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

From: Alan Stern <stern@rowland.harvard.edu>
To: David Brownell <david-b@pacbell.net>
Cc: juanslayton@dslextreme.com, Aivils Stoss <aivils@latnet.lv>,
	<jkosina@suse.cz>, lud <linux-usb@vger.kernel.org>,
	<linux-kernel@vger.kernel.org>,
	Randy Dunlap <rdunlap@xenotime.net>,
	<linuxconsole-dev@lists.sourceforge.net>,
	<linux-input@vger.kernel.org>
Subject: Re: PROBLEM: USB keyboards works only 4 per PC host port
Date: Tue, 19 Aug 2008 16:04:44 -0400 (EDT)	[thread overview]
Message-ID: <Pine.LNX.4.44L0.0808191603350.3391-100000@iolanthe.rowland.org> (raw)
In-Reply-To: <681431.40736.qm@web82201.mail.mud.yahoo.com>

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