> -----Original Message----- > From: [EMAIL PROTECTED] [mailto:linux-kernel- > [EMAIL PROTECTED] On Behalf Of Alan Stern > Sent: Thursday, January 03, 2008 2:29 AM > To: David Brownell > Cc: Mike Frysinger; [EMAIL PROTECTED]; linux-usb- > [EMAIL PROTECTED]; Robin Getz; linux-kernel@vger.kernel.org > Subject: Re: [linux-usb-devel] [PATCH] : Allow embedded developers USB > options normally reserved for OTG > > On Wed, 2 Jan 2008, David Brownell wrote: > > > On Wednesday 02 January 2008, Alan Stern wrote: > > > On Wed, 2 Jan 2008, Mike Frysinger wrote: > > > > > > > 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.) > > > > > > Just out of curiosity, how does a host controller manage to avoid > > > working with external hubs? > > > > The transaction translators in external high speed hubs require > > hosts to issue particular USB transactions. If the host controller > > doesn't implement the that split transaction support, then it won't > > be supporting external hubs. > > So in theory one could connect a high-speed hub to such a host > controller and expect it to communicate with high-speed devices. So > long as no full- or low-speed devices are added there wouldn't be any > split transactions. It wouldn't be USB-2.0 compliant but it should > still work.
Perhaps we could reject any low/full speed devices after the USBV enumeration phase itself. This would need perhaps a flag in the struct hc_driver which the hub code (that does the enumeration) can check and reject further enumeration? Atleast this way we can support high speed devices. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
