About USB in the Solaris Environment

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

USB Keyboards and Mouse Devices

Only Sun USB keyboards and mouse devices are supported. System configurations with multiple USB keyboards and mouse devices might work, but are not supported in the Solaris environment. See the following items for details.

• A USB keyboard and mouse can be connected anywhere on the bus and can be configured as the console keyboard and mouse. Booting the system is slower if the keyboard and mouse are not on the root hub.

• Do not move the console keyboard and mouse during a reboot or at the ok prompt.You can move the console 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.

• SPARC – 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, but you cannot use that key to power up the system.

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

• Multiple keyboards are not supported:

  • Multiple keyboards enumerate and are usable, but they are not plumbed as console keyboards.

  • The first keyboard that is probed at boot time becomes the console keyboard. The result of this probing might cause confusion if multiple keyboards are plugged in at boot time.

  • If you unplug the console keyboard, the next available USB keyboard does not become the console keyboard. The next hot-plugged keyboard becomes the console keyboard.

• Multiple mouse devices are not supported:

  • Multiple mouse devices enumerate and are usable, but they are not plumbed as console mouse devices.

  • The first mouse that is probed at boot time becomes the console mouse. The result of this probing might cause confusion if you have multiple mouse devices plugged in at boot time.

  • If you unplug the console mouse, the next available USB mouse does not become the console mouse. The next hot-plugged mouse becomes the console mouse.

• If you have a third-party composite keyboard with a PS/2 mouse, and the composite keyboard/mouse is the first one to be probed, it becomes the console keyboard/mouse even if the PS/2 mouse is not plugged in. Thus, another USB mouse plugged into the system cannot work because it is not configured as the console mouse.

• Only two-button and three-button mouse devices are supported. A wheel-on-wheel mouse acts like a plain-button mouse. A mouse with more than three buttons functions like a three–button mouse.

USB Host Controller and Root Hub

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 or x86 based systems. On SPARC systems, the OpenBoot^TM 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 not work well on 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 are 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.

If the SPARC based system has power management enabled, the USB framework makes a best effort to power-manage all devices. 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 (keyboard, mouse, speakers, microphones), hub, 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.

When power management is running to reduce power consumption, USB leaf devices are powered down first. When all devices that are connected to this 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.

Guidelines for USB Cables

Keep the following guidelines in mind when connecting USB cables:

• Always use USB 1.0 compliant, fully rated (12 Mbit/sec) 20/28 AWG cables for connecting USB devices. Use bus-powered hubs for low-speed devices only. Always use fully rated (12 Mbit/sec) 20/28 AWG cables for connecting USB devices.

• 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 http://www.usb.org/channel/training/warning.