linux-kernel - Re: pl2303 - pl2303_open - failed submitting interrupt urb, error -28

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Date:	Fri, 5 Dec 2008 11:03:41 -0500 (EST)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Marc Haber <mh+linux-kernel@...schlus.de>
cc:	Greg KH <greg@...ah.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	<linux-kernel@...r.kernel.org>, <linux-usb@...r.kernel.org>
Subject: Re: pl2303 - pl2303_open - failed submitting interrupt urb, error
 -28

On Fri, 5 Dec 2008, Marc Haber wrote:

> On Wed, Dec 03, 2008 at 07:47:25AM -0800, Greg KH wrote:
> > I would suggest using a USB 1.1 hub instead if you have to use this kind
> > of hardware set up.
> 
> It is nearly impossible to buy that kind of hardware at the current
> time.
> 
> >   I think the core is just not able to schedule so many interrupt urbs
> >   with such a setup, running USB 1.1 devices behind a USB 2.0 hub like
> >   this is a very difficult thing to do.
> > 
> > Sorry I don't have a better solution.
> 
> Is it possible to disable USB 2.0 for selected links?

Yes it is.  You can force port P of the EHCI controller on bus B to run 
at low/full speed by doing:

	echo P >/sys/class/usb_host/usb_hostB/companion

To allow port P to run at high speed again, use the same command but 
write -P instead of P.

Alan Stern

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