wake up everything in the device's path so that the device can be used. The host system could also wake up the device if an application sends an I/O to the device.

All HID devices (keyboard, mouse, hub, and storage devices), hub devices, and storage devices are power managed by default if they support remote wake-up capability. A USB printer is power managed only between two print jobs. Devices that are managed by the generic USB driver (UGEN) are power managed only when they are closed.

When power management is running to reduce power consumption, USB leaf devices are powered down first. After all devices that are connected to a hub's ports are powered down, the hub is powered down after some delay. To achieve the most efficient power management, do not cascade many hubs.

For information about using the SUSPEND/SHUTDOWN key on SPARC systems, see USB Keyboards and Mouse Devices.

Guidelines for USB Cables

Keep the following guidelines in mind when connecting USB cables:

For more information, go to: