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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 con-
     trollers (i.e., ohci(4) or	uhci(4)) handling USB 1.x devices.  Conse-
     quently each USB connector	is electrically	connected to two USB con-
     trollers.	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 val-
	     ues 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	Ports 11.2		April 24, 2018		    FreeBSD Ports 11.2

NAME | SYNOPSIS | DESCRIPTION | LOADER TUNABLES | SYSCTL VARIABLES | SEE ALSO | HISTORY

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