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 buses.

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).

SYSCTL VARIABLES

     The following variables are available as both sysctl(8) variables and loader(8) tunables:

     hw.usb.ehci.debug
             Debug output level, where 0 is debugging disabled and larger values increase debug message
             verbosity.  Default is 0.

SEE ALSO

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

HISTORY

     The ehci device driver first appeared in FreeBSD 5.1.