On Wed, May 13, 2020 at 07:07:20PM +0200, Andrey Konovalov wrote: > Hi Alan, > > I've been looking at this a little more. Do I understand correctly > that even though Dummy UDC names endpoints as "ep1in", etc. it > actually allows to assign endpoints addresses different from what is > specified in the endpoint names (it uses find_endpoint() to find the > right endpoint based on ep->desc)? E.g. you can technically assign > endpoint with address 2 (| USB_DIR_IN) to "ep1in". Yes, that's right. In fact, you can do this with any UDC. (But with other UDCs it won't work, whereas with dummy-hcd it will.) > If this is correct, this kind of limits Dummy UDC usage with Raw > Gadget the way it is currently implemented, as Raw Gadget assumes that > the endpoint address must be fixed when the endpoint is named as > ep1in. Okay. That makes sense, since it is true for most UDCs. > Would it be acceptable to add another mode to Dummy UDC that names the > endpoints as "ep-a"? Perhaps enabled with a module parameter. I'm not > sure if this kind of naming would be technically correct, as "ep-a" > name assumes that we can assign arbitrary transfer type to the > endpoint as well, which isn't possible with Dummy UDC, as it doesn't > support ISO transfers. > > Or do you think there can be another way to expose the fact that Dummy > UDC allows arbitrary addresses? I could hardcode this into Raw Gadget, > but it doesn't feel like the right approach. Why do you want to do this? Does anything go wrong if you just continue to assume the endpoint numbers are fixed? I suppose, if you thought this was really necessary, we could change find_endpoint() so that it looks for a match against the endpoint's name instead of against the address stored in the descriptor. Or we could change the last thirteen "generic" endpoints in ep_info[] to be configurable: "ep-a", ..., "ep-m", or "ep-aout", ..., "ep-min". (The fact that the endpoints don't support isochronous is exposed through the usb_ep_caps structures.) Alan Stern
