linux-kernel - Re: PROBLEM: USB keyboards works only 4 per PC host port

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Date:	Tue, 19 Aug 2008 16:04:44 -0400 (EDT)
From:	Alan Stern <stern@...land.harvard.edu>
To:	David Brownell <david-b@...bell.net>
cc:	juanslayton@...extreme.com, Aivils Stoss <aivils@...net.lv>,
	<jkosina@...e.cz>, lud <linux-usb@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>,
	Randy Dunlap <rdunlap@...otime.net>,
	<linuxconsole-dev@...ts.sourceforge.net>,
	<linux-input@...r.kernel.org>
Subject: Re: PROBLEM: USB keyboards works only 4 per PC host port

On Tue, 19 Aug 2008, David Brownell wrote:

> The OHCI scheduling is pretty simple and compact.  I'd think it would
> be easy enough to make UHCI do the same sort of thing:  track bandwidth
> assigned to 2^N frames (OHCI hardware imposes a smaller limit for N
> than UHCI hardware does), and pick the least loaded of those frames to
> use for new transfers.  In ohci-q.c see balance(), periodic_{,un}link().
> 
> Thing is that would involve changing how UHCI manages periodic transfers;
> assuming it hasn't changed those structures since last I looked.

Yes.  That's the messy part; the scheduling itself is easy.

Alan Stern

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