EHCI(4) FreeBSD 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 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.
FreeBSD 15.1-STABLE-HBSD April 24, 2018 EHCI(4)