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System Administration Guide: Devices and File Systems
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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:

  • Better performance – Increased data throughput for devices connected to USB 2.0 controllers, up to 40 times faster than USB 1.1 devices.

    You can take advantage of the high-speed USB protocol when accessing high-speed USB devices, such as DVDs and hard disks.

  • Backward Compatibility – Compatibility with 1.0 and 1.1 devices and drivers so that you can use the same cables, connectors, and software interfaces.

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:

  • Mass storage devices, such as CD-RWs, hard disks, DVDs, digital cameras, diskettes, tape drives, memory sticks, and multi-format card readers

  • Keyboards and mouse devices

  • Audio devices, such as speakers and microphones

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:

  • Increased USB bus speed from 12 Mbyte/sec to 480 Mbyte/sec. This increase means devices that support the USB 2.0 specification can run significantly faster than their USB 1.1 counterparts, when they are connected to a USB 2.0 port.

    A USB 2.0 port might be one of the following possibilities:

    • A port on a USB 2.0 PCI card

    • A port on a USB 2.0 hub that is connected to USB 2.0 port

    • A port on a SPARC or x86 computer motherboard

    A USB 2.0 PCI card might be needed for older SPARC platforms.

  • For a list of USB 2.0 PCI cards that have been verified for the Solaris release, go to:

  • USB 1.1 devices work as they have in the past, even if you have both USB 1.1 and USB 2.0 devices on the same system.

  • While USB 2.0 devices operate on a USB 1.x port, their performance is significantly better when they are connected to a USB 2.0 port.

  • A USB 2.0 host controller has one high-speed Enhanced Host Controller Interface (EHCI) and one or more OpenHCI Host Controller Interface (OHCI) or Universal Host Controller Interface (UHCI) embedded controllers. Devices connected to a USB 2.0 port are dynamically assigned to either an EHCI or OHCI controller, depending on whether they support USB 2.0.

    Note - USB 2.0 storage devices that are connected to a port on a USB 2.0 PCI card, and that were used with a prior Solaris release in the same hardware configuration, can change device names after upgrading to this release. This change occurs because these devices are now seen as USB 2.0 devices and are taken over by the EHCI controller. The controller number, w in /dev/[r]dsk/cwtxdysz, is changed for these devices.

    Also note that the speed of a USB device is limited to what the parent port can support. For example, if a USB 2.0 external hub is followed by a USB 1.x hub and a USB 2.0 device downstream, devices that are connected to the USB 2.0 external hub run at full speed and not high speed.

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:

  • Cascading two bus-powered hubs is prohibited.

  • Each bus-powered hub is allowed a maximum of 100 mA only for each port.

  • Only self-powered or low bus-powered devices are allowed to connect to a bus-powered hub. High bus-powered devices are denied the connection. Some hubs or devices can report a false power source, such that the connection might be unpredictable.

USB Keyboards and Mouse Devices

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

  • Do not move the keyboard and mouse during a reboot or at the ok prompt on a SPARC system. You can move the keyboard and mouse to another hub at any time after a system reboot. After you plug in a keyboard and mouse, they are fully functional again.

  • The keys just to the left of the keypad might not function on some third-party USB keyboards.

  • SPARC – Keep the following issues in mind when using USB keyboards and mouse devices on SPARC systems:

    • The power key on a USB keyboard behaves differently than the power key on the Sun type 5 keyboard. On a USB keyboard, you can suspend or shut down the system by using the SUSPEND/SHUTDOWN key. However, you cannot use that key to power up the system.

    • Before the boot process finishes, the OpenBoot PROM (OBP) limits keyboard and mouse devices to the motherboard root hub ports only.

    • USB keyboard and mouse devices cannot be used simultaneously with Sun Type 3, 4, or 5 keyboards on legacy SPARC systems, such as the Ultra 80.

  • For information about multiple keyboard and mouse device support, see virtualkm(7D).

USB Wheel Mouse Support

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

  • Support for more than 3 buttons is available on USB or PS/2 mouse devices.

  • Wheel mouse scrolling is available on a USB or PS/2 mouse device. This support means that rolling the wheel on a USB or a PS/2 mouse results in a scroll in the application or window under mouse focus. StarOfficeTM, Firefox, and GNOME applications support wheel mouse scrolling. However, other applications might not support wheel mouse scrolling.

USB Host Controller and Hubs

A USB hub is responsible for the following:

  • Monitoring the insertion or removal of a device on its ports

  • Power managing individual devices on its ports

  • Controlling power to its ports

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:

  • Directing the USB bus. Individual devices cannot arbitrate for the bus.

  • Polling the devices by using a polling interval that is determined by the device. The device is assumed to have sufficient buffering to account for the time between the polls.

  • Sending data between the USB host controller and its attached devices. Peer-to-peer communication is not supported.

USB Hub Devices
  • Do not cascade hubs beyond four levels on either SPARC based systems or x86 based systems. On SPARC systems, the OpenBootTM PROM cannot reliably probe beyond four levels of devices.

  • Do not plug a bus-powered hub into another bus-powered hub in a cascading style. A bus-powered hub does not have its own power supply.

  • Do not connect a device that requires a large amount of power to a bus-powered hub. These devices might be denied connection to bus-powered hubs or might drain the hub of power for other devices. An example of such a device is a USB diskette device.

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:

  • Always use USB 2.0 compliant, fully rated (480 Mbit/sec) 20/28 AWG cables for connecting USB 2.0 devices.

  • The maximum cable length that is supported is 5 meters.

  • Do not use cable extenders. For best results, use a self-powered hub to extend cable length.

For more information, go to:

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  Published under the terms fo the Public Documentation License Version 1.01. Design by Interspire