NAME
ehci —
USB Enhanced Host Controller
driver
SYNOPSIS
device ehci
DESCRIPTION
Theehci 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
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).