freebsd man page for ehci

EHCI(4) 						   BSD Kernel Interfaces Manual 						   EHCI(4)

NAME
     ehci -- USB Enhanced Host Controller driver

SYNOPSIS
     device ehci

DESCRIPTION
     The ehci driver provides support for the USB Enhanced Host Controller Interface, which is used by USB 2.0 controllers.

     EHCI controllers are peculiar in that they can only handle the USB 2.0 protocol.  This means that they normally have one or more companion
     controllers (i.e., ohci(4) or uhci(4)) handling USB 1.x devices.  Consequently each USB connector is electrically connected to two USB con-
     trollers.	The handling of this is totally automatic, but can be noticed since USB 1.x and USB 2.0 devices plugged in to the same connector
     appear to connect to different USB busses.

SEE ALSO
     ohci(4), uhci(4), usb(4), xhci(4)

HISTORY
     The ehci device driver first appeared in FreeBSD 5.1.

LOADER TUNABLES
     When the kernel has been compiled with options USB_DEBUG, some tunables become available that affect the behavior of ehci.  These tunables
     can be set at the loader(8) prompt before booting the kernel or stored in loader.conf(5).

     hw.usb.ehci.lostintrbug
	     This tunable enables the lost interrupt quirk.  The default value is 0 (off).

     hw.usb.ehci.iaadbug
	     This tunable enables the EHCI doorbell quirk.  The default value is 0 (off).

     hw.usb.ehci.no_hs
	     This tunable disables USB devices to attach like HIGH-speed ones and will force all attached devices to attach to the FULL- or LOW-
	     speed companion controller.  The default value is 0 (off).

BSD
								   March 4, 2012							       BSD