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 controllers.  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

       xhci(4), ohci(4), uhci(4), usb(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).

Debian                                          February 24, 2011                                        EHCI(4)