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EHCI(4)               DragonFly 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
     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).

DragonFly 3.7                   March 13, 2014                   DragonFly 3.7

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