On Mon, 30 Jan 2012, Klaus Rudolph wrote: > > > I really miss a simple beginners guide to the gadget framework where a > > > simple data flow diagram give answers to these beginners questions. > > > > > > I'm new to this list and also to the field of usb drivers. However i > > have these documents Seems it may help you, > > > > http://www.linux-usb.org/gadget/ > > http://www.linux-usb.org/gadget/h2-otg.htm You should also read include/linux/usb/gadget.h. There are lots of comments explaining the various fields and APIs. > Thanks for the link. I read the docs but could not find a answer to > my problem. > > My understanding is: > The function usb_ep_queue gives my the requests which my hardware > driver could deal with. But for ep0 I have no pending request and the > first non setup packet with 24 bytes of data could not be handled. If you have not received a request -- that is, if usb_ep_queue() was not called for ep0 -- then the hardware should reply with NAK when the 24-byte data packet is received. > The bulk data transfer seems to be quite simple. IN request data must > be send, OUT requests could be filled with "incoming" OUT data and > the callback ( complete) is called. Thats all!? Yes. > But for ep0 I have no understanding where incoming data > (OUT-Transfer) should be placed??? It's the same as for bulk transfers -- the UDC driver gets a request from usb_ep_queue() and it puts the data there. However there is one more complication when it comes to ep0. At the end of a control-IN transfer, the UDC will receive a data-OUT packet with 0 bytes (the status stage of the transfer). The hardware should reply with ACK and the driver should throw away the packet. > Maybe someone in the list can give me three sentences to that topic? Have you read Sections 8.4 and 8.5 in the USB-2.0 specification? Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
