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. The Mentor USB High Speed Dual Role Host Controller silicon IP (using the aforementioned musb_hdrc driver) is one example of such silicon. The "Multipoint" licensing option is basically for the TT support, as I understand it. One example of its use in a product is with TI's DaVinci chips. You can go to http://focus.ti.com/docs/prod/folders/print/tms320dm6446.html and download the USB controller docs. Ignore the nasty CPPI DMA glued onto it, and observe that there are host side TX and RX HUB registers that won't be present on designs that omit the "multipoint" support. (Which evidently include one of the Blackfin designs.) - Dave -- 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/
