On Sun, 15 Jan 2017, Vincent Pelletier wrote: > > An endpoint can not work in both directions, that's not how USB > > endpoints work at all. I think you are confusing the hardware with your > > configuration :) > > I do agree that I have never noticed in the wild a device using a > non-zero endpoint (4 LSb) in both directions (1 MSb) - and maybe there > is no host OS support anywhere. I have seen such devices mentioned in the mailing list. They work fine. > On the spec level though, I am less sure. Quoting the USB (v2) spec: ... The USB spec allows such things. > So there is either a bug in the HCI side, or in the UDC side: > - either the HCI should support bidirectional-ish endpoints (same > 4 LSb, different 1 MSb). Would this limitation be a hardware one ? I don't know about DWC. The host controllers drivers I maintain work okay when two endpoints have the same number but different directions. What sort of host controller do you test with? What does usbmon show? What happens when you run your test with dummy-hcd? > - or the UDC endpoint auto-allocation mechanism must skip an endpoint > when it is already used in the other direction This could be a bug in the UDC driver. 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
