/share/man/man4/ehci.4

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  7.\" by Lennart Augustsson.
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 30.\" $FreeBSD$
 31.\"
 32.Dd March 4, 2012
 33.Dt EHCI 4
 34.Os
 35.Sh NAME
 36.Nm ehci
 37.Nd USB Enhanced Host Controller driver
 38.Sh SYNOPSIS
 39.Cd "device ehci"
 40.Sh DESCRIPTION
 41The
 42.Nm
 43driver provides support for the
 44.Tn USB
 45Enhanced Host Controller Interface,
 46which is used by
 47.Tn USB
 482.0 controllers.
 49.Pp
 50.Tn EHCI
 51controllers are peculiar in that they can only handle the
 52.Tn USB
 532.0 protocol.
 54This means that they normally have one or more companion controllers
 55(i.e.,
 56.Xr ohci 4
 57or
 58.Xr uhci 4 )
 59handling USB 1.x devices.
 60Consequently each
 61.Tn USB
 62connector is electrically connected to two
 63.Tn USB
 64controllers.
 65The handling of this is totally automatic,
 66but can be noticed since
 67.Tn USB
 681.x and
 69.Tn USB
 702.0 devices plugged in to the same
 71connector appear to connect to different USB busses.
 72.Sh SEE ALSO
 73.Xr xhci 4 ,
 74.Xr ohci 4 ,
 75.Xr uhci 4 ,
 76.Xr usb 4
 77.Sh HISTORY
 78The
 79.Nm
 80device driver first appeared in
 81.Fx 5.1 .
 82.Sh LOADER TUNABLES
 83When the kernel has been compiled with
 84.Cd options USB_DEBUG ,
 85some tunables become available that affect the behavior of
 86.Nm .
 87These tunables can be set at the
 88.Xr loader 8
 89prompt before booting the kernel or stored in
 90.Xr loader.conf 5 .
 91.Bl -tag -width "xxxxxx"
 92.It Va hw.usb.ehci.lostintrbug
 93This tunable enables the lost interrupt quirk.
 94The default value is 0 (off).
 95.It Va hw.usb.ehci.iaadbug
 96This tunable enables the EHCI doorbell quirk.
 97The default value is 0 (off).
 98.It Va hw.usb.ehci.no_hs
 99This 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.
100The default value is 0 (off).
101.El