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From: David Brownell <david-b@pacbell.net>
To: linux-usb-devel@lists.sourceforge.net
Subject: Re: [linux-usb-devel] [PATCH] : Allow embedded developers USB options normally reserved for OTG
Date: Wed, 2 Jan 2008 11:16:28 -0800
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Cc: "Mike Frysinger" <vapier.adi@gmail.com>, gregkh@suse.de,
       Robin Getz <rgetz@blackfin.uclinux.org>, linux-kernel@vger.kernel.org
References: <200801020948.51310.rgetz@blackfin.uclinux.org> <200801021047.16036.david-b@pacbell.net> <8bd0f97a0801021058g15d32de7nd29102ec552ba5fa@mail.gmail.com>
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On Wednesday 02 January 2008, Mike Frysinger wrote:
> > >
> > > Allow embedded developers to turn support for USB Hubs off even if they have a
> > > full root hub. This saves the overhead (RAM and Flash size).
> >
> > ISTR that it won't save very much code though ... the Linux USB
> > stack structures all its enumeration logic around hubs.
> 
> perhaps the code size is arguable as to whether it really matters.
> the reason we want it is that we have a USB host controller that will
> not work with USB hubs, so we want to make sure the system does not
> attempt such things. ?(yes, such a USB host controller is retarded,
> but the decision was out of our hands.)

Well, it won't work with *external* hubs.  Root hubs are a different
story.  :)

I think that's one of a class of decisions sometimes made by folk
who need to conserve silicon real estate.  Supporting external hubs
has always been optional for OTG systems.

- Dave


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