-If you're lucky, your hardware will support low-power modes for USB
-controllers while the system is asleep. Lots of hardware doesn't,
-however. Shutting off the power to a USB controller is equivalent to
-unplugging all the attached devices.
+Software suspend normally powers down USB controllers, which is equivalent
+to disconnecting all USB devices attached to your system.
+
+Your system might well support low-power modes for its USB controllers
+while the system is asleep, maintaining the connection, using true sleep
+modes like "suspend-to-RAM" or "standby". (Don't write "disk" to the
+/sys/power/state file; write "standby" or "mem".) We've not seen any
+hardware that can use these modes through software suspend, although in
+theory some systems might support "platform" or "firmware" modes that
+won't break the USB connections.