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

     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).